Study On Fabrication Of Sulfonamide Sensor Based On Carbon Nanotubes

Functional nano materials have now been extremely used for preparation of electrochemical sensors and analytical purpose. Due to their surface and interface effect, the quantum size effect, the macroscopic quantum tunnel effect and the small size effect, functional nano materials possess much fantastic physical and chemical advantages. It will be a promising avenue for application of nano materials in electrochemical sensor research.In field of food production, residue of antimicrobial has now been a focus of the society. Because of their broad spectrum antimicrobial effect, sulfonamides are wildly added in feed stuff for treatment of animal diseases, which results in more and more animal product samples are sulfonamides residue positive. Modern instruments methods such as GC-MASS, HPLC, HPLC-FL, etc. have been successfully used for evaluation of the drug residues with the advantageous of high sensitive and accuracy. However these methods also have drawbacks of instrument expensive, procedure tedious, skilled laboratory personnel deeding, cost and time tedious. Hence, searching for rapid detection of sulfonamide residues in animal derived food is of particular significance. Electrochemical detection methods have the advantages of simple, low cost, fast response and easy to use.In this dissertation, we aim at developing an electrochemical sensor based on carbon nanotubes (MWCNTs) functional materials for determination of sulfonamides residues. Electrocatalytic effect and high current reponse of sulfonamides on MWCNTs based electrochemical sensor were thoroughly discussed. Incorporation of MWCNTs, OPPF6ionic liquid, Nafion and cobalt phthalocyanine (CoⅡPc), high performance electrochemical sensors were designed and discussed. Shortcoming such as insufficient of selectivity and sensitivity, short working life and matrix interference were successfully resolved. And the new sensors were successfully used for the determination of sulfadiazine in drug and urine samples. In brief, the major results of the research were listed below. 1. Based on Pt disk electrode, we produced a MWCNTs-Pt modified electrode. Due to the electrocatalytic effect of MWCNTs, the over voltage of sulfanilamide oxidation was negtively shifted dramaticly, but the anode current response was highly sensitive response. And the mechanism of electrochemical reaction of sulfanilamide was also discussed.2. Based on glassy carbon (GC) disk electrode, a MWCNTs-GC modified electrode was prepared. Due to the electrocatalytic effect of MWCNTs, the over voltage of sulfanilamide oxidation was negtively shifted dramaticly, but the anode current response was highly sensitive response. And pleased performances such as linear range, detection limit, repeatability, stability were obtained by MWCNTs-GC in sulfanilamide determination, wich would be useful for new sensor designing.3. A MWCNTs/OPPF6-GC modified electrode was produced by using OPPF6ionic liquid as the dispersing and binding agent of MWCNTs. Owing to the performance of OPPF6ionic liquid, troubles of MWCNTs releasing and high noise current were resolved completely. Due to the electrocatalytic effect of MWCNTs and the extractive function, the anodic current of sulfadiazine was highly increased while the anodic potential dropped clearly. Hydrodynamic amperometric method (i-t) was selected for the analysis of sulfadiazine. The aodic currents obtained on MWCNTs/OPPF6-GC modified electrode were linearly responsed against the concentration of sulfadiazine in system in the range of3.3-35.4μmol/L with detection limit of0.21μmol/L. And the interference of matrix was eliminated by background subtraction. A sales sulfadiazine drug was tested by this method.4. Nation was used as dispersive agent and binder of MWCNTs for producing MWCNTs/Nafion-GC. CoⅡTAPc was electrochemically deposited onto the surface of MWCNTs/Nafion-GC to form poly-CoⅡTAPc/MWCNTs/Nafion-GC. The new modified electrode owns advantages such as preventing MWCNTs releasing, long working life, enrichment of sulfadiazie by cation exchanging, avoiding interference of anions (ascorbic acid, urine acid, oxalic acid, etc.) by electrostatic repulsion, reducing the overvoltage of sulfadiazine. The mechanism of synergistic catalytic effect of MWCNTs, CoⅡTAPc and Nafion was discussed strictly. Hydrodynamic amperometric method (i-t) was selected for the analysis of sulfadiazine. The aodic currents obtained on poly-CoⅡTAPc/MWCNTs/Nafion-GC were linearly responsed against the concentration of sulfadiazine in system in the range of0.5-43.5μmol/L with the detection limit of0.17μmol/L. And the interference of matrix was eliminated by background subtraction. Trace level of sulfadiazine in urine samples was tested successfully by this method.