Analysis of Degradation Products of Non-Persistent Pesticides in Soil Using Liquid Chromatography-Tandem Mass Spectrometry

Abstract

P-561 Abstract: Non-persistent pesticides were developed to counteract the persistence and bioaccumulation concerns associated with persistent pesticides. By their nature, they degrade in the environment quickly releasing multiple degradation products. The currently applied model for assessing organophosphorus (OP) pesticide exposure is through measuring non-specific dialkylphosphates and OP-specific metabolites in urine as biomarkers of exposure. This model assumes that measuring the metabolites in the body are good markers of exposure to parent pesticides in the environment. In this assumption, there exists a direct correlation between concentrations of parent pesticide in the environment to concentration of metabolite formed in urine. However, the model is obscured by the fact that OP pesticide breakdown products in the environment are usually the same chemical as the metabolite measured in the body. The potential contribution of degradation products found in the environment to the metabolite concentration found in people needs to be assessed. In order to determine this correlation, analytical methods need to be developed to extract, quantitate and evaluate breakdown products in environmental matrices. A single method for analyzing two classes of non-persistent pesticide (OP and pyrethroids) breakdown products in soil was developed. Pesticide degradation products were extracted from soil using pressurized fluid extraction (Dionex ASE®) followed by analysis using liquid-chromatography with atmospheric pressure chemical (APCI) and electrospray ionization (ESI) and tandem mass spectrometry. Additional clean-up steps post ASE® extraction were evaluated to determine any enhanced sensitivity and selectivity of target analytes. Nonspecific, specific OP and pyrethroid degradation products were isolated using ion exchange (for non-specific) and reversed phase (specific and pyrethroids) solid phase extraction post ASE extraction and analyzed with ESI and APCI with detection limits in the sub parts per billion to low parts per billion range with recoveries ranging from 70–110%. The results of these investigations lead to a single robust method capable of analyzing degradation products from two classes of pesticides with excellent recovery, sensitivity, and precision. As a consequence of the development of this method, initiation of studies determining how much, if any, degradation product formed in the environment contributes to the concentration of biomarkers in urine.