Victor P. Andreev

Computer simulation of electroinjection analysis and electrophoretically mediated microanalysis: Commensurable concentrations of sample and reagent

Abstract The mathematical model of electroinjection analysis and electrophoretically mediated microanalysis is presented. The evolution of sample, reagent and product concentrations is described by the set of three diffusion–convection equations that are solved with the help of computer simulation. The influence of commensurable initial concentrations of sample and reagent and of reverse reaction are studied.

Hydrodynamics and mass transfer of the coaxial jet mixer in flow injection analysis.

A coaxial jet mixer that was previously proposed for rapid and efficient mixing under laminar flow conditions has been studied both theoretically and experimentally. A mathematical model that consists of a set of Navie-Stokes equations that determine the flow velocities and three diffusion-convection reaction equations that determine the reactant and product concentrations has been developed. Equations are solved with the help of finite difference techniques for different flow conditions. The quality of sample and reagent mixing is characterized by the mean product concentration and the amount of product produced. Theoretical results are compared with experimental ones for the mixing of bromothymol blue (a pH indicator) in the outer capillary with NaOH in the inner capillary of the jet mixer.

Electroinjection analysis concept, mathematical model and applications

Electroinjection analysis is described and compared with electrophoretically mediated microanalysis and flow injection analysis. Mathematical models of electroinjection analysis and electrophoretically mediated microanalysis are presented. An analytical solution for the concentration of the product of a chemical reaction is derived and used for the discussion of the optimal regimes of analysis. Examples of the applications of electroinjection analysis and electrophoretically mediated microanalysis for the determination of Cr(VI) and Co(II) ions in water are presented.

Computer simulation of affinity capillary electrophoresis.

A computer‐simulated model of affinity capillary electrophoresis is developed. Unlike existing models, it is able to describe the situation where the concentrations of sample molecules and ligand molecules are commensurable, or even the situation where the zones occupied by these molecules are not mixed initially. The model permits to study the dependence of the spatial and temporal distributions of sample molecules on various parameters such as reaction rate constants, concentrations of sample and reagent, electromigration velocities of sample and reagent and sample injection volume. A collection of peak shapes for different values of parameters is presented. The dependence of peak variance on the ratio of the time of analysis to the characteristic time of reaction is studied.

Experimental study of kinematic focusing. Comparison of electroinjection and sequential injection determination of copper.

The recently predicted phenomenon of kinematic focusing was studied experimentally using copper ions and EDTA as reactants. Kinematic focusing occurs, in electroinjection analysis, when the detected reaction product moves at the same rate as the reagent present in excess. Thus, reaction product accumulates without dispersion at the front of the excess reagent. Cu-EDTA(2-) complex was observed at 254 nm to form an exceptionally sharp peak as the front of the EDTA zone passed by the detector. The concentrating effect of kinematic focusing was quantified by electroinjection of premixed Cu-EDTA(2-). Sensitivity was compared to that of sequential injection analysis using a 1 cm optical pathlength. Sensitivity was highest in the electroinjection mode, in spite of its 120 mum capillary pathlength, due to kinematic focusing.

PRINCIPLES AND CAPABILITIES OF ELECTROINJECTION ANALYSIS

Electroinjection analysis, its principles, and its applications are reviewed. The signal-enhancing effect of kinematic focusing is explained, and new results to demonstrate the effect are presented. The potential of electroinjection analysis for investigation of the complex-forming ability of natural samples is illustrated by the reaction of copper and lead with peat samples; the fraction of uncomplexed metal is reacted in the column with EDTA for detection. Reaction kinetic studies with EIA are presented, along with the novel ability to detect reaction intermediates. Electroinjection analysis is compared with flow injection analysis, capillary electrophoresis with precolumn reaction, electrophoretically mediated microanalysis, and affinity capillary electrophoresis. *Presented at Warsaw Technical University Chemical Forum, May 15, 2001.