Negative Peak in IC analysis

[hchauhr]

Hi Guys,
I am using ICS-3000 sytem for cation analysis. But due to some reasons I am getting nagative peak. The column and eluent detail are as follow:
Column: IonPac Cs14
Eluent 10mM Methasulfonic acid
analyte: Tromethamine
Flow rate: 1.0ml/min
Cation Suppressor: none
Please can you help if know the answer.
Thanks

[Markus Laeubli, Metrohm]

Dear hchauhr

You are running a non-suppressed cation analysis. On the column the sample cations will be exchanged stochiometriclly against eluent cations (H+). After the separation your peak segment will have the total concentartion of the eluent. But consiting of the concentration of the sample cations + the initial eluent cation concentration - the sample concentration.

As H+ is the ion with highest equivalent conductivity, an exchange of H+ by any sample cation will reduce the overall conductivity.
Therefore the negative signal which you are observing is absolutely correct.

The response of the net signal is proportional to the difference between the equivalent conductivity of the sample cation and the equivalent conductivity of H+. This always is negative.

[hchauhr]

What is a solution to this problem? I have been told that it is a software issue.
Thanks

[Jason Wmson]

You could try changing the detector factor in the Chromeleon server configuration for the detector module.
The default is 1.0. If your value is 1.0, change it to -1.0. This should work for your application but may need to be changed for other applications.

[hchauhr]

Thanks Jason! You are a star.