High-performance liquid chromatographic method for the determination of quinine and 3-hydroxyquinine in blood samples dried on filter paper

A simple high-performance liquid chromatographic method for the simultaneous analysis of quinine and 3-hydroxyquinine in blood samples dried on filter paper is described. Sample preparation involves liquid–liquid extraction with toluene–butanol 75:25 (v/v) followed by evaporation. A reversed-phase liquid chromatography system with fluorescence detection was used. The limit of determination was 10 nM for both quinine and 3-hydroxyquinine and the recovery varied between 78 and 109%. The within- and between-assay coefficients of variation varied between 2–5% and 4–10%, respectively. No loss of either analyte occurred after storage for 2 months at room temperature or at 37 °C. This method for sampling has advantages that make it of great value for clinical and pharmacokinetic studies especially in remote regions where storage and transportation is problematic.