Box-Behnken design optimization of a green fluorescence sensor based on S,N-Doped graphene quantum dots for glimepiride determination in pharmaceuticals and biological samples.

In this study, a fluorescent sensor based on sulfur and nitrogen co-doped graphene quantum dots (S,N-GQDs) was developed for the determination of glimepiride in pharmaceutical formulations and spiked human plasma. The spectral characteristics of the sensor were investigated revealing a blue fluorescence emission at 431 nm upon excitation at 362 nm. Stern-Volmer analysis indicated that the quenching of the sensor's fluorescence by glimepiride followed a static quenching mechanism, which was supported by thermodynamic studies. A Box-Behnken experimental design was employed to optimize the factors affecting the quenching process, including pH, buffer volume, S,N-GQDs concentration and incubation time. A quadratic model was obtained, and the optimum conditions were determined. The sensor exhibited a linear response to glimepiride in the range of 0.5-4.0 μg/mL with a limit of detection (LOD) of 0.078 μg/mL. The developed method was validated according to ICH guidelines and successfully applied for the determination of glimepiride in pharmaceutical formulations and spiked human plasma samples. Additionally, the greenness and blueness of the method was evaluated using the AGREE and BAGI metrics revealing a high level of environmental friendliness and analytical practicability posing the developed sensor as a sustainable analytical tool.