Hydrotrope Concentration Research Articles

Thermodynamic Study for Aggregation Behavior of Hydrotropic Solution

Aggregation behavior of sodium salicylate and sodium cumene sulfonate was studied in aqueous solution at different temperature. Specific conductivity and relative viscosity were measured at different temperature to find minimum hydrotropic concentration. The thermodynamic parameters (free energy, enthalpy and entropy) were evaluated in the temperature range of 30C-70C. The free energy decreased with increase in temperature. The aggregation was found to be exothermic in nature and favored by positive value of entropy. Keywords—Hydrotropes, Enthalpy, Entropy, Free Energy, Minimum Hydrotropic Concentration.

Effect of hydrotropes on solubility and mass transfer coefficient of lauric acid

A comprehensive investigation on the solubility and mass transfer coefficient enhancement of lauric acid through hydrotropy has been undertaken. The solubility and mass transfer studies were carried out using hydrotropes such as sodium cumene sulfonate, sodium p-xylene sulfonate and sodium p-toluene sulfonate under a wide range of hydrotrope concentrations (0 to 3.0 mol/L) and different system temperatures (303 to 333 K). The effectiveness of hydrotropes was measured in terms of Setschnew constant Ks and reported for all hydrotropes used in this study. The solubility data are also fitted in a polynomial equation as the function of hydrotrope concentration.

Separation of a Phenol/o-Chlorophenol Mixture through Hydrotropy

A comprehensive study on the effect of hydrotropes such as urea, citric acid, sodium salicylate, and nicotinamide on the separation of phenol from phenol/o-chlorophenol mixtures under a wide range of hydrotrope concentrations, (0 to 3.0) mol·L−1, and different system temperatures, (303 to 333) K, has been undertaken. The performance of hydrotropes toward separation of phenol was measured in terms of the Setschenow constant KS. A Minimum Hydrotrope Concentration (MHC) in the aqueous phase was found essential to initiate significant separation of phenol from the phenol/o-chlorophenol mixture. The maximum enhancement factor which is the ratio of the percentage extraction value in the presence and absence of a hydrotrope has been determined for each case.

Hydrotropic Study on Furfural - Comprehensive Design Expert Plot

This work presents a comprehensive investigation on the solubility and mass transfer coefficient enhancement of furfural through Hydrotropy. The solubility and mass transfer coefficient studies were carried out using hydrotropes such as urea, tri-sodium citrate, sodium toluate and sodium benzoate under a wide range of hydrotrope concentrations (0 to 3.0 mol/L) and different system temperatures (303 to 333 K). The solubility of furfural increases with increase in hydrotrope concentration and also with system temperature. A Minimum Hydrotrope Concentration (MHC) in the aqueous phase was required to initiate significant solubilization of furfural. Consequent to the increase in solubilization of furfural, the mass transfer coefficient was also found to increase with increase in hydrotrope concentration. A threshold value of MHC is to be maintained to have an appreciable enhancement in the mass transfer coefficient. The maximum enhancement factor, which is the ratio of the value in the presence and absence of a hydrotrope, has been determined for all sets of experimentations. A comprehensive design expert plot for hydrotropic effect on furfural is also presented.The performance of hydrotropes was measured in terms of Setschnew constant Ks and reported for all hydrotropes used in this study.

The effect of hydrotropes on the solubility and mass transfer coefficient of 2-nitrobenzoic acid

The effect of hydrotropes on the solubility and mass transfer coefficient of 2-nitrobenzoic acid A comprehensive investigation on the solubility and mass transfer coefficient enhancement of 2-nitrobenzoic acid through hydrotropy, has been undertaken. The solubility and mass transfer coefficient studies were carried out using hydrotropes such as sodium acetate, citric acid and nicotinamide under a wide range of hydrotrope concentrations (0 to 3.0 mol/L) and different system temperatures (303 to 333 K). It was found that the solubility and mass transfer coefficient of 2-nitrobenzoic acid increases with an increase in hydrotrope concentration and also with system temperature. All hydrotropes used in this work showed an enhancement in the solubility and mass transfer coefficient to different degrees. The maximum enhancement factor value has been determined for both the solubility and mass transfer coefficient. The effectiveness of hydrotropes was measured in terms of Setschnew constant Ks and reported for all the hydrotropes used in this study.

Effective Separation of Petro Products through Hydrotropy

AbstractThis paper presents a comprehensive study on the effect of hydrotropes such as sodium salicylate, sodium benzoate, and nicotinamide on the separation of a near boiling mixture, o‐/p‐xylene. The influence of a wide range of hydrotrope concentrations (0 to 3.0 mol/L) and different system temperatures (303 to 333 K) on the separation of o‐/p‐xylene were studied. All hydrotropes used in this work showed an enhancement in the percentage extraction of p‐xylene to different degrees. The percentage extraction of p‐xylene from the o‐/p‐xylene mixture increases with an increase in hydrotrope concentration and also with system temperature. A minimum hydrotrope concentration (MHC) was found essential to initiate significant extraction of p‐xylene from the o‐/p‐xylene mixture. The maximum enhancement factor, which is the ratio of the value in the presence and absence of a hydrotrope, was determined for both cases. The Setschenow constant, ks, a measure of the effectiveness of a hydrotrope, was determined for each case.

Molecular simulation of sodium butyl benzene sulfonate at air–water interface and in aqueous solution

Molecular mechanics(MM) calculations for interfacial behaviour of sodium n-butyl benzene sulfonate (NaNBBS), sodium iso-butyl benzene sulfonate (NaIBBS) and sodium tert-butyl benzene sulfonate (NaTBBS) show a significant effect of the butyl group geometry on the surface area occupied by these molecules at the air–water interface. NaNBBS, in comparison with NaIBBS and NaTBBS, shows a closer molecular packing at the interface. The simulation predicts minimum hydrotrope concentration of each hydrotrope to reach surface saturation and molecular surface area at the interface match with good accuracy. The shape, size and charge of the hydrotrope aggregates obtained by molecular dynamics simulation also match well with the results of small angle neutron scattering experiments on the same hydrotrope. The simulation shows non-regular and ellipsoidal hydrotropes aggregates with substantial charge on the surface. The aggregates are also more open structures as compared to surfactant micelles. The water accessible surface area of a NaNBBS aggregate was 25% lower in comparison to that of NaTBBS aggregate, indicating closer packing of NaNBBS molecules. The fractional charge on the NaNBBS aggregate decreases with the increase in the number of NaNBBS molecules in the aggregate indicating more counter-ion association.

Hydrotropic extraction of bioactive limonin from sour orange ( Citrusaurantium L.) seeds

Limonoids are potential bioactive compounds present only in citrus among fruits and vegetables. A new process for extraction of limonoid aglycones from sour orange ( Citrus aurantium L.) seeds was investigated using aqueous hydrotropic solutions. The extraction efficiency was dependent on hydrotrope concentration, extraction temperature and percent of raw material loaded. Two hydrotropes such as sodium salicylate (Na-Sal) and sodium cumene sulphonate (Na-CuS) were studied using Box-Behnken experiment design. Response surface analysis (RSA) of data was performed to study the effect of parameters on extraction efficiency. Prominent limonoid aglycone such as limonin was extracted and quantified for process optimization. Both hydrotropes gave maximum limonin yield at 2 M concentration, extraction temperature of 45 °C and 10% solid loading. A maximum limonin yield of 0.65 mg/g seeds was obtained using Na-CuS whereas only 0.46 mg/g seed was obtained using Na-Sal. Using this process, the use of organic solvents can be reduced dramatically to keep the process environmental friendly for the extraction of bioactive compounds.

Enhancement of Solubility and Mass Transfer Coefficient Through Hydrotropy

This paper presents a comprehensive study on the effect of hydrotropes on the solubil- ity and mass transfer coefficient of ethyl acetate in water. The solubility and mass transfer studies were performed using hydrotropes such as tri-sodium citrate, urea, sodium benzoate, and sodium salicylate under a wide range of concentrations (0 to 3.0 mol/L) and system temperatures (303 to 333 K). The performance of the hydrotropes was measured in terms of the Setschenow constant (Ks). It was found that the solubility of ethyl acetate increases with increase in hydrotrope con- centration and also with system temperature. A Minimum Hydrotrope Concentration (MHC) in the aqueous phase was found required to initiate significant solubilization of ethyl acetate. Con- sequent to the increase in solubilization of ethyl acetate, the mass transfer coefficient was also found to increase with increase in hydrotrope concentration. All hydrotropes used in this work showed an enhancement in the solubility and mass transfer coefficient to different degrees. The maximum enhancement factor, which is the ratio of the value in presence and absence of a hy- drotrope, has been determined for both solubility and mass transfer coefficient. These character- istics would be much useful in increasing the rate of output of the desired product made from ethyl acetate. In addition, the separation of ethyl acetate from any liquid mixture which is found to be difficult can be carried out effectively using this technique.

Characterization of mixed micelles of structural isomers of sodium butyl benzene sulfonate and sodium dodecyl sulfate by SANS, FTIR spectroscopy and NMR spectroscopy

The mixed systems of sodium dodecyl sulfate (SDS) and sodium salts of n-butyl benzene sulfonate (NBBS), iso-butyl benzene sulfonate (IBBS) and tert-butyl benzene sulfonate (TBBS), as hydrotropes, are studied by Small Angle Neutron Scattering (SANS), Fourier Transform Infrared (FTIR) spectroscopy and Nuclear Magnetic Resonance (NMR) spectroscopy for the effect of hydrotrope concentration, hydrotrope structure, and temperature on the SDS micelles. The mixed micelle formation of SDS with NBBS is confirmed with the contrast matching technique. NBBS when mixed with SDS replaces some of the SDS molecules from the micelle affecting its size. The hydrotrope structure shows a prominent effect on the dimensions of the mixed micelle. The behavior of NBBS, in the SDS–NBBS mixtures, is different from that of NaCl and is not the same as the salt effect. Higher temperatures result in the formation of smaller SDS–NBBS mixed micelles in the solutions. The FTIR spectroscopy results indicate enhanced gauche/trans conformer ratio of SDS in the mixed micelles unlike the reduction of the ratio in the mixed micelles of a cationic surfactant with NBBS. The up-field chemical shifts of the aromatic protons of the hydrotrope and the methylene protons of surfactant adjacent to ionic headgroup indicate that the hydrotrope resides near the surface of the SDS micelle.

The photophysical determination of the minimum hydrotrope concentration of aromatic hydrotropes

A method based on the aggregate to monomol emission ratio, I(aggr)/I(monomol), was used to determine the minimal hydrotropic concentration (MHC) of aromatic hydrotropes. The main advantage of this method is that it does not require the use of probes or other additives, which might disrupt the aggregation process. Also, it relies on spectrophotometric measurements, which are more sensitive and less arduous than others, like conductivity, light scattering and surface tension.

Solubilization of indomethacin using hydrotropes for aqueous injection

Indomethacin is a non-steroidal anti-inflammatory drug (NSAID) that exhibits analgesic, antipyretic and anti-inflammatory activities. It is practically insoluble in water. The effect of various hydrotropes such as urea, nicotinamide, resorcinol, sodium benzoate and sodium p-hydroxy benzoate on the solubility of indomethacin was investigated. The solubility enhancement of indomethacin by the hydrotropes was observed in decreasing order as sodium p-hydroxy benzoate > sodium benzoate > nicotinamide > resorcinol > urea. In order to elucidate the probable mechanism of solubilization, various solution properties of hydrotropes such as viscosity, specific gravity, surface tension, refractive index and specific conductance of hydrotropic solutions were studied at 25 ± 2 °C. Each solubilized product was characterized by ultraviolet, infrared, powder X-ray diffraction and differential scanning calorimetry techniques. The hydrotropic solubilization of indomethacin at lower hydrotrope concentration may be attributed to weak ionic interactions while that at higher hydrotrope concentration may be due to molecular aggregation. Aqueous injectable formulations using sodium p-hydroxy benzoate, sodium benzoate and nicotinamide as hydrotropes were developed and studied for physical and chemical stability.

Syntheses of Quinolines by Friedlander's Heteroannulation Method in Aqueous Hydrotropic Medium

In the current work, quinolines have been synthesized for the first time by Friedlander's method in hydrotropic aqueous medium. The article describes a brief study of solubility of reactants in aqueous medium, with different concentrations of hydrotropes and respective yield of the products. The extent of solubilization of the reactants, in aqueous medium, has been measured, as minimum hydrotropic concentration (MHC). The suitability of the hydrotrope was confirmed, by the yield of the reactions.

Selective Extraction of Embelin from Embelia ribes by Hydrotropes

The research work proposes an alternate strategy of the extraction of embelin (2,5‐dihydroxy‐3‐undecyl‐p‐benzoquinone) from Embelia ribes. The aromatic hydrotropes such as sodium n butyl benzene sulfonate (NaNBBS), and sodium cumene sulfonate (NaCS) were found to be effective for the selective extraction of embelin with a recovery of 95% embelin from the aqueous solution of hydrotropes with high purity. The process was further optimized with respect to concentration of hydrotropes and temperature of extraction.

Hydrotropic Enhancement of Rate of the Browning Reaction; A Kinetic Study

The rate of a nonenzymatic browning reaction, that is, the reaction between reducing sugar and amino acid(commonly known as Millard reaction) is strongly enhanced in the presence of a common hydrotrope viz. sodium benzoate or sodium salicylate even below its minimal hydrotropic concentration (MHC). The effect of hydrotrope on the rate has been studied in four systems taking combination of different reducing sugars (glucose and fructose) and amino acids (glycine and alanine) in alkaline conditions. The kinetic data support the formation of the mixed aggregation between the hydrotrope and the reactants. The kinetic rate law consistent with experimental results has been derived on the basis of the proposed mechanism.

Effect of temperature on aggregation behavior of aqueous solutions of sodium cumene sulfonate

Aqueous solutions of sodium cumene sulfonate are characterized by various experimental techniques for its aggregation behavior as a function of temperature. Surface tensiometry, volumetric changes, vapor pressure osmometry, fluorescence polarization studies and enthalpy changes show changes in the solutions with increasing concentration and temperature. The apparent and partial molal volumes of the hydrotrope, derived from the density measurements, show a sharp increase at a characteristic minimum hydrotrope concentration. The osmotic coefficient of NaCS, obtained from vapor pressure osmometry, shows a significant deviation indicating aggregation of the hydrotrope molecules in aqueous solutions. NaCS, when used as an intrinsic fluorescent probe, reveals a non-polar environment in the aggregate with substantial microviscosity. The enthalpies of micellization obtained directly from the calorimetric measurements show a trend towards lower values with increasing temperature.

Citrus Bioactive Limonoid Extraction using Environment-friendly Hydrotropy

Citrus consumption has been shown to promote human health due to presence of several bioactive compounds. In the process of understanding the health benefits of citrus, we need to isolate and characterize these compounds. Limonoids are one of such prominent, but lesser-known phytonutrients that have been shown to prevent cancers of the mouth, skin, lung, breast, and colon. With the growing interest in the health-promoting properties of citrus limonoids, the demand for these bioactives has significantly increased. It has been critical to explore environment-friendly extraction methods rather than using hazardous organic solvents. A water-based hydrotropic extraction of limonoid aglycones from sour orange (Citrus aurantium L.) seeds was developed. Two hydrotropes, sodium salicylate (Na-Sal) and sodium cumene sulfonate (Na-CuS), were studied for extraction efficiency using the Box Behnken experiment design method. The extraction efficiency of prominent aglycone limonin was observed depending on hydrotrope concentration, extraction temperature, and percentage of raw material loading. Response Surface Analysis (RSA) of data predicted the optimum conditions for maximum yield. Recovery of aglycones from filtered extract is also easily achieved by mere dilution using water at pH 3 or 7 or by partitioning the extract with dichloromethane. At optimum conditions, limonin yield of 0.46 mg/g seeds in the case of Na-Sal extraction and 0.65 mg/g seeds in the case of Na-CuS extraction was achieved. The results demonstrated that the hydrotropic extraction process of limonoid aglycones has practical commercial importance. This project is based upon work supported by the USDA–CSREES IFAFS #2001 52102 02294 and USDA–CSREES #2005-34402-14401 “Designing Foods for Health” through the Vegetable and Fruit Improvement Center.

Aqueous Hydrotropic Solution as an Efficient Solubilizing Agent for Andrographolide from Andrographis paniculata Leaves

An aqueous solution based extraction process for andrographolide from Andrographis paniculata leaves has been developed using alkyl benzene sulfonates and carboxylates as hydrotropes. The plant cells are permeabilized by the hydrotrope solutions followed by solubilization of andrographolide into the solutions. The extraction and solubilization of andrographolide is affected by structure and concentration of hydrotrope, temperature and particle size. Sodium cumene sulfonate (Na‐CS) shows the most efficient solubilization of andrographolide amongst the hydrotropes studied. The solubility of andrographolide increased by two orders of magnitude in Na‐CS aqueous solutions and ∼96% andrographolide extraction was achieved in just 20 min.

Hydrotropic Enhancement of Rate of Ninhydrin‐α‐Amino Acid Reaction: A Kinetic Study

The kinetics of ninhydrin‐α‐amino acid (alanine, phenylalanine, and valine) reaction have been studied in the absence and in the presence of a common hydrotrope, sodiumbenzoate. A strong enhancement in the rate of reaction has been observed in the presence of the hydrotrope above its minimal hydrotrope concentration (MHC). The order of reaction in ninhydrin was always found to be unity while that in amino acid decreases from unity to zero at higher [Aminoacid]. A mechanism consistent with kinetic data and involving the formation of a mixed aggregation assemblies between amino acid and hydrotrope has been proposed.

Effect of Hydrotropes on the Solubility and Mass Transfer Coefficient of Benzyl Benzoate in Water

This work presents a comprehensive study on the effect of hydrotropes on the solubility and mass transfer coefficient of benzyl benzoate in water. The solubility studies were performed using hydrotropes such as tri-sodium citrate, urea, sodium benzoate, and sodium salicylate for various concentrations in the range from (0 to 3.0) mol·L-1 and system temperatures ranging from T = (303 to 333) K. The performance of the hydrotropes was measured in terms of the Setschenow constant (KS). It was found that the solubility of benzyl benzoate increases with an increase in hydrotrope concentration and also with system temperature. A minimum hydrotrope concentration (MHC) in the aqueous phase was required to initiate significant solubilization of benzyl benzoate. Consequent to the increase in solubilization of benzyl benzoate, the mass transfer coefficient was also found to increase with an increase in hydrotrope concentration. All hydrotropes used in this work showed an enhancement in the solubility and mass transfer coefficient to different degrees. The maximum enhancement factor, which is the ratio between the presence and absence of a hydrotrope, has been determined for both cases. However, a threshold value of the MHC was found essential to initiate significant increase in hydrotrope concentration.