Some technical aspects of enantioselective high-performance liquid chromatography tandem mass spectrometry

Author: Saba Jorbenadze
Keywords: Enantioseparation, HPLC/MS/MS, Pharmaceutical Drugs, Chemical Expertise
Annotation:

Since the number of chiral illicit drugs grows steadily the role of enantioselective analysis in forensic toxicology becomes increasingly important. Enantioselective high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) meets current requirements in this field more or less adequately and has the potential to assist in determination of cause of death and aid in the correct interpretation of substance abuse. As our experience shows there are some technical issues the scientists have to consider in order to correctly perform enantioselective HPLC-MS/MS experiment and to interpret experimental results adequately. This presentation summarizes some of our observations on this regard. The enantiomers of over 100 chiral substances were separated on various polysaccharide-based chiral columns in HPLC and detected with serially connected UV-VIS and MS/MS detectors. The effect of a chemistry of a chiral selector, mobile phase composition, sample solvent and sample concentration on the peak shape, separation efficiency and ratio of response to both enantiomers was evaluated. It was found that mobile phase gradient (composition and especially the flow-rate), as well as sample concentration may drastically affect peak shape and ratio of response of MS detector to two enantiomers of a given chiral compound. Optimization of collision energy can provide a solution of this issue in a certain degree. Exactly the same response to both enantiomers of a given chiral compound is not warranted with MS-detector. Experimental conditions, especially mobile phase composition and flow rate has to be carefully optimized in order to reduce the effect of these factors on peak shape and ratio of MS-detector response of two enantiomers. For quantitative analysis independent calibration has to be performed for both enantiomers. In addition, the same response cannot be a priori assumed for non-deuterated and deuterated compounds.