By lisa on Tuesday, November 16, 1999 - 11:06 am:
Does anyone use solid phase extraction to screen for and/or quantitate valproic acid? I am finding significant loss on evaporation and post-column processing, and would like ideas on a new procedure we are attempting to institute in the lab.
Thanks, and sorry it's slightly off-topic!!
Lisa
By jclark on Tuesday, November 16, 1999 - 11:32 am:
To employ a reverse-phase SPE mechanism, you need to have the pH of your solution <2.6. Is it possible you're overloading the cartridge? The rule of thumb when you're using C-18 for SPE is that the maximum load the sorbent can take is 5% of it's bed weight. That would be 25mg/500mg sorbent.
By lisa on Tuesday, November 16, 1999 - 03:39 pm:
Actually, we use mixed-mode SPE, with the VA hanging on the C8, not the ion exchanger. What I think is happening is that we're losing it in evaporation, and I'm wondering if anyone else sees this?
By fin on Sunday, November 21, 1999 - 01:24 pm:
in our lab we extract valproic acid by LLE. after the extraction we evaporat till 200 µl becouse we knew evaporation could be a problem wtih valproic acid.
By lisa on Monday, November 22, 1999 - 08:54 am:
We also extract known positives by LLE for quantitation; however, our screening protocol for seizure disorder cases involves a solid phase extraction. And I *really* don't want to have to do two different extractions for screening...
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