What is the Inspectorate’s position on the use of secondary reference standards (RS) and what are the conditions for the use of secondary reference standards?

While the Inspectorate recommends the use of the official standards for the analysis of compendia
articles, the use of a secondary RS is acceptable if each lot’s suitability is determined prior to use by
comparison against the current official reference standard and each lot is requalified periodically in
accordance with a written protocol. The protocol should clearly address the receipt, storage, handling and use
of primary reference standards, the purification of secondary standards, and their qualification against official
reference standards.