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141.
The influence of a water vapor admixture in helium, nitrogen, and carbon dioxide on capacity coefficients of C3−C5 alcohols and pyridine during chromatography process in capillary columns with polar (PEG-20M) and nonpolar (SE-30) stationary
phases was studied. The introduction of a water admixture into the carrier gas, increases the capacity coefficient of polar
organic compounds on the capillary column with PEG-20M and has almost no effect on this value in the case of SE-30. The change
in retention of polar organic compounds on the capillary column with the PEG-20M polar phase occurs due to a change in the
properties of the stationary phase when it adsorbs water from the mobile phase.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2258–2261, November, 1998. 相似文献
142.
143.
Summary This paper reports the qualitative and quantitative effects of the column pressure drop on the retention of lipid components in a serially coupled capillary column SFC system. The contribution of the pressure drop consists of two components, the density effect and the flow effect. The magnitude of the flow effect,i. e. the change in retention which results from changes in the flow-rate when column pressures are changed, is determined by the difference in single column analyte k values. The effect will be positive compared with the uncorrected retention values when the column with largest k value is closest to the injector. With the columns in reversed order, the effect will be negative. The contribution from the density effect always resulted in larger coupled column k values and was in most instances of more significance than the flow effect component. Values calculated with and without pressure drop correction have been compared and it has been shown that for most of the eighteen model lipid compounds investigated, the deviations from the experimental retention factors were smaller when pressure drop corrections were made. 相似文献
144.
Naglaa M. El Kousy 《Mikrochimica acta》1998,128(1-2):65-68
The most commonly used antidiabetic sulfonylurea drugs, gliclazide, glipizide and glibenclamide, were determined using stability-indicating densitometric methods. The degradation products were prepared by acid hydrolysis of the intact drugs. Thin layer chromatography was carried out using silica gel 60 F254 plates and different mobile phases, followed by scanning of the developed chromatograms. Mixtures of the investigated drugs and their degradation products were prepared and analysed using the proposed methods, with recovery in the range 100.4–101.0% and RSD in the range 0.6–0.7%. Pharmaceutical dosage forms were assayed and found to give results of the same accuracy and reproducibility as official or reference methods. 相似文献
145.
中药色谱指纹图谱的小波变换与分形 总被引:1,自引:0,他引:1
为了提取中药指纹图谱共性的特征,将小波变换与分形维数相结合,对同一种中药指纹图谱进行小波变换,并求其分形维数,利用相关系数法,考察了分形维数对温度和测试条件的抗干扰能力,结果表明小波变换的分形维数对温度变化具有较好的抗干扰能力,可以作为描述中药指纹图谱共性的特征. 相似文献
146.
147.
Summary A general chromatographic model has been set up starting from a set of equations based on the concept of the velocity of a
solute along the column. The composition of the mobile phase is taken into account solely as a numerical factor entering into
suitable equations and totally independent of the chemical-properties of the constituents. A few isocratic experimental runs
are necessary as input data, and subsequently a small amount of computational effort is sufficient to make predictions of
retention times under gradient elution conditions for solutes of whatever chemical structure. The prediction errors are dependent
on the steepness of the linear gradient chosen but are, in any case, acceptably low. 相似文献
148.
Summary The separation by thin-layer chromatography (TLC) is reviewed for 25 pairs of tetrasubstituted-ethane diastereomers on silica.
A total of 50 different mobile phases were used in order to define the basis of solvent selectivity for these separations.
Separation factors (α) for various diastereomeric pairs are determined mainly by the relative localization of the strong solvent
in these binary-solvent mobile phases (as measured by the mobile-phase parameter m). Relative retention of the diastereomers
expressed by positive vs. negative values of α appear understandable on the basis of steric hindrance to adsorption and solvent-solute
localization.
Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984 相似文献
149.
150.
W. J. F. van der Vijgh H. B. J. van der Lee G. J. Postma H. M. Pinedo 《Chromatographia》1983,17(6):333-336
Summary A highly sensitive on-line amperometric detection of platinum compounds in HPLC effluents was possible with the use of a polarographic detector. For TNO-1 (=cis-1,1-di(aminomethyl)-cyclohexane Pt(II)chloride) a linear dynamic range of at least three decades could be obtained (0.034–108g TNO-1/ml) with a detection limit of three times the noise signal at 0.7 ng TNO-1 (20ng Pt/ml). The sensitivity was 0.1 nA/ng TNO-1 (0.2nA/ng Pt). The within-day presicion was 1.1% at a concentration of 10.8g TNO-1/ml (n=10). With this system the compatibility was measured of TNO-6 with infusion fluids. In 0.15 M NaCl, TNO-6 (=cis-1,1-di(aminomethyl)-cyclohexanePt(II)sulphate) was converted into TNO-1 within 40 minutes. Molecular changes of TNO-6 were also observed in a 5% aqueous glucose solution. 相似文献