Stereoselective quantitation of a serine protease inhibitor using LC-MS/MS at elevated column temperature

A LC-MS/MS method using a LC column packed with sub-2 micron particles and elevated column temperatures was validated for the quantitation of SCH 503034 diastereomers (SCH 534128 and SCH 534129) in human plasma. The method was validated over the concentration range of 2.5 to 1250 ng/mL. Inter-assay precision, based on percent relative deviation for n = 18 replicate quality controls, was 4.5% for SCH 534128 and 4.9% for SCH 534129. Inter-assay accuracy based on n = 18 replicate quality controls was ±7.8% for both SCH 534128 and SCH 534129. The method involved the novel application of ion pairing reagents to increase the stereoselectivity of the separation. Temperature, types of ion pairing reagent, and concentration of ion pairing reagent were all found to play significant roles in the resolution of the SCH 534128 and SCH 534129 diastereomers on a LC column packed with sub-2 micron particles. Specifically, a sensitivity increase of five-fold was demonstrated by increasing the column temperature. Without sacrificing resolution, the run time was significantly shortened when the column temperature was elevated to 100°C.