Polycations on derivatized glass or silica

1 Polycations on Derivatized Glass or Silica Since most aqueous packings contain functional groups that can dissociate to form anions, one may expect cationic polymers to be retained or adsorbed. There have been two approaches to this problem (1) preparation of cationic supports which repel the polycation, or (2) utilization of near-neutral supports. The pros and cons of both techniques will be discussed. 

Butler reported the chromatography of cationic polymers on aminated and quaternized polystryrene-divinylbenzene packings (52). This approach has apparently since been abandoned, possibly because of difficulty in controlling swelling and porosity. Talley and Bowman prepared a cationic CPG by deriva- 

Closer to the Talley-Bowman approach is the preparation of OMAE-FractosilTM (E. Merck, Darmstadt), schematically represented as  

Another commercially derivatized cationic porous glass is produced by Rhone-Poulenc under the trade name SpherosilTM qma. Domard and Rinaudo (56) employed this packing with 0.05 M - 0.2 M ammonium acetate to chromatograph dextran, poly(N-vinylpyrrol idone), PEG, poly(L-lysine), and chitosan. Plate counts were not reported, but typical assay times were apparently 7-9 hrs. While the cationic polymers do not appear to be highly adsorbed, universal calibration plots in 0.2 M ammonium acetate suggest that poly(N-vinylpyrroli-done) is adsorbed. The elution volume of PEG also seems to be sensitive to eluant ionic strength. 

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