Analytical results describe the sample that was tested. Connecting those results to a specific container of material is the job of the batch number, and it is the reason batch identifiers appear on labels, certificates and records.
Without a matching identifier, a certificate is a document about some material rather than a document about the material in front of you.
What a batch is
A batch is a quantity of material produced in a single run under one set of conditions, intended to be uniform throughout. Everything in a batch comes from the same synthesis, the same purification and the same processing, so a sample drawn from it is taken to represent the rest.
That assumption of uniformity is what makes testing practical. A laboratory analyses a portion of the batch and the result is taken as describing the batch, which only holds because the batch was produced as one homogeneous quantity.
Batch and lot
The two terms are often used interchangeably, and in many settings they are the same thing. Where a distinction is drawn, a lot is a defined portion of a batch: for example, one batch divided and filled into vials across several sessions may be tracked as separate lots. The practical point is that whichever term is used, it refers to a defined quantity of material with its own identifier. Batch number, lot number and batch identifier are all names for that label, and this article uses batch identifier where the distinction between the two terms does not matter.
What the identifier is for
A batch identifier exists so that a specific quantity of material can be traced through the records that describe it.
- It links material to the analytical results generated from it.
- It links material to its date of manufacture and, where stated, a retest or expiry date.
- It allows a specific quantity to be identified precisely if a question is raised later.
- It distinguishes one production run from another run of the same compound.
The last point is the one most often overlooked. Two batches of the same compound are separate material with separate results. A certificate for one batch does not describe the other, however similar the two may be.
Matching the document to the material
The first check when reading any certificate is whether the batch identifier on the document matches the identifier on the container. It sounds trivial, and it is the step that determines whether anything else on the page is relevant.
- Does the batch or lot number on the certificate match the label exactly?
- Does the compound name on the certificate match the label?
- Is the certificate the current revision, if a revision number is present?
- Does the issue date sit sensibly relative to the date of manufacture?
- Do the methods named account for each result reported?
A certificate describes one batch analysed on one date. It is not a statement about a product line, about later batches, or about material whose identifier does not appear on the document.
Retention samples and retest dates
Two further items are often tied to a batch identifier. A retention sample is a portion of the batch held back after release, so that material from the original run remains available if a question comes up once the rest has been distributed.
A retest date differs from an expiry date. An expiry date marks the end of the period the material is considered fit for its stated purpose. A retest date marks the point at which material should be re-analysed to establish its current condition rather than assumed to be unchanged. Which of the two appears, if either, depends on the material and the supplier.
What documentation covers, and what it does not
Records of this kind establish traceability: which material this is, where it came from, and what was measured on it. That is a narrower claim than it is sometimes taken for.
- Documentation records the results of the tests that were performed. It says nothing about properties that were not tested.
- A complete and well-kept record does not by itself establish that a compound is suitable for any particular purpose. It establishes what was measured, by whom, on which material.
- Testing performed by an independent laboratory is a statement about who did the analysis, not about regulatory status. What third-party testing actually means covers that distinction.
Keeping records usable
Documentation is only as useful as the link between the paperwork and the physical material. A few habits preserve that link.
- Record the batch identifier wherever results or observations are logged.
- Keep the certificate with, or clearly referenced against, the material it belongs to.
- Where a container is subdivided, carry the original batch identifier onto every label.
- Note the date material was received, which is not always the date it was manufactured.
How to read a certificate of analysis goes through the sections of the document itself. Published certificates for compounds in our catalogue are on the certificates of analysis page, where each one is filed against the product and batch it belongs to.
All compounds and research materials supplied by PepX Research are for laboratory and research use only. They are not for human consumption.