The cheapest way is to prescreen with our presence tests. If you want more information like concentration of active ingredient you can use our quantitative (purity) tests.
Using the quantitative test without prescreening first is not the best solution because you will waste the test if there is no active ingredient inside. This is why we include for free one prescreen test. But it is the easy way and more expensive. Since the quantitative test is very easy, there are no colors to compare.
Combining our cheap prescreen tests with quantitative test is the best option if you have more testing. If you buy our power pack which comes with 40 test vials, it will cost you less than $5 per test vial compared to our cheapest $55 quantitative (purity) test.