A simple, rapid liquid chromatography-tandem mass spectrometry method was developed to identify and quantitate in human urine the isoprostanes iPF 2a -III, 15-epiiPF 2a -III, iPF 2a -VI, and 8,12-iso-iPF 2a -VI along with the prostaglandin PGF 2a and 2,3-dinor-iPF 2a -III, a metabolite of iPF 2a -III. Assay specificity, linearity, precision, and accuracy met the required criteria for most analytes. The urine sample storage stability and standard solution stability were also tested.The methodology was applied to analyze 24 h urine samples collected from smokers and nonsmokers on controlled diets. The results for iPF 2a -III obtained by our method were significantly correlated with results by an ELISA, although an ?2-fold high bias was observed for the ELISA data. For iPF 2a -III and its metabolite 2,3-dinoriPF 2a -III, smokers had significantly higher concentrations than nonsmokers (513 6 275 vs. 294 6 104 pg/mg creatinine; 3,030 6 1,546 vs. 2,046 6 836 pg/mg creatinine, respectively). The concentration of iPF 2a -VI tended to be higher in smokers than in nonsmokers; however, the increase was not statistically significant in this sample set. Concentrations of the other three isoprostane isomers showed no trends toward differences between smokers and nonsmokers. Among smokers, the daily output of two type VI isoprostanes showed a weak correlation with the amount of tobacco smoke exposure, as determined by urinary excretion of total nicotine equivalents.-Yan, W., G. D. Byrd, and M. W. Ogden. Quantitation of isoprostane isomers in human urine from smokers and nonsmokers by LC-MS/MS.

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The development and validation of a rapid liquid chromatography (LC)-tandem mass spectrometry (MS-MS) method for determination of nicotine and cotinine in smokers' serum is described. The method is based on solid-phase extraction in a 96-well plate format and requires only 100 microL of serum. Using normal-phase chromatography, both analytes elute in less than 1 min, which permits high sample throughput applications. The calibrated range is 2-100 ng/mL nicotine and 20-1,000 ng/mL cotinine. For known samples, recovery is 95-116% for nicotine and 93-94% for cotinine. The method is extended to rat serum and human saliva (cotinine only) using partial validation techniques. When compared with an existing radioimmunoassay method in our laboratory, the LC-MS-MS method gives improved accuracy, precision, and sample throughput.