Extension of USEPA Method 531 for the Analysis of Several Classes of Nitrogenousand Aromatic Pesticides in Groundwater by Postcolumn UV Photolysis

摘要

The primary objective of the research was to expand the number of pesticides thatcan be analyzed in groundwater at trace levels by extending the USEPA Method 531 that now covers N-methyl carbamate and carbamoyl oxime pesticides to include several other classes of nitrogenous and aromatic pesticides by postcolumn ultraviolet (UV) photolysis. Online photolysis with a 2-watt mercury lamp in a Teflon tube knitted photoreactor was used to replace the conventional alkaline hydrolysis solution that is metered in postcolumn and the HPLC separations were optimized for several pesticides on reversed phase columns. Postcolumn on-line photolysis and/or photolysis followed by OPA-MERC reagent derivatization was sufficient for generation of fluorophores leading to enhanced fluorescence detection in HPLC for monitoring various pesticide residues in groundwater. The fluorescence detector sensitivity was optimized by selection of lamp type, photoreactor designs, photolytic solvents, and derivatization. The chromatographic resolutions and peak capacity were maximized by proper choice of analytical columns and elution solvent programming. Limits of detections less than 1 micrograms/l were obtained for several classes of nitrogenous and aromatic pesticides in groundwater by direct injection of 0.4 mL filtered water samples onto reversed phase analytical columns.