An efficient analytical method for determination of S-phenylmercapturic acid in urine by HPLC fluorimetric detector to assessing benzene exposure

Benzene is an important occupational and environmental contaminant, naturally present in petroleum and as by-product in the steel industry. Toxicological studies showed pronounced myelotoxic action, causing leukemic and others blood cells disorders. Assessing of benzene exposure is performed by biomarkers as trans, trans-muconic acid (AttM) and S-phenylmercapturic acid (S-PMA) in urine. Due to specificity of S-PMA, this biomarker has been proposed to asses lower levels of benzene in air. The aim of this study was to validate an analytical method for the quantification of S-PMA by High-Performance Liquid Chromatography with fluorometric detector. The development of an analytical method of S-PMA in urine was carried out by solid phase extraction (SPE) using C-18 phase. The eluated were submitted to water bath at 75 °C and nitrogen to analyte concentration, followed by alkaline hydrolysis and derivatization with monobromobimane. The chromatography conditions were reverse phase C-18 column (240 mm, 4 mm and 5 μm) at 35 °C; acetonitrile and 0.5% acetic acid (50:50) as mobile phase with a flow of 0.8 mL/min. The limits of detection and quantification were 0.22 μg/L and 0.68 μg/L, respectively. The linearity was verified by simple linear regression, and the method exhibited good linearity in the range of 10-100 μg/L. There was no matrix effect for S-PMA using concentrations of 40, 60, 80 and 100 μg/L. The intra- and interassay precision showed coefficient of variation of less than 10% and the recovery ranged from 83.4 to 102.8% with an average of 94.4%. The stability of S-PMA in urine stored at −20 °C was of seven weeks. The conclusion is that this method presents satisfactory results per their figures of merit. This proposed method for determining urinary S-PMA showed adequate sensitivity for assessment of occupational and environmental exposure to benzene using S-PMA as biomarker of exposure.