Qualitative Amphetamine Test for Caffeine

[G.Patton]

Due to cases of total amphetamine substitution for caffeine (or mixing of amphetamine with caffeine) we would like to present the qualitative method of caffeine determination in the sample. You will need:
1. Concentrated nitric acid ~68% (you can buy it at any chemical reagent stores)
2. 25% Ammonia solution (10% ammonia solution is inappropriate) which could be bought at any online stores with delivery

To determine the sample composition, do the following steps:

1. Put the sample into white or transparent glass or any other container which is resistant to heating. The material and the color are important because you need to observe the reaction result.
2. Add concentrated nitric acid
3. Evaporate to dryness.
4. Add 25% ammonia solution.
5. Evaporate to dryness.

Compare the reaction result to the photo below:
1. In case of total amphetamine substitution for caffeine, the result would be as in the photo:

Spoiler: Case 1

2. In case of mixing of amphetamine with caffeine (in this case the composition is 70% of amphetamine and 30% of caffeine) the result would be as in the photo:

Spoiler: Case 2

3. In case of pure amphetamine sample, the result would be as in the photo:

Spoiler: Case 3

Conclusion:
As higher concentration of the substance in the sample, as brighter the yellow color. The oil stain is occurred while adding ammonia solution to amphetamine. The red-brown color of dry residue is occurred while adding the ammonia solution to caffeine.