1、Designation: D 1681 05Standard Test Method forSynthetic Anionic Active Ingredient in Detergents byCationic Titration Procedure1This standard is issued under the fixed designation D 1681; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 conve
3、nient 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 accur
4、acy 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
5、 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 ob
6、tained 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
7、 converted to thesodium salt before proceeding with this analysis.1.3 The analytical procedures appear in the following order:SectionsSeparation of Alcohol-Soluble Matter 8 and 9Separation of Oil-Free Sulfonate 10 and 11Determination of Sodium Chloride (NaCl) Content 12-17Characterization of Anionic
8、 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 Reagent 25-29Quantitative Determination of Anionic Surfactant
9、by CationicTitration30-331.4 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 pri
10、or to use. For a specifichazards statement, see Section 7.2. Referenced Documents2.1 ASTM Standards:2D 1193 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 sa
11、lts, 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 titratesimi
12、lar 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 cleanin
13、g 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. Sinc
14、e the cationic titration is con-ducted under acidic conditions, soap does not interfere. Soapmust 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 indicated, it
15、 is intended that1This test method is under the jurisdiction of ASTM Committee D12 on Soapsand Other Detergents and is the direct responsibility of Subcommittee D12.12 on theAnalysis of Soaps and Synthetic Detergents.Current edition approved May 1, 2005. Published June 2005. Originallyapproved in 19
16、59. Last previous edition approved in 1997 as D1681 92(1997).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.
17、1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.all reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.3Other grades may beus
18、ed, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.6.2 Unless otherwise indicated, references to water shall beunderstood to mean reagent water conforming to SpecificationD 1193.37. Hazards7.1 All r
19、eagents and chemicals should be handled with care.Before using any chemical, read and follow all safety precau-tions and instructions on the manufacturers label or MSDS(Material Safety Data Sheet).SEPARATION OF ALCOHOL-SOLUBLE MATTER8. Solvent8.1 Ethyl AlcoholFreshly boiled ethyl alcohol conformingt
20、o Formula No. 3A or No. 30 of the U.S. Bureau of InternalRevenue. The alcohol should not be neutralized. Redistilledalcohol must be used if alkali absorption is more than 0.2 mLof 100 mL of 0.1 N NaOH solution.9. Procedure9.1 Weigh out a sample, to the nearest 0.01 g, to correspondto surfactants wit
21、h the following ranges of active ingredientcontents and transfer to a 600-mL beaker:Active Ingredient, wt % Weight of Sample, g10 to 25 3025 to 40 1540 to 60 1060 to 80 7Over 80 5.59.2 Add 300 to 350 mL of hot alcohol. Cover with a watchglass and heat on the steam bath for at least 2 h, stirringfreq
22、uently to disperse solids and break up lumps. Have aprepared Gooch crucible or sintered glass filter inserted in the1000-mL vacuum flask.9.3 At the end of 2 h, remove the beaker from the bath anddecant the alcohol solution rapidly through the filter, retainingas much as possible of the residue in th
23、e beaker. Add 50 mL ofhot alcohol to the residue in the beaker. Heat to boiling on a hotplate, breaking up any lumps of the residue. Decant the alcoholthrough the filter as before. Repeat with another 50-mL portionof hot alcohol.9.4 Evaporate the residual alcohol from the residue in thebeaker on the
24、 steam bath, stirring at intervals, especially nearthe end. Dissolve the residue in the beaker with 10 mL of hotwater, heating on the steam bath until solution is effected.9.5 Dilute the water solution with 200 mL of hot alcohol,bring to a boil on the steam bath, and filter. Transfer theprecipitate
25、onto the filter with the aid of hot alcohol andpoliceman. Wash the beaker and the residue with hot alcoholthree or four times. For samples being prepared for Part I of thecharacterization of anionic surfactant (Sections 18-20 ), con-tinue as directed in 9.6. For samples being prepared foreventual us
26、e in Part II of the characterization of anionicsurfactant (Sections 21-24), continue in accordance with theseparation of oil-free sulfonate (Sections 10 and 11).9.6 Transferc the filtrate to a 1000-mL beaker. Wash thefilter flask with alcohol and 10 mL of water followed by analcohol wash. Evaporate
27、the filtrate to about 400 mL andtransfer to a 1000-mL volumetric flask. Dilute with water tomark. Designate as Solution I and reserve for use in Part I ofthe characterization of the anionic surfactant (Sections 18-20).SEPARATION OF OIL-FREE SULFONATE10. Reagents10.1 Ethyl AlcoholSee Section 8.10.2 P
28、etroleum Ether, having a boiling point of 30 to 60C.11. Procedure11.1 Transfer the alcohol solution quantitatively to a1000-mL beaker (with the 100-mL volume marked on the side)and concentrate to 100 mL on a steam bath or hot water bath.Transfer the concentrate quantitatively to a 500-mL, pear-shape
29、d separatory funnel by rinsing the beaker with 100 mL ofwater in several portions. Add the remainder of water to thefunnel to bring the total volume to 200 mL.11.2 Extract the aqueous-alcoholic solution with three 50-mL portions of petroleum ether, using additional separatoryfunnels. Combine the eth
30、er extracts and wash with 3 to 50- mLportions of 50 % aqueous ethanol. Add the aqueous ethanolwashings to the extracted aqueous alcohol solution. Discard thepetroleum ether extracts. Transfer the oil-free aqueous alco-holic solution quantitatively to a 1000-mL beaker by rinsingthe separatory funnel
31、with small portions of water. Heat thesolution in a 400-mL beaker in a water bath at 40 to 50C in ahood to vent off petroleum ether fumes. When free of ether,transfer the oil-free salt-free solution quantitatively to a1000-mLvolumetric flask.Add 300 mLof alcohol and dilute tovolume with water. Desig
32、nate as Solution II and reserve for usein Part II of the characterization of the anionic surfactant(Sections 21-24).DETERMINATION OF SODIUM CHLORIDE (NaCl)CONTENT12. Scope12.1 Sections 13-17 cover the determination of the sodiumchloride content of the surfactant in order that appropriatecorrections
33、can be made in the values obtained in the charac-terization of the anionic active ingredients and the quantitativedetermination of an unknown anionic active ingredient.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testi
34、ng 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.D168105213. Apparatus13.1 Stirrer Motor and Small
35、 Glass Rod Stirrer.13.2 Potentiometer.413.3 Calomel Reference Electrode, saturated.13.4 Silver Wire Electrode, 1mm in diameter by 120 mm inlength.14. Reagents and Materials14.1 Acetone.14.2 Ethyl AlcoholFreshly boiled ethyl alcohol conform-ing to Formula No. 3Aor No. 30 of the U.S. Bureau of Interna
36、lRevenue.14.3 Methyl Orange Indicator.14.4 Nitric Acid (1+1)Mix 1 volume of HNO3(sp gr1.42) containing 0.3 % sodium nitrite (NaNO2) with 1 volumeof water.14.5 Nitric Acid (1+4)Mix 1 volume of nitric acid(HNO3, sp gr 1.42) with 4 volumes of water.14.6 Silver Nitrate, Standard Solution (0.2 N)Prepare
37、andstandardize a 0.2 N silver nitrate (AgNO3) solution as follows:Weigh 17 g of AgNO3to the nearest 1 mg. Dissolve in waterand transfer to a 500-mL volumetric flask. Dilute to the mark.Standardize as follows:14.6.1 Dry about 10 g of NaCl at 110C to constant weight.Weigh about 2.00 g of the dried NaC
38、l to the nearest 1 mg.Dissolve in a solvent consisting of 60 % water and 40 %alcohol. Transfer to a 100-mL volumetric flask and dilute to themark with solvent. Pipet 100 mL of the NaCl solution to abeaker and titrate with the AgNO3solution as described inSection 15.14.6.2 Calculate the normality of
39、the AgNO3solution asfollows:Normality 5 A 3 100!/B 3 58.45! (1)where:A = grams of NaCl used, andB = millilitres of AgNO3solution required for titration ofthe NaCl.15. Procedure for Qualitative Determination15.1 Place 5 mL of Solution I or II in a test tube and acidifywith HNO3(1+4). Add several drop
40、s of AgNO3solution. If thesolution becomes turbid, it contains NaCl. Presence of soapwill also cause turbidity. Soap must not be present with thesurfactant to be characterized.16. Procedure for Quantitative Determination16.1 Pipet 100-mL portions of Solution I or II into each oftwo 400-mL beakers. A
41、dd 2 drops of methyl orange indicatorsolution and acidify to the acid color by using HNO3(1+4).Warm slightly and stir to effect maximum solution. Add 50 mLof acetone.16.2 Clean the silver electrode in the HNO3(1+1) contain-ing NaNO2. Set up the titration cell with the silver electrodeconnected to th
42、e top terminal, the saturated calomel cellconnected to the bottom terminal. Set the pH meter on + mV.Start the stirring and titrate the solution potentiometrically asfollows:16.2.1 Add 0.5 mL ofAgNO3solution and measure the emf.If appreciable chloride is present, the emf should be in therange of 100
43、 mV.16.2.2 Add AgNO3solution slowly in 2 to 3-mL portionsuntil the emf reaches 200 mV. Stir well.16.2.3 Add AgNO3solution in 0.1-mL portions, allowingsufficient time after each addition for the solution to reachequilibrium (60 to 80 s). Measure the emf (stirrer off) at each0.1-mL point.16.2.4 Calcul
44、ate the end point by the rate of change method(Note 1). The end point is usually in the range from 260 to 270mV.NOTE 1ExampleThe method for determining the maximum rate ofchange is as follows:mL emf DE DE821.2 210 10 1021.3 220 20 17A21.4 240 37 1221.5 277 2521.6 302_AMaximum rate of change.End poin
45、t 5 21.3 11717 1 123 0.1 (2)5 21.46 mL (2)16.3 Run a blank and subtract the value obtained from thevalue calculated in 16.2.4.17. Calculations17.1 Calculate the grams of NaCl present in 250 mL ofSolution I or II as follows:A 5 B 3 N 3 0.05845 3 250!/100 (3)where:A = grams of NaCl present in 250 mL o
46、f Solution I or II,B = millilitres of AgNO3solution required for titration ofthe NaCl, andN = normality of the AgNO3solution.17.2 Calculate the grams of NaCl equivalent to sodiumsulfate (Na2SO4) present in 250 mL of Solution I or II asfollows:A 5 B 3 71.03!/58.45 (4)where:A = grams of Na2SO4equivale
47、nt to the NaCl in 250 mL ofSolution I or II, andB = grams of NaCl present in 250 mL of Solution I or II.4The Beckman Model G pH meter, or its equivalent, has been found satisfactoryfor this purpose.D1681053CHARACTERIZATION OF ANIONICSURFACTANT STANDARDPart I. Determination of Surfactant, SO3Content,
48、 and Solution Molarity18. Reagents18.1 Ethyl AlcoholSee Section 6.18.2 Sulfuric Acid (sp gr 1.84)Concentrated sulfuric acid(H2SO4).19. Procedure19.1 Pipet 250 mL of Solution I (9.6) into each of two250-mL beakers. Evaporate to near dryness on a steam bath orunder an infrared lamp. Transfer quantitat
49、ively the concen-trated solution from the beaker into a tared, ignited, platinumcrucible. Wash the beaker with small amounts of alcohol andwater to ensure complete transfer to the crucible.19.2 Evaporate the contents in the crucible to dryness on asteam bath or under an infrared lamp, adding small portions ofalcohol to aid in removal of water.19.3 Carefully heat the crucible, supported on a quartztriangle, over a small flame until the sample is charred and nolonger smoking. Avoid spattering. Cool and add 3 to 4 drops ofH2SO4. Heat carefully aga
