title: Decreased protein peak asymmetry and width due to static capillary coating with hydrophilic derivatives of polydimethylacrylamide.
abstract: We have recently described [1] a fast and simple method for the "adsorbed static" coating of capillaries in capillary zone electrophoresis (CZE) with epoxy-poly(dimethylacrylamide) (EPDMA). Protein CZE peaks in the EPDMA-coated capillaries exhibited a peak asymmetry similar to that obtained in capillaries with "covalent static" coating of polyacrylamide, suggesting a similar degree of adsorption of the protein onto the coating [2]. Instability of such coating at very low ionic strength and its stripping from the capillary in the presence of sodium dodecyl sulfate (SDS) also indicated a hydrophilic bonding of EPDMA to the silanol surface of the capillary, while its stripping in the CZE of "carboxylate-modified" polystyrene suggested a competition between carboxylate and EPDMA for the hydrophilic bonds to silanol. To test those propositions, a number of EPDMA-derived coating agents with increased hydrophilicity were synthesized. Of a number of the hydrophilic coating agents tested (Table 1) only two, 2% hydrolyzed EPDMA (HPDMA) hydrolyzed in sulfuric acid to effect the conversion of the epoxy groups to diols (Table 1, No. 38), and 20% EPDMA (Table 1, No. 44) exhibited for representative proteins a decreased peak asymmetry and width while the stability of the suppression of electroosmotic flow (EOF), and the stability of mobility in consecutive CZE runs was reduced relative to EPDMA. Coating agents which were more highly hydrophilic than those two (Table 1, No. 49) or less hydrophilic than 2% EPDMA (Table 1, Nos. 57, 53, 46) provided no stable static coating.
authors.affiliation: Institute of Molecular Recognition Chemistry, CNR, Milano, Italy.
authors.forename: Marina
authors.initials: M
authors.lastname: Cretich
authors.forename: Miroslava
authors.initials: M
authors.lastname: Stastna
authors.forename: Andreas
authors.initials: A
authors.lastname: Chrambach
authors.forename: Marcella
authors.initials: M
authors.lastname: Chiari
mesh_terms: D000178:Acrylamides / Q000737:chemistry*; D000180:Acrylic Resins / Q000737:chemistry; D000327:Adsorption; D020099:Coated Materials, Biocompatible; D019075:Electrophoresis, Capillary / Q000295:instrumentation* / Q000592:standards; D004852:Epoxy Compounds / Q000737:chemistry; D004867:Equipment Design; D019544:Equipment Failure Analysis; D011506:Proteins / Q000032:analysis* / Q000378:metabolism; D055672:Static Electricity; D013499:Surface Properties
chemical_list: D000178:Acrylamides; D000180:Acrylic Resins; D020099:Coated Materials, Biocompatible; D004852:Epoxy Compounds; D011506:Proteins; C429790:poly(N,N-dimethylacrylamide); C413461:poly(dimethylacrylamide-co-allyl glycidyl ether)