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Dear All,
When in a bioanalytical assay is justified a not use of internal
standard? I am talking about a bioequivalence assay of fluconazole
(HPLC-UV) and a use of internal standard was not possible because of
low recovery of it. Fluconazole had a good recovery (over 90%).
How justify a not use of internal standard?
Regards,
Daniel
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The following message was posted to: PharmPK
Only if there is little opportunity for volume changes (e.g. with
extraction) to introduce variability to the assay.
The absolute recovery of the IS is not the major issue, provided the
overall assay imprecision/inaccuracy is satisfactory (also applies to
the analyte provided the LOQ is satisfactory too).
Cheers,
BC
Bruce CHARLES, PhD
Associate Professor and Director,
Australian Centre for Paediatric Pharmacokinetics
School of Pharmacy
The University of Queensland, 4072 Australia
[University Provider Number: 00025B]
TEL: +61 7 336 53194
FAX: +61 7 336 51688
B.Charles.-at-.pharmacy.uq.edu.au
http://www.uq.edu.au/pharmacy/brucecharles/charles.html
http://www.mater.org.au/pharm/departments/accp.asp
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Dear Daniel,
Under the circumstance you mentioned, your IS might not be a problem. The
recovery of a IS is not too important, however, its recovery rate should be
consistent. As Dr. Charles has mentioned, you could run 1) intraday and
interday variation studies 2) accuracy study to validate your assay. If the
CV of the intraday and interday variation are small (< 5% or 10%) and
accuracy is accetable (100 +/- 5 or 10%), even your IS has low recovery,
your assay is still reliable.
Good lucks
Haishu Lin, PhD
Scientist
ProStrakan
102 Route de Noisy
Romainville 93230
France
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