I am trying to detect the presence of a coating which has nanogram amounts of transition metals. I've seen many products that can detect nano amounts of various transition metals in the aqueous form, but not as a coating.

I am currently thinking about applying a drop of some solution that changes color in the presence of transition metals. I am currently a bit stumped on this problem and would appreciate any information or leads on the subject.

thanks a lot

Welcome, Jollyholly!

If you want to detect the presence of a coating, maybe its transition metals aren't the best way? Colour, thickness, hardness, roughness, surface resistivity may be easier to use than chemical properties.

OK, admitting I got it wrongly, or such methods have drawbacks for you.

I saw maybe one year ago an automatic analyser that - if I remember - makes low-intensity sparks in air towards the unknown metal and deduces the complete elemental composition from the optic emission spectrum. Said (at least by the manufacturer) to make no trace on the object. It was almost affordable, maybe something like 10k$.

You may also look at UV fluorescence. Or neutron activation, but it has serious drawbacks and doesn't see scarce elements.

In both cases, you will get the elemental composition right at the surface, which should fit a surface coating. In fact, you'll even know if it's clean.

A tunneling electron microsope.

To detect nanoimpurities (ppm levels), use secondary ion mass spectrometry (SIMS). You can do a depth profile and find out the concentration as a function of depth.