CONTENTS & ABSTRACTS
In English. Summaries in Estonian
Proceedings of the Estonian Academy of Sciences.
Volume 53 No. 1 March 2004
Special issue on capillary electrophoresis
Capillary electrophoresis in contemporary analytical chemistry; 3–5
Flow sampling in capillary electrophoresis with a pneumatically driven computerized sampler; 6–20
Arkadi Ebber, Sille Ehala, Marina Kudrjashova, Maria Kulp, Merike Vaher, and Mihkel Kaljurand
Abstract. Developments in sample introduction from liquid flow in capillary electrophoresis are reviewed. We have focused on the description of a pneumatically driven sampler that enables to force the sample stream to pass the inlet of the separation capillary. The advantages of such an input device are absence of a voltage rise and/or drop time during sampling, ease of operation because no vial manipulations are involved, and simple automation and computerization. However, the main advantage of such input devices seems to be that they facilitate easy, multiple inputs from a single sample vial. This opens the possibility of monitoring the concentration changes taking place inside the vessel, which is an important task in analytical biotechnology. This article describes some possible applications of such samplers in coupling capillary electrophoresis with flow injection analysis and high performance liquid chromatography in multiple input experiments (with or without stacking) for the reduction of detection limits and for monitoring reaction kinetics.
Key words: capillary electrophoresis, sample introduction, computerization, bioprocess monitoring, detection limits.
Separation of polyphenols and L-ascorbic acid and investigation of their antioxidant activity by capillary electrophoresis; 21–35
Sille Ehala, Merike Vaher, and Mihkel Kaljurand
Abstract. Growing evidence of the role of free radicals and antioxidants in health and ageing has focused great interest on these compounds. Vitamins C and E and various carotenoids are known to act as strong antioxidants. In recent years however interest in various polyphenols as antioxidants has also increased. Capillary electrophoresis, an effective analytical method, was used to separate the standard mixture of polyphenols and to determine the polyphenolic content of black currant qualitatively. In addition the oxidation of polyphenols and L-ascorbic acid with hydrogen peroxide (H2O2) was investigated. The experiment was performed with an in-house built reactor coupled to a capillary electrophoresis system.
Key words: capillary electrophoresis, polyphenols, antioxidative activity, free radical scavenging assay.
Electrophoretic mobilities in nonaqueos capillary electrophoresis; 36–45
Merike Vaher and Mihkel Koel
Abstract. In nonaqueous capillary zone electrophoresis separation is based on the interactions between the analytes and the ionic additive present in the separation medium. The choice of the solvents and solvent mixtures can influence the acid–base behaviour and solvation of the analytes and the additives; in addition, it can influence the electroosmotic flow of the separation medium and the intrinsic mobility of the analytes. Large changes in the separation factor and/or resolution, analysis time, and selectivity can be achieved by varying the type and content of the organic solvent in the medium. A simple and reproducible method in the case of which 1-alkyl-3-methylimidazolium based organic salts are used as additives in the separation medium is suggested. Complexes are formed with the anionic part of the ionic liquid additive. This is the case with Br¸nsted acids and phenolic compounds.
Key words: nonaqueous electrophoresis, ionic liquids, 1-alkyl-3-methylimidazolium salts.
Instructions to authors; 46–48