Other Types of Liquid Chromatography

New stationary phases for specific purposes in chromatographic separation are being continually proposed. Charge transfer adsorption chromatography makes use of a stationary phase which contains immobilised aromatic compounds and permits the separation of aromatic compounds by virtue of the ability to form charge 

In metal chelate adsorption chromatography a metal is immobilised by partial chelation on a column which contains bi- or tri- dentate ligands. Its application is in the separation of substances which can complex with the bound metals and depends on the stability constants of the various ligands (Porath, Carlsson, Olsson and Belfrage Nature 258 598 1975 Loennerdal, Carlsson and Porath FEBS LETT 75 89 1977). 

The affinity method may be biospecific, for example as an antibody-antigen interaction chemical as in the chelation of boronate by m-diols, or of unknown origin as in the binding of certain dyes to albumin. 

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Due to the fact that different end groups can be formed during the polycondensation, the reaction products may exhibit a functionality-type distribution in addition to the molar mass distribution. Although SEC is suitable to analyze the molar mass distribution, it does not yield information on different end groups. For the determination of the functionality-type distribution, other types of liquid chromatography must be used. 

Chromatography is a separation process in which the sample mixture is distributed between two phases in the chromatographic bed (column or plane). One phase is stationary whilst the other passes through the chromatographic bed. The stationary phase is either a solid, porous, surface-active material in small-particle form or a thin film of liquid coated on a solid support or column wall. The mobile phase is a gas or liquid. If a gas is used, the process is known as gas chromatography the mobile phase is always liquid in all types of liquid chromatography, including the thin-layer variety. 

Principles and Characteristics Column liquid chromatography is the parent of all other types of chromatography. The technique used by Tswett is now called classical open-column liquid chromatography or simply LC. In column chromatography the stationary phase is contained in a column and the mobile phase flows... 

The separation of chemical species by size exclusion chromatography is more reproducible than any other type of chromatography. Once the SEC columns, the mobile phase (most often a pure solvent like THF or toluene), and the flow rate are selected, the retention volume (or retention time assuming the flow rate does not change) is primarily a function of linear molecular size, which can be obtained from the valence bond structure if the compound is known. Some of the chemical species can interact with the solvent forming complexes with an effective linear size greater than that of the molecule. This causes the expected retention volume, based on "free" molecular structure, to shift to a lower but very reproducible retention volume. Phenols in coal liquids form 1 1 complex with THF (9,10) and carry the effective linear molecular size to increase. As a result phenolic species elute sooner than expected from their... 

The analysis of individual chemical constituents in distilled spirits currendy is performed using gas chromatography (gc) and high pressure liquid chromatography (hplc). Although other types of instrumental analyses have yielded much information regarding the chemical constituency of distilled spirits, the combination ofgc and hplc has allowed hundreds of different chemical components of distilled spirits to be individually identified and accurately quantified. 

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