1. What is the definition of retention time?
- the time taken for a particular compound to travel through the column to the detector, from injection to leaving the column
- the time taken for a particular compound to dissolve in the stationary phase
- the time taken for the gas to be injected into the column and dissolve in the stationary phase
- distance moved by component divided by distance moved my solvent front
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2. Which is NOT a limitation of gas chromatography?
- unknown compounds have no reference Rf value
- substances have the same retention times
- unknown compounds have no reference retention time
- substances can 'hide' beneath each other so will not be detected
3. Why is it important to seal the jar containing the TLC plate?
- to slow the evaporation of the solvent from the TLC plate
- to allow the process to occur
- to prevent bacteria contaminating the sample
- to speed up evaporation of the solvent
4. Which is NOT a use of GC-MS?
- treatment of strokes
- airport security
- forensic analysis
- drug testing
5. What is the benefit of coupling gas chromatography with mass spectrometry
- gas chromatography separates compounds and mass spectra can be compared to a database
- both the retention time and mass spectra can be used to improve the reliability of the identification
- mass spectroscopy separates the compounds and retention times can be compared to a database