The Distribution of Higher Alcohols in Aqueous Micellar Solutions

Hayase, Kohji; Hayano, Shigeo

doi:10.1246/bcsj.50.83

Cited by 173 publications

(49 citation statements)

References 11 publications

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“…A good linear relationship was observed for each alcohol between the chromatogram peak area, which corresponds to the alcohol vapor pressure in the headspace, and the total alcohol concentration. This indicates, as previous workers pointed out 13,14 , that Henry's law holds for aqueous alcohol solutions. That is, 701 ANALYTICAL SCIENCES JULY 1999, VOL.…”

Section: Resultssupporting

confidence: 79%

Association of Alcohol-Cyclodextrin in Aqueous Medium Determined by Headspace Gas Chromatography

Zheng

Toda

et al. 1999

ANAL. SCI.

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It is well-known that cyclodextrins (CyD's) form inclusion complexes with alcohols (guests) in an aqueous medium. Such complex formations have been studied by various techniques, which involve NMR 1 , calorimetric [2][3][4][5][6][7] , spectrophotometric 7-9 , and ultrasonic relaxation 10 methods. These studies, however, were exclusively concerned with α-and β-CyD's. To our knowledge, no data have been reported for γ -CyD. nAlcohols associate with α-CyD more strongly than with β-CyD. These guests are closely fitted to the relatively small α-CyD cavity, whereas they are too small in size to be in close contact with the relatively large cavity of β-CyD. 8 Then, it is expected that n-alcohols should associate with γ -CyD more weakly than with β-CyD, because the cavity size of γ -CyD is still larger than β-CyD.Despite weak association of n-alcohols with γ -CyD, these guests play an important role in complexations of γ -CyD with a certain guest of relatively large molecular size, such as pyrene.11 Accurate knowledge of alcohol-CyD association is also needed in the reversedphase LC, where CyD's have been used as a modifier to improve separation by their molecular recognizing ability. 12 Headspace GC is a useful technique to study partition of volatile solutes between gaseous and aqueous phases. This technique is of two types: one is "static headspace", in which the vapor phase is directly injected into a GC column and the other is "enriched head space", which requires trapping of volatile components onto an adsorbent prior to GC injection. The aim of the present work is to demonstrate that static headspace GC is simple and suitable for determining association constants of alcohol-CyD in aqueous medium. This report is the first to present the association constants of alcohols with γ -CyD. Experimentaln-Alcohols (C 4 to C 9 ) and 2-pentanol (Wako Pure Chemical Co.) of the highest commercially available purity were used without further purification. α-, β-, and γ -CyD's of guaranteed grade (Nacalai Tesque Co.), dried over phosphorus pentaoxide under vacuum, were used as received. Deionized distilled water was used throughout the experiments.A known initial concentration of alcohol solution of 20 ml was prepared in a bottle of 27-ml capacity in the absence and presence of CyD of various concentrations. The bottle was sealed with a silicone rubber septum cap with PTFE liner facing toward the bottle headspace. At least three bottles were used for a single sample solution. The bottles were immersed in a 25.0±0.1˚C water bath for one day with occasional gentle swirling. After equilibration, vapor samples (200 µl) were withdrawn from the headspace of the sealed bottles with a gas-tight syringe (Shimadzu HSS-2B) and directly injected into a Shimadzu GC-14A gas chromatograph. The GC conditions were as follows: a 3.2 mm×2.1 m column packed with SE-30 (60 -80 mesh), a FID detector, and a operating temperature of 120 -160˚C. Results and DiscussionCalibration curves were prepared in the absence of CyD using alcohol solutions of five ...

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Section: Resultssupporting

confidence: 79%

Association of Alcohol-Cyclodextrin in Aqueous Medium Determined by Headspace Gas Chromatography

Zheng

Toda

et al. 1999

ANAL. SCI.

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“…[40][41][42][43][44] The alcohols are included in the micelles, and partition coefficients describing the inclusion increase with increasing alcohol chain length. [44][45][46][47][48] Although doubts were once expressed over the inclusion of C 3 alcohols, 47 Stilbs demonstrated by NMR that 1-propanol and 2PN are included in SDS micelles. 49,50 In the absence of alcohol or electrolyte, an SDS micelle binds ∼75% of its sodium counterions to reduce electrostatic repulsion Figure 7.…”

Section: Origin Of Variation Ofmentioning

confidence: 99%

Influence of Organic Modifier Concentration on Plate Number in Micellar Electrokinetic Chromatography. 1. 2-Propanol

et al. 1998

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This paper establishes a physicochemical basis for the efficiency losses in micellar electrokinetic chromatography in buffers containing sodium dodecyl sulfate (SDS) and 2-propanol (2PN). Weakly, intermediately, and strongly retained analytes were separated in phosphate/borate buffers containing 50 mM SDS and from 0 to 10% 2PN by volume. Their plate numbers N generally agreed well with predictions of a theory for N based on longitudinal diffusion and instrumental contributions to dispersion. The N's of weakly and intermediately retained analytes were not affected strongly by 2PN over this concentration range, because their diffusion coefficients varied inversely with buffer viscosity and their retention times largely varied directly with viscosity. These combined effects on dispersion almost canceled. However, the N's of strongly retained analytes decreased with increasing 2PN, because their diffusion coefficients varied inversely with viscosity but their retention times increased more rapidly than did viscosity. These combined effects on dispersion did not cancel. These differences occurred because 2PN penetrated the micelles, caused bound counterions to be released, and increased the micellar charge and electrophoretic mobility. As 2PN concentration increased, the micelles electrophoresced increasingly rapidly against the electroosmotic flow. Consequently, strongly retained compounds required increasingly long times to elute.

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“…Propanol and higher alcohols, which are known microemulsion cosurfactants, in contrast to methanol or ethanol, have apparently no such dramatic effect on the micellization process per se, though the degree of surfactant aggregation is probably lowered [6][7][8]. However, since their presence affects many of the overall properties of aqueous micellar solutions [9][10][11][12], even more than methanol or ethanol do, it is usually assumed that other interactions play a more important role.In an attempt to sort out some of the three possible effects mentioned above, the explicit aim of this investigation is to compare the influence of the aqueous miscibility of alcohol cosurfactants on the energetic patterns of their dissolution in aqueous surfactant solutions, and that of the surfactant in water-alcohol mixtures. Two sets of calorimetric experiments were designed and their results are reported here: enthalpies…”

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confidence: 99%

Enthalpies of solution in sodium octanoate + water + alcohol mixtures

Kertes

Tsimering

Garti

1985

Colloid & Polymer Sci

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Enthalpies of solution of sodium octanoate in water, 1-propanol and aqueous mixtures of l-propanol, 1-butanol, 1-pentanol and 1-hexanol, and of the alcohols in aqueous solutions of sodium octanoate at various concentrations were determined calorimetrically at 35 ~ Most AH(soln) values are exothermic and strongly dependent on the solute concentration. The main energetic factor governing the process of dissolution of the surfactant is associated with changes in the water structure caused by the presence of alcohol. That governing the process of the alcohol dissolution in surfactant solutions is due to the effect alcohols have on the CMC of the octanoate. There is no indication of the alcohol being either solubilized in the interior of the aqueous micelle, or becoming part of the micellar film.The solubility at 35 ~ of sodium octanoate in water, 1-propanol and their mixtures has also been determined. In the previous reports [1][2][3][4] in these series the calorimetrically determined enthalpies of solution in some model ternary colloidal systems have been interpreted in terms of solute-solvent interactions between the components. We believe we have provided considerable evidence to show that the energetics of solubilities in such simpler systems -which can be regarded as limiting cases for the more complex, four-component microemulsion -are helpful in understanding the balance of forces which define microemulsion stability. In this balance of forces the role of the alcohol cosurfactant is perhaps the most complex one. Namely, the hydrophilic -hydrophobic balance of a microemulsion is governed primarily by the extent of water or oil miscibility of the alcohol cosurfactancThe presence of any third component in aqueous solutions of ionic surfactants is known to have an effect on the micellar properties of the binary solutions. With an aliphatic alcohol as the third component the effect is generally due to any single one or a combination of the basic processes characterized as (i) the change in the solvent structure, (ii) the solubilization of the alcohol in the interior of the aqueous micelle, and (iii) the incorporation of the alcohol molecules into the O 849 micelles in the form of mixed micellar films. A separate identification of these effects is by no means trivial. Methanol or ethanol are considered to affect micelle formation by virtue of their effect on the solvent structare, and no micelles of ionic surfactants are formed in mixed aqueous solutions containing 30-40 volume percent of the alcohols [5]. Propanol and higher alcohols, which are known microemulsion cosurfactants, in contrast to methanol or ethanol, have apparently no such dramatic effect on the micellization process per se, though the degree of surfactant aggregation is probably lowered [6][7][8]. However, since their presence affects many of the overall properties of aqueous micellar solutions [9][10][11][12], even more than methanol or ethanol do, it is usually assumed that other interactions play a more important role.In an attempt t...

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The Distribution of Higher Alcohols in Aqueous Micellar Solutions

Cited by 173 publications

References 11 publications

Association of Alcohol-Cyclodextrin in Aqueous Medium Determined by Headspace Gas Chromatography

Association of Alcohol-Cyclodextrin in Aqueous Medium Determined by Headspace Gas Chromatography

Influence of Organic Modifier Concentration on Plate Number in Micellar Electrokinetic Chromatography. 1. 2-Propanol

Enthalpies of solution in sodium octanoate + water + alcohol mixtures

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