Carbon Nanotube Reinforced Heterostructure Electrochemical Sensor for the Simultaneous Determination of Morphine and Fentanyl in Biological Samples

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^-6cm^2 s^-1and1.615×10^-6cm^2s^-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.