title: Quantification of naphthoquinone mercapturic acids in urine as biomarkers of naphthalene exposure.
abstract: Naphthalene shows carcinogenic properties in animal experiments. As the substance is ubiquitary present in the environment and has a possibly high exposure at industrial workplaces, the determination of naphthalene metabolites in humans is of environmental-medical as well as occupational-medical importance. Here, biomarkers of 1,2- and 1,4-naphthoquinone, as possibly carcinogenic metabolites in the naphthalene metabolism, are of outstanding significance. We developed and validated a liquid chromatography-tandem mass-spectrometric (LC-MS/MS) method for the simultaneous determination of the naphthoquinone mercapturic acids of 1,2- and 1,4-naphthoquinone in human urine samples as a sum of naphthoquinone- and dihydroxynaphthalene-mercapturic acid. Except for enzymatic hydrolysis and acidification, no further sample preparation is necessary. For sample clean-up, a column switching procedure is applied. The mercapturic acids are extracted from the urinary matrix on a restricted access material (RAM RP 18) and separated on a reversed phase column (Synergi Polar RP C18). The metabolites were quantified by tandem mass spectrometry using labelled D5-1,4-NQMA as internal standard. The limits of detection are 3μg/l for 1,2-NQMA and 1μg/l for 1,4-NQMA. Intraday- and interday precision for pooled urine (spiked with 10μg/l and 30μg/l of the analytes) ranges from 5.9 to 15.1% for 1,2-NQMA and from 2.0 to 10.8% for 1,4-NQMA. The developed method is suited for the sensitive and specific determination of the mercapturic acids of naphthoquinones in human urine. A good precision and low limits of detection were achieved. Application of those new biomarkers in biomonitoring studies may give deeper insights into the mechanisms of the human naphthalene metabolism.
authors.affiliation: Institute and Outpatient Clinic of Occupational, Social and Environmental Medicine, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Schillerstr. 25/29, D-91052 Erlangen, Germany. Electronic address: katrin.klotz@fau.de.
authors.forename: Katrin
authors.initials: K
authors.lastname: Klotz
authors.affiliation: Institute for Prevention and Occupational Medicine of the German Social Accident Insurance, Institute of the Ruhr-Universität Bochum (IPA), Bürkle-de-la-Camp-Platz 1, 44789 Bochum, Germany. Electronic address: angerer@ipa-dguv.de.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Angerer
mesh_terms: D000111:Acetylcysteine / Q000652:urine*; D015415:Biomarkers / Q000652:urine*; D002853:Chromatography, Liquid; D004781:Environmental Exposure / Q000032:analysis*; D006801:Humans; D057230:Limit of Detection; D016014:Linear Models; D009285:Naphthoquinones / Q000652:urine*; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry
chemical_list: D015415:Biomarkers; D009285:Naphthoquinones; D000111:Acetylcysteine
keywords: Biomarker; Biomonitoring; Mercapturic acid; Naphthalene; Naphthoquinone; Urine