Stainles steel vs PEEK for Lanthanide separation

[vmocko]

Hi,
I'm new in IC chromatography. I need to eliminate metal contaminants in my sample. I'm separation lanthanides using a-hydroxybutyric acid.
So I'm wondering how much metal contaminants would I have when using stainless steel column, injector and tubing.. How much does the passivation of the column and tubing help and how often is it necessary? What concentration of acid should I use to achieve good passivation??
! What is going on during passivation??
Thanks for any comments/input!

[Markus Laeubli, Metrohm]

Dear Vmocko
More than 25 years ago we started our IC with full stainless steel systems. We found that most of the applications did work with that setup. But as you mentioed propper passivation was required.
Any way we did alkali, alkaline earth metal cations as well as some of the heavy metals Ni Cd Pb etc. without any problems.
In the meantime ous systems are all PEEK here of course we also do not see any drawbacks without the need of passivation.
Therefore, if you have the chance to work with PEEK, just go ahead. If not, at least give it a try.

We actually use 0.1...0.2 molar nitric acid for passivation. I actually don't know what exactly happens with the steel surface. Our criterion at that time was the ability to quantify phosphate again.

[DJ]

I believe nitric acid passivation puts a chromium oxide protective layer on the surface of the stainless steel.

Bear in mind column frits contain a good amount of the total stainless steel surface area.