Common Reagents for Indirect UV Detection

[Vlad Orlovsky]

Hello Everybody,

I am looking for a list of most commonly used additives for indirect detection. Need a good example of neutral, acidic and basic additive to monitor non-UV active compounds. I never used indirect detection, but don't expect this to be fun, but since a customer wants to do this, I have no choice but try. Can I use something like caffeine, phenol or benzoic acid? How about some common dyes?

Thank you for your attention.

[M Farooq]

One can agree that indirect UV detection can easily trigger migraines because of system peaks which can be larger than the analyte peaks. Secondly, these additives will modify the stationary phase itself.

For anionic additives phthalates, napthalene sulfonic acid might be worth trying. For neutral additive, salicylamide may be worth a try. Anyway, it might be good (never tried myself) to have a post-column indirect detection - i.e. the analyte and the UV absorber mix after the column outlet. In this way, system peaks might be easily avoided and the column will remain intact.

[Vlad Orlovsky]

Thank you, M Faroog.

Since we are trying to use mixed-mode columns for this task I would like to stay with neutral additive. I have benzenesulfamide in the lab, so will try something tomorrow. Task is to analyze inorganic cations and anions in one run.

[M Farooq]

Thank you, M Farooq.

Since we are trying to use mixed-mode columns for this task I would like to stay with neutral additive. I have benzenesulfamide in the lab, so will try something tomorrow. Task is to analyze inorganic cations and anions in one run.

I hope you don't get many system peaks given that your stationary has multi-modal interactions. Sulfate ion is often a major culprit. Please share any interesting observation.