Mohammad Al-haj Ali

AN ENVIRONMENTALLY BENIGN APPROACH FOR RAPID ANALYSIS OF INDOMETHACIN USING A STABILITY-INDICATING RP-HPLC METHOD

A green RP-HPLC method for analysis of indomethacin (IND) in bulk drug, nanoemulsions, and various marketed formulations was developed and validated in the present investigation. The chromatographic identification was achieved on a Lichrosphere 250 × 4.0 mm RP C8 column having a 5-µm packing as a stationary phase using a green solvent ethyl acetate (100% v/v) as a mobile phase, at a flow rate of 1.0 mL/min with UV detection at 318 nm. The proposed method was validated for linearity, selectivity, accuracy, precision, robustness, sensitivity, and specificity. The utility of the method was verified by assay of IND in developed nanoemulsion, marketed tablet, capsule, suppository, and injection. The proposed method was found to be selective, precise, accurate, robust, sensitive, and specific. The amount of IND in developed nanoemulsion and all marketed formulations ranged from 98.34–101.40%. The proposed method successfully resolved IND peak in the presence of its degradation products which indicates the stability-indicating property of the proposed method. These results indicate that the proposed method can be successfully employed for routine analysis of IND in bulk drug and pharmaceutical dosage forms.

Effect of monomer feed and production rate on the control of molecular weight distribution of polyethylene in gas phase reactors

Abstract The control of the polymer molecular weight distribution via altering the monomer to hydrogen molar ratio in fluidized bed reactors is examined. The molar ratio is altered by manipulating the monomer and hydrogen feed rates using nonlinear model predictive controller. The simulation revealed promising results however a trade-off between utilizing both the monomer and hydrogen flows simultaneously and the hydrogen flow exclusively exists. Utilization of the monomer and hydrogen flows together favors the rapid transition to the required MWD but at the expense of higher purge and inconsistent production rate. Exclusive use of the hydrogen intake leads to steady production rate and less consumption of the purge. However, longer time is needed to achieve the desired MWD. The same phenomena are observed when discrete mechanism for product withdrawal is implemented.

Estimation of Swertiamarin in Enicostemma Littorale and Marketed Formulations Using HPLC-UV Method

A simple, economic, reproducible, robust and precis e HPLC method for estimation of swertiamarin in both 60 % methanolic extract of Enicostemma littorale and mar- keted formulations was developed and validated in p resent investigation. The mobile phase composed of methano l and water (90:10 % v/v), gave a sharp and well-defi ned peak of swertiamarin at the retention time of 10.15 ± 1.52 min. The limit of detection (LOD) and limit of quan tifica- tion (LOQ) were 17.25 and 56.92 μ g/ml respectively. The proposed method with high degree of precision and a ccu- racy was employed for the estimation of swertiamari n in methanolic extract and in marketed formulation.

Broadening the polyethylene molecular weight distribution by controlling the hydrogen concentration and catalyst feed rates

This paper discusses the control of an industrial gas-phase polyethylene reactor to produce a desired molecular weight distribution (MWD) of the polymer. The controller objective is to regulate online the entire molecular weight distribution by either manipulating the hydrogen content inside the reactor or coordinating the feed rates of two different types of catalysts. In this work, the molecular weight distribution is modeled as a function of the reaction kinetics and hydrogen to monomer ratio. Nonlinear model predictive controller (NLMPC) algorithm is used to maintain the desired molecular weight distribution online. The closed-loop simulations indicated the effectiveness of NLMPC to achieve its goal even in the presence of modeling errors. Moreover, the results showed that, altering the hydrogen concentration solely can produce the required polymer quality provided that an efficient mechanism is available to readily alter the hydrogen composition. Alternatively, the desired MWD can also be guaranteed with proper manipulation of the catalyst feed rates while the other process inputs are kept constant.

Different factors affecting the mechanical and thermo-mechanical properties of HDPE reinforced with micro-CaCO3:

In this study, we manufactured the HDPE/micro-calcium carbonate (CaCO3) composites. A twin screw extruder was used to melt blend different loadings of CaCO3 masterbatch, from 5% to 20%, with HDPE. Furthermore, injection-molded samples were manufactured using different molding conditions, namely pressure and cooling time. The presence of CaCO3 increased the viscosity and the stiffness of the composites. The viscoelastic analysis indicated that adding more than 15% on the CaCO3 masterbatch apparently affected the way the material behaves, as indicated by an abrupt change of some properties of the composite containing 20% masterbatch. As the molding pressure and cooling time increased, the shrinkage of the molded samples decreased. The tensile strength and the ductility of the composite decreased as the content of the CaCO3 increased and as the cooling time or the molding pressure decreased. The fracture surface of all samples had the characteristic dimples of polyethylene fracture; however, neat resin showed extensive fibrillation which was absent at high loadings of CaCO3.

Estimation of the Polymerization Rate of Liquid Propylene Using Adiabatic Reaction Calorimetry and Reaction Dilatometry

The use of pressure-drop and constant-pressure dilatometry for obtaining rate data for liquid propylene polymerization in filled batch reactors was examined. The first method uses reaction temperature and pressure as well as the compressibility of the reactor contents to calculate the polymerization rate; in the second, the polymerization rate is calculated from the monomer feed rate to the reactor. Estimated polymerization rates compare well to those obtained using the well-developed isoperibolic calorimetry technique, besides pressure-drop dilatometry provides more kinetic information during the initial stages of the polymerization than the other methods.

Controlling the Polyethylene Molecular Weight Distribution Using Hydrogen Influent

This paper addresses the feasibility of controlling the entire molecular weight distribution of the produced polymer in gas-phase ethylene polymerization reactors. Nonlinear model predictive controller is used to attain the control objective by utilizing the hydrogen feed rate as the only manipulated variable. The use of other manipulated variables is limited to avoid disturbing the process when influential inputs such catalyst and/or monomer inflows are used. The simulation results indicated successful implementation of the control algorithm to achieve the desired molecular weight distribution. The success depends on the improved hydrogen activities inside the reactor through a modified catalyst that is responsive to hydrogen variation and a wider admissible range of hydrogen feed rates.© 2010 ASME