Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory-Determination of organophosphate pesticides in whole water by continuous liquid-liquid extraction and capillary-column gas chromatography with flame photometric detection
Water-Resources Investigations Report
2003-4139
By: Virendra K. Jha and Duane S. Wydoski
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Abstract
A method for the isolation of 20 parent organophosphate pesticides and 5 organophosphate pesticide degradates from natural-water samples is described. Compounds are extracted from water samples with methylene chloride using a continuous liquid-liquid extractor for 6 hours. The solvent is evaporated using heat and a flow of nitrogen to a volume of 1 milliliter and solvent exchanged to ethyl acetate. Extracted compounds are determined by capillary-column gas chromatography with flame photometric detection. Single-operator derived method detection limits in three water-matrix samples ranged from 0.003 to 0.009 microgram per liter. Method performance was validated by spiking all compounds in three different matrices at three different concentrations. Eight replicates were analyzed at each concentration in each matrix. Mean recoveries of most method compounds spiked in surface-water samples ranged from 54 to 137 percent and those in ground-water samples ranged from 40 to 109 percent for all pesticides. Recoveries in reagent-water samples ranged from 42 to 104 percent for all pesticides. The only exception was O-ethyl-O-methyl-S-propylphosphorothioate, which had variable recovery in all three matrices ranging from 27 to 79 percent. As a result, the detected concentration of O-ethyl-O-methyl-S-propylphosphorothioate in samples is reported in this method with an estimated remark code. Based on the performance issue, two more compounds, disulfoton and ethion monoxon, also will be reported in this method with an estimated remark code. Estimated-value compounds, which are ?E-coded? in the data base, do not meet the performance criteria for unqualified quantification, but are retained in the method because the compounds are important owing to high use or potential environmental effects and because analytical performance has been consistent and reproducible.
Suggested Citation
Jha, V.K., Wydoski, D.S., 2003, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory-Determination of organophosphate pesticides in whole water by continuous liquid-liquid extraction and capillary-column gas chromatography with flame photometric detection: U.S. Geological Survey Water-Resources Investigations Report 2003-4139, vii, 26 p., https://doi.org/10.3133/wri034139.
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory-Determination of organophosphate pesticides in whole water by continuous liquid-liquid extraction and capillary-column gas chromatography with flame photometric detection |
| Series title | Water-Resources Investigations Report |
| Series number | 2003-4139 |
| DOI | 10.3133/wri034139 |
| Year Published | 2003 |
| Language | English |
| Contributing office(s) | National Water Quality Laboratory |
| Description | vii, 26 p. |