Liquid-solid chromatography adsorption

In liquid-solid adsorption chromatography (LSC) the column packing also serves as the stationary phase. In Tswett s original work the stationary phase was finely divided CaCOa, but modern columns employ porous 3-10-)J,m particles of silica or alumina. Since the stationary phase is polar, the mobile phase is usually a nonpolar or moderately polar solvent. Typical mobile phases include hexane, isooctane, and methylene chloride. The usual order of elution, from shorter to longer retention times, is... 

Kovat s retention index (p. 575) liquid-solid adsorption chromatography (p. 590) longitudinal diffusion (p. 560) loop injector (p. 584) mass spectrum (p. 571) mass transfer (p. 561) micellar electrokinetic capillary chromatography (p. 606) micelle (p. 606) mobile phase (p. 546) normal-phase chromatography (p. 580) on-column injection (p. 568) open tubular column (p. 564) packed column (p. 564) peak capacity (p. 554)... 

Procedures for determining fatty acids in sediments involved liquid-liquid extraction, liquid-solid adsorption chromatography followed by gas liquid chromatographic analysis [10-12], Liquid extractions have been performed with methanol-chloroform [13], methylene chloride [14] and benzene-methanol [15, 16]. Typical liquid-solid adsorbents are silicic acid. Standard gas chromatographic separations for complex mixtures employ non-polar columns packed with OV-1, OV-17, OV-101, SE-30, or glass capillary columns containing similar phases. 

The more recent applications of open-column chromatography in fat-soluble vitamin assays utilize liquid-solid (adsorption) chromatography using gravity-flow glass columns dry-packed with magnesia, alumina, or silica gel. Such columns enable separations directly comparable with those obtained by thin-layer chromatography to be carried out rapidly on a preparative scale. 

RE Majors. Liquid-solid (adsorption) chromatography. In CF Simpson, ed. Practical High Performance Liquid Chromatography. London Heydon and Son, 1976, pp 89-108. 

With binary and ternary supercritical mixtures as chromatographic mobile phases, solute retention mechanisms are unclear. Polar modifiers produce a nonlinear relationship between the log of solute partition ratios (k ) and the percentage of modifier in the mobile phase. The only form of liquid chromatography (LC) that produces non-linear retention is liquid-solid adsorption chromatography (LSC) where the retention of solutes follows the adsorption isotherm of the polar modifier (6). Recent measurements confirm that extensive adsorption of both carbon dioxide (7,8) and methanol (8,9) occurs from supercritical methanol/carbon dioxide mixtures. Although extensive adsorption of mobile phase components clearly occurs, a classic adsorption mechanism does not appear to describe chromatographic behavior of polar solutes in packed column SFC. 

R. E. Boehm and D. E. Martire, A unified theory of retention and selectivity in liquid chromatography. 1. Liquid-solid (adsorption) chromatography , J. Phys. Chem. 84 3620-3630(1980). 

One is quantitative TLC by reflective scanning (4J, and the other is an automated continuous flow system that utilizes liquid-solid adsorption chromatography coupled with selective detectors ( 5) (61-... 

The separation of ionizable compounds by liquid-solid adsorption chromatography has long presented difficulties and the separation of un-... 

Modern liquid chromatography can be carried out in any of the classical modes, e.g., liquid-solid adsorption chromatography, liquid-liquid partition chromatography, reversed-phase chromatography, ion-exchange chromatography, and gel-permeation (size exclusion) chromatography. 

The length required for a certain efficiency mainly decides the size of an analytical column. In preparative separations by liquid-solid adsorption chromatography, the quantity of the adsorbent required for a given load also comes into picture. The value of 00,1 fixes the quantity of adsorbent required for a given sample size, and this translated into practical terms implies that the amount of sample that is placed on a given column does not cause overloading of the column. Also, it is to be kept in mind that H increases in an overloaded column. Sample size, therefore, should be less than 00,1 of the column to achieve (i) constant sample migration rates and (ii) maximum separation efficiency. 

J.H. Knox and J. Jurand, Separation of Tricyclic Psychosedative Drugs by High Speed Ion Pair Partition and Liquid-Solid Adsorption Chromatography, J. Chromatogr., iOJ.- 311 (1975). 

Source From Column efficiency in liquid-solid adsorption chromatography. H.E.T.P. [height equivalent to a theoretical plate] values as a function of separation condition, in Anal. Chem. ... 

SOLVENT STRENGTH (e ). A measure of the polarity of a solvent for liquid-solid adsorption chromatography. It is based on the free energy of adsorption onto a standard surface. Values for common solvents range from 0.00 (pentane) to 0.95 (methanol). 

Liquid-Solid (Adsorption) Chromatography This type of chromatography is based on the competition between the molecules of the sample and the molecules of the mobile phase for adsorbent sites on the active adsorbent surface of the stationary phase. To alter adsorptive activity, two solvents are used in the mobile phase the principal solvent and the modifying solvent. In most cases, the principal solvent is hexane or dichloromethane and the modifying solvent is water, alcohol, or dimethyl sulfoxide. A modifying solvent is added to the principal solvent to control the absorptive activity of the samples. 

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