Quantitative determination in urine of hippuric acid and m- or p-methylhippuric acid, metabolites of toluene and m- or p-xylene.

330-334. Improved and more specific methods for the quantitative determination of hippuric and - and -methylhippuric acids in urine are described. The acids were extracted from urine with ether/ethanol, which was dried with silica gel, or with ethyl acetate. After removing the solvent by evaporation coloured azlactones were formed by reaction with -dimethylaminobenzaldehyde in acetic anhydride (DAB, only usable after ether/ethanol extraction) or benzenesulphonyl chloride in pyridine, and the absorbances were measured. The sensitivities were about 4 μg./ml. of urine using DAB, and 20 μg./ml. of urine using benzenesulphonyl chloride reagent. Separation of hippuric and methylhippuric acids was achieved by paper and thin-layer chromatography before estimation. A spot test is also described.