Determination of polyoxyethylene p-t-nonylphenyl ethers in pomades

Abstract

A method is proposed for the determination of polyoxyethylene p-t-nonylphenyl ethers, RO(CH₂CH₂O)_nH (R =p-t-nonylphenyl), in pomades. The method is based on the evaluation of the number average degree of polymerisation of the polydispersity (n) by vapour pressure osmometry and by thin-layer chromatography, and on the spectrophotometric determination of the apparent mean molar absorption coefficient (ε) at 620 nm of the bisammonium tetrathioisocyanatocobaltate(II) complexes extracted into 1,2-dichloroethane.

The method has been tested for values of n in the range 6·5 to 21·5 and for Weibull distributed polydispersions. Significant systematic errors arise only in mixtures of polydispersions with very different values of n. The accuracy and intralaboratory reproducibility have been evaluated by analysing samples of a pomade of known composition.