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The following message was posted to: PharmPK
I would very appreciate all suggestions on preparation of urine
sample for LC-MS analysis.
It was urine sample from baboons. I tried LLE with ethyl acetate but
there were still huge amounts of impurities.
Also tried solid-phase extraction: adjusted the pH to 2 or 4.2 with
concentrated HCl, wash with 0.1M HCl followed by elution with
methanol. All parent compound and metabolites were eluted out within
2 ml methanol (monitored by radioactivity). However, the pigment of
the urine also came out with methanol. The color is dark brown. I
think it will be not good for mass-spec so didn't try to analyze it.
Please give me some suggestions to solve this problem. Also
appreciate suggestions on feces sample.
Many thanks!
Ru Yan, PhD
OB/GYN
UTMB
Galveston, TX
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The following message was posted to: PharmPK
What is your drug characteristics.Is it basic, neutral or acidic?
What do you use for SPE? Most drug will elute in 100% methanol along
with all other junk if you only using reverse phase retention
mechanism. try to use waters oasis cartidge, they have different SPE
mechanisms cartridges that suitable for different analytes with
different pka. example MAX and WAX for acidic drugs amd MCX and WCX
for basic drugs depends on the strengh of the acid or base your
extracting. and HLB for neutral. They also have a lot of literature
regarding the use, even generic method so all you need is fine tune.
With LLE did you try back extraction? that may also help improving
you extraction
Good luck
Borri
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The following message was posted to: PharmPK
If your compound is retained in SPE (I assume you work in reverse-
phase) at acidic pH, you can try to elute it at high pH with lower
percentage of methanol or acetonitrile, i.e.: 50 to 70%.
Hope this help
Henri BENECH
CEA, France
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