Validated green fluorescent nanosensor for barnidipine determination using lupine-derived multi-doped carbon quantum dots

We present a green analytical fluorescence method for the selective determination of barnidipine, an antihypertensive drug, based on nitrogen, sulfur, and phosphorus co-doped carbon quantum dots (NSP-CQDs). The CQDs were synthesized via a rapid microwave-assisted approach using Lupinus albus seeds as a sustainable precursor, yielding highly fluorescent nanoparticles with a quantum yield of 25.2 %. The fluorescence of NSP-CQDs, with an emission maximum at 409 nm (λ_ex = 320 nm), was efficiently quenched by barnidipine through an inner filter effect. The developed nanosensor enabled quantitative analysis of barnidipine with a linear response in the range of 25.0–250.0 μM, a detection limit of 4.91 μM, and high accuracy, achieving a mean recovery of 99.81 % in pharmaceutical dosage forms. Analytical performance was validated in terms of sensitivity, selectivity, precision, and accuracy, confirmed the reliability of the assay in pharmaceutical preparations. Greenness and practical sustainability of the method were assessed by Complex Modified GAPI and Blue Applicability Grade Index (BAGI) metrics, underscoring its compliance with green analytical chemistry principles. This work demonstrates the integration of eco-friendly nanomaterials into pharmaceutical analysis, providing a novel, reliable, and environmentally sustainable tool for fluorescence-based drug determination.