Simple colorimetric semiquantitation method of hippuric acid in urine for demonstration of toluene abuse.

A semiquantitative method for hippuric acid in toluene sniffers' urine was explored by modifying the method by Tomokuni and Ogata. The color of sample urine mixed with pyridine and benzenesulfonyl chloride was yellow, and became reddish by addition of distilled water. Using the color chart, the concentration of hippuric acid could be semiquantitated in a few minutes. The values determined by this method were compared with those obtained by high performance liquid chromatography, showing a coefficient of determination (r2) of 0.8594. This colorimetric method is thus useful for rapid screening for hippuric acid in urine, or toluene sniffing.