Zahra Nazari; Zarrin Eshaghi
Abstract
In this study, an electrochemical sensor for simultaneous measurement of morphine and fentanyl based on a modified pencil graphite electrode with a semiconductor nanocrystalline structure was developed.The first layer of the sensor has a core of thioglycolic acid-bonded cadmium selenidequantum dot (TGA-CdSe), ...
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In this study, an electrochemical sensor for simultaneous measurement of morphine and fentanyl based on a modified pencil graphite electrode with a semiconductor nanocrystalline structure was developed.The first layer of the sensor has a core of thioglycolic acid-bonded cadmium selenidequantum dot (TGA-CdSe), surrounded by a second layer, zinc sulfide quantum dot (ZnS). Functionalized carbon nanotubes (FCNT) have also been used to reinforce the sensor structure (TGA-CdSe/ZnS@FCNT). Measurements were performed by differential pulse voltammetry (DPV) and cyclic voltammetry (CV).The synthesis of nanostructures was confirmed by FTIR, EDX, SEM and XRD. In order to optimize the effective factors in the performance of this sensor, the Taguchi orthogonal array (OA16) design has been utilized. TheCV voltammograms showed irreversible oxidation peaks at potentials of 0.9 V and 0.38 V for fentanyl and morphine respectively. The transfer coefficients (α) of 0.96for morphine and 0.95 for fentanyl obtained. The diffusion coefficients gained on the electrode surface by chronoamperometrywere 3.84×10-6cm2 s-1and1.615×10-6cm2s-1 for morphine and fentanyl, respectively. Under optimal conditions, the linear concentration range and detection limit for morphine were 0.08-100 μM, and 0.024 μM. For fentanyl two linear ranges of 0.02-8μM, 8-100 μM and 0.006 μM were obtained. The fabricated sensor can be well used for the simultaneous measurement of morphine and fentanyl in biological samples with acceptable relative recoveries in the range of 98.3-102.
Jahanbakhsh Raoof; Mohammad Ali Karimi; Leila Asadian-Zarrinabadi; Mohaddeseh Amiri-Aref
Volume 1, Issue 1 , March 2014, , Pages 12-19
Abstract
The electrochemical oxidation and determination of tryptophan (Trp) and glutathione (GSH) in the presence of catechol as a homogeneous redox in the aqueous medium were investigated at the surface of a carbon paste electrode modified with multi-walled carbon nanotube (MWCNT-CPE) using cyclic voltammetry ...
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The electrochemical oxidation and determination of tryptophan (Trp) and glutathione (GSH) in the presence of catechol as a homogeneous redox in the aqueous medium were investigated at the surface of a carbon paste electrode modified with multi-walled carbon nanotube (MWCNT-CPE) using cyclic voltammetry (CV), double step potential chronoamperometry and differential pulse voltammetry (DPV) techniques. The results of differential pulse voltammetry showed two well-resolved anodic peaks for glutathione and tryptophan, which leads to voltammetric determination of each of them. The results shows the electrooxidation peak currents of GSH and Trp is linear in the concentration range of 2×10-6 M-5×10-5 M and 4×10-6 M-6×10-5 M, respectively. The kinetic parameters such as: the chemical reaction rate constant (kh) and transfer coefficient (α) were calculated 2.01×102 cm3 mol-1 s-1 and 0.31, respectively. Also, the apparent diffusion coefficient, Dapp, for GSH was found to be 1.95×10-6 cm2 s-1 in aqueous buffered solution. The proposed method was successfully applied for determination of glutathione and tryptophan in real sample using standard addition method.
