Journal of Solution Chemistry最新文献

The main purpose of this research was to evaluate the mass/volume percentage (%m/v) solubility of acetaminophen (ACP) in {ethanol (EtOH) (1) + propylene glycol (PG) (2) + water (3)} mixtures from 20.0 to 40.0 °C to expand the solubility database of this drug in mixed pharmaceutical solvents useful for designing high concentrated liquid products including injectable solutions. This is because ACP is an analgesic drug widely used available for oral administration as tablets or solutions. Besides, as injectable products, it is only available for perfusion in as 1 g in 100 mL (1.0%m/v). However, it is not available as 5 mL ampules for supplying doses of 500 mg. As demonstrated in this research some cosolvent mixtures allow ACP concentrations higher than 10.0%m/v, for instance the aqueous ternary mixture with 20% w/w of ethanol and 30% w/w of PG, among other possible mixtures. Flask shake method and UV–vis spectrophotometry were used for ACP solubility determinations at different temperatures. ACP solubility results are presented as Cartesian and triangular solubility profiles. ACP solubility increases with temperature arising and the cosolvent proportion in the mixtures. Maximum %m/v ACP solubility value is observed in the aqueous ethanol binary mixture of w₁ = 0.80 at all temperatures being 21.18% at 25.0 °C. All the solubility values were well correlated using the Jouyban-Acree model obtaining mean percentage deviations of 3.8% (N = 330). In this way, %m/v equilibrium solubility of ACP in {EtOH + PG + water} mixtures has been studied and correlated at several temperatures as contribution to preformulation studies of injectable homogeneous liquid pharmaceutical dosage forms.

The dynamic behaviour of a chemical system made of two coupled reactions is compared with that of a mechanical system consisting of two oscillating bodies connected by springs. First, the principle of energy departure from equilibrium is employed to derive the motion equations of both systems. Subsequently, the relevant characteristic frequencies and the amplitude parameters are obtained and analysed in terms of “Normal Modes”. The results show that systems belonging to different branches of science can be analysed using the same methodologies. To elucidate the application of Normal Modes to chemistry, the dynamic analysis of a system consisting of a proton transfer reaction coupled to a complex formation reaction is described in the Supporting Information: the procedure enables the evaluation of rate constants, equilibrium constants and reaction enthalpies of a reacting chemical system made of two coupled reactions. The method is then extended to a cycle of three reactions.

Thermal degradation of piperazine (PZ) in aqueous and mixed sulfolane (SFL) (30% by weight) + H₂O solution as a hybrid context was investigated as a function of temperature and two levels of piperazine concentrations and two levels of carbon dioxide loadings. Degradation of PZ in aqueous solution has been found to be first order. The pseudo rate constants for 5%wt solution of piperazine at 145, 160 and 175 °C in aqueous solution are 2.24 × 10^–9, 1.09 × 10^–8 and 2.27 × 10^–7 and in the hybrid media are 3.56 × 10^–8, 7.67 × 10^–8 and 1.19 × 10^–7 per second, respectively, and the activation energies for the aqueous and hybrid media were estimated 238.71 and 62.77 kJ/mole, respectively. Considering the most abundant degradation products identified; 3-(hydroxyethyl)-2-oxazolidone (HEOD), N,N-bis-(2-hydroxyethyl)-piperazine (BHEP), N,N’,N-tris-(hydroxyethyl) ethylenediamine (THEED), 1-[2-[(2-Aminoethyl) amino] ethyl] piperazine (AEAEPZ) and 1-Methylpiperazine (1-MPZ), the degradation pathway of PZ in both media is expected to proceed through ring opening of protonated PZ with the attack of other piperazine molecules on its alpha carbon. The presence of SFL only accelerates the reactions without changing the degradation mechanism.

The local structure and molecular interactions of Li⁺ salt in aqueous solutions is important in many fields. However, whether solvent shared ion pairs and the direct contact ion pairs exist in aqueous LiCl solutions or not, and the details about these ion pairs are still under debate. Here, we proposed a novel IR ratio method. Using this method, the hydration spectra of Cl⁻ in LiCl, NaCl, and KCl aqueous solutions were measured from the diluted concentration to the highly concentrated solution. Hydration number of Cl⁻ from the hydration spectra was determined to be ~ 2 in the aqueous LiCl. These data demonstrated that about 3–4 Li⁺ replaced some water molecules in the first hydration shell of Cl⁻. As the concentration of LiCl increased, an abnormal increase in the hydration number was observed. This is because the water molecule that bridges Li⁺ and Cl⁻ in the solvent-shared ion pair are particularly stable, which was directly proven by the red shift of the hydration spectra of Cl⁻ in the O–H stretching region. All the hydration spectra and hydration numbers not only applied to uncover the solvent shared ion pairs and direct contacted ion pairs in LiCl aqueous solution, but also can be employed to the benchmark of force fields in the classical molecular dynamics simulations.

Study of some physicochemical properties of l-aspartic aid in water and aqueous ammonium acetate has been undertaken for this investigation. Density, viscosity and conductivity of the solutions were measured at different temperatures. Volumetric parameters such as apparent molar volume (({V}_{Phi })), partial molar volume (({V}_{Phi }^{0})), partial molar expansibility (({E}_{Phi }^{0})) and Hepler’s constant (({{partial }^{2}{V}_{Phi }^{0}/{partial T}^{2})}_{{p}})) and viscometric parameters such as relative viscosity({(eta }_{r })), viscosity coefficients ({(B}_{J }mathrm,{text{and} },{ A}_{F})), Gibbs free energy of activation of viscous flow of solvent and solute ({(Delta mu }_{1}^{#,0}mathrm,text{ and },{Delta mu }_{2}^{#,0})) respectively) and corresponding change in enthalpy ({Delta H}_{2}^{#,0}) and entropy ({Delta S}_{2}^{#,0}) have been derived from the experimentally measured density and viscosity values. Variation of these parameters with concentration and temperature was analysed in the light of ion–ion and ion–hydrophilic interactions. The possibility of ion pair formation and its effect on migration of charged particles in solution have been determined by analysing the molar conductance (Λ_m), association constant ({(K}_text{A})), Walden product and thermodynamic functions. These parameters were qualitatively correlated with changes in structure of water that occurs when l-Aspartic acid interacts with ammonium acetate in aqueous media.

Levulinic acid is a promising building block chemical with various applications, such as in pharmaceuticals and cosmetics. The key parameters used for assessing the environmental fate, risk assessment and toxicity of a compound in these applications include partition and distribution behavior of the compound. The partition and distribution coefficients can be measured from the ratio of the compound concentration in 1-octanol to the concentration in water at equilibrium. In this study, the distribution and partition behavior of levulinic acid in octanol-water system were determined experimentally using a simple and inexpensive shake flask approach according to OECD 107 via UV–Vis spectroscopy at 298.15 K. The neat and mutually saturated solvents were applied in the determination of distribution and partition behavior. The distribution coefficient (log D) using neat solvents (octanol-water) and saturated solvents (octanol_{(water−saturated)}-water_{(octanol−saturated)}) were determined, and the partition coefficient (log P) was calculated accordingly based on the relationship between log D and log P for weakly acidic compounds. In octanol-water and octanol_{(water−saturated)}-water_{(octanol−saturated)} system, the log D of levulinic acid were determined to be − 0.574 and − 0.816, while the log P were − 0.554 and − 0.790, respectively. The precision of the method was established with variation in the measurement less than 0.03 for both log D and log P. The negative value of log P indicates the preference of levulinic acid for the water phase over the octanol phase. The results from this study can be comprehended in product formulation and design related to levulinic acid as well as assessing the environmental fate.

Potentiometric and calorimetric study on mixed-ligand complexes of nickel(II) ion with histidine (His) and cysteine (Cys) has been carried out in aqueous solution at 298 K and the ionic strength of I = 0.5 mol·dm⁻³ (KNO₃). Possible coordination modes of amino acid residues in ternary complexes are discussed using comparative analysis of thermodynamic parameters of complex formation.

The equilibrium molar solubility of 2-hydroxybenzoic acid (salicylic acid, SA) in pseudo-binary mixed solvents of choline chloride/propylene glycol deep eutectic solvent (ChCl/PG DES, 1:3 molar ratio) and water was determined by a shake flask method at 293.15-313.15 K and ambient pressure (85 kPa). Based on the results, the maximum solubility of SA was observed in neat DES at 313.15 K (0.7604 mol·L⁻¹) whereas it was minimum in neat water at 293.15 K (0.0112 mol·L⁻¹). X-Ray power diffraction analysis of solid phase presented no polymorphic transformation or solvate formation in the experiments. Moreover, the molar solubility of SA was modeled mathematically with various cosolvency models attaining the average percentage deviations smaller than 6.1%, except for the modified Wilson-van’t Hoff (12.6%). Further, more favorable and entropy-driven of SA dissolution in ChCl/PG DES-rich mixtures was achieved from the apparent thermodynamic analysis.

This work presents the application of L-tartaric acid (L-TA), ascorbic acid (AA), and L-carnitine (L-CAR) as a safe and non-toxic alternative agent to enhance the aqueous solubility of baclofen (BAC). The solvent evaporation method was employed for co-crystallization in three stoichiometric ratios of the drug, coformer (1:1, 1:3, 1:5) and formulations were confirmed by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FT-IR). DSC study revealed the presence of both endothermic and exothermic peaks in compounds containing AA and L-TA. With respect to the BAC, L-TA and BAC, AA, the appearance of new diffraction peaks that do not overlap with un-processed BAC may be the implication of a new structure. The intensity of some diffraction peaks disappeared or reduced significantly which may also imply the formation of a new crystal phase. The solubility of the multicomponents increased and surpassed the solubility of BAC. Overall, the new compounds show significantly higher drug solubility whereas their physical mixtures only demonstrate a marginal increase in BAC solubility. The high solubility records of BAC, AA and BAC, L-TA evidence the marked difference in solubility of the new compounds with respect to their physical mixtures. The saturation solubility of BAC, L-CAR compound did not show any improvement relative to the un-processed BAC. These findings confirm that a new crystal phase may not have been obtained during the co-crystallization of BAC and L-CAR.

The underground brines in the Sichuan Basin of China are rich in lithium, potassium, strontium, chlorine, etc. In order to fully develop and utilize these brine resources, it is necessary to carry out phase equilibrium research about the quaternary system LiCl–KCl–SrCl₂–H₂O and develop a reasonable lithium extraction process. The quaternary system LiCl–KCl–SrCl₂–H₂O at 273.2 K were determined using the isothermal dissolution equilibrium method. As a result, the corresponding phase diagrams were drawn based on the data. The phase diagram shows that the quaternary system LiCl–KCl–SrCl₂–H₂O has no double salt or solid solution at 273.2 K and there are two invariant points, five univariate curves and four solid phase crystallization fields, which are LiCl·2H₂O, SrCl₂·2H₂O, SrCl₂·6H₂O and KCl. Furthermore, Pitzer’s model was used to predict the solubility of salts in the quaternary system. The calculated values are in good agreement with the experimental ones. Finally, combined with isothermal evaporation method and the phase diagram of the quaternary system, a brine evaporation process was designed.