To establish a rapid and sensitive ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for the determination of rivaroxaban, apixaban and edoxaban in rat plasma. The analytes and the internal standard (diazepam) were separated on an Acquity UPLC BEH C18 chromatography column (2.1 mm × 50 mm, 1.7 μm) using gradient elution with a mobile phase of acetonitrile and 0.1 % formic acid in water at a flow rate of 0.4 mL/min. The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring mode to monitor the precursor-to-product ion transitions of m/z 436.1 → 145.1 for rivaroxaban, m/z 460.0 → 443.1 for apixaban, m/z 548.2 → 366.1 for edoxaban and m/z 285.2 → 193.1 for diazepam (IS) using a positive electrospray ionization interface. The method was validated over a concentration range of 1.0-200 ng/mL for rivaroxaban, 1.0-100 ng/mL for apixaban and 1.0-500 ng/mL for edoxaban. Total time for each chromatograph was 3.5 min. The intra- and inter-day precision and accuracy of the quality control samples at low, medium, and high concentration levels exhibited relative standard deviations <10.5 % and the accuracy values ranged from -9.9 to 11.3 %. The method was successfully applied to a pharmacokinetic study of rivaroxaban, apixaban and edoxaban in rats.

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Recently, recycling of severely contaminated Nd–Fe–B sintered magnets sludge had drawn considerable attention due to the concern of environmental burden and high cost of traditional wet process recycling. In the present study, we describe a new technology that utilizes distillation, reduction–diffusion (RD), and nanoparticle-doping techniques to prepare recycled Nd–Fe–B sintered magnets from Nd–Fe–B sludge in an efficient and environmentally friendly way. The sludge was purged first to remove both organic impurities and nonmagnetic impurities. The purged products were then treated with calcium-assisted RD reaction to obtain Nd2Fe14B single-crystalline powders. After doping with NdH x or DyH x nanoparticles, the powders were fabricated into recycled Nd–Fe–B sintered magnets by the conventional sintering method. The recycled magnets bear comparable magnetic properties to the original magnets. With 10% doping of NdH x , the energy product of the original magnets is recovered by 88%; with 15% doping of DyH x , the coercivity of the recycled magnets increases by 34% compared to the original magnets. Furthermore, comparison between the conventional recycling method and our new technology demonstrates that our new technology is an economical and environmentally friendly strategy for sintered Nd–Fe–B sludge recycling.

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