Lecture_13.ppt - Introduction of Analytical Separation In...

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Introduction of Analytical Separation In the vast majority of real analytical problems, we must separate, identify, and measure one or more components from a complex mixture.
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Solvent Extraction Extraction is the transfer of a solute from one phase to another. Suppose that solute S is partitioned between phases 1 and 2. The partition coefficient, K, is the equilibrium constant for the reaction: S (in phase 1) S (in phase 2) 1 2 ] [ ] [ 1 2 S S a a K S S
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pH Effects If a solute is an acid or base, its charge changes as the pH is changed. Usually, a neutral species is more soluble in an organic solvent and a charged species is more soluble in aqueous solution. Remember that a charged species tends to be more soluble in water than in organic solvent. To extract a base into water, use a pH low enough to convert B into BH + . To extract the acid HA into water, use a pH high enough to convert HA to A - .
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Chromatography Chromatography operates on the same principle as extraction, but one phase is held in place (stationary phase) while the other phase moves past it (mobile phase). The mobile phase in chromatography is either a liquid or a gas. The stationary phase is most commonly a viscous liquid chemically bonded to the inside of a capillary tube or onto the surface of solid particles packed in the column. The partitioning of solutes between the mobile and stationary phases gives rise to separation. Fluid entering the column is called eluent. The process of passing liquid or gas through a chromatography column is called elution. Column are either packed or open tubular. A packed column is filled with fine particles of stationary phase. An open tubular column is a narrow, hollow capillary tube with stationary phase coated on the inside wall.
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Types of Chromatography Adsorption Chromatography
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