Analysis of ß-blockers and ß2-agonists in environmental and biological samples by magnetic solid-phase extraction combined with high-performance liquid chromatography-tandem mass spectrometry.

ß-Blockers and ß2-agonists are commonly prescribed for therapeutic treatments and are also administered to livestock, leading to their presence in both environmental and biological samples. Hence, the development of sensitive, rapid, and reliable analytical methods for the determination of ß-blockers and ß2-agonists in environmental and biological samples is important. In this study, MIL-101(Cr)-NH2 &GO-coated SiO2 /Fe3 O4 magnetic particles were prepared as sorbents for magnetic solid-phase extraction and then combined with high-performance liquid chromatography-tandem mass spectrometry for the analysis of 20 ß-blockers and eight ß2-agonists. The experimental parameters of magnetic solid-phase extraction were studied in detail, and the optimal conditions were established. Under optimal conditions, the limits of detection were in the range of 0.002-0.007 µg/L with enrichment factors of 20.2-24.9. The developed method was successfully applied for the determination of 20 ß-blockers and eight ß2-agonists in river water, human urine, and freeze-dried pork liver powder. Bisoprolol and salbutamol were detected at concentrations of 2.78 mg/L in human urine and 11.5 µg/kg in freeze-dried pork liver powder.

Tunable resistance of MOFs films via an anion exchange strategy for advanced gas sensing.

Because of their ultra-high surface area, large porosity and excellent structural tailorability, metal-organic frameworks (MOFs) are considered as outstanding candidates among sensing materials for hazardous gas detection. However, most of MOFs-based sensing films show weak film adhesion and low conductivity due to the poor formation ability of MOFs films by traditional sensor fabrication methods as well as the intrinsic insulating character of these MOFs. In this work, we propose a novel strategy to directly grow robust gas-sensing films based on pristine MOFs arrays (ZIF-67 nanosheets) in-situ on the surface of ceramic substrates. To improve the conductivity of MOFs arrays, anion-exchange method is applied to couple Prussian blue analogue (PBA) on the surface of ZIF-67 arrays. Structural characterization revealed that this permutation reaction can significantly improve the conductivity of the MOF films while their sheet-like structures can be mainly remained. Benefiting from the robust structure and improved conductivity, the as-designed ZIF-67/PBA films exhibited superior sensing performances such as good reproducibility, high response value (Rg/Ra=11.7), and fast response/recovery speed (5/182 s) towards triethylamine. This work provides a new strategy to fabricate MOFs gas sensors and paves a new way to modulate the conductivity of MOF films.