Simultaneous determination of chloroquine and its desethyl metabolite in human plasma by gas chromatography

A gas chromatographic method for the simultaneous determination of chloroquine and its metabolite desethylchloroquine in plasma described. Chloroquine, desethylchloroquine and internal standard are extracted as bases with n-hexane-pentanol (90:10) and then back-extracted to an acid aqueous phase. The aqueous phase is made alkaline and after re-extraction into chloroform and evaporation of the chloroform, acylation with trifluoroacetic anhydride is performed. Separation is achieved on an OV-17 column at 250 degrees C. Chloroquine and desethylchloroquine can be determined down to 0.1-0.2 mumol/l (30-60 ng/ml), with a coefficient of variation of 12%, using a nitrogen detector. The method shows good correlation (r = 0.98) with a recently developed liquid chromatographic method.