Bioequivalence and Bioavailability Forum

Dear BE/BA Forum,

I have a question regarding injecting the pre-conditioning samples (or stabilizing, equilibration samples) and cleaning of column in between a run.


1) For most method, we injected some LCMS equilibration samples before starting system suitibility. These samples are pooled CC/QC from a previous batch. We also set acceptance criteria for LCMS equilibration. For example, method SOP will state how many equilibration samples should be injected and what should be the %RSD of the last three samples area ratio. My question is can we also continue to inject these equilibration samples after the system suitability, until we are ready to load actual samples? For example, I injected 10 equilibration samples, the system suitibility, then for another 1 hour, those equilibration samples is continued before starting the calibration curve.

2) Is it alright to switch method to column cleaning, then equilibration samples, and then continue with the rest of samples? For example, samples from two subject were extracted together along with a calibration curve and QC. To analyze this batch, calibration curve, some QC and first subject were injected, then method is switched to column cleaning for 20 min (high %organic), then switch to normal method and start with equilibrating and stabilizing samples (let's say 10 injections) then followed by the second subject samples along with the rest QC.

Thanks a lot for any comment/opinion,
Ladi