Browsing by Author "R. Rezk, Mamdouh"

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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.
Comparative Study of Different Chromatographic Techniques for the Analysis of Multi-Residues of Some Approved Antimicrobials in Fish Tissues
(Oxford University Press, 2015) M. Riad, Safa'a; R. Rezk, Mamdouh; I. Khattab, Fatma; M. Marzouk, Hoda
Two chromatographic methods were developed, optimized and validated for the simultaneous determination of three approved aquaculture antimicrobials, namely sulphadimethoxine sodium, trimethoprim and florphenicol in fish tissues. The developed methods were based on simple liquid extraction technique. The first method employs thin-layer chromatography as a clean-up procedure coupled with densitometric determination for the separated drugs. The second method is an HPLC one using X-Terra™ C18 column. Several mobile-phase systems and extracting solvents were tried to optimize the separation and the extraction procedures from fish tissues. The procedures were applied for the analysis of spiked fish tissue samples at three different concentration levels (10, 50 and 100 ppm). A comparative study was conducted between the proposed methods to discuss the advantage of each one. The methods were validated according to the international conference on harmonization guidelines. The proposed methods were successfully applied for the determination of the studied drugs in spiked fish tissues, pure powders and in their veterinary pharmaceutical formulation.
Electrochemical determination of ciprofloxacin hydrochloride in pharmaceutical formulation, aquatic environ-ment and in fish tissues
(Int. J. Biol. Pharm. Res, 2013) R. Rezk, Mamdouh; M. Riad, Safaa; I. Khattab, Fatma; M. Marzouk, Hoda
Two ciprofloxacin hydrochloride (CPX) selective electrodes were developed using dioctyl phthalate (DOP) as a plasticizer in a polymeric matrix of polyvinyl chloride (PVC). Sensor I was fabricated using tetrakis(4-chlorophenyl)borate (TpClPB) as an anionic exchanger without incorporation of an ionophore. Sensor II was developed using 2-hydroxy propyl β-cyclodextrin as an ionophore. Linear responses of CPX within a concentration range of 10-5-10-2 M, with slopes of 51.7 ± 0.31 and 48.7 ± 0.40 mV/ decade over pH range of 4-7 were obtained using sensors I and II, respectively. The selectivity coefficients of the developed sensors indicated excellent selectivity for CPX. The proposed method displayed useful analytical characteristics for determination of ciprofloxacin hydrochloride in pharmaceutical formulation , fish water and fish tissues with average recoveries of 100.91 ± 0.47, 96.42 ± 1.34 and 86.46 ± 1.28 , respectively for sensor I and 101.2 ± 0.37 , 97.26± 1.56 and 86.67± 1.70 , respectively for sensor II.
Simultaneous determination of metronidazole and diiodohydroxyquine in bulk powder and paramibe compound tablets by TLC-densitometry and HPLC
(Pharmaceut Anal Acta, 2012) Salem, Hesham; M. Riad, Safaa; R. Rezk, Mamdouh; Ahmed, Kholoud
Two sensitive and precise chromatographic methods were developed and validated for simultaneous determination of metronidazole (MTR) and diiodohydroxyquin (DIQ) in pharmaceutical preparation. The techniques adopted for quantification are coupled TLC-densitometry and HPLC. A mixture of chloroform, toluene, ethanol and acetic acid (9:9:1:1, v/v/v/v) was used as the developing solvent for TLC-densitometry. A mixture of methanol and acetonitrile, (96:4, v/v) was used as a mobile phase for HPLC at 0.6 mL min-1 flow rate and UV detection at 254 nm. Linearity was obtained in concentration range of 0.5-10 µg spot-1 for DIQ and 1-20 µg spot-1 for MTR applying TLC-densitometry and 0.005-0.5 mg mL-1 for DIQ and 0.01-0.5 mg mL-1 for MTR applying HPLC. The selectivity of the proposed methods was checked using laboratory prepared mixtures. The proposed methods were successfully applied to the analysis of MTR and DIQ in their mixture and in pharmaceutical dosage forms without interference from other additives.
Simultaneous determination of pioglitazone and glimepiride in their pharmaceutical formulations
(Scholars Research Library, Der Pharma Chemica, 2011) R. Rezk, Mamdouh; M. Riad, Safa'a; Y. Mahmoud, Ghada; El Bayoumi Abdel Aleem, Abdel-Aziz
Two sensitive and precise methods were developed and validated for the simultaneous determination of pioglitazone hydrochloride and glimepiride as the bulk drugs and in their pharmaceutical formulations. Among the techniques adopted were chromatography [coupled TLC-densitometry and HPLC].Method I : Densitometric separation of the drugs was performed on aluminum plates precoated with silica gel 60 F254 as the stationary phase and the solvent system consisted of chloroform: toluene: glacial acetic acid: ethanol [4.5:4.5:1:1, v/v/v/v]. Densitometric evaluation of the separated zones was performed at 228 nm and 268 nm. The two drugs were satisfactorily resolved with RF values 0.4and 0.65 for pioglitazone hydrochloride and glimepiride, respectively. The accuracy and reliability of the method was assessed by evaluation of linearity 3-15µg/spot for pioglitazone hydrochloride and 0.1-3 µg/spot for glimepiride, precision (intra-day RSD 1.178% and inter-day RSD 1.152 % for pioglitazone hydrochloride, and intra-day RSD 1.101 % and inter-day RSD 0.999 % for glimepiride), accuracy (99.94 ± 1.30 % for pioglitazone hydrochloride and 100.74 ±1.58 % for glimepiride) and specificity, in accordance with ICH guidelines. Method II: chromatographic separation using a 250 mm x 4.6 mm, i.d. C18Lichrosorb™ 10µm analytical column. The mobile phase consisted of phosphate buffer [pH: 4]: methanol: acetonitrile: triethylamine [40:20:40:0.1, v/v/v/v] The average retention times under the conditions described were 4 minutes for pioglitazone hydrochloride and 7.5 minutes for Glimepiride, accuracy and reliability of the method was assessed by evaluation of linearity 5-175 µg/mL for pioglitazone hydrochloride and 5-30µg/mL for Glimepiride, precision (intra-day RSD 0.295% and inter-day RSD 0.215 % for pioglitazone hydrochloride, and intra-day RSD 0.345 % and inter-day RSD 0.231 % for glimepiride), accuracy (99.80 ± 1.16 % for pioglitazone hydrochloride and 99.47 ±2.07 % for glimepiride) and specificity, in accordance with ICH guidelines.
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.
Spectrophotometric determination of sitagliptin and metformin in their pharmaceutical formulation
(Pharmacie Globale, 2012) M. Riad, Safaa; R. Rezk, Mamdouh; Y. Mahmoud, Ghada; El Bayoumi Abdel Aleem, Abdel-Aziz
Two simple, accurate and precise spectrophotometric methods were developed and validated for the determination of sitagliptin phosphate monohydrate (STA) and metformin hydrochloride (MTF). The first method was based on measuring the absorbance of STA at 268 nm in the range of 25-500 µg mL-1. The second method was the isosbestic point method. The total mixture concentration was calculated by measuring the absorbance at 257 nm. The proposed methods used to determine each drug in binary mixture. The results were statistically compared using one-way analysis of variance (ANOVA). The developed methods were satisfactory applied to the analysis of the pharmaceutical formulation and proved to be selective and accurate for the quality control of the cited drugs in their pharmaceutical formulation.