QUANTITATION OF L-CARNITINE, ACETYL-L-CARNITINE, PROPIONYL-L-CARNITINE AND THEIR DEUTERATED ANALOGS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY TANDEM MASS-SPECTROMETRY

A new simple and sensitive high-performance liquid chromatographic pro cedure with tandem mass spectrometry detection (HPLC/MS/MS), to determ ine L-carnitine (LC), D-3-L-carnitine (D-3-LC), acetyl-L-carnitine (AL C), acetyl-D-3-L-carnitine (D-3-ALC), propionyl-L-carnitine (PLC) and propionyl-D-3-L-carnitine (D-3-PLC) in plasma, was developed. Sample p reparation consisted of only deproteinization of plasma samples with a mixture of acetone-methanol before injection in HPLC. The detection w as achieved by multiple reaction monitoring. A chloro-derivative of L- carnitine was used as internal standard. The limits of detection, calc ulated for a S/N ratio similar to 3, were 1 nmol/mL for LC and D-3-LC, and 0.1 nmol/mL for ALC, D-3-ALC, PLC and D-3-PLC. The limits of quan titation were 5 nmol/mL for LC and D-3-LC, 1 nmol/mL for ALC and D-3-A LC, and 0.25 nmol/mL for PLC and D-3-PLC. The recovery of the procedur e was in the range 80-96% for the six analytes, 88.2% for the internal standard. Validation was performed within the following concentration ranges: 5-160 nmol/mL for LC and D-3-LC, 1-32 nmol/mL for ALC and D-3 -ALC, and 0.25-8 nmol/mL for PLC and D-3-PLC. Linearity was assessed d uring both intraday and interday sessions, and coefficients of regress ion were always higher than 0.99. Precision and accuracy were in the r anges 0.38-5.5% and 0.01-3.92%, respectively. The method is suitable f or the quantitation of the three endogenous carnitines and their deute rated homologues in plasma in a single analysis. (C) 1998 John Wiley & Sons, Ltd.