Knowledge Base
Storage, shelf life and what a re-test date really means
A re-test date is a claim about a number, not about a chemical. Storage conditions, opening the vial, and why the freezer matters more than the label.
Resources
Knowledge Base
Background reading on reference standards as material rather than paperwork: why purity and assay are different numbers, and how storage, shelf life and re-test dates decide whether a certificate still describes what you inject.
Knowledge Base
Purity is not assay: reading HPLC figures correctly
Area percent purity and mass fraction assay answer different questions on different bases. How to read both without overstating what is in the vial.