MIC for Determination of Elemental Impurities in Tricyclic Active Pharmaceutical Ingredients

The digestion of tricyclic APIs is a critical step within the determination of elemental impurities using ICP-MS. Studies of several digestion methods have shown that in this regard MIC digestion procedure is the most suitable digestion method.


Tricyclic antidepressants are used as active pharmaceutical ingredients to treat depression, bipolar disorder, anxiety, obsessive-compulsive disorder and other mood disorders. They are also effective as analgesics so are used to treat chronic pain and used for migraine prophylaxis.

Due to current regulatory requirements (ICH Guideline Q3D, USP <232> and <233>, as well as Ph.Eur. 5.20) the consideration of elemental impurities will be mandatory for all pharmaceutical products, drug substances (APIs) and excipients as of January 2018 at the latest. In this context a specific focus is set on Cd, Pb, As and Hg, the so called "big four". Due to their high toxicological relevancy the regulatories stated the lowest permitted daily exposure values (PDE) for these elements.

USP <233> states closed vessel digestion within the sample preparation section therefore conventional microwave-assisted digestion (MW) was used as a first choice. 

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