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The following message was posted to: PharmPK
Dear all,
Can anybody suggest me it is necessory "During project sample analysis
in bioanalytical while aliquoting the subject sample and CC standard
and QC sample, it is necessory to first rinse the tip with plasma than
aliquote into respective ria vials",
Thanks
veeda clinical research
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Hello,
Notwithstanding the poor expression, this statement refers to the need
to "pre-wet" a pipette tip. The first time a liquid is taken up into,
and expelled from a tip it will leave a residue of fluid inside the
tip. Thus the volume dispensed will be less than the volume
expected. Once this has occurred for the first time (ie. it has been
pre-wet) this will not be such an issue as there is already a residue
inside the tip. It is standard practice for using a pipette. Anyone
who has spent time in an analytical lab would do this without even
thinking about it, much less actually need to be told to do it.
Regards,
David
David Foster, PhD
Lecturer
Sansom Institute
School of Pharmacy and Medical Sciences
Playford Building
Room P4-08
City East Campus
University of South Australia
Adelaide SA 5000
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The following message was posted to: PharmPK
For precision pipetting of a small volume (uL), it is necessary to
pre-wet the pipette tip for accuracy and reproducibility by pipetting
the matrix once first before the measurement. There is no such need
pipetting a larger volume (100s uL) because the matrix needed to
pre-wet the pipette tip surface is so small it is inconsequential.
Hope this help.
TK Chen, Ph.D.
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The following message was posted to: PharmPK
Anything that will improve accuracy and precision should be done.
Is the material you are pipetting of the same viscosity or close to
that of water?
If it is not, positive displacement pipettes are recommended.
(Plasma does have a higher viscosity)
If you do not have positive displacment pipettes, prewetting the tip
or reverse pipetting is recommended for plasma, regardless of the
volume.
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Yes, it is necessary to pre wet the tip this will reduce your volume
variation.
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