Chiral Analysis of Organophosphorus Nerve Agents by Formation of Diastereomers Followed by LC-MS\MS Analysis

Dan Loewenthal, Analytical Chemistry, Israel Institute for Biological Research, Ness Ziona, Israel (danl.l@iibr.gov.il)
Avi Weissberg, Analytical Chemistry, Israel Institute For Biological Research, Ness Ziona, Israel
Shai Dagan, Analytical Chemistry, Israel Institute For Biological Research, Ness Ziona, Israel

We present a simple technique for the chiral analysis of organophsophorus nerve agents in water and blood samples. Our technique can be implemented in standard reverse phase LC-MS operating conditions relieving the user of the specialized operating conditions frequently demanded in chiral LC-MS analysis. The technique consists of formation of diastereomers by a rapid reaction with (R)-2-(1 aminoethyl) phenol, followed by LC-MS\MS analysis. Reaction regioselectivity was examined by comparison to reaction with a tBoc protected reagent proving formation of diastereomers via binding to the hydroxyl group on the reagent. Reaction enantioselectivity was examined by comparison to reaction with optically pure sarin proving no enantiomeric preference in the reaction as well as the enantiomeric discrimination abilities of the technique. Enantioselective sarin elimination pathways were probed by following the elimination kinetics of the two sarin enantiomers as well as IMPA in whole blood, plasma and TDW. Sarin enantiomers showed marked differences in elimination of the (-) enantiomer in whole blood and plasma. We found that small amounts of acetonitrile in plasma cancel the rapid elimination of the (+) enantiomer causing both enantiomers to eliminate in similar kinetics. We found no pronounced increase in IMPA levels along the elimination of sarin in whole blood and plasma suggesting that protein binding is more prevalent than hydrolysis during the fast elimination of sarin in the blood.