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961.
Real time monitoring of accelerated chemical reactions by ultrasonication‐assisted spray ionization mass spectrometry 下载免费PDF全文
Shu‐Hsuan Lin Ta‐Ju Lo Fang‐Yin Kuo Yu‐Chie Chen 《Journal of mass spectrometry : JMS》2014,49(1):50-56
Ultrasonication has been used to accelerate chemical reactions. It would be ideal if ultrasonication‐assisted chemical reactions could be monitored by suitable detection tools such as mass spectrometry in real time. It would be helpful to clarify reaction intermediates/products and to have a better understanding of reaction mechanism. In this work, we developed a system for ultrasonication‐assisted spray ionization mass spectrometry (UASI–MS) with an ~1.7 MHz ultrasonic transducer to monitor chemical reactions in real time. We demonstrated that simply depositing a sample solution on the MHz‐based ultrasonic transducer, which was placed in front of the orifice of a mass spectrometer, the analyte signals can be readily detected by the mass spectrometer. Singly and multiply charged ions from small and large molecules, respectively, can be observed in the UASI mass spectra. Furthermore, the ultrasonic transducer used in the UASI setup accelerates the chemical reactions while being monitored via UASI–MS. The feasibility of using this approach for real‐time acceleration/monitoring of chemical reactions was demonstrated. The reactions of Girard T reagent and hydroxylamine with steroids were used as the model reactions. Upon the deposition of reactant solutions on the ultrasonic transducer, the intermediate/product ions are readily generated and instantaneously monitored using MS within 1 s. Additionally, we also showed the possibility of using this reactive UASI–MS approach to assist the confirmation of trace steroids from complex urine samples by monitoring the generation of the product ions. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
962.
The reaction of Ag2SO4 and bpp (bpp = 1,3‐bis(4‐pyridyl)propane) in H2O afforded the complex [Ag2(bpp)2(SO4) · 6.5H2O·CH3OH]n, 1. The IR and TGA have been recorded and the structure has been determined. Crystal data for 1: Space group C2/c, a = 17.885(4), b = 25.230(6), c = 8.832(2) Å, β = 105.437(4)°. V = 3841(1) Å3, Z = 8 with final residuals R1 = 0.0710 and wR2 = 0.1620. The complex shows a three‐dimensional supramoleclar structure constructed with two‐dimensional infinite [Ag2(bpp)2]n sheetlike layers pillared by Ag‐Ag interactions and Ag····O (SO4) interactions in the solid state. 相似文献
963.
采用溶胶-凝胶法制备了 Er3+单掺杂A2 Ti2O7(A=La,Y,Gd)和Er3+,Yb3+共掺杂的La2 Ti2O7纳米晶样品.用X射线衍射仪、扫描电子显微镜和紫外-可见-近红外光谱仪分别对样品的结构、形貌和光吸收性质进行了表征;测试了样品在980 nm激光激发下的室温上转换光谱.结果发现,样品都发出了很强的绿光(大约在525和549 nm)和红光(大约660 nm).通过研究这些基质的晶体结构对上转换发光的影响,发现La2 Ti2O7基质中Er3+离子的上转换发射最强.对La2 Ti2O7纳米晶的上转换发光研究表明,Yb3离子能够有效地敏化Er3离子的上转换发射.对上转换发光强度与泵浦功率的依赖分析,发现红光和绿光的发射均属于双光子吸收过程,最后讨论了Er3+和Yb3的上转换发光机制. 相似文献
964.
建立毛细管柱气相色谱法测定液化石油气中二甲醚含量的分析方法。采用静止进样法直接进样,用PLOT–Q毛细管色谱柱进行分离,以FID检测器进行检测,外标法进行定量分析。液化石油气中二甲醚的含量(体积分数)在0%~20.0%范围内与其色谱峰面积呈良好线性关系,线性相关系数r=0.999 9,方法检出限为0.05%(体积分数),测定结果的相对标准偏差小于5%(n=6),回收率在98.2%~102.9%之间。该方法与校正面积归一法测定结果相一致。该方法准确、快速、简便,适用于液化石油气中二甲醚含量的检测。 相似文献
965.
Structure and Bonding in CE5− (E=Al–Tl) Clusters: Planar Tetracoordinate Carbon versus Pentacoordinate Carbon 下载免费PDF全文
Estefanía Ravell Said Jalife Jorge Barroso Mesías Orozco‐Ic Gerardo Hernández‐Juárez Dr. Filiberto Ortiz‐Chi Dr. Sudip Pan Dr. José Luis Cabellos Prof. Gabriel Merino 《化学:亚洲杂志》2018,13(11):1467-1473
The structure, bonding, and stability of clusters with the empirical formula CE5? (E=Al–Tl) have been analyzed by means of high‐level computations. The results indicate that, whereas aluminum and gallium clusters have C2v structures with a planar tetracoordinate carbon (ptC), their heavier homologues prefer three‐dimensional C4v forms with a pentacoordinate carbon center over the ptC one. The reason for such a preference is a delicate balance between the interaction energy of the fifth E atom with CE4 and the distortion energy. Moreover, bonding analysis shows that the ptC systems can be better described as CE4?, with 17‐valence electrons interacting with E. The ptC core in these systems exhibits double aromatic (both σ and π) behavior, but the σ contribution is dominating. 相似文献
966.
LiMingWEI QingYuOU JuBaiLI 《中国化学快报》2004,15(9):1127-1130
The sol-gel technology is applied for the preparation of solid-phase microextraction (SPME) fiber. The fiber demonstrates high thermal stability, efficient extraction rate and the selectivity for non-polar or low-polar analytes. Efficient SPME-GC-FID analyses of benzenetoluene-ethylbenzene-xylenes (BTEXs) and low-polar halocarbon were achieved by the sol-gel coated DSDA-DDBT-TiO2 fiber. Some parameters of the SPME fiber for the determination of halocarbon in aqueous sample were investigated. 相似文献
967.
Yun MY Kim SB Park S Han CJ Han YH Yoon SH Kim SH Kim CM Choi DW Cho MH Park GH Lee KH 《Experimental & molecular medicine》2007,39(4):508-513
Failure of mitotic checkpoint machinery leads to the chromosomal missegregation and nuclear endoreduplication, thereby driving the emergence of aneuploidy and tetraploidy population. Although abnormal nuclear ploidy and the resulting impairment of mitotic checkpoint function are typical physiological event leading to human hepatocellular carcinoma, any mutational change of mitotic checkpoint regulators has not yet been discovered. Therefore, we investigated the mutation of p31(comet), a recently identified mitotic checkpoint regulator, in human hepatocellular carcinoma. Of 51 human hepatocellular carcinoma tissue and 6 cell lines tested, five samples exhibited nucleotide sequence variations dispersed on four sites within the entire coding sequence. Among these sites with sequence substitutions, three were found to be missense mutation accompanied with amino acid change but one was a silent mutation. Of these sequence substitutions, two were present in both tumor and non-tumor liver tissues, suggesting the possibility of polymorphism. The present findings indicate that p31(comet) does not have an impact on the formation of aneuploidy and tetraploidy found in human hepatocellular carcinoma. 相似文献
968.
IntroductionSnake-cageresin,alsoca1ledsnake-cagepolyelectrolyte['],isaspecialkindofamphotericresin.ItwasfirstinvestigatedbyHatchM.J.etal.in1957[z].Thetypicalandusefulsnake-cageresinisRetardation11A-8(l1A-8inthecon-text)manufacturedbyDowChemicalCoI,TD.Itissynthesizedbypolymerizingacrylicacidinsidethenetworkofastrongbasicanionexchangeresinwith8%crosslinking.Thus,theresinconsistsofacrosslinkedpolymermatrix,cage,andalinearpolymer,socalledsnake,whichisphysicallytrappedinsidethecage.Thecagepol… 相似文献
969.
970.