Separation and concentration of biologically active compounds by capillary electrophoresis using modifiers based on imidazolium cation

A cationic covalent coating of quartz capillary walls based on imidazolium cation was synthesised; the reproducibility by electroosmotic flow (marker dimethylformamide) was 99 %. The conditions (concentration and pH of background electrolyte, nature and volume of organic additive) for their separation by capillary electrophoresis were optimised on model systems of phenyl- and indolecarboxylic acids (phenyl lactic, phenylanthanoic, phenyl butanoic, indole lactic, indolpropionic, indolacrylic hydroxymindal, homogentisic, homovanilinic, hydroxindoleacetic acids): 10 mM phosphate buffer solution with pH 4.2 with addition of 10 vol. % acetonitrile. The resolution factors of neighbouring pairs of analytes ranged from 1.7 to 18.9. The possibility of intracapillary concentration of phenyl- and indolecarboxylic acids using the synthesised coating was shown. Electrostacking allowed to concentrate the analytes 106–512 times and to lower the detection limits to 4–72 ng/ml.