An efficient synthesis of 2-(guaiazulen-1-yl)furan derivatives via intramolecular Wittig reactions

An efficient and mild synthesis of 2-(guaiazulen-1-yl)furans,starting from easily accessible 1-(3-aryl-2-cyanopropenoyl) guaiazulenes,tributylphosphine and acyl chlorides,is described.The strategy employs the intramolecular Wittig protocol as a key step to append the crticial furan ring,leading to the highly functional furans in good yields.     

微波消解-浊点萃取-火焰原子吸收光谱法测定空心胶囊中铬含量

研究了微波消解-浊点萃取-火焰原子吸收光谱法(FAAS)测定空心胶囊中痕量铬的方法。空心胶囊通过微波消解,以二乙基二硫代氨基甲酸钠(DDTC)为络合剂络合消解液中铬(Ⅵ),非离子表面活性剂Triton X-114为萃取剂,结合FAAS测定空心胶囊中痕量铬,与《中国药典》(2010版)检测方法具有较好一致性。考察了溶液的pH值、络合剂和表面活性剂浓度、平衡温度和时间等条件对浊点萃取效果的影响。在最优条件下,铬(Ⅵ)线性范围为0～10μg/mL,检出限(3σ)为7.6ng/mL,相对标准偏差为1.5%(n=10),回收率在95%～102%之间。方法灵敏度高,重复性好,适合于胶囊中铬的日常检测。     

Magnetic separation of heavy metal ions and evaluation based on surface‐enhanced Raman spectroscopy: Copper(II) ions as a case study

A new approach was developed for the magnetic separation of copper(II) ions with easy operation and high efficiency. p‐Mercaptobenzoic acid served as the modified tag of Fe₂O₃@Au nanoparticles both for the chelation ligand and Raman reporter. Through the chelation between the copper(II) ions and carboxyl groups on the gold shell, the Fe₂O₃@Au nanoparticles aggregated to form networks that were enriched and separated from the solution by a magnet. A significant decrease in the concentration of copper(II) ions in the supernatant solution was observed. An extremely sensitive method based on surface‐enhanced Raman spectroscopy was employed to detect free copper(II) ions that remained after the magnetic separation, and thus to evaluate the separation efficiency. The results indicated the intensities of the surface‐enhanced Raman spectroscopy bands from p‐mercaptobenzoic acid were dependent on the concentration of copper(II) ions, and the concentration was decreased by several orders of magnitude after the magnetic separation. The present protocol effectively decreased the total amount of heavy metal ions in the solution. This approach opens a potential application in the magnetic separation and highly sensitive detection of heavy metal ions.     

Dispersive liquid–liquid microextraction combined with online preconcentration MEKC for the determination of some phenoxyacetic acids in drinking water

A fast and simple technique composed of dispersive liquid–liquid microextraction (DLLME) and online preconcentration MEKC with diode array detection was developed for the determination of four phenoxyacetic acids, 2,4,5‐trichlorophenoxyacetic acid, 2,4‐dichlorophenoxyacetic acid, 2,6‐dichlorophenoxyacetic acid, and 4‐chlorophenoxyacetic acid, in drinking water. The four phenoxyacetic acids were separated in reversed‐migration MEKC to the baseline. About 145‐fold increases in detection sensitivity were observed with online concentration strategy, compared with standard hydrodynamic injection (5 s at 25 mbar pressure). LODs ranged from 0.002 to 0.005 mg/L using only the online preconcentration procedures without any offline concentration of the extract. A DLLME procedure was used in combination with the proposed online preconcentration strategies, which achieved the determination of analytes at limits of quantification ranging from 0.2 to 0.5 μg/kg, which is far lower than the maximum residue limits established by China. The satisfactory recoveries obtained by DLMME spiked at two levels ranged from 67.2 to 99.4% with RSD <15%, making this proposed method suitable for the determination of phenoxyacetic acids in water samples.     

Crystal structure of a novel complex [Co(3,3′-bpbc)(H2O)3]·H2O

A novel coordination polymer constructed with [Co(3,3′-bpbc)(H₂O)₃]·H₂O(I) (3,3′-bpbc = 2,2′-bipyridine-3,3′-dicarboxylic acid) is successfully synthesized at room temperature and characterized by elemental analysis and IR spectra. The crystal structure of the complex is determined by single crystal X-ray diffraction. The unit cell parameters for complex I are: a = 9.9606(11) Å, b = 9.2552(10) Å, c = 16.0258(17) Å, β = 96.731(0)°, V = 1467.2(3) ų, Z = 4, space group P2(1)/n. In the crystal, the cobalt(II) ion adopts a hexa-coordinate environment, and the structure units aggregate together to give birth to infinite 1D chains. The 2D and 3D framework is constructed via intermolecular hydrogen bonds.     

Amperometric nonenzymatic determination of glucose based on a glassy carbon electrode modified with nickel(II) oxides and graphene

We have developed a stable and sensitive nonenzymatic glucose sensor by modifying a glassy carbon electrode (GCE) with a composite incorporating nickel(II) oxides and reduced graphene. The oxides were generated by directly electrodepositing nickel on the GCE with a graphene modifier using a multi-potential pulse process, and then oxidizing nickel to nickel(II) oxides by potential cycling. In comparison to the conventional nickel(II) oxides-modified GCE, this new nickel(II) oxides-graphene modified GCE (NiO-GR/GCE) has an about 1.5 times larger current response toward the nonenzymatic oxidation of glucose in alkaline media. The response to glucose is linear in the 20 μM to 4.5 mM concentration range. The limit of detection is 5 μM (at a S/N of 3), and the response time is very short (<3 s). Other beneficial features include selectivity, reproducibility and stability. A comparison was performed on the determination of glucose in commercial red wines by high-performance liquid chromatography (HPLC) and revealed the promising aspects of this sensor with respect to the determination of glucose in real samples.

Interaction between β‐Cyclodextrin and Mixed Cationic‐Anionic Surfactants (2): Aggregation Behavior

The interactions between β‐cyclodextrin (β‐CD) and the mixtures of cationic‐anionic surfactants in the aqueous solution were investigated by surface tension, rheology, and dynamic light scattering measurements. It was shown that the key‐lock interactions between β‐CD and mixed cationic‐anionic surfactants were stronger than the electrostatic/hydrophobic interactions between cationic and anionic surfactants. The inclusion of β‐CD to surfactants could destroy the ion‐pair and aggregates of cationic‐anionic surfactants, and even inhibited the precipitation of the mixed cationic‐anionic surfactants. Furthermore, the inclusion of β‐CD to surfactants could also destroy the hydrogen bond between β‐CD molecules, inducing the disassociation of the aggregation formed by β‐CD themselves.     

电化学石英晶体微天平研究高氯酸钠水溶液中活性炭电极的离子存储行为

以电化学石英晶体微天平(EQCM)为主要测试手段,在不同浓度的高氯酸钠(NaClO4)水溶液中研究了水合离子吸附到活性炭电极孔隙过程中电极的质量变化.对于每种电解液,根据Raman光谱和EQCM数据分别计算了本体溶液中和电极/溶液界面上Na+的水合数.通过比对这两组Na+水合数,探讨了Na+存储到活性炭负极过程中的去溶剂化效应.