A report was presented of a capillary gas chromatographic method developed for quantitating mandelic-acid (90642) (MA) and phenylglyoxylic-acid (611734) (PGA), urinary metabolites of styrene (100425). Urine samples with added internal standard were treated with sulfuric-acid and zinc to reduce PGA to MA. Ethyl-acetate extracts were prepared and treated with N,O-bis-(trimethylsilyl)- trifluoroacetamide and isooctane prior to capillary gas chromatography with flame ionization detection. The method was calibrated using urine from an unexposed individual, containing internal standard only or spiked with MA to yield final concentrations of 0.001 to 2mg/ml. Urine samples were obtained from workers at three reinforced fiberglass products facilities (truck manufacturing, plastic pipe and tank manufacturing, plastic grate manufacturing). Replicate analyses of workers' urine samples initially showed large variation, due to poor solubility in derivatization solution of residue from solvent evaporation. Tests of several solvents indicated that dry ethyl-acetate gave the best response, providing the lowest coefficient of variation and reducing the lower limit of quantitation to 0.01mg/ml. Detector linearity and column loading limitations provided an upper limit of 2 to 4mg/ml. The lower limit (about 0.001mg/ml) was below typical MA levels in urine of unexposed persons. Spiked urine sample analysis yielded linear standard curves, with slight differences in slopes for MA and PGA. Relative precision below 5% was obtained in the range 0.05 to 2mg/ml. PGA was quantitated by the difference between MA measured with and without reduction. The authors conclude that this method provides increased precision and sensitivity for assay of urinary MA and PGA.
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