Determination of urinary hippuric acid and o-cresol, as indices of toluene exposure, by liquid chromatography on dynamically modified silica.

Two simple and sensitive high-performance liquid chromatographic methods for the determination of hippuric acid and o-cresol in urine have been developed. The chromatographic system is the same for the two methods and is based on dynamically modified silica. The detection limits were found to be 0.05 mg/ml and 0.05 microgram/ml of urine for hippuric acid and o-cresol, respectively, when using UV detection at 254 nm. The recovery for hippuric acid was about 100% and for o-cresol 33-36%. The detection limit for o-cresol could be lowered by a factor of ten by using fluorescence detection. The methods were used for investigations of the urine from persons exposed to 100 ppm toluene for 6.5 h. The method for o-cresol may also be used for determination of other phenols in urine.