An improved gas chromatographic method for the simultaneous determination of chloroquine and two metabolites using capillary columns.

A gas chromatographic method for the simultaneous determination of therapeutic levels of chloroquine, and the metabolites deethyl chloroquine and bideethyl chloroquine in human whole blood, plasma and urine has been developed by use of the capillary column technique. The analytes were extracted as bases with n-hexane-1-pentanol (90:10) and re-extracted into an acidic aqueous phase. After a further extraction to a small volume of chloroform, the substances were injected by the falling needle technique onto a fused-silica capillary column followed by nitrogen-selective detection. Limits of determination using 2 ml of the sample were found to be 10 nmol/l (3 ng/ml) for chloroquine and deethyl chloroquine and 30-40 nmol/l (10 ng/ml) for bideethyl chloroquine with a coefficient of variation of less than 15%. The precision of the method at the 100 nmol/l level was about 4% (n = 8) for chloroquine.