How APIs are Tested: Assay, Purity & Impurity Profiling
API quality evaluation starts with analytical testing. Buyers commonly review assay, purity, impurity profile, identification, residual solvents, moisture, heavy metals, and other specification parameters before procurement.
Assay
Assay indicates the amount of active substance present in the API. It is one of the most important parameters in COA review and specification comparison.
Purity and impurities
Purity shows how clean the API is, while impurity profiling identifies related substances or degradation products. Buyers should compare impurity limits with required pharmacopoeial or in-house specification.
Other common tests
API testing may include identification, appearance, loss on drying, water content, residual solvents, particle size, sulphated ash, specific rotation, pH, and microbiological limits depending on the product.
Buyer recommendation
Always review the COA against the required specification and destination-market expectation. Testing requirements differ product-wise.
