EPA-TSC/NERL: 507:  Pesticides in Water Using GCNPD

  • Summary
  • Analytes
  • Revision
  • Data and Sites
Official Method Name
Determination of Nitrogen- and Phosphorus-Containing Pesticides in Water by Gas Chromatography with a Nitrogen-Phosphorus Detector
Current Revision
Revision 2.1, 1995
Gas Chromatography with Nitrogen - Phosphorus Detection
Method Subcategory
Method Source
  Methods for the Determination of Organic Compounds in Drinking Water - Supplement III (EPA/600/R-95-131)
Brief Method Summary
A 1 L sample is extracted with methylene chloride by shaking in a separatory funnel or mechanical tumbling in a bottle. The methylene chloride extract is isolated, dried, and concentrated to a volume of 5 mL during a solvent exchange to methyl tert-butyl ether (MTBE). The concentrations of pesticides in the extract are measured using capillary column gas chromatography (GC) system equipped with a nitrogen-phosphorus detector (NPD).
Scope and Application
This method determines certain nitrogen- and phosphorus-containing pesticides in ground water and finished drinking water.
Applicable Concentration Range
Ranges differ for each analyte depending on matrix and instrumentation.

(A) Glassware contamination: Thoroughly clean glassware, including baking or solvent rinse.

(B) Reagent contamination: Use high purity reagents.

(C) Contamination from sample carryover: Rinsing apparatus with water and purging equipment between analyses can minimize contamination.

(D) Matrix interferences: Matrix interferences may caused by contaminants that are coextracted from the sample.

(E) Solvents: The same solvent must be used to prepare samples and standards to make sure responses are comparable.

Quality Control Requirements
Initial demonstration of laboratory capability (includes analysis of standards), followed by surrogate recoveries, laboratory reagent blanks (LRBs), laboratory fortified samples, laboratory fortified blanks (LFBs), and QC performance samples. A method detection limit (MDL) must also be determined for each analyte.
Sample Handling

Grab samples must be collected in amber glass containers. Conventional sampling practices should be followed; however, the bottle must not be pre-rinsed with sample prior to collection. Add 80 mg of sodium thiosulfate per liter to the sample bottle at the sampling site or in the laboratory prior to shipping to the sampling site if residual chlorine is present. After sample is collected, seal the bottle and swirl until the sodium thiosulfate is dissolved. Samples must be iced or refrigerated at 4oC free from light from the time of collection until extraction.

NOTE: Samples analyzed for the following analytes must be extracted immediately: disulfoton sulfoxide, diazinon, pronamide, and terbufos. Samples analyzed for the following analytes exhibited recoveries of less than 60% after 14 days: carboxin, EPTC, fluridone, metolachlor, napropamide, tebuthiuron, and terbacil.

Maximum Holding Time
14 days generally (see Sampling Handling for exceptions).
Relative Cost
$201 to $400
Sample Preparation Methods