Cannabis is a unique plant in that it produces a set of chemicals called Isoprenes. Isoprenes include both "Cannabinoids" and "Terpenes". Cannabinoids are the compounds that give Cannabis its benefical medical properties. Terpenes also have beneficial properties but also give the plant its aroma and flavor.
Each Cannabis plant acts like a tiny chemical factory producing isoprenes. The plant's own DNA, Environment and how it is processed determine how much of each type of Cannabinoids and Terpenes it produces. These factors cause a wide variability in the plants composition and properties.
The only way to know the cannabinoid concentration or potency, is to do chemical testing with analyzers. The generally accepted method for testing cannabis potency is High Pressure Liquid Chromatography. Chromatography is a method of separation and measurement. But before we can do the Chromatography, we have to extract the cannabinoids from the sample. This extraction is done with solvents.
Measuring contaminents (like microbials, pesticides etc..) in Cannabis also involves separation of the contaminants from the sample. More on this topic in a later blog post.