Poly(N,N‐dimethylacrylamide‐co‐4‐(ethyl)‐morpholine methacrylamide) copolymer as coating for CE

In this work, a new physically adsorbed coating for CE is presented. This coating is based on a poly(N,N‐dimethylacrylamide‐co‐4‐(ethyl)‐morpholine methacrylamide) (DMA/MAEM) copolymer synthesized in our laboratory. It is demonstrated that the direction and magnitude of the EOF in CE can be modulated by varying the composition of the DMA/MAEM copolymer and the type and pH of the BGE. Moreover, the DMA/MAEM coating provides %RSD_n = 5 values for migration times lower than 0.9% for the same capillary and day, whereas the %RSD_n = 25 obtained for the interday assay was lower than 2.9%. The stability of the coating procedure is also tested between capillaries obtaining %RSD_n = 15 values lower than 2.9%, demonstrating that this physically adsorbed copolymer gives rise to a stable and reproducible coating in CE. Finally, the usefulness of this new cationic copolymer as CE coating is demonstrated through different applications. Namely, it is demonstrated that the CE separation of basic proteins, nucleotides and organic acids is achieved in a fast and easy way by using the DMA/MAEM coated capillary. The use of fused bare silica capillaries did not allow the separation of these compounds under the same analytical conditions. These results demonstrate that this type of coating in CE provides the option of using BGEs that are useless when utilized together with bare silica capillaries making wider the application and possibilities of this analytical technique.