共查询到19条相似文献,搜索用时 125 毫秒
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细菌细胞脂肪酸是与细菌生物学特性密切相关的重要组分,1963年Able等首次提出利用GC测定细菌细胞脂肪酸,为从分子水平探讨细菌生物学特性开辟了新的途径,现GC已成为细菌细胞脂肪酸分析测定的重要手段。以往的研究均是将脂肪酸转化为相应的甲基酯后,与脂肪酸甲酯标样的GC保留时间对照或以GC-MS定性。本文利用Kovats保留指数和Lee指数结合GC-MS,分析研究了细菌中常见的脂肪酸,探讨了利用Kovats保留指数和Lee保留指数定性的可行性,并以上述保留指数为定性的依据,分析鉴定了多种细菌的脂肪酸组成。 实验部 (一)主要仪器、试剂 GC-5890气相色谱仪,配有3392A积分仪(美国HP公司)。 VG-7070E-HE GC-MS仪,联有DS11/250数据 相似文献
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传统上用气相色谱正构烃类为基准的Kovats保留指数或线性保留指数对汽油的组份进行定性,分析汽油族组成.但此方法有一定的局限性,一是不适合多阶程序升温过程的分析,其次是对于烯烃含量较多的汽油用软件自动识别分析时,需人工干预,色谱峰总的识别率经常低于90.0%.提出了模拟指数的概念和计算规则.采用模拟保留指数定性,色谱峰识别准确,色谱峰总的识别率一般能达99.5%以上. 相似文献
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萜类化合物的QSRR研究及其在结构鉴定中的应用 总被引:1,自引:0,他引:1
采用顶空固相微萃取(SPME)-气相色谱质谱(GC-MS)联用技术分析石香薷和腊梅鲜花中的萜类化合物, 通过保留指数与质谱解析相结合, 分别对化合物进行结构鉴定, 共鉴定出17种单萜化合物, 30种倍半萜化合物. 采用遗传算法(GFA)分别对单萜及倍半萜化合物建立定量结构-色谱保留关系(QSRR)预测模型, 并对该模型进行显著性及预测能力的检测. 同时, 利用计算所得到的模型分别对随机选取的几个萜类化合物进行保留指数预测. 结果表明: 计算保留指数与预测保留指数接近, 模型预测性能较好. 该研究为各种单萜化合物及倍半萜化合物保留指数的预测提供了一种有效手段, 同时, 为建立有效的GC-MS定性方法提供了一定的依据. 相似文献
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酚的拓扑指数在色谱分析中的应用 总被引:14,自引:0,他引:14
图论基础上的拓扑指数在研究物质的定量结构-性质相关性(QSPR)方面发挥了重要的作用. 在众多的拓扑指数中,Wiener指数和物性相关性好,容易计算,应用范围较广[1].在色谱分析中,色谱保留指数作为定性指标的保留值是一种较为可靠的参数.本文选择了酚中具有代表性的15种酚及色谱保留指数,通过对Wiener指数(W),官能团位置指数(Sox)和酚上的甲基数(X-CH3)与色谱保留指数的多元线性回归分析,得到了良好的相关性 .可以说,当测得某一色谱保留指数时可估计其结构特性,进而为酚类化合物的定性分析提供有利的信息. 相似文献
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GUAN Ya-Feng ZHOU Liang-Mo LI Ling-EDalian Institute of chemical physics Chinese Academy of Sciences P.O.Box Dalian Liaoning China 《中国化学》1994,12(3):265-269
A live retention database for compound identification in isothermal and any step temperature programmed capillary gas chromatography has been developed. The database utilizes the Kovats retention indices of compounds on a given stationary phase and the retention time of n-alkanes measured at isothermal conditions on the column to be used, together with the programming parameters. Identification is performed by search operation that compares the calculated results with the retention values of unknown peaks. Cross-reference of the search results of different operating conditions is performed automatically by the database in order to increase the reliability of the identification. The error of the database conversion is ≤± 0.5 index unit, or ≤± 1% on retention time. This paper describes the principle and the structure of the database in detail. The experimental results for different calsses of compounds tested at divers operating conditions will be presented in Part Ⅱ. 相似文献
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Inverse gas chromatographic technique (IGC) was attempted as a new approach to follow the chemical changes that occur during lubricating base oil oxidation. Three groups of the oxidized base oils were prepared at different oxygen flow rates, periods and temperatures according to IP48 method. The corrected retention volumes (VR) were calculated for a series of selected test solutes possessing different functional groups on the oxidized base oils used as stationary phases. Kovats retention index (I), Flory-Huggins interaction parameter (κ∞1,2), and partial molar free energy of solution (ΔG∞L), were calculated for the given test solutes from their VR. The relationships between the I values and the oxidation variables were plotted and discussed. The obtained results were confirmed by potentiometric titration. The study reveals that the magnitudes of variation of I, κ∞1,2 or ΔG∞L retention parameters depend on the oxidation degree of the base oil. Large differences between the I values permit discrimination between the different oxidation steps. 相似文献
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Direct conversion of isothermal to temperature programmed indices is not possible. In this work it is shown that linear temperature programmed retention indices can only be calculated from isothermal retention data if the temperature dependence of both the distribution coefficients and the column dead time are taken into account. Procedures are described which allow calculation of retention temperatures and from these, accurate programmed retention indices. Within certain limits the initial oven temperature and programming rate can be chosen freely. The prerequisite for this calculation is the availability of reliable isothermal retention data (retention times, retention factors, relative retention times, or retention indices) at two different temperatures for one column. The use of compiled isothermal retention indices at two different temperatures for the calculation of retention temperatures and thus temperature programmed indices is demonstrated. For the column for which programmed retention indices have to be determined, the isothermal retention times of the n-alkanes and the column dead time as a function of temperature have to be known in addition to the compiled data for a given stationary phase. Once the programmed retention indices have been calculated for a given column the concept allows the calculation of temperature programmed indices for columns with different specifications. The characteristics which can be varied are: column length, column inner diameter, phase-ratio, initial oven temperature, and programming rate. 相似文献
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Summary Theoretical relationships between the value of a Kovats index measured under isothermal column conditions and that measured with linear temperature programming have been re-examined. A new relationship is proposed which indicates that a retention index measured with temperature programming will correspond to an isothermally measured retention index with the column temperature at the harmonic mean of injection and elution temperatures. This has been experimentally tested for a set of non-polar compounds using OV 101 as stationary phase.Presented at the 14th International Symposium on Chromatography London, September, 1982 相似文献
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V. G. Berezkin A. A. Korolev I. V. Malyukova R. G. Mardanov 《Russian Chemical Bulletin》1997,46(12):2064-2073
The effects of the carrier gas nature and pressure on the relative retention values of organic compounds were studied using
a series of capillary columns differing in the film thickness of the polar stationary phase (PEG-20M). Relative retention
depends linearly on the carrier gas pressure. This dependence becomes more pronounced in the following order of carrier gases:
helium < nitrogen < carbon dioxide. The limiting relative retention at a carrier gas pressure approaching zero rather than
relative retention values measured experimentally (relative retention time, Kovats retention index,etc.) is an invariant characteristic of a compound subjected to chromatography. For the carrier gases studied, the limiting retention
values almost does not depend on the nature of the carrier gas used. The limiting indicating the complex absorption-adsorption
nature of these parameters. Dissolution of a carrier gas in the stationary liquid phase has an effect on the relative retention.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2177–2186, December, 1997. 相似文献
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A multidimensional GC-system containing two capillary columns of different polarities, operated within a double oven instrument, was used for the optimized separation of complex isomeric mixtures of various types of chlorinated aromatic compounds such as PCB, PCDD, or PCDF. Electron capture was applied parallel to flame ionization detection to obtain sensitive signals of the PCB or PCDD and the n-alkane standards required for identification by Kovats indices, respectively. Electron capture detection within a valvelessly operated MDGC system forced changes in the usual instrumental set-up, the live-switching coupling piece being located within the second oven of the double oven instrument. This oven is operated isothermally to ensure optimal and interference-free detection, for stable flow conditions within the coupling piece and for the determination of the isothermal retention indices (Kovats), which are much more suitable for identification by retention than the so-called “linear” indices. 相似文献
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A screening program is reported for approximately 170 pesticides which are regularly encountered in toxicological analysis (organophosphates, carbamates, triazines, halogenated carbohydrates, phenoxycarbonic acid derivatives, and others). It is based on the retention index according to Kovats. Temperature dependence of the retention index and derivatization procedures are also studied.Dedicated in honour to Prof. Dr. Wolfgang Arnold (Hamburg) on the occasion of his 75th birthday.We are indebted to PD Dr. Hans H. Maurer (Homburg/Saar) for stimulating discussions 相似文献
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G. L. Hall W. E. Whitehead C. R. Mourer T. Shibamoto 《Journal of separation science》1986,9(5):266-271
A new gas chromatographic (GC) retention index based on a homologous series of tri-n-alkylamines is proposed for use in the detection of pesticides and related compounds because the standard n-paraffin hydrocarbons used for the Kovats index do not show up well on the nitrogen-phosphorus detectors commonly used in pesticide analysis. Using fused silica bonded phase capillary columns (DB-1 or DB-5), the trialkylamine indices of 106 selected pesticides and related compounds were measured and their relationship to the Kovats index determined. 相似文献