[heyhey]

I would like to be able to determine whether a given curved surface of a material is modified with either primary amines or quaternary amines. Any ideas on how to go about this?

I was thinking about doing something that can determine hydrogen bonding on the surface. So at first I thought of water drop contact angle test but I don't think this is feasible on a curved surface. Then I thought that maybe I can test if the given surface reacts with carbodiimides (primary amines would, quartenary amines won't) but I would expect so little to react that the mass difference of CDI product left in the beaker would be unmeasurable. Is there perhaps some flourescent molecule that I could easily test to see if it conjugates to the surface? Is there some better and simple procedure that I can measure this?

I was thinking X-ray spectroscopy but I don't have access to this sort of instrumentation.

[wildfyr]

Fluorescein test. Used to quantify quaternary amines on surfaces

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC33409/.

For the amines, perhaps you can prepare an activated ester (either NHS or PFP ester) version of a dye molecule, and it should react quantitatively with surface amines.