A pharmacopoeial RS is – in most cases – a primary standard specialized for one specific purpose. It should be used for the purpose(s) described in its corresponding monograph(s), and is not automatically suitable for other purposes. To service these, reference standards from other sources should be considered. This applies to both API and impurity RSs.
Secondary RSs are compared to primary standards prior to first use. The concern in the analytical community is that it is difficult to establish traceability for quantitative secondary standards to pharmacopoeial primary standards. The latter lack the uncertainty figures which would be necessary to realize a proper traceability of secondary to primary standard.
Research materials provide valuable support in early method development. However, their use as reference standards at a later stage in method validation and release testing of finished dosage forms bears risks for both patients and – from an economic standpoint – manufacturers.