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UBC Theses and Dissertations

The development of a technique for the determination of disolved chromium(III) and total dissolved chromium in seawater by electron capture detection gas chromatography Mugo, Robert K.


A gas chromatographic method for the determination of dissolved Cr(III) and total dissolved Cr in seawater was developed. The technique uses the electron capture detection of the 1,1,1-trifluoro-2,4-pentanedione (Htfa) derivative of Cr(III), Cr(tfa)₃, which was prepared from solvent extraction of a 15-mL seawater sample. The method was applied to stored acidified samples for the determination of total Cr and to stored, frozen, unacidified samples for the determination of Cr(III) and, after reduction, total Cr (with Cr(VI) being obtained as the difference of these two). The accuracy of the technique was assessed by the analysis of standard reference materials from the National Research Council of Canada. The Cr values obtained for the reference materials using this method were in good agreement with the certified values. The technique has a precision of 1.3% at 4.67 nM with detection limits (3 σn-₁) for Cr(III) and total Cr of 0.186 and 0.243 nM in the original seawater, respectively. The method is designed to be applied to the determination of Cr in seawater samples immediately after collection onboard ship during oceanographic cruises. The attempt to extend the technique to the determination of gallium in seawater was not successful due to thermal instability and/or insufficient volatility of the Ga(tfa)₃ chelate.

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