EVALUATION OF ASSAYS FOR THE IDENTIFICATION AND QUANTITATION OF MUCONIC ACID, A BENZENE METABOLITE IN HUMAN URINE

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 t he HPLC-based assay by identifying raise positives. In addition, we ha ve developed a gas chromatography (GC) based assay that uses a flame i onization detector (GC-FID). Both assays identified and quantified MA in human urine at concentrations greater than 40-50 ng/ml. Assay preci sion 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-FI D assay. Quantitative accuracy of the assays was evaluated by determin ing MA in human urine samples using both methods and also a gas chroma tography-mass spectrometry (GC-MS) procedure. Numerical correlation am ong the three assays was good at MA concentrations above 100 ng/ml.