| As residual drugs in fishery environment have been associated with harmful effects on ecological environment, quality of aquatic products and human health, an accurate, simple, fast, low cost and on line monitoring method to residual drugs was necessary. In this paper, the electrochemical behaviors of several drugs were investigated by voltammetry using paste electrode as working electrode prepared with electrode material conductive carbon black. Based on good voltammetric analytical performances, several electrochemical sensors for residual drugs in fishery environment were prepared. The details are summarized as follows:(1) The electrochemical behaviors of ciprofloxacin hydrochloride (Cipro) were investigated by voltammetry using conductive carbon black paste electrode as working electrode. Results indicate that an irreversible adsorption-controlled oxidation reaction of Cipro occurre in the B-R buffer solution of pH 4.0 with two protons and two electrons transfer. The electron transfer coefficient a is 0.37 and the standard surface reaction rate constant k’s is 0.95 s-1. Effect factors, including species of the supporting electrolyte, pH, ionic strength of supporting electrolyte, accumulation potential and accumulation time, were studied and optimized. Under the optimal conditions, there is a linear relationship between the oxidative peak current of Cipro and its concentration over the range of 2.5×10-7～6.0×10-5 mol/L with a detection limit of 9.5×10-8 mol/L (signal/noise=3). The method was applied to determine trace Cipro in real fishery water samples. And the outcomes were satisfactory with an average recovery rate of 102.73%.(2) The voltammetric behaviors of Crystal violet (CT) and Ciprofloxacin hydrochloride (Cipro) were studied at the conductive carbon paste electrode. Results demonstrated that in B-R buffer of pH 4.5 the two molecules displayed sensitive electrochemical responses, which were separate clearly. Some of the key factors, including the properties of supporting solution and accumulation parameters, were studied, following by optimization. And then a new method for determining residual CT and Cipro was developed. Tested with half impulsive differential mode, there was a linear relationship between the peak currents and the concentration of CT in the range of 2.5×10-8～1.325×10-6 mol/L with a coexistence of Cipro; there was a linear relationship between the peak currents and the concentration of Cipro in the range of 5.0×10-8～4.85×10-6 mol/L with a coexistence of CT. The detection limits were 10.5 and 21.2 nmol/L (signal/noise= 3), respectively. Satisfactory results were obtained when the new method was used to measure CT and Cipro in the real fresh fishery water samples with average recovery rates of 97.8% and 101.1%, respectively.The method exhibits many attractive advantages, such as simple operation, rapid response, low cost, and so on. Therefore it is promising for popular application.(3) The influence of surfactant on the voltammetric behavior of Doxycycline (DOC) was investigated in this paper. And a new electrochemical method for determining DOC was developed with the help of surfactant. In B-R buffer solution of pH 2.0, the presence of 2.0×10-4 mol/L sodium dodecyl benzene sulfonate (SDBS) could improve the accumulation ability significantly. With the tested conditions, an irreversible and adsorption-controlled electrode reaction occurs with 1 proton and 2 electrons participation. After the experimental parameters, including species of surfactants, supporting electrolyte, pH, accumulation time and accumulation potential, etc., are optimized, it is found that the anodic peak current of DOC is proportional to its concentration in the range of 1.0×10-7～2.3×10-5 mol/L with a detection limit of 4.5×10-8 mol/L (signal/noise=3). The electrochemical method developed here was used to detect trace amount of DOC in fresh fisheries water samples. A satisfactory result was obtained with average recoveries in the range of 97.44～105.28%. |
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