04 Principles of Chromatography

04 Principles of Chromatography - IV IV. Principles of...

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IV. Principles of Chromatography HM 614/714 CHM 614/714 Fall 2011
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Chromatography is a logical extension of countercurrent distribution. Instead of a series of discrete extractions being performed, a continuous equilibration of solute between two phases occurs. Figure 1. Schematic presentation of a representation of a chromatographic separation. chromatography the obile phase either a uid r a as The In chromatography, the mobile phase is either a liquid or a gas . The stationary phase is most commonly a liquid coated on the inside of a capillary tube or on the surface of solid particles used to pack a column. Alternatively, the solid particles themselves may serve as a stationary phase. In any case, the partitioning of solutes between the mobile and stationary phases accounts for the separation of solutes, just as it does in countercurrent distribution.
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Terminology In chromatography, separation depends on the amounts of solute in two phases, rather than the solute concentrations. : X phase in i solute total of fraction The Fraction: ) V C x i x i (1) V C V C Φ y i y x i x x : Y phase in i solute total of fraction The (2) V C V C V C Φ y i y x i x y i y i y
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i V ( V ( , V V V and C C D) (or K Since y x R i y x (4) DV 1 DV ) V D( 1 ) V D( Φ or (3) KV 1 KV ) V K( 1 ) V K( Φ R R x y x i x R R x y x i x ) V )( C ( V V y i i y y y (5) DV 1 1 KV 1 1 ) V V )( C C ( 1 V C R R y i i y x x i y X. phase in is i solute of 99% about is That %. 99 , V V and 100 D If i x y x x x X. phase in is i solute of 50% only Now, 50%. , V 01 . 0 V and 100 D If i x y x
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Capacity (retention) factor hase lute f ount tal X phase in solute of amount total k) (or k' X. phase the always is phase stationary the aphy, chromatogr For Y phase in solute of amount total (7) V K k' (6) V C k' x i x i x ) 1 ) ' V V C i i y y y k tardatio r tio tention nown so ) d ) quations (9) ' 1 (8) ' 1 y x k k aphy. chromatogr in R, factor, n retardatio or ratio, retention as known also (9) and (2) Equations
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Selectivity factor (10) k k D D K K α ' ' i i i 1.0. and ) k k or D D (or K K when occurs Separation ' ' j j j and Y phase in is i of 1% and 10 then , 01 . 0 k and 100 k If 4 ' ' j i j i j i X. phase in is j of 1% j i . separation a of quality the of measure a not is alone of value the means This phase. each in is i of 50% and 10 then , 10 k and 1 k If 4 4 ' j ' i (11) 1 k k : when occurs separation Optimum ' j ' i
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Recovery factor (12) Q R : factor recovery the introduced Sandell E.B. o i i i. species of amount initial the is Q & extracted i species of amount the is Q where Q o i i i Enrichment factor R : gives gyration algebraic after , D and DV : Recall (13) R S B R A B B/A V D g gy g D DV 1 R B A R (14) 1 V D α V D V D 1 V D V D 1 S R B R B R A R A R B B/A
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The mobile phase is called the eluent . When it emerges from the end of the column it is called eluate .
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04 Principles of Chromatography - IV IV. Principles of...

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