NMR and chromatograpyh Flashcards
NMR
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Two directional chromatography
Column chromatography (CC)
Gas-Liquid Chromatography
Gas-liquid chromatography can be used to separate mixtures of volatile liquids
In gas-liquid chromatography, the mobile phase is an inert gas such as helium and the stationary phase is a high boiling point The time taken for a particular compound liquid absorbed onto a solid
The time taken for a particular compound to travel from the injection of the sample to where it leaves the column to the detector is known as its retention time. This can be used to identify a substance
Some compounds have similar retention times so will not be distinguished
Basic gas-liquid chromatography will tell us how many components there are in the mixture by the number of peaks. It will also tell us the abundance of each substance. The area under each peak will be proportional to the abundance of that component
It is important to use an inert carrier gas such as helium or nitrogen. These will not react with the components being separated in the GC column.
The following factors can be changed to change the retention times of substances being separated: GC column temperature, column length , flow rate. If the temperature or the flow rate is higher then substance will move more quickly through the column to give shorter retention times.
It is also possible for gas-liquid chromatography machine to be connected to a mass spectrometer, IR or NMR machine, enabling all the components in a mixture to be identified.
-MS is used in analysis, in forensics, environmental analysis, airport security and space probe
Most commonly a mass spectrometer is combined with GC to generate a mass spectra which can be analysed or compared with a spectral database by computer for positive identification of each component in the mixture
draw GLC
