A novel molecularly imprinted polymer that could selectively recognize tetracyclines in milk powder was synthesized using a metal-organic framework as a support material, tetracycline as template molecule, and 3-aminophenylboronic acid as a functional monomer and a cross-linking agent. The novel molecularly imprinted polymer was characterized by Fourier transform infrared spectrometry, transmission electron microscopy, X-ray diffractometry, thermogravimetric analysis, and N adsorption/desorption measurements. The adsorption isotherms, adsorption kinetics, adsorption thermodynamics, and selective adsorption experiments of the novel molecularly imprinted polymer to tetracycline were also studied. The novel molecularly imprinted polymer was used as dispersant of matrix solid-phase dispersion to extraction tetracyclines. After that, the tetracyclines extracted from milk powder were determined by ultra high performance liquid chromatography with tandem mass spectrometry. Under the optimal conditions, the detection limits of tetracyclines were 0.217-0.318 ng/g. The relative standard deviations of intra- and interday precision ranged from 3.8 to 6.9% and from 2.8 to 7.4%, respectively. In all three concentration levels (1.0, 10, 50 ng/g), the recoveries of tetracyclines ranged from 84.7 to 93.9%. The method was successfully applied to the determination of tetracyclines in milk powder.

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Summary Pt‐doped proton exchange membranes (PEMs) can effectively reduce oxygen permeation and thus enhance the durability of PEM, which have been widely employed in fuel cell. However, until now, no study related to the oxygen permeation capability of Pt‐doped PEM during actual operation has been reported. In this article, the oxygen permeation of Pt‐doped PEM under fuel cell operation is analyzed by the embedded microelectrode method. The test results show that the anode/cathode pressure difference is the main influencing factor for the oxygen permeation of the PEM: the oxygen permeation behavior of the Pt‐free PEM exists and gradually decreases with an increase in the anode/cathode pressure difference, and the oxygen permeation behavior of the PEM disappears when the pressure difference exceeds 60 kPa. Due to the presence of Pt nanoparticles, the Pt‐doped PEM exhibits negligible oxygen permeation in the anode/cathode pressure difference from −100 kPa to 100 kPa and demonstrates excellent oxygen consumption ability.