Gas Chromatography Flashcards
UV-vis spectroscopy
A detection method
A flow cell passes eluted compounds through a UV-spec, giving a characteristic graph of absorbance peaks
Fluorescence spectroscopy
A detection method
Used in specialised experiments only
The eluted compounds must have fluorescence, but this method is more sensitive
Mass spectroscopy
A detection method
The eluent is fed into a mass spectrometer, the mass of the compound is then detected according to change, giving an m/z readout
Gas chromatography
Separates compounds by volatility and their interaction with the stationary phase
GC setup
Carrier gas = usually helium
Injector = loads sample directly into a heating block to volatise the compounds
Mobile phase = uses as a carrier, rather than for separation, usually helium or argon
Oven = keeps the compounds volatile
Long column = aids separation in GC
GC elution
Compounds in GC are eluted using a heat gradient
Sample injection
Prior to injection fluoroacetyl-butyl ester or similar compounds are used to increase volatility of the sample
A Hamilton syringe is then used to inject very small, accurate volumes into the system
Detection in GC
Detection in GC is performed using flame ionisation
The collector is supplied with air and hydrogen and ignited
This converts the sample into ions which can be detected by an electrical current
Limitations of GC
The sample is always destroyed
Applications of GC
- Lipidomics
- Metabolomics
- Carbohydrate detection
- Detection of drugs
Chromatographic resolution
A quantitative measure of how well two elution peaks can be differentiated in a chromatographic separation
Factors affecting chromatographic resolution
- Column length (longer is better ;)))))
- Matrix characteristics
- Eluting solvent
- Elution gradient (shallower is better)
- Flow rate (slower is better)
- Temperature
Proteomics
Determination of the proteins of a cell
Lipidomics
The global pattern of lipids
Metabolomics
Determination of any compound in the cell with a mass <2000Da
