O. N. Obrezkov

Modified silica as a stationary phase for ion chromatography

The possibility of the rapid preparation of agglomerated anion exchangers was demonstrated on a reversed-phase silica support with the polymeric agents poly(N-ethyl-4-vinylpyridinium bromide), poly(dimethyldiallylammonium chloride), poly(hexamethyleneguanidinium hydrochloride) and 2,5-ionene as modifiers. A 90-min sorbent preparation and column packing allowed an efficiency of more than 10000 theoretical plates per metre to be obtained for 10-μm spherical beads. The polymeric agents showed different selectivity, stability and capacity for the resulting anion exchangers (owing to changes in the structure and the density of functional groups in the polymer chain). The sorbents were used for the simultaneous determination of weakly and strongly retained anions and some heavy metals with EDTA solutions as eluent.

Ion chromatographic behaviour of anionic EDTA complexes of vanadiurn(IV) and vanadium(V)

The possibility of the simultaneous ion chromatographic determination of vanadium(IV) and vanadium(V) in the form of the EDTA complex and the EDTA monoperoxo complex, respectively, was shown. These complexes were retained strongly on the sorbent HIKS-1. The chromatographic characteristics of the EDTA complex of vanadium(V) were changed under the conditions of the experiment. The composition and the charge of the EDTA complex of vanadium(IV) and the EDTA monoperoxo complex of vanadium(V) and detection limits of vanadium(IV) and vanadium(V), were determined to be 0.2 and 1.0 mg 1−1, respectively. The kinetics of the formation of the EDTA monoperoxo complex of vanadium(V) in the system V(IV)-EDTA-H2O2 are discussed.

Simplex-optimization with a new criterion. Applications to dual-column ion chromatography

A new optimization criterion for chromatography is presented. It was designed to evaluate the quality of chromatograms in a way similar to human estimation. Selectivity, efficiency, and time of analysis as well as the number of peaks were taken into account. The criterion has been tested in comparison with expert estimations and some modern criteria. A better agreement of the new criterion with human estimation of chromatographic quality compared to some literature criteria is shown. A number of successful optimization runs has been performed using the criterion together with simplex optimization.

Application of the pattern-recognition method for modelling expert estimation of chromatogram quality

A method of nonparametric regression, namely the method of k-nearest neighbours, was applied in chromatography for creating an estimation criterion of chromatogram quality. A training set was constructed using expert estimation of a number of model and real chromatograms, and the method was learned to estimate chromatograms as a single image. The parameters for chromatogram estimation were selected, and their variance weights were determined. The proposed approach is compared with the existing criteria, and its advantages are shown. The method was successfully applied for searching for the optimum conditions for the ion-chromatographic determination of inorganic anions.

Ion chromatographic determination of anions, especially sulphur-containing anions, with conductimetric and kinetic detection

Abstract A new mode of detection in ion chromatography called “kinetic detection” is suggested. The technique uses an ion chromatograph with a conductimetric detector and a multichannel flow mounting with a spectrophotometric detector. The potassium bromate degradation reaction in hydrochloric acid accelerated by reducing anions, is used as a model indicator system. The sensitive determination of S2−, SO32−, S2O32−, SCN− and NO2− has been performed. The simultaneous deterimination of weak and strong inorganic acid anions is shown to be possible.

“Chromatogram generator” chromatogram modelling software

Abstract Software called “Chromatogram Generator” was developed for IBM-compatible computers. This software allows the approximation of chromatographic peaks with several mathematical functions and their superposition, the construction of series of chromatograms with various parameters (or with smooth variations of single or several parameters), the construction of the graphical image of a chromatogram with minimum size and the ability to be added to a chromatographic database.