HIGH-PRESSURE LIQUID-CHROMATOGRAPHIC DETERMINATION OF TOLUENE IN URINE AS A MARKER OF OCCUPATIONAL EXPOSURE TO TOLUENE

Objective: To establish a convenient method by high-pressure liquid ch romatography (HPLC) to measure toluene in urine as a marker of occupat ional exposure to toluene. Methods: As soon after sampling as possible , 1 mi of urine was mixed with an equal volume of acetonitrile in a 2. 2-ml HPLC glass bottle, and the bottle was tightly sealed and stored a t 4 degrees C. Immediately before HPLC determination, 100 mu l methano l was added to the mixture to prevent confounding effects of glycosuri a, and the bottle was spun to remove any suspended matter. An aliquot of the supernate was introduced into the HPLC system and analyzed on a PRODIGY column, with an acetonitrile - perchloric acid - phosphoric a cid - water mixture serving as the mobile phase. The effluent was moni tored at 191 nm. Results: The method can measure toluene in urine ever y 20 min; the detection limit was 2 mu g/l, the coefficient of variati on was less than 5%, and the recovery rate was 100%. No significant re duction in toluene concentration was observed for 1 week after storage at 4 degrees C. When the method was applied to end-of-shift urine sam ples from 13 male workers exposed to toluene at 18-140 ppm and also to urine samples from 10 nonexposed male controls, toluene in urine was linearly related to toluene exposure concentration, with a regression line passing close to the origin. The correlation coefficient was as h igh as 0.97 (n = 23). No toluene was detected in control urine samples . Calculations suggest that urinary toluene accounts for as little as less than 0.01% of the toluene absorbed via inhalation and that the ab sorbed toluene is converted almost quantitatively to hippuric acid and , by less than 0.1%, to o-cresol.