[firzzy87]

how can we recognize these types of elution  ... Which one was widely used in high performance liquid chromatography techniques.. can we recognize the elution by looking at the retention time also...thank u again for helping ...

[Arkcon]

Isocratic uses one eluent composition throughout the separation, gradient changes composition as it runs, usually by mixing two or more eluents.  You can't really tell by looking at the resulting chromatogram, but more complex mixtures tend to require gradient separation.

And, um, try to avoid multiposting, it's annoying.