Ratiometric Electrochemical Sensor Using Chitosan@Rhodamine B/Gold Nanoparticles (AuNPs) for the Sensitive Determination of Rutin by Differential Pulse Voltammetry (DPV)

Internal reference probes can effectively eliminate internal and external interferences. Hence, finding a suitable internal reference probe is the key to ratiometric electrochemistry. In this study, a simple and sensitive ratiometric electrochemical sensor for the determination of rutin was prepared for the first time using rhodamine B (Rh B) as an internal reference probe. The modified electrochemical sensor was constructed by electrodepositing gold nanoparticles (AuNPs) on a glassy carbon electrode followed by drop-coating chitosan-immobilized rhodamine B (CS@Rh B). Rh B has a dual function in that it has a stable electrochemical signal (1.18 V) (vs. Ag/AgCl) that is completely separated from the oxidation peak of rutin (0.52 V) to serve as an internal reference probe. At the same time, it synergistically enhances the electrochemical signal of rutin with AuNPs. When differential pulse voltammetry was used for the determination of rutin, the current ratio of IRutin/IRh B was employed as the signal for rutin determination with a wide linear range (0.1 to 70 μM) and a low detection line (0.028 μM). The recoveries for the determination of rutin in Coreopsis tinctoria and Buckwheat tea were 95.4%–106% and 95.3%–104%, respectively. This work successfully demonstrated the feasibility of Rh B as an internal reference probe.