Synthesis Of 1-alkyl-2, 3-dimethylimidazole Ionic Liquid And Its Application As Biosensor Medium

Five novel 1-alkyl-2,3-dimethylimidazole hexafluorophosphate ionic liquids were synthesized successfully by solvent-free method based on 1,2-dimethylimidazole using a similar procedure. The total yield of ionic liquid was about 89.0 %. Appropriate amount of acetone was added the ionic liquid to dilute it until its viscidity was almost same as that of water, then added activated carbon to remove color compounds. Absorption spectrum of the ionic liquid acetone solution was measured on the ultra visible spectrometer, no obvious absorption peak was found between 400nm and 800nm. The UV, IR and 1H-NMR data of the products are in good agreement with their chemical structure.Ionic liquid can dissolve in acetone, methanol and acetonitrile, but difficult to dissolve in water, toluene and carbon tetrachloride. Ionic liquid has a wide electrochemistry window more than 4V. The experiment also indicated that the density of ionic liquid decreased and the viscidity increased with increasing the carbon chain of the substitute group. It was found that the species of ionic liquids effected on electrochemistry performance of the enzyme electrode. Only enzyme electrodes based on 1-amyl-2,3-dimethylimidazole hexafluorophosphate ionic liquid can preserve good enzyme activity and produce a sensitive electrochemistry respond.The modified carbon paste electrode containing ionic liquid was prepared by mixing cabon powder and 1-amyl-2,3-dimethylimidazole hexafluorophosphate in which the ionic liquid instead of paraffine used commonly. The performance of ionic liquid modified carbon paste electrode was studied through Cyclic Voltammogram and Electrochemical Impedance Spectra method by potassium ferricyanide probe. The result illustrated that the electrode had better conductive capacity compared with traditional carbon paste electrode due to the conductive capacity of ionic liquid. The electrode also shows favorable reversibility in potassium ferricyanide solutuon. Hb was entraped into SA to fabricate biosensor which can be used to determine concentration of hydrogen peroxide and sodium nitrite in synthesized samples. The linear function were Y(10-4A)=0.3143X (mmol/L)-0.6571, R2=0.9959 for hydrogen peroxide.Ionic liquid was developed as medium to fabricate blank working electrode and catalase electrode in this work. Among these blank electrodes, background current was only several nanoamps. It was found the species of ionic liquids effected on electrochemistry performance of the enzyme electrode obviously. Only enzyme electrodes based on 1-amyl-2,3- dimethylimidazole hexafluorophosphate ionic liquid can preserve good enzyme activity and produce a sensitive electrochemistry respond. Moreover, the above enzyme electrode was very stable, its electrochemistry properties remain almost unchanged for 30 days at 4℃. In pH 7.0 phosphate buffer solution, reductive peak current of the enzyme electrode increased linearly with increase of hydrogen peroxide from 3.17 to 12.4×10-6 mol/L. The detection limit of proposed method was 1.1×10-6 mol/L. It has successfully been applied to determination of trace hydrogen peroxide in environmental water.