METHOD 507 DETERMINATION OF NITROGEN- AND PHOSPHORUS-CONTAINING PESTICIDES IN WATER BY GAS CHROMATOGRAPHY WITH A NITROGEN-PHOSPHORUS DETECTOR Revision 2.0 T. Engels (Battelle Columbus Laboratories) — National Pesticide Survey Method 1, Revision 1.0 (1987) R. L. Graves — Method 507, Revision 2.0 (1989) ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268 507-1 ------- METHOD 507 DETERMINATION OF NITROGEN-AND PHOSPHORUS-CONTAINING PESTICIDES IN WATER BY GAS CHROMATOGRAPHY WITH A NITROGEN-PHOSPHORUS DETECTOR SCOPE AND APPLICATION 1.1 This is a gas chromatographic (GC) method applicable to the determination of certain nitrogen- and phosphorus-containing pesticides in ground water and finished drinking water.1 The following compounds can be determined using this method: Analyte Chemical Abstract Services Registry Number Alachlor 15972-60-8 Ametryn 834-12-8 Atraton 1610-17-9 Atrazine 1912-24-9 Bromacil 314-40-9 Butachlor 23184-66-9 Butylate 2008-41-5 Carboxin 5234-68-5 Chlorpropham 101-21-3 Cycloate 1134-23-2 Diazinon3* 333-41-5 Dichlorvos 62-73-7 Diphenamid 957-51-7 Disulfoton* 298-04-4 Disulfoton sulfone* 2497-06-5 Disulfoton sulfoxide3* 2497-07-6 EPTC 759-94-4 Ethoprop 13194-48-4 Fenamiphos 22224-92-6 Fenarimol 60168-88-9 Fluridone 59756-60-4 Hexazinone 51235-04-2 Merphos* 150-50-5 Methyl paraoxon 950-35-6 Metolachlor 51218-45-2 Metribuzin 21087-64-9 Mevinphos 7786-34-7 MGK 264 113-48-4 Molinate 2212-67-1 Napropamide 15299-99-7 Norflurazon 27314-13-2 507-2 ------- Analyte Chemical Abstract Services Registry Number Pebulate 1114-71-2 Prometon 1610-18-0 Prometryn 7287-19-6 Pronamide3* 23950-58-5 Propazine 139-40-2 Simazine 122-34-9 Simetryn 1014-70-6 Stirofos 22248-79-9 Tebuthiuron 34014-18-1 Terbacil 5902-51-2 Terbufos3* 13071-79-9 Terbutryn 886-50-0 Triademefon 43121-43-3 Tricyclazole 41814-78-2 Vernolate 1929-77-7 aCompound exhibits aqueous instability. Samples for which this compound is an analyte of interest must be extracted immediately (Sections 11.1 through 11.3). These compounds are only qualitatively identified in the National Pesticides Survey (NPS) Program. These compounds are not 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) have been determined for the analytes above (Section 13.0). Observed detection limits may vary among 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 10.3. 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 should be confirmed by at least one additional qualitative technique. 507-3 ------- 2.0 SUMMARY OF METHOD 2.1 A measured volume of sample of approximately 1 L is 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 volume of 5 mL during a solvent exchange to methyl tert-butyl ether (MTBE). Chromatographic conditions are described which permit the separation and measurement of the analytes in the extract by Capillary Column GC with a nitrogen- phosphorus detector (NPD). 3.0 DEFINITIONS 3.1 Internal Standard — 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 — 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. 507-4 ------- 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 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 — 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. 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 10.2. 4.1.1 Glassware must be scrupulously cleaned.2 Clean all glass- ware as soon as possible after use by thoroughly rinsing with the last solvent used in 507-5 ------- 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 ware. Thermally stable materials 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 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 may be 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 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. 4.3 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. Further processing of sample extracts may be necessary. Positive identifications should be confirmed (Section 11.5). 4.4 It is important that samples and working standards be contained in the same solvent. The solvent for 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. 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 507-6 ------- chemical analysis. Additional references to laboratory safety are available and have been identified3 5 for the information of the analyst. WARNING: When a solvent is purified, stabilizers added by the manufacturer may be removed thus potentially making the solvent hazardous. APPARATUS AND EQUIPMENT (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. 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 or equivalent) 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-570050-2525 or K-570050-1025 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). 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. 507-7 ------- 6.3 Separatory Funnel Shaker (Optional) — 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 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 |im film thickness (J&W Scientific) or equivalent. 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 |iL in splitless mode with a 45 second delay. The injector temperature was 250°C and the detector temperature was 300°C. Alternative columns may be used in accordance with the provisions described in Section 10.4. 6.8.2 Column 2 (Confirmation column) — 30 m long x 0.25 mm I.D.DB-1701 bonded fused silica column, 0.25 |im film thickness (J&W Scientific) or equivalent. 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 — Nitrogen-phosphorus (NPD). A NPD was used to generate the validation data presented in this method. Alternative detectors, including a mass spectrometer, may be used in accordance with the provisions described in Section 10.4. 507-8 ------- REAGENTS AND CONSUMABLE MATERIALS 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, Methyl Tert-Butyl Ether (MTBE) — Distilled-in-glass quality or equivalent. 7.2 Phosphate Buffer, pH 7 — Prepare by mixing 29.6 mL 0.1 N HC1 and 50 mL 0.1 M dipotassium phosphate. 7.3 Sodium Chloride (NaCl) — Crystal, ACS grade, heat treat in a shallow tray at 450°C for a minimum of four hours to remove interfering organic substances. 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. 7.5 Sodium thiosulfate — Granular, anhydrous, ACS grade. 7.6 Triphenylphosphate (TPP) — 98% purity, for use as internal standard (available from Aldrich Chemical Co.). 7.7 l,3-Dimethyl-2-nitrobenzene — 98% purity, for use as surrogate standard (available from Aldrich Chemical Co.). 7.8 Mercuric Chloride — ACS grade (Aldrich Chemical Co.), for use as a bactericide. If any other bactericide can be shown to work as well as mercuric chloride, it may be used instead. 7.9 Reagent Water — Reagent water is defined as a 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 |ig/|_iL) — 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. The stock solution for simazine should be prepared in methanol. 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 507-9 ------- standards may be used at any concentration if they are certified by the manufacturer or by an independent source. 7.10.2 Transfer the stock standard solutions into TFE-fluorocarbon-sealed screw cap amber vials. Store at room temperature 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 the internal standard solution by accurately weighing approximately 0.0500 g of pure TPP. Dissolve the TPP in MTBE and dilute to volume in a 100 mL volumetric flask. Transfer the internal standard solution to a TFE-fluorocarbon-sealed screw cap bottle and store at room temperature. Addition of 50 |iL of the internal standard solution to 5 mL of sample extract results in a final TPP concentration of 5.0 y\g/mL. Solution should be replaced when ongoing QC (Section 10.0) indicates a problem. Note that TPP has been shown to be an effective internal standard for the method analytes1, but other compounds may be used if the quality control requirements in Section 10.0 are met. 7.12 Surrogate Standard Solution — Prepare the surrogate standard solution by accurately weighing approximately 0.0250 g of pure l,3-dimethyl-2-nitrobenzene. Dissolve the l,3-dimethyl-2-nitrobenzene in MTBE and dilute to volume in a 100 mL volumetric flask. Transfer the surrogate standard solution to a TFE-fluorocarbon-sealed screw cap bottle and store at room temperature. Addition of 50 |iL of the surrogate standard solution to a 1 L sample prior to extraction results in a 1,3-dimethyl- 2-nitrobenzene concentration in the sample of 12.5 Hg/L. Solution should be replaced when ongoing QC (Section 10.0) indicates a problem. Note that l,3-dimethyl-2-nitrobenzene has been shown to be an effective surrogate standard for the method analytes1, but other compounds may be used if the quality control requirements in Section 10.0 are met. 7.13 Laboratory Performance Check Solution — Prepare the laboratory performance check solution by adding 5 |iL of the vernolate stock solution, 0.5 mL of the bromacil stock solution, 30 |iL of the prometon stock solution, 15 |iL of the atrazine stock solution, 1.0 mL of the surrogate solution, and 500 |iL of the internal standard solution to a 100 mL volumetric flask. Dilute to volume with MTBE and thoroughly mix the solution. Transfer to a TFE-fluorocarbon-sealed screw cap bottle and store at room temperature. Solution should be replaced when ongoing QC (Section 10.0) indicates a problem. SAMPLE COLLECTION. PRESERVATION. AND STORAGE 8.1 Grab samples must be collected in glass containers. Conventional sampling practices6 should be followed; however, the bottle must not be prerinsed with sample before collection. 507-10 ------- 8.2 Sample Preservation and Storage 8.2.1 Add mercuric chloride (See Section 7.8) to the sample bottle in amounts to produce a concentration of 10 mg/L. Add 1 mL of a solution containing 10 mg/mL of mercuric chloride in reagent water to the sample bottle at the sampling site or in the laboratory before shipping to the sampling site. A major disadvantage of mercuric chloride is that it is a highly toxic chemical; mercuric chloride must be handled with caution, and samples containing mercuric chloride must be disposed of properly. 8.2.2 If residual chlorine is present, add 80 mg of sodium thiosulfate per liter of sample to the sample bottle prior to collecting the sample. 8.2.3 After the sample is collected in a bottle containing preservative(s), seal the bottle and shake vigorously for one minute. 8.2.4 The samples must be iced or refrigerated at 4°C away from light from the time of collection until extraction. Preservation study results indicated that most method analytes present in samples were stable for 14 days when stored under these conditions.1 The analytes disulfoton sulfoxide, diazinon, pronamide, and terbufos exhibited significant aqueous instability, and samples to be analyzed for these compounds must be extracted immediately. The analytes carboxin, EPTC, fluridone, metolachlor, napropamide, tebuthiuron, and terbacil exhibited recoveries of less than 60% after 14 days. Analyte stability may be affected by the matrix; therefore, the analyst should verify that the preservation technique is applicable to the samples under study. 8.3 Extract Storage — Extracts should be stored at 4°C away from light. Preservation study results indicate that most analytes are stable for 28 days; however, a 14-day maximum extract storage time is recommended. The analyst should verify appropriate extract holding times applicable to the samples under study. CALIBRATION 9.1 Establish GC operating parameters equivalent to those indicated in Section 6.8. The GC system may be calibrated using either the internal standard technique (Section 9.2) or the external standard technique (Section 9.3). Be aware that NPDs may exhibit instability (i.e., fail to hold calibration curves over time). The analyst may, when analyzing samples for target analytes which are very rarely found, prefer to analyze on a daily basis a low level (e.g., 5-10 times detection limit or Vz times the regulatory limit, whichever is less), sample (containing all analytes of interest) and require some minimum sensitivity (e.g., Vz full scale deflection) to show that if the analyte were present it would be detected. The analyst may then quantitate using single point calibration (Section 9.2.5 or 9.3.4). 507-11 ------- NOTE: Calibration standard solutions must be prepared such that no unresolved analytes are mixed together. Internal Standard Calibration Procedure - To use this approach, the analyst must select one or more internal standards compatible 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. TPP has been identified as a suitable internal standard. 9.2.1 Prepare calibration standards at a minimum of three (recommend five) concentration levels for each analyte of interest by adding volumes of one or more stock standards to a volumetric flask. If Merphos is to be determined, calibrate with DEF (S,S,S-tributylphosphoro-trithioate). To each calibration standard, add a known constant amount of one or more of the internal standards, and dilute to volume with MTBE. The lowest standard should represent analyte concentrations near, but above, their respective EDLs. The remaining standards should bracket the analyte concentrations expected in the sample extracts, or should define the working range of the detector. 9.2.2 Analyze each calibration standard according to the procedure described in Section 11.4. Tabulate response (peak height or area) against concentration for each compound and internal standard. Calculate the response factor (RF) for each analyte and surrogate using Equation 1. Equation 1 RF - (A-> (C»> "" (AJOCJ where: As = Response for the analyte. Ais = Response for the internal standard. Cis = Concentration of the internal standard Hg/L. Cs = Concentration of the analyte to be measured Hg/L. 9.2.3 If the RF value over the working range is constant (20% RSD or less) the average RF can be used for calculations. Alternatively, the results can be used to plot a calibration curve of response ratios (As/Ais) vs. Cs. 9.2.4 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 analyte varies from the predicted response by more than ±20%, the test must be repeated using a fresh calibration standard. If the repetition also fails, a new calibration curve must be generated for that analyte using freshly prepared standards. 507-12 ------- 9.2.5 Single point calibration is a viable alternative to a calibration curve. Prepare single point standards from the secondary dilution standards in MTBE. The single point standard should be prepared at a concentration that produces a response that deviates from the sample extract response by no more than 20%. 9.2.6 Verify calibration standards periodically, recommend at least quarterly, by analyzing a standard prepared from reference material obtained from an independent source. Results from these analyses must be within the limits used to routinely check calibration. External Standard Calibration Procedure 9.3.1 Prepare calibration standards at a minimum of three (recommend five) concentration levels for each analyte of interest and surrogate compound by adding volumes of one or more stock standards to a volumetric flask. If Merphos is to be determined, calibrate with DEF (S,S,S- tributylphosphoro-trithioate). Dilute to volume with MTBE. The lowest standard should represent analyte concentrations near, but above, their respective EDLs. The remaining standards should bracket the analyte concentrations expected in the sample extracts, or should define the working range of the detector. 9.3.2 Starting with the standard of lowest concentration, analyze each calibration standard according to Section 11.4 and tabulate response (peak height or area) versus the concentration in the standard. The results can be used to prepare a calibration curve for each compound. Alternatively, if the ratio of response to concentration (calibration factor) is a constant over the working range (20% RSD or less), linearity through the origin can be assumed and the average ratio or calibration factor can be used in place of a calibration curve. 9.3.3 The working calibration curve or calibration factor must be verified on each working day by the measurement of a minimum of two calibration check standards, one at the beginning and one at the end of the analysis day. These check standards should be at two different concentration levels to verify the calibration curve. For extended periods of analysis (greater than eight hours), it is strongly recommended that check standards be interspersed with samples at regular intervals during the course of the analyses. If the response for any analyte varies from the predicted response by more than ±20%, the test must be repeated using a fresh calibration standard. If the results still do not agree, generate a new calibration curve. 9.3.4 Single-point calibration is a viable alternative to a calibration curve. Prepare single point standards from the secondary dilution standards in MTBE. The single point standard should be prepared at a concentration 507-13 ------- that produces a response that deviates from the sample extract response by no more than 20%. 9.3.5 Verify calibration standards periodically, recommend at least quarterly, by analyzing a standard prepared from reference material obtained from an independent source. Results from these analyses must be within the limits used to routinely check calibration. 10.0 QUALITY CONTROL 10.1 Minimum quality control (QC) requirements are initial demonstration of laboratory capability, determination of surrogate compound recoveries in each sample and blank, monitoring internal standard peak area or height in each sample and blank (when internal standard calibration procedures are being employed), analysis of laboratory reagent blanks, laboratory fortified samples, laboratory fortified blanks, and QC samples. 10.2 Laboratory Reagent Blanks — Before processing any samples, the analyst must demonstrate that all glassware and reagent interferences are under control. Each time a set of samples is extracted or reagents are changed, a LRB must be analyzed. If within the retention time window of any analyte of interest the LRB produces a peak that would prevent the determination of that analyte, determine the source of contamination and eliminate the interference before processing samples. 10.3 Initial Demonstration of Capability. 10.3.1 Select a representative fortified concentration (about 10 times EDL or at the regulatory Maximum Contaminant Level, whichever is lower) for each analyte. Prepare a sample concentrate (in methanol) containing each analyte at 1000 times selected concentration. With a syringe, add 1 mL of the concentrate to each of at least four 1 L aliquots of reagent water, and analyze each aliquot according to procedures beginning in Section 11.0. 10.3.2 For each analyte the recovery value for all four of these samples must fall in the range of R ±30% (or within R ±3SR if broader) using the values for R and SR for reagent water in Table 2. For those compounds that meet the acceptance criteria, performance is considered acceptable and sample analysis may begin. For those compounds that fail these criteria, this procedure must be repeated using four fresh samples until satisfactory performance has been demonstrated. 10.3.3 The initial demonstration of capability is used primarily to preclude a laboratory from analyzing unknown samples via a new, unfamiliar method prior to obtaining some experience with it. It is expected that as laboratory personnel gain experience with this method the quality of data will improve beyond those required here. 507-14 ------- 10.4 The analyst is permitted to modify GC columns, GC detectors, GC conditions, continuous extraction techniques, concentration techniques (i.e., evaporation techniques), internal standards or surrogate compounds. Each time such method modifications are made, the analyst must repeat the procedures in Section 10.3. 10.5 Assessing Surrogate Recovery 10.5.1 When surrogate recovery from a sample or method blank is <70% or >130%, check (1) calculations to locate possible errors, (2) fortifying solutions for degradation, (3) contamination, and (4) instrument performance. If those steps do not reveal the cause of the problem, reanalyze the extract. 10.5.2 If a blank extract reanalysis fails the 70-130% recovery criterion, the problem must be identified and corrected before continuing. 10.5.3 If sample extract reanalysis meets the surrogate recovery criterion, report only data for the reanalyzed extract. If sample extract reanalysis continues to fail the recovery criterion, report all data for that sample as suspect. 10.6 Assessing the Internal Standard 10.6.1 When using the internal standard calibration procedure, the analyst is expected to monitor the IS response (peak area or peak height) of all samples during each analysis day. The IS response for any sample chromatogram should not deviate from the daily calibration check standard's IS response by more than 30%. 10.6.2 If >30% deviation occurs with an individual extract, optimize instrument performance and inject a second aliquot of that extract. 10.6.2.1 If the reinjected aliquot produces an acceptable internal standard response report results for that aliquot. 10.6.2.2 If a deviation of greater than 30% is obtained for the reinjected extract, analysis of the sample should be repeated beginning with Section 11.0, provided the sample is still available. Otherwise, report results obtained from the reinjected extract, but annotate as suspect. 10.6.3 If consecutive samples fail the IS response acceptance criterion, immediately analyze a calibration check standard. 10.6.3.1 If the check standard provides a response factor (RF) within 20% of the predicted value, then follow procedures itemized in Section 10.6.2 for each sample failing the IS response criterion. 507-15 ------- 10.6.3.2 If the check standard provides a response factor which deviates more than 20% of the predicted value, then the analyst must recalibrate, as specified in Section 9.0. 10.7 Assessing Laboratory Performance — Laboratory Fortified Blank (LFB) 10.7.1 The laboratory must analyze at least one LFB sample with every twenty samples or one per sample set (all samples extracted within a 24-hour period) whichever is greater. The fortified concentration of each analyte in the LFB should be 10 times EDL or the MCL, whichever is less. Calculate accuracy as percent recovery (X;). If the recovery of any analyte falls outside the control limits (see Section 10.7.2), that analyte is judged out of control, and the source of the problem should be identified and resolved before continuing analyses. 10.7.2 Until sufficient data become available from within their own laboratory, usually a minimum of results from 20-30 analyses, the laboratory should assess laboratory performance against the control limits in Section 10.3.2 that are derived from the data in Table 2. When sufficient internal performance data becomes available, develop control limits from the mean percent recovery (X) and standard deviation (S) of the percent recovery. These data are used to establish upper and lower control limits as follows: UPPER CONTROL LIMIT = X + 3S LOWER CONTROL LIMIT = X - 3S After each 5-10 new recovery measurements, new control limits should be calculated using only the most recent 20-30 data points. These calculated control limits should never exceed those established in Section 10.3.2. 10.7.3 It is recommended that the laboratory periodically determine and document its detection limit capabilities for analytes of interest. 10.7.4 At least quarterly, analyze a QC sample from an outside source. 10.7.5 Laboratories are encouraged to participate in external performance evaluation studies such as the laboratory certification programs offered by many states or the studies conducted by USEPA. Performance evaluation studies serve as independent checks on the analyst's performance. 10.8 Assessing Analyte Recovery — Laboratory Fortified Sample Matrix 10.8.1 The laboratory must add a known concentration to a minimum of 5% of the routine samples or one sample concentration per set, whichever is greater. The fortified concentration should not be less then the background concentration of the sample selected for fortification. Ideally, the concentration should be the same as that used for the laboratory 507-16 ------- fortified blank (Section 10.7). Over time, samples from all routine sample sources should be fortified. 10.8.2 Calculate the percent recovery, P of the concentration for each analyte, after correcting the analytical result, X, from the fortified sample for the background concentration, b, measured in the unfortified sample, i.e.,: P = 100 (X - b) / fortifying concentration, and compare these values to control limits appropriate for reagent water data collected in the same fashion. If the analyzed unfortified sample is found to contain NO background concentrations, and the added concentrations are those specified in Section 10.7, then the appropriate control limits would be the acceptance limits in Section 10.7. If, on the other hand, the analyzed unfortified sample is found to contain background concentration, b, estimate the standard deviation at the background concentration, sb, using regressions or comparable background data and, similarly, estimate the mean, Xa and standard deviation, sa, of analytical results at the total concentration after fortifying. Then the appropriate percentage control limits would be P ±3sP , where: P = 100X / (b + fortifying concentration) and sP = 100 (sa2 + s,f)1/2 /fortifying concentration For example, if the background concentration for Analyte A was found to be 1 l-ig/L and the added amount was also 1 (Jg/L, and upon analysis the laboratory fortified sample measured 1.6 \i/L, then the calculated P for this sample would be (1.6 Hg/L minus 1.0 \ig/L)/ 1 Hg/L or 60%. This calculated P is compared to control limits derived from prior reagent water data. Assume it is known that analysis of an interference free sample_at 1 Hg/L yields an s of 0.12 Hg/L and similar analysis at 2.0 Hg/L yields X and s of 2.01 (Jg/L and 0.20 (Jg/L, respectively. The appropriate limits to judge the reasonableness of the percent recovery, 60%, obtained on the fortified matrix sample is computed as follows: [100 (2.01 ng/L) / 2.0 ng/L] ±3 (100) [(0.12 ng/L)2 + (0.20 (ig/L)2]12/1.0 ng/L = 100.5% ± 300 (0.233) = 100.5% ± 70% or 30% to 170 recovery of the added analyte. 10.9 Assessing Instrument System - Laboratory Performance Check (LPC) -Instrument performance should be monitored on a daily basis by analysis of the LPC sample. The LPC sample contains compounds designed to indicate appropriate instrument sensitivity, column performance (primary column) and chromatographic 507-17 ------- performance. LPC sample components and performance criteria are listed in Table 3. Inability to demonstrate acceptable instrument performance indicates the need for reevaluation of the instrument system. The sensitivity requirements are set based on the EDLs published in this method. If laboratory EDLs differ from those listed in this method, concentrations of the instrument QC standard compounds must be adjusted to be compatible with the laboratory EDLs. 10.10 The laboratory may adopt additional quality control practices for use with this method. The specific practices that are most productive depend upon the needs of the laboratory and the nature of the samples. For example, field or laboratory duplicates may be analyzed to assess the precision of the environmental measurements or field reagent blanks may be used to assess contamination of samples under site conditions, transportation and storage. 11.0 PROCEDURE 11.1 Extraction (Manual Method) 11.1.1 Mark the water meniscus on the side of the sample bottle for later determination of sample volume (Section 11.1.6). Add preservative to blanks and QC check standards. Fortify the sample with 50 |iL of the surrogate standard solution. Pour the entire sample into a 2 L separatory funnel. 11.1.2 Adjust the sample to pH 7 by adding 50 mL of phosphate buffer. 11.1.3 Add 100 g NaCl to the sample, seal, and shake to dissolve salt. 11.1.4 Add 60 mL methylene chloride to the sample bottle, seal, and shake 30 seconds to rinse the inner walls. Transfer the solvent to the separatory funnel and extract the sample by vigorously shaking the funnel for two minutes with periodic venting to release excess pressure. Allow the organic layer to separate from the water phase for a minimum of 10 minutes. If the emulsion interface between layers is more than one third the volume of the solvent layer, the analyst must employ mechanical techniques to complete the phase separation. The optimum technique depends upon the sample, but may include stirring, filtration of the emulsion through glass wool, centrifugation, or other physical methods. Collect the methylene chloride extract in a 500-mL Erlenmeyer flask. 11.1.5 Add a second 60 mL volume of methylene chloride to the sample bottle and repeat the extraction procedure a second time, combining the extracts in the Erlenmeyer flask. Perform a third extraction in the same manner. 11.1.6 Determine the original sample volume by refilling the sample bottle to the mark and transferring the water to a 1000 mL graduated cylinder. Record the sample volume to the nearest 5 mL. 507-18 ------- 11.2 Extraction (Automated Method) — Data presented in this method were generated using the automated extraction procedure with the mechanical tumbler. 11.2.1 Mark the water meniscus on the side of the sample bottle for later determination of sample volume (Section 11.2.6). Add preservative to blanks and QC check standards. Fortify the sample with 50 |iL of the surrogate standard solution. If the mechanical separatory funnel shaker is used, pour the entire sample into a 2 L separatory funnel. If the mechanical tumbler is used, pour the entire sample into a tumbler bottle. 11.2.2 Adjust the sample to pH 7 by adding 50 mL of phosphate buffer. 11.2.3 Add 100 g NaCl to the sample, seal, and shake to dissolve salt. 11.2.4 Add 300 mL methylene chloride to the sample bottle, seal, and shake 30 seconds to rinse the inner walls. Transfer the solvent to the sample contained in the separatory funnel or tumbler bottle, seal, and shake for 10 seconds, venting periodically. Repeat shaking and venting until pressure release is not observed. Reseal and place sample container in appropriate mechanical mixing device (separatory funnel shaker or tumbler). Shake or tumble the sample for one hour. Complete mixing of the organic and aqueous phases should be observed within about two minutes after starting the mixing device. 11.2.5 Remove the sample container from the mixing device. If the tumbler is used, pour contents of tumbler bottle into a 2 L separatory funnel. Allow the organic layer to separate from the water phase for a minimum of 10 minutes. If the emulsion interface between layers is more than one-third the volume of the solvent layer, the analyst must employ mechanical techniques to complete the phase separation. The optimum technique depends upon the sample, but may include stirring, filtration through glass wool, centrifugation, or other physical methods. Collect the methylene chloride extract in a 500 mL Erlenmeyer flask. 11.2.6 Determine the original sample volume by refilling the sample bottle to the mark and transferring the water to a 1000 mL graduated cylinder. Record the sample volume to the nearest 5 mL. 11.3 Extract Concentration 11.3.1 Assemble a K-D concentrator by attaching a 25 mL concentrator tube to a 500 mL evaporative flask. Other concentration devices or techniques may be used in place of the K-D if the requirements of Section 10.3 are met. 11.3.2 Dry the extract by pouring it through a solvent-rinsed drying column containing about 10 cm of anhydrous sodium sulfate. Collect the extract in the K-D concentrator, and rinse the column with 20-30 mL methylene 507-19 ------- chloride. Alternatively, add about 5 g anhydrous sodium sulfate to the extract in the Erlenmeyer flask; swirl flask to dry extract and allow to sit for 15 minutes. Decant the methylene chloride extract into the K-D concentrator. Rinse the remaining sodium sulfate with two 25 mL portions of methylene chloride and decant the rinses into the K-D concentrator. 11.3.3 Add one to two clean boiling stones to the evaporative flask and attach a macro Snyder column. Prewet the Snyder column by adding about 1 mL methylene chloride to the top. Place the K-D apparatus on a hot water bath, 65-70°C, so that the concentrator tube is partially immersed in the hot water, and the entire lower rounded surface of the flask is bathed with hot vapor. Adjust the vertical position of the apparatus and the water temperature as required to complete the concentration in 15-20 minutes. At the proper rate of distillation the balls of the column will actively chatter, but the chambers will not flood. When the apparent volume of liquid reaches 2 mL, remove the K-D apparatus and allow it to drain and cool for at least 10 minutes. 11.3.4 Remove the Snyder column and rinse the flask and its lower joint into the concentrator tube with 1-2 mL of MTBE. Add 5-10 mL of MTBE and a fresh boiling stone. Attach a micro-Snyder column to the concentrator tube and prewet the column by adding about 0.5 mL of MTBE to the top. Place the micro K-D apparatus on the water bath so that the concentrator tube is partially immersed in the hot water. Adjust the vertical position of the apparatus and the water temperature as required to complete concentration in 5-10 minutes. When the apparent volume of liquid reaches 2 mL, remove the micro K-D from the bath and allow it to drain and cool. Add 5-10 mL MTBE to the micro K-D and reconcentrate to 2 mL. Remove the micro K-D from the bath and allow it to drain and cool. Remove the micro Snyder column, and rinse the walls of the concentrator tube while adjusting the volume to 5.0 mL with MTBE. NOTE: If methylene chloride is not completely removed from the final extract, it may cause detector problems. 11.3.5 Transfer extract to an appropriate-sized TFE-fluorocarbon-sealed screw-cap vial and store, refrigerated at 4°C, until analysis by GC-NPD. 11.4 Gas Chromatography 11.4.1 Section 6.8 summarizes the recommended operating conditions for the gas chromatograph. Included in Table 1 are retention times observed using this method. Other GC columns, chromatographic conditions, or detectors may be used if the requirements of Section 10.3 are met. 11.4.2 Calibrate the system daily as described in Section 9.0. The standards and extracts must be in MTBE. 507-20 ------- 11.4.3 If the internal standard calibration procedure is used, add 50 |iL of the internal standard solution to the sample extract, seal, and shake to distribute the internal standard. 11.4.4 Inject 2 |iL of the sample extract. Record the resulting peak size in area units. 11.4.5 If the response for the peak exceeds the working range of the system, dilute the extract and reanalyze. 11.5 Identification of Analytes 11.5.1 Identify a sample component by comparison of its retention time to the retention time of a reference chromatogram. If the retention time of an unknown compound corresponds, within limits, to the retention time of a standard compound, then identification is considered positive. 11.5.2 The width of the retention time window used to make identifications should be based upon measurements of actual retention time variations of standards over the course of a day. Three times the standard deviation of a retention time can be used to calculate a suggested window size for a compound. However, the experience of the analyst should weigh heavily in the interpretation of chromatograms. 11.5.3 Identification requires expert judgement when sample components are not resolved chromatographically. When peaks obviously represent more than one sample component (i.e., broadened peak with shoulder(s) or valley between two or more maxima), or any time doubt exists over the identification of a peak on a chromatogram, appropriate alternative techniques to help confirm peak identification, need be employed. For example, more positive identification may be made by the use of an alternative detector which operates on a chemical/physical principle different from that originally used, e.g., mass spectrometry, or the use of a second chromatography column. A suggested alternative column is described in Section 6.8. 12.0 CALCULATIONS 12.1 Calculate analyte concentrations in the sample from the response for the analyte using the calibration procedure described in Section 9.0. 12.2 If the internal standard calibration procedure is used, calculate the concentration (C) in the sample using the response factor (RF) determined in Section 9.2 and Equation 2, or determine sample concentration from the calibration curve. Equation 2 507-21 ------- c Gug/L) (As) ds) (AJ (RF) (V ) where: As = Response for the parameter to be measured. Ais = Response for the internal standard. Is = Amount of internal standard added to each extract (|ig). VQ = Volume of water extracted (L). 12.3 If the external standard calibration procedure is used, calculate the amount of material injected from the peak response using the calibration curve or calibration factor determined in Section 9.3.2. The concentration (C) in the sample can be calculated from Equation 3. Equation 3 (A) (Vt) Concentration (ptg/L) = (V.) (Vs) where: A = Amount of material injected (ng). Vj = Volume of extract injected (uL). Vt = Volume of total extract (uL). Vs = Volume of water extracted (mL). 13.0 PRECISION AND ACCURACY 13.1 In a single laboratory, analyte recoveries from reagent water were determined at five concentration levels. Results were used to determine analyte EDLs and demonstrate method range.1 Analytes were divided into five groups for recovery studies. Analyte EDLs and analyte recoveries and standard deviation about the percent recoveries at one concentration are given in Table 2. 13.2 In a single laboratory, analyte recoveries from two standard synthetic ground waters were determined at one concentration level. Results were used to demonstrate applicability of the method to different ground water matrices.1 Analyte recoveries from the two synthetic matrices are given in Table 2. 14.0 REFERENCES 1. National Pesticide Survey Method No. 1: Determination of Nitrogen- and Phosphorus-Containing Pesticides in Groundwater by Gas Chromatography with a Nitrogen-Phosphorus Detector. 507-22 ------- 2. ASTM Annual Book of Standards, Part 11, Volume 11.02, D3694-82, "Standard Practice for Preparation of Sample Containers and for Preservation," American Society for Testing and Materials, Philadelphia, PA, 1986. 3. "Carcinogens - Working with Carcinogens," Department of Health, Education, and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, Publication No. 77-206, August 1977. 4. "OSHA Safety and Health Standards, General Industry," (29 CFR 1910), Occupational Safety and Health Administration, OSHA 2206, (Revised, January 1976). 5. "Safety in Academic Chemistry Laboratories," American Chemical Society Publication, Committee on Chemical Safety, 3rd Edition, 1979. 6. ASTM Annual Book of Standards, Part 11, Volume 11.01, D3370-82, "Standard Practice for Sampling Water," American Society for Testing and Materials, Philadelphia, PA, 1986. 507-23 ------- TABLE 1. RETENTION TIMES FOR METHOD ANALYTES Retention Time3 Analyte Col. 1 Col. 2 l,3-Dimethyl-2-nitrobenzene (surrogate) 14.48 b Dichlorvos 16.54 15.35 Disulfoton sulfoxide 19.08 b EPTC 20.07 16.57 Butylate 22.47 18.47 Mevinphos 22.51 21.92 Vernolate 22.94 19.25 Pebulate 23.41 19.73 Tebuthiuron 25.15 42.77 Molinate 25.66 22.47 Ethoprop 28.58 26.42 Cycloate 28.58 29.67 Chlorpropham 29.09 b Atraton 31.26 29.97 Simazine 31.49 31.32 Prometon 31.58 30 Atrazine 31.77 31.23 Propazine 32.01 31.13 Terbufos 32.57 b Pronamide 32.76 32.63 Diazinon 33.23 b Disulfoton 33.42 30.9 Terbacil 33.79 b Metribuzin 35.20 34.73 Methyl paraoxon 35.58 34.1 Simetryn 35.72 34.55 Alachlor 35.96 34.1 Ametryn 36.00 34.52 Prometryn 36.14 34.23 Terbutryn 36.80 34.8 Bromacil 37.22 40 Metolachlor 37.74 35.7 Triademefon 38.12 37 MGK 264c 38.73 36.73 Diphenamid 38.87 37.97 Stirofos 41.27 39.65 Disulfoton sulfone 41.31 42.42 Butachlor 41.45 39 Fenamiphos 41.78 41 Napropamide 41.83 b Tricyclazole 42.25 44.33 Merphosd 42.35 39.28 Carboxin 42.77 42.05 507-24 ------- TABLE 1. RETENTION TIMES FOR METHOD ANALYTES Retention Time3 Analyte Col. 1 Col. 2 Norflurazon Triphenyl phosphate (int. std.) Hexazinone Fenarimol Fluridone 45.92 47 46.58 51.32 56.68 47.58 45.4 47.8 50.02 59.07 'Columns and analytical conditions are described in Sections 6.8.1 and 6.8.2. bData not available. CMGK 264 gives two peaks; peak identified in this table used for quantification. dMerphos is converted to S,S,S-tributylphosphoro-trithioate (DEF) in the hot GC injection port; DEF is actually detected using these analyses conditions. 507-25 ------- TABLE 2. SINGLE LABORATORY ACCURACY, PRECISION AND ESTIMATED DETECTION LIMITS (EDLS) FOR ANALYTES FROM REAGENT WATER AND SYNTHETIC GROUNDWATERS3 Reagent Synthetic Synthetic Water Water 1 Water 2 EDL Cone. Analyte |Jg/L Rg/L Rc Srd R sR R sR Alachlor 0.38 3.8 95 11 82 6 90 8 Ametryn 2 20 91 10 102 11 96 4 Ametraton 0.6 6 91 11 84 7 91 8 Atrazine 0.13 1.3 92 8 89 6 92 5 Bromacil 2.5 25 91 9 81 5 88 8 Butachlor 0.38 3.8 96 4 93 15 84 5 Butylate 0.15 1.5 97 21 36 8 83 8 Carboxin 0.6 6 102 4 98 13 87 5 Chlorpropham 0.5 5 93 11 82 7 93 8 Cycloate 0.25 2.5 89 9 97 14 93 3 Diazinon 0.25 2.5 115 7 83 8 84 3 Dichlorvos 2.5 25 97 6 86 6 106 16 Diphenamid 0.6 6 93 8 88 4 93 5 Disulfoton 0.3 3 89 10 107 12 95 5 Disulfoton sulfone 3.8 7.5 98 10 92 5 96 3 Disulfoton sulfoxide 0.38 3.8 87 11 88 22 54 19 EPTC 0.25 2.5 85 9 83 5 86 4 Ethoprop 0.19 1.9 103 5 91 7 79 3 Fenamiphos 1. 10 90 8 87 5 89 2 Fenarimol 0.38 3.8 99 5 89 6 89 6 Fluridone 3.8 38 87 9 91 11 86 10 Hexazinone 0.76 7.6 90 7 86 6 95 9 Merphos 0.25 2.5 96 8 90 4 92 4 Methyl paraoxon 2.5 25 98 10 97 8 94 4 Metolachlor 0.75 7.5 93 4 92 10 84 4 Metribuzin 0.15 1.5 101 5 99 10 86 4 Mevinphos 5. 50 95 11 93 6 92 4 MGK 264 0.5 5 100 4 91 11 83 6 Molinate 0.15 1.5 98 18 83 8 89 9 Napropamide 0.25 2.5 101 6 89 5 104 18 Norflurazon 0.5 5. 94 5 101 15 87 4 Pebulate 0.13 1.3 94 9 80 6 98 15 Prometon 0.3 3 78 9 89 5 63 2 Prometryn 0.19 1.9 93 8 91 8 93 4 Pronamide 0.76 7.6 91 10 84 7 92 8 Propazine 0.13 1.3 92 8 89 6 92 5 Simazine 0.075 0.75 100 7 86 5 103 14 Simetryn 0.25 2.5 99 5 88 4 103 14 Stirofos 0.76 7.6 98 6 84 6 95 10 507-26 ------- TABLE 2. SINGLE LABORATORY ACCURACY, PRECISION AND ESTIMATED DETECTION LIMITS (EDLS) FOR ANALYTES FROM REAGENT WATER AND SYNTHETIC GROUNDWATERS3 Reagent Synthetic Synthetic Water Water 1 Water 2 Analyte EDL |Jg/L Cone. Rg/L Rc Srd R sR R sR Tebuthiuron 1.3 13 84 9 85 10 98 13 Terbacil 4.5 45 97 6 86 5 102 12 Terbufos 0.5 5 97 4 80 6 77 7 Terbutryn 0.25 2.5 94 9 91 8 92 4 Triademefon 0.65 6.5 93 8 94 5 95 5 Tricyclazole 1. 10 86 7 90 6 90 11 Vernolate 0.13 1.3 93 6 79 9 81 2 Data corrected for blank and represent the analysis of seven to eight samples using mechanical tumbling and internal standard calibration. bEDL = estimated detection limit; defined as either MDL (Appendix B to 40 CFR Part 136 - Definition and Procedure for the Determination of the Method Detection Limit - Revision 1.11) or a level of compound in a sample yielding a peak in the final extract with signal-to-noise ratio of approximately 5, whichever value is higher. The concentration used in determining the EDL is not the same as the concentration presented in this table. CR = average percent recovery. dS = standard deviation of the percent recovery. Corrected for amount found in blank; Absopure Nature Artesian Spring Water Obtained from the Absopure Water Company in Plymouth, Michigan. Corrected for amount found in blank; reagent water fortified with fulvic acid at the 1 mg/L concentration level. A well-characterized fulvic acid, available from the International Humic Substances Society (associated with the United States Geological Survey in Denver, Colorado), was used. 507-27 ------- TABLE 3. LABORATORY PERFORMANCE CHECK SOLUTION Test Analyte Cone, Hg/mL Requirements Sensitivity Vernolate 0.05 Detection of analyte; S/N >3 Chromatographic performance Bromacil 5.0 0.80 < PGF <1.20 Column performance Prometon 0.30 Resolution >0.7b Atrazine 0.15 aPGF - peak Gaussian factor. Calculated using the equation: pGp _ 1.83 x W (1/2) W (1/10) where: W(l/2) is the peak width at half height and W(l/10) is the peak width at tenth height. bResolution between the two peaks as defined by the equation: R = — W where: t is the difference in elution times between the two peaks and W is the average peak width, at the baseline, of the two peaks. ------- |