Gas Chromatography, GC

L.O.:

Explain the term: retention time.

Interpret gas chromatograms in terms of retention times and the approximate proportions of the components of a mixture.

Explain that analysis by gas chromatography has limitations

After watching this clip, answer the following questions:

1)What is Gas chromatography (GC) used for?Separate volatile components in a mixture.2) What is the stationary phase? Liquid or solid3) What is the mobile phase?Inert gas4) What is retention time?In gas chromatography is the time for a

component to pass from the column inlet to the detector.

Gas chromatograph separating three components

Gas chromatogram of blood alcohols and related compounds showing retention times.

In pairs brainstorm about the limitations of GC. Think of this analogy...

Limitations of GC: Many chemicals may have the same

retention time.Not all the samples may be separated.

Unknown compound have no reference retention time for comparison.

GC-MSL.O.:

Explain that mass spectrometry can be combined with gas chromatography in GC–MS to provide a far more powerful analytical tool than gas chromatography alone.

Explain that the mass spectra generated can be analysed or compared with spectral databases for positive identification of a component.

• State the use of GC–MS in analysis in forensics, environmental analysis, airport security and space probes

Homework

1) Do a PowerPoint explaining a use of GC-MS (1-2 slides).

2)Upload the PowerPoint into the HW section of the wiki (you will need to request membership first). Save as “yourname-GCMS”.

3) Prepare to do a 1 minute presentation using your PowerPoint

Stages in GC–MS

Stages in GC–MS

GC-MS

The separated components are directed into a mass spectrometer.

The generated mass spectrum is unique and definitive for a single compound.

In pairs brainstorm about uses of Gas chromatography (GC)

In group of 4:

1) in each post-it write a strength or limitation of either GC or GC-MS.

2) Stick it in the corresponding part of the wall.