Chromatography Forum

Dear all,

please any one clarify regarding LOQ limit of impurity

one of the impurity having LOQ more than reporting threshold and 50% below of its specification level,
is it acceptable ?

pls clarify and provide guideline evidence.

thanks and regards
Kumar

No guidance required. The LOQ must be below the reporting level (otherwise, how will you know whether or not to report the impurity).

I agree with Tom. I had a unique situation where the known impuritiy-L elute in a noisy region (early part) of the chromatogram where its LOQ was higher (e.g. 0.20%) than the "overall" method's LOQ (e.g. 0.1%).....gradient method. No unknown impurities (in stressed and stability samples) elute in this region where the Impurity-L elutes. I believe it's okay to provide a rationale for accepting a method with this unique situation. If the impurities are all known and have specifications, would it be acceptable to have a higher LOQ (e.g. 0.20%) than the ICH reporting limit (e.g. 0.10%)......spec (e.g. 0.4%)? We should strive to develop better methods .

Thank you TOM and GTMA .

gtma, please provide guideline evidence for known impurity LOQ more than reporting threshold is acceptable
(below 50% of its specification limit)

regards
kumar

Sorry, I don't have any guideline evidence. It's seem logical that for known impurities with a specification, it makes sense to validate from 50% to 150% of specification in some cases. For example, if the known impurity specification is 1.0% and the ICH reporting limit is 0.10%, should I validate from LOQ to 150% of spec or 50% to 150%? I think it's acceptable to validate from 50% to 150% of spec if that known impurity is not part of the total impurities. However, if the known impurity is included in the total impurities or used as a surrogate for unknown impurities, then I would recommend validating from the LOQ/ICH reporting to 150% of spec. Any thoughts?