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91.
A homologous series of 2,4-dichlorobenzyl alkyl ethers (DCBEs) have been synthesized and purified for use as retention index calibrants and internal standards. They are stable, sensitive to ECD and FID and ideal for GC-MS, with base peaks at m/z 159/161. The retention index calibration against the n-alkanes for a linear temperature program (LTP) series is given and recommendations made for the most suitable members of the DCBE series for use as internal standards in organochlorine (OC) residue analysis. 相似文献
92.
Summary Reproducibility of the Kovats retention indices of alkylbenzenes was studied on conventional “PONA” fused-silica capillary
columns coated with crosslinked dimethyl silicone phase, with a film thickness of 0.5 μm. The data were compared with those
obtained on conventional OV-101 columns. The tested PONA columns showed reproducible chromatographic properties, capacity
ratios and high efficiencies. Having a standard deviation of s=0.03 i.u. of the retention indices on a single column, the
column-to-columns differences were found to be up to 0.3 i.u. Higher indices were determined for crosslinked columns, the
difference being in most cases about one i.u. 相似文献
93.
Summary A global LSER model that relates HPLC retention to mobile phase composition and pH is tested for a varied group of solutes,
both neutral and ionizable, in a polymeric column and methanol-water mobile phases. It is compared to the local LSER model
developed only for a given mobile phase, i.e., a fixed organic modifier content, and to the global LSER model set only for
neutral solutes. The global LSER model for neutral and ionizable solutes requires a few supplementary parameters over the
other models tested, but it accounts for retention under any experimental conditions for a given column and methanol-water
mobile phases, describing properly the interactions established in the HPLC system (hydrophobicity, hydrogen-bond acidity
and basicity, dipolarity/polarizability…).
This paper is number 13 of a series with the same general title: “Retention of Ionizable Compounds on HPLC” published in various
journals. 相似文献
94.
Modelling and prediction of retention in high-performance liquid chromatography by using neural networks 总被引:1,自引:0,他引:1
Y. L. Xie J. J. Baeza-Baeza J. R. Torres-Lapasió M. C. García-Alvarez-Coque G. Ramis-Ramos 《Chromatographia》1995,41(5-6):435-444
Summary Multi-layer feed-forward neural networks trained with an error back-propagation algorithm have been used to model retention
behaviour of liquid chromatography as a function of the composition of the mobile phases. Conventional hydro-organic and micellar
mobile phases were considered. Accurate retention modelling and prediction have been achieved using mobile phases defined
by two, three and four parameters. With micellar mobile phases, the parameters involved included the concentrations of surfactant
and organic modifier, pH and temperature. It is shown that neural networks provide a competitive tool to model varied inherent
nonlinear relationships of retention behaviour with respect to the mobile phase parameters. The soft models defined by the
weights of the networks are capable of accommodating all types of linear and nonlinear relationships, neural networks being
specially useful when the relationships between retention behaviour and the mobile phase parameters are unknown. However,
to train neural networks more experimental points than with hard-modelling methods are required, hence the use of the networks
is recommended only for those cases where adequate theoretical or empirical models do not exist. 相似文献
95.
有机官能化MSU-x孔分子筛的界面特征 总被引:5,自引:0,他引:5
MSU- x是自 M41S系列介孔分子筛问世以来所合成的另一类新型介孔分子筛材料 ,它具有三维立体交叉排列的 " worm- like"孔道结构特征及采用中性模板剂、廉价无毒等诸多合成优点 [1~ 4],有着潜在的应用价值 .为了改善纯硅的介孔材料的表面和孔道性质 ,扩大其应用领域 ,除了在骨架引入金属离子或在其孔道中负载催化活性物质外 ,对介孔材料进行有机官能化制备无机-有机杂化材料改善其骨架和孔道性质是当前研究的热点之一 [5].正是由于活性有机基团的存在 ,使得这些材料可直接用于催化反应 ,或作为中间介质成为其它络合离子的主体 .由于有机基… 相似文献
96.
T. Kowalska 《Chromatographia》1991,31(3-4):119-122
Summary Intermolecular interactions between the solute and the moieties constituting the mobile phase significantly contribute to the overall retention pattern of a given solute in a given chromatographic system. In this paper retention of solute is discussed in the case of the B+AB1+AB2 type mobile phase, which, in a quasithermodynamic way, can be divided into seven individual moieties. One evaluates the influence of each moiety on solute retention, and refers these regularities to the polarity of the solutes. 相似文献
97.
从充分利用气相色谱/质谱(GC/MS)提供的信息来鉴定GC流出组分的目的出发,并以脂肪醇分析为例讨论了GC保留指数在MS谱图解析及MS鉴定结果的合理性检验方面的作用。总结了GC保留的同系物规律、极性规律、加和规律及异构物规律来指导MS谱图解析。提出了含氧化合物官能团相对于-CH2-质量数的保留指数附加贡献值辅助MS确定化合物的类别。同时采用了GC/MS中选择离子检测方法(SIM)在分子离子峰受噪音干扰或太弱以至完全未观测到时来进一步佐证其相对分子质量。 相似文献
98.
H. Ohta K. Jinno Y. Saito J. C. Fetzer W. R. Biggs J. J. Pesek M. T. Matyska Y. -L. Chen 《Chromatographia》1996,42(1-2):56-62
Summary The temperature-dependency of the separation of fullerenes in liquid chromatography (LC) has been examined using various alkyl bonded stationary phases. It has been found that a maximum retention temperature exists with long alkyl bonded stationary phases, whereas there is no similar effect with the newly synthesized alkyl bonded phases which have two phenyl groups at the base of the bonded phase. The interpretation of the retention behavior of fullerenes in the low temperature region on alkyl bonded stationary phases is discussed using information obtained by CP-MAS solid-state NMR spectroscopy and LC. 相似文献
99.
In on-column or in splitless injection with recondensation of the solvent, the length of the flooded zone in the column inlet depends primarily on the wettability of the internal wall of the inlet. For columns with a coated inlet this explains why peak distortion due to band broadening in space by a certain sample volume is pronounced in one case and hardly observable in another. Glass or fused silica capillaries silylated with diphenyltetramethyldisilazane were found to give optimal retention gaps. They combine thorough and thermostable deactivation with good wettability and low retention power. On the other hand it is very easy to deactivate fused silica capillaries with Carbowax. The resulting retention gaps are suitable for a wide range of applications and are particularly attractive for the analysis of dirty samples which require frequent replacement of the inlet. 相似文献
100.
Summary Retention indices and their energy equivalents were determined for ten alkylthiazoles analysed on the stationary phases Apiezon
L, Triton X-305 and Carbowax 1000. It was found that the energy contributions of identical alkyl groups to the partial molar
free energy of sorption of a molecule are not equivalent. Smaller energy contribututions are due to the α-position of alkyl
groups with respect to the heteroatoms in the thiazole ring (α-effect). This effect was most pronounced for 2-alkylthiazoles.
Higher sorption energies were found for dimethylthiazoles with two methylgroups in a vicinal position. The retention indices
were predicted for ten other di- and tri-substituted methyl, ethyl and propyl thiazoles on the basis of the so-called α- and
ortho-effects. The predicted values are in good agreement with the experimentally determined values.
Dedicated to Prof. Dr. E. sz. Kováts (Ecole Polytechnique Fédérale de Lausanne) on the occasion of his sixtieth birthday. 相似文献