USGS-NWQL: O-1126-95:  Pesticides in Water by C-18 Solid-Phase Extraction and GC-MS

  • Summary
  • Analytes
  • Revision
  • Data and Sites
Official Method Name
 Methods of Analysis by the U.S. Geological Survey National Water Quality Laboratory - Determination of Pesticides in Water by C-18 SPE and Capillary-Column GC-MS with Select-Ion Monitoring
Current Revision
1995
Media
 WATER
Instrumentation
 Gas Chromatography with Mass Spectrometry Detection
Method Subcategory
 Organic
Method Source
  USGS-NWQL
Citation
  Zaugg, S.D., Sandstrom, M.W., Smith, S.G., and Fehlberg, K.M., 1995, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory--Determination of pesticides in water by C-18 solid-phase extraction and capillary-column gas chromatography/mass spectrometry with selected-ion monitoring: U.S. Geological Survey Open-File Report 95-181.
Brief Method Summary
 The samples are filtered at the collection site using glass-fibre filters with 0.7 um pore diameter to remove suspended particulate matter. Filtered water samples are pumped through disposable polypropylene SPE columns containing porous silica coated with an octadecyl (C-18) phase that is chemically bonded to the surface of the silica. The SPE columns are dried using a gentle stream of carbon dioxide or nitrogen gas to remove residual water. The absorbed pesticides and metabolites are then removed from the SPE columns by elution with a hexane-isopropanol (3:1) solution. The eluant is further evaporated by a gentle stream of nitrogen. Extracts of the eluant are analyzed by capillary-column GC-MS operated in the SIM (Selected Ion Monitoring) mode.
Acetochlor was added to the suite of analytes for this method in 1996. The methodology remains the same; however, this addition is documented in Lindley, C.E. and others, 1996, Journal of AOAC International, v.79, no.4.
Scope and Application
 This method is suitable for the determination of low-level concentrations (in ug/L and ng/L) of pesticides and pesticide metabolites in natural-water samples. The method is applicable to pesticides and metabolites that are efficiently partitioned from the water phase onto an octadecyl (C-18) organic phase that is chemically bonded to an inorganic matrix and that are sufficiently volatile and thermally stable for gas chromatography. Suspended particulate matter is removed by filtration. This method is suitable only for dissolved-phase pesticides and metabolites.
Applicable Concentration Range
 0.001 - 4.0 (undiluted)
Interferences
 Organic compunds having gas-chromatographic retention times and characteristic ions with a mass identical to those of the pesticides and metabolites of interest may interfere.
Quality Control Requirements
 Quality-control samples area analyzed at a minimum of one in every ten samples. These QC samples include at least one of each of the following: blanks, quality control samples, third party check solutions, replicates, and spikes. Correlation coefficients for calibration curves must be at least 0.99. QC samples must fall within 1.5 standard deviations of the mean value. If all of the data-acceptance criteria in the SOPs are met, then the analytical data are acceptable.
Sample Handling
 This schedule consumes the entire sample. Description: 1 L Glass bottle, amber bottle baked at 450oC by laboratory - SOME GCCs should be filtered CHECK METHOD REFERENCE OR EMAIL LABHELP@USGS.GOV FOR FILTERING REQUIREMENTS. Treatment and Preservation: DO NOT RINSE BOTTLE. Do not fill bottle beyond shoulder, reagents must be added to the sample at the NWQL before analyses. Chill sample and maintain at 4oC, ship immediately.
Maximum Holding Time
 7 days from arrival at the NWQL
Relative Cost
 $201 to $400
Sample Preparation Methods
 USGS-WRIR 95-4105
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