ABSTRACT
The European Pharmacopoeias general Chapter 2.4 Limit tests include 27 monographs, each describing a test developed to assure that any unintended content of a well-defined element or compound is below some critical limit. The reason for limiting the element or compound in question varies from monograph to monograph. Some monographs reveal a residual content of toxic substances, like arsenic and heavy metals, and the reason for limiting their presence is obvious. Others, however, cover clearly harmless elements like chlorides or the alkali metals. In those cases, the reason for limiting their presence is one of general product quality. A well-produced, active pharmaceutical ingredient or excipient need not have a residual content of, for example, inorganic salts used during synthesis. When present, however, they reveal a product of low general quality.
