Add time:08/02/2019         Source:sciencedirect.com

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 3 μg/l for 1,2-NQMA and 1 μg/l for 1,4-NQMA. Intraday- and interday precision for pooled urine (spiked with 10 μg/l and 30 μg/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.

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