On-line concentration of biogenic amines by capillary electrophoresis method using the synthesized covalent coating based on the imidazolium ionic liquids

Abstract

Covalent coatings of internal quartz capillary walls based on the ionic liquids were synthesized within this research. The synthesis of the covalent coating included a step of silylation followed by the functionalization with imidazole and 1-bromobutane. The resulting coating created anodic electroosmotic flow (EOF) at pH = 2. The range of pH at which coatings do not change their properties was 2.0-5.5. The possibilities of different ways of on-line concentration (large volume sample stacking, head-column field-amplified sample stacking, sweeping, sweeping in combination with electrostacking) of catecholamines were examined. Stacking efficiency factors (SEF) were 105-135 and the detection limits were decreased to 11-17 ng/ml for analytes under the large volume sample stacking. Under the sweeping conditions, sodium dodecyl sulfate (micelle forming agent) was sorbed on the modified walls, provided a negative charging surface and acted as a strong cation exchanger. This fact led to the additional reserves in the separation selectivity of catecholamines. Under the electrostacking, the values of SEF were above 1000 and the detection limits were reduced to 1-2 ng/ml. An approbation of established patterns in the analysis of urine samples was carried out.