Carbon dot based molecularly imprinted polymer for selective fluorometric determination of tetracycline and metronidazole in pharmaceuticals and human plasma

A highly sensitive, selective, and rapid spectrofluorometric method has been developed using fluorescence sensors. This method is based on the highly fluorescent graphene quantum dots coated with silica molecularly imprinted polymers (GQDs-SMIPs) for the determination of tetracycline HCl (TET) and metronidazole (MET). Upon excitation of the GQDs-SMIPs at 260.0 nm for TET and 245.0 nm for MET, strong fluorescence emissions at 292.0 nm were produced for both sensors. Such fluorescence was quenched by the addition of their corresponding molecularly imprinted polymer (MIPs) templates. The quenching effect was linear over the concentration ranges of 15.0-120.0 µM and 15.0-140.0 µM for TET and MET, respectively. Limits of detection (LOD) were 3.55 µM, and 4.48 µM while limits of quantification (LOQ) were 10.75 µM and 13.57 µM for TET and MET, respectively. The fabricated GQDs-SMIPs were characterized using scanning electronic microscopy, Fourier-transform IR spectroscopy, and X-ray diffraction. Selectivity of the method was investigated against potentially interfering substances, including two official impurities of TET and MET. Additionally, this fluorescent technique was successfully applied for the determination of these drugs in pharmaceutical dosage forms and spiked human plasma samples. This approach provides a selective and sensitive fluorometric platform for the determination of the studied drugs in complex matrices and quality control laboratories.