Ion exchange HPLC tips

[vmocko]

Hi,
I'm starting an ion exchange HPLC (previously done mostly RP-HPLC) so I could use some advice.
1. how to rinse system from the buffer in mobile phase - when the system is not use it is necessary to rinse it from the buffer so the pumps won't get damaged.. Is there a good way to do without rinsing the column? I'm thinking to have a flow switch valve so the system can get good rinse but not the column (so I do not have to wait for the conditions to equilibrate and also ion-exchange resins have the tendency to shrink/swell in different composition of the mobile phase so I'm worried about shrinking and expansion of the resin).
2. I'm using purely aqueous buffer, what would be a good rinsing mobile phase? According to what I found pure water is not recommended because of the possible microbial growth.. So a small amount of organic solvent is recommended like methanol.. How much methanol (other) solvent to use to prevent the microbial growth?
3. any other tips for newbie in IC-HPLC? Good literature to read...

Thanks!
Veronika

[danko]

Hi Veronica,

Depending on how long the system is going to dwell (stay unused) I don't think you need to worry about bacterial growth if you use pure water and give the system a day or two off. After all an HPLC system is not the best thinable medium for a micro-organism to thrive in

You don't have to worry about stationary phase support shrinking/swelling either. It is usually seen when organic modifiers (like methanol etc.) are used - especially shifting from aqueous to organic and back.

But flushing the system with pure water is always a good idea after using salts - wich is the scope of your plans.

Best Regards

[Markus Laeubli, Metrohm]

Dear Veronica

danko is right... anyway I would like to add a few points.

1. check your column leaflet about any change in solvent. Some columns do not like pure water at all.
2. Micro-organisms are able to grow anywhere! Therefore when stopping the system for longer time I recommend to finally keep it in e.g. 25% methanol.
3. Flushing the system with water: make sure that at any time the components are miscible.

Best regards

[vmocko]

Thanks for the suggestions!
V