Chromatography Forum

I was wondering if somebody knows a good C18 column running at pH=1.0. I used SiliaChrom SB C18 for more than 500 injections no stop (300 hours) at pH=1.0 and no degradation, same retention and peak shape for all peaks. So I would like to test another HPLC C18 column with the same condition.
Thanks

I've never gone so low cos there was no reason to, but... I think all SB columns should do pretty well, there's even an article about some characteristics and their dependence on column stability in low pH
Development of an accelerated low-pH reversed-phase liquid chromatography column stability test
Journal of chromatography
2004, vol. 1060, no 1-2 (255 p.)

Hi

I think you can try xbridge waters column or xterra.

Alltech Alltima HP C18 can work from pH 1 onwards

if you're pushing the extremes of pH, try a polymeric particle instead of silica.

I don’t think the silica support per se, would have any problems with an acidity of pH 1.
The problem is the actual stationary phase, or rather the bonds between support and ligands.

Best Regards

Thanks for the Info Danko,

So it would seem that substituting materials which are comprised of a polymeric support for the traditional silica is appropriate for applications involving extremely basic mobile phases and/or analytes?

Do the differences between silica and polymeric supports in areas such as stationary phase bonding and processes like silanol endcapping offer zero advantage at low pH?

Hi Hazmat,

For basic mobile phases (pH > 7.5) the polymeric stationary phase support is typically the best option. Although, some manufacturers have developed materials of more resistant character compared to pure silica (e.g. organic/inorganic hybrids).
Regarding endcapping, the technique/process is not of that huge importance in cases of employing very acidic mobile phases. Potential residual silanols are protonated and thus harmless at low pH values.

Best Regards

monofunctional ODS + TMS endcapping = narrow pH range

Endcapping can come off *very* quickly at low pH. The argument is that hydrolysis of the Si-O-Si bond occurs faster at low pH. But a hydrophobic bonded phase like C18 has such a low solubility in aqueous solution (or is so hydrophobic; take your pick!) that it is likely to stay in position long enough for the bond to re-form. That means that loss of bonded phase occurs relatively slowly.

As you go to shorter (less hydrophobic) chains, the probability of loss for any cleavage event increases, and the loss of bonded phase is faster.

End capping is effectively C1. I've heard anecdotal evidence of having to "condition" end-capped columns for a couple of days with TFA containing mobile phases, only to find that the "conditioned" column now worked just like the non-end-capped equivalent!

Hi all,

Stability of silica is not a question under these extreme acidic conditions. It is proper to consider the stability of bonded phase. Of course it depends of technology used to prepare the stationary phase. As far as I know, ZORBAX StableBond is the first technology to produce HPLC columns for use with low pH mobile phases. It includes 6 types of bonded phase and 2 different types of protection for the siloxane bond - which is under attack at low pH and could be easily hydrolysed. StableBond offers even a column for work at 100% aqueous mobile phase and pH down to 1 - and this is very convinient solution for analysis of organic acids under their pKa (in order to obtain adequate retention). So probably other brands also offer similar columns...but usually the original works best.

Special regards to Danko - what's up - cyanogen78@abv.bg - have a lot of news