An-Najah Staff

Objective: To study the dissolution behavior, the release mechanism and the stability of nanodispersion system of aglycones with PVP. Methods: The nanodispersion system of polyvinylpyrrolidone (PVP)/naringenin–hesperetin was prepared using the solvent evaporation method. The chemical stability (compatibility) of naringenin and hesperetin in the prepared dispersions was studied under accelerated conditions for 3 months. The evaluation of physical stability was performed by X-ray diffraction analysis (XRD) and by comparing the dissolution profile before and after storage at high temperature and moisture (40ºC, RH 75%). Results: The dissolution rate of naringenin and hesperetin released was dramatically increased in the nanodispersion system of PVP/naringenin–hesperetin (80/20, w/w). The release mechanism of both flavanone aglycones was better described by the diffusion model (Higuchi model). Also it was found that the rate-limiting step that controlled the release of naringenin and hesperetin in the nanodispersion system was dissolution of the carrier (PVP). Conclusions: During accelerated degradation analysis, for 3 months at high temperature and moisture, PVP nanodispersion system showed enhanced chemical compatibility and physical stability. The physical evaluation (obtained from XRD analysis) of PVP/naringenin–hesperetin (80/20, w/w) in the selected storage conditions did not show any crystallization of flavanone aglycones in the PVP nanodispersion system or any change in their release profile.

Tetra(-4-pyridyl)porphyrinatomanganese(III)sulfate (as an MnIII+MnII ion mixture) was embedded into a polysiloxane polymer matrix and attached to the surfaces of the n-GaAs electrode. The n-GaAs/polymer/MnP system was annealed under nitrogen and used for a photoelectrochemical study in a water/LiClO4/Fe(CN)6 3 −/Fe(CN)6 4− system. The values of short-circuit currents, measured after minutes of illumination, were significantly enhanced by modification. The modified electrode surfaces were more stable to degradation, in the dark and under illumination, than the unmodified ones. Furthermore, the modified electrodes showed higher light-to-electricity conversion efficiency than the unmodified ones. The methodology described here is advantageous in the sense that the semiconductor electrode properties can be enhanced in more than one aspect at the same time.

Diminazene aceturate and Antipyrine combination therapy is widely used in veterinary medicine. A simple reverse HPLC method for the analysis of samples of a ready injectable formulation containing a mixture of active ingredients and inactive excipients has been developed. The HPLC analysis was carried out using a reversed phase (RP)-C18 (250 mm×4.0 mm, 5 μm) column. The isocratic mobile phase consisted of a mixture of acetonitrile, methanol, phosphate buffer and hexane sulfonate; the flow rate was 0.6 mL/min and ultraviolet detection was at 291 nm. This method was validated in accordance with FDA and ICH guidelines and showed good linearity, accuracy, precision, selectivity and the system suitability results were within the acceptance criteria. A stability-indicating study was also carried out and indicated that this method could be used for purity and degradation evaluation of these formulations.

This study was aimed to develop valsartan/ hydrochlorothiazide tablet formulation and to develop a stability indicating HPLC method for their analysis in raw materials and in its final dosage form according to the ICH guidelines. Film coating tablets containing valsartan and hydrochlorothiazide were developed. A gradient HPLC method was performed; the flow rate was 1.5 ml/min, injected volume 20μL, the mobile phases consist of two solvent: Solvent A (0.20 M ammonium acetate, adjusted to pH 5.6 with glacial acetic acid) and Solvent B (acetonitrile) and UV detection was carried out at 265nm. Valsartan and hydrochlorothiazide and their combined dosage form were exposed to thermal, oxidative, acid-base hydrolytic stress conditions, the stressed samples were analyzed. The method was validated with respect to linearity, precision, accuracy, system suitability, and robustness. The used method is specific for the estimation of valsartan and hydrochlorothiazide in presence of their degradation products and impurities. The method was linear over the range of 2.5–32μg/mL and 17.5-224μg/mL for valsartan and hydrochlorothiazide respectively. The mean recoveries were 100±2% for valsartan and hydrochlorothiazide respectively. The percentage of relative standard deviation (%RSD) was found to be less than critical value. Our developed analytical method is a stability indicating, economical and easy method which is useful in the quality control of valsartan and hydrochlorothiazide in tablet dosage forms.

Different modification techniques, namely, preheating, controlling the cooling rate and modification with tetra(-4-pyridyl)porphyrinatomanganese(III) have been used to enhance photoelectrochemical characteristics of n-GaAs electrodes in light-to-electricity conversions. Combination of such three techniques together yielded electrodes with better darkcurrent density vs potential plots and photocurrent density vs potential plots. Higher efficiency and stability were also observed for electrodes modified by such combined techniques.

Tetra(-4-pyridyl)porphyrinatomanganese(III)sulfate (as an MnIII+MnII ion mixture) was embedded into a polysiloxane polymer matrix and attached to the surfaces of the n-GaAs electrode. The n-GaAs/polymer/MnP system was annealed under nitrogen and used for a photoelectrochemical study in a water/LiClO4/Fe(CN)6 3 −/Fe(CN)6 4− system. The values of short-circuit currents, measured after minutes of illumination, were significantly enhanced by modification. The modified electrode surfaces were more stable to degradation, in the dark and under illumination, than the unmodified ones. Furthermore, the modified electrodes showed higher light-to-electricity conversion efficiency than the unmodified ones. The methodology described here is advantageous in the sense that the semiconductor electrode properties can be enhanced in more than one aspect at the same time.

Dodecacarbonyltriruthenium(0), Ru3(CO)12, 1, has been chemically anchored to the aminated polysiloxane surface, 2. The resulting supported ruthenium complex, 3, was evaluated as catalyst for the olefin isomerization reactions. Contrary to its homogeneous catalyst counterpart, 1, the supported catalyst 3 showed exceptionally high selectivity towards 1-octene isomerization, and trans-2-octene was the sole product of the reaction mixture. The olefin isomerization reaction was markedly activated by the presence of the tertiary silane (EtO)3SiH. No hydrosilylation reaction products were detected. Preliminary kinetic study indicated catalysis by lower nuclearity catalytic species, where the cluster fragments during the reaction process. The effects of different reaction parameters on the rate of the reaction have been investigated.

Thin films of CdS, deposited by chemical bath deposition (CBD) onto films of fluorine-doped tin oxide/glass (glass/FTO) substrates were prepared and investigated for photoelectrochemical conversion (PEC) of light into electricity. Knowing the hazardous nature of CdS, the focal theme of this work was to modify the electrodes by simple economic ways to maximize their conversion efficiency and minimize their degradation under PEC conditions. This was to avoid leaching out of hazardous Cd²⁺ ions. Different parameters have been investigated for this purpose. Multi-deposition preparation, redox couple, and electrode etching affected electrode PEC characteristics. Consistent with earlier literature, annealing the electrode enhanced its conversion efficiency and stability. On the other hand, effect of cooling rate of pre-annealed CdS electrodes, prepared by CBD, on their PEC characteristics has been investigated here for the first time. Controlling the cooling rate was one major factor that affected CdS surface morphology, conversion efficiency and stability under PEC conditions. The major recommendation coming out here is that PEC characteristics of CdS thin film electrodes can be significantly enhanced by pre-annealing the electrode at ∼250 °C followed by its slow cooling.

Full Text

Thin films of CdS, deposited by chemical bath deposition (CBD) onto films of fluorine-doped tin oxide/glass (glass/FTO) substrates were prepared and investigated for photoelectrochemical conversion (PEC) of light into electricity. Knowing the hazardous nature of CdS, the focal theme of this work was to modify the electrodes by simple economic ways to maximize their conversion efficiency and minimize their degradation under PEC conditions. This was to avoid leaching out of hazardous Cd2+ ions. Different parameters have been investigated for this purpose. Multi-deposition preparation, redox couple, and electrode etching affected electrode PEC characteristics. Consistent with earlier literature, annealing the electrode enhanced its conversion efficiency and stability. On the other hand, effect of cooling rate of pre-annealed CdS electrodes, prepared by CBD, on their PEC characteristics has been investigated here for the first time. Controlling the cooling rate was one major factor that affected CdS surface morphology, conversion efficiency and stability under PEC conditions. The major recommendation coming out here is that PEC characteristics of CdS thin film electrodes can be significantly enhanced by pre-annealing the electrode at ∼250 °C followed by its slow cooling.