ASTM D4251-89(1995)e1

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
e1
Designation: D 4251 – 89 (Reapproved 1995)
Standard Test Method for
Active Matter in Anionic Surfactants by Potentiometric
Titration
This standard is issued under the fixed designation D 4251; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Keywords were added editorially in February 1995.
TABLE 1 Active Matter Content of Various Anionic Surfactants
1. Scope
by the Potentiometric Titration and Two-Phase Titration Methods
1.1 This test method describes a potentiometric titration
Active Matter Content, % weight
procedure for determining the anionic active matter in deter-
Potentiometric Titration Two-
Anionic Surfactant
gents. It is intended for the analysis of anionic surfactants such Orion Orion “Old” HNU Phase
− − −
NO (#1) NO (#2) NO Titration
3 3 3
as detergent range alkylbenzenesulfonates, a-olefin sulfonates,
A
Sulframin AOS (alpha- 41.03 41.49 40.91 39.21
alcohol sulfates, and alcohol ethosulfates. It has not been tested
olefin sulfonate) 42.50 40.74 41.05 39.26
for surfactant formulations. 42.64 41.34 41.05
B
Sulframin 1298 (alkylaryl 94.15 96.26 94.91 95.12
1.2 This standard does not purport to address all of the
sulfonate) 95.31 95.67 95.50 95.12
safety concerns, if any, associated with its use. It is the
94.73 96.26 94.91
B
responsibility of the user of this standard to establish appro- NEODOLT 25-3S (alcohol 58.12 57.94 57.75 58.19
ethoxysulfate sodium 58.81 57.74 57.95 58.24
priate safety and health practices and determine the applica-
salt) 58.12 57.94 57.95
bility of regulatory limitations prior to use. Material Safety
A
Methylene blue method.
Data Sheets are available for reagents and materials. Review
B
Mixed indicator method.
them for hazards prior to usage.
potentiometrically in an aqueous medium with a standard
2. Referenced Documents
solution of Hyamine 1622 using a nitrate ion-selective elec-
2.1 ASTM Standards:
trode. The titration reaction involves the formation of a
D 459 Terminology Relating to Soaps and Other Deter-
2 complex between the cationic quaternary ammonium titrant
gents
(Hyamine 1622) and the anionic surfactant which precipitates.
D 1193 Specification for Reagent Water
The nitrate electrode probably responds to the concentration of
D 1681 Test Method for Synthetic Anionic Active Ingredi-
unreacted anionic surfactant.
ent in Detergents by Cationic Titration Procedure
D 3049 Test Method for Synthetic Anionic Ingredient by
5. Significance and Use
Cationic Titration
5.1 Anionic surfactants are the most widely used of the
E 180 Practice for Determining the Precision of ASTM
synthetic detergents. ASTM methods in current use for their
Methods for Analysis and Testing of Industrial Chemicals
determination involve two-phase aqueous/chloroform titrations
with the organic dyes methylene blue (Test Method D 1681) or
3. Terminology
disulphine blue/dimidium bromide (Test Method D 3049) as
3.1 Definitions of Terms Specific to This Standard:
indicators. One advantage of the potentiometric method is that
3.1.1 active matter—the organic surface-active material
it eliminates the use of chloroform whose use is restricted for
present in the detergent and defined in Terminology D 459 as
environmental and toxicological reasons.
active ingredient of a synthetic detergent.
5.2 This test method is intended for use as described in 1.1.
4. Summary of Test Method
6. Apparatus
4.1 A detergent sample containing active matter is titrated
6.1 Potentiometric Titration Assembly, consisting of an
automatic titrator (Metrohm E536 or equivalent) fitted with a
This test method is under the jurisdiction of ASTM Committee D-12 on Soaps
nitrate ion-selective electrode (Orion Model 93-07 Nitrate ISE,
and Other Detergents and is the direct responsibility of Subcommittee D12.12 on
or equivalent) and a Ag/AgCl reference electrode (Metrohm
Analysis of Soaps and Synthetic Detergents.
Current edition approved May 26, 1989. Published July 1989. Originally
EA 440 or equivalent) together with a buret assembly having a
published as D 4251 – 83. Last previous edition D 4251 – 88.
5-mL buret (Metrohm E575) and 150-mL beaker. A TFE-
Annual Book of ASTM Standards, Vol 15.04.
fluorocarbon star-head stirring bar can be used to provide
Annual Book of ASTM Standards, Vol 11.01.
Annual Book of ASTM Standards, Vol 15.05. mixing and eliminate foaming during titration. Use of the
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 4251
Orion electrode with a Metrohm E536 requires an adapter (Note 4). The solution should cover the sensing tips of the
(Metrohm EA-1046/2). electrodes. Titrate initially by adding Hyamine solution at
approximately 0.5 mL/min while stirring constantly. As the
NOTE 1—The conditioning of the electrode is essential for obtaining a
inflection point is approached, reduce the addition rate, and
good break in the titration curve. Conditioning new electrodes in 0.01 M
continue titrating well past the inflection in the titration curve.
NaNO aqueous solution for 60 min (or more) prior to use is recom-
mended. Condition previously used electrodes by using again for the (Automatic titrators can be preset to automatically slow down
titration of aqueous sodium lauryl sulfate with Hyamine.
the addition rate as the inflection point is approached.)
NOTE 2—Other electrodes (for example a calomel electrode) are
NOTE 4—To determine the amount of sample needed for an approxi-
suitable as the reference electrode provided they give a stable reference
mate 3.75-mL titration (0.15 meq) use the following equation:
potential during the titration. Reference electrodes having a ceramic or an
asbestos junction tend to clog with use. Therefore, a ground-glass sleeve
~0.015!M
W 5 (3)
electrode (such as the Metrohm EA 440) is suggested.
~D!
7. Reagents
where:
W 5 weight of sample to be taken for analysis, g,
7.1 Hyamine 1622, diisobutylphenoxyethoxyethyl dim-
M 5 average equivalent weight of the anionic active matter present,
ethyl benzyl ammonium chloride.
and
7.2 Sodium Lauryl
...