Electroanalysis and simultaneous determination of dopamine and epinephrine at poly(isonicotinic acid)-modified carbon paste electrode in the presence of ascorbic acid

A carbon paste electrode modified with electropolymerized fills of isonicotinic acid was developed.The modified electrode shows excellent electrocatalytic activity toward the oxidation of both dopamine(DA)and epinephrine(EP).Separation of the reduction peak potentials for dopamine and epinephrine was about 357 mV in pH 5.3 phosphate buffer solution(PBS)and the character was used for the detection DA and EP simultaneously.The peak currents increase linearly with DA and EP concentration over the range of 8.0×10-5 to 7.0×10-4 mol/L and 5.0×10-6 to 1.0×10-4 mol/L with detection limits of 2 × 10-5 and 1×10-6 mol/L,respectively.The interference studies showed that the modified electrode exhibits excellent selectivity in the presence of large excess of ascorbic acid(AA).     

具有多级孔结构的NH4-β沸石的直接合成及其性能

以非离子表面活性剂壬基酚聚氧乙烯醚(Tx-15)为模板,设计氟化铵作为矿化剂.在近中性条件下直接合成了具有微孔-介孔复合孔道的铵型β沸石.合成样品采用粉末X射线衍射(PXRD),高分辨扫描电子显微镜(SEM),微分热重(DTG)以及氨程序升温脱附(NH3-TPD)等手段进行了表征.结果表明,氟离子及非离子表面活性剂的加入对沸石的孔结构、酸性质均起到了一定的调变作用.该沸石具有发达的呈梯级分布的多级孔结构,孔容高达0.67 cm3·g-1,且具有较强的Bronsted酸和适度分布的Lewis酸,大大改善了反应物和产物分子的扩散和反应性能.在混合C4烃的催化裂解反应中,该沸石与传统方法合成的β沸石相比,其转化率提高了约15%,烯烃(乙烯和丙烯)产率提高了近10%,芳烃(苯和甲苯)产率提高了3%.     

P-mSA/mCS双极膜的制备及其在一价、二价离子分离中的应用

以五氧化二磷、磷酸三乙酯和磷酸为反应剂, 制备了磷酸化海藻酸钠(P-SA), 经二茂铁离子改性后作为阳膜层(P-mSA); 用乙酰基二茂铁改性壳聚糖制备了阴膜溶胶(mCS). 将阴膜溶胶流延于阳膜层上, 制备了P-二茂铁-SA/乙酰基二茂铁-CS双极膜(P-mSA/mCS BPM). 测定了双极膜的红外光谱、接触角、电荷密度、离子交换容量与交流阻抗. IR与接触角的分析结果表明, SA经磷酸化后, 亲水性能得到了显著提高. 将P-mSA/mCS BPM应用于一价、二价离子的分离, 当压力差为0.3 MPa时, 二价离子的截留率(双极膜截留的离子百分数)为95%, 一价离子的截留率为22%左右.     

Pickering乳液聚合制备核-壳结构PS-SiO2复合微球

用二氯二甲基硅烷对纳米SiO2粒子进行疏水改性,当其表面Zeta电位由-54.8 mV变成-25.8 mV时,SiO2粒子就能在苯乙烯-水界面自组装,形成稳定的Pickering乳液,即以胶体粒子为乳化剂的乳液.利用Pickering乳液聚合制备了以聚苯乙烯(PS)为核、纳米SiO2为壳的PS-SiO2复合微球.用FT-IR、XPS、SEM、偏光显微镜等对复合微球进行了表征.结果表明:复合微球由聚苯乙烯和纳米二氧化硅粒子组成,二氧化硅粒子以单层、六方密排的方式分布在聚苯乙烯微球表面.     

SBA-15介孔分子筛担载的钒基氧化物催化剂对乙烷选择氧化性能

用等体积浸渍法制备了SBA-15担载的钒基(V/SBA-15)和钾修饰的钒基氧化物(K-V/SBA-15)催化剂, 使用氮气吸附、小角X射线衍射(XRD)、紫外-可见漫反射光谱(UV-Vis DRS)和紫外激光拉曼光谱对这些催化剂的结构进行表征, 并评价了这些催化剂对乙烷选择氧化的活性与选择性. 实验结果表明介孔结构SBA-15对乙烷选择氧化的活性优于常规的SiO2; 对于SBA-15担载的V/SBA-15和K-V/SBA-15催化剂, 极低钒担载量(nV:nSi≤0.1:100)时隔离的四配位钒氧化物是乙烷选择氧化生成醛类化合物的活性物种, 高钒担载量(nV:nSi≥2.5:100)时聚合的和微晶态的钒氧化物是乙烷氧化脱氢或深度氧化的活性物种.     

汽油活性炭基脱硫吸附剂的制备与评价

以250℃温度下浓硫酸改性后的活性炭为载体,采用浸渍法制备了以MnO₂为活性组分的活性炭基的汽油脱硫吸附剂MnO₂/AC,考察了吸附剂的制备条件及脱硫条件对脱硫效果的影响。研究结果表明,适宜的吸附剂制备条件为,以Mn(NO₃)₂为活性组分前驱物,Mn(NO)₂浸渍液浓度0.15mol/L、常温下浸渍24h、焙烧温度350℃、焙烧时间2h。该吸附剂在静态吸附温度120℃、吸附时间2h、剂油质量比0.10的条件下可使原料油硫的质量分数从628.6×10^-6降至221.5×10^-6,脱硫率达到64.8%;在动态吸附温度60℃、空速1.76h^-1的条件下,初始流出汽油硫的质量分数降至21.8×10^-6,初始脱硫率达到96.5%。     

基质效应对有机磷农药测定的影响及其解决方法

该文以液液萃取-气相色谱法探讨了基质对乐果、甲基对硫磷、马拉硫磷和对硫磷4种有机磷测定的影响以及解决方法.研究表明,气相色谱法测定有机磷农药的过程中基质效应显著存在,其基质增强比例为1.01 ～3.46.基质效应由基质种类及含量、有机磷农药种类及浓度等因素决定,同时与萃取溶剂、测定条件(如衬管、进样口温度等)有关.不同萃取溶剂对有机磷农药的萃取效率不同,但均存在基质增强效应;当进样口温度为260 ℃时,可最大程度降低基质在衬管中的残留,且不造成有机磷农药的分解;衬管则应首选带玻璃棉的.实际样品/标准样品的交替进样方式可以降低基质效应强度,但难以达到回收率要求,而校正因子校正法及分析保护剂法则是降低或消除基质效应的可行办法.     

Torsion pendulum automation by a single microcomputer

A new automated torsional pendulum is described. It uses a single photocell for the measurement of the period of oscillation and the logarithmic decrement. Data acquisition, data processing and temperature control are all performed by a single microcomputer. The result is that the instrument can be produced and operated more cheaply than before.The principles behind the design, the method of determining the shape factor, the calibration procedure and the software are discussed. Examples are given to illustrate the use of this instrument. A practical limitation is that the loss tangent should not exceed about 3.     

Supported Pd-Cu bimetallic nanoparticles that have high activity for the electrochemical oxidation of methanol

Monodisperse bimetallic Pd-Cu nanoparticles with controllable size and composition were synthesized by a one-step multiphase ethylene glycol (EG) method. Adjusting the stoichiometric ratio of the Pd and Cu precursors afforded nanoparticles with different compositions, such as Pd(85)-Cu(15), Pd(56)-Cu(44), and Pd(39)-Cu(61). The nanoparticles were separated from the solution mixture by extraction with non-polar solvents, such as n-hexane. Monodisperse bimetallic Pd-Cu nanoparticles with narrow size-distribution were obtained without the need for a size-selection process. Capping ligands that were bound to the surface of the particles were removed through heat treatment when the as-prepared nanoparticles were loaded onto a Vulcan XC-72 carbon support. Supported bimetallic Pd-Cu nanoparticles showed enhanced electrocatalytic activity towards methanol oxidation compared with supported Pd nanoparticles that were fabricated according to the same EG method. For a bimetallic Pd-Cu catalyst that contained 15?% Cu, the activity was even comparable to the state-of-the-art commercially available Pt/C catalysts. A STEM-HAADF study indicated that the formation of random solid-solution alloy structures in the bimetallic Pd(85)-Cu(15)/C catalysts played a key role in improving the electrochemical activity.     

Boronic Acid functionalized core-shell polymer nanoparticles prepared by distillation precipitation polymerization for glycopeptide enrichment

The boronic acid-functionalized core-shell polymer nanoparticles, poly(N,N-methylenebisacrylamide-co-methacrylic acid)@4-vinylphenylboronic acid (poly(MBA-co-MAA)@VPBA), were successfully synthesized for enriching glycosylated peptides. Such nanoparticles were composed of a hydrophilic polymer core prepared by distillation precipitation polymerization (DPP) and a boronic acid-functionalized shell designed for capturing glycopeptides. Owing to the relatively large amount of residual vinyl groups introduced by DPP on the core surface, the VPBA monomer was coated with high efficiency, working as the shell. Moreover, the overall polymerization route, especially the use of DPP, made the synthesis of nanoparticles facile and time-saving. With the poly(MBA-co-MAA)@VPBA nanoparticles, 18?glycopeptides from horseradish peroxidase (HRP) digest were captured and identified by MALDI-TOF mass spectrometric analysis, relative to eight glycopeptides enriched by using commercially available meta-aminophenylboronic acid agarose under the same conditions. When the concentration of the HRP digest was decreased to as low as 5?nmol, glycopeptides could still be selectively isolated by the prepared nanoparticles. Our results demonstrated that the synthetic poly(MBA-co-MAA)@VPBA nanoparticles might be a promising selective enrichment material for glycoproteome analysis.