Nitrogen-doped graphene-ionic liquid-glassy carbon microsphere paste electrode for ultra-sensitive determination of quercetin

The analysis of quercetin (Qu) is of great significance owing to its multiple biomedical effects. In this work, a nitrogen-doped graphene-ionic liquid-glassy carbon microsphere paste electrode (N-GE/GCILE) was constructed for the determination of Qu. Cyclic voltammetry (CV) and square wave voltammetry (SWV) were employed to investigate the electrochemical behavior of Qu. In comparison with unmodified glassy carbon microsphere paste electrode, the modified electrode exhibited better electrocatalytic activity towards Qu. The influencing conditions on sensitivity such as the amount of modifier, accumulation potential and time, and electrolyte pH value were respectively discussed. Under the optimized conditions, two linear ranges of 0.002- 0.1 μM and 0.1–10 μM were obtained, with a detection limit of 1 nM (S/N = 3). The method was applied in Qu determination in blueberry juice with the recoveries of 102.5–105.0%.