Chromatography
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What are the components of the moving phase in TLC?
Solvent The solvent carries the samples up the TLC plate.
What is the stationary phase in TLC made of?
Silica gel or alumina on aluminum, glass, or plastic The stationary phase interacts with the compounds being separated.
What is the purpose of adding a fluorescent compound to the TLC plate?
To aid in visualisation under UV light
Why should TLC plates be held by the edges?
To prevent contamination from hands
Why must the solvent level be below the baseline in TLC?
So the sample spots don’t dissolve in the solvent
What causes the solvent to rise in TLC?
Capillary action
When should the TLC plate be removed from the chamber?
When the solvent front is ~1cm from the top
How are spots visualized in TLC using UV light?
The fluorescent background glows and sample spots quench the glow
What is another method to visualize TLC spots besides UV?
Using a stain or developing agent like ninhydrin
What is Rf in chromatography?
The ratio of the distance moved by the compound to the distance moved by the solvent front
How does polarity affect movement in TLC?
Less polar compounds move further because they interact less with the polar stationary phase, while more polar compounds move less due to stronger attraction (Stationary phase tnends to be polar)
Can TLC be used for paper chromatography?
Yes
What are common uses of Rf values?
Compound identification and monitoring reactions
What is the apparatus called in chromatography?
Chromatograph
What is the pattern of separated substances called?
Chromatogram
What does retention time refer to?
Time a component stays in the column
What is chromatography in general terms?
A technique for separating mixtures based on affinities to phases
What is the moving phase in gas chromatography (GC)?
Carrier gas (e.g., He or N₂) Usually He
What is the stationary phase in GC?
Non-volatile liquid film on inert powder in a coiled tube
How is the sample introduced in GC?
Injected in vaporized form into the column
What does longer retention time indicate in GC?
Stronger interaction with the stationary phase
What affects retention time and resolution in GC?
Gas flow rate, column length, and operating temperature
How does gas flow rate affect resolution in GC?
Higher flow rate = lower retention time = lower resolution
How does column length affect resolution in GC?
Longer column = higher resolution