An ultra performance liquid chromatography (UPLC) method was established for the simultaneous determination of cimaterol, salbutamol, terbutaline, and ractopamine in feed. Target compounds were extracted with methanol and centrifuged. The supernatant was then transferred and concentrated, and applied to a solid phase extraction MCX cartridge for clean-up before UPLC analysis. The calibration curves for the four b-agonists were good linear in concentration range of 0.05-1.0 lg mL -1 with the correlation coefficients (r) over 0.999. The average recoveries were in the range of 90.1-101.4% with relative standard deviation values lower than 8.0%.
The integration of molecular imprinting technique and solid-phase extraction (SPE) implements an effective alternative for sample pre-concentration in the determination and analysis of veterinary drug/pesticide residues. Herein, we reports a preliminary study on the preparation of streptomycin imprinted polymers on the surface of silica micro-spheres (with an average size of 50μm) and nano-spheres (with an average size of 500nm) via sol gel method. A mixed solution of tetrahydrofuran, ethanol and water (volume ratio is 7:1:1) was choose as dispersion agent, 3-aminopropyltriethoxysilane and phenyltriethoxysilane as functional monomers, and tetraethyl orthosilicate as cross-linker, while ammonia solution served as catalyst in the polymerization process. Scanning electron microscopic characterization was employed, suggesting that activating time exerts important influences on the morphology of activated silica micro-spheres, and also resultant molecular imprinted polymers (MIPs). The absorption capacity and selectivity of the obtained two MIPs were also evaluated for streptomycin and its analogue compounds in water samples. The results illustrate that the streptomycin-imprinted silica micro-spheres (MMIP) exhibited both larger absorption capacity and higher selectivity than those of silica nano-spheres (NMIP). The variant analytical performance might result from inadequate polymerization on the surface of silica nano-spheres.
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