Question

compare column, thin-layer, and gas chromatography in terms of mobile phase and stationary phase

Answer 1

CHROMATOGRAPHY DEFINATION / BASICS

Chromatography is a technique for separating and for identifying the components in a mixture . The basic principle for separation is that the components in a mixture have different tendencies to get adsorbed onto a surface or get dissolve in a solvent.

All chromatographic methods require one static part ( which is called the stationary phase) and one

moving part (called the mobile phase). The phenomena’s which can explain chromatography can be one of the following : adsorption; partition; ion exchange; or molecular exclusion

There are different types of chromatography eg paper chromatography, column chromatography ; thin layer chromatography (TLC), high performance liquid chromatography (HPLC), gas chromatography (GC), liquid chromatography (LC) , high performance liquid chromatography (HPLC) etc

COMPARISON BETWEEN DIFFERENT CHROMATOGRAPHY

Now according to question we need to compare Column chromatography , gas chromatography and thin Layer chromatography in terms of stationary and mobile phase,

Now What is stationary phase and mobile phase in general??

As explained earlier stationary phase is the static phase on which separation takes place and mobile phase is the phase carries the analyte ( Substance to be separated ) and thus helps in separation. Now talking individually about different chromatographic techniques.

Column Chromatography	Thin Layer Chromatography	Gas Chromatography
1) . Column chromatography is rarely used as an analytical technique, as TLC is. Column chromatography is primary used to separate relative large samples into pure components. Column chromatography is a preparative technique.	1) TLC is basically an analytical technique. It can be used to identify components of a mixture , monitor the progress of a reaction (by comparing the intensity of spots) and check the purity of a sample (more than one spot indicates an impure sample). Rarely is TLC used to isolate and purify compounds into discrete samples.	1) Gas chromatography (GC) is a type of chromatography which is used in analytical chemistry for separating as well as analyzing compounds that can be vaporized without decomposition.
2) Here the stationary phase is solid which can be anything like silica gel ( very commonly used) alumina , cellulose powder ( earlier used).	2) TLC is performed on a sheet of glass, aluminum foil or plastic coated with a thin layer of adsorbent which can be silica gel, alumina oxide or cellulose and it is called stationary phase.	2) The stationary phase is a microscopic layer of polymer or liquid or it can be an inert solid support, in a metal tubing called a column or it can be made of glass.
3) The mobile phase or eluent is either a pure solvent or a mixture of different solvents which usually carries the analyte and usually enters from top of column	3) When sample is applied on the plate, a solvent or solvent mixture (known as the mobile phase) is drawn up the plate via capillary action thus separating the analyte. The mobile phase must not be allowed to reach the end of the stationary phase.	3) In gas chromatography, the mobile phase is a carrier gas, usually an inert gas such as helium or an gas such as nitrogen. Helium is most commonly used carrier gas also hydrogen is used for improved separations.
4) In this type of chromatography individual components are retained by stationary phase differently while they are moving at different speeds in column with eluent they got separate. And they elute one by one from end of column and in this process eluent is collected in series of fractions.	4)In this chromatography the mixture is ‘spotted’ at the bottom of the TLC plate and allowed to dry. The plate is placed in a closed vessel containing solvent (the mobile phase) so that the liquid level is below the spot. The solvent ascends the plate by capillary action, the liquid filling the spaces between the solid particles. This technique is usually done in a closed vessel to ensure that the atmosphere is saturated with solvent vapour and that evaporation from the plate is minimised before the run is complete.	4) In gas chromatograph a flow-through narrow tube( called column), through which differ­ent constituents of sam­ple passes in a gas stream (carrier gas) at different rates depending on vari­ous chemical and physical properties and their inter­action with column filling, called the station­ary phase. As the chemicals exit the end of the col­umn, they are detected electronically.