EPA METHOD 508 水含氯杀虫剂的测定 电子捕获检测器 气相色谱法

508-1 METHOD 508 DETERMINATION OF CHLORINATED PESTICIDES IN WATER BY GAS CHROMATOGRAPHY WITH AN ELECTRON CAPTURE DETECTOR Revision 3.1 Edited by J.W. Munch (1995) J. J. Lichtenberg, J. E. Longbottom, T. A. Bellar, J. W. Eichelberger, and R. C. Dressman - EPA 600/4-81-053, Revision 1.0 (1981) D. J. Munch (USEPA, Office of Water) and T. Engel (Battelle Columbus Laboratories) - National Pesticide Survey Method 2, Revision 2.0 (1987) R. L. Graves - Method 508, Revision 3.0 (1989) NATIONAL EXPOSURE RESEARCH LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268 508-2 METHOD 508 DETERMINATION OF CHLORINATED PESTICIDES IN WATER BY GAS CHROMATOGRAPHY WITH AN ELECTRON CAPTURE DETECTOR 1.0 SCOPE AND APPLICATION 1.1 This is a gas chromatographic (GC) method applicable to the determination of certain chlorinated pesticides in groundwater and finished drinking water. The following compounds can be determined using this method: Analyte Registry Number Chemical Abstract Services Aldrin 309-00-2 Atrazine 5103-71-9 Chlordane-alpha 5103-74-2 Chlordane-gamma 2675-77-6 Chlorneb 501-15-6 Chlorobenzilate 2921-88-2a Chlorothalonil 1861-32-1 DCPA 72-54-8 4,4'-DDD 72-55-9 4,4'-DDE 50-29-3 4,4'-DDT 60-57-1 Endosulfan I 959-98-8 Endosulfan II 33213-65-9 Endosulfan Sulfate 1031-07-8 Endrin 72-20-8 Endrin Aldehyde 7421-93-4 Etridiazole 2593-15-9 HCH-alpha 319-84-6 HCH-beta 319-85-7 HCH-delta 319-86-8a HCH-gamma (Lindane) 58-89-9 Heptachlor 76-44-8 Heptachlor Epoxide 1024-57-3 Hexachlorobenzene 118-74-1 Methoxychlor 72-43-5 cis-Permethrin 61949-76-6 trans-Permethrin 61949-77-7 Propachlor 1918-16-7 Trifuluralin 1582-09-8 Aroclor 1016* 12674-11-2 Aroclor 1221* 11104-28-2 Aroclor 1232* 11141-16-5 Analyte Registry Number Chemical Abstract Services 508-3 Aroclor 1242* 53469-21-9 Aroclor 1248* 12672-29-6 Aroclor 1254* 11097-69-1 Aroclor 1260* 11096-82-5 Toxaphene* 8001-35-2 Chlordane* 57-74-9 *The extraction conditions of this method are comparable to USEPA Method 608, which does measure the multicomponent constituents: commercial polychlorinated biphenyl (PCB) mixtures (Aroclors), toxaphene, and chlordane. The extract derived from this procedure may be analyzed for these constituents by using the GC conditions prescribed in either Method 608 (packed column) or Methods 505, 508.1, or 525.2 (capillary column) . The columns used in this method may well be adequate,1 however, no data were collected for these constituents during methods development. Chlorbenzilate and HCH-delta are only qualitatively identified and are nota quantitated because control over precision has not been accomplished. 1.2 This method has been validated in a single laboratory and estimated detection limits (EDLs) and method detection limits (MDLs) have been determined for the analytes above (Section 13.0). Observed detection limits may vary between waters, depending upon the nature of interferences in the sample matrix and the specific instrumentation used. 1.3 This method is restricted to use by or under the supervision of analysts experienced in the use of GC and in the interpretation of gas chromatograms. Each analyst must demonstrate the ability to generate acceptable results with this method using the procedure described in Section 9.3. 1.4 Analytes that are not separated chromatographically, i.e., analytes which have very similar retention times, cannot be individually identified and measured in the same calibration mixture or water sample unless an alternative technique for identification and quantitation exist (Section 11.5). 1.5 When this method is used to analyze unfamiliar samples for any or all of the analytes above, analyte identifications must be confirmed by at least one additional qualitative technique. 2.0 SUMMARY OF METHOD 2.1 A measured volume of sample of approximately 1 L is solvent extracted with methylene chloride by shaking in a separatory funnel or mechanical tumbling in a bottle. The methylene chloride extract is isolated, dried and concentrated to a 508-4 volume of 5 mL after solvent substitution with methyl tert-butyl ether (MTBE). Chroma-tographic conditions are described which permit the separation and measurement of the analytes in the extract by capillary column GC with an electron capture detector (ECD). 3.0 DEFINITIONS 3.1 Internal Standard (IS) -- A pure analyte(s) added to a solution in known amount(s) and used to measure the relative responses of other method analytes and surrogates that are components of the same solution. The internal standard must be an analyte that is not a sample component. 3.2 Surrogate Analyte (SA) -- A pure analyte(s), which is extremely unlikely to be found in any sample, and which is added to a sample aliquot in known amount(s) before extraction and is measured with the same procedures used to measure other sample components. The purpose of a surrogate analyte is to monitor method performance with each sample. 3.3 Laboratory Duplicates (LD1 and LD2) -- Two sample aliquots taken in the analytical laboratory and analyzed separately with identical procedures. Analyses of LD1 and LD2 give a measure of the precision associated with laboratory procedures, but not with sample collection, preservation, or storage procedures. 3.4 Field Duplicates (FD1 and FD2) -- Two separate samples collected at the same time and place under identical circumstances and treated exactly the same throughout field and laboratory procedures. Analyses of FD1 and FD2 give a measure of the precision associated with sample collection, preservation and storage, as well as with laboratory procedures. 3.5 Laboratory Reagent Blank (LRB) -- An aliquot of reagent water that is treated exactly as a sample including exposure to all glassware, equipment, solvents, reagents, internal standards, and surrogates that are used with other samples. The LRB is used to determine if method analytes or other interferences are present in the laboratory environment, the reagents, or the apparatus. 3.6 Field Reagent Blank (FRB) -- Reagent water placed in a sample container in the laboratory and treated as a sample in all respects, including exposure to sampling site conditions, storage, preservation and all analytical procedures. The purpose of the FRB is to determine if method analytes or other interferences are present in the field environment. 3.7 Laboratory Performance Check Solution (LPC) -- A solution of method analytes, surrogate compounds, and internal standards used to evaluate the performance of the instrument system with respect to a defined set of method criteria. 3.8 Laboratory Fortified Blank (LFB) -- An aliquot of reagent water to which known quantities of the method analytes are added in the laboratory. The LFB is analyzed exactly like a sample, and its purpose is to determine whether the 508-5 methodology is in control, and whether the laboratory is capable of making accurate and precise measurements at the required method detection limit. 3.9 Laboratory Fortified Sample Matrix (LFM) -- An aliquot of an environmental sample to which known quantities of the method analytes are added in the laboratory. The LFM is analyzed exactly like a sample, and its purpose is to determine whether the sample matrix contributes bias to the analytical results. The background concentrations of the analytes in the sample matrix must be determined in a separate aliquot and the measured values in the LFM corrected for background concentrations. 3.10 Stock Standard Solution -- A concentrated solution containing a single certified standard that is a method analyte, or a concentrated solution of a single analyte prepared in the laboratory with an assayed reference compound. Stock standard solutions are used to prepare primary dilution standards. 3.11 Primary Dilution Standard Solution (PDS) -- A solution of several analytes prepared in the laboratory from stock standard solutions and diluted as needed to prepare calibration solutions and other needed analyte solutions. 3.12 Calibration Standard (CAL) -- A solution prepared from the primary dilution standard solution and stock standard solutions of the internal standards and surrogate analytes. The CAL solutions are used to calibrate the instrument response with respect to analyte concentration. 3.13 Quality Control Sample (QCS) -- a sample matrix containing method analytes or a solution of method analytes in a water miscible solvent which is used to fortify reagent water or environmental samples. The QCS is obtained from a source external to the laboratory, and is used to check laboratory performance with externally prepared test materials. 4.0 INTERFERENCES 4.1 Method interferences may be caused by contaminants in solvents, reagents, glassware and other sample processing apparatus that lead to discrete artifacts or elevated baselines in gas chromatograms. All reagents and apparatus must be routinely demonstrated to be free from interferences under the conditions of the analysis by running laboratory reagent blanks as described in Section 9.2. 4.1.1 Glassware must be scrupulously cleaned . Clean all glass-ware as soon as2 possible after use by thoroughly rinsing with the last solvent used in it. Follow by washing with hot water and detergent and thorough rinsing with tap and reagent water. Drain dry, and heat in an oven or muffle furnace at 400°C for one hour. Do not heat volumetric glassware. Thermally stable materials such as PCBs might not be eliminated by this treatment. Thorough rinsing with acetone may be substituted for the heating. After drying and cooling, seal and store glassware in a clean 508-6 environment to prevent any accumulation of dust or other contaminants. Store inverted or capped with aluminum foil. 4.1.2 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. Warning: When a solvent is purified, stabilizers added by the manufacturer are removed thus potentially making the solvent hazardous. Also, when a solvent is purified, preservatives added by the manufacturer are removed thus potentially reducing the shelf-life. 4.2 Interferences by phthalate esters can pose a major problem in pesti-cide analysis when using the electron capture detector. These compounds generally appear in the chromatogram as large peaks. Common flexible plastics contain varying amounts of phthalates that are easily extracted or leached during laboratory operations. Cross contamination of clean glassware routinely occurs when plastics are handled during extraction steps, especially when solvent-wetted surfaces are handled. Interferences from phthalates can best be minimized by avoiding the use of plastics in the laboratory. Exhaustive cleanup of reagents and glassware may be required to eliminate background phthalate contamination. 4.3 Interfering contamination may occur when a sample containing low concentrations of analytes is analyzed immediately following a sample containing relatively high concentrations of analytes. Between-sample rinsing of the sample syringe and associated equipment with MTBE can minimize sample cross contamination. After analysis of a sample containing high concentrations of analytes, one or more injections of MTBE should be made to ensure that accurate values are obtained for the next sample. 4.4 Matrix interferences may be caused by contaminants that are coextracted from the sample. Also, note that all the analytes listed in the Scope and Application Section are not resolved from each other on any one column, i.e., one analyte of interest may be an interferant for another analyte of interest. The extent of matrix interferences will vary considerably from source to source, depending upon the water sampled. Analyte identifications should be confirmed (Section 11.5). 4.5 It is important that samples and standards be contained in the same solvent, i.e., the solvent for final working standards must be the same as the final solvent used in sample preparation. If this is not the case, chromatographic comparability of standards to sample may be affected. 508-7 5.0 SAFETY 5.1 The toxicity or carcinogenicity of each reagent used in this method has not been precisely defined; however, each chemical compound must be treated as a potential health hazard. Accordingly, exposure to these chemicals must 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 safety data sheets should also be made available to all personnel involved in the chemical analysis. Additional references to laboratory safety are available and have been identified for the information of the analyst.3-5 Warning: When a solvent is purified stabilizers added by the manufacturer are removed thus potentially making the solvent hazardous. 6.0 EQUIPMENT AND SUPPLIES (All specifications are suggested. Catalog numbers are included for illustration only.) 6.1 Sample Bottle -- Borosilicate, 1 L volume with graduations (Wheaton Media/Lab bottle 219820 or equivalent), fitted with screw caps lined with TFE-fluorocarbon. Protect samples from light. Amber bottles may be used. The container must be washed and dried as described in Section 4.1.1 before use to minimize contamination. Cap liners are cut to fit from sheets (Pierce Catalog No. 012736) and extracted with methanol overnight prior to use. 6.2 Glassware 6.2.1 Separatory Funnel -- 2000 mL, with TFE-fluorocarbon stopcock, ground glass or TFE-fluorocarbon stopper. 6.2.2 Tumbler Bottle -- 1.7 L (Wheaton Roller Culture Vessel or equivalent), with TFE-fluorocarbon lined screw cap. Cap liners are cut to fit from sheets (Pierce Catalog No. 012736) and extracted with methanol overnight prior to use. 6.2.3 Flask, Erlenmeyer -- 500 mL. 6.2.4 Concentrator tube, Kuderna-Danish (K-D) -- 10 mL or 25 mL, graduated (Kontes K-570050-1025 or K-570050-2525 or equivalent). Calibration must be checked at the volumes employed in the test. Ground glass stoppers are used to prevent evaporation of extracts. 6.2.5 Evaporative flask, K-D -- 500 mL (Kontes K-570001-0500 or equivalent). Attach to concentrator tube with springs. 6.2.6 Snyder column, K-D -- Three-ball macro (Kontes K-503000-0121 or equivalent). 508-8 6.2.7 Snyder column, K-D -- Two-ball micro (Kontes K-569001-0219 or equivalent). 6.2.8 Vials -- Glass, 5-10 mL capacity with TFE-fluorocarbon lined screw cap. 6.3 Separatory Funnel Shaker -- Capable of holding 2 L separatory funnels and shaking them with rocking motion to achieve thorough mixing of separatory funnel contents (available from Eberbach Co. in Ann Arbor, MI or other suppliers). 6.4 Tumbler -- Capable of holding tumbler bottles and tumbling them end-over-end at 30 turns/min. (Associated Design and Mfg. Co., Alexandria, VA or other suppliers.). 6.5 Boiling Stones Carborundum -- #12 granules (Arthur H. Thomas Co. #1590-033 or equivalent). Heat at 400°C for 30 minutes prior to use. Cool and store in a desiccator. 6.6 Water Bath -- Heated, capable of temperature control (±2°C). The bath should be used in a hood. 6.7 Balance -- Analytical, capable of accurately weighing to the nearest 0.0001 g. 6.8 Gas Chromatograph -- Analytical system complete with temperature programmable GC suitable for use with capillary columns and all required accessories including syringes, analytical columns, gases, detector and stripchart recorder. A data system is recommended for measuring peak areas. Table 1 lists retention times observed for method analytes using the columns and analytical conditions described below. 6.8.1 Column 1 (primary column) - 30 m long x 0.25 mm I.D. DB-5 bonded fused silica column, 0.25 µm film thickness (J&W Scientific). Helium carrier gas flow is established at 30 cm/sec linear velocity and oven temperature is programmed from 60-300°C at 4°C/min. Data presented in this method were obtained using this column. The injection volume was 2 µL splitless mode with a 45 second delay. The injector temperature was 250°C and the detector temperature was 320°C. Column performance criteria are presented in Table 4 (See Section 9.9). Alternative columns may be used in accordance with the provisions described in Section 9.4. 6.8.2 Column 2 (alternative column) - 30 m long x 0.25 mm I.D.DB-1701 bonded fused silica column, 0.25 µm film thickness (J&W Scientific). Helium carrier gas flow is established at 30 cm/sec. linear velocity and oven temperature is programmed from 60-300°C at 4°C/min. 6.8.3 Detector, Electron Capture -- This detector has proven effective in the analysis of fortified reagent and artificial ground waters. 508-9 7.0 REAGENTS AND STANDARDS Warning: When a solvent is purified, stabilizers added by the manufacturer are removed thus potentially making the solvent hazardous. Also, when a solvent is purified, preservatives added by the manufacturer are removed thus potentially reducing the shelf-life. 7.1 Acetone, Methylene Chloride, MTBE -- Distilled-in-glass quality or equivalent. 7.2 Phosphate Buffer, pH 7 -- Prepare by mixing 29.6 mL 0.1 N HCl and 50 mL 0.1 M dipotassium phosphate. 7.3 Sodium Chloride, Crystal, ACS Grade -- Heat treat in a shallow tray at 400°C for a minimum of four hours to remove interfering organic substances. Store in a glass bottle (not plastic) to avoid phthalate contamination. 7.4 Sodium Sulfate, Granular, Anhydrous, ACS Grade -- Heat treat in a shallow tray at 450°C for a minimum of four hours to remove interfering organic substances. Store in a glass bottle (not plastic) to avoid phthalate contamination. 7.5 Sodium Thiosulfate, Granular, Anhydrous, ACS Grade. 7.6 Pentachloronitrobenzene (PCNB) 98% Purity -- For use as internal standard. 7.7 Decachlorobiphenyl (DCB) 96% Purity -- For use as surrogate standard (available from Chemicals Procurement Inc.). 7.8 Mercuric Chloride, ACS Grade -- For use as a bactericide (optional). 7.9 Reagent Water -- Reagent water is defined as water that is reasonably free of contamination that would prevent the determination of any analyte of interest. Reagent water used to generate the validation data in this method was distilled water obtained from the Magnetic Springs Water Co., Columbus, Ohio. 7.10 Stock Standard Solutions (1.00 µg/µL) -- Stock standard solutions may be purchased as certified solutions or prepared from pure standard materials using the following procedure: 7.10.1 Prepare stock standard solutions by accurately weighing approximately 0.0100 g of pure material. Dissolve the material in MTBE and dilute to volume in a 10 mL volumetric flask. Larger volumes may be used at the convenience of the analyst. If compound purity is certified at 96% or greater, the weight may be used without correction to calculate the concentration of the stock standard. Commercially prepared stock standards may be used at any concentration if they are certified by the manufacturer or by an independent source. 508-10 7.10.2 Transfer the stock standard solutions into TFE-fluoro-carbon-sealed screw cap amber vials. Store at room temper-ature and protect from light. 7.10.3 Stock standard solutions should be replaced after two months or sooner if comparison with laboratory fortified blanks, or QC samples indicate a problem. 7.11 Internal Standard Solution -- Prepare an internal standard fortifying solution by accurately weighing approximately 0.0010 g of pure PCNB. Dissolve the PCNB in MTBE and dilute to volume in a 10 mL volumetric flask. Transfer the internal standard solution to a TFE-fluorocarbon-sealed screw cap bottle and store at room temperature. Addition of 5 µL of the internal standard fortifying solution to 5 mL of sample extract r