A Novel Flow-through Fluorescence Optosensor For The Sensitive Determination Of Tetracycline

Tetracyclines (TCs) are broad-spectrum antibiotics which have been widely used in the prevention and treatment of infectious diseases, diagnosis and treatment of cancer, as well as food additives for growth promotion in poultry raising and fish farming. The intensive use of these antibiotics has raised questions about the residual of antibiotics in organisms and in the environment. Tetracycline residue can endanger human health, enhance the bacterial resistance, and the emerging super bacterium is the consequences of antibiotics abuse. Therefore, it is necessary to develop fast and sensitive analysis methodologies for the determination of tetracyclines.Solid surface fluorescence integrates solid-phase extraction and solid-phase fluorescence detection, determines the fluorescence intensity of solid substrate after analyte adsorption, which possesses the virtue of high sensitivity and favorable selectivity. The combination of the present system with a sequential injection system facilitates the flow control and online preconcentration of the target followed by solid surface fluorescence detection.We choose Sephadex G-50as solid substrate for its high optical transparency. By adding surfactants in sample solution, the formation of admicelle on the solid surface helps the adsorption of the analyte. TC derivative enters the hydrophobic nuclear of admicelle on the solid surface via hydrophobic force, realizes its adsorption and preconcentration. As free micelle in the solution, the admicelle on Sephadex G-50can also enhance the fluorescence intensity of the adsorbed analyte. The results of FT-IR and SEM demonstrate admicelle on the solid substrate regulates the adsorption of analyte. Admicelle has the advantage of high adsorption capacity, and this study gave rise to an adsorption capacity of125mg g-1for the cationic surfactants CTAB on Sephadex G-50for tetracycline derivatives.A flow-through fluorescence optosensor with Sephadex G-50microbeads as solid support is developed for the sensitive determination of tetracycline. The fluorescent TC derivative encapsulated in CTAB admicelle structures is retained onto the surface of the microbeads packed into a fluorescent flow cell in a flow system, followed by measurement of the native fluorescence of the TC derivative on the bead surface. Under the optimal conditions, a linear calibration graphs is obtained within a range of3to500μg L-1, along with a detection limit of1.0μg L-1(3a, n=11), RSD3.8%(50μg L-1, n=11). The present solid surface fluorescence optosensor provides a22-fold improvement on the detection sensitivity for TC in comparison with that derived by using fluorimetric protocol with detection in aqueous medium. The retained TC derivative is easily stripped off with DI water from the bead surface by breaking-down the micelle structure. This offers a convenient and effective way for the regeneration of the used solid support with DI water as a carrier. The feasibility of this flow-through fluorescence optosensor is evaluated by analyzing TC in a commercial drug tablet and surface water samples.