Reference standard (revision 6)
Old revision·17:54, 20 Aug 2024·LotTraceLuka
| Reference standard | |
|---|---|
| Primary standard | Characterised without reference to another standard |
| Secondary standard | Qualified against a primary standard |
| Carries | Assigned content, identity data, expiry, storage conditions |
| Topic infobox · conventions | |
A reference standard is a material of established identity and assigned content used to calibrate an analytical method. Without one, a chromatographic determination yields a normalised proportion — area percent — but not a quantity, and a retention time yields a comparison but not an identification.[1]
Standards are described as primary or secondary. A primary standard is characterised by absolute methods without reference to another standard of the same substance; a secondary standard is qualified against a primary one and is what most laboratories actually use. Pharmacopoeial standards are the archetype of the first category.[1]
For compounds without a marketed product there is generally no compendial standard, because compendial standards follow monographs and monographs follow approval. This is a real and under-acknowledged limitation for investigational compounds such as retatrutide and survodutide.[2]
What a standard supplies
[edit]A reference standard carries more than the substance. Its accompanying documentation states the assigned content — the mass fraction that is the substance of interest, which is not 100% — the identity data supporting the assignment, the storage conditions, and a retest or expiry date.[1]
Assigned content is the field most often misunderstood. A standard is not pure in the colloquial sense; it is a material whose composition has been determined, so that a known mass of it contains a known mass of analyte. Calibrating against a standard while ignoring its assigned content introduces a systematic error of exactly the magnitude of the water and counterion it contains — for a trifluoroacetate-salted peptide, often 15–30%.