Capillary gas chromatographic method for mandelic and phenylglyoxylic acids in urine

Summary In support of an occupational investigation of styrene exposure, a capillary gas chromatographic method was developed for the quantitation of the styrene metabolites mandelic and phenylglyoxylic acids. The method was based on that of Guillemin and Bauer [7], in which phenylglyoxylic acid was converted to mandelic acid by reduction before instrumental analysis. The earlier method had to be modified for use with capillary columns; the resulting method was sensitive, selective and reproducible. The detection limit was approximately 0.001 mg/ml urine. Approximately <5% relative precision was achieved in the range of 0.05–2 mg/ml urine. Mandelic acid was resolved from other components of urine and from by-products of derivatization.