Range Of Solvent Compositions Research Articles

Comment on “Solubility of Trimethoprim in Selected Pure Solvents and (Water + Ethanol/2-Propanol) Mixed-Solvent Systems”

Mathematical representations reported by Yin and co-workers for the Combined Nearly Ideal Binary Solvent (NIBS)/Redlich–Kister model are carefully examined in regards to the model’s ability to predict the solubility of trimethoprim dissolved in binary aqueous-2-propanol and aqueous-ethanol solvent mixtures. The equation coefficients reported by Yin and co-workers were found to give calculated mole fraction solubilities in the two alcohol monosolvents that exceed unity. The narrow range of solvent composition over which the authors performed solubility measurements does not enable one to derive mathematical correlations for predicting the solubility of trimethoprim in the alcohol-rich solvent composition region.

Anionic polyelectrolyte poly(acrylic acid) (PAA) chain shrinkage in water–ethanol solution in presence of Li+ and Cs+ metal ions studied by molecular dynamics simulations

Molecular dynamic simulations of anionic polyelectrolyte poly(acrylic acid) (PAA) in water–ethanol solution, specifically Li+-PAA and Cs+-PAA, were carried out across the solvent composition range 0 ≤ фeth ≤ 0.9. Chain collapse (i.e. shrinkage) occurs with increase in фeth for both types of counter-ion systems and in agreement with the experiments. The qualitative difference in the collapse point is in agreement with experimental results, with counter-ion specific chain collapse of PAA following the order Li+ > Cs+. With increase in фeth the number of hydrogen-bonds between PAA and water decreases while that between PAA and ethanol increases. At higher level of ethanol content in solution, ethanol molecules displace water molecules from the vicinity of the chain. The analysis of the radial distribution functions shows that counter-ion binding distance of Li+ to chain is lesser as compared to that of Cs+, as well as a higher coordination number exhibited by Li+. Thus, as compared to Cs+-PAA, greater number of contact ion pairs formed between Li+ and PAA induce chain collapse more easily. The coordination of Li+ to PAA is better than that of Cs+ throughout the фeth range, which could be the reason for the greater extent of PAA chain shrinkage observed in the case of Li+. Binding of water molecule to PAA units is stronger in the case of Cs+. The backbone dihedral trans probability of both systems displayed a decrease with фeth indicating chain shrinkage. The relaxation time of H-bonds between PAA and EtOH is greater for Li+-PAA as compared to Cs+-PAA system. The enhancement of counter-ion pairs formation is found to be directly responsible for the solvent composition at which chain collapse occurs in the particular system.

Thiol-ene micropillar array electrospray ionization platform for zeptomole level bioanalysis.

A micropillar array electrospray ionization (μPESI) platform fabricated from thiol-enes with 56 individual polyethylene glycol coated μPESI chips for bioanalytical mass spectrometry is introduced. Bioanalysis capability is shown by measurement of a protein, a protein digest and a cell lysate sample. The thiol-ene polyethylene glycol (PEG) coated μPESI chip allows the use of a wide range of aqueous-organic solvent compositions and provides a detection limit at 60 zeptomole level (6 × 10-20 mol) for a peptide standard.

Thermodynamic solubility and density of sildenafil citrate in ethanol and water mixtures: Measurement and correlation at various temperatures

Solubility of sildenafil citrate (SC) in binary aqueous mixtures of ethanol (EtOH) was studied at 293.2, 298.2, 303.2, 308.2 and 313.2K. Density of the SC saturated solutions over the entire solvent composition and temperature range was measured using a pycnometer. The effect of solvent composition on solubility, enthalpy, entropy and Gibbs energy was studied according to van't Hoff and Gibbs equations. The experimental solubility and densities were used to estimate solubility in the investigated solvent system using the van't Hoff and Jouyban-Acree models.

Optimal mixing rate in linear solvent strength gradient liquid chromatography. Balanced mixing program

The mixing rate (Rϕ) is the temporal rate of increase in the solvent strength in gradient LC. The optimal Rϕ (Rϕ,Opt) is the one at which a required peak capacity of gradient LC analysis is obtained in the shortest time. The balanced mixing program is a one where, for better separation of early eluting solutes, the mixing ramp is preceded by a balanced isocratic hold of the duration depending on Rϕ. The improvement in the separation of the earlier eluites due to the balanced programming has been evaluated. The value of Rϕ,Opt depends on the solvent composition range covered by the mixing ramp and on the column pressure conditions. The Rϕ,Opt for a column operating at maximum instrumental pressure is different from Rϕ,Opt for a column operating below the instrumental pressure limit. On the other hand, it has been shown that the difference in the Rϕ,Opt values under different conditions is not very large so that a single default Rϕ previously recommended for gradient analyses without the isocratic hold also yields a good approximation to the shortest analysis time for all conditions in the balanced analyses. With or without the initial balance isocratic hold, the recommended default Rϕ is about 5%/t0 (5% increase in the solvent strength per each t0-long increment in time) for small-molecule samples, and about an order of magnitude slower (0.5%/t0) for protein samples. A discussion illustrating the use of the optimization criteria employed here for the techniques other than LSS gradient LC is included.

Solubility of d-elements salts in organic and aqueous-organic solvents: IV. Solubility of cadmium chloride

Solubility of cadmium chloride at 25°C in four ternary systems containing mixed water-organic solvents was measured by the isothermal saturation method. Dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, and 1,4-dioxane were used as organic components. In all systems the organic component addition provides a salting-out effect within the whole range of the binary solvent compositions.

Understanding the enhanced solubility of 1,3-benzenedicarboxylic acid in polar binary solvents of (acetone + water) at various temperatures

Understanding solid dissolution in polar binary solvents showing maximum or minimum solubility phenomenon is essential for the design and operation of anti-solvent crystallization process. Solubilities of 1,3-benzenedicarboxylic acid in binary solvents of acetone with water are measured from 278.15 to 323.15K using the static equilibrium method, covering the entire range of solvent composition. The solubility always increases with increasing temperature, while, at fixed temperature, a maximum solubility is observed in mixed solvents of certain composition. The experimental temperature-dependent solubility data of 1,3-benzenedicarboxylic acid in cosolvents of different compositions are correlated using the Apelblat model with an average relative deviation (ARD) of 0.18%. Calculations of the derived thermodynamic functions show that the dissolution of 1,3-benzenedicarboxylic acid in the solvent mixtures is endothermic and mainly driven by the enthalpy change. The Simplified Modified Wilson (SMW) model is adopted to reproduce the isothermal solubility data over the entire acetone composition with an overall ARD of 1.41%, with which the maximum mole fraction solubility and the corresponding solvent composition at different temperatures are determined, and are subsequently used to estimate the solubility parameter of 1,3-benzenedicarboxylic acid.

Local structure and translational dynamics of NMF (N-methylformamide)–DMF (N,N-dimethylformamide) mixtures, via molecular dynamics simulation

In this work, the liquid amide mixture of N-methylformamide (NMF) with N,N-dimethylformamide (DMF) has been investigated by means of the molecular dynamics simulation method. The intermolecular structure and local mole fractions around any kind of the component molecules have been studied in terms of the calculated site-site correlation functions at three solvent compositions, XDMF, and ambient conditions. The hydrogen bonding network of the system has been extensively explored and the several hydrogen bond types formed between NMF-NMF, DMF-DMF and NMF-DMF in each mixture per molecule have been obtained with increasing XDMF. The results obtained reveal the notable effect of DMF molecules upon the formation of the hydrogen bonding network in each system. The investigated diffusion coefficients of both mixture components show clearly a linear increase of the diffusivity of all molecules while the DMF fraction increases. The intermolecular structure and hydrogen bonding properties studied validate the results from previous small angle neutron scattering studies on the system and support their conclusion that this amide mixture may be considered as an almost ideal one. Also, it may be concluded that DMF does not self-aggregate, because it acts as a hydrogen-bond breaker over the whole range of solvent composition. This finding is in accordance with the translational diffusive behavior of the molecules in the mixtures mentioned above. The detailed analysis of the hydrogen bonding network in DMF- rich and NMF-rich mixtures has revealed important information regarding the short range molecular aggregation in these diluted mixtures. This result is in general found to be comparable with corresponding predictions from previous experimental low-frequency raman spectroscopic studies of these mixtures.

Solubilities of Phthalic Acid and o-Toluic Acid in Binary Acetic Acid + Water and Acetic Acid + o-Xylene Solvent Mixtures

The solubilities of phthalic acid and o-toluic acid in binary acetic acid (HAc) + water and HAc + o-xylene solvent mixtures were measured by a dissolution temperature method at atmospheric pressure. The mole fractions of HAc in the corresponding solvent mixtures range from 0.00 to 1.00. The measured data show that, within the temperature range studied, the solubilities of phthalic acid and o-toluic acid increase with the increasing temperature at constant solvent composition and initially decrease with the decreasing mole fraction of HAc in HAc + o-xylene and HAc + water solvent mixtures at constant temperature, respectively. It also shows that, within the solvent composition range studied, the HAc + water solvent mixtures with the mole fraction of HAc at 0.5467 has the highest dissolving capacity for phthalic acid at constant temperature, and the highest solubility of o-toluic acid is obtained in HAc + o-xylene solvent mixtures with the mole fraction of HAc of 0.5408 at constant temperature. The experime...

Influence of aqueous dimethyl sulfoxide on pyridoxine protonation and tautomerization

The constants of pyridoxine (vitamin B6) protolytic and tautomeric equilibria were determined by means of potentiometry and spectrophotometry respectively in wide range of binary solvent (aqueous dimethyl sulfoxide) compositions. The free Gibbs energies of pyridoxine molecular and zwitterionic species transfer from water to aqueous DMSO were obtained using method of partition between immiscible phases. These results were employed for discussing the transmembrane transport capability of B6 vitamin. The influence of mixed solvent composition on pyridoxine protonation was analyzed taking into account the reagents solvation data.

Potentiometric, Thermodynamics and Coordination Properties for Binary and Mixed Ligand Complexes of Copper(II) with Imidazole-4-acetic Acid and Tryptophan or Phenylalanine Aromatic Amino Acids

Binary and ternary complex formation equilibria of copper(II) with imidazole-4-acetic acid (IMA) and some aromatic amino acids such as tryptophan and phenylalanine have been studied from 15 to 45 °C by potentiometric titration. The pH-titrations of the reaction mixtures have shown 1:1:1 (Cu:IMA:amino acid) ternary complex formation. The stability of mixed-ligand complexes was quantitatively compared with the stability of the binary complexes as Δlog10 K, Δlog10 β and log10 X parameters. The speciation of different species in solution has been evaluated as a function of pH. The effect of temperature on protonation of the ligands and formation of mixed ligand complexes was investigated. Thermodynamic parameters were calculated and are discussed. The effect of solvent of the protonation of IMA and Cu–IMA complex formation was also investigated and discussed. Additionally, the stoichiometric protonation constants (log10 β) of imidazole-4-acetic acid and its binary Cu(II)–IMA complexes were determined potentiometrically over a wide range of solvent composition.

Protolytic and tautomeric equilibria of pyridoxine in aqueous ethanol

The present work reports the constants of pyridoxine (vitamin B6) protolytic and tautomeric equilibria determined by means of potentiometry and spectrophotometry respectively in wide range of binary solvent (aqueous ethanol) compositions. The Gibbs energies of pyridoxine molecular and zwitterionic forms transfer from water to aqueous ethanol were obtained using method of partition between immiscible phases. The dependences of equilibrium processes constants on mixed solvent composition were analyzed taking into account the reagents solvation data. The transmembrane transport capability of B6 vitamin was discussed. The effect of binary solvent composition on pyridoxine reactivity towards nucleophilic substitution reactions including phosphorylation reaction was estimated by quantum chemical calculations.

Optimal Mixing Rate in Linear Solvent Strength Gradient Liquid Chromatography

The mixing rate (Rϕ) is the temporal rate of increase in the solvent strength in gradient LC. The optimal Rϕ (Rϕ,Opt) for a gradient analysis is the one at which a required separation capacity and peak capacity of the analysis are obtained in the shortest time. The Rϕ,Opt of LSS (linear solvent strength) gradient LC is found in dimensionless form (rϕ,Opt) expressing Rϕ,Opt in units of hold-up time (t0) and characteristic strength-constant (Φchar). Previously unknown effect of the gradient band compression on the peak capacity is taken into account. The rϕ,Opt depends on the solvent composition range covered by the mixing ramp and on the available pressure. A default rϕ at which the analysis time is contained within 30% margin of its minimum at rϕ,Opt for a broad range of conditions is proposed. As an example, the recommended default for small-molecule samples is 5% increase in the solvent strength per each t0-long increment in time. At this rate, approximately 0.2√N units of peak capacity are generated per each 10% solvent strength increment. The effect of a column kinetic optimization is also evaluated.

Ultrasonic Velocity and Compressibility Studies of Tetraalkylammonium Salts in Acetonitrile + Methanol Binary Mixtures at 298.15 K

Abstract The ultrasonic velocities (u) and densities (ρ) of tetraalkylammonium perchlorates (R4NClO4, where R = Methyl, Ethyl, Propyl or Butyl) and tetrabutylammonium tetraphenylborate (Bu4NPh4B) solutions have been measured at different salt concentrations in the range (30–500) × 10−4 mol kg –1 in binary mixtures of acetonitrile (AN) with methanol (MeOH) containing 0, 20, 40, 60, 80 and 100 mol % methanol at 298.15 K. The isentropic compressibilities (K s ) and apparent molal isentropic compressibilities (K s,φ ) of different salts in the solvent mixtures have been calculated. Limiting apparent molal isentropic compressibilities (K o s,φ ) for various salts have been evaluated and split into contributions of individual ions i.e., into (K o s,φ )± values. The variation of (K o s,φ )± values with solvent composition shows that Bu4N+ and Ph4B+ have very large positive (K o s,φ )± values which show strong solvophobic interactions in AN and in AN + MeOH mixtures over the entire solvent composition range. These positive values indicate some special type of interactions with the solvent molecules, which increase with the increase of MeOH composition. ClO4 – shows much weaker solvation in AN + MeOH mixtures by having some interaction with AN in the AN rich region of the mixtures. The negative values of Me4N+ and Et4N+ ions show strong structural effects which arise due to solute-solvent interactions in MeOH rich region of mixtures.

Reaction kinetics and solubility in water-organic binary solutions are governed by similar solvation equilibria

The solvation effects observed in water-organic solutions were studied by combining data for reaction kinetics and dissolution equilibria by means of a linear free-energy (similarity) analysis. Kinetic data for the pH-independent hydrolysis of (4-methoxyphenyl)-2,2-dichloroacetate measured in this work and solubility data for naphthalene, and other substrates of low polarity, in aqueous binary mixtures of methanol, ethanol, acetonitrile, dimethyl sulfoxide (DMSO), and 1,4-dioxane were used. Linear similarity relationships were discovered for these data over the full range of solvent compositions studied. To gain insight into the similarities observed between these different phenomena, molecular dynamics simulations were carried out for naphthalene and an ester in water–acetonitrile solutions. The results revealed considerable preferential solvation of these substrates by the co-solvent. Linear relationships between the experimental data and the mole fractions of acetonitrile in the solvation shells of substrates were found. Surprisingly, a linear relationship was found between the mole fractions of acetonitrile in the solvation shells of the ester and naphthalene. This linearity indicated that a similar solvation mechanism governs even such different phenomena as dissolution and reaction kinetics. The relationships between the experimental data and the results of the molecular dynamics calculations found in this work explained the solvent effect observed in water-organic solutions on the molecular level. Copyright © 2015 John Wiley & Sons, Ltd.

Excess volumes and excess heat capacities of {1,2-alkanediol + methanol} mixtures and ionic volumes in these systems

Densities of {1,2-propanediol+MeOH}, {1,2-butanediol+MeOH} and {1,2-pentanediol+MeOH} mixtures and densities of dilute solutions of three electrolytes (NaI, NaBPh4 and Ph4PI) in mentioned mixtures with exception the system containing 1,2-pentanediol were measured at T=298.15K. Isobaric specific heat capacities for {1,2-propanediol+MeOH} and {1,2-pentanediol+MeOH} mixtures were measured using a differential scanning calorimeter over the temperature range from (293 to 324) K. The excess molar volumes and excess molar isobaric heat capacities of binary systems were calculated and fitted by the Redlich–Kister polynomials. For ternary systems apparent molar volumes of electrolytes were determined at an electrolyte concentration of 0.025molkg−1 over the entire mixed solvent composition range. Single ionic apparent molar volumes of transfer, ΔtVφ (ion) were calculated using the tetraphenylphosphonium tetraphenylborate (TPTB) assumption. The influence of the carbon–chain length over the obtained functions was studied. The results were analyzed in terms of intermolecular association.

Acids, Bases, and Salts in Mixed-Aqueous Solvents

The dependence of the dissociation constants of acids and bases and their tendency to form salts upon solvent composition in mixed-aqueous solvents are reviewed, along with the activities of the solvent components. The acid–base equilibria are dominated by preferential solvation of the ions by water molecules in the mixtures, compounded by the very high water activities across most of the solvent composition range; the neutral components are normally preferentially solvated by the organic component of the solvent mixture. Neutral acids, such as carboxylic acids and phenols, show only modest increases in pKa (1–2 pK units) in solvent mixtures containing up to 60–70 wt % organic component; thereafter is a much steeper, solvent-dependent increase to the value in the pure organic solvent. Cationic acids, such as protonated amines, anilines, and pyridines, display a universal decrease in pKa (∼1 pK unit) up until around 80 wt % organic solvent, almost independent of the nature of the base or the solvent; beyon...

Micellization behavior of Aerosol OT in alcohol/water systems.

This paper examines the effects of solvent composition on the micellization behavior of the surfactant Aerosol OT (AOT). The critical micelle concentrations of AOT in the pure solvents methanol, ethanol, propanol, and isopropanol were measured using conductiometric techniques. These solvents were then mixed with water to create solvent spectra from pure alcohol to pure water in 12 increments. Critical micelle concentrations were measured at each solvent composition. Dynamic light scattering was used to verify the presence or absence of micelles in the solvent mixtures. It was found that inverse micelles exist over a range of solvent compositions where εeff < 48 with CMCs increasing with increasing solvent polarity. Micellization was found not to occur when 48 < εeff < 80. Regular micelles formed in pure water, with the measured CMC agreeing with the literature value of 2.25 mM.

Ionic molar volumes in methanol mixtures with acetonitrile, N,N-dimethylformamide and propylene carbonate at T = 298.15 K

The densities of dilute solutions of three electrolytes (NaI, NaBPh4 and Ph4PI) in methanol mixtures with propylene carbonate (PC), N,N-dimethylformamide (DMF) and acetonitrile (AN) have been measured by Anton Paar 5000 densimeter at T=298.15K. Apparent molar volumes, VΦ have been determined at an electrolyte concentration of 0.06mol·kg−1 over the entire mixed solvent composition range. Single ionic apparent molar volumes of transfer, ΔtVΦ (ion) were calculated using the tetraphenylphosphonium tetraphenylborate (TPTB) assumption. The results are discussed in terms of ionic preferential solvation.

Solvent effects in the arenesulfonylation of N-alkylanilines

The kinetics of arenesulfonylation of N-methyl- and N-ethylaniline with 3-nitro- and 4-methylbenzenesulfonyl chlorides in aqueous 1,4-dioxane have been studied. Comparison of the solvent effects on the reaction of N-alkylanilines with arenesulfonyl chlorides has revealed higher yields of the arenesulfonylation products (more than 90%) in water-1,4-dioxane mixtures over a wide range of solvent composition as compared to water-alcohol mixtures studied previously.