ASTM_D_4608_-_89_2009.pdf

Designation:D460889(Reapproved 2009)Standard Test Method forCitrate in Detergents1This standard is issued under the fixed designation D4608;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.Scope1.1 This test method covers a potentiometric titration pro-cedure for the determination of citrate in liquid and powderdetergents.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 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-bility of regulatory limitations prior to use.Material SafetyData Sheets are available for reagents and materials.Reviewthem for hazards prior to usage.Specific safety precautions aregiven in Section 8.2.Referenced Documents2.1 ASTM Standards:2E70 Test Method for pH of Aqueous Solutions With theGlass ElectrodeE180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals(Withdrawn 2009)33.Summary of Test Method3.1 The sample is titrated in an aqueous solution buffered atpH 8.5,with standard copper sulfate solution.The endpoint isdetected potentiometrically using a copper ion selective elec-trode.The citrate content is calculated from the amount ofstandard copper sulfate solution consumed.4.Significance and Use4.1 This test method is suitable in research,development,and manufacturing control to monitor the level of citrate,asequestering agent,in powder and liquid detergents.4.2 Accurate determination of sequestering agent is impor-tant in evaluating cost and performance of detergent products.5.Interferences5.1 Other complexing agents such as nitrilotriacetic acid(NTA),ethylenedinitrilotetraacetic acid(EDTA),phosphates,etc.will titrate as citrate in this method.For accurate citratedeterminations,such complexing agents must be absent.6.Apparatus6.1 pH Meter,with millivolt capability.46.2 Copper Ion Selective Electrode.56.3 Calomel Reference Electrode.66.4 Glass Electrode Triple Purpose.76.5 Buret,semi-micro,25 mL capacity with 0.1 mL gradu-ations.6.6 Magnetic Stirrer,and TFE-fluorocarbon-coated mag-netic stirring bars.7.Reagents7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.Unless otherwise indicated,it is intended thatall reagents shall conform to specifications of the Committeeon Analytical Reagents of the American Chemical Society,where such specifications are available.8Other grades may beused,provided it is first ascertained that the reagent is of1This test method is under the jurisdiction of ASTM Committee D12 on Soapsand Other Detergents and is the direct responsibility of Subcommittee D12.12 onAnalysis and Specifications of Soaps,Synthetics,Detergents and their Components.Current edition approved Oct.1,2009.Published March 2010.Originallyapproved in 1986.Last previous edition approved in 2003 as D4608 89(2003).DOI:10.1520/D4608-89R09.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.4An automatic titrator may be used.5Orion Model 94-29A or equivalent has been found suitable for this purpose.Available from Orion Inc.6Orion Model 90-22 or equivalent has been found suitable for this purpose.Available from Orion Inc.7Corning Model No.476022 or equivalent has been found suitable for thispurpose.Available from Corning Inc.8Reagent 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 the United States Pharmacopeiaand National Formulary,U.S.Pharmacopeial Convention,Inc.(USPC),Rockville,MD.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 sufficiently high purity to permit its use without lessening theaccuracy of the determination.7.2 Purity of WaterUnless otherwise indicated,referenceto water shall be understood to mean distilled water or water ofequal purity.7.3 Hydrochloric Acid Solution(1+1)Slowly mix 1 vol-ume of concentrated hydrochloric acid(sp gr 1.19)with 1volume of water.7.4Sodium Hydroxide Solution(20%)Prepare a 20%aqueous solution of sodium hydroxide.7.5 Sodium Hydroxide Solution(0.1 N)Prepare a 0.1 Naqueous solution of sodium hydroxide.7.6 Hydrochloric Acid Solution(0.1 N)Prepare a 0.1 N