A rapid and sensitive liquid chromatography-tandem mass spectrometry method for the quantitation of S-phenylmercapturic acid in human urine

A rapid, sensitive and robust method based on high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for the quantitation of S-phenylmercapturic acid (S-PMA), a metabolite of benzene, in human urine. Urine samples to which S-phenylmercapturic acid-d2 (S-PMA-d2) had been added as an internal standard (I.S.) were subjected to liquid–liquid extraction (LLE) with ethyl acetate in an acidic environment. S-PMA and the I.S. were separated on a C18 column and detected in negative ion and multiple reaction monitoring mode within 1.8 min. The assay was fully validated and exhibited good linearity in the concentration range of 0.2–200 ng mL−1, with a lower limit of quantitation of 0.2 ng mL−1. The intra- and inter-day precisions were