According to ICH 3.2.S.3.2, Primary Reference Standards (PRS) and Secondary Reference Standards (SRS) are defined as follows:
PRS are purchased from pharmacopoeia sources. SRS are prepared according to the following ICH guidelines:
Characterization (UV, IR, 1H NMR, 13C NMR, MS), ICH M4Q 3.2.S.3.5 and 3.2.S.3.2.
Purity and Assay (HPLC): ICH Q7A 1.1, 12.8 and Q6A, 2.11, 3.2, and 3.3
Specification (UV, IR, HPLC): ICH: M4Q, 3.2.S.4.5