Studies On The Applications And Methodology Estimations Of Voltammetry And Ultraviolet And Visible Spetrophotometry In β-agonists

P-agonists could reduce carcass fat, increase muscle mass, and improve growth rate and feed conversion when fed to animals. So in the livestock industry, P-agonists have been used as growth promoters. While the remained P-agonists in animal food will do harm to people’s health, a sensitive, rapid and simple method to monitor therapeutic use as well as to control the illegal use of SAL is essential.The main contents of the thesis are summarized as follow:(1) Study of electrochemical behavior and application of P-agonists on SWNTs/GCEMaking use of the unique structure and extraordinary properties of carbon nanotube, the electrochemical behaviors of11β-agonists were explored by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) on single-wall carbon nanotubes (SWNTs) modified glassy carbon electrode (SWNTs/GCE). The parameters including the pH of supporting electrolyte, accumulation potential and time, which govern the analytical performance of P-agonists have been studied and optimized. The11P-agonists showed various electrochemical behaviors due to their structural diversity. A well-defined oxidative peak and two pairs of reversible redox peaks can be seen in the presence of salbutamol (hydroxybenzyl P-agonists). A well-defined oxidative peak (Epa≈0.6V) can be seen in the presence of terbutaline and metaproterenol (resorcinolβ-agonists) at the SWNTs/GCE. In addition, ractopamine, ritodrine, fenoterol (phenolic β-agonists) showed a pair of reversible redox peaks on a low potential range and a well-defined oxidative peak on a high potential range. Cimbuterol, mabuterol, brombuterol and clenbuterol (aniline P-agonists) showed a pair of reversible redox peaks on a low potential range and two well-defined oxidative peaks on a high potential range. The corresponding peak current increased linearly with the increasing concentrations of β-agonists in certain range of concentrations. The proposed electrode can be applied for quantitative detection of P-agonists and the proposed method was fast and simple.(2) Study on the spectrophometric determination of P-agonists based on the enzymatic catalytic reactionA novel and one-step colorimetric measurement for the detection of P-agonists based on tyrosinase catalytic reaction was developed. The reaction mechanisms between β-agonists and tyrosinase were studied. The parameters including the pH of the buffer solution, the concentration of tyrosinase, and the incubation time, which influence the enzyme catalytic reaction have been studied and optimized. The enzymatic oxidation products of β-agonists with phenolic group exhibited different color transitions based on the different substituent groups on the aromatic ring, whereas β-agonists with the aniline group and the resorcinol group remained colorless. The visual color discrepancy between them has been used to intuitively and conveniently discriminate the phenolic group β-agonists, such as ractopamine, isoxsuprine, ritodrine and fenoterol. The absorbance of the enzymatic oxidation product is directly correlated with the concentrations of added β-agonists. The method is rapid, intuitive, simple and with wide linearity range, so it is useful for practical application.(3) Study on the voltammetric determination of P-agonists based on the enzymatic catalytic reactionMaking use of tyrosinase catalytic reaction, the electrochemical behaviors of the enzymatic oxidation products of P-agonists was explored by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) glassy carbon electrode (GCE). The parameters including the pH of the buffer solution, the concentration of tyrosinase, and the incubation time, which influence the enzyme catalytic reaction have been studied and optimized by CV and DPV. The accumulation potential and time were also optimized by DPV. Under the optimum conditions, quantitative determination for ractopamine, isoxsuprine, ritodrine and fenoterol was carried out by DPV. The results showed that DPV exhibited higher sensitive and lower detection limit for the determination of target, compared with the results using UV-vis spectra analysis techniques.