A partition equilibrium study of sulfonephthalein dyes in anionic surfactant systems: determination of CMC in buffered medium

Saikia, Palash M.; Kalita, Achyut; Gohain, Biren; Sarma, Surashree; Dutta, Robin K.

doi:10.1016/s0927-7757(02)00545-9

Cited by 20 publications

(32 citation statements)

References 25 publications

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“…Therefore, the dye could partition only between the aqueous pseudophase and the oil-water interface (17)(18)(19). The presence of the isosbestic point indicates the presence of an equilibrium between the dye in the aqueous pseudophase of the droplets and the oil-water interface, no matter in which form the dye existed in the aqueous pseudophase (14)(15)(16)(17)(18)(19). Similar variations were observed in the visible spectra of BPB in the w/o microemulsions of water in toluene with different volume fractions of water.…”

Section: Resultssupporting

confidence: 54%

Partition of bromophenol blue in toluene/water/sodium bis(2‐ethylhexyl)‐sulfosuccinate water‐in‐oil microemulsions

Sarma

Dutta

2005

J Surfact & Detergents

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The partition of bromophenol blue between oil-water interfaces and water droplets in water-in-oil microemulsions of toluene/water/sodium bis(2-ethylhexyl)sulfosuccinate was studied by a spectroscopic method at different water fractions and pH. The partition equilibrium constant, K p , between the two domains decreased considerably with an increase in the water fraction and pH. The decrease in K p with an increase in the water fraction suggests the retention of more dye molecules in water. The decrease in K p with an increase in pH has been attributed to a lower tendency of the base form to associate with the anionic oil-water interface compared with that of the acid form and to an increase in the negative charge density at the oil-water interface at a higher pH.Paper no. S1484 in JSD 8, 277-281 (July 2005). KEY WORDS:Aerosol OT, AOT, bromophenol blue, partition equilibrium, sulfonephthalein dye, toluene, W/O microemulsion.Knowledge of the microstructure of microemulsions is important for their applications in physicochemical and technological processes (1,2). The partition of solutes between the polar droplet core, the apolar bulk solvent, and the interface may affect the microstructure and determine the physicochemical properties of microemulsions. It is also important for determining the possible localization/distribution of reagents and the reaction positions in microemulsions (3). The pseudophase ion-exchange model has been widely used for describing the partition behavior and reaction rates in micellar solutions (4). The method also has been applied to study partition equilibria of solutes between different pseudophases of microemulsions (5-8). Although several reports can be found in the literature on partition equilibria and the acid-base behavior of solutes or indicator dyes in microemulsion systems, most of them involve the partition between all three pseudophases, viz., oil, water, and the oil-water interface (3,9-13).We have developed an equilibrium method that allows us to determine equilibrium constants of the partition of dyes between aqueous and micellar pseudophases. The method has been applied to predict apparent pK a of the dyes in micellar solutions of surfactants of different charge types, where the dye is partially incorporated into the micelles (14-16). Recently, this partition equilibrium approach has been extended to o/w (oil-in-water) microemulsions to gain information on microemulsion microstructure and behavior (17). We have also applied the partition equilibrium approach to study the effects of alcohols as cosurfactants and the change in pH on partition equilibrium of a dye, viz., phenol red in o/w microemulsions (18,19). The partition equilibrium approach is a simple and time-saving approach, and the studies add to the lack of direct information on microemulsion microstructure, with some assumptions widely present in the literature. The studies carried out so far have involved only o/w microemulsions stabilized by anionic surfactants, viz., sodium dodecyl sulfate and sodium dodecyl be...

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Section: Resultssupporting

confidence: 54%

Partition of bromophenol blue in toluene/water/sodium bis(2‐ethylhexyl)‐sulfosuccinate water‐in‐oil microemulsions

Sarma

Dutta

2005

J Surfact & Detergents

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“…is the concentration of the dye in the aqueous solution, or [19,20]. The association constant, K ass , can be determined using the equation described earlier [19], …”

Section: Stepmentioning

confidence: 99%

“…Most of the studies reported so far have dealt with systems where the dye is completely micellized or at least the dye binds to the micelles in both its acid and base forms. A few of the studies reported so far have dealt with acid-base equilibria of indicator dyes in aqueous ionic micellar media, where the dye is partially bound to the micelles [17][18][19][20][21][22]. However, there is hardly any report of the study of such acid-base equilibria where the dye is not completely incorporated into the micelles involving nonionic surfactants.…”

Section: Introductionmentioning

confidence: 99%

“…We have recently reported a partition equilibrium method in which the partition constant of such indicator dyes between the micellar and aqueous pseudophases, along with the CMC of the surfactant in well-buffered micellar solutions of anionic surfactant, can be determined without the use of any B-H type of plot [19]. In the present paper, the same method has been modified to hold for dye-nonionic surfactant systems and the method has been tested with experimental pK a 2 .…”

Section: Introductionmentioning

confidence: 99%

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Acid–base equilibrium of anionic dyes partially bound to micelles of nonionic surfactants

Saikia

Bora

Dutta

2005

Journal of Colloid and Interface Science

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“…To support this conclusion, cmc of the investigated surfactants was also determined conductometrically in a buffer medium of pH 8.0 in the presence of nucleophile, [2-PAM] = 1 × 10 −3 M. As depicted in Table V, a reduction in cmc values was observed for all the cationic surfactants and thus the formation of micelles or premicellar aggregates in the reaction medium can be assumed [33]. Also, it has been documented that with a rise in pH, cmc of surfactants generally decreases [34,35]. However, it is likely that the extent of attack of oximate ions at the carbon center (C O) is influenced by a number of factors apart from lipophilicity, including the nucleophilicity of the α-effect nucleophile, structure of the surfactant, and polarity of the medium [36].…”

Section: Effect Of Cationic Surfactantsmentioning

confidence: 99%

Hydrolysis of carboxylate and phosphate esters using monopyridinium oximes in cationic micellar media

Singh

Ghosh

Marek

et al. 2011

Int J of Chemical Kinetics

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The reactions of p-nitrophenyl acetate (PNPA) with a series of monopyridinium oximes, viz. 2-PAM (2-hydroxyiminomethyl-1-methylpyridinium iodide), 3-PAM (3-hydroxyiminomethyl-1-methylpyridinium iodide), and 4-PAM (4-hydroxyiminomethyl-1-methylpyridinium iodide) have been studied in the presence of cationic surfactants of same hydrophobic chain length (C 16 ) within the concentration range of 0.5-6.0 mM at pH 8.0 under the pseudo-first-order condition. The observed rate constant (k obs ) increases with increasing surfactant concentration culminating into a maximum, and this has been analyzed in detail following the concepts of micellar catalysis. The structure-activity relationship of the investigated oximes has been discussed, and 2-PAM was found to be the most reactive among all the three investigated oximes for the cleavage of PNPA. Esterolytic decomposition of pnitrophenyldiphenyl phosphate with oximate ions ( CH NO − ) was followed in cetyltrimethylammonium bromide micelles at pH 9.0, and 4-PAM was the most reactive oxime for the micellar hydrolysis of phosphate ester. The apparent acid dissociation constants (pK a ) of the investigated oximes have been determined spectrophotometrically. C

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A partition equilibrium study of sulfonephthalein dyes in anionic surfactant systems: determination of CMC in buffered medium

Cited by 20 publications

References 25 publications

Partition of bromophenol blue in toluene/water/sodium bis(2‐ethylhexyl)‐sulfosuccinate water‐in‐oil microemulsions

Partition of bromophenol blue in toluene/water/sodium bis(2‐ethylhexyl)‐sulfosuccinate water‐in‐oil microemulsions

Acid–base equilibrium of anionic dyes partially bound to micelles of nonionic surfactants

Hydrolysis of carboxylate and phosphate esters using monopyridinium oximes in cationic micellar media

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