Ibrahim S. Khattab

Density, viscosity, and surface tension of water+ethanol mixtures from 293 to 323K

Density, viscosity, and surface tension of liquids are important physicochemical properties which affect mass and heat transfer in solutions. The density, viscosity, and surface tension of binary mixture of water+ethanol at 293, 298, 303, 308, 313, 318, and 323 K are reported and compared with the available literature data. The findings of these comparisons show how the measured data are reproducible from different laboratories. The molar volume of water+ ethanol mixtures are also calculated using measured density values. The Jouyban-Acree model was used for mathematical correlation of the data. The relative deviation (RD) was used as an error criterion and the RD values for correlation of density, viscosity, surface tension and molar volume data at investigated temperatures are 0.1±0.1%, 10.4±9.5%, 4.2±3.6%, and 0.3±0.3%, respectively. The corresponding RDs for the predicted properties after training using the experimental data at 298 K are 0.2±0.2%, 14.1±15.8%, 5.4±4.6% and 0.4±0.3%, respectively, for density, viscosity, surface tension, and molar volume data. This study shows that the Jouyban-Acree model can correlate/predict physicochemical properties of the mixtures of solvents at different temperatures with acceptable error in calculation.

Physicochemical characterization of gliclazide–macrogol solid dispersion and tablets based on optimized dispersion

Background: This study investigated the physical interaction of gliclazide (GLC) with a hydrophilic carrier, that is, macrogol [polyethylene glycol (PEG)]. Different molecular weights of PEG (4000, 10,000, and 20,000) were used in different drug : carrier weight ratios (1 : 1, 1 : 2, 1 : 5, and 1 : 10). Method: Preliminary screening was done by phase solubility studies to characterize the liquid state interaction between the drug and the carrier. Solid dispersions (SDs) of GLC and PEG in different ratios were prepared by fusion technique and by physical mixing. The solid-state interaction between the drug and the carrier was examined by performing differential scanning calorimetry and Fourier transform infrared spectroscopic studies. SD with satisfactory characteristics was selected for the formulation of tablets by wet granulation method and compared with the commercial brand for in vitro dissolution. Results: It was evident from phase solubility studies that the drug solubility increased linearly with increasing PEG concentrations. In vitro dissolution of GLC improved significantly in the SDs prepared by fusion method as compared with the original drug and physical mixtures. Scanning electron microscopy images showed well-defined changes in the surface topography of GLC, thus confirming the effective formation of a fused binary system. The SD tablets showed a significant improvement in the drug release profile than that of the commercial brand. Conclusion: It was thus concluded that SD formulations of GLC can be successfully used to design a solid dosage form of the drug, which would have significant advantages over the current marketed tablets.

Viscosity and surface tension of glycerol + N-methyl-2-pyrrolidone mixtures from 293 to 323 K

The viscosity and surface tension of binary mixtures of glycerol (1) + N-methyl-2-pyrrolidone (2) at T = 293, 298, 303, 308, 313, 318, and 323 K and at atmospheric pressure are reported. The Jouyban–Acree model was used for mathematical correlation of measured data. The average percentage deviation was used as an accuracy criterion. Derived properties from measured thermophysical properties, including deviations in viscosity and surface tension; the enthalpy, entropy and Gibbs energy of flow activation; standard enthalpy and entropy of surface formation data were reported.

Development of Novel Formulations to Enhance in Vivo Transdermal Permeation of Tocopherol

Tocopherol represents a big challenge for transdermal permeation owing to its extreme hydrophobicity and large molecular mass. The aim of the present study was to develop alpha-tocopherol (T) topical formulations and evaluate their ex vivo and in vivo permeation. Franz diffusion cells were used for ex vivo permeation, and neonatal rats were used for in vivo permeation. Seven gel formulations and 21 liquid formulations were investigated for physical stability, viscosity and permeation of T. Analysis of T was performed by a validated HPLC method using a UV detector. The ex vivo permeation from gel and emulsion formulations was very poor (0.001-0.015 %). Highest permeation was observed from monophasic liquid formulations containing dimethyl sulfoxide (DMSO), tocopheryl polyethylene glycols (TPGs), propylene glycol, ethanol and 9.5 % T. The in vivo results demonstrated higher retention in the epidermis compared to subcutaneous tissues, 1377 and 1.13 μg g-1, respectively. Increasing T concentration from 4.8 to 9.5 % did not increase the amount permeated or % of T retained. It was concluded that simple solutions of T in the presence of DMSO and TPGs were more promising systems for effective transdermal permeation compared to gel, emulsion or oleaginous systems.

In vitro and in vivo Permeation of Vitamin E and Vitamin E Acetate from Cosmetic Formulations

Objective: To investigate the ability of α-tocopherol acetate (TA) and α-tocopherol (T), widely used ingredients in cosmetics, to cross the epidermal barrier using the neonatal rat as a model. Materials and Methods: The content of T and TA in four marketed products (A–D) and two experimental formulations (F1, F2) was investigated by HPLC. An in vitro permeation study was performed in neonatal rat epidermis using diffusion cells. In vivo permeation was studied in neonatal rats after repeated application of the products and analysis of T and TA in the stratum corneum/deeper skin layers. Results: Variable contents of TA were found in the marketed products (0.12–0.53%). No vitamin permeation was detected through the stratum corneum as in vitro biological barrier after 4 h. No detectable T and TA were seen in the in vivo permeation study in the epidermis. Variable degrees of drug penetration (4.3–12.6%) of the applied dose into the deeper skin layers were observed, depending on the formulation. In vivo application of TA-containing preparations did not result in any transformation of TA into T under the described experimental conditions. Conclusion: TA and T exhibited variable skin penetration and TA did not transform into T under the experimental conditions. The data underscored the need for further studies to optimize such formulations to improve vitamin E transdermal permeation and eventually achieve the expected cosmetic/therapeutic outcome.