A lot number (or batch number) is the identifier assigned to one production run of a peptide. Every analytical claim attaches to it. Purity, identity, appearance and water content are properties of a batch, not of a product name, so a certificate without a matching lot number describes material you do not have.
How to use it
Read the lot from the vial label, then confirm the same string appears on the certificate of analysis supplied with the order and on any third-party report. Record the lot alongside your experimental data. If results shift unexpectedly between preparations, the lot is the first variable to check — a new batch means a new impurity profile and possibly a different counter-ion ratio and net peptide content.
Why it matters
Lot tracking is the difference between traceable and anecdotal work. It also underpins recalls and complaints: without a lot, a supplier cannot isolate which vials share a problem, and an out-of-specification observation cannot be tied back to a manufacturing event. Reproducibility across published research depends on the same discipline.
Related terms
purity · HPLC · research use only. See how to read a peptide COA and the vendor checklist.