Search results for "Capacity factor"
showing 6 items of 16 documents
Selectivity tuning in pressurized-flow electrochromatography
1996
Abstract Pressurized-flow electrochromatography (PEC) is a developing separation technique in which both a pressure gradient and an electric field are applied across a packed capillary. In this work we present new results illustrating the principles and the potential of PEC. Home-made capillary columns with silica-based reversed phase packings were operated under PEC conditions separating low molecular weight analytes. Compared to the purely pressure-driven system enhanced selectivity for the charged analytes was observed. It is shown that the retention time of a retained cationic analyte in PEC can be calculated using the chromatographic capacity factor and the electrophoretic mobility of …
Reliability of the capacity factor at zero micellar concentration and the solute-micelle association constant estimates by micellar liquid chromatogr…
1997
In micellar liquid chromatography, MLC, the hydrophobicity of a compound is the predominant effect on its retention and interaction with micelles. The capacity factors at zero micellar concentration, k(m), and the solute-micelle association constants, KAM- have recently been used as the hydrophobicity index of compounds and are important in QSAR studies. These parameters could be estimated (by regression) from the (k,[M]) data, where k is the capacity factor and [M] the surfactant concentration minus the critical micelle concentration. km and KAM are usually obtained from the intercept and slope, respectively, of the plot 1/k vs. [M]. In spite of the general use of this equation, the reliab…
Development of predictive retention-activity relationship models of tricyclic antidepressants by micellar liquid chromatography.
1999
The distribution of tricyclic antidepressants from plasma to brain, where these drugs exert their main clinical action, and other organs is related to transport events across the cell membranes of the different tissues. It could be expected that all the molecular features that condition the transport processes (mainly hydrophobicity and molar total charge) also control the pharmacokinetic and biochemical behavior. Micellar liquid chromatography (MLC) has been proposed to emulate in vitro the partitioning process in the biomembranes. The use of micellar solutions of Brij35 as mobile phases in reversed-phase liquid chromatography has proven to be valid to predict the biological activities of …
Neptunium(V) Sorption and Diffusion in Opalinus Clay
2009
The sorption and diffusion behavior of 8 x 10(-6) M Np(V) in Opalinus Clay (OPA) with synthetic pore water (pH 7.6) as mobile phase was studied under ambient conditions by batch and diffusion experiments, respectively. The Kd value determined by batch experiments with OPA suspensions is equal to 0.025 +/- 0.005 m3/kg. The diffusion-accessible porosity epsilon of intact OPA as determined by through- and out-diffusion experiments with tritiated water (HTO) is equal to 0.15 +/- 0.01. The diffusion coefficient De and the rock capacity factor alpha of 22Na+ in OPA were measured by through-, out-, and in-diffusion experiments and asserted the reliability of these diffusion techniques. For the dif…
Retention behaviour of volatile compounds in normal-phase high-performance liquid chromatography on a diol column
1993
Abstract Retention data on a diol column for over 300 compounds of the chemical classes usually contained in aroma extracts of plants and foodstuffs are reported. A concept that largely corrects for minor fluctuations of the mobile phase composition and of the flow-rate was used to measure capacity factors. The mobile phase was composed of pentane and diethyl ether. The high volatility of these two solvents makes the method perfectly adaptable to the prefractionation of aroma extracts and the semi-preparative isolation of compounds. Non-polar compounds such as hydrocarbons are not retained on diol. Polar compounds can be readily eluted, with the exception of strong acids and bases.
Multivalent ion-exchange model of biopolymer chromatography for mass overload conditions
1991
Abstract The simple model of multivalent ion-exchange biopolymer chromatography is analyzed on the basis of classical quasi-chemical temperature. The rigorous isotherm equation deduced from the stoichiometric displacement model (SDM) was used to stimulate the migration of a solute through the chromatographic column in the isocratic and gradient elution modes. The peak profiles generated for various sample sizes were compared with those obtained on the basis of a Langmuir isotherm. Peak tailing increases with the value of the exponent Z, defined as the ratio of the protein valency to the displacing counter-ion valency. For large Z the asymmetries due to the non-linearity of the isotherm are …