EPA Method 1659 Dazomet
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ID： |
577495F632124BDD9FCB94DEE93BA852 |
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文件大小(MB)： |
0.05 |
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页数： |
17 |
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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 1659,The Determination of Dazomet,in Municipal and Industrial,Wastewater,Method 1659,The Determination of Dazomet in Municipal and,Industrial Wastewater,1. SCOPE AND APPLICATION,1.1 This method covers the determination of dazomet (CAS 533-74-4) by base hydrolysis to,methyl isothiocyanate (MITC; CAS 556-61-6) and subsequent determination of MITC by,wide bore, fused-silica column gas chromatography (GC) with a nitrogen-phosphorus,detector (NPD).,1.2 This method is designed to meet the monitoring requirements of the U.S. Environmental,Protection Agency under the Clean Water Act at 40 CFR Part 455. Any modification of,this method beyond those expressly permitted shall be considered a major modification,subject to application and approval of alternative test procedures under 40 CFR 136.4 and,136.5.,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 dazomet in extracts produced by this,method when the level is sufficient.,1.4 The detection limit of this method is usually dependent on the level of interferences,rather than instrumental limitations. The limit in Table 1 typifies 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 A 50-mL sample is adjusted to pH 10 to 12 and allowed to stand for 3 hours to hydrolyze,dazomet to MITC. After hydrolysis, the sample is saturated with salt and extracted with,2.5 mL of ethyl acetate. Gas chromatographic conditions are described that permit the,separation and measurement of MITC in the extract by wide-bore, fused-silica capillary,column with nitrogen-phosphorus detector (GC/NPD).,2.2 Identification of MITC (qualitative analysis) is performed by comparing the GC retention,time of the MITC 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.,Method 1659,2.3 Quantitative analysis is performed using an authentic standard of MITC to produce a,calibration factor or calibration curve, and using the calibration data to determine the,concentration of MITC in the extract. The concentration in the sample is calculated using,the sample volume, the extract volume, and a factor to convert MITC to dazomet.,2.4 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 hardware may yield artifacts,and/or elevated baselines causing misinterpretation of chromatograms. All materials,used in the analysis shall be demonstrated to be free from interferences under the,conditions of analysis by running method blanks as described in Section 8.4.,3.2 Glassware and, where possible, reagents are cleaned by rinsing with and baking at 450°C,for a minimum of 1 hour in a muffle furnace or kiln. Some thermally stable materials,such as PCBs, may not be eliminated by this treatment and thorough rinsing with acetone,and pesticide-quality hexane may be required.,3.3 Specific selection of reagents and purification of solvents by distillation in all-glass,systems may be required.,3.4 Interferences coextracted from samples will vary considerably from source to source,depending on the diversity of the site being sampled.,4. SAFETY,4.1 The toxicity or carcinogenicity of each compound or reagent used in this method has not,been precisely determined; however, each chemical compound should be treated as a,potential health hazard. Exposure to these compounds should be reduced to the lowest,possible level. The laboratory is responsible for maintaining a current awareness file of,OSHA regulations regarding the safe handling of the chemicals specified in this method.,A reference file of material handling sheets should also be made available to all personnel,involved in these analyses. Additional information on laboratory safety can be found in,References 1 through 3.,4.2 Unknown samples may contain high concentrations of volatile toxic compounds. Sample,conta……
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