chromatography is a method for separating the components of a mixture by differential adsorption...
TRANSCRIPT
GAS CHROMATOGRAPHY
Basic DescriptionChromatography is a method
for separating the components of a mixture by
differential adsorption between a stationary phase
and a mobile (moving) phase
Uses for Chromatography Chromatography can be used to:
• Qualitatively analyze the number of components in a mixture
• Qualitatively identify the components of a mixture using known compounds
• Quantitatively determine the amount of a component in a mixture using standard samples
• Purify individual components by separating them from the other compounds in a mixture
• Mixture is placed on stationary phase• Mobile phase passes over the stationary
phase• Mobile phase carries the individual
components through the stationary phase, depending on their attraction to both of the phases
The Basics
Origin line
Solvent Front
ChromatographedSpot
Rf ratio of spot distance to
solvent front distance
Solvent
Put the spotted paper in a developing tank
Other Kinds of Chromatography Liquid chromatography (includes column
chromatography, thin-layer, and HPLC) Stationary phase: silica, alumina, modified
surfaces, etc. Mobile phase (moving phase): aqueous or
organic solvents Important properties: polarity, charge, etc.
Gas chromatography Stationary phase: a film of a polymer or a wax.
The film must have a low volatility Mobile phase: gas (Helium is a common carrier
gas) Important properties: boiling point, volatility,
etc.
The Basic Gas Chromatograph
Vernier GC
A Chromatogram
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2
3
4
5 1. Acetone2. Methanol3. Butanol4. Acetic Acid5. Butyric Acid
This Week’s Lab Forensic in nature Start with FTIR to decide what compound
class your “unknown” belongs to. Run authentic compounds in that class Separation is based predominantly on
boiling point rather than differential interaction with stationary phase
Run the “unknown” to determine individual identities
Logger Pro UpdateYou need the latest Logger Pro Update to operate the gas chromatograph from your laptop computer.
Go to www.vernier.comSelect DownloadsSelect Logger Pro 3.8.4.2 UpdateInstall Correct version for your OS
Writing the Report• Clearly state your experimental methods and how those
procedures yielded the solution to the problems addressed in the investigation.
• State what data you collected and how you analyzed the data.
• Include properly designed and illustrative data tables. • Show structures of all possible compounds in your
compound class. • Discuss other places that GC might be used beyond this
investigation and those described in the Introduction.