Evaluation of assays for the identification and quantitation of muconic acid, a benzene metabolite in human urine

Abstract

Muconic acid (MA) is a urinary metabolite of benzene and has been used as a biomarker of exposure to benzene in humans exposed to levels as low as 1 ppm. We have modified a high‐pressure liquid chromatography (HPLC) based assay for urinary MA (Ducos et al., 1990) by the use of a diode array detector. This modification increases the specificity of the HPLC‐based assay by identifying false positives. In addition, we have developed a gas chromatography (GC) based assay that uses a flame ionization detector (CC‐FID). Both assays identified and quantified MA in human urine at concentrations greater than 40–50 ng/ml. Assay precision was within 10% relative standard deviation for MA concentrations above 90 ng/ml using the HPLC assay and above 40 ng/ml using the CC‐FID assay. Quantitative accuracy of the assays was evaluated by determining MA in human urine samples using both methods and also a gas chromatography‐mass spectrometry (GC‐MS) procedure. Numerical correlation among the three assays was good at MA concentrations above 100 ng/ml.