A method for addressing differences in concentrations of fipronil and three degradates obtained by two different laboratory methods

Open-File Report 2017-1056
National Water-Quality Assessment Project
By:  and 

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Abstract

In October 2012, the U.S. Geological Survey (USGS) began measuring the concentration of the pesticide fipronil and three of its degradates (desulfinylfipronil, fipronil sulfide, and fipronil sulfone) by a new laboratory method using direct aqueous-injection liquid chromatography tandem mass spectrometry (DAI LC–MS/MS). This method replaced the previous method—in use since 2002—that used gas chromatography/mass spectrometry (GC/MS). The performance of the two methods is not comparable for fipronil and the three degradates. Concentrations of these four chemical compounds determined by the DAI LC–MS/MS method are substantially lower than the GC/MS method. A method was developed to correct for the difference in concentrations obtained by the two laboratory methods based on a methods comparison field study done in 2012. Environmental and field matrix spike samples to be analyzed by both methods from 48 stream sites from across the United States were sampled approximately three times each for this study. These data were used to develop a relation between the two laboratory methods for each compound using regression analysis. The relations were used to calibrate data obtained by the older method to the new method in order to remove any biases attributable to differences in the methods. The coefficients of the equations obtained from the regressions were used to calibrate over 16,600 observations of fipronil, as well as the three degradates determined by the GC/MS method retrieved from the USGS National Water Information System. The calibrated values were then compared to over 7,800 observations of fipronil and to the three degradates determined by the DAI LC–MS/MS method also retrieved from the National Water Information System. The original and calibrated values from the GC/MS method, along with measures of uncertainty in the calibrated values and the original values from the DAI LC–MS/MS method, are provided in an accompanying data release.

Suggested Citation

Crawford, C.G., and Martin, J.D., 2017, A method for addressing differences in concentrations of fipronil and three degradates obtained by two different laboratory methods: U.S. Geological Survey Open-File Report 2017–1056, 26 p., https://doi.org/10.3133/ofr20171056.

ISSN: 2331-1258 (online)

Table of Contents

  • Foreword
  • Abstract
  • Introduction
  • Description of Laboratory Methods
  • Data Used for This Study
  • Differences Between the Laboratory Methods
  • Development of the Relation Between Methods
  • Application of the Regression Equations to NWIS Data
  • Limitations
  • Summary
  • References Cited

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title A method for addressing differences in concentrations of fipronil and three degradates obtained by two different laboratory methods
Series title Open-File Report
Series number 2017-1056
DOI 10.3133/ofr20171056
Year Published 2017
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) National Water Quality Assessment Program
Description Report: vi, 26 p.; Data Release
Online Only (Y/N) Y
Additional Online Files (Y/N) N