High-performance liquid chromatographic determination of (SR)- and (RS)-enantiomers of mefloquine in plasma and capillary blood sampled on paper after derivatization with (-)-1-(9-fluorenyl)ethyl chloroformate.

A sensitive, stereoselective and rapid reversed-phase liquid chromatographic method for the determination of (SR)- and (RS)-mefloquine enantiomers in 100 microliters plasma and capillary blood collected on chromatographic paper is presented. The assay involves protein precipitation from plasma, liquid-liquid extraction of mefloquine from plasma, capillary blood with methyl tert.-butyl ether under alkaline conditions and derivatization of MQ with (-)-1-(9-fluorenyl)ethyl chloroformate. Liquid chromatographic separation of the diastereomers was performed using an C18 reversed-phase column with acetonitrile-water-acetic acid 82:18:0.07 (v/v/v) as the mobile phase, and a flow-rate of 1.0 ml/min. When using 100 microliters of plasma the limit of determination is 250 nmol/l with ultraviolet- and 10 nmol/l with fluorescence detection. The present method offers several advantages over those previously reported; very low limit of determination, small sample volume, sampling onto paper and use of an inexpensive standard achiral HPLC column. No racemization during the derivatization procedure or storage of the MQ enantiomers was found.