Conductivity detection in capillary zone electrophoresis: Inspection by PeakMaster

Abstract

A simple rule stating that the signal in conductivity detection in capillary zone electrophoresis is proportional to the difference between the analyte mobility and mobility of the background electrolyte (BGE) co-ion is valid only for systems with fully ionized electrolytes. In zone electrophoresis systems with weak electrolytes both conductivity signal and electromigration dispersion of analyte peaks depend on the conductivity and pH effects. This allows optimization of the composition of BGEs to give a good conductivity signal of analytes while still keeping electromigration dispersion near zero, regardless of the injected amount of sample. The demands to achieve minimum electromigration dispersion and high sensitivity in conductivity detection can be accomplished at the same time. PeakMaster software is used for inspection of BGEs commonly used for separation of sugars (carbohydrates, saccharides) at highly alkaline pH. It is shown that the terms direct and indirect conductivity detection are misleading and should not be used.

A Comparison of the Properties of Contactless Conductivity and Diode‐Array Photometric Detectors in Analyses of Low‐Molecular, Biologically Active Substances by Capillary Electrophoresis in Acetic Acid Solutions

“…For the sake of comparison, the specific conductance dependence on the HAc concentration was also computed from the dissociation equilibrium using the Peak Master program [20,21]. It can be seen from Figure 1 than the computed ones, apparently owing to structural changes of the solution, primarily association of HAc molecules and formation of their dimers and clusters with molecules of water [22]; these effects are not considered by the PeakMaster program.…”

“…The difference from the experiment is due to the fact that the PeakMaster program computes the molar conductance response, b x , i.e., the difference in the conductances for the analyte zone and the BGE in dependence on the BGE composition (for analyte concentration equal to unity) [20] and disregards the changes in the HAc solution conductance with changing HAc concentration (Fig. 1) and the given arrangement of the C 4 D cell.…”

“…The response dependences computed by the PeakMaster program [20,21] predicts an unpronounced, monotonous decrease in the response over the whole interval of the HAc concentration. The difference from the experiment is due to the fact that the PeakMaster program computes the molar conductance response, b x , i.e., the difference in the conductances for the analyte zone and the BGE in dependence on the BGE composition (for analyte concentration equal to unity) [20] and disregards the changes in the HAc solution conductance with changing HAc concentration (Fig.…”

Evaluation of Peakmaster for computer‐aided multivariate optimisation of a CE separation of 17 antipsychotic drugs using minimal experimental data

“…Although the source of the analyte input information and the criteria for the identification of the optimal BGE were not specified by the authors, the method was applied to the intended samples successfully. Subsequently Jaroš et al [7] applied Peakmaster to examine BGE conditions with suitable conductivity detection while minimising electromigrational dispersion. Within this work, simulated and experimentally derived electropherograms of sugar analytes were compared, displaying near-identical migration of the anlaytes within both electropherograms, although a greater degree of electromigration dispersion was apparent in the experimentally derived electropherogram.…”

The Dependence of the Sensitivity and Reliability of Contactless Conductivity Detection on the Wall Thickness of Electrophoretic Fused‐Silica Capillaries

“…C 4 D is employed not only in analyses of inorganic ions for which it was originally introduced [5 -7], but also in determinations of many organic substances. Especially important are CE-C 4 D determinations of biogenic substances, such as carboxylic acids [8], amino acids [9,10], proteins [11] and saccharides [12,13] in real biological samples. The commonly attained limits of detection (LOD) are around 1 mM for most inorganic and organic analytes [6,14].…”