EPA Method 8151A

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EPA Method 8151A:
Chlorinated Herbicides by GC Using Methylation or Pentafluorobenzylation Derivatization

Summary:
Water, soil, and waste samples are extracted and then esterified. The derivatives are determined by gas chromatography with an electron capture detector.

Scope:
This method determines the concentration of chlorinated herbicides and related compounds in water, soil, and waste samples by using capillary-column gas chromatography with an electron capture detector.

Citation:
SW-846 Online: Test Methods for Evaluating Solid Waste, Physical/Chemical Methods

Interferences:
(A) Method interferences: Contaminants in solvents, reagents, glassware, and other sample processing hardware may lead to elevated baselines and/or other interferences in the gas chromatograms. Routine analysis of reagent blanks should be performed as a check for method interferences. Glassware must be scrupulously cleaned. After use, rinse the glassware with the last solvent that was used in it, wash with detergent and hot water, then with organic-free reagent water, and finish with a rinse of acetone and pesticide-quality hexane. Store in a clean environment and either invert the glassware or cap with aluminum foil. Before use, rinse with the next solvent to be used. Use only high purity reagents and solvents. Purification of solvents by distillation may be required.(B) Matrix interferences: May be contaminants that are coextracted from the sample. Organic acids, especially chlorinated acids, and phenols may interfere with the determination by methylation. The determination using pentafluorobenzylation is more sensitive and more prone to intereferences from organic acids or phenols than by methylation. Alkaline hydrolysis and extraction of the basic solution removes many chlorinated hydrocarbons and phthalate esters that may interfere with electron capture analysis. However, hydrolysis may result in the loss of dinoseb and the formation of aldol condensation products if any residual acetone remains from the extraction of solids. Herbicides react readily with alkaline substances and may be lost during analysis. Therefore, all glassware must be acid-rinsed and then rinsed to a constant pH with organic-free reagent water. In addition, sodium sulfate may be acidified. Sample extracts must be dry prior to analysis in order to avoid poor recoveries.(C) Refer to Method 8000.

QC Requirements:
Refer to Chapter One and Methods 3500 and 8000 for specific QC procedures. Procedures include: validation of sample preparation, introduction, and analysis, initial demonstration of proficiency, calibration verification, evaluation of retention times, analysis of method blanks, matrix spikes, duplicates, surrogates, and laboratory control samples.

Maximum Holding Time:
Aqueous samples - 7 days (sample), 40 days (extract). Solid samples - 14 days (sample), 40 (extract). Also, see SW-846 Chapter Four for information.

Media:
VARIOUS

Subcategory:
Organic

Concentration:
Not Available.

Sample Prep:
Method 3580

Precision:
Precision and accuracy are based on a single laboratory study using 7 - 8 determinations of spiked organic-free reagent water obtained from diazomethane derivatization.

Detection:
The EDL is defined as either the MDL or a concentration of analyte in a sample yielding a peak in the final extract with signal-to-noise ratio of approximately 5, whichever value is higher.

Revision Number:
Revision 1, December 1996

Test Description:
Chlorinated Herbicid

Report Number:
SW-846 Ch 4.3.1

Instrument used for this test:
GC