NATIVE FLUORESCENCE DETERMINATION OF TETRACYCLINE RESIDUES IN MILK PRODUCTS FOLLOWED BY SILICA-MODIFIED MAGNETIC NANOPARTICLES

In recent years, antibiotics are widely used in food-producing animals not only for treatment of eat, but also therapeutically to maintain health and promot e growth. The presence of antibiotic’s residues in food represents... [ view full abstract ]

In recent years, antibiotics are widely used in food-producing animals not only for treatment of eat, but also therapeutically to maintain health and promot e growth. The presence of antibiotic’s residues in food represents a risk for human health. The concentration of tetracycline in milk and milk products a maximum residue level of 100 μg/kg has been established. Various methods have been used for the determination of antibiotics: high-performance liquid chromatography, spectrophotometry, electrochemistry, fluorescence, mass spectroscopy and etc. Surface modified Fe3O4 are new kind functional materials, which have been widely used in sensing and biotechnology, etc. In this study, magnetite nanoparticles modified with ions Eu(III) was used for development of optical sensors for antibiotics determination.
The magnetic nanoparticles coated with a thin silica oxide layer have been synthesized by combining co-precepitation and hydrothermal treatments. The TEM image of Fe3O4 nanoparticles prepared in aqueous medium reveals a size distribution in the range of 10.0±2.0 nm and silica shell about 2-3 nm. The magnetic dipole attraction decreases quickly with the increase of size of particles and thickness of silica shell.
The using of sulfonate polyelectrolytes (polyvinyl and polystyrene sulfonic acids) allows to obtained core-shell particles with ion-exchange properties. The more high adsorption capacity of europium(ІІІ) was observed for magnetite modified polyvinyl sulfonic acids. Sorption of europium(III) was quite rapid (15 min). Increasing ionic straight (0.01 to 0.5 M) decreased the sorption extent only at higher sorbate to sorbent rations suggesting the dominance of inner-sphere type complexes at low equilibrium tetracycline concentrations. The optimum concentration of europium ions on surface magnetite nanoparticles for the determination of trace amounts of analyte in aqua solution is 2.5•10-5 mol/l for Tetracycline in concentration range 1.0•10-5 M–1.0•10-9 M.
A preliminary series of experiments were obtained in water solution of tetracycline and showed that maximum intensity was achieved for pH close to 7-7.2. Similar measurements run on blank milk samples evidenced a different behavior. In the optimal experimental conditions, linear relationships were obtained, between intensity of fluorescence and concentration of tetracycline in milk samples. Thus magnetic nanoparticles with higher sorption capacity to the studied tetracycline were obtained.