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Hi
We had internally discussed whether it is acceptable to use a
reinjection of the calibration line at the end of a sample batch. QC
samples are scattered over the whole batch. The decision which
calibration curve is used for evaluation is made from the results of the
QC samples.
As an explanation: You sometimes have LC-MS methods which show some
drift over a run, especially if no good internal standard is available.
At start of the run it might not be really stable, so the second
injection of the calibration line would give much better results. In
other cases at the end of the run some changes might occur.
Is anybody else using such an attempt and do you think authorities (FDA)
would accept this? I could not find a guideline covering this.
Many thanks in advance
Michael
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Dear Michael
The recent AAPS&FDA discussions suggested to use one set of
calibration standards in the front another set in the end of the
sequence, construct a calibration curve by using these two sets
(include both front and back set) which greatly nullifies analyte
response variation with time.
I hope it would help you a lot.
Devender Reddy Ajjala
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Dear Michael,
you may also try to scatter the calibration curve standards
throughout the batch just as your QC samples. This will help your
cause in a much better way. And it is very well accepted by FDA as well.
Regards,
Noel Gomes,
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