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Dear all,
I am facing a problem in method development regarding carryover
which is 50% greater than LLOQ, i tried many compositions of IPA, ACN,
WATER, AMMONIA, as a rinsing solvent.
Nature of my compound is basic and MP:3mm amm.acetate:ACN(20:80).
Waiting for your suggestion
Regards,
Rahul vats
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Hi, Rahul,
Usually contamination of the injection valve is the most common source
of carryover problem.
Is your system HPLC or LC-MS/MS?
Regards,
Chunling Wa
Memorial Sloan-Kettering Cancer Center
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Dear Rahul
Since your compound is basic so the most effective washing will be a
combination of aqueous and organic with some strong acid in it. Try
using 1-5% of formic acid in water with methanol (20 to 50%) or neat
aqueous wash with acid in it.
Hope it will help.
Regards
Bajpai (Lakshmikant Bajpai)
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It really depends on how basic is the compound. If it is a weak basic
drug, strong basic modifier (such as triethylamine pKa=12) instead of
acid should be can be added into the mobile phase to suppress the
ionization of the drug, so the drug can be eluted out of the column.
I strongly suggest using gradient elution if it is because of the strong
retention of your drug on column.
Chunling Wa
Memorial Sloan-Kettering Cancer Center
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First is to identify the source of the carry over. Use strong and weak
washes with adequate rinsing cycles prior to injecting samples. I also
find it useful to make sure that the MS source is clean. Try cleaning
your LC column first with 50% organic and then with higher organic
solvent. I suspect the MS source or an auto sampler related issues.
Regards,
Anila
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Hi Rahul,
On top of all suggestions given by the experts, you can try an option
of injecting an empty vial (air) to check the contamination of
injector or its loop.
.at.ks
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The following message was posted to: PharmPK
Try this: If it is an isocratic system, make an injection of zero
volume.
If it is a gradient, repeat the gradient without an injection. This will
suggest whether the contamination is column residual or tubing. You can
also remove the column to point to injector/tubing
Poor wash or worn rotors in the injector? Stickiness of your compound to
tubing or column.
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Hi,
Carryover can be caused by the column and/or the autosampler. Maybe
it is better to identify which one caused the problem. If you inject
the blank several times, the carryover is not minimized. Then that is
not carryover, you may need to do some PM for your system.
Hope this help.
Xiaodong
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Ed,
How do you repeat the gradient without an
injection? I am very interested in this suggestion.
xiaodong
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Set the system to make additional cycles without injection.
After the first re-equilibration, at the estimated time a second
injection
would occur, the gradient and re-equilibration steps are repeated. It's
actually seen as one program-and one injection initiates it. You will
also
need to extend detector parameters.
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If you have a manual injection port just turn it assuming you have
filled in the sample. That should do. There must be a similar way to
use the auto injector too.
Manish Issar, Ph.D
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The following message was posted to: PharmPK
hi rahul,
i think this is not a method prablem, it is instrumental problem,
you can confirm it with injection of Reconstitution Solution (RS).
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