Measurement of 4-nonylphenol and 4-tert-octylphenol in human urine by column-switching liquid chromatography-mass spectrometry

We report a method for determining 4-nonylphenol (NP) and 4-tert-octylphenol (OP) levels in human urine samples by column-switching liquid chromatography-electrospray mass spectrometry after enzymatic deglucuronidation. The method involves enzymatic deconjugation by beta-glucuronidase and correction by the stable isotopically labeled internal standard, 4-(1-methyl)octylphenol-d(5). The compounds were separated by reversed-phase chromatography with a C-18 column, and detected by selected ion monitoring in the negative mode. After adding an internal standard to urine samples, a direct analysis was carried out. The average recoveries of OP and NP were above 85.0% with correction using the added internal standard. The quantitation limit in the urine samples was 0.3 ng ml(-1). The method enables the precise determination of standards and may be applied to the detection of trace amounts of OP and NP in human urine samples. (C) 2003 Elsevier Science B.V. All rights reserved.