Gas chromatographic analysis of ester-type surfactants by using mixed anhydride reagent

Polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl ether phosphates, and polyoxyethylene fatty acid ester-type surfactants have been analyzed by gas chromatography after chemical decomposition by using the mixed anhydride of acetic and p-toluene-sulfonic acids. In this way, the hydrophobic groups of the polyoxyethylene alkyl ether sulfates and polyoxyethylene alkyl ether phosphates can be identified in the form of alkyl acetates, and the alkyl compositions can be determined easily. On the other hand, the hydrophobic groups of the polyoxyethylene fatty acid ester-type surfactants, such as polyoxyethylene fatty acid ester, polyoxyethylene glycerol fatty acid ester, and polyoxyethylene sorbitan fatty acid ester, have been identified after conversion into their corresponding fatty acids. At the same time, the base compounds of the hydrophilic groups have been converted into ethylene glycol diacetate, glycerol triacetate, and isosorbide diacetate, respectively, so these surfactants may be distinguished easily.