Chromatography is a separation process involving two stages, stationary and mobile phase. Mixture to be examined is adsorbed in stationary phase and mobile phase is passed into it, eventually compounds of mix have separated based on rate of adsorption and solubility. Both are physical properties. Normally, within this chromatography, a glass tube is full of adsorbent alumina or silica gel up-to one third of it is length. Then, it is saturated with selective solvent. Sometimes, column is full of slurry adsorbent + solvent. The column should have no space. Such a column is said as ‘well packed column’. In this technique, less polar compound will be eluted first. Because, less polar compound won’t be as adsorbed in polar stationary phase. Finally, more polar compound will come out.
In TLC, a plate glass/plastic is coated with a thin layer of solid adsorbent. A little drop of mixture is seen near the bottom of plate. Then, plate is set in solvent chamber in this a way that only bottom component gets dipped into solvent mobile phase. This liquid gradually rises up to TLC. In this approach, separation is measured by RF value. Separated compounds move to different space, which can be expressed by retention factor RF worth. Compound of lower polarity will have greater RF worth than more polar ones. Within this chromatography, stationary phase is water adsorbed in newspaper and mobile phase is combinations of different organic solvent and water. Any fall of organic solvent on a filter paper becomes partitioned between water and solvent. Then, this paper is dipped into variety of solvent mixtures and chromatograms are developed.
Ascending and descending, this two kinds of development generally occur. Like TLC, within this method too, separation is expressed by RF value. Compounds with higher RF value has lower polarity and vice versa. This is the most modern technique of what is chromatography. It is often utilized in analytical chemistry. In this technique, sample vaporized without decomposition is injected into pillar. The sample is transferred through this column from the flow of mobile phase. Here, mobile phase is inert carrier gases Ex- He or nitrogen. Column is coated with different stationary phases. So, essentially, elements of examined mixture are partitioned between strong stationary phase and portable gas. Each compounds elute in another time, which is called retention time. Compounds eluted at different retention period then get detected in a variety of detectors. Finally, these are listed in a recorder and chromatograms are accessed.