Evaluation of Carbon Nanotube Paste Electrode Modified With Copper Microparticles and Its Application to Determination of Quercetin

摘要

A carbon nanotube paste electrode modified with copper microparticles (CNTPE-Cu) was constructedand used for determination of quercetin in apple juice. The optimal content of carbon nanotubes/coppermicroparticles in the paste electrode was evaluated using differential pulse voltammetry, which was6% (w/w) copper microparticles. This electrode was characterized by scanning electron microscopy(SEM) and electrochemical impedance spectroscopy (EIS). The SEM result shows the presence ofCNTs and small plates due to copper microparticles. From EIS analysis is possible to observeincreased charge-transfer resistance (Rtc) for CNTPE-Cu when compared to the carbon nanotube paste4-/3- electrode for the reaction [Fe(CN)6] . This is probably due to the formation of a passive oxide layer(CuO) on the surface of the CNTPE-Cu, which prevents electron transfer. Finally, the performance ofCNTPE-Cu in the determination of quercetin was compared to CNTPE. The lower limit of detectionobtained with CNTPE-Cu is attributed to the formation of the quercetin-Cu(II) complex on theelectrode surface. The determination of quercetin in apple juice concurred with the spectrophotometricmethod at a 95% confidence level with recoveries between 98.9 and 102.8%.