Liquid Chromatographic Determination of Pesticides in Finished Drinking Waters: Collaborative Study

Abstract

A joint U.S. Environmental Protection Agency (EPA)/AOAC International collaborative study was conducted on EPA National Pesticide Survey Method 4, Determination of Pesticides in Finished Drinking Water by High Performance Liquid Chromatography with an Ultraviolet Detector, to determine mean recovery and precision for analyses of 18 pesticides and metabolites in reagent water and finished drinking waters. The study design was based on Youden's nonreplicate plan for collaborative studies of analytical methods. The waters were spiked with 18 pesticides and metabolites at 6 concentration levels, prepared as 3 Youden pairs. Ten volunteer laboratories extracted the spiked test waters with methylene chloride, performed a solvent exchange with methanol, and analyzed an aliquot of each extract by liquid chromatography using an ultraviolet detector at 254 nm. Results were analyzed using an EPA computer program that calculated recovery and precision for each of the 18 compounds and compared method performance between water types. The method was judged useable for all analytes tested. Recoveries were good for 16 of the analytes. The method exhibited poor recovery but acceptable between-laboratory precision for metribuzin DADK and metribuzin DK. The method performance statistics for carbofuran phenol and linuron were calculated to be significantly different for reagent water and finished drinking water. Similar statistical differences were observedfor metribuzin DADK, but these effects were not considered of practical significance due to the poor recovery (<25%) in both waters. In reagent water, the overall relative standard deviation (RSDR) range was 7.8-24.1% for all 18 compounds and 5.5-38.6% in finished drinking water. The single- analyst relative standard deviations (RSDr) range was 5.7-17.6% in reagent water and 4.0- 18.7% in finished drinking water. The method has been adopted first action by AOAC International.

Part-per-Trillion Level Determination of Priority Methyl-, Nitro-, and Chlorophenols in River Water Samples by Automated On-Line Liquid/Solid Extraction Followed by Liquid Chromatography/Mass Spectrometry Using Atmospheric Pressure Chemical Ionization and Ion Spray Interfaces

“…Acceptable values for trichlorophenol and pentachlorophenol were obtained with LSE-LC/APCI-MS. A higher coefficient of variation (CV) was obtained for phenol, with a 28% deviation with respect to the target value, using LSE-LC/ISP-MS. In previous interlaboratory studies of water samples containing chlorinated compounds and acidic herbicides, the overall CV varied from 5.5 to 38% and from 17 to 49% using either LC/UV or LC/MS (PB or TSP). , These data were obtained using standard calibrated solutions with no sample pretreatment. The CVs obtained in the present work also involve a sample pretreatment using on-line LSE similar to that reported previously for organophosphorus pesticides .…”

Comparison of on-line solid-phase disk extraction to liquid-liquid extraction for monitoring selected pesticides in environmental waters

“…Liquid chromatography (LC) systems used for environmental pesticide analyses were extensively reviewed in a recent paper (1). Different EPA and National Pesticide Survey (NPS) methods include the analysis of carbamates, e.g., aldicarb and their polar transformation products (TPs), e.g., carbofuran phenol (2,3).…”

“…In addition, thermospray mass spectrometry will serve as the confirmation technique to avoid false positives present in the water matrix. The different approaches used show application for the determination of 30 pesticides of different chemical nature and their corresponding TPs, which are of interest within the EEC Drinking Water Directive (17) and the NPS-U.S. EPA monitoring program (2,3).…”