Hi, I am currently trying to replicate a method which uses DDAB coated monolith for anion analysis, however, I am having trouble seeing any peaks. Following the procedure described in a research paper I coated the onyx C18 monolith with DDAB for 30 min prior 30 min wash with 1 % acetonitrile. Afterwards I washed the excess DDAB off using deionised water. Finally, I equilibrated the column with 5 mM phtalate (pH 7.5) which was recommended in the research paper that I am following. Unfortunately, I cannot see any peaks (except for the injection peak) when injecting 50 ppm nitrate, nitrite and phosphate. I am wondering if anyone has experience in working with monoliths and could advise me on where I am going wrong.
Thank you very much for your support.