Bioequivalence and Bioavailability Forum

❝ Could it be a possibility that the absence of one APIs may affect the final concentration of other APIs (regarding sample preparation and peak response)?

Impossible. Regardless whether you use LLE or SPE each analyte follows the law of mass action (driven by pH, lipophilicity) independent from other analytes. The amount of the “target phase” (organic solvent, RP- or exchange resin) is 6 to 12 orders of magnitude higher than the one of the analyte. Hence, the presence / absence of other analyte(s) in a similar – low – amount is simply irrelevant. It can never change the equilibrium constant.

Unless you have an insufficient separation, no. Only if peaks overlap, in MS ion-suppression/enhancement by one analyte could influence the response of the other.

Can be problematic if you have a substantial degree of cross-reactivity.