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Atta N.F.,Cairo University | Galal A.,Cairo University | Ahmed R.A.,Forensic Chemistry Laboratories
Electroanalysis | Year: 2011

A simple and rapid method for morphine detection is described based on PEDOT electrode in the presence of SDS. The electrochemistry of morphine is investigated by CV, LSV and SWV. The effect of common interferences on the current response of morphine namely AA and UA is studied. The electrode is applied to the selective determination of morphine in urine samples in the linear ranges 0.3-8μmolL -1 and 10-60μmolL -1, with low detection limits of 50 and 68nmolL -1, respectively and recovery of 96.4%. The application of PEDOT is realized in determination of morphine in tablets successfully. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Atta N.F.,Cairo University | Galal A.,Cairo University | Ahmed R.A.,Forensic Chemistry Laboratories
International Journal of Electrochemical Science | Year: 2011

An electrochemical sensor was developed by using poly(3,4-ethylenedioxy thiophene) electrode in presence of different types of surfactants. Voltammetric behavior of isoniazid was studied at this electrode in the presence and absence of SDS and CTAB and interesting electrocatalytic effects were found. The presence of surfactant in the medium plays a key role in the electrostatic attraction and repulsion of isoniazid towards the polymeric surface in different pH values. The electrochemical behavior of isoniazid was investigated by cyclic voltammetry, linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The linear response obtained for isoniazid was in the range of 0.1 to 8 μmol L -1 and 10 to 100 μmol L -1 with correlation coefficients of 0.999 and 0.998 and detection limits 32 nmol L -1 and 45 nmol L -1, respectively. The utility of this modified electrode was demonstrated for the determination of INH in human urine. © 2011 by ESG.

Ahmed R.A.,Taif University | Ahmed R.A.,Forensic Chemistry Laboratories | Fekry A.M.,Cairo University | Farghali R.A.,Taif University | Farghali R.A.,Cairo University
Applied Surface Science | Year: 2013

In an attempt to increase the stability, bioactivity and corrosion resistance of Ti-6Al-4V alloy, chitosan (CS) biocomposite coatings reinforced with multiwalled-carbon nanotubes (MWCNTs), and calcium carbonate (CaCO 3) for surface modification were utilized by electroless deposition. Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) reveals the formation of a compact and highly crosslinked coatings. Electrochemical techniques were used to investigate the coats stability and resistivity for orthopedic implants in simulated body fluid (SBF). The results show that Est value is more positive in the following order: CaCO3/MWCNTs/CS > CS/MWCNTs > CS > MWCNTs. The calculated icorr was 0.02 nA cm-2 for CaCO3/MWCNTs/CS which suggested a high corrosion resistance. © 2013 Elsevier B.V. All rights reserved.

Atta N.F.,Cairo University | Galal A.,Cairo University | Ahmed R.A.,Forensic Chemistry Laboratories
Journal of the Electrochemical Society | Year: 2011

A promising electrochemical sensor was developed using poly(3,4-ethylene dioxythiophene) modified platinum electrode in the presence of sodium dodecyl sulphate (SDS). This sensor is sensitive for the determination of catecholamine compounds, namely dopamine, epinephrine, L-norepinephrine, and L-DOPA, as well as serotonin (ST) in the presence of interference molecules such as uric acid, ascorbic acid (AA), and glucose. The presence of SDS in the medium plays a key role in the electrostatic attraction of these compounds toward the polymeric surface and causes repulsion toward the interfering ones. Cyclic voltammetry, linear sweep voltammetry, ultraviolet-visible (UV-vis), nuclear magnetic resonance and electrochemical impedance spectroscopy were used to verify the behavior of the studied compounds in micellar media. In the presence of an anionic surfactant, the presence of large excess of AA and glucose did not interfere with the voltammetric responses of catecholamine and ST. The linear response was obtained for serotonin in the range of 0.05-10 mol l -1 and 20-100 mol l -1 with correlation coefficients of 0.997 and 0.998 and detection limits 48 and 71 nmol l -1, respectively. The utility of this modified electrode was demonstrated for the determination of ST in human urine. © 2011 The Electrochemical Society.

Ahmed R.A.,Taif University | Ahmed R.A.,Forensic Chemistry Laboratories
Acta Metallurgica Sinica (English Letters) | Year: 2016

In this study, the corrosion behavior of Ni47Ti49Co4 shape memory alloy (SMA) was investigated in simulated saliva solution with the binary alloy Ni51Ti49 as a reference. The surface morphology and the chemical composition of the oxide films were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy before and after immersion in the test solutions, respectively. The results showed that the ternary alloy was less affected by the test solution, owning to the formation of passive layer composed mainly of the oxides of titanium and cobalt in several oxidation states. Cyclic voltammetry, electrochemical impedance spectroscopy and potentiodynamic polarization measurements affirmed that the passive oxide film significantly improved the corrosion resistance of Ni47Ti49Co4 SMAs as demonstrated by the smaller corrosion current density, larger resistance and smaller capacitance. Consequently, alloying with cobalt, which has paramount importance in enhancing the passive layer, expands the use of Ni47Ti49Co4 SMAs in dental work as new nitinol alloys with high corrosion resistances. © The Chinese Society for Metals and Springer-Verlag Berlin Heidelberg 2016.

Ahmed R.A.,Taif University | Ahmed R.A.,Forensic Chemistry Laboratories
Oriental Journal of Chemistry | Year: 2016

Corrosion inhibition behavior of Ascorbic acid (AA) vitamin C and Thiamine (Th) vitamin B1 on mild steel corrosion in 0.5 M HCl was investigated at various immersion times. The electrochemical characteristics of mild steel in absence and presence of the inhibitors were verified by the cyclic voltammetry method. The protective properties of the passive film were acquired by electrochemical impedance spectroscopy. The best inhibitive performance was obtained for VitB1. The polarization curves indicated the high inhibition efficiency of the inhibitors. The existence of a protective film on mild steel was confirmed by SEM techniques. Computational chemistry was carried out to establish the mechanism of corrosion inhibition.

Atta N.F.,Cairo University | Galal A.,Cairo University | Ali S.M.,Cairo University | El-Said D.M.,Forensic Chemistry Laboratories
Analytical Methods | Year: 2014

A voltammetric analytical method based on a combination of β-cyclodextrin (CD), Nafion® (NF) and a gold electrode modified with poly(3,4-ethylene-dioxythiophene) (PEDOT) has been successfully developed (Au/PEDOT/NF/CD) for the determination of dopamine (DA) in the presence of ascorbic acid (AA) or uric acid (UA). Optimization of the sensor was conducted, including variables such as the type of substrate, concentration of each modifier, pH of the electrolyte, method of deposition of the polymer and immobilization of CD, and also the time for accumulation of the compound at the modified surface. The synergistic effect of the high conductivity of PEDOT and NF, in addition to the pre-concentrating effect of CD, its different host-guest inclusion complexes and its formation of hydrogen bonds with each compound, was used to construct a stable electrochemical sensor for the determination of these compounds. Under optimized conditions a linear calibration curve was obtained for the determination of dopamine in urine within the range 0.6-320 μmol L-1, with a correlation coefficient of 0.996 and detection limit of 5.84 nmol L-1. The proposed sensor was successfully used for the determination of tertiary mixtures of DA, AA and UA, of DA, AA and acetaminophen (APAP), and of binary mixtures of DA and serotonin (ST). It has been demonstrated that Au/PEDOT/NF/CD can be used as a sensor with excellent reproducibility, sensitivity and stability. © 2014 The Royal Society of Chemistry.

Ahmed R.A.,Taif University | Ahmed R.A.,Forensic Chemistry Laboratories | Fekry A.M.,Cairo University
International Journal of Electrochemical Science | Year: 2013

A biosensor electrode based on the incorporation of super nanoparticles paramagnetic iron oxide (α-Fe3O4) in chitosan (CS) film coated on platinum electrode, was developed for the determination and removal of heavy metals. The morphological properties of the homogenous α-Fe3O4/CS nanocomposite were studied with scanning electron microscopy (SEM), Energy Dispersive X-ray analysis (EDX), and thermal gravimetric analysis (TGA). The morphological results indicate the successful formation of α-Fe3O4/CS nanocomposite and high stability of the film. The α-Fe3O4/CS nanocomposite showed a great efficiency for the determination of As, Pb, and Ni ions from aqueous solution using various electrochemical techniques. The presence of α-Fe3O4 nanoparticles results in increased active surface area and enhanced electron transfer. Results showed that this novel α-Fe3O4/CS nanocomposite was successfully applied for sewage water and human urine samples with verylow detection limit. © 2013 by ESG.

Ahmed R.A.,Taif University | Ahmed R.A.,Forensic Chemistry Laboratories
Industrial and Engineering Chemistry Research | Year: 2015

The corrosion performance of Ni47Ti49Co4 shape memory alloys (SMA) in artificial urine solution was evaluated in comparison with Ni51Ti49 alloy as reference, at 37°C and pH 5.6-6.4. SEM results revealed less pitting attack for Ni47Ti49Co4 SMA surface after immersion in artificial urine solution. The XRD analysis demonstrated the formation of passive film on Ni47Ti49Co4 SMA. The XPS analysis indicated that the film mainly consisted of O, Ti, Co, P, and a small amount of Ni, and the concentration of Ni ions release was greatly reduced compared to that of the Ni51Ti49 SMA. Linear polarization results illustrated that corrosion potential (Ecorr), corrosion current density (icorr), and ac polarization resistance (Rp) were affected greatly by alloying Co to Nitinol alloy. Our observations indicated that the corrosion resistance of the ternary alloy, Ni47Ti49Co4 SMA, offers superior corrosion resistance in artificial urine when compared to Ni51Ti49 SMA, which was suitable for medical applications. © 2015 American Chemical Society.

Fadlallah S.A.,Taif University | Fadlallah S.A.,Cairo University | El-Bagoury N.,Taif University | El-Bagoury N.,Central Metallurgical Research and Development Institute | And 5 more authors.
Journal of Alloys and Compounds | Year: 2014

Nowadays, Nickel-titanium nearly equiatomic is considered as one of the best biomaterials. The aim of the present work deals with the evolution of the electrochemical behavior of NiTi in simulated oral environment. The hardness, microstructures corrosion resistance and antibacterial performance of NiTi alloy were compared with pure titanium. The hardness of NiTi is twice the hardness of pure titanium. Electrochemical techniques were used to detect the corrosion resistance of both biomaterials in Hank's solution containing (-)-epigallocatechin gallate (EGCG) which used to simulate the oral environment. In the physiological solution selected for the present study, the impedance spectroscopy (EIS) results showed that EGCG sharply increase the corrosion resistance of NiTi from 129 kΩ cm2 to 1.10 T Ω cm 2 while slowly increase the corrosion resistance of pure titanium from 9.4 kΩ cm2 to 11.3 kΩ cm2 during the duration time of immersion at 37 C. The plate-counting method was used to evaluate the antibacterial performance against Staphylococcus aureus (ATCC 6538). Among the two specimens of biomaterials studied, the antibacterial performance results revealed that the NiTi alloy is better than the pure titanium. The morphology and chemical structure of NiTi and Ti samples were systematically investigated by scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDX). The study confirmed that the distinctive characteristics of the NiTi alloy back to its chemical composition with two phases from nickel and titanium. © 2013 Elsevier B.V. All rights reserved.

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