DETERMINATION OF COLCHICINE IN BIOLOGICAL -FLUIDS BY LIQUID-CHROMATOGRAPHY MASS-SPECTROMETRY WITH PNEUMATICALLY ASSISTED ELECTROSPRAY-IONIZATION

A sensitive and specific method for the determination of colchicine in urine, serum, plasma and whole blood has been developed, using HPLC c oupled to mass spectrometry with pneumatically assisted electrospray i onization. A simple alcaline (pH = 8.0) extraction of 1 mt of biologic al fluid was performed with a mixture of diethylether : methylenechlor ide (7 :4, nu/nu). The organic layer was evaporated to dryness, the re sidue redissolved in 50 mu L Of mobile phase, and 7 mu L was injected in the chromatographic system. A Nucleosil C-18 150 x I mm id column w as used for separation with a 2 mM ammonium formate (pH = 3.0) : aceto nitrile (65/35, nu/nu) mixture as mobile phase. Colchicine was detecte d by selected-ion monitoring of three characteristic ions. The lineari ty of the method was assessed in the range from 0.1 to 100 ng/mL (r > 0.999, n = 8). Excellent infra-day precision coefficients of variation (cv < 9 %, n = 7) were obtained at concentrations of 0.5, 5, and 50 n g/mL. Intermediate precision yielded CVs lower than 10 % between 0.5 a nd 100 ng/mL land less than 18 % at the 0.1 ng/mL level (limit of quan tification). The present method can be applied both to toxicological d iagnosis and to therapeutic monitoring of colchicine.