By Greg on Sunday, March 16, 2003 - 06:50 pm:
G'day from Downunder,
I am wondering if many of the readers are doing any analyses for oxalic acid, preferably by RP-HPLC?
We have problems of retention being poor on Alltima C18 and thus being "swamped" by the large void peak of both soil and plant extracts.
By Anonymous on Sunday, March 16, 2003 - 07:36 pm:
RP is no good for oxalic acid. Can you try ion pairing? Use the hexadecyldimethylethyl ammonium ion! Alternatively, you can try ion-exchange, ion exclusion, or HILIC, if you have the right columns.
By HW Mueller on Monday, March 17, 2003 - 02:35 am:
Hypercarb graphitic columns worked well for us.
By Tom Mizukami on Monday, March 17, 2003 - 08:24 am:
Alltima would not be my first choice. I would use one of the newer polar embedded non-endcapped columns with dilute phosphoric acid as the MP.
You could try this column:
http://www.esind.com/pages/aquasep.html
Good Luck
By Tony on Thursday, March 20, 2003 - 02:11 am:
YMC ODS-AQ and 0.05M KH2PO4 pH 1.8 with H3PO4 shows some retention for oxalic acid. Increasing the ionic strength of the mobile phase may elute oxalic acid far enough away from the void, so that it does not get swamped.
By David Blais on Thursday, March 20, 2003 - 10:37 am:
Currently I work with assays for similar small organic acids and have found Phenomenex's Synergi columns (Hydro-RP and Polar-RP) to work well for retention of poorly retained molecules. I use 0.1% Phosphoric Acid with both of these columns for glycolic acid and lactic acid with RTs of 3.1 and 4.1 minutes, respectively.
By Greg on Monday, March 24, 2003 - 03:58 pm:
Thanks to everyone for their contribution, greatly appreciated. i shall try the suggestions.
Thanks again
Greg
By Anonymous on Thursday, May 8, 2003 - 10:36 am:
If you are familar with Alltech HPLC columns, I suggest you take a look at the newer Prevail line of columns. They specifically sell an organic acid column (Prevail OA) which functions as a reversed phase column. I have used this column and it performs quite well for oxallic acid. The key is to modify pH and work at a low pH, lower than 2.5. This will help protonate the acid and get maximum retention. The 250mm long column should do the job. The problem with Alltima is that it is not "water-wettable" and will collapse in high aqueous environments. Prevail will work well in 100% aqueous which will help maximize retention.
By maris on Friday, May 9, 2003 - 02:02 am:
We developed very simple method for Oxalic acid using RP-HPLC when ion-paring reagent has been used; it gives us possibility to "play" with the retention in wide range.