Solubility prediction of paracetamol in binary and ternary solvent mixtures using Jouyban-Acree model

The Jouyban-Acree model has been used to predict the solubility of paracetamol in water-ethanol-propylene glycol binary and ternary mixtures based on model constants computed using a minimum number of solubility data of the solute in water-ethanol, water-propylene glycol and ethanol-propylene glycol binary mixtures. Three data points from each binary solvent system and solubilities in neat solvents were used to calculate the binary interaction parameters of the model. Then the solubility at other binary solvent compositions as well as in a number of ternary solvents were predicted, and the mean percentage deviation (+/-S.D.) of predicted values from experimental solubilities was 7.4(+/-6.1)%.     

On the rate of complete convergence for weighted sums of NSD random variables and an application

In this paper, the complete convergence is established for the weighted sums of negatively superadditive-dependent random variables. As an application, the Marcinkiewicz-Zygmund strong law of large numbers for the random weighted average is also achieved, and a simulation study is done for the asymptotic behaviour of random weighting estimator.     

Dispersive solid-phase extraction of risperidone from plasma samples using graphene oxide aerogels and determination with liquid chromatography

A graphene oxide-based aerogel was synthesized and applied to the extraction and the determinations with the high-performance liquid chromatography-ultraviolet detector. After the characterization of the produced graphene-aerogel, it was utilized as a dispersive solid-phase extraction sorbent for risperidone extraction from plasma samples. Aerogels are materials with a large surface area-to-mass ratio and plenty of core with functional groups which can easily attach to the analytes to extract them to the second phase. The suggested method determined risperidone in plasma samples in the wide dynamic range from 20 ng/ml to 3 μg/ml. The limits of detection and quantification of the developed method were calculated as 2.4 and 8.2 ng/ml, respectively. As a novel feature, the developed method has no need to precipitate plasma proteins, improving the analytical performance of the analysis. Also, for the first time, the produced materials were utilized for the extraction of risperidone from the plasma samples. The obtained results revealed that the developed approach could be employed as an accurate method for the quantification of risperidone in real plasma samples.     

Br?nsted-acidic ionic liquid [HO3S(CH2)4MIM][HSO4] as efficient and reusable catalyst for one-pot synthesis of β-acetamido ketones

Abstract  

Efficient and convenient synthesis of β-acetamido ketones has been achieved by one-pot reaction of acetophenone, aryl aldehydes, acetyl chloride, and acetonitrile in the presence of 3-methyl-1-(4-sulfonylbutyl)imidazolium hydrogensulfate [HO₃S(CH₂)₄MIM][HSO₄], a Br?nsted-acidic ionic liquid, as a green and reusable catalyst in solvent-free media at room temperature. The catalyst could be recycled and reused without noticeable decrease in catalytic activity.     

Qualitative analysis of a class of Bianchi VI0 imperfect fluid cosmologies

A set of dimensionless equations of state is used to show that the Einstein field equations governing a class of Bianchi VI₀ imperfect fluid cosmologies reduce to a plane-autonomous system of equations. The qualitative behavior of the underlying cosmological models is obtained by investigating this plane-autonomous system.     

A Simple Stability Indicating CZE Method for the Analysis of Octreotide Acetate

A simple stability indicating capillary zone electrophoretic method was developed and validated for the analysis of octreotide acetate (OCT-Ac). The best separation was achieved by bare fused silica capillaries (50 μm i.d.; 65.5 cm total and 57.0 cm effective length), phosphate buffer (pH = 3.25; 50 mM), at 32.5 °C. The samples were injected using 50 mbar for 5 s and subjected to the applied voltage of 27.5 kV for separation. The detection was carried out using a PAD at a wavelength of 195 nm. For improving the repeatability of the method, l-histidine was applied as an internal standard. According to the validation results, the method was linear in the concentration range of 3.30–400 μg mL^?1 (correlation coefficient of 0.9996) with a limit of detection of 1.08 μg mL^?1 and a limit of quantification of 3.30 μg mL^?1; accuracy of the method was between 100.4 ± 0.2 and 101.1 ± 0.2 %; intra-assay precision was 0.5–2.6 % and intermediate precision was 1.3–3.2 %. The proposed method was successfully applied for the quantification of OCT-Ac in both a pharmaceutical formulation and force-degraded samples and for the detection and separation of degradation products; besides, the obtained results were used for the evaluation of the degradation kinetics of OCT-Ac under different stress conditions. So, it is concluded that the developed method could be employed as a simple, accurate and precise stability-indicating method in quality control laboratories to assess the quantity and stability of OCT-Ac pharmaceutical products.     

Synthesis of pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidines

Starting from 1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-ones, a synthesis pathway to the tricyclic pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidines is described. Reaction of 1,5-dihydro-4H-pyrazolo[3,4-d] pyrimidin-4-ones with phosphoryl chloride afforded the corresponding 4-chloro-1H-pyrazolo[3,4-d]pyrimidines. Treatment of these compounds with hydrazine hydrate at reflux temperature gave the hydrazino derivatives, which were subsequently cyclized to the titled compounds on heating with orthoesters in ethanol.     

四丁基铵钨多酸[TBA]2[W6O19]:无溶剂条件下通过不对称汉斯反应快速合成聚氢化喹啉的新型可重复使用的非均相催化剂（英文）

A novel, efficient, and environmentally friendly method for the synthesis of polyhydroquinoline derivatives by a one‐pot, four‐component unsymmetrical Hantzsch condensation of dimedone, aldehydes, ethyl acetoacetate, and ammonium acetate in the presence of a catalytic amount of tetrabutylammonium hexatungstate [TBA]2[W6O19] under solvent‐free conditions has been developed. The results showed that this heterogeneous catalyst has high catalytic activity and the desired products were obtained in good to high yields. Moreover, the catalyst was found to be reusable and considerable catalytic activity was still achieved after the fifth run.     

Solution thermodynamics and preferential solvation of hesperidin in aqueous cosolvent mixtures of ethanol,isopropanol, propylene glycol,and n-propanol

The solubility of hesperidin in some {cosolvent (1) + water (2)} mixtures expressed in mole fraction at temperatures from 293.15 K to 333.15 K reported by Xu et al. has been used to calculate the apparent thermodynamic functions, Gibbs energy, enthalpy, and entropy, of the dissolution processes by means of the van’t Hoff and Gibbs equations. Non-linear enthalpy–entropy relationships were observed for this drug in the plots of enthalpy vs. Gibbs energy of dissolution with positive or negative slopes regarding mixtures composition and/or cosolvent. Moreover, the preferential solvation of hesperidin by the cosolvents was analysed by using the inverse Kirkwood–Buff integrals observing that this drug is preferentially solvated by water in water-rich but preferentially solvated by cosolvents in mixtures 0.20 (or 0.24) ≤ x₁° ≤ 1.00. Furthermore, a new mathematical model was proposed for correlating/predicting the solubility of hesperidin in binary solvent mixtures at various temperatures.