1、Designation: D4251 89 (Reapproved 2009)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 revisio
2、n, 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 matte
3、r 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 The values stated in SI units are to be regarded asstandard. N
4、o 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-bil
5、ity 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 Met
6、hod for SyntheticAnionicActive 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 Chemicals3. Terminology3.1 Def
7、initions 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 titratedpotentiometrical
8、ly 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 proba
9、bly 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
10、(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
11、.6. Apparatus6.1 Potentiometric Titration Assembly, consisting of anautomatic titrator (Metrohm E536 or equivalent) fitted with a1This 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 Speci
12、fications of Soaps, Synthetics, Detergents and their Components.Current edition approved Oct. 1, 2009. Published December 2009. Originallyapproved in 1983. Last previous edition approved in 2003 as D4251 89(2003).DOI: 10.1520/D4251-89R09.2For referenced ASTM standards, visit the ASTM website, www.as
13、tm.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.TABLE 1 Active Matter Content of Various Anionic Surfactantsby the Potentiometric Titration and Two-Phase Titration Methods
14、Anionic SurfactantActive Matter Content, % weightPotentiometric Titration Two-PhaseTitrationOrionNO3(#1)OrionNO3(#2)“Old” HNUNO3Sulframin AOS (alpha-olefin sulfonate)41.0342.5042.6441.4940.7441.3440.9141.0541.0539.21A39.26Sulframin 1298 (alkylarylsulfonate)94.1595.3194.7396.2695.6796.2694.9195.5094.
15、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 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.nitrate ion-selective
16、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 dur
17、ing titration. Use 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 r
18、ecom-mended. Condition 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. Referen
19、ce electrodes having 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, diisobutylphenoxyethoxyethyl dim-ethyl benzyl ammonium chloride.7.2 Sodium Lauryl Sulfate, primary standard (N
20、ote 3).NOTE 3Sodium lauryl sulfate must be analyzed for purity accordingto the Reagent section of Test Method D3049, before using as a primarystandard.7.3 Water, type III reagent water conforming to Specifica-tion D1193.8. Preparation of Standard Reagents8.1 Sodium Lauryl Sulfate Solution,43 102NWei
21、ghaccurately 11.5 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 =
22、 weight of sodium 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. Standard
23、ize following the 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,
24、andC = Hyamine 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 atapp
25、roximately 0.5 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.
26、)NOTE 4To determine 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 ani
27、onic active matter 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.Asatisfactory procedure is
28、to first rinse 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 or
29、ganic solvent 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:A
30、nionic Active 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:m
31、eq Active Matter/100 g 5V!N!100!W!(5)where V, N, and W are as listed previously.11. Precision11.1 The following criteria should be used to judge theacceptability of the results (Note 6):3,43A research report supporting the precision statements is on file at ASTMInternational Headquarters. Request RR
32、: D12-1003.D4251 89 (2009)211.1.1 Repeatability (Single Analyst)The standard devia-tion of results (each the average of duplicates), obtained by thesame analyst on different days, has been estimated to be 0.66weight % relative at 28 df. Two such averages should beconsidered suspect (95 % confidence
33、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 weight % relative at 6 df. Two such averages should beconsidered suspect (95 % confidence level) if they differ bymor
34、e 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 % relative areacceptable for averaging (95 % confidence level).NOTE 6The precision data were derived from results o
35、f the coopera-tive tests by eight laboratories on the following surfactants (equivalentweights in parenthesis): sodium lauryl sulfate (302), alcohol ethoxysulfateammonium salt (434), a-olefin sulfonate (325), alkylaryl sulfonic acid(318).12. Keywords12.1 active matter; anionic surfactants; titration
36、4The statistical analysis was performed in accordance with Practice E180 fordeveloping precision estimates.FIG. 1 Potentiometric Titration Curves of Various Anionic Surfactants versus 0.03757 N Hyamine 1622 Using the Orion Model 93-07Nitrate ISED4251 89 (2009)3ASTM International takes no position re
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39、national Headquarters. Your comments 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 b
40、elow.This standard is copyrighted 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D4251 89 (2009)4
