An Electrochemical Sensor Based on Ionic Liquid-Multiwall Carbon Nanotubes/Graphite Paste Electrode for Simultaneous Determination of Epinephrine and Xanthine in Pharmaceutical and Biological Samples

A graphite paste electrode (GPE) modified with 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) and multi-walled carbon nanotube (MWCNT), was prepared for simultaneous voltammetric determination of epinephrine (EN) and xanthine (XN). The prepared electrode (BMIMPF6–MWCNT/GPE) showed an excellent catalytic activity in the electrochemical oxidation of EN and XN, leading to remarkable enhancements in the corresponding peak currents and lowering the peak potentials. The peaks current of linear sweep voltammograms (LSV) of EN and XN increased linearly with their concentration in the ranges of 0.30–60 µmol L−1 EN and 0.20–45 µmol L−1 XN in 0.1 M phosphate buffer solution (pH 7.0). The effects of both scan rate and pH on the anodic peak height of the EP oxidation and XN were discussed. The lowest detection limits (S/N= 3) were 0.209 µmol L−1 and 0.143 µmol L−1 for EP and XN, respectively. Therefore, the applicability of the voltammetric biosensor was demonstrated by simultaneous determination of EP and XN in human urine, human blood serum and ampoule. This modified electrode showed a good stability and repeatability during experiments.