Does gradient improves resolution?

[push]

Does gradient improves resolution of chromatographic peaks?

[tom jupille]

In general, no (there are a few exceptions, but they are very few). The major purpose of a gradient is to accommodate a range of retention too great to fit into a single isocratic run.

[Consumer Products Guy]

The major purpose of a gradient is to accommodate a range of retention too great to fit into a single isocratic run.

I'm not going to disagree with Tom. I was going to post that we use gradient primarily in two instances:

(1) two or more peaks of interest have significantly differeing polarity and we'd like to do in a single injection (this aligns with what Tom posted)

(2) when we want to clean extraneous components/peaks off the column to determine trace level components in the subsequent injections (a clean up gradient)

[tom jupille]

You're right, but I'd put #2 under the heading of "collateral benefits". On reflection, I'd have to add the similar situation of sharpening up low-level late-eluting peaks. Either way, it's not a case of improving resolution.