UBC Theses and Dissertations
Capillary electrophoresis-mass spectrometry separation of isomeric biological compounds Soliman, Laiel
Current prostate cancer (PCa) diagnosis based on prostate-specific antigen (PSA) has been gradually losing its credibility over the last decade due to contradictory results in published literature and clinical practice. Recently, a group of potential PCa biomarkers in urine, particularly sarcosine, was found to increase significantly as the cancer progressed to metastasis. In Chapter 2, we report a simple, robust, and reproducible capillary electrophoresis–electrospray ionization–tandem mass spectrometry (CE–ESI-MS/MS) method for the determination of sarcosine and other representative potential biomarkers in pooled urine. A solid phase extraction (SPE) technique was optimized for maximum recovery of sarcosine. With no derivatization step, excellent resolution between sarcosine and its isomers (α-alanine and β-alanine) was achieved. A separate non-SPE method was also developed for quantitative determination of highly concentrated urinary metabolites. Precision for intra- and inter-day standard addition calibration of sarcosine were found to be within 15%, whereas intra-day precisions for the rest of the metabolites varied from 0.03 to 13.4%. Acceptable intra-day and inter-day accuracies, ranging from 80 to 124%, were obtained for sarcosine and the other metabolites. The second part of the thesis takes on a more challenging task. The importance of chiral separation in pharmaceutical, agriculture, and food industries has driven separation scientists to develop more powerful methodologies in conjunction with the structural capabilities of mass spectrometry. In Chapter 3, chiral separation of D- and L-tryptophan was compared on a bare-fused silica capillary and a PEI-coated capillary. Although a higher resolution was observed for uncoated capillaries, analytes were found to migrate slower resulting to longer analysis times (tm > 20 min). With shorter migration times (tm < 10 min) and acceptable resolution, further investigations on different factors that could affect enantioseparation were conducted on a coated capillary. Highly-sulfated cyclodextrins (HS-CDs), a group of charged CD derivatives, were also utilized for the separation of several racemic amino acids. Resolution with HS-CDs was found to be superior to using native CDs. Unfortunately, due to time constraint, no MS work was presented as the chiral CE/MS work is still currently in progress.
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