Quantitative high pressure liquid chromatography of 6-thioguanine in biological fluids.

The determination of 6-thioguanine in human plasma and urine is described. By using isocratic reversed-phase high pressure liquid chromatography (HPLC) the purine analogues, 6-thioguanine, guanine, 8-azaguanine, allopurinol, oxipurinol, and uric acid, are completely separated within 8 min. the sensitivity of the assay for 6-thioguanine is 0.2 microgram/ml (1.2 x 10(-6) M) with a precision of 3.7%. The applicability for clinical monitoring in a patient's plasma and urine is demonstrated.