Validation of an assay for the determination of cotinine and 3-hydroxycotinine in human saliva using automated solid-phase extraction and liquid chromatography with tandem mass spectrometric detection

The validation of a high-performance liquid chromatographic method for the simultaneous determination of low level cotinine and 3-hydroxycotinine in h uman saliva is reported. Analytes and deuterated internal standards were ex tracted from saliva samples using automated solid-phase extraction, the col umns containing a hyper cross-linked styrene-divinylbenzene copolymer sorbe nt, and analysed by reversed-phase liquid chromatography with tandem mass s pectrometric detection (LC-MS-MS). Lower limits of quantitation of 0.05 and 0.10 ng/ml for cotinine and 3-hydroxycotinine, respectively, were achieved . Intra- and inter-batch precision and accuracy values fell within +/-17% f or all quality control samples, with the exception of quality control sampl es prepared at 0.30 ng/ml for 3-hydroxycotinine (inter-day precision 21.1%) . Results from the analysis of saliva samples using this assay were consist ent with subjects' self-reported environmental tobacco smoke (ETS) exposure s, enhancing the applicability of cotinine as a biomarker for the assessmen t of low level ETS exposure. (C) 1999 Elsevier Science B.V. All rights rese rved.