EPA METHOD 508.1 含氯杀虫剂、除草剂和有机氯化合物的测定 液固萃取 电子捕获检测器 气相色谱法

508.1-1 METHOD 508.1 DETERMINATION OF CHLORINATED PESTICIDES, HERBICIDES, AND ORGANOHALIDES BY LIQUID-SOLID EXTRACTION AND ELECTRON CAPTURE GAS CHROMATOGRAPHY Revision 2.0 James W. Eichelberger - Revision 1.0, 1994 Jean W. Munch - Revision 2.0, 1995 NATIONAL EXPOSURE RESEARCH LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268 508.1-2 METHOD 508.1 DETERMINATION OF CHLORINATED PESTICIDES, HERBICIDES, AND ORGANOHALIDES IN WATER USING LIQUID-SOLID EXTRACTION AND ELECTRON CAPTURE GAS CHROMATOGRAPHY 1.0 SCOPE AND APPLICATION 1.1 This method utilizes disk liquid-solid extraction and gas chromatography with an electron capture detector to determine twenty nine chlorinated pesticides, three herbicides, and four organohalides in drinking water, ground water, and drinking water in any treatment stage. Liquid solid extraction cartridges may also be used to carry out sample extractions. Single laboratory accuracy, precision, and method detection limit data have been determined for the following compounds: Analyte Registry Number Chemical Abstract Services Alachlor 15972-60-8 Aldrin 309-00-2 Atrazine 1912-24-9 Butachlor 23184-66-9 Chlordane-alpha 5103-71-9 Chlordane-gamma 5103-74-2 Chloroneb 2675-77-6 Chlorbenzilate 510-15-6 Chlorthalonil 1897-45-6 Cyanazine 21725-46-2 DCPA 1861-32-1 4,4'-DDD 72-54-8 4,4'-DDE 72-55-9 4,4'-DDT 50-29-3 Dieldrin 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 319-86-8 HCH-gamma (Lindane) 58-89-9 Heptachlor 76-44-8 Heptachlor Epoxide 1024-57-3 Analyte Registry Number Chemical Abstract Services 508.1-3 Hexachlorobenzene 118-74-1 Hexachlorocylcopentadiene 77-47-4 Methoxychlor 72-43-5 Metoachlor 51218-45-2 Metribuzin 21087-64-9 cis-Permethrin 61949-76-6 trans-Permethrin 61949-77-7 Propachlor 1918-16-7 Simazine 122-34-9 Toxaphene 8001-35-2 Trifluralin 1582-09-8 Aroclor 1016 12674-11-1 Aroclor 1221 11104-28-2 Aroclor 1232 11141-16-5 Aroclor 1242 53469-21-9 Aroclor 1248 12672-29-6 Aroclor 1254 11097-69-1 Aroclor 1260 11096-82-5 1.2 This method has been validated in a single laboratory and method detection limits have been determined for each analyte listed above. The method detection limit (MDL) is defined as the statistically calculated minimum amount that can be measured with 99% confidence that the reported value is greater than zero . For the listed analytes (except multi-component analytes),1 MDLs which range from 0.001-0.015 µg/L are listed in Table 3. MDLs for multi-component analytes (Aroclors and toxaphene) range from 0.01-0.13 µg/L. 2.0 SUMMARY OF METHOD 2.1 The analytes are extracted from the water sample by passing 1 L of sample through a preconditioned disk or cartridge containing a solid inorganic matrix coated with a chemically bonded C organic phase (liquid-solid extraction,18 LSE). The analytes are eluted from the LSE disk or cartridge with small volumes of ethyl acetate and methylene chloride, and this eluate is concentrated by evaporation of some of the solvent. The sample components are separated, identified, and measured by injecting micro-liter quantities of the eluate into a high resolution fused silica capillary column of a gas chromatograph/electron capture detector (GC/ECD) system. 508.1-4 3.0 DEFINITIONS 3.1 Internal Standard (IS) -- A pure analyte(s) added to a sample, extract, or standard 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. 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 or other processing, and is measured with the same procedures used to measure other sample components. The purpose of the SA is to monitor method performance with each sample. 3.3 Laboratory Reagent Blank (LRB) -- A aliquot of reagent water or other blank matrix 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. 3.4 Instrument Performance Check Solution (IPC) -- A solution of one or more method analytes, surrogates, internal standards, or other test substances used to evaluate the performance of the instrument system with respect to a defined set of method criteria. 3.5 Laboratory Fortified Blank (LFB) -- An aliquot of reagent water or other blank matrix 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 methodology is in control, and whether the laboratory is capable of making accurate and precise measurements. 3.6 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. 3.7 Stock Standard Solution -- A concentrated solution containing one or more method analytes prepared in the laboratory using assayed reference materials or purchased from a reputable commercial source. 3.8 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. 508.1-5 3.9 Quality Control Sample (QCS) -- A solution of method analytes of known concentrations which are used to fortify an aliquot of LRB or sample matrix. The QCS is obtained from a source external to the laboratory and different from the source of calibration standards. It is used to check laboratory performance with externally prepared test materials. 3.10 Method Detection Limit (MDL) -- The statistically calculated minimum amount of an analyte that can be measured with 99% confidence that the reported value is greater than zero .1 4.0 INTERFERENCES 4.1 Method interferences may be caused by contaminants in solvents, reagents, glassware, and other sample processing apparatus that lead to anomalous peaks or elevated baselines in gas chromatograms. 4.2 Interfering contamination may occur when a sample containing low concentrations of compounds is analyzed immediately after a sample containing relatively high concentrations of compounds. Syringes and splitless injection port liners must be cleaned carefully or replaced as needed. After analysis of a sample containing high concentrations of compounds, a laboratory reagent blank should be analyzed to ensure that accurate values are obtained for the next sample. 4.3 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. 5.0 SAFETY 5.1 The toxicity or carcinogenicity of each chemical and reagent used in this method has not been precisely defined. However, each one must be treated as a potential health hazard, and exposure to these chemicals should be minimized. Each laboratory is responsible for maintaining a current awareness of OSHA regulations regarding safe handling of the chemicals used in this method. Additional references to laboratory safety are cited .2-4 5.2 Some method analytes have been tentatively classified as known or suspected human or mammalian carcinogens. Pure standard materials and stock standard solutions of these compounds should be handled with suitable protection to skin, eyes, etc. 6.0 EQUIPMENT AND SUPPLIES (All specifications are suggested. Catalog numbers and brand names are included for illustration only.) 6.1 All glassware, including sample bottles, must be meticulously cleaned. This may be accomplished by washing with detergent and water, rinsing with tap water, distilled water, or solvent, air-drying, and heating (where appropriate) 508.1-6 in a muffle furnace for two hours at 400°C. Volumetric glassware must never be heated in a muffle furnace. 6.2 Sample Containers -- 1 L or 1 quart amber glass bottles fitted with Teflon-lined screw caps. Amber bottles are highly recommended since some of the method analytes are sensitive to light and are oxidized or decomposed upon exposure. 6.3 Volumetric Flasks -- Various sizes. 6.4 Micro Syringes -- Various sizes. 6.5 Vials -- Various sizes of amber vials with Teflon-lined screw caps. 6.6 Drying Column -- The drying tube should contain about 5-7 g of anhydrous sodium sulfate to prohibit residual water from contaminating the extract. Any small tube may be used, such as a syringe barrel, a glass dropper, etc., as long as no sodium sulfate passes through the column into the extract. 6.7 Fused Silica Capillary Gas Chromatography Column -- Any capillary column that provides adequate resolution, capacity, accuracy, and precision may be used. A 30 m X 0.25 mm ID fused silica capillary column coated with a 0.25 µm bonded film of polyphenylmethylsilicone (J&W DB-5) was used to develop this method. Any column which provides analyte separations equivalent to or better than this column may be used. 6.8 Gas Chromatograph -- Must be capable of temperature programming, be equipped for split/splitless injection, and be equipped with an electron capture detector. On-column capillary injection is acceptable if all the quality control specifications in Section 9.0 and Section 10.0 are met. The injection system should not allow the analytes to contact hot stainless steel or other hot metal surfaces that promote decomposition. 6.9 Vacuum Manifold -- A manifold system or a commercially available automatic or robotic sample preparation system designed for disks or cartridges should be utilized in this method. Ensure that all quality control requirements discussed in Section 9.0 are met. A standard all glass or Teflon lined filter apparatus should be used for disk or cartridge extraction when an automatic system is not utilized. 7.0 REAGENTS AND STANDARDS 7.1 Helium Carrier Gas -- As contaminant free as possible. 7.2 Extraction Disks and Cartridges -- Containing octadecyl bonded silica uniformly enmeshed in an inert matrix. The disks used to generate the data in this method were 47 mm in diameter and 0.5 mm in thickness. Larger disk sizes are acceptable. The disks should not contain any organic compounds, either from the matrix or the bonded silica, that will leach into the ethyl 508.1-7 acetate and methylene chloride eluant. Cartridges should be made of inert, non-leaching plastic or glass, and must not leach plasticizers or other organic compounds into the eluting solvent. Cartridges contain about 1 g of silica or other inert inorganic support whose surface is modified by chemically bonding octadecyl C groups. 18 7.3 Solvents -- Methylene chloride, ethyl acetate, and methanol, high purity pesticide quality or equivalent. 7.4 Reagent Water -- Water in which an interferant is not observed at the MDL of the compound of interest. Prepare reagent water by passing tap or distilled water through a filter bed containing activated carbon, or by using a water purification system. If necessary, store reagent water in clean bottles with Teflon-lined screw caps. 7.5 Hydrochloric Acid -- 6N. 7.6 Sodium Sulfate -- Anhydrous, muffled at 400°C for a minimum of four hours and stored in an air-tight clean glass container at ambient temperature. 7.7 Sodium Sulfite -- Anhydrous. 7.8 Pentachloronitrobenzene, ≥98% purity -- For use as the internal standard. 7.9 4,4-dibromobiphenyl, ≥96% purity -- For use as the surrogate compound. 7.10 Stock Standard Solutions -- Individual solutions of analytes may be purchased from commercial suppliers or prepared from pure materials. These solutions are usually available at a concentration of 500 µg/mL. These solutions are used to make the primary dilution standard. They should be stored in amber vials in a refrigerator or freezer. Stock standard solutions should be replaced if ongoing quality control checks indicate a problem. 7.11 Primary Dilution Standards (PDS) -- Prepare the solution(s) to contain all method analytes, but not the internal standard or surrogate compound, at a concentration of 2.5 µg/mL in ethyl acetate. 7.12 Instrument Performance Check Solution -- Prepare by accurately weighing 0.0010 g each of chlorothalonil, chlorpyrifos, DCPA, and HCH-delta. Dissolve each analyte in MTBE and dilute to volume in individual 10 mL volumetric flasks. Combine 2 µL of the chlorpyrifos stock solution, 50 µL of the DCPA stock solution, 50 µL of the chlorothalonil stock solution, and 40 µL of the HCH-delta stock solution to a 100 mL volumetric flask and dilute to volume with ethyl acetate. Transfer to a TFE-fluorocarbon-sealed screw cap bottle and store at room temperature. Solution should be replaced when ongoing QC (Section 9.0) indicates a problem. 508.1-8 7.13 Calibration Solutions -- Using the primary dilution standards, prepare calibration solutions at six concentrations in ethyl acetate. The calibration range is dependent upon the instrumentation used, and expected analyte concentrations in the samples to be analyzed. A suggested concentration range of calibration solutions is 0.002-1.0 µg/mL. Note: Calibration standards for toxaphene and each of the Aroclors must be prepared individually. 7.14 Internal Standard Solution -- Prepare this solution of pentachloronitrobenzene by itself in ethyl acetate at a concentration of 10 µg/mL. 7.15 Surrogate Compound Solution -- Prepare this solution of 4,4'-dibromobiphenyl by itself in ethyl acetate at a concentration of 10 µg/mL. Other surrogate compounds may be used if it can be demonstrated that they are not in any samples and are not interfered with by any analyte or other sample component. 7.16 GC Degradation Check Solution -- Prepare a solution in ethyl acetate containing endrin and 4,4'-DDT each at a concentration of 1 µg/mL. This solution will be injected to check for undesirable degradation of these compounds in the injection port by looking for endrin aldehyde and endrin ketone or for 4,4'-DDE and 4,4'-DDD. 8.0 SAMPLE COLLECTION, PRESERVATION, AND STORAGE 8.1 When sampling from a water tap, open the tap and allow the system to flush until the water temperature has stabilized (generally one to two minutes). Adjust the flow to about 500 mL/min. and collect the sample from the flowing stream. Keep sample sealed from collection time until analysis. When sampling from a body of water, fill the sample container with water from a representative area. Sampling equipment, including automatic samplers, must not use plastic tubing, plastic gaskets, or any parts that may leach interfering analytes into the sample. Automatic samplers that composite samples over time should use refrigerated glass sample containers. 8.2 Residual chlorine in the sample should be reduced by adding 50 mg/L of sodium sulfite (this may be added as a solid with stirring or shaking until dissolved, or as a prepared solution). 8.3 Adjust the sample to pH ≤2 by adding 6N HCl. It may require up to 4 mL to accomplish this. It is very important that the sample be dechlorinated (Section 8.2) before adding the acid to lower the pH of the sample. Adding sodium sulfite and HCl to the sample bottles prior to shipping the bottles to the sampling site is not permitted. HCl should be added at the sampling site to retard any microbiological degradation of method analytes. 508.1-9 8.4 Samples must be iced or refrigerated at 4°C from the time of collection until extraction. Preservation study results show that the analytes (except cyanazine) are stable for 14 days in samples that are preserved as described in Section 8.2 and Section 8.3. Refrigerated sample extracts may be stored up to 30 days. 8.5 If cyanazine is to be determined, a separate sample must be collected. Cyanazine degrades in the sample when it is stored under acidic conditions or when sodium sulfite is present in the stored sample. Samples collected for cyanazine determination MUST NOT be dechlorinated or acidified when collected. They should be iced or refrigerated as described above and analyzed within 14 days. However, these samples must be dechlorinated and acidified immediately prior to fortification with the surrogate standard and extraction using the same quantities of acid and sodium sulfite described above. 9.0 QUALITY CONTROL 9.1 Quality control requirements are the initial demonstration of laboratory capability followed by regular analyses of laboratory reagent blanks, laboratory fortified blanks, and laboratory fortified matrix samples. The laboratory must maintain records to document the quality of the data generated. Additional quality control practices are recommended. Determination of a MDL is also required. 9.2 Before any samples are analyzed or any time a new supply of disks or cartridges are received from a supplier, it must be demonstrated that a laboratory reagent blank is reasonably free of contamination that would prevent the determination of any analyte of concern. Both disks and cartridges could contain trace quantities of phthalate esters or silicon compounds that could prevent the determination of method analytes at low concentrations. Other sources of background contamination are impure solvents, impure reagents, and contaminated glassware. In general, background from method analytes should be below method detection limits. 9.3 Initial Demonstration of Capability 9.3.1 To demonstrate initial laboratory capability, analyze a minimum of four replicate laboratory fortified blanks containing each analyte of concern at a suggested concentration in the range of 0.01-0.5 µg/L. Prepare each reagent water replicate by adding sodium sulfite (Section 8.2) and HCl (Section 8.3) to each sample, then adding an appropriate aliquot of the primary dilution standard solution(s). Analyze each replicate according to the procedures described in Section 11.0. 9.3.2 Calculate the measured concentration of each analyte in each replicate, the mean concentration of each analyte in all replicates, the mean accuracy (as mean percentage of true value) for each analyte, and the 508.1-10 precision (as relative standard deviation, RSD) of the measurements for each analyte. 9.3.3 For each analyte, the mean accuracy, expressed as a percentage of the true value, should be 70-130% and the RSD should be ≤30%. 9.3.4 To determine the MDL, analyze a minimum of seven replicate laboratory fortified blanks which have been fortified with all analytes of interest at approximately 0.01 µg/L (Use a higher concentration for multi-component analytes). Calculate the MDL of each analyte using the procedure described in Section 13.2 . It is recommended that these1 analyses be carried out over a period of three or four days to produce more realistic limits. 9.3.5 Develop a system of control charts to plot the precision and accuracy of analyte and surrogate compound recoveries as a function of time. Charting of surrogate compound recoveries, which are present in every sample, will form a significant record of data quality. When surrogate recovery from a sample, a LFB, or a LFM is <70% or >130%, check calculations