Electrochemical microfluidic chip composed of a cerium oxide-reduced graphene oxide nanocomposite screen printed carbon electrode (SPCE) for the determination of flunitrazepam

Abstract

Due to its long-lasting tranquilizing effect on the human body, the abusive use of flunitrazepam (FNZ) in sexual assault and robbery is commonly encountered. In this study, the assembly of a hybrid nanocomposite comprising cerium oxide (CeO2) nanoparticles and reduced graphene oxide (rGO) nanosheets onto the surface of a screen printed carbon electrode (SPCE) is presented for the sensitive determination of flunitrazepam in various beverages. The properties of the CeO2-rGO nanocomposite were evaluated using various spectroscopic and microscopic techniques, while its electrochemical properties were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). A distinct composite structure with improved current response and electron transfer properties was achieved through the judicious application of rGO nanosheets to facilitate the in situ formation and anchoring of CeO2 nanoparticles. Under optimal conditions, the CeO2-rGO modified SPCE demonstrated flunitrazepam detection to 124 nM with a sensitivity of 40 µA µM−1 cm−2 and exhibited a broad linear response in the concentration range from 0.1 to 300 µM. The quantification of flunitrazepam in spiked beverage samples using CeO2-rGO/SPCE demonstrated satisfactory recovery from 96 to108%. The functionalized sensor was further integrated into a microfluidic chip to prepare a portable flunitrazepam electrochemical platform, in which multiple samples can be processed and reliable analysis can be conducted at low sample volumes. The designed electrochemical microfluidic platform demonstrated desirable performance for flunitrazepam determination, offering a promising solution for on-site determination of illicit drugs in the field of forensic investigations.