Introduction to chromatography

Analysis of complex mixtures often requires separation and isolation of components or classes of components. Examples in noninstrumental analysis include extraction, precipitation, and distillation. These procednres partition components between two phases based on differences in the components physical properties. In liquid-liquid extraction, components are distributed between two immiscible liqnids based on their similarity in polarity to the two liquids (i.e., like dissolves like ). In precipitation, the separation between solid and liquid phases depends on relative solubility in the liqnid phase. In distillation, the partition between the mixture liquid phase and its vapor (prior to recondensation of the separated vapor) is primarily governed by the relative vapor pressures of the components at different temperatures (i.e., differences in boiling points). When the relevant physical properties of the two components are very similar, their distribution between the phases at eqnilibrinm will result in slight enrichment of each in one of the phases, rather than complete separation. To attain nearly complete separation, the partition process must be repeated multiple times and the partially separated fractions recombined and repartitioned multiple times in a carefully organized fashion. This is achieved in the laborious batch processes of countercurrent liquid-liquid extraction, fractional crystallization, and fractional distillation. The latter appears to operate continuously, as the vapors from a single equilibration chamber are drawn off and recondensed, but the equilibration in each of the chambers or plates of a fractional distillation tower represents a discrete equilibration at a characteristic temperature. 

A procedure called chromatography automatically and simply applies the principles of these fractional separation procedures. Chromatography can separate very complex mixtures composed of many very similar components. The various types of chromatographic instrumentation 

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Fig. 8.6 Reproduced from D. Abbott and R. S. Andrews, An Introduction to Chromatography, Longman, London, 1965.

R. Boyer, Concepts in Biochemistry (1999), Brooks/Cole (Pacific Grove, CA), pp. 102-104. An introduction to chromatography. 

An introduction to chromatography. http //www.nidlink.com/ jffomm/chem301/chem302p.htm Review of lipid structure and function, http //www.compusmart.ab.ca/plambeck/ che/p265/p06211.htm Lipid structure and function. 

Table 30-1 lists a variety of separation methods that are in common use, including (1) chemical or electrolytic precipitation, (2) distillation, (3) solvent extraction, (4) ion exchange, (5) chromatography, (6) electrophoresis, and (7) field-flow fractionation. The first four are discussed in Sections 30A through 30E of this chapter. An introduction to chromatography is presented in Section 30F. Chapters 31 and 32 deal with gas and liquid chromatography, respectively, while Chapter 33 deals with electrophoresis, field-flow fractionation, and other separation methods. 

In Part VI, Chapter 30 is now a general introduction to separations. It includes solvent extraction and precipitation methods, an introduction to chromatography, and a new section on solid-phase extraction. Chapter 31 contains new material on molecular mass spectrometry and gas chromatography/mass spectrometry. Chapter 32 includes new sections on affinity chromatography and chiral chromatography. A section on LC/MS has been added. A new Chapter 33, Miscellaneous Separation Methods, has been included. It introduces capillary electrophoresis and field-flow fractionation. 

HI. Haer, F. C., An Introduction to Chromatography on Impregnated Glass Fiber. Ann Arbor Sci. Publ., Ann Arbor, Michigan, 1969. 

An Introduction to Chromatography Critical Readings in Chemistry A Guide to Understanding Basic Organic Reactions An Introduction to Reaction Kinetics Orbitals and Chemical Bonding... 

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