Capillary zone electrophoresis of neutral organic molecules by solvophobic association with tetraalkylammonium ion

Walbroehl, Yvonne; Jorgenson, James W.

doi:10.1021/ac00293a047

Cited by 219 publications

(77 citation statements)

References 8 publications

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“…They attribute the separations observed under these conditions to the so-called solvophobic interaction between the analyte molecules and individual surfactant ions. 11,13,14 In the work presented in this paper, we have tried to shed some light on this question. The study involved the measurement of the migration behavior of a number of hydrophobic antioxidants and alkyl aryl phenones as a function of the SDS and AcCN concentration.…”

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confidence: 99%

Mechanism of Electrokinetic Separations of Hydrophobic Compounds with Sodium Dodecyl Sulfate in Acetonitrile−Water Mixtures

1997

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The effect of the addition of 0−70% (v/v) acetonitrile (AcCN) as organic modifier, into a buffer solution containing 0−60 mmol L-1 sodium dodecyl sulfate (SDS), on the electrokinetic behavior of neutral hydrophobic compounds has been studied experimentally. The effective mobilities of the hydrophobic compounds sharply decreased above a certain AcCN concentration, depending to some extent on the SDS concentration. In solutions with up to 40% AcCN, with SDS concentrations below the literature values of the critical micelle concentration, neutral hydrophobic analytes still showed a considerable electrophoretic mobility. The observed mobilities were too high to be attributed to solvophobic interaction of the analytes with single SDS ions. From conductivity measurements, a strong indication was found that increasing the fraction of AcCN in the SDS solution does not lead to a complete disintegration of the micelles. Even with high AcCN concentrations, the mechanism of the separation was found to be a distribution between the aqueous phase and micelle-like SDS aggregates. The influence of the addition of AcCN on the mobilities could be explained as the combined effect of a decrease of the micellar volume fraction, a change of the micellar properties, and a decrease of the distribution constants of the analytes.

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confidence: 99%

Mechanism of Electrokinetic Separations of Hydrophobic Compounds with Sodium Dodecyl Sulfate in Acetonitrile−Water Mixtures

1997

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“…When concentrations are decreased, the separation becomes worse, and finally in 2 mmol/L acetic acid and 2 mmol/L TBA acetate BGE (theoretical ionic strength 2 mmol/L) the peaks are almost comigrating (data not shown). Seemingly pyrene has a small (positive) mobility under present conditions probably due to interaction with the BGE cation (TBA Note that complexation of pyrene and tetraalkylammonium ions (tetrahexylammonium and tetraheptylammonium) has been reported in the literature [43][44][45][46][47]. NM peak appears at all acetate concentrations just before the negative peak produced by the solvent (or by an eigenzone with mobility very close to zero [ 48,49]), which indicates that it is uncharged in all conditions.…”

Section: Selection Of Experimental Conditionsmentioning

confidence: 73%

Electromigration of a heteroconjugated imidazole–acetate complex in ACN

Porras

Jussila

2007

Electrophoresis

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ACN is an extremely poor hydrogen bond donor and therefore the anions dissolved in it are solvated mainly by other hydrogen bond donors (e.g. uncharged acids) possibly present in the solution. Under properly selected experimental conditions stabilization via hydrogen bonding can be used for separation in CE as has been demonstrated for uncharged acids by several authors. Electromigration based on heteroconjugation can be of importance, e.g. when aqueous separation medium cannot be used due to stability reasons. It also allows CE to be used as a tool for solution chemistry measurements, if the required physicochemical properties of the studied system are known or they can be predicted with sufficient accuracy by existing theories. In the present work we showed that also an uncharged base can stabilize an anion via hydrogen bonding in ACN. In the setup imidazole was chosen as a model base and acetate ion as complexing anion in equimolar acetic acid-acetate buffer. The resulted hydrogen-bonded imidazole-acetate complex (i.e. heteroconjugate) possesses a charge and can thus migrate in CE. It was shown that the studied complexation in ACN is sensitive to competition by other hydrogen bond donors such as water and methanol. On the other hand, acetone, which is a poor hydrogen bond donor, did not have much effect on the complexation. To take the effect of ionic strength on mobility into account, mobilities of the imidazole-acetate complex measured at various ionic strengths were corrected to zero ionic strength by the aid of conductivity equation. A fit of the 1:1 binding isotherm to the ionic strength corrected mobility versus acetate concentration data led to rather good correlation. However, x-reciprocal linear transformation of the binding isotherm showed nonlinearity, which could be partly explained by homoconjugation of acetic acid and acetate ion. Since the homoconjugation constant for acetic acid under present experimental conditions was not available, theoretical simulations were used to demonstrate the effects of homoconjugation. The possibility of multiple complexation of imidazole was discussed as well.

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“…At these concentrations, especially in nonaqueous media, the formation of micelles is unlikely, and the separations may be attributed to solvophobic interactions between the analytes and individual surfactant ions [26][27][28].…”

Section: Resultsmentioning

confidence: 99%

Sensitive capillary electrophoresis microchip determination of trinitroaromatic explosives in nonaqueous electrolyte following solid phase extraction

Lu¹,

Collins

Smith

et al. 2002

Analytica Chimica Acta

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Capillary zone electrophoresis of neutral organic molecules by solvophobic association with tetraalkylammonium ion

Cited by 219 publications

References 8 publications

Mechanism of Electrokinetic Separations of Hydrophobic Compounds with Sodium Dodecyl Sulfate in Acetonitrile−Water Mixtures

Mechanism of Electrokinetic Separations of Hydrophobic Compounds with Sodium Dodecyl Sulfate in Acetonitrile−Water Mixtures

Electromigration of a heteroconjugated imidazole–acetate complex in ACN

Sensitive capillary electrophoresis microchip determination of trinitroaromatic explosives in nonaqueous electrolyte following solid phase extraction

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