Significance and Use
4.1 This test method determines anionic detergents commonly found in laundry, dishwashing, and other cleaning materials. Accurate determination of the anionic active substance is highly important in assessing the cost and effectiveness of such cleaning substances.
Scope
1.1 Direct titration of an anionic surfactant with a standardized cationic reagent is a simple and convenient method for the quantitative determination of the content of active ingredient. The end point is detffected by the transfer of a colored complex from an organic solvent phase to an aqueous phase. The relationship between anionic and cationic agents is not always stoichiometric, and for maximum accuracy the anionic type of interest should first be characterized and then used to standardize the cationic reagent. In most cases, however, the different anionic surfactants likely to be encountered react in the same proportions. That is, a cationic titrating solution standardized against a characterized anionic agent can be used to analyze other anionics of known molecular weights.
1.2 This test method is applicable to alkylaryl sulfonates and fatty alkyl sulfates. Low results are obtained with alkylbenzene sulfonates having the alkyl chain length less than eight carbon atoms. Low results are also obtained for alkyl sulfates with the alkyl chain length of less than twelve carbon atoms. The anionic surfactants characterized in accordance with Sections 17 – 23 should be the sodium salt and not amine, ammonium, or potassium salts. In case only amine or ammonium salts are available, they should be first converted to the sodium salt before proceeding with this analysis.
1.3 The analytical procedures appear in the following order:
Sections
Separation of Alcohol-Soluble Matter
8 and 9
Separation of Oil-Free Sulfonate
10 and 11
Determination of Sodium Chloride (NaCl) Content
12 – 17
Characterization of Anionic Surfactant Standard:
Part I. Determination of Surfactant, SO3 Content, and Solution
Molarity
18 – 20
Part II. Determination of Surfactant, SO3 and Active Ingredient
Contents Combining Weight, and Solution Molarity
21 – 24
Standardization of Cationic Reagent
25 – 29
Quantitative Determination of Anionic Surfactant by Cationic
Titration
30 – 33
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For a specific hazards statement, see Section 7.