1. Gas Chromatography

2. Chromatography Chromatography Strengths of TLC Weaknesses of TLC
TLC (analytical)
GC (analytical)
Column (preparative)
Strengths of TLC
Weaknesses of TLC

3. GC Basics

4. Gas-Phase Separation
Partitioning between mobile gas and stationary column
Highly effective separations

5. GC
Injection
Column
Detector
Chromatogram

6. GC
Injection

7. GC
Column

8. Column Material Nonpolar Polar For nonpolar material vDW Follows bp
For polar material
Follows polarity

9. GC
Detector
FID
TCD

10. GC
Chromatogram
Retention time
Area under peak

11. GC Parameters and Retention Time
Length of column
Type of column
Temperature profile
Gas flow rate

12. Important GC Questions
What is each peak? (identity)
Characterization
Determination of Unknown
How much of each compound? (Quantity)
Absolute quantity
Relative quantity (product distribution)

13. Identity
Retention time corresponds to Rf
Spike with authentic sample

14. Gas Chromatography/Mass Spec
Identifying components in mixtures
Separation then identification
GC-MS

15. Quantitation
Area under peak corresponds to amount of compound causing signal
Use standard plot to determine absolute concentration
Use percent of total area to determine product distribution
Assumes same response factor

16. Our Experiment
How does the mechanism affect the product distribution of an elimination reaction?
Conduct two elimination reactions
Collect the MIXTURE of products by distillation
Analyze product distribution by GC

17. Practical Aspects