Predicting Peak Shape in Capillary Zone Electrophoresis:  a Generic Approach to Parametrizing Peaks Using the Haarhoff−Van der Linde (HVL) Function

Erny, Guillaume L.; Bergström, Edmund T.; Goodall, David M.; Grieb, Sally

doi:10.1021/ac010758g

Cited by 49 publications

(47 citation statements)

References 25 publications

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“…Analyte peaks were fitted with the Haarhoff-van der Linde function [63] (see also [64][65][66]) in order to get correct migration time for unsymmetrical peaks. Nonlinear curve fittings and all other plottings were performed with Origin 6.1 (OriginLab, Northampton, MA, USA).…”

Section: Methodsmentioning

confidence: 99%

Capillary electrophoresis in N,N‐dimethylformamide

Porras

Kenndler

2005

Electrophoresis

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N,N-Dimethylformamide (DMF) is a dipolar protophilic solvent with physicochemical properties that makes it suitable as solvent for capillary electrophoresis (CE). It is prerequisite for the proper application of CE to adjust and to change the pH of the background electrolyte (BGE) in a defined manner. This was done in the present work using benzoic acid-benzoate by selecting different concentration ratios of acid and salt, and calculating the theoretical pH from the activity-corrected Henderson-Hasselbalch equation. The mobilities of the analytes (chloro- and nitro-substituted phenolates) were found to follow reasonably well the typical sigmoid mobility versus pH curve as predicted by theory. The actual mobilities and pK(a) values (at 25 degrees C) of the analytes were derived from these curves. pK(a) values were in the range of 11.1-11.7, being thus 3-4.4 units higher than in water. This pK(a) shift is caused by the destabilization of the analyte anion and the better stability (solubility) of the molecular analyte acid in DMF, which overcome the higher basicity of DMF compared to water. Absolute mobilities were calculated from the actual mobilities; they were between 32x10(-9) and 42x10(-9) m(2)/Vxs. Slight deviations of the measured mobilities from the theoretical mobility versus pH curve were discussed on the bases of ion pairing and heteroconjugation and homoconjugation of either buffer components or buffer components and analytes. Heteroconjugation was used as a mechanism for the electrically driven separation of neutral analyte molecules in a BGE where salicylate acted as complex forming ion. Rough estimation of the complexation constants for the phenolic analytes gave values in the range of 100-200 L/mol. Addition of water to the solvent decreased the effect of heteroconjugation, but it was still present up to the surprisingly high concentration of 20% water. Electrophoretically relevant parameters like ionic mobilities and pK(a) values, and conjugation and ion pairing are dependent on the water content of the solvent. The water uptake of DMF was measured when exposed to humidity of ambient air. The resulted behavior of the water uptake was found rather similar to that for acetonitrile and methanol.

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Section: Methodsmentioning

confidence: 99%

Capillary electrophoresis in N,N‐dimethylformamide

Porras

Kenndler

2005

Electrophoresis

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“…Therefore, also prediction is hardly possible. However, there is no theoretical reason why this dispersion effect could not be depicted by appropriate mathematical means, as demonstrated by several authors [63,[76][77][78], given that the data for mobilities and pK a values were available. (iii) The plate height for thermal peak broadening, in contrast, includes parameters that depend on the solvent.…”

Section: Effect Of Solvents On Efficiencymentioning

confidence: 99%

The principles of migration and dispersion in capillary zone electrophoresis in nonaqueous solvents

2003

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Nonaqueous solvents are interesting media for capillary zone electrophoresis as they can affect all relevant parameters governing the separation of sample zones. However, for a rational planning of the working conditions and an appropriate interpretation of the results obtained, the basic principles of ion migration and zone dispersion must be understood. Many solvent induced effects need to be carefully considered and recognized before full exploitation of nonaqueous solvents can take place. It is the goal of this overview to present the fundamental physicochemical aspects of capillary zone electrophoresis in nonaqueous solvent systems. Therefore, the detailed discussion is related to the effect of organic solvents on electrophoretic mobilities (based on the theory of conductance), acid-base dissociation behavior (based on the transfer activity coefficient and medium effect), pH, separation efficiency (with regard to mobility and diffusion coefficient in dilute solutions), resolution, and electroosmotic flow.

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“…The flexibility of the model was evaluated on theoretical and experimental peaks with asymmetries in a wide range. The new model was compared with other three models that have shown good performance in the fitting of chromatographic and/or electrophoretic peaks: the empirically transformed Gaussian (ETG) [2], the parabolic Lorentzian-modified Gaussian (PLMG) [11], and the Haarhoff-van der Linde (HVL) function [9,12].…”

Section: General Aspectsmentioning

confidence: 99%

“…Among them, three models have shown the best performance [1]: the empirically transformed Gaussian (ETG) [2], the parabolic Lorentzian-modified Gaussian (PLMG) [11], and the Haarhoff-van der Linde (HVL) function [9,12], which are described below. A comparison with the proposed CSR model is further presented.…”

Section: Other Peak Modelsmentioning

confidence: 99%

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A new mathematical function for describing electrophoretic peaks

Garcı́a-Alvarez-Coque

Simó‐Alfonso

Sanchis-Mallols

et al. 2005

Electrophoresis

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A new model is proposed for characterizing skewed electrophoretic peaks, which is a combination of leading and trailing edge functions, empirically modified to get a rapid recovery of the baseline. The peak model is a sum of square roots and is called thereby "combined square roots (CSR) model". The flexibility of the model was checked on theoretical and experimental peaks with asymmetries in the range of 0-10 (expressed as the ratio of the distance between the center and the trailing edge, and the center and the leading edge of the chromatographic peak, measured at 10% of peak height). Excellent fits were found in all cases. The new model was compared with other three models that have shown good performance in modelling chromatographic peaks: the empirically transformed Gaussian, the parabolic Lorentzian-modified Gaussian, and the Haarhoff-van der Linde function. The latter model was proposed recently to describe electrophoretic peaks. The CSR model offered the highest flexibility to describe electrophoretic peak profiles, even those extremely asymmetrical with long tails. The new function has the advantage of using measurable parameters that allow the direct estimation of peak areas, which is useful for quantitative purposes.

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Predicting Peak Shape in Capillary Zone Electrophoresis: a Generic Approach to Parametrizing Peaks Using the Haarhoff−Van der Linde (HVL) Function

Cited by 49 publications

References 25 publications

Capillary electrophoresis in N,N‐dimethylformamide

Capillary electrophoresis in N,N‐dimethylformamide

The principles of migration and dispersion in capillary zone electrophoresis in nonaqueous solvents

A new mathematical function for describing electrophoretic peaks

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