Validation of an HPLC/MS/MS method with isotopic dilution for quantitative determination of trans,trans-muconic acid in urine samples of workers exposed to low benzene concentrations.

Urinary trans,trans-muconic acid (t,t-MA), a biomarker of benzene exposure, is usually determined by HPLC methods with detection by either UV or, more recently, electrospray tandem mass spectrometry. However, not all these methods have been fully validated for quantitative analysis. This paper presents an HPLC/MS/MS method for reliable quantitative determination of t,t-MA that uses a commercial deuterium-labeled isotope as internal standard; the matrix effect has been evaluated and LOD is 0.22 microg/L. We used this method to test 200 urine samples, 175 of them collected at end-of-shift from workers in an oil refinery.