Fabrication of a fluorescent nanoprobe for determination of sulfadiazine after its dispersive solid-phase extraction using magnetic nanocomposite sorbent

[Display omitted] •One-step, non-toxic, Ag2S@L-cysteine was synthesized using the L-cysteine as the sulfur source.•A sensitive Ag2S@L-cysteine fluorescent nanoprobe was designed for sulfadiazine quantification.•The ONCs-Fe3O4@N-GQDs@PEI sorbent for extraction of sulfadiazine was synthesized.•Combination of fluorescence & preconcentration method for trace sulfadiazine analysis.•Application of developed method for quantification of sulfadiazine in cow milk and water samples. A sensitive and non-toxic fluorescent nanoprobe has been designed for the determination of sulfadiazine. Sulfadiazine was separated and preconcentrated by dispersive solid-phase extraction based on the magnetic nanocomposite sorbent of oxidized nanocellulose/polyethyleneimine/nitrogen graphene quantum dots. The quantification of sulfadiazine was based on the decrease in the fluorescence of Ag2S@L-cysteine quantum dots. In optimal conditions, the fluorescence of Ag2S@L-cysteine quantum dots linearly decreases with the increase of sulfadiazine concentration within the range of 2.0–40.0 µg L−1. A limit of detection (LOD) of 0.41 µg L−1 and intra- and inter-day precision of 2.1%, and 4.3%, respectively, at the sulfadiazine concentration of 8.0 µg L−1 (RSD%, n = 7) were obtained. The maximum sorption capacity of the magnetic nanocomposite sorbent for sulfadiazine was found to be 39.0 mg g−1. The proposed procedure was successfully used to extract and quantify sulfadiazine from a variety of samples.