HPLC/MS analysis of the metabolites of 2,4-toluenediamine (2,4-TDA) and 2,4-toluenediisocyanate (2,4-TDI) in rat urine

Profiles of the urinary metabolites of 2,4-toluenediisocyanate (2,4-TDI) and 2,4toluenediamine (2,4-TDA) have been studied in rats with the aim to find suitable biomarkers of 2,4-TDI exposure. The animals were dosed intraperitoneally with 0.10 mmol/kg of each compound. Urine was cleaned-up by the extraction with acetonitrile and by preparative HPLC to remove polar matrix components. The residuum containing a wide range of metabolites was analyzed by HPLC/MS in the APCI ionization mode. In the rats dosed with 2,4-TDA, most of the previously identified metabolites, namely, 4-acetylamino-2-aminotoluene, 2,4diacetylaminotoluene, their phenolic derivatives, 4-acetylamino-2-aminobenzoic acid, and 2,4-diacetylaminobenzoic acid, were confirmed. Over ten other compounds were detected and their molecular weight was determined tentatively. The level of urinary metabolites in rats dosed with 2,4-TDI was ca. two orders of magnitude lower compared with the equimolar dose of 2,4-TDA but still a number of products was detected. These were 4-acetylamino-2aminotoluene, 2,4-diacetylaminotoluene, 2,4-diacetylaminobenzoic acid, three unidentified compounds that were found also as metabolites of 2,4-TDA, and six unknown compounds formed via pathways not including 2,4-TDA („2,4-TDI-specific products“). Identification of the new metabolites will be a subject of future studies.