1、Designation: D 4251 89 (Reapproved 2003)Standard Test Method forActive Matter in Anionic Surfactants by PotentiometricTitration1This standard is issued under the fixed designation D 4251; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, 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 This test method describes a potentiometric titrationprocedure for determining the anionic active ma
3、tter in deter-gents. It is intended for the analysis of anionic surfactants suchas detergent range alkylbenzenesulfonates, a-olefin sulfonates,alcohol sulfates, and alcohol ethosulfates. It has not been testedfor surfactant formulations.1.2 This standard does not purport to address all of thesafety
4、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. Reviewth
5、em for hazards prior to usage.2. Referenced Documents2.1 ASTM Standards:D 459 Terminology Relating to Soaps and Other Deter-gents2D 1193 Specification for Reagent Water3D 1681 Test Method for Synthetic Anionic Active Ingredi-ent in Detergents by Cationic Titration Procedure2D 3049 Test Method for Sy
6、nthetic Anionic Ingredient byCationic Titration2E 180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial Chemicals43. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 active matterthe organic surface-active materialpresent in the detergent
7、 and defined in Terminology D 459 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 r
8、eaction 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 m
9、ost 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 D 1681) ordisulphine blue/dimidium bromide (Test Method D 3049) asindicators. One advantage of the potentiom
10、etric 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) f
11、itted with anitrate ion-selective electrode (Orion Model 93-07 Nitrate ISE,or equivalent) and a Ag/AgCl reference electrode (Metrohm1This test method is under the jurisdiction of ASTM Committee D12 on Soapsand Other Detergents and is the direct responsibility of Subcommittee D12.12 onAnalysis of Soa
12、ps and Synthetic Detergents.Current edition approved May 26, 1989. Published July 1989. Originallypublished as D 4251 83. Last previous edition D 4251 88.2Annual Book of ASTM Standards, Vol 15.04.3Annual Book of ASTM Standards, Vol 11.01.4Annual Book of ASTM Standards, Vol 15.05.TABLE 1 Active Matte
13、r Content of Various Anionic Surfactantsby the Potentiometric Titration and Two-Phase Titration MethodsAnionic SurfactantActive Matter Content, % weightPotentiometric Titration Two-PhaseTitrationOrionNO3(#1)OrionNO3(#2)“Old” HNUNO3Sulframin AOS (alpha-olefin sulfonate)41.0342.5042.6441.4940.7441.344
14、0.9141.0541.0539.21A39.26Sulframin 1298 (alkylarylsulfonate)94.1595.3194.7396.2695.6796.2694.9195.5094.9195.12B95.12NEODOLT 25-3S (alcoholethoxysulfate sodiumsalt)58.1258.8158.1257.9457.7457.9457.7557.9557.9558.19B58.24AMethylene blue method.BMixed indicator method.1Copyright ASTM International, 100
15、 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.EA 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. Us
16、e of theOrion electrode with a Metrohm E536 requires an adapter(Metrohm EA-1046/2).NOTE 1The 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. Cond
17、ition previously used electrodes by using again for thetitration of aqueous sodium lauryl sulfate with Hyamine.NOTE 2Other electrodes (for example a calomel electrode) aresuitable as the reference electrode provided they give a stable referencepotential during the titration. Reference electrodes hav
18、ing a ceramic or anasbestos junction tend to clog with use. Therefore, a ground-glass sleeveelectrode (such as the Metrohm EA 440) is suggested.7. Reagents7.1 Hyamine 1622,5diisobutylphenoxyethoxyethyl dim-ethyl benzyl ammonium chloride.7.2 Sodium Lauryl Sulfate,6primary standard (Note 3).NOTE 3Sodi
19、um lauryl sulfate must be analyzed for purity accordingto the Reagent section of Test Method D 3049, before using as a primarystandard.7.3 Water, type III reagent water conforming to Specifica-tion D 1193.8. Preparation of Standard Reagents8.1 Sodium Lauryl Sulfate Solution,43 102NWeighaccurately 11
20、.5 6 0.5 g of sodium lauryl sulfate to 0.1 mg;dissolve in water and dilute to a final volume of 1 L. Calculatethe normality of the solution with the following equation:Normality of sodium lauryl sulfate 5W!P!288.38!100!(1)where:P = purity of the sodium lauryl sulfate, weight %, andW = weight of sodi
21、um lauryl sulfate, g.8.1.1 Keep the solution no longer than 1 month beforemaking a fresh solution.8.2 Hyamine 1622 Solution,43 102NDissolve 18 6 0.5g of Hyamine 1622 in deionized water. Transfer to a 1-Lvolumetric flask. Add 0.4 mL of 50 % NaOH and dilute tovolume with water. Standardize following t
22、he same proceduredescribed for the sample titration using 5 mL of the sodiumlauryl sulfate solution. Calculate the normality of the Hyaminesolution as follows:Normality of Hyamine 1622 5A!B!C!(2)where:A = sodium lauryl sulfate solution used, mL,B = normality of sodium lauryl sulfate, andC = Hyamine
23、solution consumed during titration, mL.9. Procedure9.1 Add to a 150-mL beaker a known weight of detergentsample together with enough water to make 50 mL of solution(Note 4). The solution should cover the sensing tips of theelectrodes. Titrate initially by adding Hyamine solution atapproximately 0.5
24、mL/min while stirring constantly. As theinflection point is approached, reduce the addition rate, andcontinue titrating well past the inflection in the titration curve.(Automatic titrators can be preset to automatically slow downthe addition rate as the inflection point is approached.)NOTE 4To deter
25、mine the amount of sample needed for an approxi-mate 3.75-mL titration (0.15 meq) use the following equation:W 50.015!MD!(3)where:W = weight of sample to be taken for analysis, g,M = average equivalent weight of the anionic active matter present,andD = approximate concentration of anionic active mat
26、ter expected,weight %.9.1.1 To obtain accurate weights of sample, it is convenientto make up an aqueous solution (for example 250 mL) and takean aliquot corresponding to 0.15 meq of active matter.9.1.2 The electrode should be cleaned between each titra-tion. A satisfactory procedure is to first rins
27、e it with water, thenwith alcohol (ethyl alcohol) (Note 5) and again with waterfollowed by wiping the surface with a Kimwipe.NOTE 5The electrode can be quickly washed with ethyl alcohol whenfollowed immediately by a water rinse. Prolonged contact of the electrodewith alcohol or other organic solvent
28、 can cause failure of the electrodemembrane.9.2 Graphically select the inflection point of the curve onthe recorder chart. Typical titration curves of several anionicsurfactants are shown in Fig. 1.10. Calculation10.1 Calculate the anionic active matter content of thesample as follows:Anionic Active
29、 Matter, % w 5V!N!M!10!W!(4)where:V = Hyamine 1622 solution consumed in titration, mL,N = normality of Hyamine,W = weight of sample g, andM = average equivalent weight of the anionic active mat-ter present.10.2 Calculate the milliequivalents of active matter per 100g sample as follows:meq Active Mat
30、ter/100 g 5V!N!100!W!(5)5Available from Gallard Schlesinger Chemical Manufacturing Corp., 584Mineola Ave., Carle Place, NY 11514.6Available from British Drug House, LTD, or in the U.S. from GallardSchlesinger Chemical Mfg. Corp., 584 Mineola Ave., Carle Place, NY 11514.D 4251 89 (2003)2where V, N, a
31、nd W are as listed previously.11. Precision11.1 The following criteria should be used to judge theacceptability of the results (Note 6):7,811.1.1 Repeatability (Single Analyst)The standard devia-tion of results (each the average of duplicates), obtained by thesame analyst on different days, has been
32、 estimated to be 0.66weight % relative at 28 df. Two such averages should beconsidered suspect (95 % confidence level) if they differ bymore than 1.9 weight % relative.11.1.2 Reproducibility (multilaboratory)The standard de-viation of results (each the average of duplicates), obtained tobe 1.3 weigh
33、t % relative at 6 df. Two such averages should beconsidered suspect (95 % confidence level) if they differ bymore than 4.5 weight % relative.11.1.3 Checking Limits for DuplicatesReport the weight% active matter of the sample to the nearest 0.1 weight %.Duplicate runs that agree within 1.8 weight % r
34、elative areacceptable for averaging (95 % confidence level).NOTE 6The precision data were derived from results of the coopera-tive tests by eight laboratories on the following surfactants (equivalentweights in parenthesis): sodium lauryl sulfate (302), alcohol ethoxysulfateammonium salt (434), a-ole
35、fin sulfonate (325), alkylaryl sulfonic acid(318).12. Keywords12.1 active matter; anionic surfactants; titration7Data supporting the precision statements are on file at ASTM Headquarters, 100Barr Harbor Drive, West Conshohocken, PA 19428, Research Report No. D12-1003.8The statistical analysis was pe
36、rformed in accordance with Practice E 180 fordeveloping precision estimates.FIG. 1 Potentiometric Titration Curves of Various Anionic Surfactants versus 0.03757 N Hyamine 1622 Using the Orion Model 93-07Nitrate ISED 4251 89 (2003)3ASTM International takes no position respecting the validity of any p
37、atent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revisi
38、on at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your co
39、mments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrigh
40、ted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 4251 89 (2003)4
