Quality criterion to optimize separations in capillary electrophoresis: Application to the analysis of harmala alkaloids

Abstract

In capillary electrophoresis (CE), resolution (Rs) and selectivity (α) are criteria often used in practice to optimize separations. Nevertheless, when these and other proposed parameters are considered as an elementary criterion for optimization by mathematical maximization, certain issues and inconsistencies appear. In the present work we analyzed the pros and cons of using these parameters as elementary criteria for mathematical optimization of capillary electrophoretic separations. We characterized the requirements of an ideal criterion to qualify separations within the framework of mathematical optimizations and, accordingly, propose: -1- a new elementary criterion (t') and -2- a method to extend this elementary criterion to compose a global function that simultaneously qualifies many different aspects, also called multicriteria optimization function (MCOF). In order to demonstrate this new concept, we employed a group of six alkaloids with closely related structures (harmine, harmaline, harmol, harmalol, harmane and norharmane). On the basis of this system, we present a critical comparison between the new optimization criterion t' and the former elementary criteria. Finally, aimed at validating the proposed methods, we composed an MCOF in which the capillary-electrophoretic separation of the six model compounds is mathematically optimized as a function of pH as the unique variable. Experimental results subsequently confirmed the accuracy of the model.

Determination of acidity constants and prediction of electrophoretic separation of amyloid beta peptides

“…In terms of selecting the optimum pH for the separation, this approach dramatically cuts down total optimisation time. Similar conclusions were drawn with an alternative quality criterion to optimise separations that Tascon et al recently described [36], adapting t' to use / 1/2 and considering the influence of the EOF.…”

“…Where N is the number of theoretical plates, mi is the me of the peptides, mavg is the average of mi values and mEOF is the EOF mobility. Resolution has been widely studied to optimise separations as a function of pH in CE with fused silica and coated capillaries [32,36]. If we suppose similar N values for all the peptides of the mixture, efficiency is considered as constant and only accounts for resolution the selectivity term.…”

Enantiomeric separations by capillary electrophoresis: Theoretical method to determine optimum chiral selector concentration

“…Therefore, it makes possible to predict by extension the behavior of more than one compound and, consequently, the optimization of their separation. Recently, a criterion to qualify the separation of many compounds in electrodriven separations with a single scalar was proposed [16]. The criterion, whose elementary form was called t'ij, considers the separation of compounds between them and also the separation of each one from neutral compounds, always present in real samples.…”

Capillary electrophoresis in phytochemical analysis (2014–2017)

“…But certain issues and inconsistencies appeared, when these and some other proposed parameters were considered as an elementary criterion for optimization by mathematical maximization. Tascon et al analyzed the pros and cons of using these parameters as elementary criteria for mathematical optimization of CE separations . They characterized the requirements of an ideal criterion to qualify separations within the framework of mathematical optimizations.…”