Measurement of urinary hippuric and m-methylhippuric acids by gas chromatography.

Buchet, J. P., and Lauwerys, R. R. (1973). British Journal ofIndustrial Medicine, 30, 125-128. Measurement of urinary hippuric and m-methylhippuric acids by gas chromatography. A gas chromatographic method for the determination of hippuric and m-methylhippuric acids in urine is described. A known amount of heptadecanoic acid (internal standard) is added to the urine before its extraction with ethyl acetate. After evaporation of the solvent, the acids are methylated with diazomethane. The residue is taken up in methanol and injected into the gas chromatograph. The ratio of the height of the hippuric or m-methylhippuric acid peak to the height of the heptadecanoic acid peak is calculated and by reference to a calibration curve prepared in the same conditions the urine concentration of the two acids is determined.