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By Yury on Monday, June 21, 2004 - 02:50 am:
Colleagues,
I’m working with plant extracts. For this extracts I’d like to separate amino and organic acids from sugars prior to derivatization and GC/MS analyses. I’ve herd that it’s possible to use Sep-Pak or other ion-exchange cartridges to separate acids and sugars.
Could anybody tell me which type of cartridge I should choose and how to use it for this application?
Thank you in advance,
Yury
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By Uwe Neue on Monday, June 21, 2004 - 02:28 pm:
Ion exchangers will do best. Acidify the sample with formic acid, then use a strong cation exchanger like Oasis MCX to capture all positively charged compounds (amines). Sugars will break though unretained. Wash with methanol to release neutral compounds and mildly to strongly hydrophobic acids. Release the amines again from the cartridge by changing to alkaline pH (ammonia) in the presence of 90+% methanol. To separate the neutral compounds from the acids, dilute the second (methanol) fraction 1:1 with a strongly basis solution (ammonia), then bind the ionized acids on an anion exchanger such as Oasis MAX. Wash all neutral compounds out with methanol, then elute the retained acids with 90+% methanol acidified with a suitable acid (formic, HCl). The very polar sugar fraction may still contain a few acids, which can be retained on the anion exchanger after changing the pH to a basic pH. You cna find such protocols and more details on the Waters website.
Colleagues,
I’m working with plant extracts. For this extracts I’d like to separate amino and organic acids from sugars prior to derivatization and GC/MS analyses. I’ve herd that it’s possible to use Sep-Pak or other ion-exchange cartridges to separate acids and sugars.
Could anybody tell me which type of cartridge I should choose and how to use it for this application?
Thank you in advance,
Yury
-------------------------------------------------------------------------------------------------------
By Uwe Neue on Monday, June 21, 2004 - 02:28 pm:
Ion exchangers will do best. Acidify the sample with formic acid, then use a strong cation exchanger like Oasis MCX to capture all positively charged compounds (amines). Sugars will break though unretained. Wash with methanol to release neutral compounds and mildly to strongly hydrophobic acids. Release the amines again from the cartridge by changing to alkaline pH (ammonia) in the presence of 90+% methanol. To separate the neutral compounds from the acids, dilute the second (methanol) fraction 1:1 with a strongly basis solution (ammonia), then bind the ionized acids on an anion exchanger such as Oasis MAX. Wash all neutral compounds out with methanol, then elute the retained acids with 90+% methanol acidified with a suitable acid (formic, HCl). The very polar sugar fraction may still contain a few acids, which can be retained on the anion exchanger after changing the pH to a basic pH. You cna find such protocols and more details on the Waters website.
