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Dear Members
I am in the process of developing a Bioanalytical
method for a molecule.
here peculier thing is we are observing sodium adduct
ion as the most prominent and intense while infusing
itself. We are also getting the protonated ion around
30%, sample is in methanol and we thought to avoid
glass ware contact. Even though same thing is
observed. This is observed on two instruments API 3000
and 4000.
So LC method is developed and performed a PK in
rats. Though we monitored M+1-Na as well as protonated
ion(M+1). Sensitivity is better with sodium adduct ion
only.
Calibration curve is good in terms of accuracy for
sodium adduct.
Now Literature says that they have done with
protonated ion only.
We are thinking that contamination may be from
standard compound, tubings.
we appreciate if any body can suggest the reason like
how to avoid it and/or how to genetare insource Na
ions while running pk.
We have tried with NaCl(1mM)1% in mobile phase, but
ionisation was suppressed significantly.
Thanks in advance
RajaReddy Kallem
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Hi
How about using Sodium acetate/formate instead of NaCl in your mobile
phase thereby you would be forcing predominantly the formation of
Sodium adduct?
Raj
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You could try using 10 mM Amm. Acetate(volatile salt), which would
force it to form ammoniated adducts. you may want to buffer it with
formic acid. Ammoniated adducts are easy to break to product ions (if
you need to).
Has helped me in the past.
VK
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The following message was posted to: PharmPK
Hello Raju
If you really want to generate the sodium ions in the source you
could add a pinch of sodium iodide in the MP rather than sodium
chloride, it works better and do use as less as possible otherwise it
will also show the signal supression.
If you want to avoid its formation, you can try the following:
1. Use ammonium formate/acetate in the mobile phase as it will
replace the sodium with ammonium ions which can break easily to
generate ammonia and the M+1 ion.
2. Try to avoid methanol as the solvent and do check the infusion
itself with acetonitrile solution of the stock.
Hope it will be helpful.
Bye
Bajpai
(Lakshmikant Bajpai)
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Hi,
I found that the ratio between [M+H] and [M+Na] is temperature
dependent; the higher you analyzer temp. the more predominant is the M
+Na adduct.
Maybe you can simply lower the temperature at the spray / ion-
transfer device.
I hope this helps!
Dirk Scharn
Dr. Dirk Scharn
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
Dear Raju kallem,
Adduct formation is a characteristic of electrospray ionisation. Many
times
this will be a useful property to enhance sensitivity . Our general
observation is, API instruments tend to give sodium adduct.(I don't
know is
there any scientific basis for this, like ion optics).
One strategy to avoid adduct is to achieve a balance of declustering
potential and various gas controls. Adduct is believed to fragment with
higher voltage and gas pressure.
If LOQ on sodium adduct is higher than parent, then you can use sodium
adduct for quantification.
Interestingly, in literature, have they used ABI instrument or some
other
manufacturer? Ease of adduct formation varies from instrument to
instrument.
Thanks,
Vinayak Nadiger
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I had a similar problem (sodium adduct being higher than the M+H
peak) which
was solved by introducing a 0.1% formic acid in the aqueous phase.
Federica
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Hi!Raja
You will find in mass analysis there are few drug compounds and
intermediates that generally give sodium adduct with M+1(protonated
ion).
There are few possibilities that you have to consider
1)Check with your vendor the mass data of compound you used for PK
study.There is a possibility that your compound has sodium adduct.
2)Water and glass wares you used for the preparation of mobile phase.
3)Clean the ionization orifice and curtain filter from inside and
outside.
I hope this will help you.
Yogesh Patil
Graduate Research Assistant
Department of Pharmaceutics
Wayne State University
Detroit,MI-48202
313-577-8892
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Try Na acetate 50 microM. I used that in many instances.
1mM is too too much.
Regards,
laurian vlase
Vlase Laurian
MD, PhD, Pharm. Chem.
Teaching Assistant
Dept. of Pharmaceutical Technology and Biopharmaceutics
Faculty of Pharmacy
University of Medicine and Pharmacy "Iuliu Hatieganu"
13, Emil Isac
Cluj-Napoca, Cluj 400023, Romania
email:vlaselaur.-at-.yahoo.com
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