U.S. Geological Survey
Open-File Report 03-173
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Methods of Analysis by the U.S. Geological Survey Organic Geochemistry Research
Group—Determination of Acetamide Herbicides and Their Degradation Products
in Water Using Online Solid-Phase Extraction and Liquid Chromatography/Mass
Spectrometry
By E.A. Lee and A.P. Strahan
An analytical method for the determination of 6 acetamide herbicides (acetochlor,
alachlor, dimethenamid, flufenacet, metolachlor, and propachlor) and 16 of their
degradation products in natural water samples using solid-phase extraction and
liquid chromatography/mass spectrometry is described in this report. Special
consideration was given during the development of the method to prevent the
formation of degradation products during the analysis. Filtered water samples
were analyzed using octadecylsilane as the solid-phase extraction media on online
automated equipment followed by liquid chromatography/mass spectrometry. The
method uses only 10 milliliters of sample per injection. Three different water-sample
matrices, a reagent-water, a ground-water, and a surface-water sample spiked
at 0.10 and 1.0 microgram per liter, were analyzed to determine method performance.
Method detection limits ranged from 0.004 to 0.051 microgram per liter for
the parent acetamide herbicides and their degradation products. Mean recoveries
for the acetamide compounds in the ground- and surface-water samples ranged
from 62.3 to 117.4 percent. The secondary amide of acetochlor/metolachlor ethanesulfonic
acid (ESA) was recovered at an average rate of 43.5 percent. The mean recoveries
for propachlor and propachlor oxanilic acid (OXA) were next lowest, ranging
from 62.3 to 95.5 percent. Mean recoveries from reagent-water samples ranged
from 90.3 to 118.3 percent for all compounds. Overall the mean of the mean recoveries
of all compounds in the three matrices spiked at 0.10 and 1.0 microgram per
liter ranged from 89.9 to 100.7 percent, including the secondary amide of acetochlor/metolachlor
ESA and the propachlor compounds. The acetamide herbicides and their degradation
products are reported in concentrations ranging from 0.05 to 2.0 micrograms
per liter. The upper concentration limit is 2.0 micrograms per liter for all
compounds without dilution.
With the exception of the secondary amide of acetochlor/metolachlor ESA, good
precision and accuracy for the chloroacetanalide herbicides and their degradation
compounds were demonstrated for the method in buffered reagent water, ground
water, and surface water. The extraction method as used did not optimize the
recovery of the secondary amide of acetochlor/metolachlor ESA.
CONTENTS
Abstract
Introduction
Determination of Acetamide Herbicides and Their Degradation Products in Water
Method of Analysis
Application
Summary of Method
Interferences
Apparatus and Instrumentation
Reagents and Consumable Materials
Sampling Methods
Standards
Safety Precautions
Evaluation of Instrument Performance
High-Performance Liquid Chromatograph and Diode Array Detector Performance
Mass Spectrometer Performance
Calibration
Alternate Calibration
Extraction Efficiency
Analytical Procedure
Calculation of Results
Qualitative Identification
Quantitation
Alternate Quantitation
Reporting of Results
Method Performance
Corrections for Background Concentrations
Method Detection Limits
Mean Recovery
Discussion
Conclusions
References Cited
Lee, E.A. and Strahan, A.P., 2003, Methods of Analysis by the U.S.
Geological Survey Organic Geochemistry Research Group•Determination of acetamide
herbicides and their degradation products in water using online solid-phase
extraction and liquid chromatography/mass spectrometry: U.S. Geological Survey
Open-File Report 03-173, 17 p.
For additional information about the Organic Geochemistry Research Group, please visit
their Web site at:
http://ks.water.usgs.gov/studies/reslab/
For additional information contact:
Betty Scribner
U.S. Geological Survey
4821 Quail Crest Place
Lawrence, KS 66049-3839
Telephone: (785) 832-3564
Fax: (785) 832-3500
Email: scribner@usgs.gov
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