We have a 883 Basic IC plus, on whitch we analyse the anions Fluoride, Chlorde, Nitrate and Sulfate. I resently change the analytical column and calibrated for all the anions. After this, all the controls were fine the first day of analysis. The next day, the fluoride peak became smaller and smaller for each time I ran the control. I tried to change the inline filters, pump tubings, and remove the guard column. After that the background conductivity beacme really high (above 600 µS/cm). I then cleaned the MSM, and the background conductivity became normal, but the Fluoride anion-peak/area is still too low.

In the internal controle we are using, all the anions mentioned are present, but only the fluoride peak is lower than normal. The others are within acceptabel values.

Have anyone had a similar problem, and can help me with what to do next?