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.