Determination of UV-327 and its metabolites in human urine using dispersive liquid-liquid microextraction and gas chromatography-tandem mass spectrometry

The benzotriazole UV stabilizer (BUVS) 2-(5-chloro-benzotriazol-2-yl)-4,6-di-(tert-butyl)phenol (UV-327) is added to plastic materials for UV protection. The compound is known to be ubiquitously distributed in the environment. We developed the first analytical method for the determination of UV-327 and seven metabolites, which were identified in vitro, in urine to be able to investigate the in vivo metabolism of UV-327 and to assess potential human exposure to the compound. Enzymatic hydrolysis of phase II conjugates is followed by sample purification with dispersive liquid-liquid microextraction (DLLME). The analytes are extracted from the urine samples after acidification with hydrochloric acid solution and addition of sodium chloride solution. Isopropyl alcohol and chloroform are used as disperser solvent and extraction solvent, respectively. After derivatization, the trimethylsilylated analytes are chromatographically separated and detected by gas chromatography coupled with tandem mass spectrometry (GC-MS/MS). To achieve maximum extraction of the analytes from the sample solution, the DLLME procedure was optimized with respect to the type and volume of disperser and extraction solvent, the pH value of the sample solution, the addition of salt, and the duration of vortex-mixing. Subsequent method validation demonstrated high sensitivity and reliability, with limits of detection (LODs) between 0.05 and 0.1 μg l-1 and mean relative recovery rates ranging from 88 to 112%. Precision and repeatability were proven by relative standard deviations ranging from 1 to 13% and from 5 to 14%, respectively.