Use of on-line mass spectrometric detection in capillary electrochromatography

Capillary electrochromatography (CEC) is a liquid phase analytical separation technique that is generally carried out with packed capillary columns by electroosmotically driven mobile phase at high electric field strength. The analytes are separated by virtue of the differences in their distribution between the mobile and stationary phases and, if charged in their electrophoretic mobilities as well. It is thus considered a hybrid of liquid chromatography and capillary electrophoresis and is expected to combine the high peak efficiency of capillary zone electrophoresis (CZE) with the versatility and loading capacity of HPLC. This review explores the potential use of on-line mass spectrometric detection for CEC. It discusses key design issues that focus on the physical and electrical arrangement of the CEC column with respect to the electrospray orifice inlet. The salient features of the sheathless, sheath flow and liquid junction interfaces that are frequently employed while coupling a CEC column to an electrospray ionization mass spectrometry system are also highlighted. Possible configurations of the CEC column outlet that would obviate the need for pressurizing the capillary column are also presented. While coupling CEC with MS both the nature of the interface and the configuration of the column outlet will determine the optimal arrangement. The review also discusses bandspreading that occurs when a connecting tube is employed to transfer mobile phase from the column outlet to the atmospheric region of the electrospray source with a concomitant loss in sensitivity. Selected examples that highlight the potential of this technique for a wide range of applications are also presented.     

聚吡咯水杨酸修饰电极的电化学行为及水杨酸含量测定

本用电化学方法制备了聚吡咯－水杨酸修饰电极；并进行了电化学行为的研究，经电化学处理该是电极对水杨酸根具有选择性响应，响应线性范围在１．０×１０＾－＾５－１．０×１０＾－＾３ｍｏｌ／Ｌ之间。电极斜率为４０ｍＶ／ｐＣ，该电极具有较好的稳定性，响应时间在１８０－３００ｓ之间；电极寿命可达６０ｄ。     

脱氧核糖核酸在汞膜电极上的电化学行为

首次在汞膜电极上利用循环安，微分脉冲和交流伏安法研究脱氧核糖核酸（ＤＮＡ）的电化学行为，结果表明汞膜电极作为一类固体电极可应用于负电位区ＤＮＡ电化学行为的研究。同时结合凝胶电泳和ＵＶ光谱法，研究了用纯高氯酸处理的ＤＮＡ的氧化还原特性，结果表明纯高氯酸可经起ＤＮＡ的变性和降解，纯高氯酸不适宜ＤＮＡ的变性处理。     

丙烯环氧化反应的高活性钼催化剂

在钼(Ⅵ),钒(Ⅴ)和钛(Ⅳ)等化合物存在下,丙烯与烷基过氧化氢的环氧化反应比传统的氯醇法有很多优点,其中以钼催化剂的性能最优,但目前报道的催化剂在反应过程中因易分解而降低了活性,并且丙烯与烷基过氧化氢的投料比过大(>3:1),丙烯循环次数过多。前文报道了钼烷基醇胺化合物对环已烯的环氧化反应,本文考察了钼烷基醇胺化合物对丙烯与叔丁基过氧化氢环氧化反应的催化性能。     

Preparation and characterization of polyvinyl alcohol-capped CdSe nanoparticles at room temperature

Polyvinyl alcohol (PVA)-capped CdSe nanoparticles were successfully prepared by a one-step solution growth technique at room temperature and ambient pressure. X-ray diffraction, transmission electron microscopy, infrared spectra, and X-ray photoelectron spectra were used to characterize the final product. The as-prepared CdSe nanocrystals were well dispersed and uniform in shape and the diameter of the particles was confined within 8 nm. Ultraviolet-visible absorption spectra were used to study the confined growth process of PVA-capped CdSe nanoparticles. Photoluminescence measurement showed the near band-edge luminescence of the final product.     

Theoretical study on conformational conversion of 1,3-dioxane inside a capsular host

The conformational conversion of 1,3-dioxane guest encapsulated inside a cylindrical capsular host was investigated with PM3 method and single point energies were evaluated by B3LYP method. When entrapped in the capsule, the guest tumbles were slower than that in the free condition. The influences of the inner phase of the capsule on the guest conformational conversion were discussed in detail.     

HMS和NaY固载酒石酸钛配合物的研究

利用化学键合和“瓶中造船”方法,成功地将酒石酸钛配合物接枝到HMS(heragonal mesoporous silicas)上或包络合于微孔NaY内.FT-IR表征表明酒石酸钛在HMS上是通过与载体表面羟基发生交换作用而被固载的;在NaY载体上则是通过包络合被封装在载体的超笼内.UV-Vis可见漫反射表征表明两类固载型催化剂有着相似的钛配位环境.在催化肉桂醇环氧化反应中,HMS键合型催化剂的反应转化率比NaY包络型催化剂的高;但后者在环氧化选择性上要高于前者.回收样品的重复使用实验结果表明,两类固载型催化剂在重复使用过程中均存在不同程度的失活.     

8-羟基喹哪啶固相萃取光度法测定水样中的铁

研究了8-羟基喹哪啶与铁的显色反应，在pH为8．0的氯化氨-氨水缓冲介质中，在十六烷基三甲基溴化铵(CTMAB)存在下，8-羟基喹哪啶与铁反应生成3：1稳定的蓝紫色络合物，该络合物可被Waters Sep-Park-C18固相萃取小柱萃取，用乙醇洗脱后用光度法测定，络合物λmax=600nm。在此波长下其它金属离子的络合物无光吸收，对铁选择性很好，铁含量在0-5mg/L内符合比尔定律，方法用于水样中痕量铁的测定，结果令人满意。     

5′-Noraristeromycin derivatives isomeric to aristeromycin and 2′-deoxyaristeromycin

A straightforward synthesis of (1S,2R,3R,4R)-4-(6-aminopurin-9-yl)-2-hydroxymethylcyclopentane-1,3-diol (2), an isomer of aristeromycin, and its 2′-deoxy derivative 3 from readily available disubstituted cyclopentenes is presented. An antiviral analysis of 2 showed it to have significant activity versus Epstein-Barr virus (IC₅₀ 0.62 μg/mL in the Elisa assay) and to be free of cytotoxicity effects against the host cells. In a much less comprehensive antiviral analysis, 3 also was active towards Epstein-Barr (IC₅₀ 7.58 μg/mL in the Elisa assay) but this was accompanied by cellular toxicity.     

Water／Oil Biphasic Hydroformylation of Higher Olefins over a TPPTS-Rh／SiO2 Catalyst

A novel TPPTS-Rh/SiO2 catalyst, prepared by directly modifying a heterogeneous high-surface-area Rh/SiO2 catalyst with water-soluble TPPTS ligands, could decrease the resistance of masstransfer in water/oil biphasic media for the hydroformylation of higher olefins. The catalytic performancefor hydroformylation on this biphasic TPPTS-Rh/SiO2 catalyst system was higher than those of thetraditional biphasic HRhCO(TPPTS)3 systems, owing to the chemical bonds between the highly dispersedRh metal particles and the TPPTS ligands. The catalyst system is applicable for hydroformylation ofhigher olefins such as 1-dodecene.