Reusable electrochemical sensor for quinine detection via β-cyclodextrin-based indicator displacement assay

Quinine, a natural alkaloid discovered several centuries ago, has been widely used as an anti-malarial drug and a bitter food additive. However, overconsumption would result in quinine poisoning. Herein, a simple, reusable, and cost-effective electrochemical sensor was presented for quinine detection, utilizing indicator displacement assay (IDA) with β -cyclodextrin/poly( N -acetylaniline)/graphene-modified glassy carbon (GC) electrode. Graphene was deposited onto the electrode surface through cyclic voltammetry (CV) electroreduction to enhance the electron transfer properties. The poly( N -acetylaniline) film was introduced to inhibit non-special absorption of methylene blue (MB). The β -cyclodextrin ( β -CD) molecules were modified on the electrode surface using chronoamperometry to provide a binding site for MB(probe)/quinine(target). Through competitive host–guest interaction, quinine displaced the indicator MB molecule from the β -CD cavity. Differential pulse voltammetry (DPV), cyclic voltammetry (CV), proton nuclear magnetic resonance ( 1 H NMR), scanning electron microscopy (SEM), electrochemical impedance analysis (EIS), and Fourier transform infrared (FTIR) were employed to verify the successful construction of sensor. The sensor also displayed superior selectivity over the common interfering molecules, satisfactory reusability upon reincubation in MB solution, good reproducibility using the consistent fabrication method, and high stability with an acceptable peak current decrease within 21 days. It is worth pointing out that this is the first time to integrate host–guest recognition with an electrochemical assay for quinine determination. In light of the IDA design strategy, the proposed sensing strategy may inspire innovative engineering methods for molecule detection in the fields of clinical analysis, food safety, and environmental monitoring.