Page 1 of 1
Negative Peak in IC analysis
Posted: Thu Nov 10, 2011 2:14 pm
by 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
Re: Negative Peak in IC analysis
Posted: Fri Nov 11, 2011 8:13 am
by 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.
Re: Negative Peak in IC analysis
Posted: Fri Nov 11, 2011 9:52 am
by hchauhr
What is a solution to this problem? I have been told that it is a software issue.
Thanks
Re: Negative Peak in IC analysis
Posted: Tue Nov 15, 2011 10:04 pm
by 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.
Re: Negative Peak in IC analysis
Posted: Thu Nov 17, 2011 12:27 pm
by hchauhr
Thanks Jason! You are a star.