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

1

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.