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

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Presentation on theme: "Gas Chromatography. Chromatography – TLC (analytical) – GC (analytical) – Column (preparative) Strengths of TLC Weaknesses of TLC."— Presentation transcript:

1 Gas Chromatography

2 Chromatography – 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 – For nonpolar material – vDW – Follows bp Polar – 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 R f 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


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