Chromatography Forum

If anyone can provide any insight on the following, I would much appreciate it. I'm new to the IC world and to this forum but will help where I can.

DIONEX ICS-2100
K2CO3 eluent generator cartridge
Background conductivity sits around 13uS
New Suppressor and trap column. Guard column and analytical column are used but not old

3 point calibration (quadratic)

Standard 1:
1ppm Flouride, Chloride, Nitrite, Sulfate
96ppm Nitrate

Standard 2:
4ppm Flouride, Chloride, Nitrite, Sulfate
480ppm Nitrate

Standard 3:
10ppm Flouride, Chloride, Nitrite, Sulfate
960ppm Nitrate

All points on the calibration are fine except 1 ppm sulfate. I consistently get around 1.6. I tried a new lot for calibration standard.
The DI water for the carrier is open to atmosphere, I'm not sure that the container is being cleaned often. I thought the potential existed for microbio growth...

Does anyone have any ideas?

Thanks.

I have ICS1100. Lowest point in calibration for sulfate 0,5 ppm. LOQ is lower.
Try lineer curve or you may dilute "standart 3" ten times.
Check calibration solution for phosphate, its retention time is close to sulfate, they may overlap.

Thanks Therdem,

I traced the problem to a consumables issue. Something was contaminating the low end calibration. Thanks for the advice, I will keep that in mind should something similar occur in the future.

The only issue is I'm now seeing a doublet (peak split) with the new column on Fluorine...the fun never stops.