Metabolism of four tobacco-specific N-nitrosamines (TSNAs), N′-nitrosonornicotine (NNN), N′-nitrosoanatabine (NAT), N′-nitrosoanabasine (NAB), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) has been studied by solid-phase extraction (SPE) and liquid chromatography–tandem mass spectrometry (LC–MS–MS). 4-(Methylnitrosamino)-4-(3-pyridyl)-1-butanol (iso-NNAL) was used as internal standard. SPE and LC–MS–MS was found to be a rapid, simple, sensitive, and selective method for analysis of TSNAs in rabbit serum. The relative standard deviation (R.S.D., n = 6) for analysis of 5 ng mL−1 and 0.5 ng mL−1 standards and of serum sample spiked with 5 ng mL−1 standards of five TSNAs was 2.1–11% and recovery of 5 ng mL−1 standards from serum was 100.2–112.9%. A good linear relationship was obtained between peak area ratio and concentration in the range of 0.2–100 ng mL−1 for NNAL and 0.5–100 ng mL−1 for other four TSNAs, with correlation coefficients ( R 2) >0.99 (both linear and log–log regression). Detection limits for standards in solvent were between 0.04 and 0.10 ng mL−1. Doses of TSNAs administered to rabbits via the auricular vein were 4.67 μg kg−1 and 11.67 μg kg−1, in accordance with the different levels in cigarettes. Metabolic curves were obtained for the four TSNAs and for 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a metabolite of NNK; on the basis of these curves we modeled metabolic kinetic equations for these TSNAs by nonlinear curve fitting. [ABSTRACT FROM AUTHOR]
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