Browsing by Author "M. Riad, Safa'a"

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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.
Conductomtric Determination of Torasemide in Bulk Drug, in Formulations and in Plasma
(UNIV TEHRAN, FAC CHEMISTRY, CENTER EXCELLENCE ELECTROCHEMISTRY, 2013) M. Riad, Safa'a
Two simple and sensitive conductometric procedures were investigated for the determination of torasemide (TOS) using potasium tetraphenyl borate (K TPB) and ammonium reineckate (Amm. RNC) were described. Optimized conditions including temperature, solvent and reagent concentration were studied. The suggested methods were used for conductometric determination of (TOS) in its pharmaceutical preparations. Precision, measured as relative standard deviation was less than 1% and accuracy was 99.76%.The obtained results were comparable with data using the reported method. The proposed procedures were successfully adapted for the determination of (TOS) in plasma. For comparison, some interference was also determined by the condutometric titrations. At equimolar concentration levels, some molecules of similar structure interfere with the original drug. A reduction in interferent concentration by a factor of 10 negated the interference.
Ion selective electrodes for potentiometric determination of baclofen in pharmaceutical preparations‏
(Analytical & Bioanalytical Electrochemistry, 2013) M. Riad, Safa'a; M. Mostafa, Nadia
Two different sets of baclofen sensors were developed for its potentiometric determination in pharmaceutical preparations, based on the fact that baclofen behaves as cation in acidic medium and anion in basic medium (pK1=9.62 and pK2=3.87;respectively). Six baclofen- selective electrodes were investigated using precipitation based technique with either sodium tetraphenyl borate as an anionic exchanger or 1, 10-ortho-phenanthrolineferrous as a cationic exchanger; respectively upon using polyvinyl chloride (PVC) matrix and dioctylsebacate (DOS) as a plasticizer. The resultant sensors have different forms, either as membrane electrodes (sensors I&IV), coated wire electrodes (sensors II&V) or as microsized graphite electrodes (sensors III&VI). Linear responses of 10-6–10-2 M with slopes of 43.05, 43.11, and 43.05 mv/decade within pH range 4-6 were obtained for sensors I, II and III. On The other hand, Linear responses of 10-7–10-3 M with slopes of 55.90, 57.13 and 57.37 mV/decade within pH 6-8 range were obtained for sensors IV, V and VI; respectively.All these sensors were prepared and fully characterized in terms of composition, life span, usable pH range, response time and temperature. The sensors show good selectivity to the drug in presence of a variety of inorganic and organic interferent substances. The proposed procedures were compared to the USP pharmacopoeial method and showed no significant difference. The proposed sensors displayed useful analytical characteristics for the potentiometric determination of baclofen in pure form and in pharmaceutical preparations.
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.
Stability-indicating methods for the determination of lidocaine and prilocaine in presence of their degradation products
(Bulletin of the Faculty of Pharmacy (Cairo University), 2008) M. Riad, Safa'a; O. Mohamed, Afaf; Abdul-Azim Mohammad, M.
Four simple, selective and accurate methods were adopted for the quantitative determination of lidocaine (L) and prilocaine (P) in presence of their major degradation products. In the first method, the second (D2) derivative spectrophotometry at 290 nm was used for the determination of lidocaine in presence of its degradation product 2,6-dimethylaniline over concentration range of 2.5-15 µg.ml-1 with mean percentage recovery 99.98±0.96. The second method based on the use of first (D1) and third (D3) derivative specrophotometry at 240 and 251 nm for the determination of prilocaine in presence of its degradation product o-toludine over concentration range of 2.5-15 µg.ml-1 with mean percentage recoveries 99.95±0.40 and 99.87±0.31, respectively. The third method was adopted depending on the application of ratio-specra 1st derivative (1DD) specrophotometry for the simultaneous determination of lidocaine and prilocaine. Lidocaine was determined at 270 and 277 nm over concentration range of 2.5-15 µg.ml-1 with mean percentage recoveries 100.18±0.43 and 100.32±0.35 whereas, prilocaine was determined at 259 and 268 nm over concentration range of 2.5-15 µg.ml-1 with mean percentage recoveries 100.28±0.25 and 100.24±0.21. The fourth method was a spectrodensitometric analysis, which provides the quantitative densitometric evaluation of thin layer chromatograms of lidocaine and prilocaine. They were determied at 220 nm and 237 nm over concentration ranges of 3-15 µg / spot and 0.4-10 and µg / spot with mean percentage recoveries 99.57±0.53 and 99.97±0.76 for lidocaine and prilocaine, respectively. The HPTLC plates were developed in methanol: n-butanol: distilled water: toluene: glacial acetic acid (2: 3: 1: 2: 0.1 v/v) as mobile phase. The proposed methods were checked using laboratory prepared mixtures and were successfully applied for the analysis of the dosage forms.