ZnO nanoparticle-modified ionic liquid-carbon paste electrodefor voltammetric determination of folic acid in food and pharmaceutical samples

In this work, a ZnO/nanoparticles (NPs) modified carbon ionic liquid paste electrode (ZnO/NP/CILPE) was fabricated and used to investigate the electrochemical behavior of folic acid. ZnO/NP/CILPE was prepared by mixing hydrophilic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim]-[PF6])), ZnO/NPs, graphite powder, and liquid paraffin together. The fabricated ZnO/NP/CILPE showed great electrocatalytic ability to the oxidation of folic acid, and an irreversible oxidation peak appeared at 0.75 V (vs. Ag/AgCl) with improved peak current. Under the optimized conditions of pH 9.0, the plot of peak current vs. folic acid concentration consisted of two linear segments with slopes of 1.776and 0.033 μA/μM in the concentration ranges of 0.05–1.5 μM and 1.5–550.0 μM, respectively. The detection limit was 0.01 μM (3σ). The proposed sensor was successfully applied for the determination of folic acid in fortified food and pharmaceutical samples.