Compound specific isotope analysis of the pesticides bentazone, MCPA, dichlobenil and its main metabolite BAM: Method validation and degradation studies.

In this work compound specific isotope analysis (CSIA) of the pesticides bentazone, MCPA, 2,6-dichlorobenzonitrile atrazine as well as their metabolites 2,6 dichlorobenzamide (BAM) and desethylatrazine were developed and optimized, respectively. CSIA has become a promising tool to determine the carbon and nitrogen isotope composition of organic compounds. Natural transformation reactions are associated with kinetic isotope effects, which typically cause an enrichment of heavier isotopes in the reacting contaminant. This may allow a qualitative as well as a quantitative assessment of contaminants during biodegradation without complete mass balances. The study demonstrates the potential and the practicability of CSIA using BAM as an example substance. Biodegradation of BAM resulted in an isotope fractionation and showed a clear trend for carbon and nitrogen enrichment with proceeding extent of degradation. Furthermore we got a first clue on the reaction chemistry of enzymatic BAM transformation. To this end, the work offers a method to assess the environmental fate of BAM