Chromatography Forum

I am using an ICS-1100 chromatography machine with sodium carbonate/sodium bicarbonate eluent. I have been noticing double peaks/shoulder peak for nitrate ion in my samples. Any suggestion on how to correct this? If i decide to dilute the samples, phosphate which is my major ion of interest will not be detected because the concentration is very low in my samples.

I have the same issue with you for almost a year now. And I'm using the same model.
I think the most probable reason is that the column is contaminated with metal ions.
The only way I can do is either dilute the sample or change the column.