In Parts I and II of this series (1,2), degradation and foaming experiments on a number of commercially available alcohol polyethoxylates and alkyl phenol polyethoxylates are described. This paper describes an extension of the thin layer chromatographic work on which the experiments described earlier were based, supplemented by a variety of other chemical and physical tests to provide some insight into the initial mechanism of degradation of these materials before they disappear by the established oxidation and hydrolytic routes. In the case of the readily degradable alcohol ethoxylates, two distinct mechanisms are shown to proceed simultaneously: a fission of the molecule into hydrophobic and hydrophilic entities, and a rapid oxidation of the hydrophobic group. No fission occurs in the case of the alkyl phenol ethoxylates, the more usual route of degradation being slow oxidation and hydrolysis of the alkyl groups, the aromatic ring and the ethoxy chain simultaneously; occasionally, and at higher pH, the hydrolysis of the ethoxy chain proceeds at a considerably increased rate.

The thin-layer chromatographic method for determination of nonionie detergents has been used for the chemical assessment of alcohol polyethoxylates and material derived from them during degradation under simple laboratory conditions. Foaming capacity during degradation was also measured on a representative selection of the materials under test.With one exception (a material with a highly branched alkyl chain) the disappearance of all the aleohoi-ethoxylates tested was rapid; a small increase in time required for complete disappearance was observed with the more highly ethoxylated materials, and with the materials which had some slight branching in the alkyl chain. Residues of the polyethylene glycol type, which were generally more persistent than the original materials, were observed to build up as the original materials disappeared, increasing ethoxylation present in the original material giving rise to increasing quantities of residues.The foaming capacity at every stage of the degradation, that is, foam formation alone or synergistic effect on foam formation because of other detergents, could be closely correlated with the results obtained by using the thin-layer chromatographic procedure.

In this series of experiments, as in those described in Part I, the foaming capacity during degradation could be closely correlated with the results obtained by using the thindayer chromatographic procedure.

A preliminary investigation showed that polyoxyethylene emulsifiers contain substantial amounts of "free" polyethylene glycol. An improved method for determining these emulsifiers in foods is presented, in which the emulsifier is extracted with chloroform, "cleaned up" on an alumina column and analysed by thin-layer chromatography with a modified Dragendorff reagent to spray the chromatogram. The method is a t least f 1 5 per cent. accurate down to an emulsifier level of 0.01 per cent. in fats and 0.001 per cent. in baked foods and food mixes. The detection of polyoxyethylene emulsifiers can be carried out a t even lower levels.

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