DETERMINATION OF QUINIDINE AND DIHYDROQUINIDINE IN PLASMA BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A rapid, specific and sensitive high performance liquid chromatographic method has been developed for the determination of quinidine (Q) and dihydroquinidine (DHQ) in human plasma. Plasma samples are extracted with a benzene-isoamyl alcohol mixture (1:1) followed by separation on a microparticulate reverse-phase column. Quinidine, dihydroquinidine, their metabolites are detected by fluorescence in acid medium using post-column addition of sulfuric acid. Plasma concentrations as low as 0.05 μg/mL can be measured with a relative standard deviation less than 10%. The complete assay procedure takes about 30 min. Recovery from plasma is at least 95 %. A linear response is obtained in the concentration range of 0.05 to 10 μg/mL of quinidine in plasma. The minimum detectable quantity is 1 ng on column. © 1979, American Chemical Society. All rights reserved.