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

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 β-glucuronidase and correction by the stable isotopically labeled internal standard, 4-(1-methyl)octylphenol-d5. The compounds were separated by reversed-phase chromatography with a C18 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.