V. V. Sursyakova

System peaks in capillary zone electrophoresis of anions with negative voltage polarity and counter‐electroosmotic flow

The system peaks that often appear on electropherograms in anion separation by CE with indirect spectrophotometric detection, negative voltage polarity and cathodic EOF are studied. The system peaks are shown to correspond to the zones with the changed concentration of the BGE constituents; they appear while the zone of each analyte anion passes through the outlet end of the capillary and are transported to the detector by EOF. An equation is suggested for predicting migration times of the system peaks with an error of 1%. The ratios of the system peak area to the analyte peak area are found to amount to 20%. It is shown that it is possible to avoid overlapping of the system peaks and analyte peaks by controlling the EOF velocity owing to hydrodynamic pressure. Using the mathematical simulation of CE shows that the system peaks and baseline shift can result from changing the transference numbers of the BGE ions and analyte ions at the capillary edge. The cases when the system peak may be incorrectly identified as the peak of analyte ion are considered. In order to avoid such errors, some practical recommendations are given.

Hydrodynamic suppression of the electroosmotic flow in capillary electrophoresis with indirect spectrophotometric detection

A version of capillary electrophoresis with indirect spectrophotometric detection and the hydrodynamic suppression of electroosmotic flow is studied. It is shown that, to improve the reliability of ion identification, one should calculate electrophoretic mobilities of ions or migration times corrected with regard to the electroosmotic flow rate. Correlations between electrophoretic peak areas of ions and their electrophoretic mobilities are derived. In the studied version of capillary electrophoresis, the accuracy of measuring anion concentrations can be improved using the internal standard method.

System peaks and optimization of anion separation in capillary electrophoresis with non-reversed electroosmotic flow

We studied system peaks present in the electropherograms obtained in the separation of anions by capillary electrophoresis with indirect spectrophotometric detection and cathode electroosmotic flow (EOF) with a chromate background electrolyte. The system peaks correspond to the zones with changed concentration of the background electrolyte; they formed when the zones of each analyte passed through the outlet of the capillary and then moved towards the EOF detector. It has been revealed that the height and area of the system peaks linearly depends on the concentration of the corresponding anion and the areas of the system peaks can achieve 10% of the anion peak area. An algorithm has been proposed for the determination of the optimal conditions for anion separation using hydrodynamic pressure for the regulation of the EOF flow rate. This algorithm prevents the overlapping of the anion and system peaks.

Determination of iron and copper ions in cognacs by capillary electrophoresis

A method is developed for the determination of iron(III) and copper(II) in cognacs by capillary electrophoresis (CE) with diode array detection with limits of detection 0.06 and 0.6 mg/L, respectively. Foreign substances present in cognac do not interfere with the determination. The accuracy of the results of analysis was confirmed by the added-found method. The method was applied to the analysis of seven cognac samples. The data obtained by CE are in a good agreement with the results of inductively coupled plasma mass spectrometry.

Determination of stability constants of inclusion complexes of betulin derivatives with β-cyclodextrin by capillary electrophoresis

67 Betulin and its derivatives relating to pentacyclic triterpenoids of lupan series exhibit pharmacological activity including human immunodeficiency virus inhibition, as well as antibacterial, antimalarial, anti inflammatory, antioxidant, and anticancer activity [1–3]. However, their medical application is rather limited because of their low solubility in water, which hampers the preparation of formulation for injection in humans.

Optimization of the conditions of phenol determination in natural and potable waters by HPLC with sorption preconcentration

The conditions of the sorption preconcentration of phenols from samples of natural and potable waters in Diapak P concentrator cartridges filled with super-cross-linked polystyrene are optimized. Countercurrent desorption with acetonitrile or methanol ensures the elimination the step of organic solvent evaporation. The observed reduction of the sorption of humic and fulvic acids (HFA) on the addition of sodium sulfite to the samples of natural and potable waters prior to their processing probably relates to the change of pH. The preconcentration of phenols from natural and potable waters at pH 6–8 substantially reduces the sorption of HFA. The method is used to determine phenols in samples of tap water and water from the Yenisei river by the added-found method.