Analysis of Urine to Monitor Exposures to Benzidine, o-Dianisidine, o-Tolidine, and 4, 4′-Methylenedianiline

Abstract

Aromatic diamines have great potential for dermal absorption as an exposure route. Also, the body exhibits the ability to reductively cleave an azo dye to its corresponding aromatic diamine. These factors have demonstrated the need for biological monitoring to complement environmental monitoring when assessing occupational exposures to these compounds. This is especially important since certain aromatic diamines are known or are potential human carcinogens. Therefore, a sampling and analytical procedure for the measurement of benzidine, o-dianisidine, o-tolidine, and 4, 4′-methylenedianiline in urine was developed for use in industrial hygiene investigations. After hydrolysis of urine metabolites, the free diamines are isolated using a C₁₈ solid sorbent. The free diamines are eluted, concentrated, and injected into a high-performance liquid chromatography system. Separation is achieved using a C₁₈ column with a mobile phase of acetonitrile and water. Identification and quantitation is achieved by monitoring the ultraviolet (UV) absorbance at 280 or 245 nm and the electrochemical response. Using UV detection, the limit of detection (LOD) for these aromatic diamines was less than 2 μg/L while the limit of quantitation (LOQ) was less than 6 μg/L. For electrochemical detection, the LOD was less than 0.3 μg/L and the LOQ was less than 0.9 μg/L. Recoveries range from 87 to 102 percent at 2 μg/L, 10 μg/L, and 20 μg/L levels.