Preparation and stability tests for polyacrylamide-coated capillaries for capillary electrophoresis

The stability of polyacrylamide coatings at high pH values has been tested. It could be shown that overall stability is not limited by the coating of the fused-silica surface with organo silanes or Grignard reagents. The instability of polyacrylamide capillaries could be traced back to the hydrolysis of the amide bond at pH 10. The SiOSi surface bonds are not affected at this pH by hydrolysis. The application of the sol-gel process to the preparation of stable homogeneous sublayers and a high density of olefinic groups within the capillary is described. The advantage for this method is the simple coating reaction and its independence of fused-silica surface properties.