Alternative eluent for metrohm A supp 5 column

[Ripx2000]

Hi,

I'm doing trace analysis on nitrite, but it's kind of hard for me to detect it precisely because of the interferences from chloride.
Chloride r.t.: ~5mins; Nitrite r.t.: 6mins

And usually my sample matrix contain high level of chloride.

From my understandings, the things that I can do:
1. Use sample cleanup cartridge to reduce the level of chloride. (Drawback: price)
2. Use different column, or longer column.
3. Change composition of eluent. (I'm using sodium carbonate and sodium hydrogen carbonate)

The system that I'm using is Metrohm 881 Compact IC pro and dosino gradient, column: A supp 5 150/4.0.

Currently i'm trying on different composition of sodium carbonate and sodium hydrogen carbonate. Somehow the separation of chloride and nitrite doesn't being affected much but the runtime extended significantly.

Is there any alternative eluent that would improve the separation of these 2 ions? Or other solutions?

Thanks.

[James_Ball]

When our columns get old (A-Supp5) we dilute the eluent to bring the retention times later to where they were before. Have you tried using the same ration of carbonate/bicarbonate but reducing the concentrations 20% or 30%?

You may also be able to increase column temperature(if you have column heater) and increase the flow 10% which will give sharper peaks for better resolution.

The alternative would be to use an A-Supp7 column for more separation between chloride and nitrite.