NaOH and HPAEC-PAD
Posted: Sun Nov 25, 2007 8:00 pm
by rick1112
hi
does anyone know the reason can KOH be used in place of NaOH for analysis in HPAEC-PAD analysis for carbohydrates?? is there a aprticular reason why NaOH is prefered??
Posted: Wed Nov 28, 2007 7:03 am
by XL
NaOH can be replaced with KOH for HPAEC-PAD applications.
NaOH vs KOH in HPAEC-PAD
Posted: Wed Dec 12, 2007 8:44 pm
by Chris Pohl
Rick,
There is no fundamental reason for choosing KOH over NaOH in this separation mode. The pH simply needs to be high enough to control ionization of carbohydrates in the mobile phase. Assuming the cation isn't electroactive or weakly basic, it will work for this mode of chromatography. The only reason I first used sodium hydroxide when I developed this mode of chromatography was that I had a ready source of 50% sodium hydroxide in the lab and none of the corresponding KOH solution. In theory, concentrated sodium hydroxide solution should have a lower level of carbonate due to the lower solubility Na2CO3 relative to K2CO3 but the differences should be quite small and you shouldn't observe any difference when switching from one to the other as previously noted. The important point is that the hydroxide needs to be substantially free of carbonate, something which is achieved with 50% NaOH but not NaOH pellets since the latter is invariably coated with a film of sodium carbonate. Of course, if you are using an eluent generator to produce the hydroxide you don't have to worry about carbonate since the generator produces carbonate free hydroxide.
Chris