Polyacrylamide adhesive for fixing the sorbent layers of overpressured, one-and multilayer-chromatographic plates and a process for the preparation thereof

A process for preparing a polyacrylamide adhesive having a density of 1.004 to 1.008 g/ml of and a relative viscosity of 2.ltoreq..eta..ltoreq.20, suitable for the appropriate fixing of fine particle sorbent layers, based on organic or inorganic compounds, and supplied with a bound or unbound nonpolar phase, used in high pressure single layer and multilayer chromatographic procedures, which comprises the following steps:

• (a) polymerizing in an aqueous mixture, acrylamide and N,N-methylene-bis-acrylamide, in the presence of a catalyst, at 21.degree. to 30.degree. C., wherein the aqueous mixture contains 1.6 to 2.5% acrylamide and 0.6 to 1.0% N,N-methylene-bis-acrylamide repsectively to obtain a polyacrylamide gel;
• (b) homogenizing the polyacrylamide gel to obtain an opaline solution containing acrylamide-N,N-methylene-bis-acrylamide copolymer;
• (c) fractionally precipitating the acrylamide-N,N-methylene-bis-acrylamide copolymer from the opaline solution with a water-soluble solvent to obtain a curdy precipitate containing the desired fraction of the copolymer and a supernatant liquid containing undesired monomers and oligomers;
• (d) removing the curdy precipitate and pulpifying same by adding water to form again a homogeneous opaline solution;
• and
• (e) repeating steps (c) and (d) several times to obtain a homogenous opaline composition of the polyacrylamide adhesive.