Chromatography Forum

Hi! all!

Kindly clarify my doubt wrt the reporting of impurities.

Say

I am having the following two known imps ..

Imp - 1 = 0.008 %w/w -----> LOQ = 0.010 %w/w
Imp - 2 = 0.015 % w/w ------> LOQ = 0.010%w/w

If my Total imp = imp - 1 + imp - 2

Then what shld i report i.e 0.023%w/w (by including the below the LOQ values of imp -1) or 0.015%w/w (excluding the Below the LOQ value of imp -1 )

is there any guidelines or articles available related to reporting such results?

If available pl share the reference!

Thanx in advance.

Actually, I don't think I would use either of those options. According to the ICH guidelines on impurities, the total impurities should be the total of all impurity results above the ICH reporting limit (not the quantitation limits).

Hope this helps. Adam

This is something that arises in environmental testing constantly.

Limit of Quantitation (LOQ) is just that, a limit. Your imp-1 may be detectable, but it is not reliably quantifiable. Thus, you would not want to report a number for it, or base any reported number on it. However, you may want to report or comment on the fact that it was detected below the LOQ.

For example, a common test of drinking water is for trihalomethanes. These are tested individually, chromatographically, and then the total is reported. That total will only be based upon detections above the LOQ, and that is the value that is used for compliance purposes. However, we will note additional detections less than the LOQ, but higher than the limit of detection (LOD).

As you may imagine, some environmental testing clients are interested in those below LOQ values, and will try to track them, while others couldn't care less since they are not compliance reportable.

ravenwork

In total impurities, the impurities >LOQ should be included. But while reporting individual values you may report either Below LOQ or report the actual value and mention the LOQ value of that particular impurity. I prefer to report the actual value and include a statement "Below LOQ. Not included in total impurities". The signficance of reporting the actual value is in stability. If the peak increases with time, you can see the trend.