ELISA and GC/MS analysis of pesticide residues in North Carolina

Studies were conducted to analyze the presence of 11 pesticide residues in 12 surface waters in the Piedmont and coastal plain regions of North Carolina. Samples were assayed using enzyme-linked immunosorbent assays (ELISAs). All ELISA results of one part per billion (ppb, mu g/L) or greater were confirmed using gas chromatography/mass spectrometry (GC/MS). ELISA detection limits were approximately an order of magnitude higher than GC/MS methods. Of the 5,035 analytical results from 742 surface water samples, atrazine was detected in approximately 45 percent of the samples, five of which were at or above the Maximum Contaminant Level (MCL) of 3-ppb. Metolachlor was detected in 64 percent of the samples. Aldicarb, 2,4-D, chlorpyrifos, and chlorothalonil were also detected, and each was found in less than 12 percent of the samples. The remaining pesticides, including carbaryl, acetochlor, methomyl, carbofuran, and alachlor, were not detected during the study period.