In situ sulfur isotopes (δS and δS) analyses in sulfides and elemental sulfur using high sensitivity cones combined with the addition of nitrogen by laser ablation MC-ICP-MS

The sulfur isotope is an important geochemical tracer in diverse fields of geosciences. In this study, the effects of three different cone combinations with the addition of N₂ on the performance of in situ S isotope analyses were investigated in detail. The signal intensities of S isotopes were improved by a factor of 2.3 and 3.6 using the X skimmer cone combined with the standard sample cone or the Jet sample cone, respectively, compared with the standard arrangement (H skimmer cone combined with the standard sample cone). This signal enhancement is important for the improvement of the precision and accuracy of in situ S isotope analysis at high spatial resolution. Different cone combinations have a significant effect on the mass bias and mass bias stability for S isotopes. Poor precisions of S isotope ratios were obtained using the Jet and X cones combination at their corresponding optimum makeup gas flow when using Ar plasma only. The addition of 4–8 ml min⁻¹ nitrogen to the central gas flow in laser ablation MC-ICP-MS was found to significantly enlarge the mass bias stability zone at their corresponding optimum makeup gas flow in these three different cone combinations. The polyatomic interferences of OO, SH, OOH were also significantly reduced, and the interference free plateaus of sulfur isotopes became broader and flatter in the nitrogen mode (N₂ = 4 ml min⁻¹). However, the signal intensity of S was not increased by the addition of nitrogen in this study. The laser fluence and ablation mode had significant effects on sulfur isotope fractionation during the analysis of sulfides and elemental sulfur by laser ablation MC-ICP-MS. The matrix effect among different sulfides and elemental sulfur was observed, but could be significantly reduced by line scan ablation in preference to single spot ablation under the optimized fluence. It is recommended that the d₉₀ values of the particles in pressed powder pellets for accurate and precise S isotope analysis should be less than 10 μm. Under the selected optimized analytical conditions, excellent agreements between the determined values and the reference values were achieved for the IAEA-S series standard reference materials and a set of six well-characterized, isotopic homogeneous sulfide standards (PPP-1, MoS₂, MASS-1, P-GBW07267, P-GBW07268, P-GBW07270), validating the capability of the developed method for providing high-quality in situ S isotope data in sulfides and elemental sulfur.     

Identification of triacylglycerol using automated annotation of high resolution multistage mass spectral trees

High complexity of identification for non-target triacylglycerols (TAGs) is a major challenge in lipidomics analysis. To identify non-target TAGs, a powerful tool named accurate MSⁿ spectrometry generating so-called ion trees is used. In this paper, we presented a technique for efficient structural elucidation of TAGs on MSⁿ spectral trees produced by LTQ Orbitrap MSⁿ, which was implemented as an open source software package, or TIT. The TIT software was used to support automatic annotation of non-target TAGs on MSⁿ ion trees from a self-built fragment ion database. This database includes 19108 simulate TAG molecules from a random combination of fatty acids and corresponding 500582 self-built multistage fragment ions (MS ≤ 3). Our software can identify TAGs using a “stage-by-stage elimination” strategy. By utilizing the MS¹ accurate mass and referenced RKMD, the TIT software can discriminate unique elemental composition candidates. The regiospecific isomers of fatty acyl chains will be distinguished using MS² and MS³ fragment spectra. We applied the algorithm to the selection of 45 TAG standards and demonstrated that the molecular ions could be 100% correctly assigned. Therefore, the TIT software could be applied to TAG identification in complex biological samples such as mouse plasma extracts.     

A novel polymeric ionic liquid-coated magnetic multiwalled carbon nanotubes for the solid-phase extraction of Cu,Zn-superoxide dismutase

A novel magnetic adsorbent, benzyl groups functionalized imidazolium-based polymeric ionic liquid (PIL)-coated magnetic multiwalled carbon nanotubes (MWCNTs) (m-MWCNTs@PIL), has been successfully synthesized and applied for the extraction of Cu, Zn-superoxide dismutase (Cu, Zn-SOD). The m-MWCNTs@PIL were characterized by X-ray diffraction (XRD), Fourier transform infrared spectrometry (FT-IR), thermal gravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM) and zeta-potential nanoparticles. In this method, the m-MWCNTs@PIL could interact with Cu, Zn-SOD through hydrogen bonding, π-π and electrostatic interactions. The extraction performance of the m-MWCNTs@PIL in the magnetic solid-phase extraction (MSPE) procedure was investigated, coupled with the determination by UV–vis spectrophotometer. Compared with m-MWCNTs@IL and m-MWCNTs, the m-MWCNTs@PIL exhibited the highest extraction capacity of 29.1 mg/g for Cu, Zn-SOD. The adsorbed Cu, Zn-SOD remained high specific activity after being eluted from m-MWCNTs@PIL by 1 moL/L NaCl solution. Besides, the m-MWCNTs@PIL could be easily recycled and successfully employed in the extraction of Cu, Zn-SOD from real samples. Under the optimal conditions, the precision, repeatability and stability of the proposed method were investigated and the RSDs were 0.29%, 1.68% and 0.54%, respectively. Recoveries were in the range of 82.7–102.3%, with the RSD between 3.47% and 5.35%. On the basis of these results, the developed method has great potential in the extraction of Cu, Zn-SOD or other analytes from biological samples.     

Graphene‐Coated ZnO and SiO2 as Supports for CoO Nanoparticles with Enhanced Reducibility

The insertion of a graphene layer between cobalt and a substrate modifies the morphology and the oxidation/reduction properties of supported cobalt particles. Co forms a relatively flat structure on ZnO and SiO₂, whereas individual Co nanoparticles are formed after graphene coating of these substrates. The graphene layer moderates the formation of cobalt oxide in 5×10^?7 mbar O₂ and promotes the reduction of oxidized Co in H₂ at lower temperature. Angle‐resolved XPS measurements indicate that this is mainly a consequence of the restricted interaction of cobalt with the oxide supports. After the low‐pressure redox treatments, the graphene layer maintains a relatively high quality with a small number of defect sites.     

超高效液相色谱-串联质谱法快速检测蔬菜中248种农药残留

采用超高效液相色谱-串联质谱（UHPLC-MS/MS）技术建立了快速检测蔬菜中248种农药残留的分析方法。蔬菜样品采用乙腈提取,盐析后无需净化,缩短了样品前处理的时间。采用正负离子多反应监测（MRM）模式对蔬菜中248种农药残留进行定性和定量分析。245种农药在各自的线性范围内线性关系良好（r>0.99）。除丁硫克百威、灭蝇胺、苯磺隆和二氯喹啉酸4种农药外,其余244种农药在3个添加水平下的平均回收率范围为63.0%～126.4%,相对标准偏差（RSD）范围为0.5%～26.7%,方法的定量限为0.001～0.030 mg/kg。该方法具有简单、快速、灵敏度高、准确度高等优点,适合蔬菜样品中农药多残留的快速检测分析。     

New C20-diterpenoid alkaloids from Aconitum sinomontanum

Two new denudatine-type C₂₀-diterpenoid alkaloids, named sinomontanidines A (1) and B (2), were isolated from the roots of Aconitum sinomontanum Nakai. Their structures were elucidated by extensive analysis of 1D, 2D NMR, and MS data.     

Construction of four d10 coordination polymers containing binuclear rings as building blocks from 4′-(2H-tetrazol-5-yl)biphenyl-4-carboxylic acid

Four coordination polymers based on 4′-(2H-tetrazol-5-yl)biphenyl-4-carboxylic acid (H₂TBPC), [Zn(μ₃-TBPC)(H₂O)]_n (1), [Zn(μ₃-TBPC)(Me₂NH)]_n (2), [Cd(μ₃-TBPC)(bpy)]_n (bpy = 4,4′-bipyridine, 3), and [Cd(μ₄-TBPC)(H₂O)]_n (4), were constructed under hydrothermal conditions. The compounds are composed of M₂(TBPC)₂ binuclear ring as a building block. In 1–3, the binuclear rings are interconnected to three different 2-D networks with the same (4·8²) topology. In 4, the binuclear rings are arranged into a 3-D framework with PtS-type topology. The results revealed that the structural diversity is mainly attributed to the coordination geometries of metal ion, the coordination modes of TBPC^2?, and the auxiliary ligand. The thermal stabilities and luminescent properties of 1–4 have also been studied.     

Organocatalytic,Asymmetric Total Synthesis of (−)‐Haliclonin A

The first total synthesis of the alkaloid (−)‐haliclonin A is reported. The asymmetric synthesis relied on a novel organocatalytic asymmetric conjugate addition of nitromethane with 3‐alkenyl cyclohex‐2‐enone to set the stereochemistry of the all‐carbon quaternary stereogenic center. The synthesis also features a Pd‐promoted cyclization to form the 3‐azabicyclo[3,3,1]nonane core, a SmI₂‐mediated intermolecular reductive coupling of enone with aldehyde to form the requisite secondary chiral alcohol, ring‐closing alkene and alkyne metathesis reactions to build the two aza‐macrocyclic ring systems, and an unprecedented direct transformation of enol into enone.