Dye-Surfactant Interaction

The interaction of Congo Red (CR) with a series of Alkyl trimethyl
ammonium bromide (CnTAB), N-hexadecyl pyridinium bromide (CPB) and N-hexadecyl pyridinium chloride (CPC) were investigated using conductometry and UV-Vis spectroscopy technique. Job’s method was used to determine the stoichiometric ratio of dye and surfactant in ion pairs. The equilibrium constant and other thermodynamic parameters for the ion pair formation were calculated on the basis of a theoretical model using the data
obtained by conductometry. It was found that an increase in temperature reduces the tendency for ion pair formation as equilibrium constants decrease with increasing temperature. The results showed that as the chain length of the CnTAB molecule in Dye/CnTAB systems was increased, the equilibrium constants
were significantly increased. Therefore, the short range as well as long range  interactions is responsible for the formation of the ion pair. The importance of long range electrical forces is basically to bring the dye anion and the surfactant cation close enough to enable the action of short range interactions whose contribution represents the major part of the standard free energy change for the formation of the anionic dye–cationic surfactant ion pair. The reaction between the dye and the surfactants was revealed to be an enthalpy-driven reaction which is highly dependent on the temperature and the structures of both dye and the surfactant. Prog. Color Colorants Coat. 4(2011), 121-128. © Institute for Color
Science and Technology.

The interactions between an anionic dye and cationic surfactants were investigated using surface tension measurements, spectroscopy, conductometry, and pulsed field gradient NMR (PFG-NMR). Spectroscopic and surface property characterization of the solution as a function of surfactant concentration in the presence of the dye revealed formation of three species: a dye–surfactant ion pair, small mixed aggregates of the dye and surfactant (below the critical micelle concentration (CMC) of these surfactants), and micelles composed of the cationic surfactant. Above the CMC, the dye reverted to its monomeric state or bound to the surface of the micelle. Chemometric resolution analysis confirmed the formation of three species. The hydrodynamic radii of the micelles were determined by self-diffusion coefficient measurements. The average size of the micelles was larger in the presence than in the absence of the dye. Regular solution theory was used to describe the synergistically enhanced ability to form mixed aggregates of dyes and surfactants.

Interaction of tetradecyltrimethylammonium bromide (TTAB), octylophenylpolyoxyethylene ether (TX-100), sodium dodecylsulfate (SDS), N,N′-ditetradecyl-N,N,N′,N′-tetramethyl-N,N′-butanediyl-diammonium dibromide (14,4,14) and N,N′-didodecyl-N,N,N′,N′-tetramethyl-N,N′-butanediyl-diammonium dibromide (12,4,12) with an anionic diazo dye, Congo Red, was investigated using conductometry, spectroscopy, tensiometry, and pulsed field gradient NMR (PFG-NMR). The formation of dye–surfactant ion pairs, their small mixed aggregates (below the critical micelle concentration (CMC) of these surfactants) and surfactant micelles were detected successfully. Above the CMC, the dye reverted to its monomeric state and solubilized in the micelles. Job's method was used to determine the stoichiometric ratio of dye and surfactant in ion pairs and revealed the formation of more hydrophile ion pairs for geminis compared to their conventional analogs. Quantitative results obtained from tensiometry indicated the existence of considerable synergism for cationic surfactants and antagonism for anionic SDS. In addition, the synergism observed for TX-100 revealed the effect of π–π stacking and hydrophobic forces on ion pair and mixed micelle formation. The increase of dye–surfactant interactions by increasing the electrical charge and chain length of cationic surfactants confirmed the importance of both electrostatic and hydrophobic forces in binary dye/surfactant systems. The hydrodynamic radii of the micelles were determined by self-diffusion coefficient measurements. The average size of the cationic and nonionic micelles increased in the presence of CR molecules.

The interactions of anionic day, Mordant Red7 (D1) with two different cationic ligands (ethanol amine and tallow amine) were studied in acidic aqueous solution using UV–VIS absorption spectroscopy. The D1 interacts strongly with oppositely charged ligands. The results have shown that the maximum absorbance of the D1 shifted to higher wavelength in its absorption maxima, and also shows the emergence a new absorption band. The new peak was attributed to the formation of D1 aggregation by intermolecular forces such as hydrophobic forces attraction, Van der Waals forces and hydrogen bonds. The binding constant (Kc) values of the D1 to cationic ligands have been determined by means of Benesi–Hildebrand equation. The magnitude of Kc is large for tallow amine 43.05 x 103 mol-1 L compared to ethanol amine 1.245 mol-1 L. This is because; tallow amine able to self-assemble into micelles (surfactant) at a specific concentration called the critical micelle concentration (CMC), thereby, the D1 b...

Nagpur is a very hot city in India. Tetra pack juices are the most important part of human diet. Therefore it is very necessary to check the quality of these fruit juices and it should be upto the mark. In the present study two homemade juices and two tetrapack juices of Grapes and Pineapple which were sold in local markets were taken. They were analysed for their quality. The parameters checked were Total soluble solids, pH, Ascorbic acid content and acidity. They were determined by standard methods. Resultant parameters of homemade and packed juices were different from each other. It was found that homemade juices were better in terms of nutritional and chemical composition than packaged fruit juices in the market.