High-performance liquid chromatographic method for the simultaneous determination of mefloquine and its carboxylic metabolite in 100-microliters capillary blood samples dried on paper.

A reversed-phase high-performance liquid chromatographic method is described for the analysis of mefloquine and its carboxylic metabolite in 100-microliters capillary blood spots dried on chromatographic paper. Each spot was cut into small pieces, and mefloquine and its metabolite were eluted with an ammonia-water solution (10:90, v/v). The compounds were extracted simultaneously after alkalization at pH 9.5 using tetrabutylammonium as ion-pairing agent and then separated on a C18 column with ultraviolet detection at 227 nm. The recovery of the drugs from spiked blood applied to paper and dried was 70-80%, and the inter-assay precision at 1.0-5.0 mumol/l (therapeutic range) was less than 10%. The correlation between extractions from venous whole blood and capillary blood applied to chromatographic paper was more than 0.94. The analytes were stable in dried blood spots for at least fifty days at -20 degrees C. The decrease of concentration was less than 10%, when the paper was stored at 37 degrees C for fifty days. The assay is reliable and easy to use for therapeutic monitoring of mefloquine with a lower limit of determination of 0.3-0.5 mumol/l.