McGettrick Julie R, Palmer Christopher P
Department of Chemistry and Biochemistry, University of Montana, Missoula, MT, USA.
J Sep Sci. 2017 Oct;40(20):4060-4066. doi: 10.1002/jssc.201700461. Epub 2017 Sep 11.
Capillary electrophoresis and electrokinetic chromatography are typically carried out in unmodified fused-silica capillaries under conditions that result in a strong negative zeta potential at the capillary wall and a robust cathodic electroosmotic flow. Modification of the capillary wall to reverse the zeta potential and mask silanol sites can improve separation performance by reducing or eliminating analyte adsorption, and is essential when conducting electrokinetic chromatography separations with cationic latex nanoparticle pseudo-stationary phases. Semipermanent modification of the capillary walls by coating with cationic polymers has proven to be facile and effective. In this study, poly([2-(acryloyloxy)ethyl]trimethylammonium chloride) polymers were synthesized by reversible addition-fragmentation chain transfer polymerization and used as physically adsorbed semipermanent coatings for capillary electrophoresis and electrokinetic chromatography separations. An initial synthesis of poly([2-(acryloyloxy)ethyl]trimethylammonium chloride) polymer coating produced strong and stable anodic electroosmotic flow of -5.7 to -5.4 × 10 cm /V⋅s over the pH range of 4-7. Significant differences in the magnitude of the electroosmotic flow and effectiveness were observed between synthetic batches, however. For electrokinetic chromatography separations, the best performing batches of poly([2-(acryloyloxy)ethyl]trimethylammonium chloride) polymer performed as well as the commercially available cationic polymer polyethyleneimine, whereas polydiallylammonium chloride and hexadimethrine bromide did not perform well.
毛细管电泳和电动色谱通常在未改性的熔融石英毛细管中进行，其条件会导致毛细管内壁产生强负zeta电位和强大的阴极电渗流。对毛细管内壁进行改性以反转zeta电位并掩盖硅醇位点，可以通过减少或消除分析物吸附来提高分离性能，并且在用阳离子乳胶纳米颗粒假固定相进行电动色谱分离时至关重要。通过用阳离子聚合物涂层对毛细管内壁进行半永久性改性已被证明是简便有效的。在本研究中，通过可逆加成-断裂链转移聚合合成了聚([2-(丙烯酰氧基)乙基]三甲基氯化铵)聚合物，并将其用作毛细管电泳和电动色谱分离的物理吸附半永久性涂层。聚([2-(丙烯酰氧基)乙基]三甲基氯化铵)聚合物涂层的初步合成在4-7的pH范围内产生了-5.7至-5.4×10 cm /V·s的强而稳定的阳极电渗流。然而，在不同合成批次之间观察到电渗流大小和有效性的显著差异。对于电动色谱分离，性能最佳的聚([2-(丙烯酰氧基)乙基]三甲基氯化铵)聚合物批次的表现与市售阳离子聚合物聚乙烯亚胺相当，而聚二烯丙基氯化铵和溴化己二甲铵的表现不佳。
