Difference Between Isocratic and Gradient Elution

Difference Between Isocratic and Gradient Elution in High Performance chromatography (HPLC).

The major difference between gradient elution & isocratic elution is that isocratic elution refers to maintaining a constant concentration in the mobile phase, whereas gradient elution refers to maintaining a variable concentration in the mobile phase.
In chromatography, the words isocratic and gradient elution are employed. We utilise a stationary phase, which is a non-moving substance, and a mobile phase, which is a moving substance, during a chromatographic run.
The characteristics of the mobile phase are described by isocratic and gradient elution.

In chromatography, isocratic elution denotes to when the mobile phase remains constant in concentration. Throughout the chromatographic process, the mobile phase concentration remains constant.
The peak width increases linearly with retention time in the chromatogram throughout this process. The late-eluting peaks for late elution, however, become relatively flat and broad as a result of this. As a result, these broad peaks become difficult to be to identify as peaks.
Furthermore, the selectivity of isocratic elution is unaffected by column diameters. This indicates that changes in column dimensions have no effect on selectivity.
The length and diameter of the column are taken into account here. As a result, the peaks elute in the same sequence order.

What is Gradient Elution?

Gradient elution is a word used in chromatography to describe when the mobile phase concentration varies. In other words, the mobile phase concentration does not have to be constant.
In HPLC, for example, a common separation procedure starts with 10% methanol and progressively increases to 90% by gradually increasing the concentration.
There are two solvents in the mobile phase: a weak solvent and a strong solvent. The solute elutes slowly in a weak solvent, whereas the solute elutes quickly in a strong solvent.
In reverse phase chromatography, the weak solvent is water, while the strong solvent is an organic solvent.