SIMULTANEOUS DETERMINATION OF AZATHIOPRINE AND 6-MERCAPTOPURINE BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A specific, sensitive, single-step solid-phase extraction and reversed -phase high-performance liquid chromatographic method for the simultan eous determination of plasma 6-mercaptopurine and azathioprine concent rations is reported. Following solid-phase extraction, analytes are se parated on a C-18 column with mobile phase consisting of 0.8% acetonit rile in 1 mM triethylamine, pH 3.2, run on a gradient system. Quantita tion limits were 5 ng/ml and 2 ng/ml for azathioprine and 6-mercaptopu rine, respectively. Peak heights correlated linearly to known extracte d standards for 6-mercaptopurine and azathioprine (r=0.999) over a ran ge of 2-200 ng/ml. No chromatographic interferences were detected.