High efficiency and simple preparation of polyacrylamide coated silica stationary phase for hydrophilic interaction liquid chromatography.

A polyacrylamide (PAM)-coated silica packing as a novel stationary phase for hydrophilic interaction liquid chromatography (HILIC) was produced firstly by thermal immobilization. The coated layer was formed by a simple and facile physical method that dipping silica spheres into a PAM solution and then stirring the mixture until the solution was evaporated absolutely, leaving a certain amount of PAM on the silica particles. Although there are no chemical bonds involved, the bleeding measurement and the background noise are acceptable. Polyacrylamide coated silica (PAM-Sil, mean diameter: 5 μm) demonstrated a good hydrophilic property and excellent separation efficiency, which was observed especially for several high polar analytes such as saccharides. It is much higher than bare silica or amino columns under the same conditions. Moreover the obtained stationary phase demonstrated good stability under our operation conditions. The specific preparing method offers an easy and economical way to manipulate the thickness of PAM coating and can be extended as a universal way to produce various polymer coated stationary phases with dipping-heating/stirring-evaporating procedure.