Question

What is gradient elution and what are the advantages to using a gradient in HPLC?

Answer 1

Steady changes in the composition of the mobile phase during the chromatography technique is called gradient elution

The main moto behind carrying out gradient elution is to elute out strongly retained components of the mixture faster, but making the less/weakly retained component well resolved.

We bein with with the low composition of the organic component in the eluent thus enabling the weakly retained components to be separated first. Strongly retained components will adsorb onto the adsorbent surface on the top of the column, or will move very slowly.

When we begin to increase the amount of organic component in the eluent solvent, then strongly retained components will move much faster this time, because of the steady increase of the competition for the adsorption sites.

1. Gradient elution also increases quasi-efficiency of the column.

2. Gradient elution is ideal for certain kind of mixtures which cannot bew separated by Isocratic method because of their wise K' range

3. Low pressure gradient system have only one pump and therefore less expensive compared to high-pressure gradient system which have 2 pumps and therefore expensive. So low-pressure gradient systems are more often used.