Suppressor reduces conductivity even when off?

[Foxdash]

Hi.

I'm completely new to IC, and am wondering if this suppressor behavior is normal...

The conductivity of the eluent (sodium hydrogen carbonate) is about 13 μS regardless of whether the suppressor is on or off. If I keep everything else the same except bypass the suppressor, the conductivity is about 390 μS.

Am I correct to think that the suppressor shouldn't be reducing the conductivity from 390 μS to 13 μS even when it's off? Seems a bit fishy to me.

I'm using a used Dionex DX-500 IC system (CD20 conductivity detector, LC25 oven, GP40 gradient pump, ASRS 300 4mm suppressor, IonPack AS4A-SC column). The suppressor is in autosuppression recycle mode. I know the suppressor is off when I think it's off because the bubbles in the regen out line go away. I don't think there is a clog because if I disconnect the line from the eluent out port, I can see eluent drip out; and if I disconnect the regent in, I can also see eluent drip out.

Thanks

[sbrand]

Hi

With the AS4A i quess you are using a Carbonat/Bicarbonat (1.7/1.8mM) eluent. The suppressor has a high capacity therefore he will continue to suppress even if he is off. After a while (depending on the flow and concentration of your eluent) the conductivity will increase. I would not reccommend to do that because after turning on the suppresssor again it takes a longer time for equilibration.

Best regards,

[Foxdash]

I see. I will not worry about it for a bit then.

Thank you for the response!