Selective Characterization of Olefins by Paternò–Büchi Reaction with Ultrahigh Resolution Mass Spectrometry

Petroleum olefins play important roles in various secondary processing procedures and are important feedstocks for the modern organic chemical industry. It is quite challenging to analyze petroleum olefins beyond the gas chromatography (GC)-able range using mass spectrometry (MS) due to the difficulty of soft ionization and the matrix complexity. In this work, a Paternò–Büchi (PB) reaction combined with atmospheric pressure chemical ionization and ultrahigh resolution mass spectrometry (APCI–UHRMS) was developed for selective analysis of olefins. Through the PB reaction, CC bonds were transformed into four-membered rings of oxetane with improved polarity so that soft ionization of olefins could be achieved. The systematic optimization of PB reaction conditions, as well as MS ionization conditions, ensured a high reaction yield and a satisfied MS response. Furthermore, a sound scheme was set up to discriminate the coexisting unsaturated alkanes in complex petroleum, including linear olefins, nonlinear olefins, cycloalkanes, and aromatics, making use of their different behaviors during the PB reaction and chemical ionization. The developed strategy was successfully applied to the analysis of olefins in fluid catalytic cracking oil slurry, a complex heavy oil sample. This method extended the characterization of petroleum olefins from lower to higher with high efficiency and selectivity to provide a comprehensive molecular library for heavy petroleum samples and process optimization

Facile Preparation of Poly(lactic acid)/Brushite Bilayer Coating on Biodegradable Magnesium Alloys with Multiple Functionalities for Orthopedic Application

Recently magnesium and its alloys have been proposed as a promising next generation orthopedic implant material, whereas the poor corrosion behavior, potential cytotoxicity, and the lack of efficient drug delivery system have limited its further clinical application, especially for the local treatment of infections or musculoskeletal disorders and diseases. In this study, we designed and developed a multifunctional bilayer composite coating of poly­(lactic acid)/brushite with high interfacial bonding strength on a Mg–Nd–Zn–Zr alloy, aiming to improve the biocorrosion resistance and biocompatibility of the magnesium-based substrate, as well as to further incorporate the biofunctionality of localized drug delivery. The composite coating consisted of an inner layer of poly­(lactic acid) serving as a drug carrier and an outer layer composed of brushite generated through chemical solution deposition, where a facile pretreatment of UV irradiation was applied to the poly­(lactic acid) coating to facilitate the heterogeneous nucleation of brushite. The in vitro degradation results of electrochemical measurements and immersion tests indicated a considerable reduction of magnesium degradation provided the composite coating. A systematic investigation of cellular response with cell viability, adhesion, and ALP assays confirmed the coated Mg alloy induced no toxicity to MC3T3-E1 osteoblastic cells but rather fostered cell attachment and proliferation and promoted osteogenic differentiation, revealing excellent biosafety and biocompatibility and enhanced osteoinductive potential. An in vitro drug release profile of paclitaxel from the composite coating was monitored with UV–vis spectroscopy, showing an alleviated initial burst release and a sustained and controlled release feature of the drug-loaded composite coating. These findings suggested that the bilayer poly­(lactic acid)/brushite coating provided effective protection for Mg alloy, greatly enhanced cytocompatibility and bioactivity, and, moreover, possessed local drug delivery capability; hence magnesium alloy with poly­(lactic acid)/brushite coating presents great potential in orthopedic clinical applications, especially for localized bone therapy