I am a 7th grade student at a private school in Cary, North Carolina. I am doing a project on Chromatography for science class. If anyone can answer my question, could you please e-mail me at Piggypoo@hotmail.com!
Thank you

Hi Emma,

The direct translation for chromatography is "colored writing". I am not sure if it is Greek or Latin. Chromatography today refers to the science of separation.

In 1906, Mikhail Tswett (1872-1919) used a glass column packed with calcium carbonate (solid and stationary) and petroleum ether (liquid and mobile) to separate components of chlorophyll. By having mixtures interact between a stationary phase (calcium carbonate) and a mobile phase (petroleum ether), it is possible to separate mixtures into individual chemicals to be analyzed and quantified. Some chemicals like mobile phase better than stationary phase and travel through the column more quickly. Likewise, chemicals that like stationary phase more than mobile phase remain on the column longer until conditions between the phases change and the chemical becomes more attracted to the mobile phase.

Today, there are three main modes of chromatography - gas, supercritical fluid (a chemical that is in equilibrium between gas and liquid), and liquid. Modern equipment can simplify these separations and perform them in minutes and cost as little as $2,000 to as high as $50,000.

Hope this helps,

Steve

i am doing a project for school and i was wondering if you could plese help me out with these questions.

1.How does chromatography work? as a solvent, polarity, absorbtion
2. What is an Rf value?
3. Why do leaves change color in the fall?
4. What is the structure(chemical) and name of the pigments in leaves?
Thank you very much

Hi Danica,
Maybe I'll be able to help you, at least partially, I hope.

Ad. 1. In general, the chromatography (the word comes from greek "chroma" [colour] and "grapha" [paint]) is based upon system containing
stationary phase particles and the mobile phase substance. Stationary phase, for instance 5 micrometers big silica round-shape particles, may be
packed in a column (capillary, or bigger like 4 mm ID) or spread on a plate. Now we must apply the mobile phase. If the silica is packed in a column
we can PUMP mobile phase through the packed column. In this case we may have two kinds of chromatography: I) Gas chromatography (GC)
where the gas is our substance of mobile phase (can be pure nitrogen, argon or just air); II) Liquid chromatography (LC) where our mobile phase is
liquid (water, methanol, hexane, etc.).
When your stationary phase is on the plate then you can only use liquid mobile phase - this is Thin Layer Chromatography (TLC), but the
retention mechanism is similar to LC.

Now, in the GC we mainly deal with the retention of your analysed chemical (injected onto the column along with the constantly pumped mobile
phase) which is based upon the stationary phase-analyte interactions. If the stationary phase is silica the main driving force will be adsorption
(NOT absorption!), caused by polar -OH groups of silica. However, if the silica is derivatized with some hydrophobic organic species then the
other interactions (so-called non-polar dispersive attraction) will appear. Gas is assumed to be inert medium (no considerable interactions).
In LC we got the same as above but additionally, there is a liquid mobile phase. The liquid mobile phase interacts STRONGLY with both, solute and
stationary phase, therefore the resulting retention of your solute is a kind of "compromise" between all interactions among all components of
chromatogtraphic system. The interactions may be ion-ion, ion-dipole, dipole-dipole or dispersion (non-polar), depends on the type of stationary
phase, mobile phase and your solute (=analyte).

Ad. 2. Rf value comes from TLC and signify the distance of retention of your solute, that is how long it has been traveling on your plate (with
spreaded stationary phase and flowing mobile phase through) from the start point to the end point, and this is with respect to the velocity of travel of your mobile phase. Usually your substance travels much slower.

Ad. 3. Because magnesium atoms in chlorophyll (green dye of leaves, which produces oxygen) become oxidized when the autumn temperature goes
down and the chlorophyll transforms into the red chromophyll, therefore.
Ad. 4. Chemical structure is very complicated, you may find a picture at:
http://www.ch.ic.ac.uk/local/projects/steer/

Cheers,
Maciej

chromatograpy of photosynthetic pigments
can anyone help? I am determining relative amounts of chlorophyll a,b using beer-lambert law .I need to compare my ratios to published ratios. Why would ratios differ? Where can i find this information? Also,why does carotene move more quickly? Any help would be greatly appreciated. My write up is due in 3 days!!! regards angela www.mrigby4432@aol.com