Determination of fluvastatin enantiomers and the racemate in human blood plasma by liquid chromatography and fluorometric detection

Liquid chromatographic methods for the determination of fluvastatin, as racemate and as separated enantiomers, are described. Fluvastatin was extracted at pH 6.0 from blood plasma into methyl tert-butyl ether. The organic phase was evaporated and the extract redissolved into either a phosphate buffer solution of pH 6.0 containing tetrabutylammonium fluoride and methanol for the racemate determination, or in a mixture of acetonitrile and water for assaying the enantiomers. The absolute recoveries were 95 and 86% for the racemate and the enantiomers, respectively, and the limit of quantitation 0.5 nmol/l for the racemate, and 5 nmol/l for the enantiomers, when using half a millilitre of plasma sample. The samples were chromatographed on a C-8 column (racemate) and on a Chiralcel OD-R column (enantiomers), and monitored using fluorescence detection. In the achiral system, post-column exposure of the eluate to UV light enhanced the sensitivity by 4 to 5 times when compared with analysis based on the native fluorescence.