Chromatography Forum

I have a method with several impurities, process and degradation products.
We can resolve the impurities but the resolution is not getting any better than 1. Infact, some of them are less than 1.

I use Empower Apex track integration algorithm. All my peaks are integrated based on this algorithm.

Is there a minimum resolution that I need to achieve, inorder to obtain an accurate peak integration.

A question towards clarity of your issue - are you worried about the actual ability to integrate, or are you worried about correctly quantifying the amount of substance you are integrating? Optimizing integration parameters is one thing; optimizing your separation is another.

If it's the latter, are you working under USP guidelines/regulations? If so, I found two different numbers, either 1.5 or 2. I think it depends on what the method-specific system suitability parameters are.

http://www.usp.org/pdf/EN/meetings/asMe ... meters.pdf

>1.5 for the critical pair


http://www.fda.gov/downloads/Drugs/Guid ... 134409.pdf

Recommendations:
R, of > 2 between the peak of interest and the closest potential interfering peak (impurity, excipient, degradation product, internal standard, etc.) is desirable.


But, I don't work in the pharma industry, so those who have more knowledge than me will know better.

Unfortunately, there is no hard-and-fast number. "Baseline" resolution of 1.5 was originally defined that way as the resolution at which you have just less than 1% overlap between two equal-sized, Gaussian peaks. The FDA suggests that resolution should be greater than 2. Where there is a big disparity in peak sizes or serious tailing, even greater resolution may be required. Perhaps the best statement comes from Dyson's book on integration:

“. . . errors arising from peak overlap are introduced by the algorithms of perpendicular and tangent separation and cannot be eliminated by anything but better chromatography. Integrators are able to generate a highly precise and totally inaccurate set of results for all the foregoing examples.â€

We target resolution of 2 or better with our in-house validated assays, but my memory thinks our SOP may list 1.5 minimum. Now, we use new or virtually-new columns for our validation work, and three different lots of packings. Methinks (personal opinion) is that 2 is the guideline desired, full well knowing that over time the resolution will not improve, likely start getting worse. 1.5 resolution looks like baseline, and even without baseline resolution today's data systems can do a great job.

So I'd go with Tom's opinion: if it works for you.....

Hi and happy holidays

as an addition to Toms post, I would also consider what stage in development you are. Say for instance that you are doing drug development before commercial stage, you might be on "good enough resolution", as your improve "your" product the number of likely impurities hopefully will decrease and the situation will change to the better. In worst case you might end up with 2 different methods to accurately determine all relevant "peaks"