Liquid Chromatography-Mass Spectrometry for muconic, mandelic, hippuric and methylhippuric acids analysis in human urine as metabolites for fuel exposure

Abstract

Muconic acid (MUC), mandelic acid (MAN), hippuric acid (HIP) and orthomethylhippuric acid (MHP) are four fuel metabolites which are analyzed in urine using Liquid Chromatography-Mass Spectrometry (LC-MS). The developed method is suitable for the quantitative analysis of the targeted metabolites in urine of healthy gas stations workers. The method is sensitive and selective to simultaneously analyze the four metabolites in presence of any possible urine interferences. The method is non-invasive and needs no extraction procedure prior to analysis so it can be applied for routine medical check of gas stations workers. A comparative study was applied for monitoring the metabolites level in the urine of workers before and after shift. The data reveals a significant increase in all metabolites level after shift at p = 0.05 using paired t-test (n = 20). The method is simple as Shim-pack® XR – ODS II column was used as stationary phase with a gradient eluting solvent of 1% formic acid and acetonitrile. The metabolites were resolved with retention times of 3.1, 5.8, 6.2 and 11.1 min for MUC, MAN, HIP and MHP, respectively. The MS detector was adjusted to negative SIM mode to eliminate the interference and enhance sensitivity. The selected m/z values were 141, 151, 178, and 192 for MUC, MAN, HIP and MHP, respectively.