Chromatography Forum

Requirement of a particular monongraph is minimum 1.3 for peak to valley ratio. I am getting 1.2. How do you improve the peak to valley ratio ?


Thanks for your reply.

try increasing the % water in your mobile phase a few percent... assuming you are doing isocratic reversed phase.

Peak/valley ratio is another way of specifying resolution. You can improve that be increasing retention (as suggested by sepscientologist), by increasing efficiency (plate count), or by changing selectivity.

You need to dig one level deeper to see *why* the peak/valley ratio is too low.
- are the retention times shorter than they should be? The add more water
- are the retention times about right, but the peaks are wider than they should be? Maybe a new column, or check for things like too much tubing volume.
- are the retention times about right and the peaks are the right width, but the spacing is a bit too tight (peaks closer together than they should be). Again, maybe a new column or a new batch of mobile phase.

[quote="tom jupille"]- are the retention times about right, but the peaks are wider than they should be? Maybe a new column, or check for things like too much tubing volume.

Addendum: Check detector settings (Response time/rise time/ whatever it is called in your CDS)