Abstract:

Silica is used as an important component for NMR "chromatog.". In this study the effect of the binding strength to silica of a variety of compds. on their diffusion rate is measured for the first time. Over two orders of magnitude of diffusion difference enhancement was obtained in the presence of silica for some compds. An explanation of the enhancement is given that also allows one to predict the "chromatog." behavior of new compds. or mixts. The binding strength is divided into categories of weakly bound, singly bound and multiply bound. Carboxylates, sulfonates, and diols are found to be particularly strongly bound and to diffuse up to 21/2 orders of magnitude more slowly in the presence of silica. [on SciFinder(R)]