ASTM_D_4251_-_89_2016.pdf

Designation:D425189(Reapproved 2016)Standard Test Method forActive Matter in Anionic Surfactants by PotentiometricTitration1This standard is issued under the fixed designation D4251;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 describes a potentiometric titrationprocedure for determining the anionic active matter in deter-gents.It is intended for the analysis of anionic surfactants suchas detergent range alkylbenzenesulfonates,-olefin sulfonates,alcohol sulfates,and alcohol ethosulfates.It has not been testedfor surfactant formulations.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.2.Referenced Documents2.1 ASTM Standards:2D459 Terminology Relating to Soaps and Other DetergentsD1193 Specification for Reagent WaterD1681 Test Method for Synthetic Anionic Active Ingredientin Detergents by Cationic Titration ProcedureD3049 Test Method for Synthetic Anionic Ingredient byCationic TitrationE180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals(Withdrawn 2009)33.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 active matterthe organic surface-active materialpresent in the detergent and defined in Terminology D459 asactive ingredient of a synthetic detergent.4.Summary of Test Method4.1 A detergent sample containing active matter is titratedpotentiometrically in an aqueous medium with a standardsolution of Hyamine 1622 using a nitrate ion-selective elec-trode.The titration reaction involves the formation of acomplex between the cationic quaternary ammonium titrant(Hyamine 1622)and the anionic surfactant which precipitates.The nitrate electrode probably responds to the concentration ofunreacted anionic surfactant.5.Significance and Use5.1 Anionic surfactants are the most widely used of thesynthetic detergents.ASTM methods in current use for theirdetermination involve two-phase aqueous/chloroform titrationswith the organic dyes methylene blue(Test Method D1681)ordisulphine blue/dimidium bromide(Test Method D3049)asindicators.One advantage of the potentiometric method is thatit eliminates the use of chloroform whose use is restricted forenvironmental and toxicological reasons.5.2 This test method is intended for use as described in 1.1.6.Apparatus6.1 Potentiometric Titration Assembly,consisting of anautomatic titrator(Metrohm E536 or equivalent)fitted with anitrate ion-selective electrode(Orion Model 93-07 Nitrate ISE,or equivalent)and a Ag/AgCl reference electrode(MetrohmEA 440 or equivalent)together with a buret assembly having a5-mL buret(Metrohm E575)and 150-mL beaker.A TFE-fluorocarbon star-head stirring bar can be used to providemixing and eliminate foaming during titration.Use of theOrion electrode with a Metrohm E536 requires an adapter(Metrohm EA-1046/2).NOTE1The conditioning of the electrode is essential for obtaining agood break in the titration curve.Conditioning new electrodes in 0.01 MNaNO3aqueous solution for 60 min(or more)prior to use is recom-mended.Condition previously used electrodes by using again for the1This 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 July 1,2016.Published August 2016.Originallyapproved in 1983.Last previous edition approved in 2009 as D4251 89(2009).DOI:10.1520/D4251-89R16.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 titration of aqueous sodium lauryl sulfate with Hyamine.NOTE2Other electrodes(for example a calomel electrode)aresuitable as the reference electrode provided they give a stable referencepotential during the titration.Reference electrodes having a ceramic or anasbestos junction tend to clog with use.Therefore,a ground-glass sleeveelectrode(such as the Metrohm EA 440)is suggeste