Green and Sustainable Determination of Fluconazole Using a Box–Behnken Optimized Zn-CQDs Fluorescence Quenching Approach: Application to Pharmaceutical Formulations and Pharmacokinetic Studies

In this study, a sensitive and selective analytical method has been developed for the determination of fluconazole, a widely used antifungal agent, using Zn-doped carbon quantum dots as a fluorescent probe. A strong emission from the Zn-CQDs was observed at 440 nm upon excitation at 330 nm, which was quenched in the presence of fluconazole due to a static quenching mechanism, as revealed by Stern–Volmer analysis and thermodynamic studies. The Stern–Volmer constant and the association constant were found to be 6.25 × 10⁴ and 8.47 × 10 ⁴ M⁻¹, respectively, indicating a strong interaction between fluconazole and Zn-CQDs. Factors affecting the quenching process, such as pH, incubation time, and the concentration of Zn-CQDs, were optimized using a Box–Behnken design. The developed method was validated according to ICH M10 guidelines, demonstrating excellent linearity in the range of 0.1–3.0 μg/mL and high sensitivity with LOD value of 0.03 μg/mL. The method was successfully applied to analyze fluconazole in rabbit plasma and pharmaceutical formulations, and the pharmacokinetic parameters were determined using noncompartmental analysis. Finally, the greenness and whiteness of the method were assessed showcasing its low environmental impact and high sustainability, posing advantages over the reported fluorometric and chromatographic methods.