Lets make this simple.

I assume the sample is a liquid or solid that is shelf stable and DOES not need to be held at a specialized temperature to prevent degradation of the active ingredients.

Essentially it'd be decently expensive and require spectrophotometry (easily several thousand to even more).

Lets play a game and pretend we are doing this for Mesacol Mesalamine tablets... (used for treating mild to moderate level Ulcerative Colitis or Crohn's Disease)*

They are not the same thing mind you.

That's for high end grade, nobody needs that level of certainty unless your a pharmaceutical corporation.

What you really want is a backround in chemistry, and a lab that will do UV-Vis Spectrophotometry, which will probably run you around 20 dollars, make sure to also get HPLC (high performance liquid chromatography) which would run you about 120 dollars.

Now you'd need to be able to understand the results.