ELEMENT-SELECTIVE DETECTION OF PESTICIDES BY GAS-CHROMATOGRAPHY ATOMIC-EMISSION DETECTION AND SOLID-PHASE MICROEXTRACTION

The analysis of samples contaminated by organic compounds, especially pesticides, is an important tool of environmental monitoring. A new isolation method has been developed for the determination of pesticides in environmental water samples using solid-phase microextraction (SPME). Thus, the extraction and preconcentration steps of sample preparation are focused in a single process step. For the determination of organophosphorus pesticides using SPME extraction and preconcentration steps a GC-atomic emission detection coupling system was used. This coupling technique is a very selective analytical tool. Element-characteristic chromatograms acquired by using different element emission lines can be obtained, enhancing the selectivity of the method in environmental monitoring, and they can be used to identify even unknown compounds in environmental samples. A fused-silica fiber coated with a polymer (polydimethylsiloxane) phase is used to extract organic compounds and transfer them into a GC injector for thermal desorption and analysis. Volatile pesticides can be efficiently isolated from aqueous environmental samples, as demonstrated for organophosphorus pesticides. This method shows a precision of 8-12% (R.S.D.), depending on the compound. Furthermore, it is capable of limits of detection in the ppb and sub-ppb range. The adsorption and desorption times to carry out the optimum equilibrium and thermodesorption conditions, have been optimized. Determination of pesticides in spiked river water samples with this technique is reported and a comparison of SPME to established extraction techniques, i.e. solid-phase extraction is also carried out. The results demonstrate the suitability of the SPME approach for analysis of these polar compounds.