Stability and effectiveness of linear polyacrylamide capillary coating to suppress EOF in acidic media in the presence of surfactants, ionic liquids and organic modifiers

Because of its high hydrophilicity, linear polyacrylamide (LPA) has often been used as a coating to suppress electroosmotic flow (EOF) in capillary electrophoresis (CE); however, its stability and effectiveness in acidic media, with or without organic modifiers, surfactants or ionic liquids is not well documented. In this work, the adequacy of LPA coating to suppress EOF in those different conditions was studied. It was shown that electroosmotic mobilities (mu(EO)) did not change for at least 70 h of non-stopped operation in all the tested conditions and the coating was stable. It was also shown that LPA coating efficiently suppresses EOF in acidic media (pH 4.0, 3.1, and 23) with or without organic modifiers (50% methanol or acetonitrile, ACN), as measured mu(EO) values were between 18 and 84 times lower than those obtained with bare fused-silica capillaries. In acidic media with anionic surfactant (50 mM sodium dodecylsulfate, SDS), ionic liquid (25 mM dodecyldimethylimidazolium bromide) or both SDS and ACN (buffer pH 2.1/ACN (8:2, v/v)+50 mM SDS) EOF was reduced to a magnitude lower than with bare fused silica capillaries, even though slight adsorptions of these surfactants were observed. LPA showed its superiority to hydroxypropyl cellulose, for which marked adsorption occurred because of its lower hydrophilicity. (C) 2016 Elsevier B.V. All rights reserved.