Marwa A.A. Ragab

Bio: Marwa A.A. Ragab is an academic researcher from Alexandria University. The author has contributed to research in topics: Forced degradation & Derivative. The author has an hindex of 13, co-authored 53 publications receiving 462 citations.

Green chemistry: Analytical and chromatography

Abstract: Nowadays, the environment protection and the personal health and safety are given more consideration in the field of chemistry, thus resulting in an increased number of published researches about h...

Modeling the influence of limestone addition on cement hydration

Abstract: This paper addresses the influence of using Portland limestone cement “PLC” on cement hydration by characterization of its microstructure development. The European Standard EN 197-1:2011 and Egyptian specification ESS 4756-1/2009 permit the cement to contain up to 20% ground limestone. The computational tools assist in better understanding the influence of limestone additions on cement hydration and microstructure development to facilitate the acceptance of these more economical and ecological materials. μic model has been developed to enable the modeling of microstructural evolution of cementitious materials. In this research μic model is used to simulate both the influence of limestone as fine filler, providing additional surfaces for the nucleation and growth of hydration products. Limestone powder also reacts relatively slow with hydrating cement to form monocarboaluminate (AFmc) phase, similar to the mono-sulfoaluminate (AFm) phase formed in ordinary Portland cement. The model results reveal that limestone cement has accelerated cement hydration rate, previous experimental results and computer model “cemhyd3d” are used to validate this model.

Development and Validation of a High-Performance Thin-Layer Chromatographic Method for the Simultaneous Determination of Two Binary Mixtures Containing Ketorolac Tromethamine with Phenylephrine Hydrochloride and with Febuxostat

Abstract: A validated and highly selective high-performance thin-layer chromatography (HPTLC) method was developed for the determination of ketorolac tromethamine (KTC) with phenylephrine hydrochloride (PHE) (Mixture 1) and with febuxostat (FBX) (Mixture 2) in bulk drug and in combined dosage forms. The proposed method was based on HPTLC separation of the drugs followed by densitometric measurements of their spots at 273 and 320 nm for Mixtures 1 and 2, respectively. The separation was carried out on Merck HPTLC aluminum sheets of silica gel 60 F254 using chloroform-methanol-ammonia (7:3:0.1, v/v) and (7.5:2.5:0.1, v/v) as mobile phase for KTC/PHE and KTC/FBX mixtures, respectively. Linear regression lines were obtained over the concentration ranges 0.20-0.60 and 0.60-1.95 µg band(-1)for KTC and PHE (Mixture 1), respectively, and 0.10-1.00 and 0.25-2.50 µg band(-1) for KTC and FBX (Mixture 2), respectively, with correlation coefficients higher than 0.999. The method was successfully applied to the analysis of the two drugs in their synthetic mixtures and in their dosage forms. The mean percentage recoveries were in the range of 98-102%, and the RSD did not exceed 2%. The method was validated according to ICH guidelines and showed good performances in terms of linearity, sensitivity, precision, accuracy and stability.

Properties Of Concrete

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Ionic Liquids In Synthesis

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Short communication Spectrophotometric determination of alendronate in pharmaceutical formulations via complex formation with Fe(III) ions

Abstract: The formation of the complex between alendronate, non-chromophoric bisphosphonate drug important for the treatment of a variety of bone diseases, and iron(III) chloride in perchloric acid solution was studied. The stoichiometric ratio of alendronate to Fe(III) ions in the chromophoric complex was determined to be 1:1. The conditional stability constant was log Kave =4.50 (SD =0.15), indicating that the Fe(III)–alendronate complex is a complex of medium stability. The optimum conditions for this reaction were ascertained and a spectrophotometric method was developed for the determination of alendronate in the concentration range 8.1–162.5 gm l − 1 , the detection limit being 2 gm l − 1 . The method was validated for the direct determination of alendronate in tablet

Human versus Robots in the Discovery and Crystallization of Gigantic Polyoxometalates

Abstract: The discovery of new gigantic molecules formed by self-assembly and crystal growth is challenging as it combines two contingent events; first is the formation of a new molecule, and second its crystallization. Herein, we construct a workflow that can be followed manually or by a robot to probe the envelope of both events and employ it for a new polyoxometalate cluster, Na6[Mo120Ce6O366H12(H2O)78]⋅200 H2O (1) which has a trigonal-ring type architecture (yield 4.3 % based on Mo). Its synthesis and crystallization was probed using an active machine-learning algorithm developed by us to explore the crystallization space, the algorithm results were compared with those obtained by human experimenters. The algorithm-based search is able to cover ca. 9 times more crystallization space than a random search and ca. 6 times more than humans and increases the crystallization prediction accuracy to 82.4±0.7 % over 77.1±0.9 % from human experimenters.