Stable Isotopic Fingerprinting for Identification of the Methyl Tert-Butyl Ether (MTBE) Manufacturer

Abstract

Since the late 1990s, methyl tert-butyl ether (MTBE) contamination in groundwater aquifers has become a serious concern in many countries. This study focused on the carbon and hydrogen isotopic compositions of MTBE reagents produced by six manufacturers from three regions, to investigate the potential of utilizing stable isotopes in tracing the production origin of MTBE. The carbon and hydrogen isotopic compositions (δ13C and δD) of MTBE ranged from −31.0% to −26.4% and −101% to −54%, respectively, and exhibited different signatures according to the manufacturer. Two different supplies of MTBE produced by the same manufacturer, however, had different carbon isotopic compositions, with a deviation of approximately 0.6‰. δ13C values of MTBE were classified according to the area of production (Japan, Europe and the United States), allowing the data from this study to be aligned with those of previous reports. The results suggest that both δ13C and δD values cannot be used to apportion sources of MTBE in detail, but that it is possible to apply a fingerprinting technique, which classifies the country of production of MTBE, using δ13C values alone. Minimal carbon isotope fractionation was observed during the progressive evaporation of MTBE, following the Rayleigh fractionation trend. The impurities of MTBE reagents, in particular the water contents, cause the gas-phase diffusion coefficient to vary and subsequently impact isotope fractionation. These data indicate that although significant loss of MTBE occurs by evaporation, the isotopic composition of the remaining MTBE in contaminated sites can be used to identify its production origin.