Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
31 Cards in this Set
- Front
- Back
|
thin layer chromatography
|
a chromatography technique used to separate mixtures
|
|
|
chromatography
|
collective term for a set of laboratory techniques for the separation of mixtures.
It involves passing a mixture dissolved in a "mobile phase" through a stationary phase, which separates the analyte to be measured from other molecules in the mixture based on differential partitioning between the mobile and stationary phases |
|
|
In this experiment, the liquid mobile phase is simply the:
|
solvent
|
|
|
What causes the solvent to rise on the TLC?
|
capillary action (which pulls along the components present in the sample)
|
|
|
Why are the components pulled up the TLC at different speeds?
|
This is because of their specific interactions with the stationary phase
|
|
|
When should the plate be removed from the chamber? What is this level called?
|
When the solvent has traveled 80-95% of its length.
This level is called the solvent front. |
|
|
What does TLC stand for?
|
Thin-layer chromatography
|
|
|
What is ε ?
|
polarity
|
|
|
ε is what Greek letter?
|
epsilon
|
|
|
What is Rf?
|
ratio to the front
|
|
|
adsorption
|
the process by which molecules of a gas, liquid, or solid in solution interact with the adsorbent
|
|
|
adsorbent
|
the molecules on the surface of a solid
|
|
|
What causes adsorption?
|
electrostatic forces between adsorbent and sample
ex. dipole-dipole, ion-dipole interactions, and H-bonds |
|
|
binding site
|
the place on the surface of the adsorbent where the sample binds
|
|
|
What are the most commonly used adsorbents in TLC
|
silica gel and alumina
|
|
|
What is alumina?
|
aluminum oxide
Al2O3 |
|
|
kieselguhr
Celite |
both are diatomaceous earths with very limited adsorption strength
|
|
|
adsorptivity
|
adsoprtion strength
|
|
|
activation
|
the removal of water at high temperatures
|
|
|
dielectric constant is usually taken as an indicator of:
|
polarity
|
|
|
Why should the marks on the TLC plate be made with pencil and not ink?
|
The components of ink may separate during the run and interfere with the TLC analysis.
|
|
|
development
|
the process of allowing the mobile phase to run along the plate
|
|
|
Rf
|
ratio to the front
= (distance traveled by spot) / (distance traveled by solvent) |
|
|
What is indicated if a spot streaks or runs with a tail?
|
That too much sample was applied
|
|
|
What affects Rf?
|
-thickness of the adsorbent
-nature of the stationary phase and its degree of activation -the mobile phase -the amount of material applied |
|
|
What are the four most important plant pigments?
|
chlorophylls, carotenoids, flavonoids, and tannins
|
|
|
What are the two main types of chlorophyll present in higher plants? Which is most abundant?
|
chlorophyll a (most abundant by a 3:1 ratio)
chlorophyll b |
|
|
labile
|
capable of changing state or becoming inactive when subjected to heat or radiation.
|
|
|
xanthophylls
|
oxygen-containing products derive from carotenes
|
|
|
flavonoids
|
pigments present in leaves, fruits, and flowers.
|
|
|
anthocyanins
|
(from Greek: anthos, flower; kyanos, dark blue)
ionic flavonoids that are found coupled to sugars such as glucose |
