EPA Method 1658 Phenoxy-Acid Herbicides
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ID： |
9231E306F1B444DDB16249C1C44709A5 |
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文件大小(MB)： |
0.15 |
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页数： |
36 |
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文件格式： |
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日期： |
2008-2-26 |
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购买： |
文本摘录（文本识别可能有误，但文件阅览显示及打印正常，pdf文件可进行文字搜索定位）：
Method 1658,The Determination of,Phenoxy-Acid Herbicides in,Municipal and Industrial,Wastewater,Method 1658,The Determination of Phenoxy-Acid Herbicides in Municipal and,Industrial Wastewater,1. SCOPE AND APPLICATION,1.1 This method is designed to meet the survey requirements of the Environmental,Protection Agency (EPA). It is used to determine (1) the phenoxy-acid herbicides and,herbicide esters associated with the Clean Water Act, the Resource Conservation and,Recovery Act, and the Comprehensive Environmental Response, Compensation and,Liability Act; and (2) other compounds amenable to extraction and analysis by,automated, wide-bore capillary column gas chromatography (GC) with electron capture,or halogen-selective detectors.,1.2 The chemical compounds listed in Table 1 may be determined in waters, soils, sediments,and sludges by this method. This method should be applicable to other herbicides. The,quality assurance/quality control requirements in this method give the steps necessary,to determine this applicability.,1.3 When this method is applied to analysis of unfamiliar samples, compound identity must,be supported by at least one additional qualitative technique. This method describes,analytical conditions for a second gas chromatographic column that can be used to,confirm measurements made with the primary column. Gas chromatography mass,spectrometry (GC/MS) can be used to confirm compounds in extracts produced by this,method when analyte levels are sufficient.,1.4 The detection limit of this method is usually dependent on the level of interferences,rather than instrumental limitations. The limits in Table 2 typify the minimum quantity,that can be detected with no interferences present.,1.5 This method is for use by or under the supervision of analysts experienced in the use of,a gas chromatograph and in the interpretation of gas chromatographic data. Each,laboratory that uses this method must demonstrate the ability to generate acceptable,results using the procedure in Section 8.2.,2. SUMMARY OF METHOD,2.1 Extraction.,2.1.1 The percent solids content of a sample is determined.,2.1.2 Samples containing low solids: If the solids content is less than or equal to 1%,the sample is extracted directly using continuous extraction techniques. The pH,of a 1-L sample is raised to 12 to 13 to hydrolyze acid esters, and the sample is,extracted with methylene chloride to remove interferences. The pH is lowered,to less than 2 and the free acids are extracted with methylene chloride.,Method 1658,2.1.3 Samples containing greater than 1% solids.,2.1.3.1 Solids content 1 to 30%: The sample is diluted to 1% solids with reagent,water, homogenized ultrasonically, and extracted as a low-solids sample,(Section 2.1.2).,2.1.3.2 Solids content greater than 30%: The sample is placed in an extraction,bottle and approximately 1 L of basic (pH 12 to 13) water is added. The,bottle is tumbled for 18 hours. The water is removed and extracted as a,low-solids sample (Section 2.1.2).,2.2 Concentration and cleanup: The extract is dried over sodium sulfate, concentrated using,a Kuderna-Danish evaporator, cleaned up (if necessary) using gel permeation,chromatography (GPC) and concentrated to 5 or 10 mL (depending upon whether GPC,was or was not used).,2.3 Derivatization and cleanup: The acids in the extract are derivatized to form the methyl,esters. The solution containing the methyl esters is cleaned up (if necessary) using solidphase,extraction (SPE) and/or adsorption chromatography and reconcentrated to 5 or 10,mL.,2.4 Gas chromatography: A 1-μL aliquot of the extract is injected into the gas,chromatograph (GC). The derivatized acids are separated on a wide-bore, fused-silica,capillary column and are detected by an electron capture, microcoulometric, or,electrolytic conductivity detector.,2.5 Identification of a pollutant (qualitative analysis) is performed by comparing the GC,retention times of the compound on two dissimilar columns with the respective retention,times of an authentic standard. Compound identity is confirmed when the retention,times agree within their respective windows.,2.6 Quantitative analysis is performed by using an authentic standard to produce a,calibration factor or calibration curve, and using the calibration data to determine the,concentration of a pollutant in the extract. The concentration in the sample is calculated,using the sample weight or volume and the extract volume.,2.7 Quality is assured through reproducible calibration and testing of the extraction and GC,systems.,3. CONTAMINATION AND INTERFERENCES,3.1 Solvents, reagents, glassware, and other sample-processing har……
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