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The following message was posted to: PharmPK
Dear Colleagues:
We are experiencing ion suppression effects in some of
our recent LC/MS/MS analysis, which we believe is
linked to the presence of anticoagulant (lithium
heparin); we do not see this with the same samples
prepared with sodium heparin. There are some
publications suggesting lithium has more ion
suppression effects compared to sodium. I would like
to know if anyone else have seen this before and get
some insight into this such as concentration
dependency of this effect. Are there any Na-heparin
coated microcontainer (less tahn 500 uL) commercially
available?
Rostam
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The following message was posted to: PharmPK
I have seen several references that indicate EDTA (K2, K3?) is a better
anticoagulant than Li Heparin. I have been using K3-EDTA.
Heparin from what I can find (google search on heparin, then click on
images tab) is a polymeric species with carboxylate, amidosulfate,
sulfate groups, etc.). Seems to me that less likely ion suppression
problems with EDTA since monomeric and problably elutes towards the
front of gradient..
Heparins could occur over a large area since polymeric?
I wouldn't think that Li vs Na heparin would matter, since most salts
would exchange out using either formic, acetic, ammonium formate, etc
and be eluted in the column volume as lithium or sodium with a counter
ion. Though I have never used heparin anticoagulants..
See where authors said heparin a problem..
Hong Mei, et al Rapid Communications in Mass Spectrometry, 2003, 17,
97-100
Another said EDTA much better than heparin especially if multiple
freez-thaw cycles..
Josephine S. Villa et al, Rapid Communications in Mass Spectrometry,
2004, 18: 1066-1072, p 1066-1072
James Little
Tel. No. 423-229-8685 office
Tel. No. 423-229-8022 lab
Tel. No. 423-367-0914 Cell
"A Little Mass Spectrometry and Sailing":
http://users.chartertn.net/slittle
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Hi Rostam,
Something to watch out for in the microcontainers are dispersal/
wetting agents which are PEG-based molecules. there to make the anti-
coagulant disperse and dissolve faster. We found this a worse
problem with Li-Heparin tubes and switched to EDTA. Run a blank in
full scan mode and look for a regular series of peaks separated by 44
mass units. These compounds interfere with ionisation and may hit
the analyte or the IS, etc. Do you run a gradient to high organic to
elute all the late running background, because sometimes they elute
in later runs?
For some jobs, to avoid PEG-based interference, we revert to heparin
solution in blank tubes - and make sure they are blank first!
Let us know if you get it fixed.
Regards.
Ted
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