ASTM_D_7237_-_18.pdf

Designation:D723718Standard Test Method forFree Cyanide and Aquatic Free Cyanide with Flow InjectionAnalysis(FIA)Utilizing Gas Diffusion Separation andAmperometric Detection1This standard is issued under the fixed designation D7237;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 parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This test method is used to establish the concentration offree cyanide in an aqueous wastewater,effluent and in-streamfree cyanide concentrations after mixing treated water withreceiving water.The test conditions of this test method are usedto measure free cyanide(HCN and CN)and cyanide bound inthe metal-cyanide complexes that are easily dissociated intofree cyanide ions at the pH of 6.Free cyanide is determined atpH 6 at room temperature.The aquatic free cyanide can bedetermined by matching the pH to the water in the receivingenvironment in the range of pH 6 to 8.The extent of HCNformation is less dependent on temperature than the pH;however,the temperature can be regulated if deemed necessaryfor aquatic free cyanide to further simulate the actual aquaticenvironment.1.2 The free cyanide test method is based on the sameinstrumentation and technology that is described in TestMethod D6888,but employs milder conditions(pH 68 bufferversus HCl or H2SO4in the reagent stream),and does notutilize ligand displacement reagents.1.3 The aquatic free cyanide measured by this procedureshould be similar to actual levels of HCN in the originalaquatic environment.This in turn may give a reliable index oftoxicity to aquatic organisms.1.4 This procedure is applicable over a range of approxi-mately 5 to 500 g/L(parts per billion)free cyanide.Sampledilution may increase cyanide recoveries depending on thecyanide speciation;therefore,it is not recommended to dilutesamples.Higher concentrations can be analyzed by increasingthe range of calibration standards or with a lower injectionvolume.In accordance with Guide E1763 and Practice D6512the lower scope limit was determined to be 9 g/L forchlorinated gold leaching barren effluent water and the IQE10%is 12 g/L in the gold processing detoxified reverse osmosispermeate waste water sample matrix.1.5 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.6 This test method is not recommended for samples thatcontain reduced sulfur compounds such as sulfides.1.7 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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.Specific hazard statements are given in 8.6 and Section 9.1.8 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles 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 WaterD1293 Test Methods for pH of WaterD2036 Test Methods 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 WaterD4658 Test Method for Sulfide Ion in WaterD4841 Practice for Estimation of Holding Time for WaterSamples Containing Organic and Inorganic ConstituentsD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water Analysis1This 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 Dec.1,2018.Published January 2019.Originallyapproved in 2006.Last previous edition approved in 2015 as D7237 15a.DOI:10.1520/D7237-18.2For 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 page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright 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 theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 D6512 Practice for In