Migration behaviour of monovalent weak acids in micellar electrokinetic chromatography mobility model versus retention model

Muijselaar, Pim G.; Claessens, H.A.; Cramers, C.A.M.G.

doi:10.1016/s0021-9673(96)00920-x

Cited by 32 publications

(17 citation statements)

References 23 publications

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“…For weak electrolytes (acids, bases, amphoteric compounds) the overall retention factor is the weighted sum of the retention factors of all species present. For a weak acid, the following phenomenological approach is valid [19][20][21]:…”

Section: Theoretical Considerationsmentioning

confidence: 99%

Regulation of the retention factor for weak acids in micellar electrokinetic chromatography with cationic surfactant via variation of the chloride concentration

2011

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For tetradecyltrimethylammonium bromide in boric acid/borate or acetic acid/acetate buffer and NaCl or CaCl₂ as the added salt, it is investigated whether the retention behaviour of weak acids in MEKC with cationic surfactant can be modelled by assuming for the deprotonated species predominantly electrostatic interaction with the micelles acting as a pseudostationary ion-exchanger. The retention of (partially) charged solutes by oppositely charged micelles is analyzed by applying the classical theory of IEC (plotting lg k against lg(c(Cl⁻)) assuming a fixed concentration of ion-exchange sites. When plotting the absolute slopes of the regression lines against the absolute effective charge numbers of the analytes, correlation coefficients of 0.968-0.998 were obtained. It is shown that the dependence of the retention factor on the concentration of chloride (the competing ion) in the separation electrolyte and on the degree of dissociation of the analyte corresponds to what would be expected for mixed-mode retention (hydrophobic and ion-exchange interaction) on a pseudostationary ion-exchanger.

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Section: Theoretical Considerationsmentioning

confidence: 99%

Regulation of the retention factor for weak acids in micellar electrokinetic chromatography with cationic surfactant via variation of the chloride concentration

2011

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“…Equation (5) is the retention factor (k T ) for neutral analytes in MEKC derived by Terabe et al [39], where t 0 is the time for an unretained substance (EOF) and t m the time for the micelles to reach the detector. Equation (6) can be used for calculation of the retention factor (k C ) for charged analytes in MEKC [31,40,41] where m eff is the effective mobility of the charged compound in the MEKC system, m eff,aq being the effective mobility of the charged compounds in the pure buffer solution without any micelles and m m is the mobility of the micelles. Using Eq.…”

Section: Equationsmentioning

confidence: 99%

“…The overall effective mobility of the charged analyte in the micellar/microemulsion system is corrected with the effective mobility of the charged compounds in a pure buffer system (without micelles/microemulsion). According to Muijselaar et al [41], certain assumptions must be made when using this equation. The influence of the micelles on the ionic strength, the dielectric constant and the viscosity are regarded as negligible and it is also assumed that an interaction between analyte and micelle monomer does not occur.…”

Section: Additional Experiments To Study the Effective Mobility Of Thmentioning

confidence: 99%

Microemulsion electrokinetic chromatography of drugs varying in charge and hydrophobicity: I. Impact of parameters on separation performance evaluated by multiple linear regression models

et al. 2004

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The separation of anionic, cationic and neutral drugs in microemulsion electrokinetic chromatography (MEEKC) was studied with a statistical experimental design. The concentration of sodium dodecyl sulfate (SDS, surfactant), 1-butanol (co-surfactant) and borate buffer and the factors Brij 35 (surfactant), 2-propanol (organic solvent) and cassette temperature were varied simultaneously, while the parameters pH (9.2), the concentration of octane (oil, 0.8% w/w), the voltage (10 kV) and the dimension of the fused-silica capillary, were kept constant. Eight different model substances were chosen with different hydrophobicities. Two of the analytes were positively charged, two were negatively charged, and the remaining four were neutral or close to neutral at the pH explored. The importance of each parameter on the separation window, the plate height and the retention factor for each of the analytes was studied by means of multiple linear regression (MLR) models. A new response was evaluated for anions, the quotient between the effective mobility in the microemulsion and the effective mobility in the corresponding buffer. Factors affecting selectivity changes were also explored, and it was found that SDS and 2-propanol had the largest effect on selectivity.

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“…The analytes were baseline resolved in one CE run when PVP was present in the carrier electrolyte at a 2.5% (w/v) concentration. In [16] it was demonstrated that differences in overall effective mobilities, based on interaction with a neutral surfactant (polyoxyethylene-23-dodecanol), can be applied for a sample stacking procedure, even if the sample compound is dissolved in a solution with the same ionic strength as that of the applied electrolyte system. Better peak shape and shift of pK a for p-nitrophenol was found in this case.…”

Section: Nonionic Polymersmentioning

confidence: 99%

Application of water‐soluble polymers as modifiers in electrophoretic analysis of phenols

Пирогов

Шпигун

2003

Electrophoresis

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A review of application of water-soluble cationic, anionic and nonionic polymers as pseudostationary phases in capillary electrophoresis (CE) and micellar electrokinetic capillary chromatography (MEKC) is presented. The effect of the structure of the polymers on the selectivity and efficiency of separation is discussed. A novel specially designed cationic polymer, 2,10-ionene, has been used for the separation of phenols. The polymer has hydrophilic and hydrophobic parts in its backbone. The polymer shows the best selectivity as a modifier in capillary zone electrophoresis (CZE)-mode, which allows the selective determination of both hydrophilic and hydrophobic phenols.

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Migration behaviour of monovalent weak acids in micellar electrokinetic chromatography mobility model versus retention model

Cited by 32 publications

References 23 publications

Regulation of the retention factor for weak acids in micellar electrokinetic chromatography with cationic surfactant via variation of the chloride concentration

Regulation of the retention factor for weak acids in micellar electrokinetic chromatography with cationic surfactant via variation of the chloride concentration

Microemulsion electrokinetic chromatography of drugs varying in charge and hydrophobicity: I. Impact of parameters on separation performance evaluated by multiple linear regression models

Application of water‐soluble polymers as modifiers in electrophoretic analysis of phenols

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