AN INEXPENSIVE AND SENSITIVE METHOD FOR THE DETERMINATION OF QUINIDINE IN PLASMA BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH ULTRAVIOLETDETECTION

A sensitive, specific, and rapid high-performance liquid chromatograph ic method with ultraviolet detection for therapeutic drug monitoring o f the cardioactive compound quinidine is described. The method uses on ly 50 mu l of serum, which is extracted into methyl-t-butylether at an alkaline pH and consequently reextracted into dilute hydrochloric aci d. Quinidine is separated from quinine, the internal standard, and dih ydroquinidine on a reversed phase C18 column. The minimum detectable a mount is 1 ng injected on column. The method is both precise and accur ate, as shown by the validation data presented, and can also be of use in pharmacokinetic investigations.