Bioequivalence and Bioavailability Forum

Hi Ionsource,

❝ Please let me know if this difference in the method of solution preparation is significant enough to invalidate our previously done studies?

In my opinion both methods are acceptable and GLP compliant.
Having said that, I would also like to say:
1. I understand the comments from other posters in this thread: The more pipetting that takes place the larger the risk of an error being carried forward. But om the other hand the same holds true for every step involving dilutions. And a normal standard curve or QC prep. involves "a lot" of such steps.
2. I am aware of the source of your doubt. In some cases I have witnessed inspectors or auditors being upset by the fact that analytical results are given with e.g. 4 decimals or 5 significant digits or whatever, while at the same time, if the assay developer weighs "approximately XY.Z mg" into a vial and dilutes from there to a known volume then the LLOQ cannot necessarily be generally (yes, that term was generally) specified in the same fashion and we end of up with an assay having an LLOQ of "about ABC ng/mL" etc. This is due to the fact that the lowest calibrator conc. on standard curves may differ a little. It simply seems unpalatable to some auhtorities (whether formal or self-appointed ) that the LLOQ is given approximately while results are given with higher accuracy.