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Gang Wang Instrumental_Week10-12_CH26_28-2010

Gang Wang Instrumental_Week10-12_CH26_28-2010 - Chapter 26...

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Chapter 26: An Introduction to Chromatographic Separations Column Chromatography Migration Rates Distribution Contstants Retention Times Selectivity Factor Zone Broadening & Column Efficiency Optimizing Performance Resolution Intro to Chromatography Chromatography is a separation technique Many determinations involve separation followed by analysis Chromatography electrophoresis HPLC & GC are our primary focus Also discuss low pressure column chromatography & TLC (thin layer) All chromatographic techniques have Stationary phase – solid or viscous liquid phase typically in a column Mobile phase – moves sample in contact with stationary phase
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Chromatography: sample transported by mobile phase electrostatic or van der Waals' some components in sample interact more strongly with stationary phase and are more strongly retained sample separated into zones or bands Elution Chromatography: flushing of sample through column by continual mobile phase (eluent) addition migration rate fraction time spent in mobile phase Planar chromatography - flat stationary phase, mobile phase moves through capillary action or gravity Column chromatography - tube of stationary phase, mobile phase moves by pressure or gravity
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Overview of chromatographic process – packed column Inject at t o Separate t 1 to t 3 Detect at t 4 Å Resulting chromatogram A & B retained by column differently B has higher K B takes longer to elute from column Detector sees A first then B Peak heights & peak areas are proportional to conc. Band broadening
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