A rapid colorimetric method for the determination of phenylglyoxylic and mandelic acids: Its application to the urinalysis of workers exposed to styrene vapour

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Abstract
Ohtsuji, H., and Ikeda, M.(1970).Brit. J. industr. Med.,27, 150-154. A rapid colorimetric method for the determination of phenylglyoxylic and mandelic acids. Its application to the urinalysis of workers exposed to styrene vapour. A rapid colorimetric method has been developed for the determination of the styrene metabolites, phenylglyoxylic and mandelic acids, in urine. Ether extracts of acidified urine containing the two acids were evaporated to dryness in a test tube, and a mixture of sulphuric acid and formalin (100:1, v/v) was added for colour development. Factors necessary to convert optical extinction to gravimetric units were determined. When urinesamples from workers exposed to up to 30 ppm of styrene were analysed for phenylglyoxylic and mandelic acids together with hippuric acid, it was found that the phenylglyoxylic acid level provided the most sensitive index of styrene exposure and that the optical extinction at 350 nm was practically proportional to phenylglyoxylic acid concentration. No significant increase in hippuric acid levels was observed.