Characteristics of the electroosmotic flow of electrolyte systems for nonaqueous capillary electrophoresis

Abstract

Nonaqueous capillary electrophoresis (NACE) is a powerful tool for the analysis of surface-active substances, which represent a broad class of analytes containing cationic and anionic species, such as surfactants, phosphoric acid esters, and amines. In order to conduct an efficient method development in NACE, the influence of the electrolyte composition on the electroosmotic flow (EOF) of organic separation systems was systematically investigated. Background electrolytes and background chromophores appropriate for direct and indirect UV-detection were considered, as the majority of surface-active substances do not absorb UV-light. It was found that theoretical models developed to describe the EOF in aqueous electrolyte systems are insufficient for organic electrolyte systems. Experimental data on electroosmosis in a variety of organic solvents and mixtures of methanol and acetonitrile applying different background chromophores and basic or acidic additives are given. Differences between them are discussed with relation to the physicochemical properties of the organic solvents.

Recent advances in nonaqueous capillary electrophoresis

“…Studies on the influence of the electrolyte system on the EOF of organic separation systems have been few [30,31], but, happily, systematic investigation on the topic was just recently published by Grob and Steiner [32]. Experimental data were given on electroosmosis in common NACE solvents (MeOH, ACN, N-methylformamide (NMF), N,N-dimethylform- Vaher et al [33,34] used dialkylimidazolium-based lowtemperature-melting organic salts known as "ionic liquids" as electrolyte additives in ACN.…”

“…EOF-marker, antracene; Applied voltage, 30 kV; capillary, 48.5 cm6 75 mm; injection, 1 s at 50 mbar from 1 mM solution, UV detection at 340 nm[32].…”

Microchip electrophoretic separation and fluorescence detection of chelerythrine and sanguinarine in medicinal plants

“…The electrophoretic mobility (m ep ) depends on the solute charge (q), radius (r), and solvent viscosity (η) as follows [38]:…”

Validation of non-aqueous capillary electrophoresis for simultaneous determination of four tricyclic antidepressants in pharmaceutical formulations and plasma samples

“…It is well known that an increase in ionic strength causes a reduction of the thickness of the electric double layer. Consequently, the zeta potential decreases resulting in electroomosis suppression [28].…”