加速溶剂萃取同步净化-同位素内标-气相色谱-高分辨质谱测定水产品中32种多氯联苯

建立了加速溶剂萃取同步净化-同位素内标-气相色谱-高分辨质谱同时测定水产品中32种多氯联苯含量的方法。通过在加速溶剂萃取仪中加入2 g无水硫酸钠、1 g弗罗里硅土、50 g中性氧化铝作为吸附剂实现同步净化的效果，萃取溶剂为二氯甲烷-正己烷（1:1，v/v），萃取温度为100℃，循环2次。萃取结束后分别用0.5 mL浓硫酸净化两次，净化液浓缩定容后，采用气相色谱-高分辨质谱测定，同位素内标法定量。32种多氯联苯在0.1~20 μg/L范围内平均相对响应因子（RRF）的相对标准偏差（RSD）值（n=7）均小于15%，定量限（S/N=10）为0.3~1.9 ng/kg。在草鱼和海鲈鱼空白基质中做加标回收试验，添加水平为5、20和50 ng/kg，得到的平均回收率为71.9%~119.0%（n=6），RSD为3.5%~19.6%。该方法背景干扰低，灵敏度高，重现性好，回收率稳定，适用于水产品中多氯联苯的检测。     

二(2,4,4-三甲基戊基)膦酸-上胺205-正庚烷乳状液膜分离钪(Ⅲ)、铁(Ⅲ)和镥(Ⅲ)

本文研究了二（2，4，4-三甲基戊基）膦酸（Cyanex272）-上胺205-正庚烷乳状液膜分离Sc（Ⅲ）、Fe（Ⅲ）和Lu（Ⅲ）。考察了外相酸度、表面活性剂浓度、流动载体浓度及内相盐酸浓度对Sc（Ⅲ）迁移的影响。并探讨了该液膜体系分离Sc（Ⅲ）、Fe（Ⅲ）和Lu（Ⅲ）的可能性，结果表明，该体系对于稀土矿中Sc（Ⅲ）的分离与分析有良好的应用前景。     

ELECTROCHEMICAL POLYMERIZATION OF ANILINE IN PHOSPHORIC ACID AND THE PROPERTIES OF POLYANILINE

The behavior of the electrochemical polymerization of aniline in a weak acid, phosphoric acid, is very similar to that in strong acids, i.e. its polymerization rate increases quickly with the electrolysis time. The FTIR spectra of polyaniline samples synthesized in phosphoric acid indicate that the counter ion H2PO4^- is present in both the oxidized form and the reduced form of polyaniline. The counter ion plays an important role in adjusting the pH value at the electrode surface of polyaniline during the oxidation and reduction processes. As a result, a pair of redox peaks still appear in cyclic voltammograms of polyaniline in a solution of sodium sulfate of pH 5.5 and in a solution of NaH2PO4 of pH 7.0,respectively, at low potential scan rate; and the color of polyaniline film also changes with applied potential at pH 7.0. Thus,the pH region for the electrochemical activity and the electrochromism of polyaniline is extended to pH 5.5 for a solution of sodium sulfate and to pH 7.0 for a solution of NaH2PO4. The conductivity of polyaniline is 3.3 S cm^-1, depending on the concentration of phosphoric acid used in the stage of polymerization of aniline. The result of elemental analysis of polyaniline is presented here.     

An efficient synthesis of a hexasaccharide—the repeating unit of the exopolysaccharide from Cryptococcus neoformans serovar A

A general method for the synthesis of 2-xylose or glucuronic acid branched (1→3)-linked mannose oligosaccharides has been developed. As a typical example, the synthesis of the methyl glycoside of β-d-GlcpA-(1→2)-α-d-Manp-(1→3)-[β-d-Xylp-(1→2)-]α-d-Manp-(1→3)-[β-d-Xylp-(1→2)-]α-d-Manp, the repeating unit of the exopolysaccharide from Cryptococcus neoformans serovar A, was achieved in a regio- and stereoselective manner.     

以学生为中心的物理化学远程教学初探

During the fight against the new coronavirus epidemic, the "Physical Chemistry" team of Beijing Normal University used various network platforms and tools, such as MOOC of China University, Rain Classroom and WeChat Group in the teaching process. The exploration and practice of online learning of "Physical Chemistry" is carried out based on MOOC teaching, with student learning as the center and teacher guidance as the support. Taking the most difficult chapter of "fundamentals for statistical thermodynamic" as an example, we designed a complex teaching program that includes previews, watching MOOC videos in class, real-time online exercises, teachers' answers, and after-class reflection and questioning. The students were encouraged to learn independently through the reserved information, designed activities and assignments. Practice shows that the online course has cultivated the students' self-management ability, trained their critical thinking skills, and achieved good teaching results.     

Co—Mo／MgO—Al2O3水煤气耐硫变换催化剂失活的研究

利用Ｘ－射线衍射，扫描电镜，拉曼光谱，等离子发射光谱和比表面测定等方法研究了不同状态下失活及新鲜催化剂的结构，杂种类及含量。结果表明，超温使催化剂晶化明显，制备方法对催化剂结构有直接影响，再生使其强度降低，条形催化剂比较容易粉化，无机杂质是次要的失活原因。     

TiO2 sol-gel derived amperometric biosensor for H2O2 on the electropolymerized phenazine methosulfate modified electrode

A novel hydrogen peroxide biosensor was developed based on the immobilization of horseradish peroxidase (HRP) in a TiO(2) sol-gel matrix on an electropolymerized phenazine methosulfate (PMS) modified electrode surface. Such membranes are of interest due to their high surface area, biological compatibility, and ease of fabrication. HRP entrapped in the TiO(2) matix was stable and retained its activity to a large extent. Cyclic voltammetry and amperometric measurements were employed to demonstrate the feasibility of electron transfer between immobilized HRP and the glassy carbon electrode via electropolymerized PMS. The influence of various experimental parameters such as operating potential, pH, temperature, and stability was investigated for optimum analytical performance. The biosensor provided a wide linear calibration range from 4.0x10(-6) M to 1.0x10(-3) M, with a detection limit of 8.0x10(-7) M at a signal-to-noise ratio of 3. The sensor retained 80% of its original activity after two months of operation.     

Characterization of silicon nitride particles synthesized in an atmospheric-pressure convection-stabilized arc

Silicon nitride powders were synthesized in an atmospheric-pressure convection-stabilized arc using silicon and ammonia as reactants. The morphology and particle size distributions of the silicon nitride particles were characterized by SEM, TEM, and electron diffraction analyses. The silicon nitride particles collected in the plasma reactor were formed by either gas-condensed phase reactions or chemical vapor reactions. The morphologies of the particles formed by gas-condensed phase reactions consisted of -Si₃N₄ prisms, -Si₃N₄ matte, -Si₃N₄ needles, and spaghetti-like whiskers. For the homogeneously nucleated particles, the morphologies included dendrites, needles, platelets, and amorphous particles. Most of the particles formed were aggregates with particle size distributions ranging from 500 to 1500 Å depending on the location of injection of the reactants.     

Study on the interaction of trypsin with some DNAs and their analytical application by resonance Rayleigh scattering spectra

When trypsin reacts with Herring sperm DNA (hsDNA), Salmon sperm DNA (sDNA), and Calf thymus DNA (ctDNA) to form a complex, the resonance Rayleigh scattering (RRS) was remarkably enhanced and new RRS spectra appear. These new spectra have similar characteristics of RRS spectra. The maximum RRS peaks are at 307 nm (hsDNA, sDNA) and 290 nm (ctDNA), and other peaks are at 350 nm. The scattering intensity is proportional to the concentration of DNA or trypsin; so this intereaction can be used to determine trypsin using DNA or DNA using trypsin. In the determination of DNA using trypsin, the linear ranges for hsDNA, sDNA, and ctDNA are 0–2.3, 0–2.5, and 0–1.9 μg·mL⁻¹, and the detection limits are 0.4, 0.7, and 1.1 ng·mL⁻¹, respectively. In the determination of trypsin using hsDNA, the linear range is 0–30.0 μg·mL⁻¹, and the detection limit is 39.0 ng·mL⁻¹. In this paper, the intereaction conditions were optimized. The affecting factors, chemical properties of the complex, and the composition ratio of trypsin with DNA were investigated. Using trypsin as RRS probe, a sensitive method for the determination of trace amounts of DNA was developed. Translated from Chemical Journal of Chinese Universities, 2006, 27(3) (in Chinese)     

[H2en]2{La2M(SO4)6(H2O)2} (M=Co, Ni): First organically templated 3d-4f mixed metal sulfates

The first organically templated 3d-4f mixed metal sulfates, [H₂en]₂{La₂M(SO₄)₆(H₂O)₂} (M=Co 1, Ni 2) have been synthesized and structurally determined from non-merohedrally twinned crystals. The two compounds are isostructural and their structures feature a three-dimensional anionic network formed by the lanthanum(III) and nickel(II) ions bridged by sulfate anions. The La(III) ions in both compounds are 10-coordinated by four sulfate anions in bidentate chelating fashion, and two sulfate anions in a unidentate fashion. The transition metal(II) ion is octahedrally coordinated by six oxygens from four sulfate anions and two aqua ligands. The doubly protonated enthylenediamine cations are located at the tunnels formed by 8-membered rings (four La and four sulfate anions).