Enrichment of adenosine using thermally responsive chromatographic materials under friendly pH conditions

A thermally responsive boronate affinity chromatographic material, which showed thermal sensitivity, had been successfully applied for the enrichment and separation of cis‐diol‐containing compounds, and the capture and release process could be facilitated by adjusting the temperature. However, in this system, the pH of the mobile phase must be higher than 9.8, and alkaline media can lead to the degradation of labile compounds; the use of silica beads also limits its use. In this study, thermally responsive boronate affinity chromatographic material, namely poly(N‐isopropylacrylamide‐co‐N‐acryloyl‐3‐aminophenylboronic acid) grafted silica, was successfully prepared by atom transfer radical polymerization. Its structure was confirmed by IR spectroscopy and the graft ratio was 20.8%, determined by thermogravimetric analysis. Furthermore, the capture/release of adenosine, a cis‐diol, was performed from pH 5.0–9.0 and 10–50°C. The elution of adenosine was remarkably retarded at decreased temperatures and adenosine could be captured completely at 10°C at pH values of 5.0–9.0. The enrichment of adenosine could be achieved by simply changing the temperature from 10 to 50°C. Therefore, this material not only improved the stability of the silica, but was also suitable for the capture of oxidation‐sensitive biological analytes. Moreover, it could be used for the enrichment of cis‐diol‐containing compounds in LC with MS.     

Correlation between electron delocalization and structural planarization in small water rings

The discovery of the covalent‐like character of the hydrogen bonding (H‐bonding) system [Science 342 , 611(2013)] has promoted a renewal of our understanding of the electronic and geometric structures of water clusters. In this work, based on density functional theory calculations, we show that the preferential formation of a stable quasiplanar structure of (H₂O)_n(n = 3–6) is closely related to three kinds of delocalized molecular orbitals (MOs; denoted as MO‐I, II, and III) of water rings. These originate from the 2p lone pair electrons of oxygen (O), the 2p bond electrons of O and the 1s electrons of H and the 2s electrons of O and 1s electrons of H, respectively. To maximize the orbital overlaps of the three MOs, geometric planarization is needed. The contribution of the orbital interaction is more than 30% in all the water rings according to our energy decomposition analysis, highlighting the considerable covalent‐like characters of H‐bonds. © 2015 Wiley Periodicals, Inc.     

Improved Photocatalytic Activity and Stability of Nano‐sized Ag/Ag2CO3 Plasmonic Photocatalyst by Surface Modification of Fe(III) Nanocluster

The surface modification of Ag/Ag₂CO₃ with Fe(III) ions has been achieved through simply photoreduction‐impregnation method. The obtained products were characterized by means of X‐ray diffraction (XRD), scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and UV‐vis absorption spectroscopy. Under visible‐light irradiation (γ>420 nm), the Fe(III)/Ag/Ag₂CO₃ sample displays a higher photocatalytic activity and stability than pure Ag₂CO₃ and Ag/Ag₂CO₃ samples for the degradation of methyl orange (MO). The improved photocatalytic activity and stability of this ternary system could be ascribed to the synergetic effect between Ag nanoparticles and Fe(III) nanocluster. The metallic Ag nanoparticles cause an obviously enhanced visible‐light absorption to produce more photogenerated charges, while the Fe(III) works as an active site for the following oxygen reduction to reduce the recombination rate of photogenerated electrons and holes.     

Development and Investigation of a Mesh-Electrode Linear Ion Trap (ME-LIT) Mass Analyzer

A mesh-electrode linear ion trap (ME-LIT) mass analyzer was developed and its performance was primarily characterized. In conventional linear ion trap mass analyzers, the trapped ions are mass-selected and then ejected in a radial direction by a slot on a trap electrode. The presence of slots can strongly affect the electric field distribution in the ion trapping region and distort the mass analysis performance. To compensate for detrimental electric field effects, the slot is usually designed and fabricated to be as small as possible, and also has very high mechanical accuracy and symmetry. A ME-LIT with several mesh electrodes was built to compensate for the effects caused by slots. Each mesh electrode was fabricated from a plate electrode with a relatively large slot and the slot was covered with a conductive mesh. Our preliminary experimental results show that the ME-LIT could considerably diminish the detrimental electric field effects caused by slots, and increase the mass resolving power and ion detection efficiency. Even with 4-mm-wide slots, a mass resolution in excess of 600 was obtained using the ME-LIT. Mass resolution could be remarkably improved using mesh electrodes in ion traps with asymmetric electrodes. The stability diagram of the ME-LIT was mapped, and highly efficient tandem mass spectrometry was demonstrated. The ME-LIT was qualified as a LIT mass analyzer. The ME-LIT can improve the mass resolution and decrease the requirements of mechanical accuracy and symmetry of slots, so it shows potential for a wide range of practical uses.

Preparation and characterization of polyphenylene sulfide-based chelating fibers

A series of novel chelating fibers containing sulfur, nitrogen, oxygen heteroatoms were prepared via the functionalization of chloromethylated polyphenylene sulfide （CMPPS）. The structures, micromorpholo- gy and physicochemical properties of these fibrous adsorptive materials were characterized by FT-IR, elementary analysis, TG and SEM-EDS. The results show that chelating fibers had high functional group contents （3.94 mmol/g for thiourea, 3.85 mmol/g for mercapto, 5.00 mmol/g for methylamine and 6.07 mmol/g for ethylenediamine, respectively）. Owing to the unique matrix of polyphenylene sulfide fiber, these fibrous adsorbents possess excellent thermostability. This synthetic method proved a simple and efficient way for the preparation of chelating fibers.