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941.
The analytical potential of furan as a chemical ionization (CI) reagent was evaluated for selectivity with nine monosubstituted naphthalene compounds. The ion-molecule reactions of furan and tetrahydrofuran (THF) were compared with those of methane, methanol and acetonitrile (prominently producing [M + H](+) ion base peaks) with naphthalene compounds in chemical ionization mass spectrometry (CI-MS). Reactions with furan predominantly show M(+) and [M + 39](+) ions. Based on this phenomenon, investigations were carried out for some of the molecular factors such as proton affinity, substituent effects and the preferred site of [C(3)H(3)](+) ion attachment that influence reactivity in furan CI. High selectivity with different substituents is observed in the formation of [M + 39](+) adduct ion, suggesting its usefulness as selective ionization reagent liquid. The selectivity and sensitivity are illustrated in the analysis of mixture of amino acids. Furthermore, the structure determination and reaction mechanism study is characterized by collision-activated dissociation experiments in CI-MS/MS and CI-MS/MS/MS. 相似文献
942.
一种可循环使用的固相试剂:N-烷基-N-酰基磺酰胺聚苯乙烯基微球(5), 通过对聚苯乙烯磺酰氯微球树脂进行两步功能基化的修饰反应来制备. 制备过程如下:聚苯磺酰氯树脂(1)与伯胺(2)反应得到聚苯乙烯基N-烷基磺酰胺树脂(3), 树脂3用酰氯(4)或酸酐酰化得到N-烷基-N-酰基磺酰胺聚苯乙烯基树脂(5). 酰化的树脂5作为酰基转移试剂与亲核试剂胺反应得到二级酰胺. 根据5上取代基对酰胺生成的程度的影响结果表明, 烷基R1和酰基(R2CO)对酰基转移反应活性的大小依次分别为:苯基>苄基>甲基>正丁基>>H和对硝基苯甲酰基(苯甲酰基>乙酰基. 胺的亲核能力对酰胺的收率也有一定的影响. N-苯基-N-苯甲酰基磺酰胺树脂重复使用3次没有发现活性降低. 相似文献
943.
Han-Wen Sun 《Analytica chimica acta》2004,509(1):71-76
Simultaneous vapor generation of zinc (Zn) and cadmium (Cd) was evaluated by atomic fluorescence spectrometry coupled with an intermittent flow vapor generation system. Some complexing reagents, surfactant and transition metal ions were respectively tested as enhancement reagents. Experiments showed that an appropriate amount of 8-hydroxyquinoline or phenanthroline and nickel ion simultaneously, effectively improved the vapor generation efficiency of Zn and Cd. The volatile species generation was presumed to be a hydrogenation process interpreting how the enhancement reagents played an important role in vapor generation. Additionally, due to the instability of volatile species, reaction temperature, rapid and sufficient mixing of reagents and rapid separation of the volatile species from liquid phase were also crucial. The method of simultaneous determination of Zn and Cd by intermittent flow vapor generation led to the development of atomic fluorescence spectrometry. The detection limits (3σb) were 1.6 μg l−1 for Zn and 0.01 μg l−1 for Cd and the relative standard deviations were 3.6% for Zn (50 μg l−1, n=11) and 1.7% for Cd (2 μg l−1, n=11) respectively. Results for the determination of Zn and Cd have been confirmed by the analysis of CRMs with good agreement between the certified and found values. 相似文献
944.
用反相离子对色谱分离和检测水溶性维生素——十二烷基磺酸钠作离子对试剂 总被引:4,自引:0,他引:4
本文使用十二烷基磺酸钠(SDS)作离子对试剂,研究了用反相离子对色谱法对混合水溶性维生素的检测和分离,确定了最佳实验条件,包括SDS浓度,pH值,甲醇与水的配比,三乙胺浓度及柱温等。用本方法对九种混合水溶性维生素〔B_1,B_2,B_5(烟酰胺和烟酸),B_6(吡哆醛和吡哆醇),B_(11),B_(12)和C〕的标样和西瓜汁的分离表明,在所选定的实验条件下,可于10min内一次分离。 相似文献
945.
A facile preparation of Tebbe reagent (1) by reacting AlMe3 solution with Cp1TiCl2 is reported. After complete removal of solvent and excess of AlMe3, the crude Tebbe reagent could be used without purification to react with ketones in a Wittig-type manner. 相似文献
946.
947.
镉(Ⅱ)离子是废水中的重要污染成分[1,2]。本文研究氨羧络合剂N,N′ 二(十二烷基)乙二胺二乙酸(H2R2Y)的氯仿溶液对镉的萃取行为;用电导法、摩尔比法证实了H2R2Y与Cd2+的络合比为1∶1;考察了酸度、络合剂浓度、相比及温度对萃取的影响。1 实验H2R2Y按前文[3]合成,配制成不同浓度的氯仿溶液待用。不同pH缓冲溶液按文献[4]配制;显色剂为1 0×10-3mol/L的4 (2 吡啶基偶氮) 间苯二酚(即4 (2 pyridylazo)resorcinol,以下简写为PAR)乙醇溶液;0 10mol/L的硼砂溶液。于60ml分液漏斗中分别加入5 0ml络合剂氯仿溶液和已配制好的不同pH值… 相似文献
948.
Kazuyuki Sato 《Journal of fluorine chemistry》2003,121(1):105-107
Reaction of ethyl bromodifluoroacetate with a variety of Michael acceptors was tremendously improved by the addition of TMEDA. Using this additive, 1,4-adducts were formed exclusively, and any 1,2-adducts or radical adducts were not obtained. THF or other low boiling solvents can be used as a solvent. This simplifies the work-up of the reaction effectively. 相似文献
949.
The potential of the continuous addition of reagent technique in differential reaction-rate methods was evaluated. The approach was tested on the simultaneous determination of copper and iron through their fast complex-formation reaction with pyridoxal thiosemicarbazone. Mixtures of these metal ions at the sub-μg ml?1 level with copper/iron ratios from 5:1 to 1:2 can be analysed with a precision (relative standard deviation) of 0.25 and 0.45%, respectively. The method was successfully applied to the determination of both metals in serum samples with a purpose-designed reaction mini-chamber. 相似文献
950.
Mohammad Ali Karimi Zarchi 《中国化学会会志》2007,54(5):1299-1302
Crosslinked poly(N‐methyl‐4‐vinylpyridinium)thiocyanate [P4‐Me]SCN (II) is prepared easily and is used as a new polymeric reagent for synthesis of alkyl thiocyanates from alkyl halides under mild and nonaqueous conditions. The used polymeric reagent usually can be removing quantitatively and be regenerated. 相似文献