622有机磷农药

Method 622 The Determination of Organophosphorus Pesticides in Municipal and Industrial Wastewater Method 622 The Determination of Organophosphorus Pesticides in Municipal and Industrial Wastewater 1. SCOPE AND APPLICATION 1.1 This method covers the determination of certain organophosphorus pesticides. The following parameters can be determined by this method: Parameter STORET No. CAS No. Azinphos methyl 39580 86-50-0 Bolstar ) 35400-43-2 Chlorpyrifos ) 2921-88-2 Chlorpyrifos methyl ) 5598-13-0 Coumaphos 81293 56-72-4 Demeton 39560 8065-48-3 Diazinon 39570 333-41-5 Dichlorvos ) 62-73-7 Disulfoton 39010 298-04-4 Ethoprop ) 13194-48-4 Fensulfothion ) 115-90-2 Fenthion 39016 55-38-9 Merphos 39019 150-50-5 Mevinphos ) 7786-34-7 Naled ) 300-76-5 Parathion methyl 39600 298-00-0 Phorate 39023 298-02-2 Ronnel 39357 299-84-3 Stirofos ) 961-11-5 Tokuthion ) 34643-46-4 Trichloronate ) 327-98-0 1.2 This is a gas chromatographic (GC) method applicable to the determination of the compounds listed above in industrial and municipal discharges as provided under 40 CFR 136.1. Any modification of this method beyond those expressly permitted shall be considered a major modification subject to application and approval of alternate test procedures under 40 CFR 136.4 and 136.5. 1.3 The estimated method detection limit (MDL, defined in Section 15) for each parameter is listed in Table 1. The MDL for a specific wastewater may differ from those listed, depending upon the nature of interferences in the sample matrix. 1.4 The sample extraction and concentration steps in this method are essentially the same as several others in the 600-series methods. Thus, a single sample may be extracted to measure the parameters included in the scope of each of these methods. When cleanup is required, the concentration levels must be high enough to permit selecting aliquots, as necessary, in order to apply appropriate cleanup procedures. Under gas Method 622 chromatography, the analyst is allowed the latitude to select chromatographic conditions appropriate for the simultaneous measurement of combinations of these parameters (see Section 12). 1.5 This method is restricted to use by or under the supervision of analysts experienced in the use of gas chromatography 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 8.2. 1.6 When this method is used to analyze unfamiliar samples for any or all of the compounds above, compound identifications should be supported by at least one additional qualitative technique. Section 14 provides gas chromatograph/mass spectrometer (GC/MS) criteria appropriate for the qualitative confirmation of compound identifications. 2. SUMMARY OF METHOD 2.1 A measured volume of sample, approximately 1 L, is extracted with 15% methylene chloride using a separatory funnel. The methylene chloride extract is dried and exchanged to hexane during concentration to a volume of 10 mL or less. Gas chromatographic conditions are described which permit the separation and measurement of the compounds in the extract by gas chromatography with a thermionic bead or flame photometric detector in the phosphorus mode.1 3. INTERFERENCES 3.1 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 8.5. 3.1.1 Glassware must be scrupulously cleaned. Clean all glassware as soon as possible2 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 15 to 30 minutes. Do not heat volumetric ware. Thermally stable materials, such as PCBs, may not be eliminated by this treatment. Thorough rinsing with acetone and pesticide-quality hexane may be substituted for the heating. After drying and cooling, seal and store glassware 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. Method 622 3.2 Matrix interferences may be caused by contaminants that are coextracted from the sample. The extent of matrix interferences will vary considerably from source to source, depending upon the nature and diversity of the industrial complex or municipality sampled. Unique samples may require special cleanup approaches or selective GC detectors to achieve the MDL listed in Table 1. Use of a flame photometric detector in the phosphorus mode will minimize interferences from materials that do not contain phosphorus. Elemental sulfur, however, may interfere with the determination of certain organophosphorus pesticides by flame photometric gas chromatography. A halogen- specific detector (electrolytic conductivity or microcoulometric) is very selective for the halogen-containing pesticides and has been shown to be effective in the analysis of wastewater for dichlorvos, naled, and stirofos. 4. SAFETY 4.1 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. From this viewpoint, exposure to these chemicals must be reduced to the lowest possible level by whatever means available. 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 data handling 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 the3-5 information of the analyst. 5. APPARATUS AND MATERIALS 5.1 Sampling equipment, for discrete or composite sampling. 5.1.1 Grab-sample bottle: Amber borosilicate or flint glass, 1-L or 1-quart volume, fitted with screw-caps lined with TFE-fluorocarbon. Aluminum foil may be substituted for TFE if the sample is not corrosive. If amber bottles are not available, protect samples from light. The container and cap liner must be washed, rinsed with acetone or methylene chloride, and dried before use to minimize contamination. 5.1.2 Automatic sampler (optional): Must incorporate glass sample containers for the collection of a minimum of 250 mL. Sample containers must be kept refrigerated at 4°C and protected from light during compositing. If the sampler uses a peristaltic pump, a minimum length of compressible silicone rubber tubing may be used. Before use, however, the compressible tubing must be thoroughly rinsed with methanol, followed by repeated rinsings with reagent water to minimize the potential for contamination of the sample. An integrating flow meter is required to collect flow-proportional composites. 5.2 Glassware. (All specifications are suggested. Catalog numbers are included for illustration only.) 5.2.1 Separatory funnel: 2000-mL, with TFE-fluorocarbon stopcock, ground-glass or TFE stopper. Method 622 5.2.2 Drying column: Chromatographic column 400 mm long by 19 mm ID with coarse-fritted disc. 5.2.3 Concentrator tube, Kuderna-Danish: 10-mL, graduated (Kontes K-570050-1025 or equivalent). Calibration must be checked at the volumes employed in the test. Ground-glass stopper is used to prevent evaporation of extracts. 5.2.4 Evaporative flask, Kuderna-Danish: 500-mL (Kontes K-570001-0500 or equivalent). Attach to concentrator tube with springs. 5.2.5 Snyder column, Kuderna-Danish: Three-ball macro (Kontes K-503000-0121 or equivalent). 5.2.6 Vials: Amber glass, 10- to 15-mL capacity with TFE-fluorocarbon-lined screw-cap. 5.3 Boiling chips: Approximately 10/40 mesh. Heat at 400°C for 30 minutes or perform Soxhlet extraction with methylene chloride. 5.4 Water bath: Heated, with concentric ring cover, capable of temperature control (±2°C). The bath should be used in a hood. 5.5 Balance: Analytical, capable of accurately weighing to the nearest 0.0001 g. 5.6 Gas chromatograph: Analytical system complete with gas chromatograph suitable for on-column injection and all required accessories including syringes, analytical columns, gases, detector and strip-chart recorder. A data system is recommended for measuring peak areas. 5.6.1 Columns: These columns were used to develop the method performance statements in Section 15. Alternate columns may be used in accordance with the provisions described in Section 12.1. 5.6.1.1 Column 1: 180 cm long by 2 mm ID glass, packed with 5% SP-2401 on Supelcoport (100/120 mesh) or equivalent. 5.6.1.2 Column 2: 180 cm long by 2 mm ID glass, packed with 3% SP-2401 on Supelcoport (100/120 mesh) or equivalent. 5.6.1.3 Column 3: 50 cm long by c″ OD PTFE, packed with 15% SE-54 on Gas Chrom Q (80/100 mesh) or equivalent. 5.6.2 Detector: Thermionic bead or flame photometric in the phosphorus mode. These detectors have proven effective in the analysis of wastewaters for the parameters listed in the scope and were used to develop the method performance statements in Section 15. Alternative detectors, including a mass spectrometer, may be used in accordance with the provisions described in Section 12.1. Method 622 6. REAGENTS 6.1 Reagent water: Reagent water is defined as a water in which an interferent is not observed at the method detection limit of each parameter of interest. 6.2 Acetone, hexane, methylene chloride: Pesticide-quality or equivalent. 6.3 Sodium sulfate: ACS, granular, anhydrous. Condition by heating in a shallow tray at 400°C for a minimum of 4 hours to remove phthalates and other interfering organic substances. Alternatively, heat 16 hours at 450 to 500°C in a shallow tray or perform a Soxhlet extraction with methylene chloride for 48 hours. 6.4 Stock standard solutions (1.00 µg/µL): Stock standard solutions may be prepared from pure standard materials or purchased as certified solutions. 6.4.1 Prepare stock standard solutions by accurately weighing approximately 0.0100 g of pure material. Dissolve the material in pesticide-quality hexane or other suitable solvent 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. 6.4.2 Transfer the stock standard solutions into TFE-fluorocarbon-sealed screw-cap vials. Store at 4°C and protect from light. Frequently check stock standard solutions for signs of degradation or evaporation, especially just prior to preparing calibration standards from them. 6.4.3 Stock standard solutions must be replaced after 6 months, or sooner if comparison with check standards indicates a problem. 7. CALIBRATION 7.1 Establish gas chromatographic operating parameters equivalent to those indicated in Table 1. The gas chromatographic system may be calibrated using either the external standard technique (Section 7.2) or the internal standard technique (Section 7.3). 7.2 External standard calibration procedure. 7.2.1 For each parameter of interest, prepare calibration standards at a minimum of three concentration levels by adding accurately measured volumes of one or more stock standards to a volumetric flask and diluting to volume with hexane or other suitable solvent. One of the external standards should be representative of a concentration near, but above, the method detection limit. The other concentrations should correspond to the range of concentrations expected in the sample concentrates or should define the working range of the detector. Method 622 7.2.2 Using injections of l to 5 µL of each calibration standard, tabulate peak height or area responses against the mass injected. The results can be used to prepare a calibration curve for each parameter. Alternatively, the ratio of the response to the mass injected, defined as the calibration factor (CF), may be calculated for each parameter at each standard concentration. If the relative standard deviation of the calibration factor is less than 10% over the working range, the average calibration factor can be used in place of a calibration curve. 7.2.3 The working calibration curve or calibration factor must be verified on each working shift by the measurement of one or more calibration standards. If the response for any parameter varies from the predicted response by more than ±10%, the test must be repeated using a fresh calibration standard. Alternatively, a new calibration curve or calibration factor must be prepared for that parameter. 7.3 Internal standard calibration procedure: To use this approach, the analyst must select one or more internal standards similar in analytical behavior to the compounds of interest. The analyst must further demonstrate that the measurement of the internal standard is not affected by method or matrix interferences. Due to these limitations, no internal standard applicable to all samples can be suggested. 7.3.1 Prepare calibration standards at a minimum of three concentration levels for each parameter of interest by adding volumes of one or more stock standards to a volumetric flask. To each calibration standard, add a known constant amount of one or more internal standards, and dilute to volume with hexane or other suitable solvent. One of the standards should be representative of a concentration near, but above, the method detection limit. The other concentrations should correspond to the range of concentrations expected in the sample concentrates, or should define the working range of the detector. 7.3.2 Using injections of 1 to 5 µL of each calibration standard, tabulate the peak height or area responses against the concentration for each compound and internal standard. Calculate response factors (RF) for each compound as follows: Equation 1 where A = Response for the parameter to be measureds A = Response for the internal standardis C = Concentration of the internal standard, in µg/Lis C = Concentration of the parameter to be measured, in µg/Ls Method 622 If the RF value over the working range is constant, less than 10% relative standard deviation, the RF can be assumed to be invariant and the average RF may be used for calculations. Alternatively, the results may be used to plot a calibration curve of response ratios, A /A against RF.s is 7.3.3 The working calibration curve or RF must be verified on each working shift by the measurement of one or more calibration standards. If the response for any parameter varies from the predicted response by more than ±10%, the test must be repeated using a fresh calibration standard. Alternatively, a new calibration curve must be prepared for that compound. 7.4 Before using any cleanup procedure, the analyst must process a series of calibration standards through the procedure to validate elution patterns and the absence of interference from the reagents. 8. QUALITY CONTROL 8.1 Each laboratory using this method is required to operate a formal quality control program. The minimum requirements of this program consist of an initial demonstration of laboratory capability and the analysis of spiked samples as a continuing check on performance. The laboratory is required to maintain performance records to define the quality of data that is generated. 8.1.1 Before performing any analyses, the analyst must demonstrate the ability to generate acceptable accuracy and precision with this method. This ability is established as described in Section 8.2. 8.1.2 In recognition of the rapid advances occurring in chromatography, the analyst is permitted certain options to improve the separations or lower the cost of measurements. Each time such modifications to the method are made, the analyst is required to repeat the procedure in Section 8.2. 8.1.3 The laboratory must spike and analyze a minimum of 10% of all samples to monitor continuing laboratory performance. This procedure is described in Section 8.4. 8.2 To establish the ability to generate acceptable accuracy and precision, the analyst must perform the following operations. 8.2.1 Select a representative spike concentration for each compound to be measured. Using stock standards, prepare a quality control check sample concentrate in acetone, 1000 times more concentrated than the selected concentrations. 8.2.2 Using a pipette, add 1.00 mL of the check sample concentrate to each of a minimum of four 1000-mL aliquots of reagent water. A representative wastewater may be used in place of the reagent water, but one or more additional aliquots must be analyzed to determine background levels, and the spike level must exceed twice the background level for the test to be valid. Analyze the aliquots according to the method beginning in Section 10. Method 622 8.2.3 Calculate the average percent recovery (R), and the standard deviation of the percent recovery (s), for the results. Wastewater background corrections must be made before R and s calculations are performed. 8.2.4 Using the appropriate data from Table 2, determine the recovery and single- operator precision expected for the method, and compare these results to the values calculated in Section 8.2.3. If the data are not comparable, review potential problem areas and repeat the test. 8.3 The analyst must calculate method performance criteria and define the performance of the laboratory for each spike concentration and parameter being measured. 8.3.1 Calculate upper and lower control limits for method performance as follows: Upper Control Limit (UCL) = R + 3s Lower Control Limit (LCL) = R − 3s where R and s are calculated as in Section 8.2.3. The UCL and LCL can be used to construct control charts that are useful in observing trends in performance.6 8.3.2 The laboratory must develop and maintain separate accuracy statements of laboratory performance for wastewater samples. An accuracy statement for the method is defined as R ± s. The accuracy statement should be developed by the analysis of four aliquots of wastewater as described in Section 8.2.2, followed by the calculation of R and s. Alternatively, the analyst may use four wastewater data points gathered through the requirement for continuing quality control in Section 8.4. The accuracy statements should be updated regularly.6 8.4 The laboratory is required to collect in duplicate a portion of their samples to monitor spike recoveries. The frequency of spiked sample analysis must be at least 10% of all samples or one spiked sample per month, whichever is greater. One aliquot of the sample must be spiked and analyzed as described in Section 8.2. If the recovery for a particular parameter does not fall within the control limits for method performance, the results reported for that parameter in all samples processed as part of the same set must be qualified as described in Section 13.3. The laboratory should monitor the frequency of data so qualified to ensure that it remains at or below 5%. 8.5 Before processing any samples, the analyst must demonstrate through the analysis of a 1-L aliquot of reagent water that all glassware and reagent interferences are under control. Each time a set of sam