The two primary types of impurity often referenced, especially in pharmaceutical contexts, are organic and inorganic impurities.
Organic Impurities
Organic impurities are typically process- or drug-related. This means they can arise from the manufacturing process of a drug or be related to the drug's structure and degradation. Examples include:
- Starting materials
- Intermediates generated during synthesis
- By-products of the reaction
- Degradation products that form over time.
Inorganic Impurities
Inorganic impurities often originate from the manufacturing process as well. Examples include:
- Reagents used in synthesis
- Catalysts
- Filter aids
- Inorganic salts
- Heavy metals
It's important to note that while "residual solvents" are a critical type of impurity to control, they are often categorized separately, rather than being considered a type of inorganic or organic impurity. They are solvents used in the manufacturing process that remain in the final product. Therefore, while organic and inorganic impurities are a key distinction, the broader context of impurity control requires considering residual solvents as well.
