Why COA batch matching matters

A Certificate of Analysis describes one batch of material. If the batch number on the certificate is not the batch number on the vial in your hand, the certificate tells you about something else. This sounds obvious, and yet a substantial share of the COAs supplied with UK research peptides either carry no batch number, carry a batch number that appears on no vial, or are reused across batches for months. This note explains what batch matching means, how to check it, and why Alphex prints the batch number on every label. All Alphex products are for laboratory and in-vitro research only.

What a batch is

A batch (or lot) is a quantity of peptide made in one synthesis and purification run, lyophilised and vialled together, and tested as a unit. Every vial from that batch is, within the limits of the fill process, the same material, and one set of tests characterises all of them. The next synthesis run is a new batch: different crude profile, different purification, different test results, different number. Batch identity is what makes a COA meaningful; the tests were done on that material.

What matching means in practice

1. The vial label carries a batch number.
2. The COA header carries the same number.
3. The chromatogram and mass spectrum on the COA carry it too, as the sample identifier the laboratory used.
4. The test date is after the synthesis date and reasonably close to it, and before the vial reached you.

All four should agree. Two out of four is a document assembled from parts.

Why it matters

• The certificate is only evidence for its own batch. A COA showing 99.4% purity for batch A says nothing about batch B, however similar the label looks.
• Traceability of results. If an experiment behaves unexpectedly six months later, the batch number on the vial, carried onto the aliquot labels and the lab book, lets you retrieve the exact chromatogram and mass spectrum for that material and compare it to a fresh batch. Without it, the question "was it the peptide?" cannot be answered. See aliquoting and record keeping.
• Accountability. If independent testing finds a batch below specification, the batch number is what a supplier's replacement or refund policy hangs on. A supplier that does not batch-number its vials cannot honour such a policy in any verifiable way. See the purity guarantee.
• Detecting reuse. The commonest COA problem in the market is not fabrication but recycling: one genuine certificate from one good batch, supplied with every subsequent batch. Batch numbers and dates are what expose it.

How Alphex handles it

Every vial label carries the batch number. Every COA is issued against that number, with the chromatogram and mass spectrum labelled with it and the testing laboratory named. When a new batch is vialled, a new COA is issued and the previous one is retired from what we send out. You can request the certificate for the batch currently in stock before ordering, and it will match the vial you receive; if stock turns over between your request and dispatch, we send the new certificate with the order. See how to request a COA before ordering and the Alphex batch numbering system.

Checking a supplier

• Ask for the COA for the batch currently in stock, not "a COA".
• When the vial arrives, compare the number on the label with the certificate.
• Order again a few months later and check whether the certificate changed. If a supplier's COA has had the same batch number for a year, they are either holding a very large batch or reusing a document.

The wider checks are in how to read a research peptide COA.

Alphex research peptides are supplied for laboratory and in-vitro research by qualified researchers only. They are not authorised for human or veterinary use.

Research use only. Alphex products are supplied exclusively for laboratory and in-vitro research by qualified researchers. They are not authorised for human or veterinary use, and nothing in this note is advice on any such use.

Published 23 April 2026. Alphex reviews research notes when the testing method, the catalogue or UK guidance changes.

Alphex Research Team

Alphex Limited, UK research peptide supplier

The Alphex research team writes and maintains these notes for UK laboratories buying research peptides. Every batch Alphex lists is verified by reverse-phase HPLC with a batch-matched Certificate of Analysis. Content covers laboratory and in-vitro research only.