USGS-NWQL: O-1126-02: 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 - A Method Supplement for the Determination of Fipronil and Degradates in Water by Gas Chromatography/Mass Spectrome

Current Revision

2002

Media

WATER

Instrumentation

Gas Chromatography with Mass Spectrometry Detection

Method Subcategory

Organic

Method Source

USGS-NWQL

Citation

Madsen, J.E., Sandstrom, M.W., and Zaugg, S.D., 2003, Methods of Analysis of the U.S. Geological Survey National Water Quality Laboratory - A Method Supplement for the Determination of Fipronil and Degradates in Water by Gas Chromatography/Mass Spectrometry, U.S. Geological Survey Open-File Report 02-462, 16 p.

Brief Method Summary

This method adapts an analytical method created by the U.S. Geological Survey National Water Quality Laboratory in 1995 for the determination of a broad range of high-use pesticides typically found in filtered natural samples (see OFR 95-181).
Samples are collected and filtered onsite by using glass-fiber filters (0.7-um nominal pore diameter) as described by Sandstrom (1995). At the NWQL or at the field site, samples are prepared for analysis by C-18 solid-phase extraction (SPE), and compounds are determined by capillary-column quadrupole GC/MS using positive-ion electron-impact selected-ion monitoring (SIM). A detailed description of the method (including the equipment, reagents, sampling protocol, instrument calibration, SPE procedure, and sample analysis) is reported in Zaugg and others (1995).
A few substantial changes were made to the original method after its publication. The SPE elution solvent was changed from hexane-isopropanol to ethyl acetate, the upper concentration range was extended by dilution, acetochlor was added, and terbuthylazine was deleted as a surrogate.
Positive identification of a compound requires it to elute within 0.1 minute (+/- 6 seconds) of its expected retention-time window based on calibration standard injections. Furthermore, the maxima of the quantitation and two associated confirmation ion peaks should be within 0.01 minute of each other. The sample spectra and ion abundance ratios also are inspected to determine if they match the internal-standard reference compound.
After qualitative criteria are met, the compound concentration is determined by calculating the relative response of the quantitation ion to the corresponding internal-standard reference compound and comparing it with a seven-point calibration curve of relative responses equivalent to the range from 0.001 to 4.0 ug/L.
At least one fortified laboratory reagent-water spike sample at 0.1 ug/L and one laboratory reagent-water blank sample are analyze

Scope and Application

This report describes supplementary information for fipronil and four degradates in USGS method O-1126-95 (Zaugg and others, 1995). A description of these five compounds and method validation data for them are included.

Applicable Concentration Range

0.001-4.0

Interferences

Ions with high mass-to-charge (m/z) ratios were selected for identification and quantitation of fipronil and its degradates because of the high relative abundance and uniqueness of these ions. Fipronil sulfone and desulfinylfipronil amide coelute in this analysis. However, each of these compounds can be identified and quantitated by its unique ions. None of the ions in the fipronil sulfone spectrum are selected ions for desulfinylfipronil amide. The quantitation ion m/z 383 and confirmation ion m/z 385 for fipronil sulfone are not present in the desulfinylfipronil amide spectrum. The confirmation ion m/z 255 and monitor ion m/z 257 for fipronil sulfone are present in desulfinylfipronil amide. This coelution has not caused a problem in identifying fipronil sulfone because of the two unique selected ions for fipronil sulfone. Desulfinylfipronil amide has been detected only at low concentrations in samples analyzed to date (2002).
None of the compounds included in method O-1126-95 (Zaugg and others, 1995) interfere with any of the selected ions of fipronil or its degradates.

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

Maximum Holding Time

Relative Cost

Sample Preparation Methods

USGS-WRIR 95-4105

This method has 4 analytes associated with it.

Analyte	Detection Level	Bias	Precision	Spiking Level
Fipronil(120068-37-3) 5-Amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3-cyano-4-trifluoromethylsulfinylpyrazole Fipronil	0.003 ug/L	N/A	11.20 % RSD (SL)	0.01 ug/L
Fipronil sulfide(120067-83-6) 5-Amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3-cyano-4-trifluoromethylthiopyrazole Fipronil sulfide	0.002 ug/L	N/A	9.70 % RSD (SL)	0.01 ug/L
Fipronil sulfone(120068-36-2) 5-Amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3-cyano-4-trifluoromethylsulfonylpyrazole Fipronil sulfone	0.002 ug/L	N/A	11.30 % RSD (SL)	0.01 ug/L
Herbicides(E-12839) Herbicide formulations Herbicides	N/A	N/A	N/A

Precision Descriptor Notes:	Average percent recovery of all method compounds for short-term single-operator results in reagent-water samples fortified at 1.0 ug/L was 98 +/- 6 percent relative standard deviation. Average recovery for these compounds in the ground-water subsamples fortified at 1.0 ug/L was 88 +/- 4 percent relative standard deviation. Other precision information is available in USGS OFR 02-462. Bias and precision data for desulfinylfipronil and desulfinylfipronil amide were not included in the NEMI analyte table because they currently (2005) do not have assigned CAS numbers; see the method report for more information.
Detection Level Note:	Method detection limits (MDLs) were determined for this method using the procedures of the U.S. Environmental Protection Agency (1997). MDLs for desulfinylfipronil and desulfinylfipronil amide were not included in the NEMI analyte table because they currently (2005) do not have assigned CAS numbers; see the method report for their MDLs.

Precision Descriptor Notes:

Average percent recovery of all method compounds for short-term single-operator results in reagent-water samples fortified at 1.0 ug/L was 98 +/- 6 percent relative standard deviation. Average recovery for these compounds in the ground-water subsamples fortified at 1.0 ug/L was 88 +/- 4 percent relative standard deviation. Other precision information is available in USGS OFR 02-462. Bias and precision data for desulfinylfipronil and desulfinylfipronil amide were not included in the NEMI analyte table because they currently (2005) do not have assigned CAS numbers; see the method report for more information.

Detection Level Note:

Method detection limits (MDLs) were determined for this method using the procedures of the U.S. Environmental Protection Agency (1997). MDLs for desulfinylfipronil and desulfinylfipronil amide were not included in the NEMI analyte table because they currently (2005) do not have assigned CAS numbers; see the method report for their MDLs.

Revision	PDF/Link
2002

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USGS-NWQL: O-1126-02: Pesticides in Water by C-18 Solid-Phase Extraction and GC-MS

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