DETERMINATION OF NICOTINE AND COTININE IN HUMAN PLASMA BY LIQUID-CHROMATOGRAPHY TANDEM MASS-SPECTROMETRY WITH ATMOSPHERIC-PRESSURE CHEMICAL-IONIZATION INTERFACE

Here we report a sensitive liquid chromatographic-tandem mass spectrom etric (LC-MS-MS) method capable of quantifying nicotine down to 1 ng/m l and cotinine to 10 ng/ml from 1.0 ml of human plasma. The method was validated over linear ranges of 1.0-50.0 ng/ml for nicotine and 10.0- 500.0 ng/ml for cotinine, using deuterated internal standards. Compoun ds were simply extracted from alkalinized human heparinized plasma wit h methylene chloride, reconstituted into a solution of acetonitrile, m ethanol and 10 mM ammonium acetate (53:32:15, v/v) after the organic p hase was dried down, and analyzed oh the LC-MS-MS, which is a PE Sciex API III system equipped with a Keystone BDS Hypersil C-18 column and atmospheric pressure chemical ionization (APCI) interface. The between -run precision and accuracy of the calibration standards were less tha n or equal to 6.42% relative standard deviation (R.S.D.) and less than or equal to 11.8% relative error (R.E.) for both nicotine and cotinin e. The between-run and within-run precision and accuracy of quality co ntrols, (2.5, 15.0, 37.5 ng/ml for nicotine and 25.0, 150.0, 375.0 ng/ ml for cotinine), were less than or equal to 6.34% R.S.D. and less tha n or equal to 7.62% R.E. for both analytes. Sample stabilities in chro matography, in processing and in biological matrix were also investiga ted. This method has been applied to pharmacokinetic analysis of nicot ine and cotinine in human plasma.