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Dear All,
I am on a project of Analysis of tacrolimus in whole blood. during
method development i observed that the recovery was just 25% by all
means by LLE. i also observed that the final sample precipitated in
the autosampler. the sample was clean by SPE. but the recovery was
still the same. any suggestions to improve the recovery are invited.
Abhijith Rao
Research Assistant
Suven Life Sciences
Banjara Hills
Hyderabad
India
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Tacrolimus is highly lipophilic. Siliconization of glassware for
sample preparation and transfer may help. And also check whether the
extraction volume is sufficient or not. I have a paper on this which
you can refer if required.
Zahir H, Nand RA, Brown KF, Tattam BN, McLachlan AJ. Validation of
methods to study the distribution and protein binding of tacrolimus
in human blood. J Pharmacol Toxicol Methods. 2001 Jul-Aug;46(1):27-35.
Hamim
Hamim Zahir, PhD
Pharmacokineticist
NPS Pharmaceuticals
383 Colorow Drive
Salt Lake City, Utah 84108
Phone : 801-883 2580
Fax: 801- 583 2590
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Hi,
maybe you want to add 0.1 to 0.5 % acetic acid to the organic solvent
for LLE, this helped in some cases.
kind regards
Dirk
--
Dr. Dirk Scharn
Senior Scientist, DMPK
Jerini AG
Jerini AG
Invalidenstrasse 130
10115 Berlin, Germany
Phone: +49-30-9 78 93-369
Fax: +49-30-9 78 93-105
eMail: scharn.-at-.jerini.com
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The following message was posted to: PharmPK
We used to have the same problem with the whole blood extract samples
precipitating on the autosampler...column...et al...What worked for
us was
to run the extract from the LLE through a kind of filter plate. We
use one
from Varian called a Captiva plasma protein precipitation 96-well filter
plate Cat no. A5960045.
I know other companies make similar products, but I already had the
associated vacuum manifold for this one and it works well.
We run all our samples and standards through the same LLE and filtration
procedure so as to correct for any recovery problems...but 25% is
much lower
that the recovery we have seen when we checked more thoroughly
(closer to 90
something) Maybe someone else has ideas about that?
Good luck!
-Rachel
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The following message was posted to: PharmPK
Hi, Rao,
May I know what kind of analytical equipment you are using? HPLC-UV or
LC-MS? This will result in a big difference on your recoveries. Please
give the details on calculating your recovery.
Regards,
Zhi
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Abhijith,
You can improve the recovery using salt solution (e.g. 5% ZnSO4), as
a precipitating agent as well as hypertonic solution. This can be
followed by LLE.
Jignesh Kotecha
Torrent Research Centre
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The following message was posted to: PharmPK
It was my understanding that the zinc sulfate was used to lyse the blood
cells...i have recently pursued a SPE method from whole blood where
in we
employ zinc sulfate as an agent to lyse the cells...
I would appreciate any additional information that you may supply
along this
vein...
James ladd
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The following message was posted to: PharmPK
Hi,
In which the recovery is lower? samples or standards?
I would like to check the pH effect first.
Hope this help
Xiaodong
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