Basically,
you can use any solvent
. The important thing is leave to dry the spots in the plate very well. In the case of ethyl acetate it is fast and in methanol it can take a bit more time. If you use a high boiling point solvent (e.g. DMSO or DMF), you have to dry them several minutes in a high vacuum chamber.
What factors affect TLC?
Retention factor values in thin layer chromatography are affected by
the absorbent, the solvent, the chromatography plate itself, application technique and the temperature of the solvent and plate
.
How does the solvent affect chromatography?
Chromatography is a technique used to separate the components of a mixture.
Different solvents will dissolve different substances
. A polar solvent (water) will dissolve polar substances (water soluble ink in the video below). A non-polar solvent will dissolve non-polar substances.
How does solvent affect Rf value?
The eluting power of solvents
increases with polarity
. Non-polar compounds move up the plate most rapidly (higher Rf value), whereas polar substances travel up the TLC plate slowly or not at all (lower Rf value).
Why are polar solvents better for TLC?
The eluting power of solvents increases with polarity
. Therefore, low polarity compounds can be eluted with low polarity solvents, while higher polarity compounds require solvents of higher polarity. The stronger a compound is bound to the adsorbent , the slower it moves up the TLC plate.
How does TLC choose solvent system?
The choice of solvent or a mixture of solvents used in TLC is solely guided by two important factors : (a) the nature of the constituent to be separated i.e., whether it is polar or non-polar ; and (b) the nature of the process involved i.e., whether it is a case of ‘adsorption’ or ‘partition chromatography’.
When should a mixed solvent system be used for TLC?
Use a mixed solvent system
when no single solvent gives the desired separation
. Mixed solvent systems can be particularly effective for separating compounds having similar physical properties. The order of elution for TLC is about the same as for column chromatography.
What solvent is best for TLC?
- Polar compounds: 100% EtOAc or 5% MeOH/dichloromethane.
- Normal compounds: 10-50% EtOAc/Hexane.
- Nonpolar compounds: 5% EtOAc/hexane, 5% ether/hexane, 100% hexane.
What are 3 factors that can affect Rf values in TLC?
Frequently Asked Questions on Rf Values
Retention factor values in thin layer chromatography are affected by
the absorbent, the solvent, the chromatography plate itself, application technique and the temperature of the solvent and plate
.
Why must the baseline be above the solvent level in the TLC chamber?
The start line above the solvent level
allows the solvent to move past the start line, carrying the dissolved samples along with it
.
Which are more soluble in the chromatography solvent xanthophylls or chlorophyll A?
Which are more soluble in the chromatography solvent, xanthophylls or chlorophyll a? Based on the Rf values,
xanthophylls are more soluble in the chromatography solvent
.
How does solubility affect TLC chromatography?
If the compound is soluble in the solvent,
it will travel further up the TLC plate
.
How well the compound likes the stationary phase
. If the compound likes the stationary phase, it will stick to it, which will cause it to not move very far on the chromatogram.
Does solubility affect chromatography?
1 Answer.
Solubility does not affect chromatography
; differences in intermolecular forces affect chromatography.
Why does the solvent travels up the chromatography paper?
Non-polar molecules in the mixture that you are trying to separate will have little attraction for the water molecules attached to the cellulose, and so will spend most of their time dissolved in the moving solvent. Molecules like this will therefore travel a long way up the paper carried by the solvent.
Does changing the solvent change the Rf value?
absolutely ; this due to different in interaction between the sample and mobile phase
. also we have the similar things with the stationary phase . so you can see different Rf of the same molecule in different solvent ratio.
Does increasing the solvent polarity increase or decrease the Rf value of polar compounds What effect does it have on the Rf value of nonpolar compounds?
Rf values increase
with increasing solvent polarity as substance are more attracted to the solvent and therefore move with it.
Should Rf values increase or decrease upon increasing eluting solvent polarity in TLC?
Since polar molecules attract other polar molecules, the aspirin molecules will tend to bind to the silica and not move up the TLC plate in a nonpolar eluent, resulting in a low Rf value.
When the polarity of the eluent is increased, its ability to attract polar molecules is increased
.
Why do more polar solvents elute faster?
A polar solvent will compete well with molecules and will occupy sites on the stationary phase
. This will force compounds into the mobile phase, and result in faster elution/increased travel distance.
What pulls the solvent mobile phase up the TLC plate stationary phase )?
After the sample has been applied on the plate, a solvent or solvent mixture (known as the mobile phase) is drawn up the plate via
capillary action
. Because different analytes ascend the TLC plate at different rates, separation is achieved. The mobile phase has different properties from the stationary phase.
What is the result of applying too much sample to the TLC plate?
If too much of a compound is applied to a TLC plate (or its too concentrated),
the dot will streak across the plate or it can run into neighboring
…
What is the ideal Rf range when choosing a solvent for column chromatography?
A solvent system that gives an R
f
between 0.25 and 0.35
is recommended as it gives the sample time to equilibrate on the column and thereby be fully resolved into all its component parts.
What is mixed solvent system in TLC?
The mixed solvent system
served as a solvation and reaction medium for efficiently producing reliable FAB mass spectra and for the partial displacement of the ligands for ease in their identification
.
How do you choose a solvent for column chromatography?
The solvent system which gives maximum separation of the spots
will be better solvent for column chromatography. Usually volatile solvents are better than non-volatile solvents .
When would you use mixed solvents for recrystallisation of a compound?
When no single solvent can be found that meets all of the criteria for crystallization
, it may be possible to use a mixed solvent. A pair of solvents is chosen: one in which the compound is soluble (called the “soluble solvent”), and one in which the compound is insoluble (called the “insoluble solvent”).
