High-performance liquid chromatographic determination of 3,5-dimethylhippuric acid in the occupational exposure to trimethylbenzenes.

A high-performance liquid chromatographic method for the measurement of urinary 3,5-dimethylhippuric acid (3,5-DMHA) in the human biological monitoring of the occupational exposure to trimethylbenzenes has been developed. 3,5-DMHA was extracted from urine with ethyl acetate. The organic phase was dried under vacuum and the resultant product, dissolved in the mobile phase, was analysed by an isocratic system and a programmable photodiode-array detector adjusted to 205 nm. The mobile phase was water-acetonitrile (80:20, v/v) containing 0.1% acetic acid. 3,5-DMHA was chromatographed on a reversed-phase Supelco C18 column (3 microns; 15 cm x 0.46 cm I.D.), and identified by its retention time and ultraviolet spectrum. Quantitation was performed by peak area. The detection limit of the method is 30 ng/ml and the recovery and the accuracy are 96%.