VOLUME 31, NO4, AUG 2009

Microencapsulation of Tramadol Hydrochloride and Physicochemical Evaluation of Formulations

The present project involves the microencapsulation of tramadol hydrochloride with ethocel using a non-solvent addition coacervation technique. The concentration of ethocel was varied to get a prolonged release profile. Then microparticles were compressed into tablets to study the variation of drug release between the microparticles and tablets. The microparticles were off white, aggregated and irregular in morphology having good percentage entrapment efficiency and percentage production yield. Dissolution study was made using USP XXIV apparatus I and II respectively, in 900 mL double distilled water at 50 rpm maintained at 37 °C. An Initial burst effect was noted in the drug release behavior. Polyisobutylene concentration affected inversely the rate of drug release from microparticles. Dissolution media and stirring speed affected insignificantly (p>.05) the release pattern. Tramadol hydrochloride tablets showed good stability and reproducibility. UV and FTIR spectroscopy and X-Ray diffractometry proved that tramadol hydrochloride was completely and uniformly distributed in ethocel with out any strong interaction. The mechanism of drug release was anomalous diffusion that was best fit to Higuchi’s equation. It can be concluded that multi-unit, slow-release tramadol hydrochloride microparticles can be formulated efficiently with non-solvent addition coacervation technique using ethocel.read more

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Mahmood Ahmad ,

Study of Color Parameters of Light Exposed and Light Unexposed Wool Fabrics Dyed With 1:1 Chromium (III) Based Complex Dyes

Derivatives of o-amino benzoic acid (anthranilic acid) were synthesized using 1-naphthol-3,6-disulfonic acid, 1-Naphthol-8 amino-3, 6-di-sulfonic acid; 1-naphthol-3-sulfonic acid, 6-methylamino-1-naphthol-3-sulfonic acid or 1-naphthol-3-sulfonic acid, 6-phenylamino-1-naphthol-3-sulfonic acid as a coupling component. These derivatives were used to synthesize chromium (III) complexes. After isolation, these complexes were applied on pure wool fabric by exhaust process to evaluate hue, wash fastness and light fastness properties. The complexes delivered a change in color equivalent to gray scale step 3/5 to 4/5 for wash fastness test. During the study of light fastness, it was monitored that the hue of dyed fabrics enhanced after exposing them to light.read more

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Naheed Kausar ,

Oxidation of Benzyl Alcohol in Liquid Phase Catalyzed by Oxides of Nickel

The oxidation of benzyl alcohol in liquid phase catalyzed by nano sized nickel hydroxide and nickel oxide using water and toluene as solvent was studied. Benzaldehyde and benzoic acid were identified as the reaction products in alkaline aqueous medium, but with the toluene as a solvent benzaldehyde was the only product. Influence of different reaction parameters (speed of agitation, reaction period, flow of molecular oxygen and temperature) on the reaction performance was studied. Temkin adsorption model was found to be the best fit to experimental data. The reaction was found to be heterogeneous in nature in which catalyst can easily be separated from the reaction mixture by centrifugation.read more

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Mohammad Ilyas ,

Effect of the Hydrophilic Block Length on the Surface-Active and Micellar Thermodynamic Properties of Oxyethylene-Oxybutylene Diblock Copolymers in Aqueous Solution

The effect of hydrophilic block length on the surface and micellar thermodynamic properties of aqueous solution of E40B8, E80B8 and E120B8 diblock copolymers, were studied by surface tension measurements over a wide concentration and temperature range; where E stands for an oxyethylene unit and B for an oxybutylene unit. Like conventional surfactants, two breaks (change in the slope) were observed in the surface tension vs logarithm of concentration curve for all the three copolymers. Surface tension measurements were used to estimate surface excess concentrations (Γm), area per molecule at air/water interface and thermodynamic parameters for adsorption of the pre-micellar region in the temperature range 20 to 50 ºC. Likewise the critical micelle concentration, CMC and thermodynamic parameters for micellization were also calculated for the post-micellar solutions at all temperatures. For comparison the thermodynamic parameters of adsorption and micellization are discussed in detail. The impact of varying E-block length and temperature on all calculated parameters are also discussed. This study shows the importance of hydrophobic-hydrophilic-balance (HHB) of copolymers on various surface and micellar properties.read more

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Muhammad Siddiq ,

Partially Cd2+ Ion-Exchanged Type-A Zeolites and Their Thermal Analysis

A series of partially exchanged Cd2+ A-zeolites (Cd0.86 A, Cd1.7 A, Cd2.46 A, Cd2.86 A, Cd3.25 A) were prepared by aqueous cation exchange technique from synthetic NaA-zeolite. The percentage of Cd2+ ions exchanged increased with decreasing the concentration of Cd2+ions and increasing temperature of the exchanging solution. This behaviour of Cd2+ ion exchange with concentration is attributed due to ‘volume effect,’ ‘salt imbibent’ and electroselectivity effect.’ The uptake of Cd2+ ions increased with rise in temperature indicated the process to be endothermic. Ion-exchange isotherms plotted at different temperatures showed the type ‘a’ isotherm i.e., the entering ion (Cd2+) indicated selectivity to the outgoing ions (Na+). The ion-exchange equilibrium data also followed the Freundlich and Langmuir adsorption isotherms. Thermogravimetric analysis (TGA) showed that the zeolitic water depends on the number of Na+ and Cd2+ ions per unit cell (p.u.c.) Thermal analysis curves showed that the minimum endothermic peak of dehydration slightly shifted towards higher temperature for CdA-zeolites indicated that water molecules are more strongly bonded to Cd2+ than Na+. Three exotherms were clearly observed within the temperature range 780-1000 °C, which are indicative of more than one reaction or crystallization of more phases. The differential thermal analysis (DTA) curves showed that dehydrated NaA zeolite retained its stability from 340 to 780 °C and CdNaA-zeolites from 330-380 °C to 800-820 °C, NaA amorphisized at 920°C  and CdNaA-zeolite, from 920 to above 1000 °C.read more

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Sher Akbar ,

FTIR Study of the Methylation of Phenol with Dimethyl Carbonate over KBr/SiO2

The O-Methylation of phenol with dimethyl carbonate (DMC) over KBr/SiO2 catalyst was carried out and the reaction mechanism was investigated by in-situ FTIR. It was found that phenol was deprotonated to generate phenolate at 100 ºC but DMC was found no activation even at elevated temperature except a little decompose at 200 ºC. As a result anisole was formed at 150 ºC. Methylation mechanism was proposed based on those, in which phenolate was generated firstly and then acted as an active phase to attack methyl carbon of DMC to yield anisole. The activation of DMC seemed to be not essential.read more

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Bing Chen ,

Kinetics of DeSOx Reaction on Copper and Cerium-based Sorbent-Catalysts

Kinetics of SO2 removal using a copper-based sorbent CuO/γ-Al2O3 and a cerium modified copper sorbent CuO-CeO2/γ-Al2O3 were measured on a TGA and their kinetics behaviors were simulated with a proposed empirical rate model (ERM). The purpose of cerium addition to the copper sorbent was to study the difference of sorbent's kinetics. The cerium modified copper sorbent showed a higher reaction rate on initial sulfation than the regular copper sorbent. Both sorbents however had similar calculated activation energy. The proposed ERM model appeared to describe the SO2 removal kinetics well in the temperature range 250-400 ºC.read more

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Jian Sun ,

Synthesis and Characterization of Co (II), Ni (II), Cd (II) and Cu (II) Complexes of Bis-Schiff Bases obtained from 1,8-Diaminonaphthalene

The present study deals with the preparation of Schiff base and its chelates with some transition metal ions Co (II), Ni (II), Cu (II) and Cd (II). The ligand was obtained by condensation of 1,8-diaminonaphthalene with salicylaldehyde. The ligand and its complexes have been characterized by elemental analyses, IR, 1H-NMR, UV-Vis. molar conductance and magnetic susceptibility. The analytical, spectral and magnetic data support the mononuclear formulations of these complexes with M/L 1:1. The Co (II) and Ni (II) complexes of ligand are proposed to be square-planar, while the Cu (II) and Cd (II) complexes are proposed to be tetrahedral.read more

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Nevin Turan ,

Low Frequency Vapour Phase Infrared Spectra of Metal Carbonyls. Derivatives of the type XMn(CO)5, (where X=Br, Cl, H, D, CH3, CD3, CF3,)

Many vibrations which occur in the far-infrared region of spectrum are similar to the types of vibrations found in other regions of the spectrum.  They fall in the far-infrared because the atomic masses are large and/or the forces resisting the deformation are small.  Most of the vibrations of metal carbonyls fall into this category and hence they give a good example of what can be expected.  A number of metal carbonyls e.g. BrMn(CO)5, ClMn(CO)5, HMn(CO)5, DMn(CO)5, CH3Mn(CO)5, CD3Mn(CO)5 and CF3Mn(CO)5, have been studied in the vapour phase for first time and it is now possible to discuss the general nature of the vibration in this region.  The metal-CO stretching frequencies are found between 350 and 475 cm-1.  The metal-C-O bending frequencies are more scattered and fall between 275 and 650 cm-1 depending in part upon the phase of motion. The OC-M-CO bending modes occur between 50 and 150 cm-1.  Other vibrations are founds in this region when one or more CO group are replaced by groups in which heavy atoms are attached to the metal. Factor which shifts the positions of the frequencies, such as mass or charge on the metal carbonyl moiety, will be discussed.read more

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Zaid Mahmood Zaid ,

Chemical Pollution Profile of Rehri Creek Area, Karachi (Sindh)

The present investigation focuses on environmental issues along Rehri Creek area, which is an imperative creek of economic importance. During the study, a total of 30 samples of wastewater (industrial waste, Cattle colony waste and domestic waste) and seawater (infront of Rehri Goth and Lat Basti) from five sites along Rehri Creek area were collected for physical (pH and TSS), chemical (BOD5, COD, salinity, phosphate, TKN, oil & grease and organic matter) and heavy metals (Cr, Cu, Pb, Ni, As and Zn) analysis. Results of the physicochemical analysis revealed that effluent from Cattle Colony (Site 4) is the major source of marine water pollution along Rehri Creek area as it has high levels of all parameter except pH. Other two important sources are industrial effluent (Site 1) and domestic sewer drains (Site 2). Except pH and oil and grease concentration at Site 2, the levels of all the parameters in industrial and domestic drains are not within permissible limit. Heavy metal analysis reveals that the concentration of heavy metals along the Creek is higher than previously estimated. The study showed that marine water quality of Rehri Creek is grossly contaminated with the industrial and cattle colony effluents, which are dumped into the sea without any treatment and would create an alarming situation in future. The continued accumulation of pollutant is also responsible for ecological imbalances and biodiversity losses in the area.read more

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Moazzam Ali Khan ,