The identification of polyethylene glycols and polypropylene glycols by thin-layer chromatography

Abstract

Thin-layer chromatographic procedures involving the use of silica-gel plates have been developed for the identification of polyethylene and polypropylene glycols.

One method is described for distinguishing between polyethylene glycols and polypropylene glycols; a mixture of chloroform and industrial methylated spirits is used as the developing solvent and the separated zones are located by spraying with an acidic solution of potassium permanganate.

A second method is described for determining the approximate molecular weight distribution of the polyglycols. The polyglycols are converted into the 3,5-dinitrobenzoyl esters, which are then examined by thin-layer chromatography; the polyethylene glycol esters are separated by using ethyl methyl ketone, saturated with water, as developing solvent, and polypropylene glycol esters are separated by using a mixture of ethyl acetate and acetic acid. An ethanolic solution of rhodamine B is used as the reagent to locate the separated zones. Simple glycols do not interfere in the identification of the polyglycols.