Simultaneous determination of aromatic acid metabolites of styrene and styrene-oxide in rat urine by gas chromatography - flame ionisation detection

A convenient and reliable gas chromatographic method was developed for the simultaneous determination of six aromatic acid metabolites of styrene and styrene-oxide in rat urine: i.e. benzoic (BA), phenylacetic (PAA), mandelic (MA), phenylglyoxylic (PGA), hippuric (HA) and phenylaceturic (PAUA) acids. The method involves a one-pot esterification-extraction procedure, performed directly on urine without prior treatment. Analyses were performed on a RTX-1701 capillary column and the recovered isopropyl esters derivatives were detected by flame ionization detection. The analytical method was validated for: selectivity, linearity, detection and quantification limits, recovery, intra and inter-day precisions. Calibration curves showed linearity in the range of 8 – 800 mg/L except for HA and PAUA (40 – 800 mg/L). Limits of detection were between 0.2 (PPA) and 7.0 (PAUA) mg/L. The intra-day precisions determined at three concentrations levels were less than 5% and 9% for BA, PAA, MA, PGA, on one hand, and HA and PAUA on the other hand respectively. The corresponding mean inter-day precisions for these two groups were 8% and 16% respectively. The method was successfully applied to quantitatively analyze styrene, styrene-oxide, ethylbenzene and toluene metabolites in urines samples from rats exposed by inhalation to these compounds at levels close to the occupational threshold limit values. Provided that this method can be transposed to human urine, it could have applications as part of biological monitoring for workers exposed to styrene or related compounds.