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 (text-decoration:overlinen) by vapour pressure osmometry and by thin-layer chromatography, and on the spectrophotometric determination of the apparent mean molar absorption coefficient (text-decoration:overlineε) at 620 nm of the bisammonium tetrathioisocyanatocobaltate(II) complexes extracted into 1,2-dichloroethane.The method has been tested for values of text-decoration:overlinen 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 text-decoration:overlinen. The accuracy and intralaboratory reproducibility have been evaluated by analysing samples of a pomade of known composition.