EPA Method 625 Semivolatile Organic Compounds by Isotope Dilution GC_MS
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ID： |
4FD74CEEE8AA4FDBAA9E1F33DB9270E8 |
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文件大小(MB)： |
0.46 |
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页数： |
41 |
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文件格式： |
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日期： |
2003-1-16 |
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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）：
APPENDIX A TO PART 136,METHODS FOR ORGANIC CHEMICAL ANALYSIS OF MUNICIPAL AND,INDUSTRIAL WASTEWATER,METHOD 625—BASE/NEUTRALS AND ACIDS,1. Scope and Application,1.1 This method covers the determination of a number of organic compounds that are,partitioned into an organic solvent and are amenable to gas chromatography. The,parameters listed in Tables 1 and 2 may be qualitatively and quantitatively,determined using this method.,1.2 The method may be extended to include the parameters listed in Table 3. Benzidine,can be subject to oxidative losses during solvent concentration. Under the alkaline,conditions of the extraction step, "-BHC, (-BHC, endosulfan I and II, and endrin are,subject to decomposition. Hexachlorocyclopentadiene is subject to thermal,decomposition in the inlet of the gas chromatograph, chemical reaction in acetone,solution, and photochemical decomposition. N-nitrosodimethylamine is difficult to,separate from the solvent under the chromatographic conditions described.,N-nitrosodiphenylamine decomposes in the gas chromatographic inlet and cannot be,separated from diphenylamine. The preferred method for each of these parameters is,listed in Table 3.,1.3 This is a gas chromatographic/mass spectrometry (GC/MS) method2,14 applicable to,the determination of the compounds listed in Tables 1, 2, and 3 in municipal and,industrial discharges as provided under 40 CFR Part 136.1.,1.4 The method detection limit (MDL, defined in Section 16.1)1 for each parameter is,listed in Tables 4 and 5. The MDL for a specific wastewater may differ from those,listed, depending upon the nature of interferences in the sample matrix.,1.5 Any modification to this method, beyond those expressly permitted, shall be,considered as a major modification subject to application and approval of alternate,test procedures under 40 CFR Parts 136.4 and 136.5. Depending upon the nature of,the modification and the extent of intended use, the applicant may be required to,demonstrate that the modifications will produce equivalent results when applied to,relevant wastewaters.,1.6 This method is restricted to use by or under the supervision of analysts experienced,in the use of a gas chromatograph/mass spectrometer and in the interpretation of,mass spectra. Each analyst must demonstrate the ability to generate acceptable results,with this method using the procedure described in Section 8.2.,2. Summary of Method,2.1 A measured volume of sample, approximately 1 L, is serially extracted with,methylene chloride at a pH greater than 11 and again at a pH less than 2 using a,separatory funnel or a continuous extractor.2 The methylene chloride extract is dried,concentrated to a volume of 1 mL, and analyzed by GC/MS. Qualitative,identification of the parameters in the extract is performed using the retention time,and the relative abundance of three characteristic masses (m/z). Quantitative analysis,is performed using internal standard techniques with a single characteristic m/z.,3. Interferences,3.1 Method interferences may be caused by contaminants in solvents, reagents, glassware,and other sample processing hardware that lead to discrete artifacts and/or elevated,baselines in the total ion current profiles. All of these materials must be routinely,demonstrated to be free from interferences under the conditions of the analysis by,running laboratory reagent blanks as described in Section 8.1.3.,3.1.1 Glassware must be scrupulously cleaned.3 Clean all glassware as soon as,possible after use by rinsing with the last solvent used in it. Solvent rinsing,should be followed by detergent washing with hot water, and rinses with tap,water and distilled water. The glassware should then be drained dry, and,heated in a muffle furnace at 400°C for 15-30 minutes. Some thermally stable,materials, such as PCBs, may not be eliminated by this treatment. Solvent,rinses with acetone and pesticide quality hexane may be substituted for the,muffle furnace heating. Thorough rinsing with such solvents usually,eliminates PCB interference. Volumetric ware should not be heated in a muffle,furnace. After drying and cooling, glassware should be sealed and stored in a,clean environment to prevent any accumulation of dust or other contaminants.,Store inverted or capped with aluminum foil.,3.1.2 The use of high purity reagents and solvents helps to minimize interference,problems. Purification of solvents by distillation in all-glass systems may be,required.,3.2 Matrix interferences may be caused by contaminants that are co-extracted from the,sample. The extent of matrix interferences will vary considerably from source to,source, depending upon the natu……
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