1、Designation: D4282 15Standard Test Method forDetermination of Free Cyanide in Water and Wastewater byMicrodiffusion1This standard is issued under the fixed designation D4282; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () 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 heredefined a
3、s 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 water
4、 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 D2777.1.5 The values stated in SI units are to be regarded asstandard.
5、No other units of measurement are included in thisstandard.1.6 This standard does not purport to address all of thesafety 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-bi
6、lity of regulatory limitations prior to use. For specific hazardstatements, see 8.6, 8.9, Section 9, and 12.2.1.2. Referenced Documents2.1 ASTM Standards:3D1129 Terminology Relating to WaterD1192 Guide for Equipment for Sampling Water and Steamin Closed Conduits (Withdrawn 2003)4D1193 Specification
7、for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD3856 Guide for Management Systems in LaboratoriesEngaged in Analysis of WaterD4210 Practice for Intralaboratory Quality C
8、ontrol Proce-dures and a Discussion on Reporting Low-Level Data(Withdrawn 2002)4D5788 Guide for Spiking Organics into Aqueous SamplesD5789 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Organic Constituents(Withdrawn 2002)4D5847 Practice for Writing Quality Control
9、Specificationsfor Standard Test Methods for Water AnalysisE275 Practice for Describing and Measuring Performance ofUltraviolet and Visible Spectrophotometers3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this standard, refer toTerminology D1129.3.2 Definitions of Terms Specific
10、 to This Standard:3.2.1 free cyanidethose simple cyanides or loosely heldcyanide complexes that diffuse at pH 6, at room temperature.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
11、The sample is buffered at pH 6 and allowed to stand for4h.4.4 The HCN diffuses into sodium hydroxide solution.4.5 An aliquot of the sodium hydroxide solution is treatedwith chloramine-T, and the cyanogen chloride formed is1This test method is under the jurisdiction of ASTM Committee D19 on Waterand
12、is the direct responsibility of Subcommittee D19.06 on Methods forAnalysis forOrganic Substances in Water.Current edition approved July 15, 2015. Published July 2015. Originallyapproved in 1983. Last previous edition approved in 2015 as D4282 02 (2015).DOI: 10.1520/D4282-R15.2The paper by J. M. Krus
13、e and L. E. Thibault “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.
14、 Longer diffusion time was required at pH 7 on the samples analyzed.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM w
15、ebsite.4The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1reacted with barbituric acid in pyridine. The absorbance of thecolor formed is measured using a
16、 spectrophotometer at awavelength of 580 nm.5. Significance and Use5.1 This test 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 d
17、eterminations.6. Interferences6.1 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 reactivity
18、of free cyanide with such 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 reac
19、tions that may beencountered.7. Apparatus7.1 Diffusion Cell, microdiffusion cell, Conway type, 68mm outside diameter.57.2 Micropipets, 0.10 mL, 1.00 mL.7.3 Spectrophotometer, conforming to Practice E275.7.4 Spectrophotometer Cell, 1 cm equipped with a stopper.7.5 Pipet or Syringe, adjustable (to del
20、iver 1.30 mL).7.6 Calomel 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 specific
21、ations of the Committeeon Analytical Reagents of the American Chemical Society6where 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 o
22、f WaterUnless otherwise indicated, referenceto water shall be understood to mean reagent water conformingto Type II of Specification D1193.8.3 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 wate
23、r.8.4 Chloramine-T Reagent (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 mL of cyanide stock solution (approximately 1.0g/LCN)intoa1Lvolumetr
24、ic flask and dilute 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) ina1Lvolumetric flask. Dilute to volume with sodiumhydroxide solution (2.05 g/L). This solution contains approxi
25、-mately 1.0 g/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 alsocon
26、taining 50 mL 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 eq
27、uation:50 3 mL silver nitrate! 5 mg/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 Soluti
28、on, 190 g/LAdd 400 mLof water toa2Lbeaker. 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 sol
29、utiontoa1Lvolumetric flask, and dilute to volume with water.5One source of supply for these cells is Arthur H. Thomas, No. 3806-F-10.6Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the Ame
30、rican Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.NOTE 1Twenty millilitres of 2.51 g/L KCN titrated with AgNO3.FIG. 1 Typical Titratio
31、n Curve Standardizing KCN SolutionD4282 1528.9 Pyridine-Barbituric Acid ReagentAdd 15.0 g of bar-bituric acid to a 250 mL volumetric 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 concentrated hy
32、drochloric 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.)8.10 Si
33、lver Nitrate Solution, Standard (1 mL = 1 mg ofCN)Weigh 3.2647 g of silver nitrate on an analyticalbalance. Quantitatively transfer the silver nitrate toa1Lvolumetric flask. Dissolve and dilute to volume with water.Store in a dark glass bottle.8.11 Sodium Hydroxide Solution (4.1 g/L), NaOHAdd4.10 g
34、of sodium hydroxide to 800 mL of water ina1Lvolumetric 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 ina1Lvolumetric flask. Stir until diss
35、olved, 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 handli
36、ng. 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 reagentsan
37、d 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 a
38、nd 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 micro
39、diffusion 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 measurements
40、 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 Guide D1192and Practices D3370.10.2 A satisfacto
41、ry 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 minimizesCNlo
42、sses 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 solutioninto four 2
43、00 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 calibration
44、 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 period of t
45、ime. 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, microdiffus
46、ion 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.FIG. 2 Example of Calibration Curve for CND4282 15312.1.3 At this time, smear the ground glass side of a glasscell
47、 cover plate with a sufficiently heavy layer 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 ensurem
48、ixing.12.1.5 Immediately inject 1.0 mL of 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
49、 ensure propermixing.12.1.7 Keep the covered cell in the dark for a period of notless than 4 h and not more than 8 h.Typical Cell(a)Filling Inner Compartment(b)Filling Outer Compartment(c)FIG. 3 Microdiffusion CellD4282 15412.2 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, dry, stoppered spectrophotom-eter cell. The stopper shall form a watertight seal. For a largenumber of determinations, it will be necessary to periodically
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