1、Designation: D7284 13 (Reapproved 2017)Standard Test Method forTotal Cyanide in Water by Micro Distillation followed byFlow Injection Analysis with Gas Diffusion Separation andAmperometric Detection1This standard is issued under the fixed designation D7284; the number immediately following the desig
2、nation indicates the year oforiginal adoption or, in the case of revision, the year 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 is used to det
3、ermine the concentrationof total cyanide in an aqueous wastewater or effluent. This testmethod detects the cyanides that are free (HCN and CN) andstrong-metal-cyanide complexes that dissociate and releasefree cyanide when refluxed under strongly acidic conditions.1.2 This test method may not be appl
4、icable to processsolutions from precious metals mining operations.1.3 This procedure is applicable over a range of approxi-mately 2 to 500 g/L (parts per billion) total cyanide. Higherconcentrations can be measured with sample dilution or lowerinjection volume.1.4 The determinative step of this test
5、 method utilizes flowinjection with amperometric detection based on Test MethodD6888. Prior to analysis, samples must be distilled with amicro-distillation apparatus described in this test method orwith a suitable cyanide distillation apparatus specified in TestMethods D2036.1.5 The values stated in
6、 SI units are to be regarded asstandard. 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 heal
7、th practices and determine the applica-bility of regulatory limitations prior to use. Specific hazardstatements are given in 8.6 and Section 9.1.7 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Pr
8、inciples for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2036 Test Methods
9、for Cyanides in WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3856 Guide for Management Systems in LaboratoriesEngaged in Analysis of WaterD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water An
10、alysisD6696 Guide for Understanding Cyanide SpeciesD6888 Test Method for Available Cyanides with LigandDisplacement and Flow InjectionAnalysis (FIA) UtilizingGas Diffusion Separation and Amperometric DetectionD7365 Practice for Sampling, Preservation and MitigatingInterferences in Water Samples for
11、Analysis of CyanideE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this standard, refer toTerminology D1129 and Guide D6696.3.2 Definitions of Terms Specific to This Standard:3.2.1 to
12、tal cyanide, ntotal cyanide is an analytically de-fined term that refers to the sum total of all of the inorganicchemical forms of cyanide that dissociate and release freecyanide when refluxed under strongly acidic conditions.3.2.1.1 DiscussionTotal cyanide is determined analyti-cally through strong
13、 acid distillation or UV radiation followedby analysis of liberated free cyanide on aqueous samplespreserved with NaOH (pH12). In water, total cyanide includesthe following dissolved species: free cyanide, weak aciddissociable metal cyanide complexes and strong metal cyanidecomplexes. Also, some of
14、the strong metal cyanide complexes,1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.06 on Methods forAnalysis forOrganic Substances in Water.Current edition approved July 15, 2017. Published July 2017. Originallyapproved i
15、n 2008. Last previous edition approved in 2013 as D7284 13. DOI:10.1520/D7284-13R17.2For 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 p
16、age onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for
17、theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1such as those of gold, cobalt and platinum, might not be fullyrecovered during the total cyanide analytical procedure.Additionally, total cyanide
18、may also include some organicforms of cyanide such as nitriles that release free cyanide underthe conditions of the analysis.4. Summary of Test Method4.1 The samples are distilled with a strong acid in thepresence of magnesium chloride catalyst and captured insodium hydroxide absorber solution.4.2 T
19、he absorber solution is introduced into a flow injectionanalysis (FIA) system where it is acidified to form hydrogencyanide (HCN). The hydrogen cyanide gas diffuses through ahydrophobic gas diffusion membrane, from the acidic donorstream into an alkaline acceptor stream.4.3 The captured cyanide is s
20、ent to an amperometric flow-cell detector with a silver-working electrode. In the presence ofcyanide, silver in the working electrode is oxidized at theapplied potential. The anodic current measured is proportionalto the concentration of cyanide.4.4 Calibrations and data are processed with the instr
21、u-ments data acquisition software.5. Significance and Use5.1 Cyanide and hydrogen cyanide are highly toxic. Regu-lations have been established to require the monitoring ofcyanide in industrial and domestic wastes and surface waters.35.2 This test method is applicable for natural waters, indus-trial
22、wastewaters and effluents.6. Interferences6.1 Improper sample collection or pretreatment can result insignificant positive or negative bias, therefore it is imperativethat samples be collected and mitigated for interferences asdescribed in Practice D7365.6.1.1 Sulfide captured in the absorber soluti
23、on above 50-mg/L S2will diffuse through the gas diffusion membraneduring flow injection analysis and can be detected in theamperometric flowcell as a positive response. Refer to Section11.2 for sulfide abatement.6.1.2 Thiocyanate in the presence of oxidants (for example,nitrates, hydrogen peroxide,
24、chlorine or chloramine, Carosacid), can decompose to form cyanide during the distillationresulting in positive interference regardless of the determina-tive step (amperometry, colorimetry, etc.). During acidicdistillation, decomposition of thiocyanate in the absence ofoxidants produces elemental sul
25、fur, sulfur(IV) oxide, as well ascarbonyl sulfide which eventually leads to the formation ofsulfite ion (SO32) in the NaOH absorbing solution. The sulfiteion slowly oxidizes cyanide to cyanate resulting in a negativeinterference. Therefore, samples that are known to containsignificant amounts of thi
26、ocyanate may need to be analyzedwith a test method that does not require distillation, forexample, available cyanide by Test Method D6888.6.1.2.1 During the validation study, synthetic samples con-taining up to 15 mg/L SCNand 25 mg/L NO3as N yieldedless than 0.5 % of the SCNto be measurable CN. Fore
27、xample, a solution that did not contain any known amount ofcyanide, but did contain 15-mg/L SCNand 25 mg/L NO3asN, was measured as 53.1 g/L CN.7. Apparatus and Instrumentation7.1 The instrument should be equipped with a precisesample introduction system, a gas diffusion manifold with340 CFR Part 136
28、.FIG. 1 Flow Injection Analysis ApparatusD7284 13 (2017)2hydrophobic membrane, and an amperometric detection sys-tem to include a silver working electrode, a Ag/AgCl referenceelectrode, and a Pt or stainless steel counter electrode. Theapparatus schematic is shown in Fig. 1, and example instru-ment
29、settings are shown in Table 1.4NOTE 1The instrument settings in Table 1 are only examples. Theanalyst may modify the settings as long as performance of the method hasnot been degraded. Contact the instrument manufacturer for recommendedinstrument parameters.7.1.1 An autosampler is recommended but no
30、t required toautomate sample injections and increase throughput. Autosam-plers are usually available as an option from the instrumentsmanufacturer.7.1.2 Data Acquisition SystemUse the computer hardwareand software recommended by the instrument manufacturer tocontrol the apparatus and to collect data
31、 from the detector.7.1.3 Pump TubingUse tubing recommended by instru-ment manufacturer. Replace pump tubing when worn, or whenprecision is no longer acceptable.7.1.4 Gas Diffusion MembranesAhydrophobic membranewhich allows gaseous hydrogen cyanide to diffuse from thedonor to the acceptor stream at a
32、 sufficient rate to allowdetection. The gas diffusion membrane should be replacedwhen the baseline becomes noisy or every 1 to 2 weeks.57.1.5 Use parts and accessories as directed by instrumentmanufacturer.7.2 Distillation ApparatusThe Micro-Distillation Systemdescribed below was utilized during the
33、 laboratory study todemonstrate precision and bias for this test method. A largerdistillation apparatus such as the MIDI distillation described inSection 7 of Test Methods D2036 can also be used to preparesamples prior to flow injection analysis, but the user isresponsible to determine the precision
34、 and bias.7.2.1 Micro-Distillation Apparatus consisting of a distilla-tion sample tube, hydrophobic membrane, and collector tubecontaining 1.5 mL of 1.0 M sodium hydroxide with a break-away top section, guard membrane, and cap as shown in Fig.2.67.2.2 Heater block assembly, temperature controlled, c
35、a-pable of heating the micro-distillation tubes to 120C.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of theAmericanChemical Society, where such specifi
36、cations are available.7Other grades may be used, provided it is first ascertained thatthe reagent is of sufficiently high purity to permit its usewithout lessening the accuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent
37、water that meetsthe purity specifications of Type I or Type II water, presentedin Specification D1193.8.3 Sodium Hydroxide Solution (1.00 M)Dissolve 40 gNaOH in laboratory water and dilute to 1 L.8.4 Absorber Solution for MIDI Distillations (0.25 MNaOH)Dissolve 10 g NaOH in laboratory water and dilu
38、te to1L.8.5 Acceptor Solution (0.10 M NaOH)Dissolve 4.0 gNaOH in laboratory water and dilute to 1 L.4Both the OI Analytical CN Solution and Lachat Instruments QuikChemAutomated Ion Analyzer have been found to be suitable for this analysis.5The sole source of supply of the apparatus known to the comm
39、ittee at this timeis PALL Life Sciences Part Number M5PU025, OI Analytical Part NumberA0015200, and Lachat Instruments Part Number 50398. If you are aware ofalternative suppliers, please provide this information to ASTM InternationalHeadquarters. Your comments will receive careful consideration at a
40、 meeting of theresponsible technical committee,1which you may attend.6The sole source of supply of the apparatus known to the committee at this timeis Lachat Instruments, PNA17001 (subject to US Reg. Patent No. 5,022,967). If youare aware of alternative suppliers, please provide this information to
41、ASTMInternational Headquarters. Your comments will receive careful consideration at ameeting of the responsible technical committee,1which you may attend.7Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the testing of reagent
42、s notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.TABLE 1 Flow Injection Analysis ParametersFIA Instrument Param
43、eter Recommended Method SettingPump Flow Rates 0.5 to 2 mL/minCycle Period (Total) Approximately 120 secondsSample Load Period At least enough time to completely fillthe sample loop prior to injectionInjection Valve Rinse Time BetweenSamplesAt least enough time to rinse the sampleloopPeak Evaluation
44、 Peak height or areaWorking Potential 0.0 V versus Ag/AgClFIG. 2 Micro Distillation Sample TubeD7284 13 (2017)38.6 Stock Cyanide Solution (1000 g/mL CN)Dissolve2.51 g of KCN and 2.0 g of NaOH in 1 L of water. Standardizewith silver nitrate solution as described in Test MethodsD2036, section 16.2. St
45、ore the solution under refrigeration andcheck concentration approximately every 6 months and correctif necessary. (WarningBecause KCN is highly toxic, avoidcontact or inhalation.)88.7 Intermediate Cyanide Standards:8.7.1 Intermediate Standard 1 (100 g/mL CN)Pipette10.0 mL of stock cyanide solution (
46、see 8.6) into a 100 mLvolumetric flask containing 1 mL of 1.0 M NaOH (see 8.3).Dilute to volume with laboratory water. Store under refrigera-tion. The standard should be stable for at least 2 weeks.8.7.2 Intermediate Cyanide Solution 2 (10 g/mL CN)Pipette 10.0 mL of Intermediate Cyanide Solution 1 (
47、see 8.7.1)into a 100 mL volumetric flask containing 1.0 mL of 1.00 MNaOH (see 8.3). Dilute to volume with laboratory water. Thestandard should be stable for at least 2 weeks.8.8 Working Cyanide Calibration StandardsPrepare freshdaily as described in 8.8.1 and 8.8.2 ranging in concentrationfrom 2 to
48、500 g/L CN.8.8.1 Calibration Standards (50, 100, 200, and 500 g/LCN)Pipette 50, 100, 200, and 500 L of IntermediateStandard 1 (see 8.7.1) into separate 100 mL volumetric flaskscontaining 1.0 mL of 1.00 M NaOH (see 8.3). Dilute to volumewith laboratory water.8.8.2 Calibration Standards (2, 5, and 10
49、g/L CN)Pipette 20, 50, and 100 L of Intermediate Cyanide Solution 2(see 8.7.2) into separate 100 mL volumetric flasks containing1.0 mL of 1.00 M NaOH (see 8.3). Dilute to volume withlaboratory water.8.9 Potassium Ferricyanide Stock Solution (1000 g/mL asCN)Weigh 0.2109 g K3Fe(CN)6into a 100-mL volumetricflask containing 1 mL 1 M NaOH, then dilute to volume withlaboratory water.8.9.1 Potassium Ferricyanide Spiking Solution (100 g/mLCN)Pipette 10.0 mL of potassium ferricyanide stock solu-tion into a 100 mL volumetric flask contai
