Chromatography Forum

The last few revised EP monographs I've had to deal with all seem to have Peak-to-Valley ratios newly added as part of the system suitability criteria. Is this calculation the latest and greatest in sys suit, or is it a european thing? And, can we use some other parameter that is more common in the US?

Next, comes how to calculate the ratio. The main data collection program for us is TotalChrom. There is a "Height" parameter in the Sys suit subscreen (under Apps). Is this where we need to go, and where do we go from there?

Thanks for any help!

I haven't got the latest EP handy, but I hope that the peak to valley ratio is not the "latest and greatest ", as it's only supposed to be used as an additional system suitability test for related substances only when the chromatography is poor.

Specifically, the test is applied when baseline separation between two peaks is not reached. The details, along with an example, are in Section 2.2.46 "Chromatographic Separation Techniques ", subsection "Separation Data ". Improve the resolution to >1.5 and the p/v ratio becomes irrelevant.

The example shows how you divide the height of the minor peak (measured from the extrapolated baseline of the major peak ), by the height of the valley ( between the two peaks ) measured down to the same extrapolated major peak baseline.

I've no idea how to calculate it with your software, and it's proably best to ask the software vendor.

Please keep having fun,

Bruce Hamilton

You may well have to grab heights from an exported RAX file to do that calculation (like when you do step gradient or linear gradient responses for calibration, if you've done them that way).

Thanks for the info. sometimes the EP monographs give me a migraine. I'm not sure how to write that into our Quality release methods. That's way too involved. I guess we will have to petition.

Or use a ruler...?
I'd check w/ PE - there may be a simpler way to do it.