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The majority of compounds adsorb iodine and become visible if exposed to iodine vapor. Although reaction may take place with some unsaturated compounds, for the vast majority of compounds, the iodine appears to be physically bound to the material and does not chemically react. The after carrying out the elution process the plate is dried and placed in an enclosure containing iodine crystals and is preferably heated to about 50oC. Brown spots appear where the solutes are situated. When the plate is removed from the enclosure, the spots rapidly disappear and so this detection technique appears to be essentially non-destructive.
This detection procedure can be improved by first exposing the plate to a very high concentration of iodine vapor, the plate is the removed and allowed to stand for a few minutes to allow the excess iodine to evaporate. The plate is then sprayed with a 1% starch solution. As a result the solute bands appear as blue spots on the plate. These methods will detect most organic substances and in particular unsaturated compounds.
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What will be the result of applying too much compound to a TLC plate?
Applying too much compound to the TLC plate makes it difficult for a good separation to occur. Instead, a large blot of solution tends to appear in the TLC. "It is extremely important that the spots be as small as possible and that they be applied using a 1% solution of the compounds being separated
Is ethyl acetate a good solvent for using TLC plates?
Ethyl acetate is generally a good solvent for TLC. It is more polar than hexanes, but less so than acetone, alcohols, acids, and water. If you are doing a reaction for the first time and have no idea what solvent system to use for TLC, varying ratios of hexanes:ethyl acetate is always a good starting point (try 3:1, 2:1, 1:1, 1:2. 1:3, etc).
What are some different methods for separating the parts of a mixture?
It really depends what the mixture consists of. You would not use the same method to separate sand from gravel as you would to separate salt water from pure water.Some common separation methods include:Filtration: works best for solids suspended in a liquid (to separate sandy water into dry sand and pure water for example) or for two solids with very different particle sizes (to separate a mixture of sand and gravel).Distillation: works to separate liquids that have different boiling points. This method is used to separate alcohol from water (to make hard liquor) and the essentially the same method is used to take oil from the ground and turn it into petroleum products such as gasoline. Chromatography: used to separate mixtures of liquids based on polarity. Many different types exist, including thin layer chromatography (TLC), gas chromatography (GC), and column chromatography. Extraction:used to separate a mixture of solids based on their solubilities in organic and inorganic phases. Differences in pH can also be used to separate different solids by selectively ionizing one compound, causing it to dissolve more readily in inorganic solution.See the Related Questions to the left for more information.
Why iodine is used in thin layer chromatography?
The staining of a TLC plate with iodine vapor is among the oldest methods for the visualization of organic compounds. It is based upon the observation that iodine has a high affinity for both unsaturated and aromatic compounds. Preparation: A chamber may be assembled as follows: To 100 mL wide mouth jar (with cap) is added a piece of filter paper and few crystals of iodine. Iodine has a high vapor pressure for a solid and the chamber will rapidly become saturated with iodine vapor. Insert your TLC plate and allow it to remain within the chamber until it develops a light brown color over the entire plate. Commonly, if your compound has an affinity for iodine, it will appear as a dark brown spot on a lighter brown background. Carefully remove the TLC plate at this point and gently circle the spots with a dull pencil. The iodine will not remain on the TLC plate for long periods of time so circling these spots is necessary if one wishes to refer to these TLC's at a later date.
What are the Spray reagents for visualize colerless compound in TLC?
Iodine vapours can be used as spray reagent in TLC
When preparing to develop a TLC plate what is the appropriate spatial relationship between the level of solvent in the developing chamber and the spots on your TLC plate?
The spots on the TLC plate should be placed about a cm from the bottom of the plate. Then solvent should then fall about half-way between these spots and the bottom of the beaker.
How do you check TLC for thio barbituric acid it wont soluble in any solvent?
Barbituric acid looks like its very polar... it should be soluble in water and acetone, at least.Visualizing it on a TLC plate is problematic because the compound is not aromatic and thus does not absorb UV. The easiest way to visualize non-UV absorbing compounds on a TLC plate is using an iodine development chamber. In a jar, mix some powdered iodine (I2) crystals* and dry silica gel. Throw in the TLC plate (after running in the appropriate solvent system), shake it a bit, and use forceps to fish it out. The iodine should oxidize the compound on the plate and it should appear as a brown dot. The iodine development chamber can be used pretty much indefinitely. Hope this helps!Do all steps in the fume hood... pure iodine is toxic.
How Chromatography can be used for non colored solution?
Many organic compounds are aromatic and thus absorb ultraviolet light. Simply shine UV over your TLC plate and observe the spots. If the compound isn't UV absorbing but has a double bond, a solution of KMnO4 can be used to visibly stain the compound on the TLC plate.
Why is it important to keep the spots applied to TLC slides for chromatography as small as possible?
The components may not separate properly, because the solvent will overload
What will be the result of applying too much compound to a TLC plate?
Applying too much compound to the TLC plate makes it difficult for a good separation to occur. Instead, a large blot of solution tends to appear in the TLC. "It is extremely important that the spots be as small as possible and that they be applied using a 1% solution of the compounds being separated
What problem will ensue if the level of developing liquid is higher than the applied spot in a TLC analysis?
If the spots are submerged in the solvent, they are washed off the plate and lost.
What is dimethylaminobenzaldihyde used for?
it is used for detecting Urobilinogen in Urine, in TLC plates, and for hydrazine indicator.
Why KMnO4 used in TLC?
because it can make the point shown in your plate
Can you grow a apple tree in southeast Louisiana if so what kind?
yes you can....but it needs alot of tlc in northeast they grow but they have alot of spots and problems ....humidity pears grow easily
Was Beyonce ever in TLC?
No, Beyonce was never apart of the group TLC. She was in Destiny's child but never TLC
