Definition
An unbroken sequence of temperature-controlled storage and transport that keeps a product within a set range.
A cold chain is the continuous temperature control maintained from manufacture through storage, shipping and receipt. For biological reagents, defined ranges include refrigerated (2–8 °C), frozen (−20 °C) and ultra-low (−80 °C) storage. Lyophilised peptides are generally robust for short periods at ambient temperature, so many ship without refrigeration and are moved to the freezer on arrival, whereas peptide solutions are far more sensitive. Cold-chain practice uses insulated packaging, gel packs or dry ice, and sometimes data loggers that record temperature in transit. On receipt, laboratories typically check the packaging condition, log the arrival and move material promptly to its specified storage temperature.