Browsing by Author "Aboul-Enein, Hassan Y."

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Citation Count: 8
Electro-Oxidation and Determination of Benomyl by Square-Wave Adsorptive Stripping Voltammetry
(Oxford Univ Press inc, 2014) Sarigul, Tuba; Inam, Recai; Demir, Ersin; Aboul-Enein, Hassan Y.
The electro-oxidation of the benomyl fungicide was studied by square-wave adsorptive stripping voltammetry. The voltammetric current at a glassy carbon electrode was acquired within the pH range 1.0-10.0. The quantitation was performed using the peak generated at +1144 mV by scanning the potential from +0.00 to +1600 mV (versus an Ag/AgCl reference electrode, 3 M NaCl). Accumulation potential = 0.0 mV, accumulation time=45 s, frequency=75 Hz, pulse amplitude=-60 mV, and staircase step potential =7 mV were used as square-wave parameters. The peak current versus concentrations plot were rectilinear over the range from 0.081 to 1.496 mu g/mL with an LOD of 0.024 mu g/mL. Mean recovery was 99.0% (0.198 +/- 0.011 mu g/mL), which was very close to the benomyl content spiked into river water (0.20 mu g/mL). The method was efficiently applied for benomyl determination in the pesticide formulation Minelate 50WG (R), and the average determined content of 49.8 +/- 0.16 (n = 5) was consistent with the 50% benomyl (w/w) quoted by the manufacturer. The benomyl voltammograms recorded between days exhibited a negligible degradation into carbendazim metabolite, and therefore all results were given as the total benomyl concentration. The high recoveries and low RSD gave evidence of good accuracy and precision.
Citation Count: 13
Electrochemical Evaluation of the Total Antioxidant Capacity of Yam Food Samples on a Polyglycine-Glassy Carbon Modified Electrode
(Bentham Science Publ Ltd, 2020) Demir, Ersin; Senocak, Ahmet; Tassembedo-Koubangoye, Mouhoum F.; Demirbas, Erhan; Aboul-Enein, Hassan Y.
Background: The total antioxidant capacity of yam food grown in southern African regions was investigated by a polyglycine-glassy carbon modified electrode. The modified electrode was fabricated using glycine solution on glassy carbon electrode by electrodeposition method. The proposed modified electrode is found to be nearly 3.15-fold more sensitive than the bare electrode. For the measurement of the total antioxidants of yam, differential pulse stripping voltammetry (DPSV) was employed with standard quercetin compound. Methods: The total antioxidant capacity of yam was deduced by DPSV and cyclic voltammetry (CV) methods. The basic parameters for the stripping technique such as pH, accumulation time and accumulation potential were optimized as 20 s, 200 mV and a pH of 3 Britton-Robinson (B-R) buffer solutions in 0.5 mg quercetin/L, respectively. Results: In the optimization condition, the linear working range was determined between 5.0 mu g/L and 80.0 mu g/L for the quercetin. The detection (LOD) and quantification (LOQ) limits of quercetin were found to be 0.39 mu g/L and 1.39 mu g/L on the modified electrode by DPSV, respectively. The procedure was also applied to natural yam samples and total antioxidant capacity of 0.1 kg of yam was determined as 96.15 +/- 0.85 mu g/L of equivalent quercetin at 95% confidence level with the relative standard deviations of 0.88%. Conclusion: Sensitive and selective voltammetric method was developed for the determination of total antioxidant capacity in yam. Moreover, the modified polyglycine-glassy carbon electrode was constructed more selectively for quercetin. As a result, a simple, sensitive and rapid new voltammetric method for the determination of antioxidants has been developed using the modified electrode.
Citation Count: 3
Fe³⁺ - Ion Selective Electrode Developed as a Detector in Flow Injection Analysis
(Bentham Science Publ Ltd, 2015) Demir, Ersin; Kemer, Baris; Isildak, Ibrahim; Aboul-Enein, Hassan Y.
A new polyvinyl chloride (PVC) membrane Fe3+ - ion selective electrode was constructed as a detector for the analysis Fe3+ using a home-made low-volume flow through cell. Optimum working conditions for the flow injection analysis (FIA) measurements were examined. In addition, under optimum conditions, potentiometric performance characteristics of the Fe3+ ion-selective electrode were investigated. Electrode had a linear response in the concentration range of 1.0 x 10(-3)-1.0 x 10(-6) M (R-2=0.9961, y=24.7+772.0). Reproducibility of the electrode responses was very satisfied. The potential of Fe3+ ion selective electrode was decreased intra and inter day 0.9 % and 3.7% respectively. The designed flow-through cell system as Fe3+ detector revealed sampling rates of approximately 50 injections per hour. The obtained results in FIA were in a good agreement with AAs results at % 95 confidence level for each syrups.
Citation Count: 15
A Novel all Solid-State Contact PVC-Membrane Beryllium-Selective Electrode Based on 4-Hydroxybenzo-15-Crown-5 Ether Ionophore
(Bentham Science Publ Ltd, 2018) Isildak, Ibrahim; Attar, Azade; Demir, Ersin; Kemer, Baris; Aboul-Enein, Hassan Y.
Aim: A novel all solid-state contact PVC-membrane beryllium-selective electrode based on 4-hydroxybenzo-15-crown-5 ether as an ionophore is described. Results: The best performance was obtained with a membrane composition of 4% ionophore, 67% dioctyl sebacate (DOS), 28% poly(vinyl chloride) (PVC), and 1% potassium tetrakis (p-chloro) phenylborate (KTClPB) (w/w). The all solid-state contact PVCmembrane beryllium-selective electrode together with an Ag/AgCl reference electrode exhibited sub-Nernstian response with a slope of 22 +/- 1 mV/decade to beryllium ions from 1.0x10(-6) to 1.0x10(-1) M, and resulted a considerably low detection limit of 6.2x10(-7). The electrode had a good performance in selectivity over a wide range of interfering cations tested. It showed a working pH range between 4.0-8.2 with fast response time (< 10 s) and a good reproducibility. Conclusion: The all solid-state contact PVC-membrane beryllium-selective electrode developed was successfully applied in potentiometric titration of Be2+ ions with EDTA.
Citation Count: 11
A Novel Iron(III)-Selective Membrane Potentiometric Sensor Based on 5-Chloro-3-[4-(trifluoromethoxy) phenylimino] Indolin-2-one
(Bentham Science Publ Ltd, 2015) Demir, Ersin; Kemer, Baris; Bekircan, Olcay; Aboul-Enein, Hassan Y.
A novel polyvinyl chloride (PVC) membrane sensor that is highly selective to Fe3+ ions was prepared by using 5-chloro-3-[4-(trifluoromethoxy) phenylimino] indolin-2-one (CFMEPI) ionophore. The sensor exhibits a Nernstian response for Fe3+ ions over a wide concentration range (1.0 x10(-2) -1.0x10(-6)M) with a slope of 46.7 +/- 0.5 mV per decade. The sensor has a response time of 20s and can be used for at least 3 months without any measurable divergence in potential. It was concluded that the sensor response was pH independent in the range of 4.0-8.61. The sensor has some advantages such as short analysis time, particularly high selectivity towards iron (III). The sensor was used successfully for direct determination of Fe3+ in several synthetic and real samples with satisfactory results.
Citation Count: 2
RETRACTED: Use of electrochemical methods to determine the effect of brewing techniques (Espresso, Turkish and Filter coffee) and roasting levels on the antioxidant capacity of coffee beverage (Retracted Article)
(Springer india, 2023) Yildirim, Sevinc; Gök, İlkay; Gök, İhsan; Aboul-Enein, Hassan Y.; Gastronomi ve Mutfak Sanatları / Gastronomy and Culinary Arts
Coffee is a complex mixture of chemicals, which provide biologically active compounds with various health benefits. The some biologically active compounds arising from both its natural structure and formed after processing were determined as an antioxidant capacity of coffee beverages. In this study, we aimed to determine how roasting levels of Arabica coffee seed (light, medium, dark) and three brewing techniques-decoction methods (Turkish coffee), infusion method (filter coffee) and pressure methods (Espresso)-affect total antioxidant capacity in a cup of coffee beverage by electrochemical methods such as square wave stripping voltammetry (SWSV), differential pulse stripping voltammetry (DPSV) and cyclic voltammetry (CV). Antioxidant capacities of the coffee samples in terms of the equivalent amounts were determined according to standard oxidation peaks of rutin and caffeic acid. The highest antioxidant capacity was found in espresso coffee prepared at light roasting coffee seeds as equivalent the routine and caffeic at 9.4 +/- 0.2 g/L and 19.7 +/- 0.7 g/L, respectively with SWSV on a carbon paste electrode. As a result, SWSV, DPSV and CV voltammetric methods, fast, reliable, fully validated and without any pretreatment are alternative to conventional analytical methods to evaluation antioxidant values in any food samples.
Citation Count: 0
RETRACTION: Use of electrochemical methods to determine the effect of brewing techniques (Espresso, Turkish and Filter coffee) and roasting levels on the antioxidant capacity of coffee beverage (Retraction of Vol 60, Pg 1933, 2023)
(Springer india, 2024) Yildirim, Sevinc; Demir, Ersin; Gök, İhsan; Gok, Ilkay; Aboul-Enein, Hassan Y.
[No Abstract Available]
Citation Count: 16
Voltammetric Determination of Ophthalmic Drug Dexamethasone Using Poly-glycine Multi Walled Carbon Nanotubes Modified Paste Electrode
(Bentham Science Publ Ltd, 2018) Demir, Ersin; Inam, Onur; Inam, Recai; Aboul-Enein, Hassan Y.
Background: Dexamethasone has been used in ophthalmology for the treatment of different eye diseases and it is a powerful synthetic member of the glucocorticoid class of steroid medicament having anti-inflammatory and immunosuppressant characteristics. The aim of this study is to develop a rapid, sensitive and selective voltammetric method for its determination using polygylcine-multi walled carbon nanotubes (polyglycine-MWCNTs) modified paste electrode. Methods: The electro-activity and the voltammetric behavior of dexamethasone on the polyglycine-MWCNTs electrode were deduced by cyclic voltammetry (CV), square wave stripping voltammetry (SWSV), differential pulse voltammetry (DPV) and linear sweep voltammetry (LSV). The method permits accurate and sensitive detection of the ophthalmic drug dexamethasone in the presence of ascorbic acid, dopamine and uric acid from the generated anodic peaks at +950 mV, +740 mV and +700 mV, respectively. Results: The cyclic voltammetric study indicates that dexamethasone created a single anodic peak at about +1100 mV in pH 3 B-R solution and none of the cathodic peak appeared in the subsequent reverse scan. The detection and quantification limits measured for LSV were 0.087 mg/L and 0.29 mg/L, respectively. The extent of recoveries in the presence of equal amounts (1: 1 mass ratio) of ascorbic acid, dopamine and uric acid were calculated as 98.28 +/- 0.45, 94.46 +/- 1.77 and 98.57 +/- 0.60%, respectively. The voltammetric procedure was also applied to dexamethasone spiked urine samples(5.0 mg/L) and the percent recovery was determined as 95.2% with the relative standard deviations of 3.29%. Conclusion: Sensitive and selective voltammetric method was proposed for the direct determination of dexamethasone. The modified polyglycine-MWCNTs paste electrode enabled the direct determination of dexamethasone in the presence of biological molecules such as ascorbic acid, dopamine and uric acid.