Alkyl sulfates assay

Active agent content of anionics is usually determined by titration with a cationic surfactant such as benzethonium chloride. Two-phase titration is suitable for assay of alkylaryl sulfonates alkyl sulfates and hydroxysulfates, alkanesulfonates, fatty alcohol ethoxysul-fates and alkyIphenolethoxysulfates and dialkyIsulfosuccinates (4,5). The results on ma-... 

There are separate ISO standards for primary and secondary alkyl sulfates (i.e., for products made from primary or secondary alcohols). The ISO standard covering primary alkyl sulfates specifies neutral oil by extraction from ethanol/water solution, total combined alcohols by ether extraction after acid hydrolysis, pH of a 10% aqueous solution, water by titration if below 10% or by azeotropic distillation if above 5%, and chloride by titration (60). The standard covering secondary alkyl sulfates is similar, but combined alcohols are not determined. Assay is by determination of total solids after extraction of the neutral oil, corrected for the presence of other impurities (61). 

The procedure is suitable for determination of anionic surfactants in concentrates and in detergent formulations and is used for assay of alkyl aryl sulfonates, alkyl sulfates, sulfated APE and AE, and sulfosuccinates. As described in Chapter 1, alkane monosulfonates require special precautions. Phosphate surfactants will generally not be determined. Since the analysis is conducted at pH 2, soap is not determined. Hydrotropes in low concentrations do not interfere, nor do most other detergent constituents. 

Only the apphcation of LC-MS analysis can be conceived of as reliable surfactant analysis. To elaborate determination methods for the analysis of the anionic surfactant mixture of alkyl ethoxysuUates (AES) APCI and ESI-MS(-t/-) studies combined with in-source MS/MS examinations were performed and results were compared (cf. Pig. 15.4 and 15.5 and 15.3.3.2 ESI, surfactants). APCI fragment ion spectra revealed the aUcyl chain length and the number of ethoxylate moieties therefore APCI was found to be the method of choice [326]. To confirm determination methods apphed in surfactant analyses an inter-laboratory comparison study of LC-MS techniques and enzyme-hnked immunosorbent assay for the determination of surfactants in wastewaters was performed in seven laboratories. The quantitative determination of the non-ionic NPEOs, AEOs, coconut diethanol amides (CDEAs) and the anionic LAS, NPEO-sulfates and the secondary alkane sulfonates (SAS) was performed under APCI or ESI-interfacing conditions in positive or negative... 

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