Entity

Time filter

Source Type


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. Source


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. Source


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. Source


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. Source


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. Source

Discover hidden collaborations