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- Posts: 7
- Joined: Fri Jul 12, 2013 8:32 am
I am doing a validation of a HPLC based bioanalytical method.
My problem is: if I am using self prepared quality controll samples (stock solution is the same as for the calibration) I always obtain good results. Every time I am using external quality control samples I am also getting good results for high concentration levels (about 95%) but not for low (only 75%) ...
I have already tried to do weighted regression analysis with 1/x as a weighting factor but this makes the results even worse (only for the external low quality control samples).
Does anyone can help me? What is the reason for that? I don't have the foggiest idea
Thanks!