How to check a research peptide supplier

This page names no suppliers and recommends none. It lists the checks that can be run on any research peptide shop from the outside, without an account, without an enquiry and before a first order. At the end it runs the same checks on UKPeps, including the places where UKPeps comes off badly. Everything mentioned is supplied strictly for in vitro laboratory research and is not for human or veterinary use.

The question everything else depends on

There is exactly one check the others hang from: can the vial in your hand be traced back to a test report? That requires the lot number on the label to match the lot number in the report. If they do not match, or if one of them is missing, the report says nothing about that vial, however good it looks. Every other check on this page is a variation of that one question.

Six entries a certificate must carry

Substance. A trade name alone is not enough, because the same compound travels under several.
Lot number. This ties the report to one production run. Without it the report applies to none.
Test method. A percentage without a method is not a statement; two laboratories can measure the same lot and report different figures.
Measured value. The result of the measurement, not the seller's promise.
Date of analysis. Shows whether the report belongs to the lot you are buying or to another year.
Testing laboratory. Names who measured. "Tested in house" is not an independent statement.

Lot-specific or sample document

The common failure is not a missing certificate, it is the sample document: a single, unchanged PDF per substance. It proves something was measured once. About the vial in the parcel it proves nothing.

Two minutes settle it. Open the reports for two different products and compare lot number and date of analysis. If both lot numbers are identical, they do not belong to two lots. If the date is years old while the shop ships continuously, it is not the date of the goods being shipped.

Readable without an account

A report that arrives only after registration, only on request, or only with the delivery cannot be checked at the one moment when checking would change the decision, which is before buying. The question is not whether a supplier has certificates, but whether they are shown without anything being handed over first.

Specification and measured value are two numbers

A specification is a promise made in advance, such as "at least 98%". UKPeps states none. A measured value is the result for one specific lot. Both can be true and far apart, and a page that merges them into one number blurs the difference.

From that follows a check almost nobody runs. If the published measured value always lands exactly on or just above the promise, for every lot, that is not evidence of quality. It suggests the figure was copied from the specification. Real measurement series scatter.

The method belongs with the number

Which column, which gradient, which detection wavelength: the result depends on all of them. That is why the method belongs on the report, and why it belongs stated per laboratory rather than blanket for a whole register. Where a shop page carries a single percentage for an entire catalogue, that percentage describes no measurement.

Purity and identity are two questions

HPLC answers how clean a sample is. It does not answer whether it is the right substance. Mass spectrometry answers that second question through the molecular mass.

This is not an academic point. If a chain is missing one link, the molecule is lighter by the mass of that amino acid, and chromatography does not necessarily separate the difference cleanly. A report that gives only a purity figure leaves the identity question open.

What a certificate does not prove

Peptide content: how much of the weighed mass is actually peptide. It is determined by amino acid analysis or nitrogen content and does not appear on every report.
Loss on drying: the residual moisture, which adds to the weight and limits shelf life.
Counterion: with chemically synthesised peptides usually trifluoroacetate, which also adds to the weight.
Sterility: a lyophilised research reagent is not a sterile product, and a purity figure says nothing about it.

From the first three follows the practically most important sentence on this page: the nominal amount on the label is an upper bound for the peptide it contains, not a guarantee. Anyone who needs concentrations exactly should calculate with the peptide content from the report, where it is stated.

Looking up the CAS number

A CAS number identifies a compound unambiguously, independently of trade names. BPC-157 carries 137525-51-0, TB-500 carries 77591-33-4. Any number can be looked up in public databases such as PubChem or CAS Common Chemistry; the last digit is a check digit calculated from the others, so an invented number fails at the first lookup.

One point that is often misread: preparations of several peptides carry no CAS number of their own, because a number designates exactly one defined substance. Where a dash appears for a research blend, that is the correct entry and not a missing one. An invented number in that place would be the opposite of care.

What can be checked about the supplier itself

The legal entity in the imprint: name, registered office and company number of the legal person, verifiable in the relevant national register. A shop showing only a brand and a contact form names nobody.
Prices in the currency that is charged, so the exchange rate does not decide after the order.
The research use statement on every product page, not only in the footer. Where it shares a page with per person quantities, schedules or user reports, the page contradicts itself.
Storage and shipping without contradiction: if the product page, the delivery page and the structured data name three different warehouses, at least two of them are unmaintained.

Checklist

Certificate readable without an account.
Lot number present in the report.
Reports for two products carry different lot numbers.
Date of analysis is not years old.
Method and laboratory named in the report, not in the product copy.
Measured values scatter instead of landing exactly on the promise.
CAS number matches the public database.
Legal entity and company number in the imprint.
No statements about use in humans anywhere on the site.

How UKPeps does on the same checks

The figures come from the certificate library, not from a promise. As at 9 October 2026:

82 test reports are published in the certificate library, searchable by substance and lot number, without an account and without an order. They cover 29 substances.
Two named testing laboratories. Liquilabs s.r.o. signs 51 reports, APIGENEX s.r.o. 28 reports, and 3 reports carry both signatures. The method is stated per laboratory, not blanket for the library.
UKPeps states no general minimum purity. Of the 82 reports, 75 carry a purity figure; the values run from 92.93% to 100%. Eleven of them are below 98%.
7 reports carry no purity figure. They are the laboratory reagents, for which no purity figure applies, and two older reports in which the laboratory states identity only.
Peptide content and loss on drying are not on every report. Where they are missing, the nominal amount is the workable figure, with the limitation set out above.

Until 9 October 2026 this shop promised at least 98%. Its own library contradicted that, so the promise was dropped rather than the inconvenient figures hidden. The eleven values below 98% sit openly in the library. There is a second reason, and it weighs more than the numbers: an order carries no lot number, so the shop does not know which lot reaches you, and what it does not know it does not promise.

All reports are open to read, without an account, in the certificate library.