Chromatography Forum

Hi everyone,

Currently I have a problem with a Metrohm IC 761 instrument with column Supp4 , where the baseline has a high conductivity of a round 30 μS/cm. I am using Sodium biocarbonate: 1.7 mmol/L; 286 mg/2 L
Sodium carbonate: 1.8 mmol/L; 382 mg/2 L

I tried to rinse with distilled water, regenerate the suppressor with 50 mmole/l H2SO4.. It definitely improved but now its fixed. I also tried after I removed the column and still the same.


The only thing I don't do as suggested is the filtration process since I don't have at the moment 0.45 µm so I use bigger one.

Any suggestions what might be the causes?


Best regards,
Moaaz Shehab

Rinse the 3 suppressor units with the following solutions for about 15 minutes each:
1 mol/L H2SO4 + 0.1 mol/L oxalic acid and 5 % Acetone

For the continous regeneration we recommend 100 mmol/L sulfuric acid.

If the background conductivity is still high, check the cell constant of the detector with e.g. the Metrohm 6.2324.010 Conductivity standard 100 µS/cm, 250 mL.
See also the manual of the 761.