Ion Chromatography 101

[mtnshawn]

Fellow chromatographers-
I am using the Waters Columns and the methods/MP's described in their column brochures. Waters 432 conductivity detector, Waters 2695 HPLC. The cation method works wonderfully and with the exception of subtle changes in RT is very reproducible with respect to the Waters Lit. However. . .

the anion (spefically Cl-, I haven't tried other anions yet) does not behave in the same manner as the Waters Lit describes. I keep encountering a dip right after the Cl- peak.

MP: Concentrate:n-butanol:MeCN:H2O (2:2:12:86)
Concentrate: Boric acid:Na gluconate: Na tetraborate:glycerin:H2O (18g:16g:25g:250 mL:~750 mL)

I have tried new columns/old columns and variations in the MP content.

Any suggestions??

Thank ya so much.

Shawn

[tom jupille]

If you have enough sensitivity, try diluting your sample with mobile phase. Negative "system peaks" are not uncommon with conductivity detectors.

If it is a system peak, sometimes tweaking the pH can move a negative dip away from a peak of interest.