Automatic solid-phase extraction and high-performance liquid chromatographic determination of quinidine in plasma.

High-performance liquid chromatography (HPLC) was used for the therapeutic drug monitoring of quinidine in clinical samples. Solid-phase extraction (SPE) was studied in both off-line and on-line modes. SPE was performed in an automatic on-line mode using a fully automated Prospekt system. Extraction recoveries were in the range 97.1-99.4% for 1-2 micrograms/ml quinidine concentrations. For HPLC separation an Ultrasep RP-8 reversed-phase column was applied with acetonitrile-water (9:1) containing 0.3% triethylamine (pH 2.5) as the mobile phase. The Prospekt system is recommended for the routine monitoring of quinidine in plasma samples. Concentrations were in therapeutic range (1.2-3.6 micrograms/ml).