First test was done in the tube, came out dark red. No change

Second test was done on a plate, came out a lot more pinkish. But then turned dark red after a while. Idk if this is just because it was more space to spread out and not as concentrated as the tube.

Black gel tab

Thoughts?

I want to test some pregabalin but all I can find online are urine test strips. Can I use a urine test and test it by mixing the substance with water before taking it?