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2、n American National StandardStandard Test Methods forNitrite-Nitrate in Water1This standard is issued under the fixed designation D 3867; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parent
3、heses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 These test methods cover the determination of nitrite nitrogen, nitrate nitrogen, and combined nitrite-nitrate nitrogen in water and wastewater in th
4、e range from 0.05 to 1.0 mg/L nitrogen. Two test methods2 are given as follows:SectionsTest Method AAutomated Cadmium Reduction9 to 16Test Method BManual Cadmium Reduction17 to 241.2 These test methods are applicable to surface, saline, waste, and ground waters. It is the users responsibility to ens
5、ure the validity of these test methods for waters of untested matrices.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety and health practices and determine
6、 the applica- bility of regulatory limitations prior to use. For specific hazard statements, see Note 1 and Note 2.2. Referenced Documents2.1 ASTM Standards:D 992 Test Method for Nitrate Ion in Water3D 1129 Terminology Relating to Water4D 1141 Specification for Substitute Ocean Water5D 1192 Specific
7、ation for Equipment for Sampling Water and Steam in Closed Conduits4D 1193 Specification for Reagent Water4D 1254 Test Method for Nitrite Ion in Water6D 2777 Practice for Determination of Precision and Bias ofApplicable Methods of Committee D-19 on Water4D 3370 Practices for Sampling Water from Clos
8、ed Con- duits41 These test methods are under the jurisdiction of ASTM Committee D-19 on Water and are the responsibility of Subcommittee D19.05 on Inorganic Constituents in Water.Current edition approved June 10, 1999. Published November 1999. Originally published as D 3867 79. Last previous edition
9、 D 3867 90.2 Methods similar to these appear in Methods of Chemical Analysis of Water andWastes, 2nd edition, U.S. Environmental Protection Agency.3 Discontinued; see 1983 Annual Book of ASTM Standards, Vol 11.01.4 Annual Book of ASTM Standards, Vol 11.01.5 Annual Book of ASTM Standards, Vol 11.02.6
10、 Discontinued; see 1980 Annual Book of ASTM Standards, Part 31.E 60 Practices for Photometric and Spectrometric Methodsfor Chemical Analysis of Metals7E 275 Practice for Describing and Measuring Performance of Ultraviolet, Visible, and Near Infrared Spectrophotom- eters83. Terminology3.1 Definitions
11、: For definitions of terms used in these test methods, refer to Terminology D 1129.4. Summary of Test Methods4.1 A filtered sample is passed through a column containing copper-coated cadmium granules to reduce nitrate ion to nitrite ion. The combined nitrite-nitrate nitrogen is determined by diazoti
12、zing the total nitrite ion with sulfanilamide and coupling with N-(1-naphthyl)ethylenediamine dihydrochloride to form a highly colored azo dye that is measured spectrophotometri- cally.4.2 The nitrite ion originally present in the sample can be determined separately by carrying out the procedure and
13、 omitting the cadmium reduction step.4.3 The nitrate ion can be calculated as the difference between the combined nitrite-nitrate nitrogen and the nitrite nitrogen.5. Significance and Use5.1 Both test methods use identical reagents and sample processing. The only difference between the two methods i
14、s that one test method is automated and the other is manual. The ranges and interferences are identical.5.2 The automated test method is preferred when large numbers of samples are to be analyzed. The manual test method is used for fewer samples or when automated instru- mentation is not available.5
15、.3 These test methods replace Test Methods D 1254 (Ni- trite) and D 992 (Nitrate). The nitrite test method (Test Method D 1254) used a reagent which is considered to be a potential carcinogen. The nitrate test method (Test Method D 992) has been shown to have relatively large errors when used in7 An
16、nual Book of ASTM Standards, Vol 03.05.8 Annual Book of ASTM Standards, Vol 03.06.*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1D 3867 99wastewaters and also has gre
17、ater manipulative difficulties thanthe test method described herein.6. Interferences6.1 Turbid samples must be filtered prior to analysis to eliminate particulate interference. Furthermore, sample turbid- ity results in a buildup on the reduction column that restricts sample flow.6.2 Sample color th
18、at absorbs at wavelengths between 520 and 540 nm interferes with the absorbance measurements. When color is suspect, analyze a sample blank, omitting the N-(1-naphthyl)ethylenediamine dihydrochloride from the color reagent.6.3 Oil and grease in the sample coat the surface of the cadmium and prevent
19、complete reduction of nitrate to nitrite. This interference is usually removed by filtration prior to analysis. If filtration is not adequate, the interference can be removed by preextracting the sample with an n-hexane or a solid phase extraction (SPE) filter.6.4 Certain metal ions, in concentratio
20、ns above 35 mg/L, may cause an interference. For example, Hg (II) and Cu (II) may form colored complex ions having absorption bands in the region of color measurement. Iron and manganese are other reported examples of interference.6.5 Excessive amounts of chlorine will deactivate the reduc- ing colu
21、mn. Chlorine might be present in some Type II water. The use of chlorine-containing Type II water will lead to a negative interference because nitrite and chlorine do not normally coexist. This is of particular importance when pre- paring standards or spiked samples.6.6 In acid samples (pH less than
22、 4.5) nitrate is not reduced in the cadmium column. To overcome this interference, the sample must be neutralized to a pH of between 6 and 8 prior to analysis.7. Purity of Reagents7.1 Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents sha
23、ll conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, when such specifications are available.9 Other grades may be used, pro- vided it is first ascertained that the reagent is of sufficient high purity to permit its use without lessening the accur
24、acy of the determination.7.2 Purity of WaterUnless otherwise indicated, references to water shall be understood to mean reagent water conforming to Specification D 1193, Type I. Other reagent water types may be used, provided it is first ascertained that the water is of sufficiently high purity to p
25、ermit its use without adversely affecting the bias and precision of these test methods. Type II water was specified at the time of round-robin testing of these test methods.9 “Reagent Chemicals, American Chemical Society Specifications,” American8. Sampling and Sample Preservation8.1 Collect the sam
26、ple in accordance with SpecificationD 1192 and Practices D 3370, as applicable.8.2 When nitrite ion is to be determined separately, analyze as soon as possible after sampling. Even when sterile bottles are used, bacteria naturally present in the water may cause conversion of all or part of nitrite i
27、on to other forms such as nitrate or ammonia. Ammonia and natural amines, which are frequently present in natural waters, may react with nitrites to form nitrogen. If samples are to be stored for 24 h or less, preserve the sample by refrigeration at 4C. If the sample must be stored for more than 24
28、h, preserve it by the addition of 2 mL of chloroform per litre (11.8 and 11.9) in addition to refrigeration at 4C.NOTE 1WARNING: Chloroform is toxic and is a suspected human carcinogen. Use with adequate ventilation or in a fume hood. Wear prescribed protective equipment. Use of chloroform is discou
29、raged, since its use renders the solution a hazardous waste.NOTE 2CAUTION: The common prescribed use of sulfuric acid or mercury compounds as preservatives is discouraged. Sulfuric acid does not necessarily inhibit oxidation and mercury compounds should be avoided to prevent environmental pollution.
30、 Mercuric chloride is known to deactivate the column.TEST METHOD AAUTOMATED CADMIUM REDUCTION9. Scope9.1 The applicable range of this test method is from 0.05 to1 mg/L of nitrite or nitrate nitrogen. The range may be extended upward by dilution of an appropriate aliquot. Many workers have found that
31、 this test method is reliable for nitrite and combined nitrite-nitrate levels to 0.01 mg N/L. However, the precision and bias data presented in this test method are insufficient to justify application of this test method in the 0.01 to 0.05 mg/L-N range.9.2 This test method is applicable to surface,
32、 saline, waste, and ground waters. It is the users responsibility to ensure the validity of this test method for waters of untested matrices.10. Apparatus10.1 Automated Analysis System 10 consisting of:10.1.1 Sampler.10.1.2 Manifold or Analytical Cartridge.10.1.3 Colorimeter equipped with a 15- or 5
33、0-mm tubular flow cell and 540 6 10-nm filters.10.1.4 Recorder or Electronic Data Acquisition Device.10.1.5 Digital Printer (Optional).10.1.6 Continuous Filter (Optional).10.2 Reduction ColumnsChoose the appropriate reduc- tion column for the manifold system. A schematic drawing of the manifold syst
34、em is shown in Fig. 1 and the cartridge system is shown in Fig. 2.10.2.1 Reduction Column, a glass tube 8 by 50 mm with the ends reduced in diameter to permit insertion into the system(see Fig. 1).Chemical Society, Washington, D.C. For suggestions on the testing of reagents not listed by the America
35、n Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K. and the United States Pharmacopeia andNational Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.10 The apparatus described is commercially available. ASTM does not undertaketo ensure a
36、nyone utilizing an automated analysis system against liability of infringement of patent or assume such liability.2D 3867 99FIG. 1 Nitrite-Nitrate ManifoldFIG. 2 Nitrite-Nitrate Cartridge10.2.2 Reduction Column, a U-shaped glass tubing,350-mm length and 2-mm inside diameter.NOTE 3A pump tube with 0.
37、081-in. (2.1-mm) inside diameter can beused in place of the 2-mm glass tube.3D 3867 9911. ReagentsTABLE 1 Concentration of Calibration Standards, AutomatedCadmium Reduction11.1 Ammonium Chloride Solution (85 g/L)Dissolve 85 g of ammonium chloride (NH Cl) in water and dilute to 1 L. Add NO3-N or NO2-
38、N, mg/LmL Standard Solution/100 mL0.5 mL wetting agent.1111.2 Cadmium, 40 to 60 mesh, granulated.1211.3 Color Reagent Add the following to 800 mL of water, while stirring constantly: 100 mL of concentrated phosphoric acid (H3PO4), 10 g of sulfanilamide, and 0.5 g ofN-1-(naphthyl)ethylenediamine dihy
39、drochloride. Stir until dis- solved. Add 1 mL of wetting agent,11 and dilute to 1 L with water. This solution is stable for about a month when stored ina brown bottle in a dark cool place.11.4 Copper Sulfate Solution (20 g/L)Dissolve 20 g of copper sulfate pentahydrate (CuSO45 H2O) in 500 mL of wate
40、r. Dilute to 1 L.11.5 n-Hexane.11.6 Hydrochloric Acid (1 + 1)Slowly add 50 mL of concentrated hydrochloric acid (HCl) to 40 to 45 mL of water and dilute to 100 mL.11.7 Nitrate Solution, Stock (1.0 mL = 1.0 mg NO3-N) Dry potassium nitrate (KNO3) in an oven at 105C for 24 h. Dissolve 7.218 g in water
41、in a 1-L volumetric flask. Dilute to the mark with water. This solution is stable for up to 1 month with refrigeration. If longer stability is required or refrigerationis not available, add 2 mL of chloroform as a preservative and store in a dark bottle. This solution is stable for 6 months. (See No
42、te 1.)11.8 Nitrate Solution, Standard (1.0 mL = 0.01 mg NO3- N)Dilute 10 mL of stock nitrate solution (11.7) to 1 L with water and store in a dark bottle. Prepare fresh as needed.11.9 Nitrite Solution, Stock (1.0 mL = 1.0 mg NO2-N) Place about 7 g of potassium nitrite (KNO2) in a tared 125-mL beaker
43、 and dry for about 24 h to a constant weight in a desiccator containing a suitable dessicant. Adjust the weight of the dry potassium nitrite to 6.072 g. Add 50 mL of water to the beaker, stir until dissolved, and transfer quantitatively to a1000-mL volumetric flask. Dilute to the mark with water sto
44、re in a sterilized bottle under refrigeration. Prepare fresh as needed.NOTE 4Potassium nitrite is easily oxidized, so use only fresh bottles of this reagent.11.10 Nitrite Solution, Standard (1.0 mL = 0.01 mg NO2- N)Dilute 10 mL of stock nitrite solution (11.9) to 1 L with water. This solution is uns
45、table; prepare fresh as needed.12. Preparation of Reduction Column12.1 Cadmium Granules TreatmentClean and copperize new or used cadmium granules in the following manner:12.1.1 Clean about 10 g of cadmium granules by washing with dilute HCl (11.6) and rinsing with water.12.1.2 Swirl the clean cadmiu
46、m in 100-mL portions of copper sulfate solution (11.4) in a beaker for 5 min or until the11 A 30 % aqueous solution of Brijt 35, a polyoxyethylene compound with dodecyl alcohol (sp gr 1.18 to 1.22) has been found satisfactory for this purpose.12 Different sizes of granulated cadmium may be used. The analyst should ensurethat adequate reduction occurs with the size chosen.0.010.10.020.20.040.40.11.00.22.00.44.00.77.0
