Determination Of Some Small Molecules On Ionic Liquid Modified Carbon Paste Electrode

A room temperature ionic liquid (RTIL) modified carbon paste electrode (CPE) was constructed based on the substitute of paraffin with N-butylpyridinium hexafluorophosphate (BPPF₆) to mix with graphite powder. The electrochemical behaviors of hydroquinone, metol, 3, 4-dihydroxy benzoic acid, L-tryptophan on the IL-CPE was investigated by the cyclic voltammetry and chronocoulometric method. The results indicated that the IL-CPE 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 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.Moreover, a hydrophilic ionic liquid of 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM] BF₄) was used as modifier to make a new kind of ionic liquid modified carbon paste electrode (IL-CPE), which was further characterized by different methods including electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and scanning electron microscope (SEM). The electrochemical behaviors of metol on the IL-CPE were investigated by the cyclic voltammetry and chronocoulometric method. The results indicated that the CILE showed excellent catalytic ability to metol. Some electrochemical parameters were calculated. These methods were further applied to the determination of samples with satisfactory results.