Polyamidoamine dendrimer-armed fluorescent magnetic nanoparticles for sensitive and selective determination of nitrite in beverages

Herein, we report a novel solid-phase spectrofluorimetric method for the determination of nitrite. The fluorophore 1-naphthylamine-4-sulfonic acid was covalently bonded to the surface of magnetic silica nanoparticles using polyamidoamine dendron structures as spacers. The introduction of dendritic arms significantly improved the fluorescence intensity. Compared with the conventional solid-phase spectrofluorimetry based on physical adsorption of the derived fluorescent reagents to the sorbents, our method exhibited better selectivity and could directly analyze nitrite in real color samples without pretreatment. The concentrations of nitrite in beer, peach juice and grape juice were determined to be 0.146, 0.165 and 0.110 mg/L, respectively, which is in good agreement with capillary electrophoresis results. Moreover, our novel method circumvented the disadvantage of the Langmuir-type isotherm of conventional solid-phase spectrofluorimetry and offered a detection limit of 10 ng/L for a 500-mL fortified sample with a recovery of 90.5%. These promising results suggest that our strategy can be applied for the facile, sensitive and selective detection of nitrite in complicated matrices.