Imidazolium ionic liquids as dynamic and covalent modifiers of electrophoretic systems for determination of...

The subject of this study is comparison of imidazolium based dynamic and covalent coatings of the quartz capillary wall on the example of catecholamines determination. A way of synthesis of covalent coatings was proposed. For the first time different type of on-line sample preconcentration techniques (field-amplified sample stacking (FASS), head-column field amplified sample stacking (HC FASS), electrostacking, sweeping) were performed for catecholamines determination in N-alkylsubstituted imidazolium coated capillary. It was found that long chain imidazolium ionic liquids (C₁₂MImCl and C₁₆MImCl) in background electrolyte content create a dynamic coating of the quartz capillary walls and generate anode electroosmotic flow. Same is true for covalent coatings based on N-alkylsubstituted imidazolium. Both coatings prevent sorption of catecholamines on the internal surface of the quartz capillary. As a result efficiency and peak symmetry are increased. The maximum stacking efficiency factor (SEF) values for dynamic coatings were in range of 70-85, and limits of detection (LODs) were about 0.05 µg/ml under sweeping condition (micelle forming agent - C₁₆MImCl) when the electric conductivity of sample matrix was higher than electric conductivity of BGE. In case of covalent coating, the maximum SEF values were higher than 1000, and LODs were about 1-2 ng/ml under sweeping condition (micelle forming agent - sodium dodecyl sulphate) in combination with electrostacking.