QUANTITATIVE COLORIMETRIC DETERMINATION OF URINARY P-AMINOPHENOL WITHAN AUTOMATED ANALYZER

We developed an automated colorimetric method for the quantitative det ermination of p-aminophenol with a Cobas Mira analyzer. The procedure can be used for the biological monitoring of human exposure to aniline . An absorbed aniline dose is extensively oxidized to rho-aminophenol, which is excreted in urine mainly as glucurono- and sulfo- conjugates . After enzymatic hydrolysis, we reacted the free compound with resorc inol in the presence of manganese ions to form an indophenol dye, whic h is measured at 550 nm. Excellent accuracy (102.8%, 103.9%, and 96.8% at 2.5, 50, and 90 mg/L, respectively) and precision (7.7%, 2.1%, and 0.8% CV for within-run and 11.1%, 4.7%, and 4.6% for total reproducib ility at 2.5, 50, and 90 mg/L, respectively) were achieved over a line ar concentration range of 2.0 to 100 mg/L. The detection limit was 0.9 mg/L and no significant interference (except for o-aminophenol) was f ound for several investigated drugs and related compounds. The propose d method was used for a stability study and to analyze several samples from an occupational health screen.