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The development of a technique for the determination of disolved chromium(III) and total dissolved chromium… Mugo, Robert K. 1991

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THE DEVELOPMENT OF A TECHNIQUE DISSOLVED CHROMIUM(III) AND  FOR THE DETERMINATION  TOTAL DISSOLVED CHROMIUM IN  SEAWATER BY ELECTRON CAPTURE DETECTION GAS  CHROMATOGRAPHY  by ROBERT K. MUGO B.Sc.  (Hons.)# U n i v e r s i t y  A THESIS SUBMITTED  of Nairobi,  1987  I N P A R T I A L FULFILLMENT  OF THE REQUIREMENTS FOR THE DEGREE  OF  MASTER OF SCIENCE  in THE FACULTY OF GRADUATE STUDIES (Department o f C h e m i s t r y ) We  accept t h i s to  thesis  the required  as conforming standard  THE UNIVERSITY OF B R I T I S H COLUMBIA October ©  OF  1991  R o b e r t K. Mugo, 1991  In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department  or  by his  or  her  representatives.  It is  understood  that  copying or  publication of this thesis for financial gain shall not be allowed without my written permission.  Department of  CU  The University of British Columbia Vancouver, Canada Date  DE-6 (2/88)  OcWr tfc 1991 •  ABSTRACT A  gas chromatographic  dissolved  Cr(III)  developed.  The  detection  of  derivative solvent was  and  total  determination samples  for  reduction,  (Htfa)  difference The  which  3  stored  of t o t a l  total  seawater  prepared  sample.  (with  of  samples  Cr(VI)  Cr(III)  for  of  the  unacidified and,  Research  C o u n c i l o f Canada.  obtained  as  the  was  assessed  by  the  reference  materials  from  The C r v a l u e s  the National  obtained  r e f e r e n c e m a t e r i a l s u s i n g t h i s method were i n good with the c e r t i f i e d 1.3% a t 4.67  respectively. determination  detection limits  The method o f Cr  attempt  to thermal 3  nM w i t h  The t e c h n i q u e  i s designed  i n seawater  to  extend  (3 a _ ) n  agreement  ±  f o r Cr(III) seawater,  t o be a p p l i e d t o t h e  samples  the  f o r the  has a p r e c i s i o n o f  immediately  onboard s h i p d u r i n g oceanographic  determination  Ga(tfa)  values.  C r o f 0.186 a n d 0.243 nM i n t h e o r i g i n a l  The  after  being  technique  of standard  collection  the  of these two). accuracy  total  from  The method  C r and t o s t o r e d , f r o z e n ,  determination Cr  was  acidified  analysis  and  was  1,1,1-trifluoro-2,4-pentanedione Cr(tfa) ,  the  i n seawater  capture  to  the  Cr  of  electron  Cr(III),  uses  e x t r a c t i o n o f a 15-mL  applied  f o r the determination  dissolved  technique  the  of  method  after  cruises.  technique  to  the  o f g a l l i u m i n s e a w a t e r was n o t s u c c e s s f u l due  instability  chelate.  and/or i n s u f f i c i e n t v o l a t i l i t y  of the  iii TABLE OF  CONTENTS Page  ABSTRACT  i i  TABLE OF CONTENTS  i i i  L I S T OF TABLES  viii  L I S T OF FIGURES  ix  L I S T OF ABBREVIATIONS  xi  ACKNOWLEDGMENT  CHAPTER 1:  x i i  INTRODUCTION  1.1  BACKGROUND  1  1.2  COMPOUND REQUIREMENTS  2  1.2.1  Volatility  2  1.2.2  Stability  3  1.2.3  Ease o f f o r m a t i o n  4  1.3  B-DIKETONE CHELATES  5  1.4  FLUORINATED 6-DIKETONE CHELATES  8  1.5  ELECTRON CAPTURE DETECTOR  9  1.6  DETERMINATION OF TRACE METALS BY GAS CHROMATOGRAPHY  12  1.7  THE DETERMINATION OF CHROMIUM IN SEAWATER  16  1.8  MARINE GEOCHEMISTRY  19  1.9  AIM OF PRESENT STUDY  CHAPTER 2: 2.1  OF CHROMIUM  23  EXPERIMENTAL  INSTRUMENTATION  26  2.1.1  26  Gas c h r o m a t o g r a p h  iv  2.2  2.1.2  Mass s p e c t r o m e t r y  27  2.1.3  Elemental  27  2.1.4  pH  27  2.1.5  Shaking  27  2.1.6  Heating  27  analysis  MATERIALS AND REAGENTS  28  2.2.1  l,1,1-Trifluoro-2,4-pentanedione  28  2.2.2  Toluene  28  2.2.3  Buffer  29  2.2.4  Sodium s u l p h i t e  30  2.2.5  2,6-Dichlorobiphenyl  30  2.2.6  Separatory  31  2.2.7  D e i o n i z e d water  31  2.2.8  Aqueous C r s t a n d a r d s  31  2.2.9  funnel  Tris-(1,1,1-trifluoro-2,4-pentanediono)chromiura(III) s t a n d a r d  32  2.3  PROCESSING  32  2.4  OPTIMIZATION  33  2.4.1  Gas C h r o m a t o g r a p h y  33  2.4.2  Solvent extraction conditions  34  2.4.2.1  pH  34  2.4.2.2  Ligand  2.4.2.3  T e m p e r a t u r e and r e a c t i o n t i m e  2.5  2.6  concentration  SEAWATER SAMPLES  35 35  2.5.1  Stored  acidified  2.5.2  Frozen  unacidified  ANALYTICAL SCHEME  35  seawater samples seawater samples  36 36 37  V  2.7  GENERAL  2.8  QUANTITATION  2.9  PROCEDURE  37 39  2.8.1  Organic  chromium s t a n d a r d s  2.8.2  Chromium e x t r a c t i o n  40  standards  2.8.2.1  Cr(III)  2.8.2.2  Cr(VI) standards  40  standards  40 41  CHROMIUM RECOVERY STUDIES  41  2.10 REPRODUCIBILITY  41  2.11 ACCURACY  41  2.12 BLANKS  42  CHAPTER 3.1  3:  RESULTS AND  DISCUSSIONS  CHARACTERIZATION OF T R I S - ( 1 , 1 , l - T R I F L U O R O - 2 , 4 PENTANEDIONO)-CHROMIUM(III) STANDARD  43  3.1.1  Mass s p e c t r a  43  3.1.2  Elemental  44  analysis  3.2  QUANTITATIVE ANALYSIS IN GC  46  3.3  QUANTITATIVE PROCEDURES IN PRESENT STUDY  47  3.3.1  Cr(tfa)  47  3.3.2  Internal  3.3.3  O r g a n i c chromium s t a n d a r d s  3.3.4  Chromium e x t r a c t i o n  3.3.5  Chromium e x t r a c t i o n b l a n k s  50  3.3.6  C a l i b r a t i o n curves  51  3.3.7  Chromatograms  51  AGENT  3  c i s v trans  isomerization  s t a n d a r d method  standards  48 ,  49 50  3.4  REDUCING  57  3.5  SOLVENT  57  3.6  OPTIMIZATION  58  vi  3.6.1  3.6.2  3.7  3.8  Gas c h r o m a t o g r a p h  58  3.6.1.1  59  ECD s e n s i t i v i t y  Solvent  extraction  3.6.2.1  pH  3.6.2.2  Ligand  3.6.2.3  T e m p e r a t u r e and r e a c t i o n t i m e  60 concentration  60 62  ANALYTICAL FIGURES OF MERIT  65  3.7.1  Precision  65  3.7.2  Recovery  66  3.7.3  Accuracy  67  3.7.4  Limit of detection  68  ANALYSIS OF SEAWATER SAMPLES  69  3.8.1  Stored  acidified  69  3.8.2  Stored  f r o z e n samples  3.8.2.1 3.8.3 3.9  60  samples  Handling  R e a g e n t and h a n d l i n g  DETERMINATIONS  72 75 blank  AT SEA  76 76  3.10 SUGGESTIONS  FOR FURTHER WORK  77  3.11 SUMMARY AND  CONCLUSIONS  78  CHAPTER 4.1  4.2  4:  GALLIUM  INTRODUCTION  79  4.1.1  Overview  79  4.1.2  Background  79  EXPERIMENTAL  81  4.2.1  Gas c h r o m a t o g r a p h y  81  4.2.1.1  81  Column  vii  4.2.1.2 4.2.2  4.3  GC c o n d i t i o n s  81  Synthesis of tris-(1,1,1-trifluoro-2,4pentanediono)-gallium(III) standard  82  4.2.3  Organic  Ga s t a n d a r d s  82  4.2.4  Solvent  extraction  83  RESULTS AND 4.3.1  DISCUSSION  84  Characterization of t r i s - ( 1 , 1 , 1 - t r i f l u o r o 2,4-pentanediono)-gallium(III)  standard  ....  84  4.3.1.1  Mass s p e c t r a  84  4.3.1.2  Elemental  86  analysis  4.3.2  Chromatograms  86  4.3.3  ECD s e n s i t i v i t y  90  4.3.4  Discussion  91  4.3.5  Summary and c o n c l u s i o n s  95  REFERENCES  96  APPENDIX I.  Theoretical intensity patterns f o r Cr(tfa) and C r ( t f a ) *  100  Theoretical intensity patterns f o r Ga(tfa) and G a ( t f a )  101  +  3  II.  2  +  3  2  viii L I S T OF TABLES  1.5 3.1.1 3.1.2 3.6.1  3.7.1  ECD s e n s i t i v i t y o f compounds  to various  classes 13  Fragmentation ions of t r i s - ( 1 , 1 , 1 - t r i f l u o r o 2,4-pentanediono)-chromium(III)  43  Elemental a n a l y s i s data f o r t r i s - ( 1 , 1 , 1 trifluoro-2,4-pentanediono)-chromium(III)  44  Gas c h r o m a t o g r a p h i c c o n d i t i o n s f o r t h e a n a l y s i s o f chromium a s t r i s - ( 1 , 1 , 1 - t r i f l u o r o - 2 , 4 pentanediono)-chromium(III)  58  Reproducibility  o f C r d e t e r m i n a t i o n on  seawater  sample  3.7.2  Recovery  o f Cr s p i k e s from seawater  3.7.3  A c c u r a c y o f C r d e t e r m i n a t i o n on s e a w a t e r samples T o t a l Cr v s . depth i n the c e n t r a l North A t l a n t i c (BDA s t a t i o n )  3.8.1 3.8.2 4.2.1.2  4.3.1.1 4.3.1.2  66 samples  ...  67  68 70  C r ( I I I ) , C r ( V I ) a n d t o t a l C r vs. d e p t h i n t h e N o r t h e a s t P a c i f i c (NTK s t a t i o n )  74  Gas c h r o m a t o g r a p h i c c o n d i t i o n s f o r t h e a n a l y s i s o f g a l l i u m as t r i s - ( 1 , 1 , 1 - t r i f l u o r o 2,4-pentanediono)-gallium(III)  81  Fragmentation ions o f t r i s - ( 1 , 1 , 1 - t r i f l u o r o 2,4-pentanediono)-gallium(III)  84  Elemental a n a l y s i s data f o r t r i s - ( 1 , 1 , 1 trifluoro-2,4-pentanediono)-gallium(III)  86  ix L I S T OF  FIGURES  Figure  Page  1.3  S t r u c t u r e s o f some B - d i k e t o n e  1.5  E l e c t r o n capture  1.8  pH-pE d i a g r a m f o r t h e m a j o r d i s s o l v e d s p e c i e s o f chromium  3.1.1  ligands  detector  11  Organic  3.3.6b  Cr(III) calibration  3.3.6c  T o t a l Cr c a l i b r a t i o n curve obtained from r e d u c i n g C r ( V I ) standards Chromatogram o f s y n t h e s i z e d C r ( t f a ) standard  3.3.7c  Cr standards  calibration  45  3.3.6a  3.3.7b  22  Mass s p e c t r u m o f t r i s - ( 1 , 1 , 1 - t r i f l u o r o 2,4-pentanediono)-chromium(III)  3.3.7a  7  curve  curve  Chromatogram o f C r ( t f a ) standard Chromatogram o f C r ( t f a )  3  52 53  53 3  54  f r o m an e x t r a c t i o n 55  3  from a seawater  sample  56  3.6.2.1  C r r e c o v e r y v s . pH  61  3.6.2.2  C r r e c o v e r y vs.  61  H t f a l i g a n d volume  3.6.2.3a C r r e c o v e r y vs. s h a k i n g temperature 3.6.2.3b C r r e c o v e r y vs. s h a k i n g microwave i r r a d i a t i o n 3.8.1  3.8.2 4.3.1.1  time  a t room  time  after  64  T o t a l C r vs. d e p t h i n t h e c e n t r a l A t l a n t i c (BDA s t a t i o n )  64 North 71  C r ( I I I ) , C r ( V I ) and t o t a l C r vs. d e p t h i n t h e N o r t h e a s t P a c i f i c (NTK s t a t i o n )  73  Mass s p e c t r u m o f t r i s - ( 1 , 1 , 1 - t r i f l u o r o 2,4-pentanediono)-gallium(III)  85  X  4.3.2a  4.3.2b  4.3.2c  5.10(a)  Chromatogram of standard  synthesized  Chromatogram of standard  Ga(tfa)  Chromatogram of sample  Ga(tfa)  Ga(tfa)  87 3  from  3  from  Theoretical intensity for C r ( t f a )  patterns  Theoretical intensity for C r ( t f a )  patterns  Theoretical intensity for G a ( t f a )  patterns  Theoretical intensity for G a ( t f a )  patterns  101  +  3  +  seawater  100  +  2  a  100  2  5.20(b)  extraction  89  +  5.20(a)  an  88  3  5.10(b)  3  101  xi  L I S T OF ABBREVIATIONS  DI H 0 2  Htfa/tfa  Deionized  water  1,1,1-Trifluoro-2,4-pentanedione (Trifluoroacetylacetone)  GC  Gas  ECD  Electron  hfa fod  chromatography capture  detector  Hexafluoroacetylacetone  acac  6,6,7,7,8,8,8-Heptafluoro-2,2dimethyl-3,5-octanedione Acetylacetone  thd  2,2,6,6-Tetramethyl-3,5heptanedione  facam  Trifluoroacetyl-d-camphor  ppm  Parts per m i l l i o n  ppb  Parts per b i l l i o n  nM  Nanomolar  pM  Picomolar  UHP  Ultra  high  purity  NaAc  Sodium  acetate  HAc  Acetic  acid  PFA  Perfluoroalkoxy  xii  ACKNOWLEDGMENT  I  wish  supervisor, throughout people  to  express  my  D r . K. J . O r i a n s , the course  of this  i n and o u t s i d e  encouragement  and h e l p f u l  gratitude  to  my  f o r h e r guidance study.  I am a l s o  t h e Department  who  and support grateful to  have  suggestions a l l along.  research  given  me  1 CHAPTER 1  INTRODUCTION  1.1  BACKGROUND The  as  use  metal  (1).  of  gas  chelates  This  chromatography  was  concept  first  i n analyzing  suggested  requires  that  a  by  then  be  subjected  measurement. suitable  The  was  rapidly  of g r e a t use Gas in  gas and  i t was  f o r metal  reasoned  for analyzing  has By  simply  column  stationary  phase,  the  quality  markedly.  Peak r e s o l u t i o n  possible  to  take  characteristics  of  advantage of  that  can and  in finding If  the  mixtures  to  or  technique of  separate a t low  this  metals. complex  levels  are  can  changing  selected  one  of  the  or  the  of  the  can  be  improved  be  enhanced  the  analysis  data  and  liquid  changes.  GC-detectors of  not e v i d e n t  temperature  t i m e s h o r t e n e d by s i m p l e p a r a m e t e r variety  separation  a great v e r s a t i l i t y  as  wide  metals  1955  analysis.  such  The  in  purpose.  to provide detection  techniques.  parameters,  this  chromatography  chromatography  other  for  metals  compounds w h i c h  chromatographic  compounds  overcome,  of  of  t h e b i g g e s t o b s t a c l e was  of great b e n e f i t  ability  mixtures  gas  Initially,  volatile  difficulty w o u l d be  to  Lederer  mixture  m e t a l compounds be c o n v e r t e d t o v o l a t i l e  for  available  specificity detection  i n the  makes i t response  techniques.  The  2  electron  capture  sensitive  to  detector,  halogenated  for  example,  compounds,  is  yet  remarkably-  insensitive  to  hydrocarbons. The  ability  techniques, difficult  such  t o combine as s o l v e n t  problems  of  gas chromatography extraction,  separations  feature f o r a n a l y s i s o f metals two  components  often  one  of  preliminary the  cannot the  sample  several  be  components  i n a variety  may  by be  preparation step  parameters  to solve  i s also  separated  with  an  especially attractive  of matrices.  gas  removed  of  If  chromatography, during  by v a r y i n g  (pH, a d d i t i o n  other  the  any one o f  masking  agents,  etc.) associated with the extraction.  1.2  COMPOUND REQUIREMENTS If  trace  gas chromatography  metal  analysis,  i s t o be s u c c e s s f u l l y  the metal  derivative  applied to  formed  has t o  requirement  i s that  meet a number o f r e q u i r e m e n t s .  1.2.1  Volatility The  most  important  and r e s t r i c t i n g  compounds s h o u l d be v o l a t i l e the  gas phase.  exhibit  a vapor  move t h r o u g h few  types  F o r most  purposes,  pressure  o f 0.1  t h e column of  enough t o be c h r o m a t o g r a p h e d  metal  the metal  t o 1.0  a t a reasonable compounds  meet  mm  compound  Hg  rate this  in must  i n order t o (2) .  Only  a  requirement.  3  Immediately polar  eliminated  a r e most  s p e c i e s i n which  types  intermolecular  of  formation,  p o l y m e r i z a t i o n and h y d r o g e n  volatility.  volatile  at  number.  They  include  carbonyls,  metal  complexes  various metal  low  such  as  dipoles,  are  halides, metal  the metal  act to  that are  limited  metal  The  adduct  will  compounds  temperatures  alkyls,  are high.  bonding  of metal  some m e t a l  metal  large  or highly  in  alkoxides,  hydrides,  jr-bonded  cyclopentadienyls,  and  c h e l a t e s s u c h a s B - d i k e t o n a t e s and p o r p h y r i n s .  Stability The  importance  strongly  dependent  compounds  c a n be  the  as  The t y p e s  reasonably  metal  1.2.2  such  forces  existence  reduce  factors  of charged  result  demanding. sufficiently  that  of on  the  of  i t s volatility.  eluted  a t lower  thermal  stability  For quantitative thermally  stability  work,  stable  column  a  compound  More  they  with  a r e n o t as  t h e compounds  that  volatile  temperatures  requirements  is  can  s h o u l d be be  eluted  without degradation. In must  addition  t o being  be s o l v o l y t i c a l l y  stationary  phase  effectively  occur.  T h e compounds  of  stationary  the  stable  when  i n t h e column.  compete  solid  thermally stable, dissolved  i n the  I f the l i q u i d  as a c o o r d i n a t i n g should also  t h e compounds  agent  flow  phase can  solvolysis  will  be n o n - r e a c t i v e w i t h t h e  s u p p o r t and w i t h t h e c o n s t r u c t i o n  chromatographic  liquid  system.  From  a  materials practical  4  standpoint, the  i t i s d e s i r a b l e t h a t the  ambient  atmosphere  so  as  compounds be  to  avoid  stable in  special  handling  procedures. Unlike ways  the  of  thermal  circumventing  requirements.  materials  phases,  will  solid  the of  as t h e m e t a l  other  and  not  undergo may  present  in  present  a  occur  a  in  i f oxidizing  For  and  reducing  Dimerization  bridge  formation  saturated  or  and  do  may  Ease of  limited or  chlorothat  are  moieties  that  Formation  q u a n t i t a t i v e work t h e  quantitative  oxo-,  contain  1.2.3  are  redox  polymerization  Compounds  not  sample  are  form b r i d g e s are t h e r e f o r e p r e f e r r e d .  For  the  species  when h y d r o x o - ,  occurs.  with.  example,  readily  used  operation.  components o f  reaction.  particularly  coordinatively  be  construction  stability  t h a t the  problem  other  liquid  h a l i d e s which undergo h y d r o l y s i s  mutual  mixture.  are  stability  non-reactive  supports  greater  i s a l s o important  reactions  or  of  there  a t m o s p h e r e a r e , however, burdensome t o work  It should  requirement,  selection  permit  Compounds s u c h the  some  Careful  partitioning  in  stability  to  those  types  of  t h a t can  compounds w h i c h be  n e a r l y q u a n t i t a t i v e and  yield.  The  metal  formed  only  yield.  T h e i r syntheses  with  carbonyls, hydrides difficulty  and  c a n n o t be  readily  easily  and  alkyls  rarely  in  c a r r i e d out  formed  can in  reproducible are u s u a l l y quantitative  i n water  owing  5  to  the s o l v o l y t i c  hand,  certain  solvolytic The  i n s t a b i l i t y of the products.  chelating  agents  form  On  the other  complexes  of  s t a b i l i t y by s i m p l e r e a c t i o n s t h a t o c c u r  reactions  can  be  carried  m e d i a and a r e pH d e p e n d e n t , selectivity  in  handling  out  i n aqueous  or  a feature affording  mixtures  which  are  high  readily.  non-aqueous a measure o f  difficult  to  separate chromatographically.  1.3  B-DIKETONE CHELATES ft-diketonates  are  derivatives  which  quantitative  gas  are  stable  form complexes  meet  of  the  the  are r e a d i l y  i n the under  classes  These  of  for  successful  chelates  have  atmosphere.  c o n d i t i o n s which  multi-element determinations. well  advantages matrices  The  solvent  in selectivity.  can  complexes  to  be  simplifies  into  ligands  forces  surrounding  with  volatility should  extraction  with  act  i t  volatile  the to  shield  that a  the  render  hydrocarbon  combination minimize  ions the  aspect i n  Metal B-diketonates also  lend  i t s attendant  metal  B-diketonate  f o r g a s c h r o m a t o g r a p h i c s e p a r a t i o n and  intermolecular  yield  A w i d e v a r i e t y o f m e t a l s i n many  converted  B-diketone  been  Many m e t a l  sample p r e p a r a t i o n p r o c e d u r e and c o u l d be a u s e f u l  themselves  metal  obtained i n quantitative  ambient  similar  few  requirements  chromatography.  used e x t e n s i v e l y , and  one  of  the  steric tendency  metal i t  ion  from  the  non-volatile  by  shell. and to  analysis.  For  inductive form  maximum effects  adducts  or  6  polymers. the  The  presence  resulting  virtually With  enhanced  essential  their  virtually  of chelate rings stability  have  for successful  i n the been  described  o x y g e n d o n o r atoms f a c i l i t a t i n g c o m p l e x a t i o n  with  elements,  the  i o n i z a t i o n of 6-diketones  R-C-CH.-C-R'  8-diketonates  i s as  follows:  R-C-CH = C-R'  (a) complexing  neutral twice  (1)  enolate  oxidation  coordinatively solvent  (b)  chelates with  their  or  anion  (b) whose  state.  The  other  ligarid  species  and  have  Cr(III),  chromatographed  as  as N i ( I I ) ,  Co(II),  additional  neutral  than  hydrates volatility peak  many  instances  forms  c o o r d i n a t i o n number resulting  complexes  been  F e ( I I ) and ligands  to  subject  have  been  broadening,  characteristics.  of Be(II),  GC  the  assume  analysis  the  a  Alternatively,  by are  Al;'"".';,  successfully metals  such  adduct  coordination state state,  (4).  polarity, or  which  which r e a d i l y  Hydrates  tailing  most  In c o n t r a s t ,  oxidation  formed.  increase  those  La(III),  to  their to  Chelates  amongst  B-diketonates.  twice  and  as  (3).  is are  saturated, thus p r e c l u d i n g other adduction  s a t u r a t e d , such  difficult  in  metals  coordinatively  greater  (Fig.  agents.  I A "' J A-  The  as  (2).  1.3.1) a r e amongst t h e most v e r s a t i l e c h e l a t i n g The  and  chromatography  a l l A-type  gas  complex  tend  have In to  thereby other  proved  some lower  cases the  increasing undesirable  n o n - s o l v a t e d c h e l a t e s have  7  Liqond acetytacetone  Structure of Anion  Abbreviation  H£-£Vc-CH,  ocac  H  trifluoroacetylacetone  hexafkioroocetylacetone  FjC-?-C-?-CH H  tfa 3  0© F,C-C-9  hfa  H 2,2,6,6-tetramethyl-3,5-  HjC-6-C-C-CHf-CH, H£ H CHs  thd  hepianedione  6^,7,7,8 8,8-h€ptofluoro-2,2-  HaC-C-C-C-C-CFrCFj-CF,  fod  L  dimefhyl-3,5-octanedione  l^!A5,6,6,7,7,7-decafluofO-  2,4-heptonedione  FsC-C-C-C-CFV-CFfCF, H  facam  tri f luoroacetyl-d-camphor  Fig.  1.3:  Structure  dfhd  o f some 6 - D i k e t o n e  ligands  8  polymerized other  or  groups  phase.  on  the  leads  to  excessive  irreversible  levels  FLUORINATED With only  They  and  (approx.  pointed  °C)  chelates of  a  made  fluorinated  analogs  reduce  the  on-column and  of van  GC  GC  metal  der  complex Waals  much  less  the  port,  part as  The  f o r c e s and  Cr(III)  As  by  was  the  major  of  metal  introduction fluorinated  severe  increased  in  be  characteristics,  (2),  was  to  high  to  and  These  their  (6).  too  determination  injection  atoms  are  degradation.  procedure  explained  fluorine  the  of  that  Sievers  require  column,  be  electronegative  even  chromatography.  Al(III)  adequate  the  because may  low  degradation  B-diketonates.  (lower  effect  periphery  or  Moshier  that  temperatures),  or  acetylacetonates  during  Be(II),  showed  useful analytical  conditions  This  (5)  by  acetylacetonate  at  simple  thermal  Only  injection  breakthrough  broadening  temperatures  for  absent.  out  the  instability  column  170-200  minimal  stationary  u n s a t i s f a c t o r y f o r m e t a l a n a l y s i s owing  acetylacetonates with  peak  i n the  or  CHELATES  exceptions,  require  completely  and  particularly  fl-DIKETONE  solvolytic  often  active, hydroxyl  (4).  a few  have p r o v e n t o be  with  supports  adsorption,  concentration  thermal  on-column  present  This  1.4  reacted  instrument  and  detector  volatilities.  envisioning  dominating  the  fluorocarbon intermolecular  shell  the outer may  hydrogen  9  bonding  between  Conceivably prevent  the  somewhat  close-packing  should  favour  The  increase  several  containing  metal  with  »  »  the  1.5  of  CAPTURE  chromatographic utilized  the  conductivity electron  concentrations  Workers which  limits  have i s  detector.  of  also  and  the  of  to  on  containing of  fluorine  vapor  pressure  that  complexes  more v o l a t i l e i n the  than  order  (8)  determine  hfa  applied  the  relative  B-diketonates  and  confirmed  the  fluorination.  extent  have  trace flame  Later,  of  been  (12)  the  the  thermal that  extremely  microwave to  g  of  the  emission electron  the  small  B-diketonates, 1 4  gas  workers  and  reported  to  10~  sensitivity  in  Early  ionization  Ross  of  used  metals.  responded  order  employed in  the  showed  fluorine-containing  comparable  that  DETECTOR  detector  on  could  factor  extent  Eisentraut  metal  conventional detectors.  the  substitutes;  detectors  analysis  capture  detection  of  to  measured  acac.  volatility  types  a  fluorine  ligands are  fluorines  various  ELECTRON  Several  (7)  analysis  of  dependence  al.  »  thermogravimetric  atoms  lattice,  of  directly  fluorinated  fod  volatilities  volatility  et  fewer  fluorine  crystal  B-diketonates  highly  complexes tfa  in  Wolf  bulkier  B-diketonates.  volatility.  corresponds  substitution.  substituted  i n the  greater  B-diketonates  of  fluorine  with metal.  detector capture  10  The  electron  radioactive  isotope  (fi-particles). (adsorbed  effluent  from  electrons  collisions Further the  the  cause  collisions  results  from  decreases,  collected to  the  compared  In  in  to  a  is  passing  converted  to voltage  ECD  carrier  between  a  pair  groups. as  amines,  It  is  presence  where  through  of  molecules  short-term  cell  rises  current  and  the  cell  the  i n the  tend  electrons  are pulses  i s measured  pulse  interval  electron The  The  and is  pulse  capturing pulse  r e l a t e d to the  is  amount  cell.  selective in  i t s response,  halogens, peroxides,  i n s e n s i t i v e toward and  current  voltage  cell.  a  that  current.  when an  into  electrodes  The  uncaptured  constant  material  alcohols,  The  molecules,  process.  which i s l i n e a r l y  g r o u p s s u c h as  or  electrons.  of  s e n s i t i v e toward molecules c o n t a i n i n g  functional  gas  secondary  sample  current,  i s therefore  Ni  emitter  of  through  of e l e c t r o n c a p t u r i n g  6 3  foil).  absence  This  therefore  are  the  a  electrons  energy of these e l e c t r o n s  applying  to maintain  compound  such  by  reference  (frequency)  of  The  electrodes.  rate  nitro  the  used  over the  ionization  periodically  adjusted  highly  the  current  this  then  The  burst  electrons.  cell  passed  reduce the  however,  capture  a  contains  titanium  i o n i z a t i o n of  range.  standing  is  or  1.5)  energy  usually  platinum  column  constant  to  on  (Fig.  high  emitters  producing  thermal  detector  emitting  The  tritium  the  capture  electronegative quinones,  functional  hydrocarbons.  being  An  and  groups  important  11  Radioactive  N  Ceramic insulator  Fig.  1.5:  f o i l  Electron «;oUsctor  Electron  capture  detector  12  application  of  chlorinated  pesticides.  indication  the  ECD  has  been  in  Table  the  1.5  o f t h e ECD s e n s i t i v i t y  detection  gives  a  to different  of  general  classes of  compounds.  1.6  DETERMINATION OF TRACE METALS BY GAS CHROMATOGRAPHY Formation  of  chromatography trace  metal  from  separation  analysis  sensitivity metal  (2).  large been and  analysis  coupled  attractive  simplicity  determining of  chelation  (no s o l v e n t ) .  trace  gas  technique f o r  o f i t s speed,  o r by d i r e c t  of metals  with  and  i s a c h i e v e d by e x t r a c t i o n o f t h e  involved  on d e t e r m i n i n g  presence  because  sample  quantities  on  i s an  Chelation  solvent,  with t h e metal metal  chelates  an aqueous medium w i t h t h e l i g a n d  immiscible  in  volatile  in a  suitable  of the ligand  Although  the separation  early of  efforts  relatively  i n m i x t u r e s , r e c e n t emphasis has metals  i n biological  microquantities  macroquantities  of  of  one  others  substances  metal  in a  i n the  variety  of  the idea  of  matrices. Although analyzing experiments Janak  Lederer  metals were  and B r a n d t  (1) f i r s t  as v o l a t i l e  metal  done t o c o n f i r m t h i s (9,10) e a c h b r i e f l y  metal  acetylacetonates analysis  1960.  Bierman  mixtures  of  put forward  and G e s s e r aluminum,  by  chelates  i n 1955, no  concept  a t the time.  d e s c r i b e d t h e i r work on gas chromatography  (11) succeeded chromium,  in  i n chromatographing  and  beryllium  acac  13  T a b l e 1.5:  ECD s e n s i t i v i t y  t o various  Chemical Type  classes  Relative Sensitivity  Hydrocarbons  1  Ethers, esters  10  Aliphatic alcohols, ketones, amines; mono-Cl, mono-F compounds Mono-Br, di-Cl and di-F compounds  ofcompounds  100 1000  Anhydrides and tri-Cl compounds  1.0*  Mono-I, di-Br and nitro compounds  105  Di-I, tri-Br, poly-Cl and poly-F compounds  10°  14  complexes.  Complexes o f  gas  analysis,  phase  temperature  were g e n e r a l l y u n s u i t a b l e f o r  however,  requirements.  complexes proved their  acac  t o be  because  The  and  more u s e f u l .  l e v e l s by  sufficiently  the  fluorinated  electronegative fluorinated  stable  of  high  tfa  and  GC fod  T h e s e c o m p l e x e s , due moieties,  volatile  to  be  were  to  thermally  measured  at  low  electron capture detection.  Kawaguchi  et  al.  (13)  and  Dagnell  et  al.  (14)  first  a p p l i e d microwave e m i s s i o n d e t e c t i o n t o the d e t e r m i n a t i o n volatile  metal  B-diketonates  chromatography. chromatography analysis copper  of  and  Sakamoto coupled  trace  per  aluminum  million  emission Sievers serum They  at  utilized  line  of  matrix gas  were  part  were  of  the  able  to  microwave after and  3  interference Highly  the from  chromatographic  (ppb)  zinc  were  using  chromium  levels  emission  by  the  simple  blood  method.  in  o t h e r compounds  any  the  and  monitor  chromium  without  a  microwave  extraordinary selectivity peak  at  Black  to  of  into  i n human  detector  converting  chelate other  a  the  Traces  measured  metals.  gas  to  metal  selective  s e p a r a t i n g i t from  This  efficient  and  measure  emission  from  gas  applied  samples.  individual  the  chromatography. of  (ppm)  by  (15)  microwave  solution,  billion  to C r ( t f a )  al.  extracted  per  chromium,  detection  with  level  detection (16)  et  i m p u r i t i e s i n metal  trifluoroacetylacetone part  separated  of  a the by  allowed  detectable  compounds.  solvent extraction  instrument  conditions  techniques  have  been  and  gas  developed  15  for  quantitative  6-diketonates  metal  i n organic  water f a c i l i t a t e s from  aqueous  Morie  Schwarberg  widespread  containing  to  separation  analysis, using The  (22-25). of  the  gas  to  detect  samples.  to  11  of  and  4xl0~  few et  and  toxicity  chelation,  determine  beryllium  f o r the  of  iron  al.  (25) 1 ppm and  mixture.  procedure  the  berylliumdevelopment  i n the  blood  i n lunar  capture (19)  was  and  material  gas  concentrations  form  urine  beryllium  i n meteorites. and  this  samples  Sievers  in  for  extraction.  of  determined  extraction  gas  electron  technique  beryllium  ions  d e t e c t i o n of  by  in  and  beryllium,  detected  this  metal  applied  environmental  ppb  missions  employed  g  1 4  been  l e s s than  12  severe  (19-21) and  Using  Eisentraut  concentration Apollo  a  (17)  extraction  alloys necessitated  has  chromatography.  able  (24)  as  t f a complex,  Sweet  aluminum  techniques  of  insolubility  outlined a general  fluids  little  and  an  and  compounds and  As  their  q u a n t i t a t i v e c h e l a t i o n and use  in biological  of  solubility  e x t r a c t i o n of metal  the  (18)  of s e n s i t i v e a n a l y t i c a l metal  and  c h e l a t i o n and  methods  chromatographic  alloy  the  The  solvents  media.  quantitative  M o s h i e r and  analysis.  at  from  Pyle  a  the  et  al.  chromatography  in  ambient  air  particles. Chelation several (26) as  other  measured the  measured  tfa in  and  gas  chromatography  metals  in  3xl0~  g  1 4  various of  Trace  soil  in  (23),  from  quantities  liver  been  matrices.  chromium  complex.  have  tissue  applied  Savory  et  human b l o o d of (27)  chromium and  in  to al.  serum were lunar  16  samples, (28). to  with  a mass s p e c t r o m e t e r  as t h e d e t e c t i o n  Gas c h r o m a t o g r a p h i c a n a l y s i s was s u c c e s s f u l l y  inorganic  systems  by  Genty  e t al.  device applied  ( 2 9 ) , who  detected  0.1 ppm o f aluminum i n u r a n i u m . Measures determination  and  Burton  of dissolved  natural  waters.  selenite  i n a 100 mL  to  form  and  The  selenite  method  (7.9xl0~  determined  by ECD-GC.  the determination  natural  waters,  determination  of  as  beryllium  (32) and aluminum  use  t o chelate  toluene.  0.57 nM  1.7  based  reaction  into  toluene  limit  o f 10 pM  (31) d e s c r i b e d  a method  and  total  chromium  with  f o r the  limits  and  a n d aluminum,  reported  Both  subsequent  o f 2 pM  in  subsequent  determination  (33) i n s e a w a t e r .  the metals  Detection  of  (1.8xl0~  of  methods  extraction 5  s e a w a t e r were  ppb) and reported  respectively.  THE DETERMINATION OF CHROMIUM IN SEAWATER  point  of  dissolved 2 4  the  chelates,  methods  Seawater i s a h i g h l y  S0  Gosink  (0.015 ppb) f o r t h e o r i g i n a l  for beryllium  selenium i n  M e a s u r e s a n d Edmond have  ECD-GC  into  f o r the  4-nitro-o-phenylenediamine  aluminum  shipboard  Htfa  and t o t a l  A detection  Htfa  by ECD-GC.  method  w h i c h was e x t r a c t e d  ppb) was r e p o r t e d .  4  a  entailed  sample w i t h  5-nitropiazselenol  then  for  (30) r e p o r t e d  ~,  Ca  view, salts 2 +  ,  because  complex m a t r i x , of  the  ( 3 . 5 % by w e i g h t ) .  and M g  2 +  ,  account  large  f r o m an a n a l y t i c a l concentration  S i x ions;  C l ~ , Na ,  f o r 99% o f t h e s e  +  of K , +  dissolved  17  salts.  Cr  exist  at  Vertical are  and o t h e r  trace  concentrations  of  less  o r depth d i s t r i b u t i o n s  investigated t o help  processes of these  elements,  which  control  1  e l u c i d a t e t h e major the concentration  hand,  M9/ 3  (ppb).  k<  of t r a c e metals  methods  i n seawater  biogeochemical.  and  f o r the determination  n a t u r a l w a t e r s have b e e n r e p o r t e d . been u s e d f o r t h e d e t e r m i n a t i o n others  have  either  separately  allowed  involved  procedures analysis  than  the other  distribution  elements.  Several  have  on  the determination  substantial  which  Some o f t h e methods have  of t o t a l  or together.  are  viewpoint;  clearly  none  chromium o n l y  while  of Cr(III) or  Most  sample  o f chromium i n  Cr(VI)  o f t h e methods  handling  and  undesirable  o f t h e methods  used  pretreatment  from  a  has had  trace  shipboard  application. Subramanian determination atomic  of  absorption  extraction  involved  and  a  Cr(VI)  spectrometry  ketone  method by  after  extraction  determination  obtained  an  for  the  graphite  furnace  initial  solvent  of  system.  Cr(VI)  The  procedure  followed  by  of [Cr(III)+Cr(VI)] with  by d i f f e r e n c e .  A detection limit  the  Cr(III)  o f 5.8 nM  C r s p e c i e s was o b t a i n e d .  Cranston Cr(III)  Cr(III)  determination  simultaneous  f o r both  reported  s t e p u s i n g t h e ammonium p y r o l i d i n e c a r b o d i t h i o a t e -  methylisobutyl  being  (34)  was  hydroxide,  and  Murray  selectively  and a f t e r  (35) u s e d  a  technique  coprecipitated  dissolution  using  i n which iron(III)  of the precipitate,  C r was  18  determined  by  graphite  spectrometry. way  using  Cr(III)  Total  hydroxide.  A  by  et  al.  from  graphite  furnace  atomic  ion-exchange  reduced  to  C r ( I I I ) by  seawater  sample  minutes.  A  (37)  for  the  limit  and  of  3.84  Cr(III)  nM and  chemiluminescence (38) .  The  reaction  found  was  columns with  system  luminol  1.92  that  f o r Cr(VI)  for  by  200  in  although  et  seawater. dilution  A  of  detection  determination  chromatography by  Williams anion  et  al.  cation  Post-column  allowed  detection limit  with  and  parallel.  nM.  al.  chemiluminescence  Simultaneous  reported  mL  several  Chang  interference.  5.76  a  was  reported.  Cr(III)  in  was  to  stand was  Prior  Cr(VI)  2  chemiluminescence The  determination  S0 -water  to  ion  total  spectrometry.  involved both  connected  immobilized  by  bromide-ion  using  iron(III)  an  interfere,  obtained.  to  to  reported.  employed  of  Cr(VI)  dissolved  nM  was  d e t e c t i o n was  detection.  and  to  Cr(VI)  sensitivity nM  0.76  similar  preconcentrate  of  i t  eliminated the  separation  exchange  allowing of  was  followed  addition  utilizing  enhancement  to  the  determination  i o n s were  seawater  signal  a l l  chemiluminescence the  Magnesium  and  the  nM  absorption  step,  a  reduces  used  seawater  in  oxidized  0.02  agent  detection limit  Luminol  of  chelating  Cr(III)  the  which  of  absorption  determined  (36)  as  to  atomic  simultaneously  detection limit  diphenylcarbazone  was  hydroxide,  being  Willie  chromium  chromium  iron(II)  while  furnace  for  for  Cr(III)  high was  19  Lan  et  procedure waters  al.  (39)  reported  for differentiating  followed  activation. different  by  The  pH  0.58  nM  method  values  using  Siu  involved  of  the  al.  seawater  by  monitoring  the  the  two  monitoring  mode.  1.8  population main  of  5  oxidation  There  four  are  (4.35%),  5 2  Cr  toxicity  is  maintenance  a detection  with  o f 0.15  a  nM  5 1  Cr  humans,  to  has  Htfa  considered  to  glucose,  ion  reported.  outer  in  from  The 100  chromium  (9.50%) and  5 4  shell  nature  Cr(VI).  varies  on be  and  selected was  an  exist  and  with  depends  gas  chromium  in  to  300  T  =  1/f2  and  its  lipid,  27.8  oxidation  and  5 0  (2.36%).  which The  organisms,  state  mammals  protein  Cr  In  days.  terrestrial  e s s e n t i a l to  ppm.  isotopes:  Cr  two  reported  a r e a number o f r a d i o a c t i v e i s o t o p e s o f is  limit  dilution  chromium  naturally occurring Cr  lead  liters.  24)  tends  crust  5 3  with  two  CHROMIUM  Cr(III)  earth's  lived  of  species  isotope  the  of t h i s metal t o aquatic  including Cr(III)  and  (83.79%),  addition there longest  1  neutron  to determine t o t a l  number  states,  i n the  2  A detection limit  3d 4s  by  c o p r e c i p i t a t i o n at  mass f r a g m e n t s w i t h  + 2  (atomic  abundance  the  complexing  i n natural  chromium  chromium  used  MARINE GEOCHEMISTRY OF Chromium  Cr(III)  They r e p o r t e d  (40)  Cr(tfa)  and of  sample v o l u m e s o f  et  step c o - p r e c i p i t a t i o n  Cr(VI)  chromatography/mass s p e c t r o m e t r y from  two  determination  p y r o l i d i n e dithiocarbamate. of  a  (41).  for  the  metabolism.  20  C r ( V I ) o n t h e o t h e r hand i s r e p o r t e d  t o be t o x i c b e c a u s e o f  its  and i t s a d v e r s e  impact  B o t h chromium  species  on  ability  to oxidize  t h e lung,  enter  the  from  industries,  cooling  oxidative  coordination  the  largest  transition  metals  of  substitution slow,  (46,47).  The l a c k  with  electrons  of  effluent  from  inputs  sanitary  of crustal  a  The s o l u b i l i t y  pH  8.5  and  In  preference  Q  energy  the  (45).  waters  residence  time  available to tends t o form  F o r example, t h e of  hydration  o f about  two  of the coordination  of Cr(III)  of electron  are hours  sphere transfer  hydroxides or oxides i s  maximum o f s o l i d i s controlled  spin  e n e r g y i s 6/5 & ,  As a r e s u l t , C r ( I I I )  of  octahedral  are i n the high  stabilization  of labi-lity  The s o l u b i l i t y  by  Cr(OH)  3  i s a b o u t 400  the intersection of  and C r ( O H ) " ( 4 8 ) .  + 2  4  ( V I ) t e n d s t o f o r m m o s t l y o x o compounds.  its  large  and  the soluble  common  natural  l i m i t a t i o n s on t h e mechanisms  reactions.  Cr  and l e a c h i n g s  i n e r t complexes  extremely  Cr(OH)  result  3d e l e c t r o n s .  site  (44).  rates  at  a  e l e c t r o p l a t i n g and t a n n i n g  as from  three  octahedral  kinetically  nM  dyeing,  has t h r e e  these  strong  low.  towers,  and t h e c r y s t a l f i e l d  imposes  as  through r i v e r s and t h e atmosphere.  Chromium(III)  states  (42).  primarily  (43), as w e l l  materials  species  and k i d n e y s  waterways  discharges  landfills  liver  other  ionic  species.  potential,  i t i s an e x t r e m e l y  tetrahedral  chromate  Because o f strong  ion Cr0  - 2 4  acid  i s the  21  Elderfield are  the  only  the  most  (49)  calculations  have  been  state  In predict  Brewer  used  changes  environmental in  to  the  t o Cr  that  (51). determine  Cr(OH)  account  The  reduction  should  equilibrium ratio  the  seawater  at  of  20.9  Cr(VI)  is  and  The Earley the and  and  kinetics  and  Cannon  of (52)  pH  12.6,  should  shown i n F i g . 1.8  + 3 pE  and  that  oxidation  as  well  as  discrepancies  C r ( V I ) as  4  Cr0  2 4  ~  (2)  + 2  66.1  pE  - 66.1  (3)  of  surface  oxygenated  respectively,  predominate.  The  the  ratio  equals  pE-pH r e l a t i o n s h i p  (51). the  oxidation  are  concluded that  differences in coordination Cr(VI)  as  follows:  2  = 6 pH  average  8.2  Cr(VI);  o f d i s s o l v e d chromium i s t h e n :  log Cr(VI)/Cr(III)  Taking  2  4  however,  probable  log K = The  Cr0 ~ ,  techniques  = Cr(H 0) (OH)  2  waters,  be  found, of  (VI)  thermodynamic  f o r the  as  Cr  and  4  handling,  may  + 2 H 0 + 3e"  +  form  species,  takes place  +  2  waters,  sample  2  (H 0)  + 2  variety  Cr  ( I I I ) and in natural  have b e e n  The  results.  + 6H  2 -  Cr(OH)  stable  Cr(III)  variability  ( I I I ) as  4  the  during  reported  Cr0  being  states  oxidizing  amounts o f  by  oxidation  species  respectively.  reviewed  s u g g e s t e d ' t h a t Cr  significant  probable  significant  has  (tetrahedral).  known  this  i s due  between C r ( I I I )  Using  Cr(III)  to  be  slow.  i n part  to  (octahedral)  spikes  added  to  22  23  Columbia  River  observed  a first  order oxidation h a l f - l i f e  changes  i n the  The and Cr  estuary  distribution  in  intermediate  total  Cr  at  the  top  of  increased  deep  profiles  element). of  Cr(VI)  was  reduced rapidly  AIM  OF  for  similar  to  The  those  4.0  Cr  deep  of  s c a v e n g e d by  nM  at  the  than  2.5  concentrations water  silica  They  region  reported  less  t h e minimum i n t o t a l Cr.  (a  levels)  and  i n the  particulate  understand  trace  metals  sensitive,  determination of  samples  artifacts.  Much  eliminating  or  element  Pacific  of  with  the  (a n u t r i e n t C r were  high  concluded  that  o x y g e n minima, much  the v e r t i c a l  particle  of  flux.  PRESENT STUDY  of  determination collect  nM  to C r ( I I I ) at the  desire to  distribution  their  being  minima.  month.  i n a study  t o a minimum o f  5.0  C r ( I I I ) and  w h i c h was  search  about  (48)  3.0  (53)  influence input  oxygen  between  oxygen  Coincident with  values  The  to  of  low  Murray  o f one  tropical  have  decrease  the  and  M u r r a y e t al  eastern  waters  a sharp  then  1.9  the  concentrations  surface with  Cranston  o x i d a t i o n s t a t e can  removal from the ocean.  where  nM  water,  sampling,  rapid in  trace free work  the metals  of in  in  factors  the  and  accurate  seawater depends  developing  and  that  oceans  contamination  controlling storage  the  has  control  the  led to  the  techniques  matrix. on or  the  Accurate ability  other  conditions  contamination a n a l y s i s has  for  to  sampling aimed  during therefore  at  trace been  24  done  (54).  It  contamination the  control  ability  great  to  a  possibly  doing  some  to  acquire  adverse  sampling  strategies  ability  high  (ECD-GC)  volumes  permits  of  fact  that  of a  particularly This method  the  would  GC  study  Cr,  was  after  already  a  been  of  to  sea-going developed  of  two)  ability. f o r Se  data  to  date.  rapidly  ship  is  of  modifying and  any  affords  unforeseen  gas  chelates  easily  nature  and  coupled  inexpensive  of  collected general with  the  makes  i t  ships. at  the  development  dissolved (with  Cr(III)  Cr(VI)  i n seawater Similar  (30),  detection  volatile  motion  onboard  reduction, these  sea  later  of  capture  compact  t h e r e f o r e aimed  of  at  samples  a  proceeds  small,  relatively  determination  difference have  use  f o r use  the  onboard  solve  electron  The  is  collecting  treatment  at  of  field.  equipment  suitable  f o r the  dissolved  the  be  potential  involve  possibility  fluorinated  the  seawater.  insensitivity  of  of  exist  and  i n the  would  accurate  gathering  identify  sensitivity  metals  and  that  a l l stages;  controlling  transporting  the  data  problems  chromatography trace  as  at  sea  preliminary  precise  provides  to  contamination The  at  procedures  then  ensure  observed  and  conditions that  This  the  to  laboratory for determinations  ability the  are  determinations  monitoring  benefit.  as  procedures  p r e c o n c e n t r a t i o n ) , and  under  important  C u r r e n t l y most  shore-based  The  very  the  in  contamination.  (e.g  do  benefit  samples,  is  Be  being by  and  Al  a  total  obtained  ECD-GC  methods  (32)  and  of  which  that  have  (33)  have  25  allowed several  the  determination  oceanographic  Cr between  elements  at  concentrations  in  2-5  nutrient-type distribution  nM  with  a  enrichment  in  cycles),  biological  (54).  these  due  to  the  seawater  at depth  of  I t i s hoped t h a t t h e r a p i d  here w i l l  greatly  t h e s e and  other factors  are  reported  as a r e s u l t  complicated  influence  of  i n suboxic  changing  on  redox  and  to  (surface  or  anaerobic conditions developed  insight  that are r e s p o n s i b l e f o r the  chromium.  fall  involvement  s e a - g o i n g method  enhance o u r u n d e r s t a n d i n g  oceanic chemistry of  sea  cruises.  d e p l e t i o n and  areas  of  into  general  26  CHAPTER 2  EXPERIMENTAL  2.1  INSTRUMENTATION  2.1.1  Gas A  10-15  Hewlett mCi  study. ratio  Ni  electron  series  capture  was  through  a  I t was  molecular  before being was  after  UHP  removes  present  sieve  an  a  in this a  split  DB 210 15 m  then  by  The N oxygen  2  fed into  of  passing i t hydrocarbon  the detector  gas p u r i f i e r  moisture  g a s was trap  a  purity  The d e t e c t o r makeup  carrier  amounts  high  first  through  t o t h e GC. and was  ultra  trap  or  oxygen  subsequently  passed  which  complements  the  trap.  Data Hewlett  further  a heated  trace  indicating  with  mode w i t h  hydrogen  trap  nitrogen  i n t h e stream.  through heated  any  used  A J & W Scientific  purified  passing i t through  which  d e t e c t o r was  g a s was  supplied  grade  equipped  c o l u m n w i t h a 0.5-fim f i l m t h i c k n e s s  The c a r r i e r  grade.  I I GC  run i n the s p l i t  o.d. c a p i l l a r y  used.  trap  5890  o f a p p r o x i m a t e l y 10:1.  (UHP)  gas  6 3  Packard  The ECD-GC  x 0.25 mm was  chromatograph  handling Packard  HP-Chemstation  from  GC  personal  3 365 s o f t w a r e .  was  performed computer  on  an  equipped  on-line with  27  2.1.2  Mass  Mass were  spectral  obtained  spectrometer  2.1.3  the  data  with  in  and  using  the  this  Elemental  Carbon on  spectrometry  electron  use  of  a  impact  Kratos  ionization  MS  50  mass  Department.  analysis  hydrogen  synthesized  elemental  metal  analysis  chelates  by  were  Mr.P.Borda  performed of  this  Department.  2.1.4  p_H  pH m e a s u r e m e n t s meter  equipped  were  with  a  performed using 91-02  general  an O r i o n  purpose  SA 520  pH  combination  electrode.  2.1.5  Shaking  Shaking action  2.1.6  accomplished  with  a  Burrell  Model  75  wrist  shaker.  Heating  A speed  was  Samsung up t h e  MW2570UC home  chromium  microwave  extractions.  oven  was  employed  to  28 2.2  MATERIALS AND  2.2.1  1,1,1-trifluoro-2,4-pentanedione The  was  ligand,  purchased  use, a  this  flask  or  was  of  10  distillation Cole-Palmer  middle  25  distilled  described  a ground o.d.  h e a d was  x  glass mm  in a  of  Teflon  impure m a t e r i a l  stoppered  distillation  2.2.2  was  Prior  100  mL  (32),  to a  tubing  and  peaks  sufficient  to restore  The  through  In o r d e r t o  the  i n the  a  freezer. a  get  three  ligand  developed;  the  f o r use  i t at least  complete,  cm  then running  t o h i g h enough p u r i t y  extraneous  15  tubing into  and  bottle  The  tubing.  elbow j o i n t  condenser.  to  distillation  tubing adaptor  out  to  pressure i n  al.  i . d . Teflon  was  Teflon  (Htfa),  contaminants.  necessary to d i s t i l l  distillation  however,  a  et  o b t a i n e d by r u n n i n g t h i s  piece  Once  metal  from  (T-63970-30) T e f l o n cm  Measures  and  8  Company.  at atmospheric  by  organic  s t u d y , i t was  times.  was With  single  i t s purity.  Toluene The  grade  Chemical  of a conventional L i e b i g  this  stored  Aldrich  constructed  by mm  initially  use,  as  connected  another  the  remove  still  length  in  from  still  minimize Teflon  1,1,1-trifluoro-2,4-pentanedione  compound was  Teflon  the  REAGENTS  solvent  (whichever  distillation  used was  through  was  toluene  BDH  available).  a 4 ft x  1.5  A.C.S. It  inch  was  glass  or  Omnisolve  purified still.  Two  by or  29  three  distillations  were n e c e s s a r y  extraneous peaks from o r g a n i c toluene used  was  as  then spiked the  100  approximately 2.2.3  buffer  sodium  acetate  remove  trace  present. 100  g  (DI  H 0)  standard  at  The  a  prepared  from  of  redistilled which  was  concentration  of  ng/mL.  of  in  filtered  250-mL  a  by  bench. An involved the  The  alternate  was  way  100  of  The  was  as  Htfa  was  adjusting  hours  procedure  the  ligand the  sodium  seawater  to  water  scavenge  b u f f e r pH  by  in a  was  using  unit.  To  a the  ethanol  which  Teflon  still  stored  in  for recrystallization.  approximately  impure  then  to  follows:  filter  i n the  collected  few  as  solution  absolute  was  once  deionized  filtration  mL  allow  cleaning  redistilled done by  to  i t for a  t r e a t i n g the same  of  grade  contaminants  was  polycarbonate  filtrate  material  yield  mL  double d i s t i l l a t i o n  overnight  leaving The  metal  bottle.  Millipore  added  by  in  Teflon  0.40-juM  a  above.  recrystallized  other  100  dissolved  acid-cleaned  refrigerator  and  recrystallized  was  s o l u t i o n was  described  Cr  been  analytical  procedure  been p u r i f i e d  dried  of  had  BDH  recrystallization  through  previously  was  amounts  NaAc  2  used  (NaAc) w h i c h  The  filtered  in  contaminants.  solvent  Buffer  The  had  clear this  2,6-dichlorobiphenyl,  with  internal  to  filtration  laminar  flow  the The and clean  60%. f o r the acetate samples any to  Cr  sodium buffer and  acetate solution  using  present.  approximately  the This  6  with  30  double  distilled  acetic  extraction  with  (described  i n the general  several all  times  with  i n a similar  was  were  was c l e a n  made  manner  procedure).  by  solvent  t o t h e samples  The b u f f e r was r i n s e d toluene  equally  enough  t o ensure  purely  on  effective  f o r use i n t h i s  choice of the r e c r y s t a l l i z a t i o n work  followed  that  removed.  procedures  which  (HAc)  the r e d i s t i l l e d  t h e H t f a h a d been Both  NaAc  toluene  acid  procedure  the  basis  in  producing  study  and t h e  f o r a l l subsequent  of  time  and  labour  savings.  2.2.4  Sodium s u l p h i t e The  1 M sodium  s u l p h i t e (BDH ACS g r a d e )  for  the reduction of Cr(VI)  use  of  the r e d i s t i l l e d  Htfa  to Cr(III), ligand  solution  was c l e a n e d  as  described  used  by t h e f o r the  sodium a c e t a t e b u f f e r above.  2.2.5  2,6-dichlorobiphenyl This  purchased spiked  compound from  All  into  as  the toluene  by d i s t i l l a t i o n  other  used  the internal  Chem. S e r v i c e I n c . ,  directly  purified  was  reagents  were u s e d w i t h o u t  Westchester,  after  as d e s c r i b e d  standard PA.  the l a t t e r  as  I t was had been  above.  were o f a n a l y t i c a l  further purification.  grade q u a l i t y and  31  2.2.6  Separatorv  The funnels  funnel  smallest  commercially  a r e 125 mL  and t h e i r  sample v o l u m e s i n t h i s of  some  study  of the organic  available Teflon use with  the r e l a t i v e l y  20 mL)  Teflon  easily  by  Teflon  tubing  Teflon  taking  layer  separatory an  on t h e w a l l s  of the vessel.  separatory  constructed  2.2.7  Deionized from  funnel  Cr(VI)  were  standards. Cr(VI)  this  study.  2  done  of heat  Separation  quite shrink  standard of  r e a c t i o n was a c h i e v e d  the using  H 0) 2  used  Nanopure  in  this  study  was  Series  630 D e i o n i z a t i o n  standards  f o r C r ( I I I ) and  i n the laboratory.  standards  atomic used  a s ammonium  DI H 0  piece  stopcock.  (DI  a Barnstead  1000 ppm  with  cm  was  Water  Aqueous C r Certified  1.5  phases a f t e r  water  System i n s t a l l e d  2.2.8  x  This  funnel.  Deionized  obtained  cm  funnel.  low-volume  and s h r i n k i n g one o f t h e ends o n t o a  aqueous and o r g a n i c this  18  low  w o u l d have r e s u l t e d i n t h e l o s s  This necessitated the construction of a makeshift (ca  separatory  absorption to  prepare  Cr(III)  appropriate  i n 1 wt.  dichromate s o l u t i o n  to appropriate  % HC1  extraction a n d 1000  i n w a t e r were  concentration  ranges  ppm  diluted  f o r use i n  32  2.2.9  Tris-(1,1.1.-trifluoro-2.4-pentanediono1chromium(111)  Chromium synthesized chloride (1.53 of  urea  the  as d e s c r i b e d  34.5 and  refluxed At  g,  over end  10  by  mL  DI  product  the  oven  purified as  the  spectra  by  65  was  Htfa  with  heating  the  was  collected DI  for  on  a  mixture  then  water a f t e r  which  recrystallization  two  times  with  The as  C  final and  a  in toluene  i n t o the  two  for  1 GC  H  yield  was  elemental  (results  revealed and  and  the  olive-  i t was  ethyl  and  dried  Cr(tfa)  g  the  funnel  was  3  acetate  (51%).  a n a l y s i s data  presented  )iL s o l u t i o n of  i t s trans  2.61  Mass  for  the  later). Cr(tfa)  3  compound  t h a t t h i s compound e l u t e d cis  isomers  g  swirling.  The  buchner  crude  of  20  stopped  The  Injection  flask.  constant  hr.  well  °C  compound were o b t a i n e d  peaks  purified  to  1  solvent. as  (III)  t o c o o l t o room t e m p e r a t u r e .  formed  at  Chromium  (55).  added  f o r 7 hr  period  washed s e v e r a l t i m e s w i t h in  was  was  3  w a t e r were added and  this  allowed  e t al.  (Cr(tfa) )  250-mL r o u n d b o t t o m e d  a steam b a t h of  Fay  mmol))  mmol) i n a  100  m i x t u r e was drab  trifluoroacetylacetonate  (1.58  g,  standard  which  were  as  well  resolved.  2.3  PROCESSING Sample  filtered  processing  in  a i r environment  the  within  laboratory a  laminar  took  place  flow  bench  in in  a an  33  effort  to  reduce  surroundings. PFA  the  funnel, three for  The  bottles.  all  Before  reaction  their  were  first  containers,  leached  a week.  by  out  use, these  and  the  the  i n Teflon  60-mL b o t t l e s ,  Teflon  separatory a t 60 ° C f o r  by a weak ( a p p r o x . 1%) n i t r i c  acid  During  the Teflon  usual  b o t t l e s and s e p a r a t o r y  extractions  carried  from  i n 4 N hydrochloric acid  days f o l l o w e d  about  contamination  extractions  reagent  were  possible  rinsing  laboratory funnel  three  runs  were c l e a n e d  times  leach  between  with  approximately  gas  chromatograph  5-10 mL o f a c e t o n e .  2.4  OPTIMIZATION The  optimum  operation  and  conditions  the  solvent  both i n v e s t i g a t e d i n t h i s  2.4.1  operating  optimized to  i n order the  retention  were  procedure  step  were  study.  flow  to obtain  f o r t h e g a s c h r o m a t o g r a p h were the highest  chelate  3  f o r the  maintaining  monitored  temperature, gas  extraction  conditions  Cr(tfa)  times  peaks, w h i l e which  the  Gas c h r o m a t o g r a p h y The  ECD  for  and  chelate  to  achieve  and  good r e s o l u t i o n .  and o p t i m i z e d  were  oven temperature, d e t e c t o r  sensitivity  reasonable  internal The GC  of the  standard conditions  the i n j e c t i o n temperature,  r a t e and t h e d e t e c t o r makeup g a s f l o w  rate.  port  carrier  34  2.4.2  Solvent  The  optimum  chromium  from  recoveries spike  of  Nootka  extraction conditions  Sound  Island,  seawater  of  4.31  conditions  a  T h i s amount o f C r already  present  "blanks"  with  factors  were  ligand  of  a  2.4.2.1 The of  the same  between  been  and The  the  coast  acidified  to the t o t a l A  of  the  sample  but  pH,  the  was  in  Vancouver pH  2.1. Cr  seawater  with  The  Cr  no  Cr  following amount  of  extraction  q u a n t i f i e d by  the  use  running  organic  Cr  chelate in  toluene.  by 3  A  of  i n c r e a s i n g the  from the C r ( t f a )  matrix.  amount o f  series  reagent  obtained  the  at  of  of  of  of  s p i k e d samples.  effect  curve  basis  seawater c o l l e c t e d  stored  seawater.  recovery  the  seawater  west  equal  the  on  a  to  the  amount  alongside  prepared  pH pH  NaAc/HAc  t o Cr  in  calibration  standards  off  investigated:  added,  temperature.  had  r e a c t i o n / e x t r a c t i o n of  from  added  i s roughly  the  s p i k e s were r u n  spike  127°W)  which  the  determined  C r ( I I I ) was  (49°N  B.C.,  were  chromium  nM  for  was  adjusted  buffer  approx.  2  to  e x t r a c t i o n s as  to 8.  by  the  obtain These  a d d i t i o n of  various  samples  with  samples  were t h e n  i n the general  procedure.  pH  amounts  values  of  subjected  35  2.4.2.2 L i g a n d  The of  concentration  effect  pure  Htfa  conditions ranging  on  the  Cr  ligand  added,  constant,  from  20  recovery  was  to  200  while  of  increasing  keeping  other  investigated. juL  were  the  reaction  Ligand  added  to  amount  volumes  the  reaction  bottles.  2.4.2.3  Temperature  A  variety  of  the  optimum  determine extraction Different were  the  time  reaction/extraction parameters  Cr(tfa)  combinations  SEAWATER  Two  1.  of  reaction  of  for  the  chelate  3  shaking  with  conditions  to  formation  and  were and  investigated. without  heating  investigated.  2.5  this  and  types  SAMPLES  of  stored  seawater  samples  were  analyzed  in  study:  Filtered  seawater  samples  that  had  been  stored  samples  that  had  been  frozen  acidified. 2.  Filtered  seawater  immediately  In  addition,  Nootka  Sound  whenever  a  after  filtered (a  mixture  seawater  c o l l e c t i o n without  acidified from  matrix  was  two  seawater  being  acidified.  collected  d i f f e r e n t depths)  required.  in  was  the used  36  2.5.1  Stored a c i d i f i e d Samples  Bermuda, (General by  E.A.  from  were  Boyle  and The  of approx.  acid  2.5.2  central  collected  Oceanics)  Technology. pH  the  seawater  samples  North  using  mounted  on  a  were  2 w i t h 1 mL  per l i t e r  Frozen u n a c i d i f i e d for Cr(III)  the Northeast P a c i f i c  and  near  bottles hydrowire,  Institute  acidified  HC1,  and  of  to  a  stored i n  by  members  our  immediately  conditions,  research  frozen  i t was  hoped  collected  that  on  After  line,  filtration  they  integrity  with l i t t l e  o r no  30-liter  a Kevlar  acidification. the  from  Under of  the  these trace  changes i n the  J u s t p r i o r t o p r o c e s s i n g t h e s a m p l e s were  a l l o w e d t o thaw f o r a b o u t temperature  were  mounted  group.  without  m e t a l s w o u l d be m a i n t a i n e d , speciation.  Cr  Ocean n e a r N o o t k a Sound u s i n g  (General Oceanics)  of  samples  total  Flo bottles  room  steel  then  o f 6N  seawater  Go  redox  Niskin  Massachusetts  filtered  Ocean,  leached polyethylene b o t t l e s .  Samples  were  5-liter stainless  colleagues at samples  Atlantic  4-5  f o l l o w e d by  after reduction, total  Cr.  h r on t h e b e n c h and determination of  to achieve  Cr(III)  and,  2.6  ANALYTICAL Total  dissolved  seawater  samples  reducing  agent  acidification than  24  hr  frozen  was  (58).  were  of  was  determined  had not  been  Seawater  Cr(III), with  samples  with  sodium  The  for  by a d d i n g  t o a d d 20  nh  as  stored  immediate  being  determined  Cr(VI)  was  then  two v a l u e s . by u s i n g  F o r seawater samples  15  that  t o pH 2, t h e e x t r a c t i o n pH o f 6 ±  pH o f t h e p r e v i o u s l y  necessary  the  i n less  h a d been  f a c t o r o f 15 was a c h i e v e d  acidified  0.2 was a c h i e v e d  Cr  from  samples  to Cr(III)  sulphite.  mL o f s a m p l e a n d 1 mL o f t o l u e n e . been s t o r e d  these  thaw  total  Cr(IH)  acidified;  that  to  as t h e d i f f e r e n c e o f these  A concentration  had  to  of Cr(VI)  allowed  as  stored  added  reduction  first  reduction  obtained  Cr  that  causes  determination after  SCHEME  1000 (iL o f 2 M NaAc/HAc  frozen  buffer.  s a m p l e s was 8.2 a n d i t was  o f 10% HAc  t o achieve  the desired  e x t r a c t i o n pH. The the  general  determination  exception sulphite  being to  determination  2.7  of the  the  Cr  described in  addition  previously  below  a l l samples of  200  frozen  was  applied  with  the  JUL o f samples  1  M  to  only  sodium  during /the  of total Cr.  GENERAL PROCEDURE 15  the  procedure  mL  seawater  reaction  bottles  samples using  were an  measured  adjustable  accurately 10  mL  into  Eppendorf  38  pipet  and  6.0  0.2.  ±  added,  then Next,  then  internal  1 mL  The  bottles  microwave  NaAc/HAc  which  buffer Htfa  had been  were  level  20  microwave).  shaken  reagents,  f o u r a t a time  (equivalent  To r e d u c e  for five  the  expansion.  to  pressure  period  then  1 3 0 watts build-up  placed  power inside  wrist  were removed f r o m  five  seconds  samples  action  fully  separation  aqueous  and  layer  was  shaken  prevent  The  was  level.  the  which layers  shaker,  after  contents  f o r 10 s with formation can occur were  of when  allowed  room  by  for  this  65-70  °C.  f o r 1 0 min  on t h e  which  they  before  commencing  of  the  bottle  were  were  funnel, the The  organic  o f d e i o n i z e d water  emulsions NaOH  deflated  A t t h e end o f  discarded.  1 mL  this  for  t o the Teflon separatory and  with  returned  of  shaken  separated  i n the  the bottles  allow  then  were  The  to  t h e microwave and  a t room t e m p e r a t u r e  step.  transferred  hydroxides step.  cooling,  to cool  carefully  help  for  to  t h e s a m p l e s were a t a t e m p e r a t u r e  allowed  sodium  f o r 3 min a t m i c r o w a v e  capping  3 min a t t h e same power  mechanical  layer  before  The b o t t l e s  During  the  walls  manually  another  Cr i n the  seconds  d u r i n g m i c r o w a v e h e a t i n g , b o t t l e s were p a r t i a l l y  shaken  was  spiked with the  2 0 0 /uL o f 1 M  manually  of the various  and h e a t e d  squeezing  pH  ligand  For the determination of t o t a l i n addition  to  added.  mixing  power  of toluene  f r o z e n samples,  s u l p h i t e was  with  1 0 0 /JL o f t h e p u r i f i e d  standard.  previously  ensure  buffered  from  i s added  to separate  Ca  and  i n the  to Mg  next  and t h e o r g a n i c  39  layer  then  shaken  washing s t e p w i t h  f o r 20 s w i t h  1 mL  base i s c r i t i c a l  of 1 M  NaOH.  This  as i t d e s t r o y s t h e excess  l i g a n d w h i c h w o u l d o v e r s a t u r a t e t h e d e t e c t o r i f n o t removed. After  separation the organic  l a y e r was r i n s e d two t i m e s  a total  o f 2 mL o f DI w a t e r t o r i n s e  extract  was t r a n s f e r r e d t o a c l e a n g l a s s v i a l I t was r e a d y  o f f a l l t h e NaOHi,  for injection  into  with  lined  cap.  stage  o r i t c o u l d be s t o r e d f o r a n a l y s i s l a t e r  term  storage,  the extracts  were  stored  -15  °C  were  for  several  and  stable  with The  a Teflon  t h e GC a t t h i s on.  For long  i n the freezer at weeks  at  these  conditions. Cr(III) manner  with  of  M  l  and C r ( V I ) the only  sodium  standards  exception  sulphite  were  being  reducing  treated  i n t h e same  t h e a d d i t i o n o f 200 jxL agent  to  the  latter  standards.  2.8  QUANTITATION Quantitative  the  use o f  standards.  determination  the internal Two t y p e s  1. O r g a n i c  i n this  standard  o f standards  Cr standards  study  method  and  was  calibration  were u s e d :  made f r o m t h e p u r i f i e d  2. C r e x t r a c t i o n s t a n d a r d s  made b y  Cr(tfa)  3  40  2.8.1  Organic The  standard  weighing in  chromium  0.0039  23.5 mL  standards  solutions  of  g of the p u r i f i e d  of the r e d i s t i l l e d  Cr(tfa)  of  1.66xl0~  further  diluted  primary  organic  ppb.  This  dilute  from  1:1000 Cr  t o l u e n e w h i c h had been  standards  this  for  toluene with  then  a  This  3  with  was  standard,  Cr(tfa) .  standard  standard  efficiencies  g/mL  4  a  used  to  Cr  to  prepare curve.  also curves,  be  used,  instead  of  the  t o compute t h e a c t u a l  2.8.2  Chromium e x t r a c t i o n  2.8.2.1  Cr(III)  of  16.8  range  of  determined  c o n d i t i o n s had  Cr  this  extraction  Cr concentrations  correction.  standards  standards  Aqueous C r ( I I I ) e x t r a c t i o n  dilution.  final  Extraction  r e c o v e r i e s were  t h e seawater samples a f t e r b l a n k  primary  a  was  and t h e r e c o v e r i e s shown t o be q u a n t i t a t i v e ,  could  calibration  a  a  a  curve.  been found  in  spiked  solution  produce  Once t h e C r r e a c t i o n / e x t r a c t i o n optimum  curve  by-  producing  concentration  calibration  f o r optimizing  made  c h e l a t e and d i s s o l v i n g i t  with the 2,6-dichlorobiphenyl i n t e r n a l solution  were  3  standard  solution  Standards  C r ( I I I ) were p r e p a r e d  with  of  standards 384.6  0.190,  nM  0.380,  and u s u a l l y a n a l y z e d  were p r e p a r e d C r ( I I I ) by 3.850,  from  serial  7.690  i n duplicate.  nM  41 2.8.2.2 C r ( V I )  Aqueous a primary of  Cr(Vl) extraction  standards  s t a n d a r d o f 380.8 nM C r ( V I ) .  were p r e p a r e d Two  replicates  from each  1.620, 3.850 and 7.690 nM C r ( V I ) were e x t r a c t e d a s i n t h e  general  procedure  reducing  2.9  with  the addition  o f t h e sodium  sulphite  agent.  CHROMIUM RECOVERY STUDIES The  r e c o v e r y o f b o t h C r ( I I I ) and C r ( V I ) i n s e a w a t e r  evaluated Cr  standards  by s p i k i n g  s p e c i e s a t two  seawater  different  samples  s p i k e d a t t h e 2.150  and 4.310  was  spiked  a n d 7.690  samples  plus  analyzed  f o r Cr using the procedure  2.10  the  each  o f t h e two  concentration levels.  was  a t t h e 3.850  with  unspiked  nM  levels  nM  Cr(III)  whereas C r ( V I )  levels.  seawater  was  Both  "blanks"  spiked  were  then  developed.  REPRODUCIBILITY r  The  precision  running 6 r e p l i c a t e  2.11  of  the  was  a n a l y s i s on a s e a w a t e r  determined  by  sample.  ACCURACY The  analysis  of standard  National  Research  Council of  for  technique  the accuracy  r e f e r e n c e m a t e r i a l s from Canada was  of the technique.  Two  an  important  samples,  the test  t h e Open  42  Ocean  Seawater  Reference  Seawater R e f e r e n c e dissolved  Cr  Standard  Standard  using  (NASS-3)  (CASS-2) were a n a l y z e d f o r t o t a l  o u r method.  The  were a t pH 1.9 and were t h u s t r e a t e d samples  that  (7 r e p l i c a t e s  2.12  had been f o r each  and t h e C o a s t a l  stored  samples  as  purchased  i n t h e same way a s t h e  acidified  i n the  laboratory  reference material).  BLANKS DI w a t e r s a m p l e s were a n a l y z e d f o r C r ( I I I ) and t o t a l C r  as a  part  of the Cr extraction  period  the  limit To  H 0 2  the  of time,  determine  reagents volumes  analyzed.  DI  came  and  from  but with H 0 2  over  an e s t i m a t i o n o f  amounts  f o r Cr(III)  DI H 0 2  volume  Cr.  much came  amounts  added,  from  aqueous  added  mL  were  A least  gave  i n t h e DI  different  10, a n d 15  had been  and t o t a l  of  reagent  o f 5,  observed  and how  samples  constant  volumes  duplicate  versus  t h e water  handling,  reagent  signal  provided  how much o f t h e s i g n a l  identical  the  results  When a v e r a g e d  of detection of the technique.  extractions  phase  these  standards.  were  t o which analyzed i n  squares  an i n t e r c e p t  f i t of a t zero  v o l u m e w h i c h was t h e e q u i v a l e n t o f t h e r e a g e n t p l u s h a n d l i n g blank.  43 CHAPTER 3  RESULTS AND  3.1  DISCUSSION  CHARACTERIZATION OF T R I S - ( 1 , 1 , l - T R I F L U O R O - 2 , 4 PENTANEDIONO)-CHROMIUM(III) The  its  synthesized  mass  spectral  elemental  3.1.1  Table  Table  data  3  and  standard as  the  was  characterized  results  of  C  by  and  H  analysis.  Mass  analysis  Cr(tfa)  STANDARD  spectra  3.1.1  shows  of the C r ( t f a )  3.1.1:  the 3  results  of  the  mass  spectral  chelate.  Fragmentation ions o f t r i s - ( 1 , 1 , 1 - t r i f l u o r o 2,4-pentanediono)-chromium(III)  F r a g m e n t mass (m/z)  Intensity (% b a s e  Assignment peak)  513  1.5  5 4  512  7.5  5 3  511  25.8  5 2  359  21.5  5 3  358  100.0  5 2  Cr(tfa) + 3  Cr(tfa)  3  Cr(tfa)  3  Cr(tfa)  2  Cr(tfa)  2  +  +  +  +  44  The (Fig. m/z  511  observed  of  the 5 2  Cr)  7.5%  the  m o i e t i e s t o form peak  with  result  3.1.2  of the  as the  359  1.5%, with  the  5 3  of the  Cr(tfa)  and  5 2  ion  with  confirming  the  the  most  Cr(tfa)  and  + 3  abundant  ).  513  Also  (relative  respectively) resulting  a result 5 2  512  spectrum  Cr  and  loss  relative  Cr  isotopes.  o f one  molecular  + 2  5 4  ion.  intensity  of the t f a Similarly  21.5%  t o form  5 3  from  was  Cr(tfa)  as + 2  of  in  C  and  Table  H  3.1.2  elemental and  are  analysis  on  3.1.2:  a  .  Cr(tfa)  consistent with  s t r u c t u r e of the c h e l a t e .  Table  a  analysis  results  presented  m/z  l o s s of a t f a molecule  Elemental The  are  m/z  and  of (  mass  molecular  25.8%  ligand  with  the  the  chelation  the  ligand  b a s e peak was  of  intensity  with  peaks  of  of  verification  c h e l a t e by  were  of  aspect  relative  (  intensities chelation  the  and  isotope  The  important  3.1.1) was  formation Cr  most  Elemental a n a l y s i s data f o r t r i s - ( 1 , 1 , l trifluoro-2,4-pentanediono)-chromium(III)  Cr(tfa)  3  %  C  H  Calcd.  35.24  2.37  found  35.33  2.43  3  the  Intensity » » « L_ l  J  a s» s o>  &? §g T oo  XX M l Set  Bn  §  m  I  ft  •1  HHi H*  c o •1 oI i  !  i  I  I  L_ i  l_l  I I I I I I I I  I  I  I  46 3.2  QUANTITATIVE ANALYSIS IN I n GC,  of  either  with  that  q u a n t i t a t i v e a n a l y s i s i s b a s e d upon a the  peak  height  of  one  or  chromatographic lines  on  peak. and  the  of  the  side  or  more  that  sample  accurate  be  of  the The  analyte height  by  connecting  the  of  the  by  a  line  peak  distance  made w i t h  from  temperature,  injection during  straight  are the  so  line  eluent  period  high  as  required to  and  to  the  rate, not  to  obtain  t h i s measurement precision  a  base  flow  controlled  standards,  reasonably  this  peak of  obtained  c h r o m a t o g r a m s f o r s a m p l e and ordinarily  area  standards.  column  peak w i d t h s  the  comparison  is  perpendicular  Provided  rate  alter  peak  either  measuring  GC  and  can  yield  results.  Peak  areas  on  broadening  effects  from  standpoint,  this  due  the to  parameter than  the  a r e more e a s i l y  hand  are  independent  v a r i a b l e s mentioned  peak  analytical latter  other  areas  are  a  more  above.  Thus  satisfactory  peak h e i g h t s d e s p i t e t h e measured.  of  fact  that  47  3.3  QUANTITATIVE PROCEDURES IN PRESENT STUDY  3.3.1  C r ( t f a ) ^ trans ^ c i s isomerization A  calibration  compound ratio  problem  o f t h e two  can vary  involved.  quantities  of  GC o p e r a t i n g not  allowed  c i s and t r a n s ,  but the  their  aluminum  experimental  determination  and  a packed  t o the  chromium column  of  in  uranium,  and o p t e d  to select  achievable, based  thus on  conditions  avoided  either employed  having  isomer. in  to The  this  deal  study,  L o v e t t e t al. ratio only  attained Cr(tfa)  trans  3  isomer  isomerization place this on  only  Unless  thus  oven  d e p e n d on  4:1  trans:cis  initially  100%  proceeded  t o use t h e  Cr(tfa)  has been  temperatures  both  isomers.  constant  f o r quantitation.  GC  3  cis£  reported  (e.g.,  to  120 ° C )  trans  trans take (5);  i n e r r o r s i f q u a n t i t a t i v e a n a l y s i s i s based  the predicted  quantitation  They  i n t h e gas phase  can r e s u l t  a  dissolution of  i n benzene.  at typical  peaks.  (56) r e p o r t e d  after  were made i n t h i s Cr  between t h e two  GC  however,  f o r g o o d r e s o l u t i o n o f t h e two i s o m e r s .  constancy of the r a t i o  with  optimum  peaks a r e q u a n t i f i e d i n t h e a n a l y s i s , t h e r e s u l t s the  trace  c o n d i t i o n s where r e s o l u t i o n o f t h e two C r p e a k s  quantitation operating  This  according  In  G e n t y e t a l . (29) u s e d  for Cr(tfa) . 3  i s made up o f two i s o m e r s ,  procedures  was  arises  The based  magnitude study ratio  o f one o f t h e p e a k s .  t o monitor the area was  on o n l y  not  constant  Attempts  r a t i o o f t h e two throughout  and  one o f t h e p e a k s w o u l d h a v e  been  48  unreliable.  I t was  the  o f t h e two  sum  area  therefore peaks  decided  to quantify  Cr  instead  o f r e l y i n g on  using either  peak.  3.3.2  Internal The  Standard  internal  component,  Method  standard  method  that  an  extra  t h e i n t e r n a l s t a n d a r d , be added i n a known amount  t o e v e r y sample and s t a n d a r d . present  in  presence  i s detected  reference  requires  both  unknown  and  this  f o r an i n t e r n a l s t a n d a r d  extra  calibration  i n a l l analyses  or normalizing  1. I t must  Since  factor. compound  and  component i s samples,  i t serves  Some o f t h e  its as  a  requirements  include:  be a v a i l a b l e i n h i g h  ( o r a t l e a s t known)  purity. 2. I t must  be s t a b l e , b o t h on t h e s h e l f and  during  analysis. 3. I t must  n o t r e a c t w i t h any o f t h e sample  components.  4. I t must  chromatograph w e l l , y i e l d i n g a well-formed  peak. 5. I t must h a v e a r e t e n t i o n t i m e d i f f e r e n t f r o m any o f the  sample  components.  6. I t must be s o l u b l e  i n t h e sample o r i n t h e  solvent  used f o r t h e sample. 7. I t s h o u l d the  have a r e t e n t i o n t i m e comparable t o t h a t o f  components  of i n t e r e s t .  49  The  advantages  chromatography drift, the  and o t h e r  only  using  a r e many:  standard.  and  of  internal  instrument  the  peaks  of  in  gas  s e t p o i n t , flow,  column  a r e compensated  f o r by  possible variations  In a d d i t i o n  standards  t h e sample interest  size  i s not c r i t i c a l  need  be  eluted  and  calibrated. The areas  ratio  of  (or heights)  the analyte serves  to  internal  as t h e a n a l y t i c a l  standard  peak  parameter.  In  t h i s work 2 , 6 - d i c h l o r o b i p h e n y l , w h i c h h a d b e e n shown t o be a good Al  internal  standard  ( 3 3 ) , was u s e d .  time  of  retention  2.03  The i n t e r n a l  min  times  i n similar  under  the  f o r the  GC  standard  GC  trans  work  on Be  (32) a n d  had a  retention  conditions  and  c i s Cr  used.  The  isomers  were  2.66 a n d 3.35 min r e s p e c t i v e l y .  3.3.3  Organic The  chromium  standards  organic Cr standards  b a s i s but p e r i o d i c checks for  up 2-3 weeks  standards  were  decomposition  proved  Three standards,  sample  and any added  the purified  standard) standards  this  stable  stored i n the freezer  was n o t n e c e s s a r y .  a n d showed  and  of  f o r a few  with Cr concentration bracketing the  Cr spike  toluene injected  were u s e d  The  no e v i d e n c e  e v e n when s t o r e d a t room t e m p e r a t u r e  days.  in  on s t a n d a r d s that  remarkably  were i n i t i a l l y made on a d a i l y  only  c o n c e n t r a t i o n s , were  (already into  spiked  the  GC.  with  made up  the internal  Initially  these  t o quantify the Cr recovery  during  50  the  solvent  extraction  quantitative these  (100 ±  standards  concentrations  3.3.4  could  i n real  Cr(III)  extracted  from  quantify  the  samples.  be  Once  recovery  used  the were  directly  amounts  determine  and  t h e two  standards stored  these  Cr  were  the t o t a l  the solvent  standards,  these  Cr  extraction extracts,  from  procedure. despite  Chromium e x t r a c t i o n Deionized  alongside observed provided value  water  Like  that  these  f o r Cr(III)  (0  was  the organic a  was  used  with  from the  t h e DI  H 0. 2  extraction  host  of  stable.  standards)  vary  were  throughout.  much were  Cr averaged  1.017 ± 0.081 nM r e s p e c t i v e l y . blank  nM  of reagents  and t o t a l  useful  standards  containing  standards  d i d not  t h e same b a t c h  after  blanks  blanks  the Cr extraction  total  samples  these  to  seawater  to quantify  seawater  recovery  used  in  o t h e r e x t r a c t e d m e t a l - t f a c h e l a t e s , were e g u a l l y  3.3.5  Cr  routinely  were  species  used  frozen  were  The u s e o f t h e o r g a n i c C r s t a n d a r d s  confirming  however,  correction.  standards  water  of  found,  standards  Cr(VI)  deionized  conditions f o r  to  samples a f t e r b l a n k  i n the previously  after  Cr  and  The C r ( V I )  reduction. in  4%)  Chromium e x t r a c t i o n Both  Cr  stage.  from  0.390  I t was  day  used.  t o day  The ±  run  blank  0.062 and  The m a i n s o u r c e o f C r i n t h e This  blank  standards  i s therefore only which  contain  the  51  equivalent from  amount  reagents  (Section  of  DI  and  3.8.3),  H 0.  Contribution  2  handling  and  used  was  to  to  this  determined  blank  correct  blank  separately the  seawater  samples.  3.3.6  Calibration In  all  curves  cases,  calibration  plotting  the  standard  peak) a g a i n s t t h e  the  area  a  ratio  concentration  ratio  standard  concentration  standard  was,  concentration Figs.  by  standards, 3.3.7  Cr  running  of  internal  Theoretically  used. in  for  The  exactly  sample  internal the  and  Cr,  Cr(III)  same  standards.  3.3.6c shows t h e c a l i b r a t i o n organic  by  concentration/internal  be  both  obtained  peaks/area  Cr  present  a l l cases  was  concentration.  i.e.,  however, in  Cr  of  should  3.3.6a, 3.3.6b and  obtained  and  curves Cr(VI)  respectively.  Chromatograms Fig.  Cr(tfa)  3  3.3.7 from  extraction  3.35  after  2.03  peak  with  Al-tfa  shows  chromatograms  (a) s y n t h e s i z e d C r ( t f a )  standard  t h e t r a n s and and  (area  curve  and  min.  retention  standard,  The  identified time  and  1.57  internal on  min,  the  trans  (b) C r ( I I I )  The  peaks  o f Cr have r e t e n t i o n t i m e s  respectively. Also  cis  (c) seawater sample.  c i s isomers  min,  3  of  standard  of  c h e l a t e formed from t r a c e A l p r e s e n t  i n the  2.66  elutes  chromatograms  corresponding  for  to  is a the  samples  52  0.4-r  0.3--  0.0 A  0  1  2  !  4  1  6  Chromium concentration (pg/ul)  Fig.  3.3.6(a):  Organic Cr standards c a l i b r a t i o n curve ( e a c h p o i n t t h e mean o f two r e p l i c a t e s )  1  8  53  Fig.  3.3.6(b):  Cr(Ill) calibration  curve  Fig.  3.3.6(c):  T o t a l Cr c a l i b r a t i o n from r e d u c i n g C r ( V I )  curve obtained standards  54  CO CO CO  ><  M  cn W 2  —  •»  o  OB  •ft  TIME ( m i n )  Fig.  3.3.7(a):  Chromatogram o f s y n t h e s i z e d C r ( t f a ) s t a n d a r d (peak r e t e n t i o n t i m e s (min): I n t e r n a l s t a n d a r d , 2.042; C r , 2.682 & 3.351) 3  55  CO  f  en H  w  55 W E-< H  A  A  o  TIME ( m i n )  Fig.  3.3.7(b):  Chromatogram o f C r ( t f a ) from an e x t r a c t i o n s t a n d a r d (peak r e t e n t i o n t i m e s ( m i n ) : A l , 1.572; I n t e r n a l s t a n d a r d , 2.043; C r , 2.682 3  56  co EH H CO  55 w  2 if?  o  CC  cc  A  TIME ( m i n )  Fig.  3.3.7(c):  Chromatogram o f C r ( t f a ) from an e x t r a c t i o n s t a n d a r d (peak r e t e n t i o n t i m e s (min): A l , 1.572; I n t e r n a l s t a n d a r d , 2.042; C r , 2.682 & 3.351) 3  57  and  standards.  The  identity  of  the a n a l y s i s of a pure A l ( t f a )  the  peak  standard  3  was  confirmed  (details  by  in  Chapter  and  1,1,1-  4).  3.4  REDUCING AGENT The  reaction  between  chromium  trifluoro-2,4-pentanedione  to  form  2,4-pentanediono)-chromium(III) does  not  reduce  occur  Cr(VI)  with to  Cr(VI).  Cr(III)  for determination  of t o t a l  It  purpose  as  i t s e f f e c t i v e n e s s has  reducing other  al.  reagents  achieved  amount b u t  lesser  the  r e a c t i o n times.  3.5  SOLVENT  organic  was  solvents  have been used. obtainable  15  under these reducing  the such  200 mL  agent  and  necessary and  to  standards  chosen been  of  the  for  of  Cr(VI)  to  can this  demonstrated 1  M  samples t o g e t h e r  Na S0 2  3  with  the  Cr(III)  was  T h i s was  an  excess  amounts r e s u l t e d  in  longer  used  hexane,  Whatever t h e  i n high purity  ML  conditions.  solvent as  samples  already  conversion  overall  Toluene  i s therefore  s u l p h i t e was  Thus  added t o  and  rapidly  sodium  (53).  a g e n t was  for Cr(III)  Cr before c h e l a t i o n with H t f a  this  et  Tris-(1,1,1-trifluoro-  i n seawater  In  Lovett  Cr(III)  is specific  occur.  by  study  as  in  this  benzene  choice of  study.  etc.,  could  Other also  s o l v e n t , i t must  free of other organic  be  contaminants  58  t h a t might here  was  i n t e r f e r e w i t h t h e GC a n a l y s i s . easily  contamination bottle  after  purified  problems  OPTIMIZATION  3.6.1  Gas  the  conditions  sensitivity  Cr(tfa)  provided  i t was  were  of  chelate,  3  selected  shows  quantitative  Table  stored  in a  t o ensure  the electron  capture  as  good  well  as  r e a s o n a b l e r e t e n t i o n t i m e s f o r t h e peaks 3.6.1  and p r e s e n t e d  no  Teflon  chromatography  GC  possible  distillation  distillation.  3.6  The  by  The t o l u e n e u s e d  the  optimized  the highest detector f o r  resolution  of interest.  parameters  used  and Table  for a l l  work.  3.6.1:  Injection  Gas c h r o m a t o g r a p h i c c o n d i t i o n s f o r t h e a n a l y s i s o f chromium a s t r i s - ( 1 , 1 , 1 - t r i f l u o r o 2,4-pentanediono)-chromium(III)  port temperature  200 ° C  Oven t e m p e r a t u r e  130 °C  Detector temperature  350 ° C  Column head  15 p s i  pressure  Hydrogen c a r r i e r gas f l o w  2.6 mL/min  N i t r o g e n makeup g a s f l o w  49 mL/min  59  Capillary manufacture, to  affect  Silyl-8  for  do  the  Cr(tfa)  improving  any  ECD  sites of  in  column  found  to  at  metal  active  the  increase  somewhat,  them  in  which  chelates was  the  the  tend (32).  injected  beginning ECD  presumably  sites  during  of  to  each  sensitivity  by  temporarily  column  and  thus  sensitivity  electron capture  Cr(tfa)  chelate  3  as  response  was  linear  seawater  samples  between  conditioning  S p e c i a l t i e s Inc.)  chelate  injected  The  active  chromatography  was  3  careful  i t s performance.  The the  have  capillary  This  sequestering  3.6.1.1  gas  despite  (Chromatographic  run. the  s t i l l  the  deactivate days  columns,  the  0.6  obtained  and  as  resulting  could  for  up  in  and  As  be  to  in this nM  i s extremely  expected.  chelate  4.2  detector  detected three  study a  little  orders  pg  Cr  0.15  the of  Cr  concentration  0.47-3.29  as  and  a l l had  sensitive pg  to Cr  detector magnitude.  concentrations  factor in  of  15  was  each  1  JUL  injection. The  ECD  monitored 150-350  °C  sensitivity  lower  as  showed  no  and  chelate.  response  response  with  regard  This  is  seen  for  temperature.  to  the the  case  internal  function  of  appreciable  unlike  i n the  the  a  of  peak  variation  areas  factor Be(tfa)  standard  was  temperature  2  of  of  the  2  (32).  between Cr(tfa)  increase The  however  was  3  in  detector  reduced  at  60  3.6.2  Solvent extraction  3.6.2.1  pH  The  highest A t pH  5.6-6.5.  was of  observed Cr  reported The  allowed buffer  range  Ligand  3.6.2.2  The  e x t r a c t i o n of  added,  the  pure  and  a 1 5 mL  1 5 mL  the  5.5  x  ligand  an  5  /In t h e i r  ±  of  Cr  studies (26)  e x t r a c t i o n with  Htfa.  found  et  in  this  study  n e c e s s i t y t o make In  general  the  use  the  0.2.  t o d e p e n d on  and  used  extraction  for  added  (approximately  of  plus the  the  r e a c t i o n time,  /iL r a n g e  20-80  was  pH the  average t o t a l  /iL  found  (Fig.  amount  the  more  efficiency  for  3.6.2.2).  a l l extractions  s u f f i c i e n t f o r recovery  initially 10~  was  greater  s a m p l e p l u s any  sample  seawater  Cr  At constant  t h i s was  Taking  6.0  range  recovery  Savory  accurately.  t o pH  pH  al.  materials, f o r Cr  at  concentration  l i g a n d added.  study  t h i s , the  extraction  extremely  l i g a n d volumes i n the of  Cr  achieved  a s a f e t y margin p r e c l u d i n g the addition  ligand  was  3.6.2.1).  5.8-6.2  for  s a m p l e s were a d j u s t e d  of  Cr  (Fig.  biological  range of  pH  of  g r e a t e r than  decrease  in  a pH  wide  values  to  content  recovery  100  in  ML  this  of a l l the Cr  in  spikes. Cr  the the  concentration sum  1 0 nM  of the Cr present  highest  ligand  of  should  spike  in  added)  theoretically  in a the only be  61  10080--  x u o > o a  60-  K  40-  4) OS  208  6 PH  lOO-  Ps  u, a > o a  QS  40  BO  120  160  200  240  Htfa (pL)  Fig.  3.6.2.1:  C r r e c o v e r y vs. pH ( t o p ) ( e a c h p o i n t t h e mean o f two r e p l i c a t e s )  Fig.  3.6.2.2:  C r r e c o v e r y vs. H t f a l i g a n d v o l u m e ( b o t t o m ) ( e a c h p o i n t t h e mean o f two r e p l i c a t e s )  62  n e c e s s a r y f o r c o m p l e t e ,Cr e x t r a c t i o n . a  large  excess  quantitative This  (at  undissociated  could  fraction  negligible);  a  phase  cannot  which  as  used;  of  an  in  extremely  high  20  s  excess the  A  washing  with  this  the by  base the  Cr  by  pentanedione hours  shaking  percentage shaking  at  room  at  to  the  phase;  an  the  the in  to  than  the  Cr.  due  of  causes to  IM  the  NaOH f o r  this  before  Cr(tfa)  The  fluorinated  destroying  chromatogram  organic  phase  this  1 mL  aqueous  the  organic  ECD  being  experimental  analysis  by  that  an  of  other  phase w i t h  obtain the  quantitative  ligand,  temperature  were  extraction  time  the  follows:  and  excess after  chelate  was  extraction  of  3  r e a c t i o n time  with  time  of  ions  the  here.  washing.  attempts  reaction  in  for  (probably  complexed  during  shows  3.6.2.3 T e m p e r a t u r e and Initial  Htfa  problem of  as  under  metals  organic  comparison  destroyed  of  detector  eliminates  with  fraction  sensitivity  used  aqueous phase  that  required  organic  extracted  of  was  conditions  combined  a  Shaking the  ligand.  not  and  Htfa  the  i n the  be  t e s t s showed  distributed  in  complexes  problems  ligand.  be  fraction  tfa  presence  of  6  fraction  undissociated  phase  10 )  Cr e x t r a c t i o n at the  excess  conditions  least  The  required.  efficiency  room t e m p e r a t u r e .  1,1,1-trifluoro-2,4-  showed Fig. of  that  at  least  3-4  3.6.2.3a  shows  the  Cr  Lovett  as et  a  function al.  (56)  of have  63  reported  a room t e m p e r a t u r e s h a k i n g  o f b e l o w 10 nq/raL w i t h  Cr c o n c e n t r a t i o n s excess  (0.164  extraction.  M  time o f a t l e a s t  i n benzene)  Measures  i n order  (57) e s t i m a t e s  In  order  t o reduce extraction  t h e temperature  investigations about  Good  into  times  using  were  done  were  a water  shaking  bath a t reaction  i n between.  i n significantly  m i n was enough  to  Initial  the Teflon  regular  achieved  necessary  mixture.  using  immersing  necessary f o r  found  of the reaction  this  (30-40  time  o f C r , i t was  f o r d i f f e r e n t times with  Cr recoveries  reaction  maximum C r  a t room t e m p e r a t u r e f o r  the reaction  65-70 ° C a n d i n v o l v e d  bottles  to obtain  100 ixL o f H t f a .  quantitative change  the ligand i n great  87% C r r e c o v e r y  15 mL s e a w a t e r s a m p l e s a f t e r s h a k i n g 2 hr using  2 h for  reduced  f o r 90% C r r e c o v e r y )  a l t h o u g h r e p r o d u c i b i l i t y b e t w e e n r e p l i c a t e s a m p l e s was p o o r . Using eliminated (100 be  t h i s problem.  oven  Various  well  controlled, allowing  reaction  investigated.  was  between  times/microwave A total  20 ( e q u i v a l e n t  combination but  was c h o s e n .  with  excellent could  f o r good r e p r o d u c i b i l i t y . power  level  time  t o 130 W a t t s on t h i s that  combinations  o f 6 min,  a 5 s manual  The m i c r o w a v e  reproducible.  however,  a n d t h e power l e v e l  reaction  gave C r r e c o v e r i e s  were v e r y  t h e samples,  N o t o n l y was C r r e c o v e r y  b e t w e e n two 3 m i n s e s s i o n s , in  t o heat  ± 4%), b u t t h e r e a c t i o n time  very  were  a microwave  power  shaking level  split time  adopted  microwave) and t h i s  were n o t o n l y  excellent  64  1  2  3  Shaking time at r o o m temp, (hrs)  100-(b) 80-% o a K  60--  40-20-0--  20  40  60  60  Shaking time (min) after microwave  Fig.  Fig.  3.6.2.3(a):  3.6.2.3(b):  C r r e c o v e r y vs. s h a k i n g t i m e ( h r s ) a t room t e m p e r a t u r e ( e a c h p o i n t t h e mean o f two r e p l i c a t e s ) C r r e c o v e r y vs. s h a k i n g t i m e (min) a f t e r microwave i r r a d i a t i o n (each p o i n t t h e mean o f two r e p l i c a t e s )  65  The At  the  bottles  end  of  temperature cool  were  the  i n the  min  to  room  step.  microwave  microwave  of approximately  them  extraction  6  put  70  °C and  temperature  During  the  the  Extra As  Cr  was  chelated  c o n t a c t time,  can  be  seen  nonetheless,  allowed  to  approximately  cool  15  min  to  time.  were  at  necessary  period  of  i t was  ligand  to the  cooling, estimated time.  does s e r v e t o ensure  this.  min  of shaking  after  quantitative.  s a m p l e s were s h a k e n f o r 10 min room  while  a  temperature new  a  this  10  by  Cr recovery i s e s s e n t i a l l y  In u s u a l l a b o r a t o r y runs, then  the  a  completing  although  i n F i g . 3.6.2.3b, by  microwave r e a c t i o n ,  i t was  initial  with  samples  before  b o t t l e s were s h a k e n on t h e s h a k e r that  time,  four at  set of  on  the  samples  bench were  and for  being  processed.  3.7  ANALYTICAL FIGURES OF  3.7.1  Precision The  precision  performing seawater seawater The  replicate sample  matrix  results  of Cr  used  MERIT  the  technique  analysis for  which had  on  this  been  a r e shown i n T a b l e  was  a seawater  purpose  evaluated  by  sample.  The  was  stored acidified 3.7.1.  the at  Nootka pH  2.1.  66 Table  3.7.1:  R e p r o d u c i b i l i t y o f C r d e t e r m i n a t i o n on a seawater sample.  Sample No  The is  3.7.2  1  4.69  2  4.58  3  4.69  4  4.67  5  4.76  6  4.63  Mean  4.67  s t d dev  0.06  % r e l s t d dev  1.31  relative  therefore  Chromium  precision  o f t h e t e c h n i q u e a t 4.67  nM  Cr  1.3%.  Recovery Absolute  spikes  added  recovery studies  of  to  performed  seawater  were  amounts o f t h e two C r s p e c i e s subjecting Two  (nM)  the  replicates  samples  to  Cr(III)  i n t o seawater  the  f o r e a c h sample  both  full  by  and  spiking  samples  extraction  Cr(VI) known  and t h e n  procedure.  were a n a l y z e d and a s shown i n  67  Table  3.7.2,  excellent  recoveries  of  both  species  were  achieved.  Table  3.7.2:  Recovery o f Cr s p i k e s from  Chromium  Cr species added  Total recovd.  Percentage recovery  4 .70±0.08  2.15  Cr(III)  6.62±0.19  97  4 .70±0.08  4.31  Cr(III)  8.99±0.04  100  4 .70±0.08  3.85  Cr(VI)  8.62±0.21  101  4 •70±0.08  7.69  Cr(VI)  12.3±0.03  99  technique  study  (nM)  Spike added  Measures  high  samples  Initial Total  Absolute by  seawater  spikes,  e t al.  although  yields. was  quantitative  That  excellent reduction  recovery  (32), a  i s n o t , as p o i n t e d o u t  requirement  good p r e c i s i o n the recovery  f o r an  i s usually of both  Cr(III)  of  the  associated with  Cr species  shows t h a t e v e n w i t h to  analytical  the case  followed  by  of  i n this Cr(VI)  chelation  was  successful.  3.7.3  Accuracy The  analysis from  accuracy  technique  o f Cr i n t r a c e metal  the N a t i o n a l Research  was  seawater  assessed  reference  C o u n c i l o f Canada.  Two  by  the  standards reference  68  seawater  samples,  (CASS-2)  and  (NASS-3)  were  technique  the  Open  Seawater Reference Seawater  for total  i n this  The r e s u l t s  3.7.3:  Ocean  analyzed  developed  sample).  Table  the Nearshore  CASS-2  2.331 ± 0.068  2.327 ± 0.308  NASS-3  3.333 ± 0.011  3.365 ± 0.192  between  the c e r t i f i e d  reference  m a t e r i a l s and t h e v a l u e s  technique  t o t h e samples  accuracy  percent  respectively. 0.3%; and  was  The r e l a t i v e  The a c c u r a c y ,  precision  values  5.7% f o r CASS-2 a n d NASS-3,  values  f o r the  by a p p l y i n g t h e  sufficient  0.17% a n d -0.95%  the corresponding  3.7.4  obtained  provided  o f t h e method.  error,  f o r each  (nM) Certified  agreement  the  3.7.3.  Found  Good  using  o f C r d e t e r m i n a t i o n on s e a w a t e r  Chromium  the  Cr  Material  (7 r e p l i c a t e s  a r e shown i n T a b l e  Accuracy samples  Reference  dissolved  study  Material  evidence f o r  indicated  f o r CASS-2 obtained  by t h e  and NASS-3, was  2.9% and  f o r the materials  a r e 13.2  respectively.  Limit of detection The  amount  limit of  of detection  analyte  that  can  (LOD) i s d e f i n e d be  detected  as t h e  with  least  reasonable  69  certainty.  The  LOD  was  estimated  of  DI  w a t e r f o r C r ( I I I ) and  on  a  regular  basis  as  by  total  part  of  the  Cr.  the  Cr  thus the  numbers r e p r e s e n t  (at  least  10  r e p l i c a t e s i n each c a s e ) .  and  total  Cr  defined  of  t h e i r b l a n k s were 0.186  3.8  ANALYSIS OF The  method  seawater  samples  3.8.1  Stored Cr  pH  than  approx. 24  hours of  acidifying acidifying frozen.  the a  that  had  acidified  times and  2  with  to  Further  Cr  replicate  sulphite  sample.  pH  the  of  acidified  i n the  is  Cr  in  and  to  acidification.  had  reduced  and agent  for  achieved was  previously  regular state  was  without  (58).  The  simply  by  verified  by  stored  intervals  showed  achieved  i n seawater  longer  been  after  the  acidified  periods  state  This  at  this  acid Cr(III)  2 that  Cr(III)  reducing  deviation  have b e e n s t o r e d  seawater  with  Cr(III)  samples  Cr(III)  analysis  time  respectively.  without  hydrochloric  of  of  for  determination  frozen  to  verification  LOD  standard  stored  Cr(VI)  was  the  the  in  for  standards  over a period The  run  SAMPLES  a l l exists  sample t o  extraction  0.243 nM  been  been s t o r e d  Analysis  a l l the  sodium  applied  LOD  i n seawater samples t h a t  reduction  that  nM  SEAWATER  was  s a m p l e s t h a t had  at  three  analysis  T h e s e b l a n k s were  and  as  the  replicate  about a by  addition samples  day.  running of that  the had  70  been  stored  total that the  acidified.  Cr content. had been  total  Cr(III)  Table  +  The r e s u l t s showed no d i f f e r e n c e i n  Thus,  stored  i n t h e a n a l y s i s o f seawater samples  acidified,  amount o f d i s s o l v e d  t h e C r measured  Cr present  represents  i n t h e sample i . e . ,  Cr(Vl).  3.8.1:  T o t a l C r vs. depth i n the c e n t r a l North A t l a n t i c (BDA s t a t i o n )  Depth  (m)  Total Cr (nM)  19  2.85  38  2.96  56  3.64  77  3.39  121  3.42  171  3.66  299  3.76  640  3.10  1468  3.17  2088  3.09  2463  3.42  3000  3.94  3500  3.33  4000  3.64  71  Chromium (nM) 1  2  3  4  1000  2000 -  Q  3000 -  4000 —  Fig.  3.8.1:  T o t a l Cr vs.depth i n t h ec e n t r a l North A t l a n t i c (BDA s t a t i o n ) ( e a c h p o i n t t h e mean o f two r e p l i c a t e s )  72  Table  3.8.1  shows  samples  obtained  Atlantic  Ocean  3.8.1  which  this  station Total  found  in  does  the  two  from  near  Cr  a l l samples. of  not  total  give  species  seen  can of  distributions  of  other  n u t r i e n t s and  other  trace  The species times  samples  B.C.,  station  in  the  depth p r o f i l e  2.85  3.94  studies  about  at  and  and  the  the  be  these  greater  than  were  a  The  total  by  of  a  more  chromium, with  properties  of  complex  distribution  comparison  chemical  the  proportion  unravelled  the  but  depth  including  metals.  samples collected  off  the  total  Cr.  The  coast  results  p l o t t e d i n Fig.3.8.2  results  nM  ( c r " . (58)),  analyzed.  only  and  and  of  n e a r N o o t k a Sound, were a n a l y z e d  Cr(VI)  in  only  not  species  3.8.2  acidified  i s plotted in Fig.  vs.  i n other  control  Cr  Table  a  in  i s consistent with  which  oceans  frozen  profile  seawater  investigation  Stored  between  the  thorough  Cr(III),  data  information  in  the  different  The  any  in  Island,  This  from  concentration  Cr  chromium  Frozen  depths  concentrations  cycles  3.8.2  concentration  (BDA).  Cr  Cr  Cr  Bermuda.  geochemical  the  total various  shows t h e  distribution but  the  show  that  seawater Cr(III).  Cr(VI) samples  (NTK  for dissolved  are  presented  in  station).  was and  Vancouver  the was  Thermodynamic  dominant roughly  Cr  three  c a l c u l a t i o n s on  73  Chromium (nM) 1 2  F i g . 3.8.2:  3  4  C r ( I I I ) ( 0 ) C r ( V I ) ( * ) and t o t a l Cr( • ) vs. depth i n t i i e Northeast P a c i f i c (NTK s t a t i o n ) (each p o i n t t h e mean o f two r e p l i c a t e s ) r  74  Cr  s p e c i a t i o n i n seawater p r e d i c t t h a t Cr(VI) should  dominant  species  ratio  Cr(VI)/Cr(Ill) predicted  of  approximately between  50  Arhennius  Table  1  pE  found have  The  conditions  is  ratios  experimentally  pointed  out  (nM)  20  0.71  3.29  2.69  22  50  1.17  4.19  3.43  28  100  0.71  3.54  2.86  20  300  1.02  3.66  2.66  28  and  c o p r e c i p i t a t i o n of sulphate. would  proportions  The  of  environments, Cr  kinetic  a l s o be  state  Cr(III)  (nM)  (%)  and  some  i s predicted  M u r r a y e t a l . (48)  and  only,  to  with  hinder  workers  than  m i g h t be  stabilization  expected  Cr(III)  theory  Cr(VI)  Cr(VI)  t o be  this  Cr(VI)  (nM)  contradiction with  (59).  depth  (m)  Cr  of  that  C r ( I I I ) , C r ( V I ) , and t o t a l C r v s . t h e N o r t h e a s t P a c i f i c (NTK station)  Total  the  (49).  Cr(VI)/Cr(III)  been (60)  and  Cr(III)  higher  state.  have  pH  under these  However,  2 0  to  seawater  Depth  hydration the  10 .  3.8.2:  situ  barium  natural  and B o n a t t i  variation in  at  be  have  to  the  strontium  or  of  the  due  Cr(III)  by  oxidation  to  reported  (39).  i n the  C r a n s t o n and  in  Cr(III) Murray  In  higher anoxic  oxidation (53)  have  75  reported these  Cr(VI)  predictions  Saanich  effects  metals  ions,  f o r both  to  of  in  Uncertainties regard  Cr(III)  changes  handling  exist  in  i t s effect  can  reliable  on  results  with  Pacific  and  like  of  the  speciation  still  unclear.  sample  storage  of  trace  the  with metal  C r where t h e o x i d a t i o n s t a t e  relatively  easily.  will  those  be  been  on  performed  Clearly for  in  as  the  samples short  a  most where  time  as  Cr(III)  on  Handling  Since  Cr(VI)  is  acidification  t o pH  important  verify  to  sample  fairly  approx. that  easily  reduced  2 in less  than  this  then  p r e p a r a t i o n f o r the  rest  the  sample  pH of  adjusted the  step. Cr(III)  and  did  from  I t was  not  and  was  result  hours, did  8  to  6  not of  before  performing in this  what  from  i t  was  the  study  Cr(III) to  be  adding solvent  to  originally  unintended  was  occur  T h e s e s a m p l e s had  important  measured  24  determination  approx.  reagents  to  conversion  t h e p r e v i o u s l y f r o z e n samples.  extraction that  consistent  are  speciation  collection.  3.8.2.1  storage  the  i n cases  occur  and  form  possible after  thawed  are  eastern t r o p i c a l  any  have  the  that  samples  determinations  from  the  seawater  especially  during  levels  Inlet.  The of  and  assure in  reduction  the of  Cr(VI). The freshly  verification  was  done  thawed sample a t t h e  by  level  spiking of  38  nM  Cr(VI) and  into  running  a the  76  Cr(III) this  determination procedure  and  a  difference despite levels  a  non-spiked in  the  Cr(VI)  present i n the  C r ( V I ) was  process  samples.  It  Cr(III)  levels  of  contribution  reagents  and  handling  aqueous  contained  a  handling  10  the  times  sample.  however,  in  these  of  showed  no  two  the  samples  natural  T h i s was  proof  Cr  that  Cr(III)  explain  samples  in  these  fact  that  higher  than  the  were  calculations.  Cr  to  the  only  was  extraction  contribution  blank  was  nM  for  standards.  In the  DI  H 0.  of  and  the  separately  from  The  2  checked,  standards  from  blank,  f o r the f i r s t  analysis  signal  determined  standards  routinely  Cr(III)  analyte  from  b a t c h o f r e a g e n t s were u s e d 0.066  results in  each  R e a g e n t and h a n d l i n g b l a n k The  the  The  determination of  p r e d i c t e d by t h e r m o d y n a m i c  3.8.3  replicates  Cr(III)  roughly  not,  found  four  t o C r ( I I I ) d u r i n g t h e p r e p a r a t i o n and  f o r the  does  of  seawater  not reduced  handling  sample.  amount  spike  on  time. nM  samples,  also  reagent  especially  0.326  seawater  which  It  when  and a  averaged  for  Cr(VI)  therefore,  t h e v a l u e s were a d j u s t e d a c c o r d i n g l y .  3.9  DETERMINATIONS AT The  method  applicable total  Cr  to  developed the  SEA in this  determination  study of  (and C r ( V I ) by d i f f e r e n c e )  was  designed  dissolved at sea.  The  to  Cr(III) method  be and has  77  been  applied  i n the laboratory  from p r e v i o u s data  on  workers this  Cr  that  using  cruises,  consistent  techniques.  over  stored  other  noted  perform  elsewhere  trace short  that  seawater  metal  those  The i n h e r e n t  such  samples  and s o f a r h a s y i e l d e d  with  methods,  time  after  Cr e x i s t s and t h a t  in  this  obtained  by  advantage o f  however,  thesis,  determinations sampling  i n both  and  handling  perform  determinations  may  occur,  as  soon  the  on b o a r d  h a s many  Cr(III)  interconversion  storage  is  i t s  ability  ships  species  warrants  the  effort  after  sample  handling.  t o minimize  method w i l l  s o o n be u s e d i n t h e f i e l d .  The  during  possible  and t h e n e e d  a  states i n  of these  as  to  within  advantages.  and C r ( V I )  collection,  3.10  seawater  ability.  As  fairly  are  other  technique  seagoing  fact  oceanographic  on  to  sample The  SUGGESTIONS FOR FURTHER WORK  It  has been s u g g e s t e d t h a t p a r t i c u l a t e C r i n seawater e x i s t s  in  the Cr(III)  extension  state  of the technique  particulate residue  oxidation  Cr.  This  as C r ( 0 H )  i s t o include  would  involve  collected after filtration  for  Cr(III) determination  be  useful  in  providing  3  (48).  A  natural  determination  of  dissolving the Cr(OH)  3  i n a c i d and p r o c e e d i n g as  i n the dissolved state. information  about  g e o c h e m i s t r y o f Cr i n a l l forms i n seawater.  This  the  will  overall  78  There  also  multi-element conditions other.  exists  procedure  study,  possibility  incorporating  f o r one e l e m e n t  In t h i s  (Section  the  of  with those  was e x a m i n e d o n l y  3.3.7) b u t a p p e a r e d  a  C r and A l p r o v i d e d t h e  are compatible  this  developing  feasible  of the  qualitatively  and w a r r a n t s  further  investigation.  3.11  SUMMARY AND CONCLUSIONS An  accurate  determination  has a  ECD-GC  Cr(III)  The method u s e s  seagoing  immediately  rapid  of dissolved  was d e v e l o p e d . and  and  after  ability  which  may  will  during  with  reducing of  fjords  British  technique  to  oxygen  include help  The  storage. of this  of Cr.  found  will  elucidate  oceans.  The t e c h n i q u e  extended  t o multi-element  also  be u s e f u l i n  Of  t o areas  t o have  a great  Such a r e a s i n c l u d e intermittently  i n the coastal  of  extension  the  Cr i n  of Cr i n the  the p o s s i b i l i t y  determinations.  areas  of  particulate  the geochemistry offers  changes  particular  method  and  possible  determination  seawater  (15 mL)  determination  This w i l l  minima  which a r e e a s i l y  Columbia.  allow  i s expected  speciation  pronounced  Cr i n seawater  and o t h e r s p e c i a t i o n  sample  environment  i n f l u e n c e on t h e r e d o x areas  will  be t h e a p p l i c a t i o n  where t h e s e a w a t e r  f o r the  s m a l l sample v o l u m e s  sample c o l l e c t i o n .  occur  importance  and t o t a l  that  reducing possible contamination  technique  of being  79  CHAPTER 4  GALLIUM  4.1  INTRODUCTION  4.1.1  Overview A method  which  uses  f o r the determination  the electron  capture  o f aluminum  detection  of  i n seawater t h e 1,1,1-  trifluoro-2,4-pentanedione derivative  formed a f t e r  was r e c e n t l y d e s c r i b e d  c h a p t e r t h e attempt  adapt  this  seawater  the determination  a n d some s u g g e s t i o n s  of  table  gallium i n  f o r the f a i l u r e are  are put forward.  i s immediately  o f elements  Group  below  aluminum  and i t i s e x p e c t e d  I I I metals  should  i n the periodic  therefore that  have s i m i l a r  chemical  Dissolved gallium concentrations i n the Pacific to  to  Background Gallium  two  to  In t h i s  i s d e s c r i b e d , p o s s i b l e reasons  postulated  4.1.2  technique  (33).  chelation  be 2-30 pM and 20-60 pM  corresponding higher  concentrations  a t 0.06-6.0 nmol/kg  Both these  i n t h e northwest  elements e x i s t  f o r dissolved  and 5-40  nmol/kg,  as hydrolyzed  these  behavior.  are reported  Atlantic. aluminum  The are  respectively.  s p e c i e s i n seawater  80  and  similar  factors  may  be  responsible  f o r their  vertical  distributions (61). A shipboard seawater  which  pentanedione The  uses  utilizes  metal  control  which  especially materials  the high  sensitivity  chelates  and  i s critical  must  with  The c h i e f form  high  was  possibility  of  adapting  this  study ECD-GC  solution  and t h a t  technique  would a l l o w f o r t h e e l u c i d a t i o n  us t h e p o s s i b i l i t y  chemistry  with  that  of  phase.  t o investigate the  was r e a s o n e d ,  giving  f o r a comparison  e l e m e n t method f o r t h e two e l e m e n t s .  to  the  Such a t e c h n i q u e , i t of the factors  i n seawater  aluminum,  i n crustal  volatile  o f g a l l i u m i n seawater.  for i t s distribution  metals  stable,  determination  responsible  small  i s t h a t t h e elements  i n aqueous  of this  of  trace  n a t u r a l abundance  a suitable organic  t h e purpose  electron  contamination  with  chromatographically  be e x t r a c t a b l e i n t o It  dealing  limitation  efficiency  of  f o r the use  a t s e a improve  when  (33).  reported  (ECD-GC) f o r f l u o r i n a t e d  allows  A l due t o i t s h i g h  question  1,1,1-trifluoro-2,4-  has been  Determinations  (8.2%).  o f aluminum i n  t h e metal  chelates  sample v o l u m e s .  these  ligand  d e t e c t o r gas chromatography  volatile  in  the  to chelate  technique  capture  method f o r t h e d e t e r m i n a t i o n  as  well  as  of i t s oceanic  preferably  in a  multi-  81 4.2  EXPERIMENTAL  4.2.1  Gas  chromatography  4.2.1.1 Column  The had  DB  210  been u s e d  capillary  column  f o r ECD-GC work on  good s e p a r a t i o n  f o r Cr  in this  The  peaks  were  Al  resolve  and them  variety  of  Scientific thickness  tfa  by  5  m  W  Scientific)  (32),  Al  thesis failed  the  x  best  Be  &  unresolved  columns 15  gave t h e  GC  0.25  o.d.  gave Ga.  attempts  to  conditions.  A  investigated;  mm  and  t o work f o r  despite  operating  were  (33),  which  with  a  J  &  0.25-/im  W  film  results.  conditions  GC  conditions  complex a r e  Table  changing  other DB  4.2.1.2 GC The  Ga  (J  4.2.1.2:  for  presented  analysis  i n Table  of  gallium  as  the  4.2.1.2  Gas c h r o m a t o g r a p h i c c o n d i t i o n s f o r t h e a n a l y s i s o f g a l l i u m as t r i s - ( 1 , 1 , 1 trifluoro-2,4pentanediono) gallium(III)  Injection port Oven  the  temperature  temperature  Detector  temperature  Column h e a d  Nitrogen  gas  makeup gas  °C  140  °C  300  °C  15  pressure  Hydrogen c a r r i e r  200  flow flow  2.6 52  psi mL/min mL/min  82  4.2.2  Synthesis  of tris-(l,l.1-trifluoro-2,4pentanediono)  qallium(III) The  standard.  procedure  followed  trifluoroacetylacetonate e t al.(62)  Wold  Gallium  in  water  mL  of  pentanedione NH OH  DI  (5.78 g,  slowly  4  with  approximately from  ethyl  product  (III) nitrate was  added  The  which  analysis  4.2.3  Organic  g  (65%).  solution  gallium  1,1, l - t r i f l u o r o - 2 , 4 -  white  of  concentrated  precipitate  funnel  and r i n s e d  which  several  o f the white  I t had  a  i s 128.5-129.5 ° C ( 2 ) ) . mass  spectra  crystalline  melting  point value  and C  twice  point  of  f o rthe trans The compound  and H  elemental  standards Ga(tfa)  f o r the  chelate  3  optimization  was u s e d  t o make t h e GC  procedures.  The  stock  was made b y d i s s o l v i n g 0.022 g o f t h e c h e l a t e i n  mL x  by  Ga  purified  standards  4.67  the  data.  The  47.12  of  i t was r e c r y s t a l l i z e d  The y i e l d  isomer o f t h i s c h e l a t e characterized  from  (2.86 g, 11.2 mmol)  i n 7 mL  128-130 ° C ( t h e l i t e r a t u r e m e l t i n g  was  adapted  gallium  I t was d r i e d i n t h e o v e n a t 60 ° C f o r  acetate. 3.850  to  37.5 mmol)  2 hr after  was  of  f o r the synthesis  on a b u c h n e r  DI w a t e r .  was  3  shaking.  f o r m e d was c o l l e c t e d times with  (Ga(tfa) )  description  acetylacetonate. 25  f o r the synthesis  of purified  10~  4  g/mL  toluene  Ga(tfa) . 3  giving The  a  solution  actual  containing  concentration  of  83  gallium  i n this  standards from  solution  was 6.10 x 1 0 ~  c o n t a i n i n g lower  this  primary  5  g/mL.  Appropriate  g a l l i u m c o n c e n t r a t i o n s were made  standard  by  serial  dilution  with  the  toluene solvent.  4.2.4  Solvent  extraction  A 10 ppb g a l l i u m s t a n d a r d was  used  i n an a t t e m p t  chelation  of  investigated. adjustments addition  with  of ligand  rinsed with  analyzed.  t o determine Various  1  M  NaAc/HAc  and s o l v e n t  shaker. 1 M NaOH  t h e optimum samples  The s o l v e n t e x t r a c t i o n  the mechanical and  gallium.  made up i n a s e a w a t e r  with  pH f o r t h e  volumes  procedure  buffer,  were  i n v o l v e d pH  followed  subsequent  The o r g a n i c l a y e r was t h e n solution  matrix  by t h e  shaking  on  separated  a n d DI w a t e r b e f o r e  being  84 4.3  RESULTS AND  DISCUSSION  4.3.1  Characterization  of  tris-(l.l.l-trifluoro-2,4-  pentanediono) a a l l i u m ( I I I ) The  purified  Ga(tfa)  3  was  standard  characterized  by t h e r e s u l t s  o f C a n d H e l e m e n t a l a n a l y s i s a n d mass s p e c t r o m e t r y  4.3.1.1 Mass The Ga(tfa)  3  spectra  results chelate  T a b l e 4.3.1.1:  The  mass  formation  of  the  mass  are presented  spectral  analysis  f o r the  i n T a b l e 4.3.1.1.  Fragmentation ions of t r i s - ( 1 , 1 , 1 trifluoro-2,4-pentanediono)-gallium(III)  F r a g m e n t mass (m/z)  Intensity (% b a s e p e a k )  530  2.2  7 1  528  3.0  6 9  377  68.4  375  100.0  6 9  71  2.7  7  69  4.9  69 a+  43  72.6  CH C0  spectrum of  data.  the  (Fig.  4.3.1.1)  Ga(tfa)  3  Assignment  7 1  Ga(tfa)  3  Ga(tfa)  3  Ga(tfa)  2  +  +  +  (tfa) + 2  lGa+ G  +  3  provided  chelate  and  evidence the  f o r the splitting  85  II  7» (f If 4f 1* 2*  +* -H M  c © c  If  *  ^ T"  'i  iff  tlf  i  I  I  |  I  I  l  1 ( 1 1 1 1  T  4M  4 If  Iff  M •f 7f tf If 4f  31 If  it  1* •  iff  F i g . 4.3.1.1  r  'I  1  I  I  I  I  I  I  I I  I  I  IM  tff  Mass spectrum o f t r i s - ( 1 , 1 , 1 - t r i f l u o r o - 2 A pentanedione)-gallium(lii) ' " t  r  i  r  A  u  o  r  o  2  4  86  p a t t e r n o f t h e compound. a relative A  intensity  smaller  peak  corresponds the of  7 1  Ga  375; m/z  with  of  also 377  3.0%  the seen  and  The  530  intensities  of  base  peak  relative 2.7%  corresponds  to  (relative  peak from  i s the the  4.9%  68.4%  .  6 9  528  of  the  i o n and 7 1  Peaks w i t h  correspond  to  7 1  Ga  +  .  from loss  has  Ga(tfa)  + 3  2.2%)  i o n formed  result  to  had  Ga(tfa)  intensity  parent  corresponding  intensity and  i o n w i t h m/z  chelate molecular  t f a moieties is a  molecular and  m/z  to gallium-tfa  isotope.  one  of  The  m/z with  + 2  relative  and  6 9  Ga  +  respectively.  3.1.2  Elemental Results  additional  analysis  of  C  and  H  elemental  evidence  for  the  formation  analysis of  provided  Ga(tfa)  (Table  3  4.3.1.2). T a b l e 4.3.1.2:  Elemental a n a l y s i s data f o r t r i s - ( 1 , 1 , 1 trifluoro-2,4-pentanediono)-gallium(III)  Ga(tfa)  3  4.3.2  Chromatograms  Figure  4.3.2  Ga(tfa)  3  shows  chelate  the from:  %  C  Calcd.  34.03  2.27  found  3 3.88  2.26  chromatograms (a)  the  H  obtained  synthesized  for  the  Ga(tfa)  3  87  1  .Ze-4-  1 . 1  1  •  .0«-4  ^ O O O X EH  •  M W  eooo  w  7000-  55  EH  o  •i  M  J  4ooo -  Ok  o  G>  —  s  i «ooo3  TIME ( m i n )  Fig.  4.3.2(a)  Chromatogram o f s y n t h e s i z e d Ga(tfa) s t a n d a r d ( p e a k r e t e n t i o n t i m e s ( m i n ) : Ga, 1.440; I n t e r n a l s t a n d a r d , 3.015) 3  88  TIME ( m i n )  Chromatogram o f G a ( t f a ) from an e x t r a c t i o n s t a n d a r d (peak r e t e n t i o n t i m e s ( m i n ) : A l , 1.123; Ga, 1.488; I n t e r n a l s t a n d a r d , 3.094) 3  89  Fig.  4.3.2(c):  Chromatogram o f G a ( t f a ) from a seawater sample (peak r e t e n t i o n t i m e s ( m i n ) : A l , 1.115; G a , 1.475; I n t e r n a l s t a n d a r d , 3.087) 3  90  standard, from The  a  (b)  seawater  internal  time  of is  1.12  min.  4.3.3  ppb  a  sample.  min  extraction Ga(tfa)  under  peak  ECD  standard  elutes  3  for  the  GC  Al(tfa)  with  3  a  study.  detector  response  The  was  not  only  for  Al(tfa) That few  confirmed  3  remarkably chelate  days  when  also  very  retention  here,  also  time  very early  f o r the G a ( t f a ) compared  varied  detector  fresh daily attempt with  amount o f g a l l i u m detector  to  of  greatly  on  in  chelate  3  the  response  from  i n the  of  the  freezer  over  to  a  single  a l s o showed v a r i a t i o n to  regard  optimize to  pH  was  r e c o v e r e d was  c h e l a t e c o u l d n o t be  temperatures  response  response  response  the also  day  to  (-15  °C)  was  ECD  to  one  a  period  Ga  standard  f r o m day  solvent  of  to  day.  extraction  unsuccessful.  The  impossible to quantify  since  characteristics  for  the  Ga(tfa)  3  determined.  a v e r a g e , a 10 ppb  amount d e t e c t a b l e  low  the  standard stored  prepared  On  at  monitoring  The  conditions  low  but  even  time.  The  min.  t h e s e o r g a n i c s t a n d a r d s were u n s t a b l e on s t o r a g e  by  particular  used  Ga  sensitivity were e n c o u n t e r e d  a  (c)  1.46  retention  problems  day.  and  after  conditions  Sensitivity this  the  Ga  s t a n d a r d ( 2 , 6 - d i c h l o r o b i p h e n y l ) has a  3.08  seen  for  100  even  Ga  s t a n d a r d seemed t o be t h e  with the changing  To o b t a i n a r e a s o n a b l e s i g n a l  detector  f r o m an a c t u a l  least  response.  seawater  sample  91  (with  Ga  concentration  (250-500  mL)  were  of  2-60  required  pM) , l a r g e  and  even  seawater  then  the  volumes  results  were  irreproducible.  4.3.4  Discussion  The  fact  that  Ga(tfa)  was  3  synthesized,  successfully  c h a r a c t e r i z e d suggests  least  in i t s natural  In  stable  solution,  stability detector toluene  however,  after  a  response varied  standard  was  results  were  problem  might from  day  detector  would  be  the  chelates  just  a b o v e Ga  also  to  synthesized  behavior The Ga(tfa)  3  in  other  foregoing  experiences  during  analysis  If to  behave  metals,  decomposition  characteristics.  in  of  so,  its  conclusion  poor  Thermal  the  then  the  way  for  which  and  3  is was  experienced. that  either  and/or t h a t  gas  and  the  chromatographic  p r o b l e m s were  in  the  detector  similar Al  in  same  that  the  were  storage  the  analyzed,  However, A l ( t f a )  and  the  why  made up  argue  a  its  When t h e  can  in  i s at  loose  explains  especially  study  to  to  and  this  and  temperature.  standard  3  day  One  i n s o l u t i o n on  resulting  room  storage.  each  similar  leads  i s unstable  on  chelate  seems  periodic table. this  at  instability  day.  i n v e s t i g a t e d : no  chelate  response  the  the  perhaps  better.  expected  i n the  day  freshly  in  of  chelate which  to  much  lie  form  single Ga(tfa)  day  prepared not  the days  for a  from  response  tfa  few  solid  that  purified  the  chromatograph irreproducible chromatographic  92  stabilities  a r e mandatory  have  analytical  any  comprehensive complexes In(III), been  Uden  Sc(III),  gas  et  have  infact  shown  been  degradation trace  high  al.  (5)  below  analysis  Zr(lV),  sample  ECD  has  chromatographic Burgett the  and  with  100-ng  to  the  but  detection  chromatography When t r a c e  have b e e n s u c c e s s f u l  on-column suitable  of  Fe(III),  and  crucial  metal  complex  detector  total  show  was  and  limits  a  not  species  saturation  i n this  function the  rather  from s i m i l a r than  and u l t r a - t r a c e  of the of  at of  GC the  complexes  (such as  was  problems o f  poor  level  by  instance  ability  a r e n o t good  suffer  f o r the  disappearance  It i s clear  limit  test  I t i s possible that other  3  sensitivity.  has  2  not  chelates  a  observed  species  it.  as  a  level.  the case here f o r G a ( t f a ) ) inadequate  elute  Cu(tfa)  decomposition  the  detection  detectors to detect f o r w h i c h t h e ECD  of  (64) who  complex  to  of  below microgram l e v e l s ( 2 ) .  employed  below t h i s  the observed  elute  some  stability  level  detectability that  been  Fritz  level.  Htfa  having  evidence  i s therefore  The  Ga(III),  considerable  and  metal  though  proved  a  and Z n ( I I ) a r e a l l n o t e d t o e l u t e a t  considerable deterioration The  been  in  of of  apparent  undergo  (63).  levels  no  yet  level  Hf(lV)  and C u ( l l ) ,  with  i s to  noted  t f a complexes  the microgram  to  this  As  chromatography  Rh(lll),  not  a t below  Mn(III),  gas  V(IV),  quantitatively  for  on  chromatographed  decomposition,  of metal chelates  applications.  review  by  i f t h e GC  detector  applications  and t h e r e f o r e t h e c h r o m a t o g r a p h y i s n o t  93  suspect,  the  consistently This  would  source as  appear  whether  complexes  the  While  ECD  have  f o r pure  t h e ECD  sensitivity  is still  capturing  pseudo-aromatic  some  and s h o u l d  complexes give  good  of  or the  (5), i t i s clear  a r e good  electron-  detection  limits i f  their  ECD-GC  study  of  the determination  of  q u a n t i t i e s o f aluminum a n d chromium i n u r a n i u m u s i n g ligand,  Genty  sensitivities  et  a l .  orders  gallium  (  7 2  (29)  the detector's  o f magnitude  Ga, T  major p a r t  1 / / 2  lower.  difficulties radioactive was  while only  were copper  quantitative  parts  similarly but that  ECD order  f o r Ga was  t o show  ( i n j e c t i o n p o r t and  f r a c t i o n was e l u t e d ;  differences for  showed copper  that  i n t o the apparatus  components  encountered  the  By t h e u s e o f r a d i o a c t i v e  a small  the s e n s i t i v i t y  trace  H t f a as  t h e same  sensitivity  o f t h e compound i n t r o d u c e d  column m a i n l y ) , explain  that  ~ 14.1 h r ) , t h e y were a b l e  r e m a i n e d f i x e d on i t s v a r i o u s  could  observed  f o r A l , C r a n d Be were w i t h i n  magnitude b u t t h a t  three  the  these  GC c h a r a c t e r i s t i c s a r e a d e q u a t e . In  of  as t h e  uncertainty  ability  rings  been  complexes.  the f l u o r i n a t i o n , the metal  a l lof the fluorinated species  the  range  there  electron  from  of several  capturing  of  t o exonerate  the  arises  presence  limits  i n t h e low p i c o g r a m  o f problems.  to  that  detection  noticed.  copper,  that  the  solvent  was  trapped  this  Similar use  of  extraction in  various  o f t h e GC. The  fairly  fact  that  similar  two  metals,  chemical  A l and  behavior  Ga,  should  which  display  behave  so  94  differently  as  tfa  chelates  in  the  gas  chromatograph  s u g g e s t s a d e p e n d e n c e o f t h e c h e l a t e p r o p e r t i e s on t h e ion.  The  complexes rare  dependence on  the  much  case,  more  Possible  can  than  for  molecules.  tendency  enhance  the  ionic  to  form  volatility  the  the  radii  of the  or  A l l of  in  complex  the  local  become  more  attractive  B-diketonate  radii.  trend  i o n , and  size  were  forces also  these with  of  have  a  factors  a  smaller  step  towards  radius.  suggestion put  forward  v a r i o u s components o f t h e GC continuous  however, t h i s high  size  the  (66).  ionic  s m a l l e r c o m p l e x may  as  s o l v i n g the problems of decomposition  a  large  metal  in  for  e a r t h metals  The  oligomers.  of  noted  size-related  the  from The  with  (65).  decrease  B-diketonate  smaller ionic  the  r a d i u s of  shielded  reduced  One  those  of  i o n was  alkaline  complexes w i t h  either  effectively neighboring  the  metal  the  h a v e been a d v a n c e d with  volatility  the  and  explanations  decreases dipole  the  the  of  (65)  volatile  volatility  metal  size  earth metals  In e i t h e r  of  metal  level  of  sensitivity  of the c h e l a t e s i n the  i s t o dope t h e c a r r i e r  ligand  does not appear  a possible  vapor feasible  (5).  At  f o r the  to  fluorinated  ligands;  the  w o u l d most c e r t a i n l y  contaminate  the d e t e c t o r .  gas  the ECD  with  moment  with i t s  excess  ligand  95  4.3.5  Summary  The  attempt  determination the  metal  chelate  of  with  was  problems  be  Htfa  experienced  was  the  and s u f f e r e d fact  that  with  B-diketone  which  through  which  3  The  has  ligands  with  will  i n t h e gas none  a  already  One p o s s i b l e  of the  metal  ion  been  noted  solution  would  a g r e a t e r degree result  of  gallium-tfa  shows  suggests  3  f o r the  chelation  decomposition  Al(tfa)  Ga(tfa)  hopefully  of the chelate.  technique  unsuccessful.  i n the other groups.  fluorination  ECD-GC  i n seawater  relationship  to t r y other  volatility  use  gallium  The  size-volatility metals  to  unstable  chromatograph.  for  and c o n c l u s i o n s  i n  of  greater  96  REFERENCES  1.  L e d e r e r , M., Nature,  176, 462, ( 1 9 5 5 ) .  2.  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R., A n a l . Chem., 2 6 ( 3 ) , 546, ( 1 9 5 4 ) .  63.  B e l c h e r , R., M a r t i n , R. J . , S t e p h e n , W. I . , H e n d e r s o n , D. E . , K a m a l i z a d , A., Uden, P. C., A n a l . Chem., 45, 1197, (1973).  64.  B u r g e t t , C. A., F r i t z , (1972).  65.  S i c r e , J . E . , D u b o i s , J . T., E i s e n t r a u t , K. J . , S i e v e r s , R. E . , J . Am. Chem. Soc, 91, 3476, ( 1 9 6 9 ) .  66.  S c h w a r b e r g , J . E . , S i e v e r s , R. E . , M o s h i e r , A n a l . Chem., 42, 1828, ( 1 9 7 0 ) .  J . S., A n a l . Chem., 44, 1738,  R.  W.,  100  APPENDIX I  TOTAL'ABUNDANCE" 0.99939 AVCRAiE MASSSll.239700 MOST A8IJN0ANT PEAK510.939557 N0M MASS 50S. 510. 511. 512. 513. 514. 515.  Fig.  5.10(a):  EXACT  MASS  509.995095 509.998385 510.989557 511.991749 512.991829 513.994011 514.995115  INTENSITY 5.19_ 0.S9 100.00 28.59 7.41 1.04 0.11  Theoretical  intensity  patterns  for Cr(tfaf  patterns  for  3  TOTAL A2UN0ANC E» 0.9994S AVESA^E MASS* 3S3.1S8467 MOST 4BUN0AMT PEAK357.971:15 NOM  MASS 355. 357. 358. 359. 360. 361. 362.  Fig.  5.10(b):  EXACT  MASS  3S5.978742 355.982097 357.973215 358.974960 359.974549 360.976759 361.977584  INTENSITY S.19 0.58 100.00 22.85. 5.55 0.57 0.05  Theoretical  intensity  Cr(tfa)o  +  101  APPENDIX I I  TOTAL ABUNDANCE" 0.99977 AVERAGE MASS" 528.966294 MOST A8UN0ANT P E A K 527.974600 MASS 523. 529. 530. 531 . 532. 533. 534.  Fig.  EXACT  MASS  INTEN!  527. 9 7 4 6 0 0 100. .00 17 .27 528 . 9 7 7 9 7 0 68 .34 529. 973898 1 1.71 530. 9 7 7 2 4 5 1 .75 531 . 9 7 9 3 9 7 532 .,981972 0 .18 0 .01 533. .984688  5.20(a):  Theoretical  intensity  patterns  f o r Ga(tfa) +  patterns  for Ga(tfa)  3  TOTAL ABUNDANCE0.99967 AVERAGE MASS375.83*303 MOST ABUNOANT P E A K 374.953257 NOM MASS 375 .• • 376. 377. 378. 379. 330.  Fig.  5.20(b):  EXACT MASS 374 . 9S82S7 375 . 9 6 1 6 4 4 376.957470 377.960843 378.962626 379.964990  INTENSITY 100.«f0 U.Sl" 67.64* 7.7l" 0.93* 0.06  Theoretical  intensity  + 2  

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