Question

Gas Chromatography

How are compounds separated by GC? What kind of information do we get from GC/MS analysis?

Answer 1

In a gas chromatograph, a column made of glass or metal is coated inside with an inert material. Upon that inert material, a layer of liquid/polymer is applied. This layer of liquid/polymer acts as the stationary phase.

Mobile phase is generally an inert gas, mostly Helium.

When the gaseous mixture to be separated is passed through this column, the components of the mixture interact with the stationary layer, and hence they are carried at different speeds along the mobile phase. This causes the different components of the mixture to elute (come out of the column) at different intervals, hence the separation is achieved.

Using GC analysis, we can know how many different compounds are present in a mixture, that is, we get to know about the purity of the compound. Also we get to know about the retention times of the different components. This data of retetion times is extremely useful in performing analytical studies and designing separation columns using these data.