A freezer rebuild is rarely just a logistics exercise. Vials come out, the log is reconciled, boxes are relabelled and fresh stock arrives to fill the gaps. In the rush, the purity percentage on a certificate of analysis tends to become shorthand for quality — precise, comparable and easy to drop into a spreadsheet. It is also only half of the question a materials manager should ask before anything new goes into the rack.
Identity testing is the other half. A purity figure describes how much of a sample is accounted for by the principal peak; an identity result speaks to whether that peak is the compound the label claims. Rebuilding without both is rebuilding on an assumption.
What a Purity Percentage Measures, and What It Quietly Leaves Open
On a certificate of analysis, purity is typically derived from high-performance liquid chromatography and reported as the relative area of the principal peak. In plain terms, it describes how much of the detected signal, under one defined set of chromatographic conditions, belongs to the main component rather than to neighbouring peaks. That is genuinely useful information: it speaks to cleanliness of preparation and to the presence of detectable impurities.
It is not, however, a statement of identity. A chromatographic peak tells you that something eluted at a particular retention time and absorbed at a particular wavelength; it does not, on its own, tell you what that something is. Related structures can behave similarly in a single chromatographic system, and a mislabelled or substituted material can still produce a tidy, dominant peak with an impressive percentage beside it. The number shows that a sample is largely one thing — not that it is the right thing.
Purity percentages are also method-dependent, which makes them slippery across time. Column chemistry, mobile-phase composition, gradient, detection wavelength and integration parameters all influence the reported figure. A value lifted from an old certificate, a product listing or a marketing badge is therefore no substitute for the document that accompanies the specific batch in hand. Research Sciences publishes headline lines such as “≥99% Verified Purity” and “UK Research Materials Over 99.1% Purity”; these are the shop’s current published figures and should be reconfirmed on the live site, with the exact purity for any given vial read from its batch CoA.
Nor does a purity percentage span every analytical dimension. The About page describes the testing framework as full-spectrum, covering purity, identity, heavy metals and endotoxin evaluation of submitted samples, and site blog posts discuss HPLC alongside elemental screening by ICP-MS and endotoxin testing. Those are separate questions with separate answers, which is why one percentage should never stand in for the whole document.
Reading Identity and Purity Together on the Batch CoA
Identity testing is the counterweight. Where purity asks “how much”, identity asks “which compound” — and that is the question a freezer rebuild actually turns on. Once vials are split, moved between sites or relabelled into working stocks, the label becomes the only remaining claim about contents. If that claim is unverified, no downstream purity figure repairs the experiment.
The FAQs state that every compound is supplied with a CoA covering both purity and identity by HPLC, that materials are produced by international partners using solid-phase peptide synthesis and independently tested by HPLC, and that final verification and quality checks take place in the UK before release. The homepage lists “CoAs Janoshik Analytical Reports”. The instruction that follows is simple: open the document attached to the specific batch and read the identity section alongside the purity section, rather than relying on a listing summary or a remembered figure from an earlier order.
Vial labelling supports that check. Labels combine a SKU code with an expiry date — the shop cites the format BPC10-03/27 — and the reference links to the corresponding CoA, so it should be quoted whenever documentation is queried. Two caveats belong in a standard operating procedure. Vial cap colour and other packaging details may vary between deliveries and are not indicators of identity, analytical quality or manufacturing origin; stock should never be sorted on that basis. And restocked products may carry the same Internal Test Reference as earlier stock. An ITR links to associated sample testing reports, but it does not confirm that separate deliveries came from the same production lot or received separate independent testing. Treat a matching ITR as a pointer to reports, not as proof of lot-level continuity.
Read together, on the same batch CoA, purity and identity give a materials manager something a spreadsheet column cannot: a defensible statement about what is in the vial and how well characterised it is.
Rebuilding the Freezer Inventory Without Losing the Paper Trail
With the analytical logic settled, the rebuild becomes a documentation exercise as much as a storage one. Incoming vials should be quarantined until the label reference has been matched to the correct CoA and both the identity and purity sections have been sighted and recorded. Shelving should be organised by batch rather than by product name alone, so stock from different deliveries is not silently merged in one box, and expiry dates should be transcribed into the inventory record at the point of entry.
Storage discipline follows the shop’s published handling guidance: lyophilised materials at –20°C or below, sealed with desiccant, protected from moisture, heat and light, with repeated freeze–thaw cycles avoided. Reconstituted material is less stable and should be held at 2–8°C for short-term laboratory use within an in-vitro workflow. The FAQs note that all peptides contain trace amounts of mannitol as an excipient, included to support lyophilisation, solubility and stability — worth flagging in the SOP so a legitimate formulation component is not later mistaken for an anomaly. The shop also does not supply blended peptides, recommending that compounds be bought individually and combined only within a controlled experimental design, which keeps each batch’s identity record clean.
Catalogue review usually runs alongside the same process, and it is a good moment to confirm that listing, label and certificate agree. Anyone cross-referencing product pages before a restock — whether for the lyophilised peptides listed as Uk peptides or for supporting items such as storage containers and 10ml mixing water — should open the batch CoA before committing shelf space, and reconfirm current published wording on the live site rather than a cached page from a previous rebuild.
Two compliance points belong in the same conversation. All materials are supplied strictly for controlled laboratory and analytical research, labelled “For Research Use Only – Not for Human Consumption” in line with the shop’s stated position, and are not for human or veterinary use, consumption, administration or clinical application. The purchaser remains responsible for lawful use, safe handling, storage, disposal and compliance with COSHH and laboratory safety standards. A reconstitution calculator may be used to work out diluent volumes and concentrations for an in-vitro assay; it is a laboratory aid only and never a basis for dosing.
Documentation checked at the point of receipt takes minutes; documentation reconstructed once vials are spread across a building can take days, and sometimes cannot be reconstructed at all. Keep the label reference, the CoA and the storage record together, and the purity percentage becomes what it was always meant to be: one line of evidence, sitting beside the identity result that gives it meaning.
Dhaka-born cultural economist now anchored in Oslo. Leila reviews global streaming hits, maps gig-economy trends, and profiles women-led cooperatives with equal rigor. She photographs northern lights on her smartphone (professional pride) and is learning Norwegian by lip-syncing to 90s pop.
