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Dear all
I would like to ask one doupt regarding positive and negative mode
method development in LC- MS /MS. I am in need for develop methods
for some drugs that one molecule is positive mode and another
molecule is negative mode is there any possibilities and my internal
standard should be what mode.
Does any one come across like that problem and what is the solution.
I would appreciate all comments. Thank you.
A.Karthik
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The following message was posted to: PharmPK
Dear karthik
For the combination of drugs there is possibility to
arise such issues, as one compound can ionize in
positive and another one ionize in Negative modes.
The instrument can be switch over to both positive and
negative mode. where the method should have two
segments (each segment have different tuning
parameters i.e positive and negative) and there should
be better resolution between the two peaks of your
interest.
Regarding the internal standard you can use any one
compound either it can be ionizes in positive or
negative modes, again it depends on the resolution of
your for all your compounds.
I think such methods can also affect the instrument to
keep switching to positive and negative modes. Its
better that you can clear this issue with your
instrument engineer.
Hope this information may help you
Wish you good luck
Regards
Venku
G.Venkatesh
PhD Research Scholar
Drug Research Centre
University Science Malaysia
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Dear
It is very simple, just try to resolve the two peaks
chromatographically, and then apply the criteria of two different
period if using API-4000, or use the criteria of Two segments f using
thermofinigan instrument. This will definitely solve your problem and
along wth this your instrument will also get the time to stabilize
the switched voltages. IS can be of either category, preferably if
available in both the parts of acquisition then it is the best, but
if only one peak in one part of the acquisition, it should work.
Regards
Deepak Jain
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