Bioequivalence and Bioavailability Forum

Dear Joy,

❝ I couldn't find rules in EMEA or FDA guideline, related to Ratio area of analyte vs internal standard (IS) for LLOQ in calibration curve.

AFAIK there is none.

If you are using a stable isotope IS: you need to consider the isotopic purity of your IS (so basically, the signal you get in the channel of the analyte when injecting a pure solution of the IS). You may need to adapt the amount of IS you add if the purity is not high enough.