Fabrication And Analytical Application Of Ionic Liquid BPPF₆ Modified Carbon Paste Electrode

Room temperature ionic liquids (RTILs) are generally regarded as a compound entirely composed of organic cations and various inorganic anions that exist in the liquid state around room temperature. RTILs have excellent physical and chemical properties, which can be applied in the field of analytical chemistry. RTILs can be used either as supporting electrolyte or modifier for chemically modified electrode. Since electroanalysis has inherent advantages such as lower detection limit and wider dynamic range, it can be used to investigate the electrochemical behaviors of small molecules.A room temperature ionic liquids (RTILs) modified carbon paste electrode (CPE) was constructed based on the substitute of paraffin with N-butylpyridinium hexafluorophosphate (BPPF6) to mix with graphite powder. The optimal conditions for preparation were selected and the surface morphologies of the CILE were scanned by a scanning electron microscopy. The electrochemical behaviors of the CILE was investigated by using K3[Fe(CN)6] as probe and compared with that of traditional CPE. The result showed that the electrochemical response was greatly improved with the high conductivity of RTILs and the modified CILE showed good mechanic property and stability. The electrochemical behaviors of ascorbic acid, dopamine, rutin, uric acid and p-nitrophenol on the CILE was investigated by the cyclic voltammetry and chronocoulometric method. The results indicated that the CILE showed excellent catalytic ability to the small molecules. Based on the changes of their electrochemical responses such as peak currents, potentials with the change of the scan rates, some electrochemical parameters such as the charge transfer coefficientα, the electron transferred number n, the electrode reaction standard rate constant ks and the diffusion coefficient D etc were calculated. Under the optimal conditions, the peak current had a linear relationship with the concentration of small molecules in a certain range. The influences of coexisting substances such as metal ions and amino acids etc were tested. The results showed that most of them didn't interfere with the determination. These methods were further applied to the determination of samples with satisfactory results.