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81.
Roger M. Smith 《Chromatographia》1982,16(1):155-157
Summary The pungent principles of ginger and grains of paradise are examined using a reversed-phase HPLC column. An electrochemical detector is used to selectively detect the phenolic gingerols and shogaols. The retention indices of the compounds are compared using methanowater and acetonitrile-water as eluents.Presented at the 14th International Symposium on Chromatography London, September, 1982 相似文献
82.
83.
Molecular parameters and retention characteristics of unsubstituted polyaromatic hydrocarbons in HPLC 总被引:1,自引:0,他引:1
Summary The present research studies the possibility of using the correlation dependence between molecular parameters of unsubstituted
polyaromatic hydrocarbons (PAH) and their retention in reversed-phase liquid chromatography to optimize the conditions for
the separation and identification of unknown peaks on the chromatograms of multicomponent mixtures. A linear correlation equation,
that takes the number and environment of the carbon atom in the PAH molecule into account as well as the differences in the
specific interactions of isomeric molecules with polar eluent, has been proposed. The adequacy of the proposed PAH retention
model was verified by comparing the calculated retention values with the experimental data. The possibility of identifying
unsubstituted PAH according to the number of carbon atoms of various types and according to the values of the molecules lengths
(calculated on the basis of the retention of these substances under different eluent compositions) was exemplified by various
chromatographic systems (reversed phase-eluent-PAH molecules). 相似文献
84.
With a set of equations for the self-consistent large-signal interaction derived in this paper, the bandwidth characteristics of a non-reflection-type gyrotron-TWA using a tapered waveguide and tapered magnetic field system have been analysed. Numerical calculations indicate that under defined conditions an instantaneous bandwidth of nearly 10 % at a center frequency of 35 GHz with a length of the order of only8 cm of the rf interaction region could be achieved. 相似文献
85.
86.
Mehrzad Mehran William J. Cooper Nahid Golkar Michael G. Nickelsen Eric R. Mittlefehldt Edward Guthrie Walter Jennings 《Journal of separation science》1991,14(11):745-750
The retention behavior of a heterogeneous group of solutes has been examined on seven different stationary phases under isothermal and temperature-programmed conditions. Both ΔHv (enthalpy of solute vaporization from the stationary phase) and ΔSv (entropy of solute vaporization from the stationary phase) values were determined for each solute – stationary phase combination under isothermal conditions. Both program rate and carrier gas velocity were shown to affect solute elution order. Unless these and other experimental factors discussed are controlled, column equivalency studies based on solute elution order have dubious value. 相似文献
87.
Summary The true meanings of the so-called corrected retention volume and the specific retention volume are explained in the light of the recent paper by Davankov. 相似文献
88.
Summary The addition of appropriate concentrations of an organic amine and an alkylsulphonate to the mobile phase in reversed-phase, ion-pair liquid chromatography can introduce unique selectivity in to the chromatographic system allowing separation of complex mixtures of basic, acidic and neutral compounds. As an example, the methodology for a specific stability-indicating determination of propantheline bromide, a quaternary ammonium anticholinergic agent, on several reversedphase stationary phases, was developed. The retention mechanism was studied and it was concluded that both ion-interaction processes and ion-exchange processes were involved in the separation technique developed with two counterions of opposite charge in the eluent. 相似文献
89.
A new additive scheme is proposed for the precalculation of gas chromatographic retention indices of complex organic compounds. The principal feature of this approach is the absence of previously calculated I increments for any structural fragments or functional groups in the molecule. Instead, arithmetical operations involving I values of simpler structural analogues of target compounds are used directly. I precalculation for polychlorinated hydroxybiphenyls (839 congeners) on the HP-5 stationary phase was chosen as one of the most important applications of the method under discussion. Such a large number of congeners cannot be obtained as reference samples and their gas chromatographic (GC)-mass spectrometric (MS) identification should therefore be based currently on precalculated I values. 相似文献
90.
Summary Computer-assisted procedures for the one-parameter optimization of the surfactant concentration and the concentration of urea or D-glucose as modifiers in micellar electrokinetic capillary chromatography have been developed. These procedures permit a rapid optimization of one parameter on the basis of only two experiments. Predicted values are compared to empirically obtained optimum values. The influence of the modifier concentration on the critical micelle concentration of sodium dodecyl sulfate was experimentally determined in buffers commonly employed in micellar electrokinetic chromatography. The alteration of retention factors of solutes caused by the influence of urea addition on the critical micelle concentration of sodium dodecyl sulfate was calculated under the assumption of constant distribution coefficients and compared to experimentally obtained values. It was demonstrated that the addition of urea or of D-glucose does not alter the phase ratio substantially. 相似文献