Application Of The Ionic-liquid-based Electrochemical Sensors In Food Analysis

Ionic liquids have been widely used in electrochemical analysis due to their good properties such as high conductivity,wide electrochemical window,high thermal and chemical stability and designability.This work constructed a series of electrochemical sensors using different types of ionic liquids and the carboxylic multi-walled carbon nanotubes（MWCNTs-COOH）which have better conductivity as the main electrode modified materials.These electrochemical sensors were used to analyze the real food samples.The main contents of the work are as follows:（1）A sensitive electrochemical glucose biosensor based on carboxylic multi-walled carbon nanotubes（MWCNTs-COOH）/ionic liquid（[BMIM]PF₆）film modified glassy carbon electrode has been developed and its characteristics were investigated by cyclic voltammetry（CV）,differential pulse voltammetry（DPV）and electrochemical impedance spectroscopy（EIS）.The results showed that hydrogen peroxide（H₂O₂）generated during the enzymatic reaction of GOx with glucose could be decomposed by catalase,resulting in the higher sensitivity.Finally,the proposed biosensor was successfully applied for the determination of glucose in drink and food samples.（2）A new copper（Ⅱ）solid-state ion-selective electrode（ISE）has been prepared by directly using an amino functionalized ionic liquid as the sensing material.A solid-state ionic liquid（tetrabutylphosphonium bis（trifluoromethyl sulfonyl）imide（TBPNTf₂））was selected to replace paraffin that have poor electrical conductivity and used as a binder;carboxylic multi-walled carbon nanotubes（MWCNTs-COOH）was used as an electrode modification material.The use of both MWCNTs-COOH and IL improves greatly the conductivity and the transduction of chemical signal to electrical signal.The effects of the components of modified electrode,the pH values and activation time were also studied by potentiometry.Finally,the proposed electrode was applied to determine copper in food samples.The accuracy of the results was comparable to those obtained by atomic absorption spectroscopy.The results of the experiment were satisfactory.（3）A new mercury（Ⅱ）solid-state ion-selective electrode has been developed by using a thiol functionalized ionic liquid as the sensing material.The effects of the components of modified electrode,the pH values and activation time were also studied by potentiometry.The results suggested that the proposed electrode had good analytical performance and showed obvious response to mercury and had good selectivity toward Hg（II）ions.Finally,the proposed electrode was successfully applied to determine total mercury in real food samples.Meanwhile,the accuracy of the results was comparable to those obtained by mercury analyzer.The results show good agreement between the two methods.