I'm working in a pharmaceutical company in Eastern Europe and we are at beginning of developing HPLC methods for our products. For one of them we have to establish the maximum level of the related compunds (impurities from the synthetis and degradation compounds). As long this particular product can not be found in any pharmacopoeia (USP,BP,EU.Ph,...), how can we set this level? Are there any general rules for this kind of problem? I'll be grateful for any suggestion.

I believe that in most cases, you have to quantitate any peak that consitutes more than 0.1% (area % at the wavelength of maximum absorbance of the parent) and identify any peak that constitutes more than 0.5%. I also believe that lower limits may be required if any of the impurities are known to be highly active / toxic / carcinogenic.

Check www.ich.org and www.fda.gov and do searches there.