Introduction:
Partition column chromatography is a type of column chromatography in which the separation of compounds is based on the partitioning between two immiscible liquids: a stationary liquid phase coated on the surface of an inert solid support and a mobile liquid phase.
The components in the mixture partition themselves between these two phases, and this partitioning difference leads to separation.
Methodology:
Partition column chromatography is based on a partitioning equilibrium between two liquid phases.
One liquid phase is held stationary by adsorption on the surface of an inert solid support, while the other liquid phase acts as the mobile phase and moves through the column.
Here’s a step-by-step breakdown of the process:
1. Preparation of the Column:
A column (typically glass) is packed with an inert solid support that has been soaked or coated with one of the immiscible liquid phases, which becomes the stationary phase.
Common supports include diatomaceous earth, Celite, or silica, while the stationary liquid might be water, an oil, or another suitable liquid.
2. Sample Loading:
The sample is dissolved in the mobile phase or a compatible solvent and then introduced onto the top of the column.
3. Elution:
The mobile phase, which is immiscible with the stationary phase, is poured or pumped onto the column.
Compounds in the sample distribute themselves between the two liquid phases based on their partition coefficients.
Those that prefer the mobile phase will move faster through the column and elute earlier, while those that have higher affinity for the stationary phase will move slower and elute later.
4. Detection & Collection:
As in adsorption chromatography, fractions are collected at the bottom in test tubes or vials.
Detection of the eluted compounds might be visual (if compounds are colored) or, in a more sophisticated setup, by using detectors like UV-Vis or refractive index detectors.
5. Analysis:
Fractions are analyzed to determine their constituents.
Techniques like TLC, GC, or HPLC can be employed to analyze these fractions.
Components:
Stationary Phase: Typically, an inert solid support like diatomaceous earth (e.g., Celite) is coated with a liquid phase (like a water-soluble polymer or an oil).
Mobile Phase: An immiscible liquid, often an organic solvent, which competes for the sample compounds, leading to partitioning.