Electrochemical Sensing Detection Of β-Aadrenergic Agonists Molecules Based On Carbon Nanocomposites

Clenbuterol (CLB), Ractopamine (RAC) and Salbutamol (SAL) are a class of drugs called P-adrenergic agonist, which can be easily remained in animal tissues. β-adrenergic agonist will be comsumed by human body through food chain and cause poisoning. This is a serious threat to the public health and safety. In order to solve this threat, this thesis is concentrated on the investigation of nanomaterials applied on electrochemical sensors for the detection of P-adrenergic agonist. Our main research and results in aspects are as follows:Based on graphene oxide (GO) and acidified single-walled carbon nanotubes (SWCNT) which were ultrasonically dispersed into a Nafion solution, a modified glassy carbon electrode (GCE) with such GO/SWCNT-Nafion composite was prepared. The surface morphologies of different modified electrodes like bare GCE, GO-Nafion/GCE and GO/SWCNT-Nafion/GCE were characterized by scanning electron microscopy (SEM), and their corresponding cyclic voltammetry (CV) and differential pulse voltammetry (DPV) behaviors were investigated, showing that the GO/SWCNT-Nafion composite exhibited significantly electrocatalytic activity to clenbuterol (CLB,1). The oxidation mechanism has been discussed that the anilino group of CLB (1) was oxidized to form a radical cation (2), exhibiting a characteristic oxidation peak (I) at 0.98V, and reacted with CLB molecule via head to head coupling to form a diphenylamine intermediate (3), and then transformed a CLB dimmer (4) with an azo bond by intramolecular electrons transferring under low potential. With the optimum condition, the composite modified electrode showed good response to clenbuterol from 1.0×10-8 to 6.0×10-6 mol/L with a linear curve and a detection limit of 6.0×10-9mol/L. The modified electrode possessed nice selectivity, reproducibility and stability, which was successfully applied to determination of content of clenbuterol in pork meat and liver samples with a recovery rate from 96.9% to 105.3%, suggesting a potential application in food security field.Based on double-walled carbon nanotubes (DWCNT) and graphene oxide (GO) which were ultrasonically dispersed into a Nafion solution with a ratio of 1:1, a GO/DWCNT-Nafion modified glassy carbon electrode was prepared. The surface morphologies of different modified electrodes were characterized by scanning electron microscopy (SEM). The electrochemical behavior of RAC was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), and the oxidation mechanism was studied. The results showed that the oxidation of ractopamine involved two prontons and two electrons of its two phenolic hydroxyl groups. With the optimum condition, the modified electrode showed good response to ractopamine from 1.0×10-8 to 1.0×10-6 mol/L with a linear curve and a detection limit of 5.4×10-9 mol/L. The modified electrode possessed nice selectivity, reproducibility and stability, which was successfully applied to determination of concentrations of ractopamine in pig urine and pig serum samples with a recovery rate from to, suggesting a potential application in food security field.PtNPs/MWCNTs nanocomposite was prepared by liquid phase reduction, and then modified on the surface of glassy carbon electrode to synthesis PtNPs/MWCNTs-Nafion/GCE. The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) behavior were investigated, showing that PtNPs/MWCNTs-Nafion composite exhibited significantly electrocatalytic activity to sabutamol (SAL,1). The oxidation mechanism has been discussed that the phenolic hydroxyl group of sabutamol (1) was oxidized involved one proton and one electronic to form a radical intermediate (2),the radical intermediate (2) can resonate by intramolecular electrons transferring to form radical intermediate (3), and then transformed a intermediate (4) with a C-C bond by combination of two moieties of intermediate (3), the intermediate (4) can be easily converted to form a more stable salbutamol dimmer (5). With the optimum condition, the modified electrode showed good response to salbutamol with a linear range from 3.0×10-8 to 2.0×10-6 mol/L and a detection limit of 1.0×10-8mol/L. The modified electrode possessed nice selectivity, reproducibility and stability, which was successfully applied to determination of content of salbutamol in pork meat and liver samples with a recovery rate from 94.76% to 104.6%, suggesting a potential application in food security field.