Browsing by Author "K. Abd El-Rahman, Mohamed"

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Anions Selective Electrodes with Unusual Half Nernstian Response
(UNIV TEHRAN, FAC CHEMISTRY, CENTER EXCELLENCE ELECTROCHEMISTRY, 2014) M. Riad, Safa'a; R. Rezk, Mamdouh; I. Khattab, Fatma; K. Abd El-Rahman, Mohamed; M. Marzouk, Hoda
Selective poly (vinylchloride) membrane electrodes based on a quaternary ammonium compound, malachite green as a novel ion exchanger for anionic species were prepared. The developed membrane electrodes were used successfully for the quantification of sulphadimethoxine, iodide ions and thiocyante ions in their pure powdered forms, fish water and/or pharmaceutical formulation. Linear responses were obtained within a concentration range of 10-5-10-2 M for the three selected monovalent anionic species. The electrodes exhibited unusual half Nernstian slopes when the divalent cationic malachite green is used as a novel lipophilic ion exchanger in PVC based membranes for determination of monovalent anions. They have fast response times about 20 s, satisfactory reproducibility, and long life times.
A single novel PVC membrane for dual determination of sulphadimethoxine and malachite green in aquatic environment
(Elsevier, 2015) I. Khattab, Fatma; M Riad, Safa'a; R. Rezk, Mamdouh; K. Abd El-Rahman, Mohamed; M. Marzouk, Hoda
A novel ion-pair of a quaternary ammonium compound; malachite green (MG), and an anionic drug sulphadimethoxine sodium (SDM) was prepared. The developed ion pair was incorporated into poly (vinyl chloride)-based membrane sensors for the dual quantification of sulphadimethoxine (sensor 1) and malachite green (sensor 2) in aquatic environment. Linear responses of SDM and MG were obtained within a concentration range of 10−5–10−2 and 10−5–10−3 M, respectively. The slopes of −29.8 ± 0.31 and 35.5 ± 0.20 mV/decade were obtained over pH range of 6–8 and 4–8 using sensors 1 and 2, in order. The proposed sensors displayed useful analytical characteristics for determination of SDM in its pharmaceutical formulation and in aquatic environment with average recoveries of 100.92 ± 0.19 and 102.47 ± 4.63, respectively. The recovery of MG in aquatic environment was 101.32 ± 3.64.
Stability indicating spectrophotometric and spectrodensitometric methods for the determination of diatrizoate sodium in presence of its degradation product
(Elsevier, 2015) K. Abd El-Rahman, Mohamed; M. Riad, Safaa; A. Abdel Gawad, Sherif; M. Fawaz, Esraa; A. Shehata, Mostafa
Three sensitive, selective, and precise stability indicating methods for the determination of the X-ray contrast agent, diatrizoate sodium (DTA), in the presence of its acidic degradation product (highly cytotoxic 3,5 diamino metabolite) and in pharmaceutical formulation were developed and validated. The first method is a first derivative (D1) spectrophotometric one, which allows the determination of DTA in the presence of its degradate at 231.2 nm (corresponding to zero crossing of the degradate) over a concentration range of 2–24 lg/mL with mean percentage recovery 99.95 ± 0.97%. The second method is the first derivative of the ratio spectra (DD1) by measuring the peak amplitude at 227 nm over the same concentration range as D1 spectrophotometric method, with mean percentage recovery 99.99 ± 1.15%. The third method is a TLC-densitometric one, where DTA was separated from its degradate on silica gel plates using chloroform:methanol:ammonium hydroxide (20:10:2 by volume) as a developing system. This method depends on quantitative densitometric evaluation of thin layer chromatogram of DTA at 238 nm over a concentration range of 4–20 lg/spot, with mean percentage recovery 99.88 ± 0.89%. The selectivity of the proposed methods was tested using laboratory-prepared mixtures. The proposed methods have been successfully applied to the analysis of DTA in pharmaceutical dosage forms without interference from other dosage form additives. The results were statistically compared with the official US pharmacopeial method. No significant difference for either accuracy or precision was observed.