Intermediate is a kind of material produced in the process of API, which can only be turned into API by further molecular change or refinement. Intermediates can be separated or not separated.

API is Active Pharmaceutical Ingredients. Any mixture of substances or substances intended for use in pharmaceutical manufacture. It is also an active ingredient in pharmaceuticals when used in pharmaceuticals. Such substances have pharmacological or other direct effects in the diagnosis, treatment, remission, treatment or prevention of diseases, or can affect the function and structure of the body.

From the definition, it can be seen that the intermediate is the key product of the preceding process of making API, which is different from the structure of API. In addition, pharmacopoeia is available for the detection of API, but there is no intermediate.