1、Designation: D 4282 02Standard Test Method forDetermination of Free Cyanide in Water and Wastewater byMicrodiffusion1This standard is issued under the fixed designation D 4282; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of freecyanides in waters and wastewaters. Free cyanide is heredefine
3、d as the cyanide which diffuses as cyanide (HCN), atroom temperature, from a solution at pH 6.21.2 This test method does not include complexes that resistdissociation, such as hexacyanoferrates and gold cyanide, nordoes it include thiocyanate and cyanohydrin.1.3 This test method may be applied to wa
4、ter and wastewa-ter samples containing free cyanide from 10 to 150 g/L.Greater concentrations may be determined by appropriatedilution.1.4 This test method has been fully validated by collabora-tive testing as specified by Practice D 2777.1.5 This standard does not purport to address all of thesafet
5、y concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardstatements, see 8.6, 8.9, Section 9, and 12.2.1.2. Refer
6、enced Documents2.1 ASTM Standards:D 1129 Terminology Relating to Water3D 1192 Guide for Equipment for Sampling Water andSteam in Closed Conduits3D 1193 Specification for Reagent Water3D 2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on Water3D 3370 P
7、ractices for Sampling Water from Closed Con-duits3D 3856 Guide for Good Laboratory Practices in Laborato-ries Engaged in Sampling and Analysis of Water3D 4210 Practice for Interlaboratory Quality Control Proce-dures and A Discussion on Reporting Low-Level Data3D 5788 Guide for Spiking Organics into
8、Aqueous Samples4D 5789 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Organic Constituents4D 5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water Analysis4E 275 Practice for Describing and Measuring Performanceof Ultraviolet, V
9、isible, and Near-Infrared Spectrophotom-eters53. Terminology3.1 Definitions:3.1.1 For a definition of terms used in this test method referto Terminology D 1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 free cyaniderefers to those simple cyanides orloosely held complexes of cyanide tha
10、t diffuse at pH 6, at roomtemperature.4. Summary of Test Method4.1 The reactions are carried out in a microdiffusion cell.4.2 The sample is treated with cadmium ion to precipitatethe hexacyanoferrates.4.3 The sample is buffered at pH 6 and allowed to stand for4h.4.4 The HCN diffuses into sodium hydr
11、oxide solution.4.5 An aliquot of the sodium hydroxide solution is treatedwith chloramine-T, and the cyanogen chloride formed isreacted with barbituric acid in pyridine. The absorbance of thecolor formed is measured using a spectrophotometer at awavelength of 580 nm.5. Significance and Use5.1 This te
12、st method is useful in distinguishing between thepotentially available free cyanide (total cyanide) and the freecyanide actually present.5.2 This test method provides a convenient technique formaking on-site free cyanide determinations.1This test method is under the jurisdiction of ASTM Committee D1
13、9 on Waterand is the direct responsibility of Subcommittee D19.06 on Methods forAnalysis forOrganic Substances in Water.Current edition approved July 10, 2002. Published August 2002. Originallypublished as D 4282 83. Last previous edition D 4282 95 (2001).2The paper by J. M. Kruse and L. E. Thibault
14、 “Determination of Free Cyanidein Ferro- and Ferricyanides,” Analytical Chemistry, 45(13): 22602261; 1973 Nov.,recommends a diffusion at pH 7. TheANSI modification (ANSI PH 4.41-1978) usespH 6. Using the conditions of the ANSI method, diffusion is completed within 4hours at pH 6. Longer diffusion ti
15、me was required at pH 7 on the samples analyzed.3Annual Book of ASTM Standards, Vol 11.01.4Annual Book of ASTM Standards, Vol 11.02.5Annual Book of ASTM Standards, Vol 03.06.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6. Interfer
16、ences6.1 Decomposition of Hexacyanoferrates During Diffusion:6.1.1 This decomposition is virtually eliminated by allow-ing the sample to diffuse in the dark, and by precipitating thehexacyanoferrates with cadmium ion.6.2 Instability of Free Cyanide in EffluentsThe reactivityof free cyanide with such
17、 chemicals as aldehydes or oxidizingagents, is not really a method interference. However, becauseof this instability, it is important for the diffusion to begin assoon after sampling as possible. It is beyond the scope of thistest method to list all the possible cyanide reactions that may beencounte
18、red.7. Apparatus7.1 Diffusion Cell, microdiffusion cell, Conway type,68-mm outside diameter.67.2 Micropipets, 0.10 mL, 1.00 mL.7.3 Spectrophotometer, conforming to Practice E 275.7.4 Spectrophotometer Cell, 1-cm equipped with a stopper.7.5 Pipet or Syringe, adjustable (to deliver 1.30 mL).7.6 Calome
19、l Reference Electrode, with saturated KNO3electrolyte, or the equivalent.7.7 pH Meter.7.8 Silver Electrode.8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatreagents shall conform to the specifications of the Committeeo
20、n Analytical Reagents of the American Chemical Society7where such specifications are available. Other grades may beused provided it is first ascertained that the reagent is ofsufficient purity to permit its use without lessening the accu-racy of the determination.8.2 Purity of WaterUnless otherwise
21、indicated, referenceto water shall be understood to mean reagent water conformingto Type II of Specification D 1193.8.3 Cadmium Chloride Solution (10 g/L), CdCl2Dissolve10.0 g of anhydrous cadmium chloride in 750 mL of water ina 1-L volumetric flask. Dilute to volume with water.8.4 Chloramine-T Reag
22、ent (10 g/L)Dissolve 1.00 g ofchloramine-T in 50 mL of water in a 100-mL volumetric flask.Dilute to volume with water. Make this reagent fresh daily.8.5 Cyanide Solution, Standard (1.00 mL = 2 g CN)Pipet 2.00 mLof cyanide stock solution (approximately 1.0 g/LCN) into a 1-L volumetric flask and dilut
23、e to volume withsodium hydroxide solution (2.05 g/L).8.6 Cyanide Solution StockDissolve 2.51 g of potassiumcyanide, KCN, in 500 mL of sodium hydroxide solution (2.05g/L) in a 1-L volumetric flask. Dilute to volume with sodiumhydroxide solution (2.05 g/L). This solution contains approxi-mately 1.0 g/
24、L cyanide (CN). (WarningKCN is highlytoxic, avoid contact or inhalation. Prepare and standardize thissolution weekly.)8.6.1 Standardizing Cyanide Stock Solution:8.6.1.1 Using a silver electrode and a reference electrode,titrate 20.0 mL of the cyanide stock solution (in a beaker alsocontaining 50 mL
25、of sodium hydroxide solution (2.05 g/L)with the silver nitrate standard solution.8.6.1.2 Record the mL of titration for use in the calculation(see Fig. 1 for an example of a typical titration curve).8.6.1.3 Calculate the concentration of the cyanide stocksolution using the following equation:50 3mL
26、silver nitrate!5mg/L CN2in stock solution1.00 mL of silver nitrate solution is equal to 1 mg of CN2.8.7 Potassium Phosphate Buffer Solution (Acidified)Add8.0 mLof concentrated phosphoric acid (sp gr 1.69), H3PO4,to100 mL of potassium phosphate solution.8.8 Potassium Phosphate Solution, 190 g/LAdd 40
27、0 mLof water to a 2-L beaker. Add and dissolve 14.5 g of sodiumhydroxide, NaOH. Add and dissolve 190 g of potassiumphosphate, monobasic, KH2PO4. Add water to 950 mL to aiddissolution. Adjust the pH of the solution to pH 5.9 to 6.1,using 100 g/Lsodium hydroxide solution. Transfer the solutionto a 1-L
28、 volumetric flask, and dilute to volume with water.8.9 Pyridine-Barbituric Acid ReagentAdd 15.0 g of bar-bituric acid to a 250-mLvolumetric flask. Wash down the sidesof the flask with just enough water to moisten the barbituricacid. Add 75 mL of pyridine and swirl to mix. Slowly add 15mL of concentr
29、ated hydrochloric acid (sp gr 1.19) and swirl tomix. Cool the solution to room temperature. Dilute to volumeand mix. It is recommended that this reagent be prepared freshweekly and stored in a dark place. (WarningPyridine istoxic; avoid contact or inhalation. Prepare this reagent in anexhaust hood.)
30、8.10 Silver Nitrate Solution, Standard (1 mL = 1 mg ofCN)Weigh 3.2647 g of silver nitrate on an analyticalbalance. Quantitatively transfer the silver nitrate to a 1-Lvolumetric flask. Dissolve and dilute to volume with water.Store in a dark glass bottle.6One source of supply for these cells is Arthu
31、r H. Thomas, No. 3806-F-10.7Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and t
32、he United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.NOTE 1Twenty millilitres of 2.51 g/L KCN titrated with AgNO3.FIG. 1 Typical Titration Curve Standardizing KCN SolutionD 4282 0228.11 Sodium Hydroxide Solution (4.1 g/L), NaOHAdd4.10 g of so
33、dium hydroxide to 800 mL of water in a 1-Lvolumetric flask. Stir until dissolved, and cool the solution toroom temperature before adjusting the final volume to 1 L.8.12 Sodium Hydroxide Solution (2.05 g/L), NaOHAdd2.05 g of sodium hydroxide to 800 mL of water in a 1-Lvolumetric flask. Stir until dis
34、solved, and cool the solution toroom temperature before adjusting the final volume to 1 L. (Analternative preparation is to dilute 0.10 N sodium hydroxidesolution with an equal volume of water.)9. Hazards9.1 Safety Precautions:9.1.1 Because of the toxicity of cyanide, exercise great carein its handl
35、ing. Acidification of cyanide solutions producestoxic gaseous hydrocyanide acid (HCN). Perform all manipu-lations in the hood so that any HCN that might volatilize issafely vented.9.1.2 Some of the reagents used in these methods, such ascyanide solutions, are highly toxic. Dispose of these reagentsa
36、nd their solutions properly.9.1.3 Do not pipet by mouth.9.2 Operational PrecautionsThis test method requirespractice and manual dexterity. The following practices havebeen found necessary to obtain reliable test results:9.2.1 Keep the samples in the dark because light candissociate complex cyanides
37、and lead to high values.9.2.2 Run the samples at least in duplicate.9.2.3 Use calibrated syringes or equivalent for deliveringthe sample. The force of the sample ejection aids in the mixingin the microdiffusion cell.9.2.4 Exercise great care during mixing of solutions bytilting and rotating the micr
38、odiffusion cell to avoid spilling orsplashing liquid from one compartment to another.9.2.5 Make the seal between the microdiffusion cell and lidairtight.9.2.6 It is important to observe the specified time periods inthose steps where such is noted. In particular, make thespectrophotometer measurement
39、s in the 3 to 6-min interval.9.2.7 Full color development in the spectrophotometer cellrequires that after each addition, mix the solution thoroughlywithout loss of material.10. Sampling and Sample Preservation10.1 Collect the sample in accordance with SpecificationD 1192 and Practices D 3370.10.2 A
40、 satisfactory preservation technique is not available.Reactions between CNand aldehydes, oxidizing agents, orsulfides will continue. However, if the sample cannot beanalyzed immediately, some steps can be taken to slow downthe reactions taking place.10.2.1 Adjust the sample to pH 12 or more. This mi
41、nimizesCNlosses due to vaporization.10.2.2 Store the samples in the dark to prevent hexacyano-ferrate breakdown.10.2.3 Keep the sample cool (for example, in a refrigerator).11. Calibration11.1 Calibration StandardsPipet 0.00 (Note 2), 5.00,10.0, and 15.0 mL of the 2.00-mg/L cyanide standard solution
42、into four 200-mL volumetric flasks. Dilute each of the flasks tovolume with sodium hydroxide solution (2.05 g/L). Thesedilutions yield calibration standards that are approximately 0,50, 100, and 150 g/L of CN, respectively.NOTE 1The 0.00 sample can also be considered the blank.11.2 To establish the
43、calibration curve, analyze the calibra-tion standards in accordance with the procedure in Section 12.Plot a calibration curve of concentrations of CNversusabsorbance (see Fig. 2). Standards should be run daily forcalibration, until it is established that the calibration curve willapply for a longer
44、period of time. Then it is only necessary torun two standards (such as 0 and 100 g/L CN) with eachbatch of samples as a check on the existing calibration curve.12. Procedure12.1 Microdiffusion of Free Cyanide:12.1.1 Pipet 3.00 mL of sample or calibration standard intothe outer ring of a clean, dry,
45、microdiffusion cell (see Fig. 3).12.1.2 Using a calibrated syringe (or adjustable pipet), pipet1.30 mL of sodium hydroxide solution (4 g/L) into the centerof the chamber of the microdiffusion cell.12.1.3 At this time, smear the ground glass side of a glasscell cover plate with a sufficiently heavy l
46、ayer of petroleumjelly or stopcock grease to achieve an airtight seal.12.1.4 Using a micropipet, pipet 0.5 mL of 10 g/L cadmiumchloride solution (10 g/L) into the sample in the outside ring ofthe microdiffusion cell.Tilt and rotate the cell for 15 s to ensuremixing.12.1.5 Immediately inject 1.0 mL o
47、f potassium phosphatesolution (190 g/L) into the sample in the outside ring of themicrodiffusion cell, inject at an angle in order to force thesolution around the chamber, and quickly seal with the greasedglass plate.12.1.6 Tilt and rotate the cell for 15 s to ensure propermixing.12.1.7 Keep the cov
48、ered cell in the dark for a period of notless than 4 h and not more than 8 h.FIG. 2 Example of Calibration Curve for CND 4282 02312.2 Dye Formation:12.2.1 At the end of the diffusion period, pipet a 1.00-mLaliquot of the NaOH solution from the center chamber of themicrodiffusion cell into a clean, d
49、ry, stoppered spectrophotom-eter cell. The stopper shall form a watertight seal. For a largenumber of determinations, it will be necessary to periodicallyclean the cells with acid-dichromate or methanol-hydrochloricacid (3 volumes of water, 1 volume of concentrated HCl sp gr1.19 and 4 volumes of methanol). Avoid contact with skin oreyes with these acid reagents. Methanol may be used to dry thecell, if necessary. (WarningDO NOT keep methanol near aflame.)12.2.2 Micropipet 0.1 mL of acidified potassium phosphatebuffer into the spectrophotometer
