Detection of triclocarban and two co-contaminating chlorocarbanilides in US aquatic environments using isotope dilution liquid chromatography tandem mass spectrometry

The antimicrobial compound triclocarban (TCC; 3,4,4′-trichlorocarbanilide; CAS♯ 101-20-2) is a high-production-volume chemical, recently suggested to cause widespread contamination of US water resources. To test this hypothesis, we developed an isotope dilution liquid chromatography electrospray ionization tandem mass spectrometry method for ultratrace analysis of TCC (0.9 ng/L detection limit) and analyzed low-volume water samples (200 mL) along with primary sludge samples from across the United States. All river water samples (100%) collected downstream of wastewater treatment plants had detectable levels of TCC, as compared to 56% of those taken upstream. Concentrations of TCC (mean±standard deviation) downstream of sewage treatment plants (84±110 ng/L) were significantly higher (P<0.05P<0.05; Wilcoxon rank sum test) than those of samples taken upstream (12±15 ng/L). Compared to surface water, mean TCC concentrations found in dried, primary sludge obtained from municipal sewage treatment plants in five states were six orders of magnitude greater (19,300±7100 μg/kg). Several river samples contained a co-contaminant, identified based on its chromatographic retention time, molecular base ion, and MS/MS fragmentation behavior as 4,4′-dichlorocarbanilide (DCC; CAS♯ 1219-99-4). In addition to TCC and DCC, municipal sludge contained a second co-contaminant, 3,3′,4,4′-tetrachlorocarbanilide (TetraCC; CAS♯ 4300-43-0). Both newly detected compounds were present as impurities (0.2%w/w each) in technical grade TCC (99%). Application of the new method for chlorocarbanilide analysis yielded TCC occurrence data for 13 US states, confirmed the role of sewage treatment plants as environmental inputs of TCC, and identified DCC and TetraCC as previously unrecognized pollutants released into the environment alongside TCC.