1. Intro to Chromatographic Separations Chap 26

2. Originally based on separation and identification by color Originally based on separation and identification by color All have in common: All have in common: (a) Stationary phase (a) Mobile phase (eluent) (a) Separation based on differences in migration rates of components of a mixture rates of components of a mixture i.e., The extent of which components are partitioned between mobile and stationary phases between mobile and stationary phases A mobile ⇌ A stationary CHROMATOGRAPHY

3. Quantitative Description of Column Efficiency ► Two related terms used: (1)Plate height, H (2)Number of theoretical plates, N (3)Related by: (Eqn. 26-16) ► Efficiency increases as N ↑ and as H ↓ (Eqn. 26-17) (Eqn. 26-21)

4. Effect of Particle Size on Plate Height Fig. 26-11 Smaller particles reduce H and increase resolution Smaller particles reduce H and increase resolution

5. Optimization of Column Performance Objectives: reduce zone broadening reduce zone broadening alter relative migration rates of solutes alter relative migration rates of solutes Column Resolution (R S ) ≡ (Eqn. 26-24) Recall that efficiency increases as N and as H lengthening column increases N lengthening column increases N lower H by altering flow rate of mobile phase or lower H by altering flow rate of mobile phase or decreasing particle size of packing

6. tRtRtRtR W 2σ2σ2σ2σ (Eqn. 26-17) (Eqn. 26-21)

7. Desire R S > 1.50 The General Elution Problem in Chromatography Fig. 26-15

8. Effect of Solvent Variation on Chromatograms Fig. 26-14

9. Fig. 26-12 The General Elution Problem in Chromatography

10. Solution to the General Elution Problem For liquid chromatography (LC): For liquid chromatography (LC): vary k A by varying composition of mobile phase during elution (gradient elution or solvent programming) vary k A by varying composition of mobile phase during elution (gradient elution or solvent programming) For gas chromatography (GC): For gas chromatography (GC): use temperature programming use temperature programming

11. Result of Temperature Programming Detector Signal

12. Gas Chromatography Chap 27

13. Schematic of a Gas Chromatograph Fig. 27-1

14. A Soap-Bubble Flowmeter Fig. 27-2

15. Sample Port and Injector Must flash volatize and Must flash volatize and introduce sample onto column introduce sample onto column Heated ~ 50°C above BP of Heated ~ 50°C above BP of least volatile compound least volatile compound May be: May be: split (cap columns & GC-MS) split (cap columns & GC-MS) splitless (packed columns) splitless (packed columns) Fig 27-4

16. Column Configurations Two types: Packed columns (L ~ 1 – 5 m) Packed columns (L ~ 1 – 5 m) Open Tubular Column (L ~ 1 – 100 m) Open Tubular Column (L ~ 1 – 100 m)

17. Typical Fused Silica Capillary Column ~20 – 100 m Fig. 27-6