Research On Molecularly Imprinted Sensors For Ethylparaben, Ascorbic Acid And Chloramphenicol

In this paper, based on Ethylparaben, Ascorbic acid and Chloramphenicol, seven kinds of molecularly imprinted electrochemical sensor was developed and successfully used in the food safety testing, the main contents are as follows:(1) A voltammetric sensor based on MIPs, which was constructed on the surface of a glassy carbon electrode with the ethylparaben (EP) as template and methacrylic acid as functional monomer, was developed for determination of paraben in this work. Electrochemical oxidation behaviors of EP on the imprinted electrode have been investigated with CV, SWV and I-t. The results show that, the peak currents were proportional to the concentration of EP in the range of5.0×10-6-5.0×10-5mol/L with the detection limit of1.1×10-6mol/L (S/N=3) and the relative standard deviation (RSD) of peak current was4.8%(n=7). On the other hand, the voltammogram of EP recorded with imprinted electrode was different from that with the bare electrode at the same conditions. The imprinted electrode displayed substantially specific binding of paraben. Structural unanalog benzoic acid and vitamin C had almost no response.(2) In order to establish a rapid detection technique of ethylparaben (EP), EP was used as template molecule, o-phenylenediamine (o-PD) as functional monomer, poly(o-phenylenediamine)(PPD) film was electropolymerized on the surface of a glassy carbon electrode and a using cyclic voltammetry (CV). Furthermore, the same optimization condition used to electropolymerize the film on the surface of a dual channel screen-printed carbon electrode (SPCE), which could achieve two repetitive measurements by using the same sample drop and improve test efficiency. And last,the ultrapure water was used to elute the template molecules. The electrochemical properties of the molecularly imprinted sensor were investigated using CV, square wave voltammetry (SWV) and current-time curve (I-t) methods.The response current of the former sensor had good linear relationship with the concentration of EP in two range of3.2×10-7～1.6×10-6mol/L and7.8×10-6-5.8×10-5mol/L, respectively. The detection limit was2.2×10-8mol/L. The response current of the latter sensor had good linear relationship with the concentration of EP in two range of3.2×10-7-3.2×10’6mol/L and2.7×10-5-5.6×10-4mol/L, respectively. The detection limit was9.7×10-8mol/L. The proposed method was applied to determine EP in commercial soybean sauce, and high performance liquid chromatography method was used to verify. The results showed that the detection technique was rapid, accurate, inexpensive, and suitable for determination of EP in soybean sauce and other food samples.(3) In order to establish a rapid detection technique of ascorbic acid (AA), AA was used as template molecule, o-PD as functional monomer, PPD film was electropolymerized on the surface of a glassy carbon electrode and a using CV. Furthermore, the same optimization condition used to electropolymerize the film on the surface of a dual channel SPCE. And last,the eluting solution was used to elute the template molecules. The electrochemical properties of the molecularly imprinted sensor were investigated using CV, SWV and I-t methods. The response current of the former sensor had good linear relationship with the concentration of AA in two range of1.0×10-6-1.0×10-3mol/L and1.0×10-3-4.5×10-3mol/L, respectively. The detection limit was4.9×10-7mol/L. The response current of the latter sensor had good linear relationship with the concentration of AA in two range of4.5×10-7-1.4×10-5mol/L and1.4×10-5-4.09×10-4mol/L, respectively. The detection limit was1.1×10-7mol/L. The proposed method was applied to determine AA in commercial orange juice, and2,6-dichlorophenol indophenol titration method was used to verify. The results showed that the detection technique was rapid, accurate, inexpensive, and suitable for determination of AA in orange juice and other food samples. (4)In order to establish a rapid detection technique of chloramphenicol (CAP), CAP was used as template molecule, o-PD as functional monomer, PPD film was electropolymerized on the surface of a glassy carbon electrode and a using CV. Furthermore, the same optimization condition used to electropolymerize the film on the surface of a dual channel SPCE. And last,the eluting solution was used to elute the template molecules. The electrochemical properties of the molecularly imprinted sensor were investigated using CV and SWV methods. The response current of the former sensor had good linear relationship with the concentration of CAP in a range of1.0×105-1.0×10-4mol/L. The detection limit was5.2×10-6mol/L. The response current of the latter sensor had good linear relationship with the concentration of CAP in two range of2.0×10-5-1.4×10-4mol/L and1.4×10-4-3.2×10-4mol/L, respectively. The detection limit was1.9×10-6mol/L. The proposed method was applied to determine CAP in commercial pure milk, and ultraviolet spectrophotometry was used to verify. The results showed that the detection technique was rapid, accurate, inexpensive, and suitable for determination of CAP in pure milk and other food samples.