共查询到20条相似文献,搜索用时 203 毫秒
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用二维色谱技术测定聚合反应气体组成 总被引:1,自引:1,他引:1
介绍一种无阀切换的二维气相色谱分析方法。采用两根不同性质的色谱柱并联连接,样品分别经两根色谱柱分离后汇合在一起进入同一检测器。一次进样可同时测定H2、O2、N2及C1~C3的组分。 相似文献
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本文合成了六个含“CCl3”或“CC”基团的酯类化合物([Cl3CC(O)OCH2]21;p-(Cl3CC(O)O)2C6H42;(Cl3CC(O)O)3C3H53;(Cl3CC(O)OCH2)4C4;Cl3CC(O)OCH2CCH5;C6H5C(O)OCH2CCH6)并对其进行了C/H分析、IR、1HNMR等项表征,对化合物5、6进行了质谱分析。 相似文献
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本文利用过渡金属的亲硫性,通过Cp*-W(CO)3Cl(Cp*=C5H5,C5H4CH3)与HFe2Co(CO)9(μ3-S)反应,得到四种含硫异核金属羰基原子簇化合物Cp*WFeCo(CO)8(μ3-S)(Cp*=C5H5,Ⅰ-a;Cp*=C5H4CH3,Ⅱ-a),(Cp*W)2Fe(CO)7(μ3-S)(Cp*=C5H5,Ⅰ-b;Cp*=C5H4CH3,Ⅱ-b)。对合成的簇合物进行了IR,1H/13C-NMR,C/H及金属分析,并对Ⅰ-a进行了X-射线单晶结构分析。 相似文献
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二(三)苄基锡不饱和烃基膦酸酯的合成 总被引:15,自引:3,他引:15
合成了10种二(三)苄基锡不饱和烃基膦酸酯[(PhCH2)nSn]n-1O2P(O)R(n=2,3;R=—C≡CPh,—C≡CC5H11-n,—C≡CCH2OCH3,—C≡CCH2OC2H5,—CH=CClPh),利用元素分析、核磁共振氢谱和TG-DTA对其组成和结构进行了表征.初步生物活性测试表明,有些化合物具有较强的杀螨和杀菌活性 相似文献
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本文对Cu/Co比不同的五个Cu-Co-Al合金样及其碱抽提产物──RaneyCu-Co催化剂的体相结构进行了XRD表征。结果表明:Cu-Co-Al合金由CuAl、CuAl_2及Al_(13)Co_4三种物相构成。随Cu/Co原子比(0.17~23.1)增高,Al_(13)Co_4及CuAl物相逐渐减少,直至消失,CuAl_2物相产生且逐渐增多。RaneyCu-Co催化剂由两种Cu-Co固溶体组成,一种富铜,另一种富钴。Cu-Co固溶体的形成发生于碱抽提或还原过程,含钴物相的存在有利于CuA1物相的碱抽提。 相似文献
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Presently, two coupling techniques are used for directly introducing HPLC fractions into capillary GC: The retention gap technique (involving negligible or partially concurrent solvent evaporation) and fully concurrent solvent evaporation. While the former involves use of a conventional on-column injector, it is now proposed that concurrent solvent evaporation technique be carried out using a switching valve with a built-in sample loop. The technique is based on the concept that the carrier gas pushes the HPLC eluent into the GC capillary against its own vapor pressure, generated by a column temperature slightly exceeding the solvent boiling point at the carrier gas inlet pressure. Further improvement of the technique is achieved by flow regulation of the carrier gas (accelerated solvent evaporation) and backflushing of the sample valve (improved solvent peak shape). Concurrent solvent evaporation using the loop-type interface is easy to handle, allows transfer of very large volumes of HPLC eluent (exceeding 1 ml), and renders solvent evaporation very efficient, allowing discharge of the vapors of 1 ml of solvent through the column within 5–10 min. 相似文献
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Concurrent solvent evaporation using the loop-type HPLC-GC interface requires that the GC oven temperature be above the eluent boiling point at the given carrier gas inlet pressure in order to prevent eluent flowing into the GC capillary column. Corresponding oven temperatures representing minimum oven temperatures for eluent transfer were experimentally determined for solvents and solvent mixtures of interest for use as HPLC eluents. Evaluation of eluents for concurrent evaporation is discussed. Recommended lengths of uncoated column inlets (pre-columns) are derived from the mechanisms involved in solvent evaporation. Temperatures listed as minimum column temperatures for concurrently evaporating HPLC eluents are also useful for estimating maximum applicable column temperatures when working with the conventional retention gap or partially concurrent solvent evaporation techniques in coupled HPLC-GC. 相似文献
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Tuulia Hytyluinen Konrad Grob Marja-Liisa Riekkola 《Journal of separation science》1997,20(12):657-664
Temperature measurements on the column outer well were used for detecting recondensation or evaporation of solvent inside the precolumn during injection or on-line transfer of large solvent volumes. This facilitates the choice of the most critical parameter of these techniques, i.e. oven temperature. When using the vaporizer/precolumn solvent split/gas discharge system, the dew point of the solvent is determined, either to just prevent solvent recondensation or to limit it to the capacity of the precolumn to retain liquid. In concurrent eluent evaporation through the loop type LC-GC interface, temperature measurement enables the determination of whether or not the flooded zone exceeds a given limit. Fanally, when solvent trapping is used (on-column injector/partially concurrent solvent evaporation evaporation or vaporizer/partial recondensation), temperature measurement near the front end of the flooded zone is used as a signal for accurate closure of the vapor exit shortly before the end of solvent evaporation. 相似文献
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The concept and some first results of a method are described for evaporating large volumes of solvent in a relatively short pre-column (retention gap) in such a way that solvent trapping retains volatile components in the inlet up to completion of solvent evaporation. The method was developed for transferring large volumes (easily exceeding 1 ml) of HPLC eluent to GC when using on-line coupled HPLC-GC, but is equally suited for injecting large sample volumes (at least some 50 μl) and could be particularly useful for introducing aqueous solutions. Concurrent solvent evaporation allows introduction of very large volumes of liquid into GC. However, peaks eluted up to some 40–80° above the column temperature during introduction of the liquid are strongly broadened due to the absence of solvent trapping. On the other hand, previous retention gap techniques involving solvent trapping were not suited for transferring very large volumes of liquid into GC. Using a relatively high boiling co-solvent added to the sample or the HPLC eluent, advantages of concurrent solvent evaporation can be combined with solute reconcentration by solvent effects, allowing elution of sharp peaks starting at the column temperature during introduction of the sample. 相似文献
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Grob K 《Journal of chromatography. A》2000,892(1-2):407-420
Progress during the last 5 years in on-line LC-GC and related techniques is reviewed. In normal-phase LC-GC, the wire interface proved to have advantages over the loop type interface. Further investigations on the solvent evaporation process in an uncoated precolumn under conditions of an early vapour exit revealed that the rules for the transfer by the retention gap techniques must be modified. For reversed-phase LC-GC, approaches with a phase transfer compete with direct evaporation. Eluents were extracted into a bed of Tenax located in a programmed-temperature vaporiser and thermally desorbed. Direct evaporation is possible when a hot vaporising chamber is used and solvent/solute separation occurs in a separate compartment, a coated precolumn possibly in combination with packed beds. As a future strategy, LC-GC transfer techniques should be adjusted to those of large volume injection and involve a single device. It is believed that on-column injection/transfer is the choice. This requires that concurrent evaporation in LC-GC is performed by the on-column interface. 相似文献
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Use of early solvent vapor exits for concurrent eluent evaporation with the loop-type interface has two purposes: protection of the GC detectors from large amounts of solvent vapors and more efficient discharge of the vapors to accelerate eluent evaporation and help avoiding broad solvent peaks. Use of a retaining pre-column after the uncoated pre-column can rule out losses of solute materials that form sharp peaks. 相似文献
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A technique is proposed which allows introduction of very large volumes of liquid (10 ml were tested) into capillary columns equipped with short (1–2 m long) retention gaps. It is based on concurrent solvent evaporation, i.e. evaporation of the solvent during introduction of the sample. The technique presupposes high carrier gas flow rates (at least during sample introduction) and column temperatures near the solvent boiling point. The major limitation of the method is the occurrence of peak broadening for solutes eluted up to 30°, in some cases up to 100°, above the injection temperature. This is due to the absence of solvent trapping and a reduced efficiency of phase soaking. Therefore, use of volatile solvents is often advantageous. Application of the concurrent solvent evaporation technique allows introduction of liquids which do not wet the retention gap surface. However, the method is still not very attractive for analysis of aqueous or water-containing solutions (reversed phase HPLC). 相似文献
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When 0.53 mm i.d. uncoated precolumns connected to a solvent vapor exit are used for sample introduction with partially concurrent solvent evaporation, substantial losses of volatile solutes are often observed. They were found to be the consequence of solute accumulation at the front end of the flooded zone, which in turn is the result of a strong pressure drop over the flooded zone owing to the formation of plugs of sample liquid. The pressure drop causes significant solvent evaporation at the front, which enriches the solute material there and causes its loss. The use of 0.32 mm i.d. restrictions between the uncoated precolumn and the vapor exit greatly reduced this problem. 相似文献
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F. Munari A. Trisciani G. Mapelli S. Trestianu K. Grob J. M. Colin 《Journal of separation science》1985,8(9):601-606
Two-dimensional chromatography of gasoline by on-line coupled HPLC-HRGC, as described in this paper, allows separate GC analysis of paraffins and aromatics. The GC system contains a retention gap of only 10 m length for introducing HPLC fractions of 100 μl volume. This becomes possible through evaporation of part of the solvent during introduction of the HPLC eluent. This “partially concurrent solvent evaporation” technique allows transfer of large volumes of HPLC eluent into relatively short retention gaps, maintaining the full efficiency of the solvent effects in reconcentrating the bands of the early eluted solutes. 相似文献