Studies on a simultaneous analytical method of urinary nicotine and its metabolites, and their half-lives in urine.

The objectives of this research were to improve and standardize a relatively easy, highly sensitive and highly accurate method of measuring nicotine, cotinine and trans-3'-hydroxycotinine in the urine of non-smokers exposed to environmental tobacco smoke (ETS) and to clarify the reliability of this method. Blinded studies using this analytical method were conducted in two universities. Standard solutions of nicotine, cotinine and trans-3'-hydroxycotinine were prepared at one university, divided in two parts and sent to another two universities for analyses by gas chromatography-mass spectrometry (GC/MS) without revealing the concentrations. It was found that the assay lower limit was at a level that could be used in passive smoking surveys and good results were obtained in crosschecks of samples of unknown concentration between the two universities. Since this method was considered to be useful for analyzing these urinary substances, ETS exposure experiments were performed in three universities using urinary nicotine, cotinine and trans-3'-hydroxycotinine as specific biomarkers of the urine. Non-smokers were exposed to ETS in an exposure room in each university. It was found that the nicotine concentrations in the urine of the subjects exposed to ETS reached a peak at about 2 hours after the end of exposure, which was somewhat later than that in active smokers. Because cotinine and trans-3'-hydroxycotinine in the urine are metabolites of nicotine, it was evident that the quantities were lower and the increasing rates were also less than that of nicotine. When the deceases in nicotine/ creatinine, cotinine/creatinine and trans-3'-hydroxycotinine/creatinine ratios in the urine were calculated using theoretical curves, the half-life times were calculated to be 13.9, 20.0 and 63.0 hours, respectively.