Analysis and stability of phenylglyoxylic and mandelic acids in the urine of styrene-exposed people

In this work a high-performance liquid chromatographic method is described that is reliable and practical for use in routine biological monitoring of exposure to styrene. The method uses a modern diode array detection technique by which mandelic and phenylglyoxylic acids can be measured simultaneously using different wavelengths. The liquid chromatographic method was compared to a gas chromatographic method developed for the analysis of mandelic, phenylglyoxylic and para-hydroxymandelic acids. The methods gave results consistent with each other. These two methods were then used to check the stability of the main metabolites of styrene, especially of phenylglyoxylic acid, in urine samples stored at +6 degrees C or at -18 degrees C for periods up to 70 days. None of the frozen samples showed any significant decrease in the phenylglyoxylic acid concentration, whereas at 6 degrees C one of the samples showed a reduction of 46% after 1 month.