Chromatography separation, basic principle

Capillary electrophoresis, although carried out in a capillary tube, is not fundamentally a chromatographic technique. It evolved somewhat tenuously from the traditional gel electrophoresis and, as the separation procedure differs considerably from chromatography, the basic principles involved in an electrophoretic separation will be briefly described. 

The basic principle of chromatography separations can be described by thermodynamics using the distribution coefficient K (12) ... 

Gas-Liquid Chromatography. In gas-liquid chromatography (GLC) the stationary phase is a liquid. GLC capillary columns are coated internally with a liquid (WCOT columns) stationary phase. As discussed above, in GC the interaction of the sample molecules with the mobile phase is very weak. Therefore, the primary means of creating differential adsorption is through the choice of the particular liquid stationary phase to be used. The basic principle is that analytes selectively interact with stationary phases of similar chemical nature. For example, a mixture of nonpolar components of the same chemical type, such as hydrocarbons in most petroleum fractions, often separates well on a column with a nonpolar stationary phase, while samples with polar or polarizable compounds often resolve well on the more polar and/or polarizable stationary phases. Reference 7 is a metabolomics example of capillary GC-MS. 

The basic principles of adsorption, ion-exchange, and affinity resins have been explained in the previous section on adsorption. Chromatography is similar to adsorption because both involve the interaction between solute and solid matrix. However, they are different in a sense that chromatography is based on the different rate of movement of the solute in the column, while adsorption is based on the separation of one solute from other constituencies by being captured on the adsorbent. 

There are several types of chromatography however, they all follow the same basic principles. The simplest kind is paper chromatography. To separate the different-coloured dyes in a sample of black ink, a spot of the ink is put on to a piece of chromatography paper. This paper is then set in a suitable solvent as shown in Figure 2.26. 

For the experimental investigation of volatile transactinide compounds two different types of chromatographic separations have been developed, thermochromatography and isothermal chromatography. Sometimes also combinations of the two have been applied. The basic principles of thermochromatography and isothermal chromatography are explained in Figure 7. 

Ion Chromatography, edited by James G. Tarter 38. Chromatographic Theory and Basic Principles, edited by Jan Ake Jonsson 39. Field-Flow Fractionation Analysis of Macromolecules and Particles, Josef Janca 40. Chromatographic Chiral Separations, edited by Morris Zief and Laura J. Crane 41. Quantitative Analysis by Gas Chromatography, Second Edition, Revised and Expanded, Josef... 

The basic principle of one-column process is identical to four-zone SMB. The performance of the process for the amino acids separation was compared with four-zone SMB by computer simulation using Aspen Chromatography. The system and operating parameters are listed in Table 1. It was set that T2, T3 and T4 are initially filled with desorbent and T1 is empty in the simulation. Liquid in each tank is ideally mixed. Liquid of the average solute concentration in a tank is introduced into the column. The simulated concentration profile of two amino acids in the one-column process is presented in Figure 3. 

F. BressoUe, M. Audran, T.-N. Pham, and J-J. Vallon, Cyclodextrins and enantiomeric separations of drugs by liquid chromatography and capillary electrophoresis Basic principles and new developments, J. Chro-matogr. B 657 303 (1996). 

The purpose of this article was to provide the reader with a basic understanding of capillary electrophoresis and to describe how a technique such as MEKC uses basic principles of chromatography to perform separations which are not possible electrophoretically. As the applications for electrokinetic chromatography rapidly expand, the future direction will develop on two fronts ... 

General references on chromatography include P. Sewell and B. Clarke. Chromatographic Separations. New York Wiley, 1988 Chromatographic Theory and Basic Principles, J. A. Jonsson, Ed. New York Marcel Dekker, 1987 A. Braithwaite and F. 1. Smith, Chromatographic Methods, 5th ed. London Blackie, 1996. 

Skill 12.1 Demonstrating knowledge of various separation techniques (e.g., distillation, filtration, chromatography) and their basic principles... 

Chromatography, the process by which the components of a mixture can be separated, has become one of the primary analytical methods for the identification and quantification of compounds in the gaseous or liquid state. The basic principle is based on the concentration equilibrium of the components of interest, between two immiscible phases. One is called the stationary phase, because it is immobilized within a column or fixed upon a support, while the second, called the mobile phase, is forced through the first. The phases are chosen such that components of the sample have differing solubilities in each phase. The differential migration of compounds lead to their separation. Of all the instrumental analytical techniques this hydrodynamic procedure is the one with the broadest application. Chromatography occupies a dominant position that all laboratories involved in molecular analysis can confirm. 

Chromatography encompasses a number of variations on the basic principle of the separation of components in a mixture achieved by a successive series of equilibrium stages. These equilibria depend on the partition or differential distribution of the individual components between two phases a mobile phase... 

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