Valproic Acid screening

Chromatography Forum: GC Archives: Valproic Acid screening
Top of pagePrevious messageNext messageBottom of pageLink to this message  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


Top of pagePrevious messageNext messageBottom of pageLink to this message  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.


Top of pagePrevious messageNext messageBottom of pageLink to this message  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?


Top of pagePrevious messageNext messageBottom of pageLink to this message  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 Ál becouse we knew evaporation could be a problem wtih valproic acid.


Top of pagePrevious messageNext messageBottom of pageLink to this message  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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