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Posted: Mon Feb 09, 2009 10:41 am
by Bryan Evans
Kostas -
I understand not being able to switch phases.
Vlad -
Now I'm curious. Does SIELC Technologies have a method for the separation
of dehydroascorbic acid, isoascorbic acid, and ascorbic acid?
Posted: Mon Feb 09, 2009 3:16 pm
by HW Mueller
kliaros, registered or not, I tried to be very diplomatic above, my unabridged feeling on this method is: utter nonsense. To get an ion pair method, which one does not need as ascorbic ACID has sufficient retention and is quite inert, one uses a pH at which the acid has been converted to ascorbate which is known to very readily react with oxygen, especially with all these metal ions present.
Posted: Mon Feb 09, 2009 3:41 pm
by juddc
The problem isn't so much with your column or mobile phase, but the pH of your sample preparation. Having the pH at 6.5 in a predominantly aqueous solution is going to accelerate degradation. Drop the pH of your sample prep solvent to about 2.5 and check repeatability. My bet is that it will improve significantly.
Regardless of the registration status of the method and whatever that means, if you don't change your method, you won't change your result.
If you MUST have your sample prep solvent at pH 6.5, add a ton of sodium metabisulfite or something like it to your prep solvent and see if that helps.