High-performance liquid chromatography of quinidine in plasma, with use of a microparticulate silica column

We describe a routine method for determining plasma concentrations of quinidine by liquid chromatography. The procedure requires 1.0 ml of plasma (or serum) and involves internal standard addition, extraction with ether, and separation on a column of microparticulate silica. Day-to-day CV (15 days) was less than 5% and no deterioration in column performance has been observed during 12 months. Comparison with a fluorometric procedure gave a correlation coefficient of 0.995.