ASTM_D_1681_-_05_2014.pdf

Designation:D168105(Reapproved 2014)Standard Test Method forSynthetic Anionic Active Ingredient in Detergents byCationic Titration Procedure1This standard is issued under the fixed designation D1681;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 Direct titration of an anionic surfactant with a standard-ized cationic reagent is a simple and convenient method for thequantitative determination of the content of active ingredient.The end point is detffected by the transfer of a colored complexfrom an organic solvent phase to an aqueous phase.Therelationship between anionic and cationic agents is not alwaysstoichiometric,and for maximum accuracy the anionic type ofinterest should first be characterized and then used to standard-ize the cationic reagent.In most cases,however,the differentanionic surfactants likely to be encountered react in the sameproportions.That is,a cationic titrating solution standardizedagainst a characterized anionic agent can be used to analyzeother anionics of known molecular weights.1.2 This test method is applicable to alkylaryl sulfonatesand fatty alkyl sulfates.Low results are obtained with alkyl-benzene sulfonates having the alkyl chain length less than eightcarbon atoms.Low results are also obtained for alkyl sulfateswith the alkyl chain length of less than twelve carbon atoms.The anionic surfactants characterized in accordance withSections 17 23 should be the sodium salt and not amine,ammonium,or potassium salts.In case only amine or ammo-nium salts are available,they should be first converted to thesodium salt before proceeding with this analysis.1.3 The analytical procedures appear in the following order:SectionsSeparation of Alcohol-Soluble Matter8 and 9Separation of Oil-Free Sulfonate10 and 11Determination of Sodium Chloride(NaCl)Content12 17Characterization of Anionic Surfactant Standard:Part I.Determination of Surfactant,SO3Content,and SolutionMolarity18 20Part II.Determination of Surfactant,SO3and Active IngredientContents Combining Weight,and Solution Molarity21 24Standardization of Cationic Reagent25 29Quantitative Determination of Anionic Surfactant by CationicTitration30 331.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 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.For a specifichazards statement,see Section 7.2.Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent Water3.Summary of Test Method3.1 This test method involves isolating alkylaryl sulfonateor fatty alkyl sulfate by extraction with ethyl alcohol to removeinorganic salts,extracting the alcohol-soluble material withpetroleum ether to remove unsulfonatable matter,correctingfor sodium chloride present,and determining the active ingre-dient combining weight.The characterized surfactant is used tostandardize a cationic reagent which in turn is used to titratesimilar anionic surfactants.4.Significance and Use4.1 This test method determines anionic detergents com-monly found in laundry,dishwashing,and other cleaningmaterials.Accurate determination of the anionic active sub-stance is highly important in assessing the cost and effective-ness of such cleaning substances.5.Interferences5.1 With the exception of picrate,perchlorate,thiocyanate,nitrate,dichromate,and chromate,common inorganic anionsand low molecular weight organic anions do not interfere withthis analysis.However,sulfonates of xylene,cunene,or tolu-ene interfere positively.Since the cationic titration is con-ducted under acidic conditions,soap does not interfere.Soap1This test method is under the jurisdiction of ASTM Committee D12 on Soapsand Other Detergentsand is the direct responsibility of Subcommittee D12.12 onAnalysis and Specifications of Soaps,Synthetics,Detergents and their Components.Current edition approved Jan.1,2014.Published February 2014.Originallyapproved in 1959.Last previous edition approved in 2005 as D1681 05.DOI:10.1520/D1681-05R14.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 must not be present in the anionic surfactant characterized inaccordance with Sections 17 23.6.Reagents6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.Unless otherwise ind