Bioequivalence and Bioavailability Forum

Dear group members,

I got consistant response of internal standard in Method Validation.But during study sample analysis, I got variation more than 40% of mean response of calibration curve standards. And I was observed that in some samples ISTD response exactly double than that of preceeding and succeeding samples, even after taking care during sample processing.

Response of ISTD in CC's and QC's almost same, but in subject samples response was differed.


1.what might be the reason for internal standard variation ?
2.why sudden response change will come?
3.Is there any regulatory guideline suggesting the acceptance criteria for internal standard variation?.

Thanks and Regards,
chari.