Gels as size selective extraction solvents

We have successfully used cross‐linked, partially‐hydrolyzed, polyacrylamide gels to concentrate solutions of high molecular weight solutes. The gels are sizeselective, concentrating solutes whose diameter exceeds 3 nm. They can be easily regenerated by means of pH‐induced changes in gel swelling; this regeneration is consistent with that inferred from existing theories of gel swelling. The resulting separation process is a good alternative to ultrafiltration.