Lot numbers and lot discipline

A lot is a quantity of material produced and handled as one unit, so that every vial filled from it is expected to be the same. The lot number is the label for that unit. When an analytical laboratory tests a sample drawn from the lot, its result is taken to describe the whole lot — which is only reasonable if the lot really was handled as one thing from start to finish.

Material here is released by lot, and each lot carries its own certificate of analysis. The certificate names the compound, the lot number, the assay date, the analytical method and the measured purity. There is no such thing as a certificate for a compound in general; there are only certificates for lots. If you have two vials of the same compound with different lot numbers, you should have two certificates, and they may show different figures. That is expected, and it is the point.

The moment two lots are combined after testing, the certificates for both stop describing anything real. The blend has a purity that neither certificate measured, and there is no number on the vial that maps to a single assay any more. So nothing is blended between lots after testing. The number printed on your vial always corresponds to exactly one analysis of exactly one lot. It is a simple rule, and it is what makes reading a certificate mean something.

Three practical habits make the lot number work for you:

• Match it on arrival. Find the lot number on the vial and the lot number on the certificate. They must be identical. If they are not, contact support before doing anything else.
• Record it. Write the lot number into your inventory and your notebook the day the parcel arrives, alongside the date received. When a result needs to be traced back to the material that produced it, this is the line that does it — see a lab notebook and chain of custody for reference materials.
• Quote it. Any question to support about a certificate, a replacement or a return goes faster with the lot number in the first message.

If you need the certificate for a lot you already have — the original was misfiled, a reviewer wants a copy, a new team member is checking the shelf — contact support with the lot number and it will be sent the same business day. There is no charge and no need to have the order number, though having it helps.

Ordering several vials of the same compound raises a practical question: are they all from the same lot? Usually, but not necessarily. When a lot runs low, an order may be filled from two lots, and each vial then carries its own lot number and maps to its own certificate. The receiving check should therefore match each vial's lot number to a certificate individually, rather than reading one vial and assuming the rest match — see inspecting a vial on arrival. Wholesale accounts, which order in quantity as a matter of course, have certificates attached to every invoice for this reason, so a shipment drawn from two lots arrives with two certificates. The quality page describes the standard; the receiving check is where a laboratory applies it.

A lot number identifies material; it does not describe its condition today. Everything after the assay date — storage, handling, time — is the researcher's responsibility, and the storage conditions to follow are stated on the certificate. All material is supplied for in-vitro laboratory research only; see research use only.