DETERMINATION OF HYDROXYL-GROUPS IN POLY(ETHYLENE GLYCOLS)

An analytical method for the determination of hydroxyl content in poly (ethylene glycol) is presented and verified. It consists of substituting the hydroxyl group with a chromophoric siloxy group, purification of the silylated polymer, and a photometric determination of the chromophor concentration. The silan-ization of the primary hydroxyls with dimethylaminosilanes is shown to proceed quantitatively under very mild conditions and that the elimination of the excess reagent by precipitation is easy. The precision of the method is ±4.5% (95% confidence level) down to 5 X 10-4 mol kg-1 and it is estimated to be applicable to a lower limit of 10-4 mol kg-1. The method has about the same precision as the current standard acylation method but yields a 1000-fold gain in sensitivity. © 1979, American Chemical Society. All rights reserved.