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-PMAd2) 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 C-18 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 < 8.1%, with a relative error < 6.9%. The short run time coupled with the efficient one-step LLE sample preparation procedure makes the proposed method a promising strategy for the high-throughput and cost-effective analysis of urinary S-PMA levels, which is required to evaluate the health risk of exposure to benzene or cigarette smoking.