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Chromatographic Separations: Maximizing Column Performance for Precise Elution

Explore different methods of chromatography, from gas to liquid, and learn key factors affecting column performance and elution efficiency for optimal results. Understand retention time, resolution, selectivity, and factors influencing chromatographic separations.

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Chromatographic Separations: Maximizing Column Performance for Precise Elution

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  1. Chapter26 An Introduction to Chromatographic Separations Gas Chromatography

  2. 26A General Description of Chromatography 26A-1 Classification of Chromatographic Methods Two ways: Column Chromatography Planar Chromatography a) Liquid chromatography --- Liquid - liquid (LLC) --- Liquid - solid (LSC) --- Liquid - bonded phase (LSB) --- Ion - exchange (IEC) --- Gel - permeation (GPC)

  3. b) Gas chromatography --- Gas - liquid (GLC) --- Gas - solid (GSC) --- Gas - bonded phase c) Supercritical-fluid chromatography d) Electrochromatography

  4. 26A-2 Elution in Column Chromatography Fig. 26-1 Elution Chromatography Fig. 26-2 Concentration profiles of analyte band A and B

  5. 26B Migration Rates of Solutes Fig. 26-3 Improving separation 

  6. 26B-1 Distribution Constants Amobile ⇄ Astationary 26B-2 Retention time tR, tM The average linear rate of solute migration:

  7. 26B-3 The Relationship between Volumetric Flow Rate and Linear Flow Velocity The average linear rate of molecules of the mobile phase: Fig. 26-4

  8. 26B-4 The Relationship between Retention Time and Distribution Constant = u x fraction of time solute spends in mobile phase = u x moles of solute in mobile phase / total moles of solute

  9. 26B-5 The Rate of Solute Migration: The Retention Factor

  10. 26B-6 Relative Migration Rates: The Selectivity Factor. from

  11. 26C Band Broadening and Column Efficiency N = L/H, 1) Plate height, 2) Plate count plate

  12. Fig. 26-6

  13. Fig. 26-8 Effect of mobile-phase flow rate on plate height for LC and GC

  14. The Longitudinal Diffusion Term (Fig. 26-9)

  15. The Stationary-Phase Mass-Transfer Term The Mobile Phase Mass-Transfer Term H = A + B/u + (CS + CM)u A Van Deemter plot  (Fig. 26-10)

  16. Fig. 26-11 Effect of particle size

  17. 26D Optimization of Column Performance 26D-1 Column Resolution (Rs)

  18. 26D-2 The Effect of Retention and Selectivity Factors on Resolution

  19. 26D-3 The Effect of Resolution on Retention Time

  20. Example 26-1 a) b) c)

  21. d) e) f)

  22. 29D-4 Variables That Affect Column Performance Variation in Retention Factor Variation in Selectivity Factor

  23. Fig. 26-13 Effect of retention factor kB on resolution and elution time

  24. 26D-5 The General Elution Problem Fig. 26-14Effect of solvent variation on chromatograms

  25. Fig. 26-15

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