limit solution

[olivia]

Hi, what is the purpose of the limit solution in stability assays (0.1% of standard concentration)
Is it just to see the lowest amount detected
Thanks liv

[Dan]

Two reasons for having a limit solution:

1. The limit solution is used to determine if the level of an analyte is below a given specification limit. In a chromatogram, this is usually evaluated by simply comparing peak areas (or converting the peak areas to a %w/w value using calibration).

2. To check the detection sensitivity of the system as part of the system suitability test (SST) evaluation. It is, essentially, a check of the limit of quantitation for the system that is used for methods that are for impurity analysis. You can find this in the chromatography chapter of the EP. The USP was going to add to add this requirement but postponed it due to concerns that older methods cannot meet the criteria. However, the USP did suggest tha all new methods have such a SST requirement. Here is a link for the USP:

http://www.usp.org/USPNF/notices/postpo ... er621.html

Which is the correct reason? That depends on your method. What does the method state?

Regards,
Dan