February 8th Quiz Flashcards
Name the two types of GC columns
Packed and Capillary
Describe the simpler of the two GC columns
The packed column is made of tubing packed with small, uniform size, inert support coated with a thin film of nonvolatile liquid.
Describe the more complicated of the two GC columns
The capillary column is made of fused silica capillary tube coated in the interior wall with polymer.
Which GC column is better? What are its limitations?
Capillary columns give better separations and can separate complex mixtures containing many compounds, but they require more sensitive detectors.
Name the two types of GC detectors
The two types of detectors are TC (thermal conductivity) and FID (flame ionization detector).
Which detector works with which column?
The TC detector works with a packed column and the FID works with a capillary column.
Describe the GC detector with the smaller acronym
In a TC detector, the column gas flow cools a heated filament and the change in temperature causes a change in electrical resistance. The difference between that and the reference (only the gas) is used.
Describe the GC detector with the bigger acronym
In a FID detector, the sample is burned in a H2 flame creating ions that cause the flame to conduct current, resulting in a signal.
What is the general effect of GC column temperature on separation and resolution?
The separation of peaks is determined by the column temperature: as it increases, the peaks elute more rapidly and separation decreases.
What is the effect of a low GC column temperature?
At low column temperatures, compounds with lower boiling points spend more time in the mobile phase than those with higher boiling points. The lower boiling compounds move faster and come off the column sooner.
What is the effect of a high GC column temperature?
At high column temperatures, all compounds spend more time in the mobile phase, causing all compounds to move faster.
