Dionex polar-embedded columns

[MEH]

I am running a reversed-phase gradient analysis using THF & water (10% to 90% THF). My Zorbax SB-C18 col. retains the organic acids (maleic, fumaric etc.) poorly. Does anyone have experience with the Acclaim PA, PA2, or OA polar-embedded columns, which promise to retain polar compounds?

[Bryan Evans]

Organic acids are well retained on our Unison UK-C18 column:

http://www.imtakt.com/TecInfo/TI109E.pdf
http://www.imtakt.com/TecInfo/TI130E.pdf

[Mark Tracy]

Oddly enough, yes. I was part of the team that developed those columns. You can see the typical chromatograms and product info on the Dionex.com website. If you are doing organic acid analysis with these columns, the typical mobile phase is 50-100 mM Na2SO4 adjusted to pH 2.6, and no organic modifier is needed. Do you have any specific questions that are not answered in the product literature?

[MEH]

1. Is the OA column (PEEK column body) THF compatible?
2. Can you use NA2SO4 with an ELSD detector?
3. All these columns may work for my application. Is one of the stationary phases more stable under these conditions (pH 2.6 0-90% THF)?

Thanks for your help Mark. We have a U-3000 HPLC system scheduled for delivery this month.

[Mark Tracy]

1. The PEEK body is not recommended for >20% THF. Is there some specific reason for needing such a high concentration of THF?
2. You can't use Na2SO4 (or any other non-volatile salt) with the ELSD (unless you like plugged nebulizers). In any case, ELSD-compatible mobile phases will lose the volatile organic acids.
3. In general, the Acclaim PA2 is more stable than PA in acid conditions. Either way, I would recommend conditioning the column with blank gradients until you get a consistent baseline.

[ym3142]

Bryan,
did you use the 100% aqueous specified in the legends in your posted appliction?
Thanks

[mardexis]

I have had luck with some of the ion-exclusion type columns from Biorad and Phenomenex for organic acids. The embedded polars from various manufacturers have also produced some amount of retention in mostly aqueous mobile phases. I haven't been able to buy Dionex columns because I don't own Dionex hardware. I would be curious how they turn out for you.

Good luck,
Marc