Back to the Top
Dear All,
Recently i got an assay validated with labeled internal standard and proceeded to study sample analysis and Now many of my samples are qualifying in Internal standard variation,even though the concentration of such samples is well within the profile.(repeated values give me same concentration)
what i want to know is"can we define any particular acceptance for internal response? or any validation experiment support the fact?What is the reason for this type of variation?This is my second such experience in both the methods i was using labeled Internal standard and in both cases variation was there?
bioanalytical method with MS as detector.
Kindly respond
jacob
Back to the Top
The following message was posted to: PharmPK
It was caused by matrix effect. If you are really concerned about this. You may want either modify your extraction method or LC method, or even both. There is a paper published by Rick King on how to evaluate this kind of matrix effect.
Hope this help.
Back to the Top
Dear jacob,
When you developed and validated the method using labeled IS, with your blank plasma samples you did not get such type of IS variation. but as you do the real study samples due to presence of formulation ingeradients and subjects variability, you may get IS variation in the subjects and this effect may be continued even in the interspersed QC's. It is observed change in mobile phase or change in column will change the RT of your analyte and co-eluting substances. if it does not work, you hv to redevelop extraction method.
ashish saxena
|
Want to post a follow-up message on this topic?
If this link does not work with your browser send a follow-up message to PharmPK@boomer.org with "Internal standard variation" as the subject | Support PharmPK by using the |
Copyright 1995-2011 David W. A. Bourne (david@boomer.org)