Polarity has a huge affect on how attracted a chemical is to other substances. The larger the charge difference, the more polar a molecule is. You will find that as you increase the polarity of the solvent, all the components of the mixture move faster during your chromatography experiment.
Why does the solvent move up the 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.
The presence of these hydroxyl groups renders the surface of silica gel highly polar. Thus, polar functionality in the organic analyte interacts strongly with the surface of the gel particle and nonpolar functionality interact only weakly.
In most column and TLC the stationary phase has a very high polarity and the mobile phase has a lower polarity. Ferrocene is less polar then acetylferrocene. This means that ferrocene will like, or have a higher affinity to the less polar mobile phase than the more polar stationary phase.
In chemistry, silica gel is used in chromatography as a stationary phase. In this application, due to silica gel's polarity, non-polar components tend to elute before more polar ones, hence the name normal phase chromatography.
Chlorophyll is a green pigment that gives most plants their color.The reason that it is green is because it absorbs other colors of light such as red and blue, so in a way the green light is reflected out since the pigment does not absorb it.
The stronger a compound is bound to the adsorbent , the slower it moves up the TLC plate. 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).
Both chlorophylls are much more polar than β-carotene. This makes chlorophyll b slightly more polar than chlorophyll a. After we isolate the pigment mixture from the leaves in a hexane solution, we will use the difference in polarity to separate the various pigments using column chromatography.
Polar compounds will interact with the silica more strongly than non-polar ones so will come off the column, or elute, after non-polar compounds. When a sample contains compounds with similar polarity, the separation between then can be small and recovering all of your clean sample can become a challenge.
Caffeine is water soluble, so it is a polar compound. If you're looking for a more chemically accurate answer, the reason is because in the caffeine molecule, the nitrogen and oxygen are more strongly polar than the carbon, which allows them to more firmly pull the covalent electrons from the carbon counterparts.
Hexane is just hydrogens and carbons and there isn't much charge imbalance. The carbon-hydrogen bonds aren't very polarized. Because of that lack of charge imbalance, the molecule is non-polar.
Beta carotene is carried the furthest because it is highly soluble in the solvent and because it forms no hydrogen bonds with the chromatography paper fibers. Chlorophylls are bound more tightly to the paper than the other two, so they travel the shortest distance.
Methylene chloride or dichloromethane is moderately polar. Any small molecule cannot be polar or non polar at the same time * polarity is a range. Chlorine being more electronegative than hydrogen causes the dichloromethane molecule to be slightly more negative on the side of the chlorine atoms.
Alcohols are less polar than water. This means that alcohols are better solvents of organic molecules. The isopropyl group is large and nonpolar, so isopropyl alcohol is less polar than methanol and ethanol. It is a component of nail polish removers as organic compounds in nail polish become soluble.
In paper chromatography, for example, you dissolve the components of a mixture in a solvent. As the solution moves along the paper, the various constituents travel at different speeds. They separate into different spots.
In the classic case of the black ink being separated into its component colors using paper chromatography, the paper in this case is the stationary phase and the liquid solvent that the paper is dipped into is the mobile phase. Purpose of chromatography is to separate homogeneous mixture.
The farther a compound travelled, the larger it's Rf value. Logically, you can conclude that if a compound A travels farther than compound B in a polar solvent, then it is more polar than solvent B. So basically, the compound that is more "like" the solvent will have the larger Rf value.
Chromatography is used to separate mixtures of substances into their components. They all have a stationary phase (a solid, or a liquid supported on a solid) and a mobile phase (a liquid or a gas). The mobile phase flows through the stationary phase and carries the components of the mixture with it.
Paper chromatography is a useful technique in the separation and identification of different plant pigments. The solvent carries the dissolved pigments as it moves up the paper. The pigments are carried along at different rates because they are not equally soluble.
The silica gel (or the alumina) is the stationary phase. The stationary phase for thin layer chromatography also often contains a substance which fluoresces in UV light - for reasons you will see later. The mobile phase is a suitable liquid solvent or mixture of solvents.
Paper chromatography. Paper chromatography is an analytical method used to separate colored chemicals or substances. It is primarily used as a teaching tool, having been replaced by other chromatography methods, such as thin-layer chromatography.
Gas Chromatography is used in airports to detect bombs and is used is forensics in many different ways. It is used to analyze fibers on a persons body and also analyze blood found at a crime scene. In gas chromatography helium is used to move a gaseous mixture through a column of absorbent material.