Peptide testing in the UK: how to read a certificate of analysis

What a certificate of analysis is

A certificate of analysis (COA) is a laboratory's record of the tests it ran on one sample and the results it got. This guide to peptide testing in the UK explains what the tests can show, how to check a report from a UK or overseas laboratory, and how to tell whether a report belongs to the product it comes with. It uses the reports on our peptide lab reports and certificates of analysis page as worked examples. Peptide testing usually answers four separate questions, and no single test answers all four.

HPLC peptide purity: what the percentage means

Peptide purity testing usually relies on high-performance liquid chromatography (HPLC), which pushes a dissolved sample through a packed column. Different molecules leave the column at different times, and a detector draws each one as a peak. Purity is usually worked out by area normalisation: the area of the main peak divided by the total area of all the peaks recorded, as a percentage.

So an HPLC purity of 99.5% means that other detected peaks made up 0.5% of the total peak area under that method. The figure has limits:

• It only counts what the detector can see. Water, salts and counter-ions such as acetate or trifluoroacetate (TFA) do not appear as peptide peaks, so high purity is not the same as high peptide content.
• Impurities that leave the column with the main compound hide inside its peak. European medicines guidance warns about these co-eluting impurities, and notes that diastereomers (versions of the peptide in which some amino acids are in their mirror-image form) may need methods of their own.

For scale, the European Medicines Agency's guideline on synthetic peptides, in force since 1 June 2026, applies the European Pharmacopoeia thresholds for medicines: peptide-related impurities are reported above 0.1%, identified above 0.5% and supported by safety data (qualified) above 1.0%. Typical impurities are near-copies of the target, with an amino acid missing, cut short or added (see how synthetic peptides are made). These thresholds are set for medicines. The GHK-Cu report we publish is not a medicines-release report: it gives one purity figure and lists no individual impurities.

Mass spectrometry: checking peptide identity

Mass spectrometry weighs molecules, and the laboratory compares the observed mass with the mass expected from the formula. For GHK, the tripeptide part of GHK-Cu, PubChem gives the formula C14H24N6O4 and a monoisotopic mass (the mass when every atom is its most common isotope) of about 340.19. In positive-ion mode, commonly used for peptides, the molecule picks up a proton, so a matching signal appears near a mass-to-charge ratio (m/z) of 341.19.

A match is good evidence that the main component is what the label says, but not proof of everything. Molecules with the same atoms in a different order, or with mirror-image amino acids, can share a mass, and mass spectrometry alone says little about how much of the sample is the target. The EMA guideline therefore recommends at least two orthogonal (differently based) identification methods for peptide medicines and, when the structure is characterised, expects representative mass spectra with tables of theoretical against observed masses. On a research report, identity is often one line: a tick, ‘confirmed’ or an observed mass.

Content: how much is actually there

A content test, also called an assay or quantity test, measures how much of the compound is in the sample, usually against a reference standard. It answers the question purity cannot: does an item labelled 100mg contain about 100mg? Results may be given per container in milligrams, or as a concentration in milligrams per millilitre (mg/mL). For medicines, the EMA guideline expects assay limits measured by liquid chromatography to be expressed on a counter-ion-free, water-free basis, unless otherwise justified.

The GHK-Cu 100mg report we publish gives a GHK-Cu concentration of 39.18 mg/mL, split into GHK at 32.54 mg/mL and copper at 6.64 mg/mL, and the two parts add up to the total. A concentration only converts into a total amount once the filled volume is known, and the report does not state one.

Blends and bundles: one result per component

A blend pen holds more than one compound in one solution, so a useful report identifies and measures each one separately, for example by its own chromatography peak and measured mass. A single purity figure cannot show how a labelled total is divided between the compounds. A report for a single-compound pen does not carry over to a blend, or the other way round, and a bundle of separate pens needs a report for each pen (see single-compound, blend and bundle pens). On 22 October 2026 our library had no published report for either of the catalogue's two blend pens, BPC-157 + TB-500 (40mg) and BPC-157 + TB-500 + GHK-Cu (70mg), or for the BPC-157 + TB-500 bundle.

Endotoxin, sterility and other contaminants

Endotoxins are fever-causing (pyrogenic) substances, such as lipopolysaccharide, found in the cell wall of bacteria; that is the definition in the US Food and Drug Administration's (FDA) guidance on aseptic processing. The same guidance notes that sterilising-grade filters and moist-heat (steam) sterilisation have not been shown to remove endotoxin, so a sterile sample can still contain it, and the two are tested separately. The FDA's guidance on pyrogen and endotoxin testing (second edition, March 2026) refers to the gel-clot, photometric and kinetic methods in the US Pharmacopeia. It notes that the sample itself can interfere with these assays, and that pyrogens other than endotoxins may call for a different test.

A sterility test asks whether anything grows when the sample is placed in culture media. Its limit is statistical: in the FDA's aseptic processing guidance, a 10,000-unit lot with 0.1% of units contaminated, tested by sampling 20 units, has a 98% chance of passing. A pass shows that the tested units grew nothing; it cannot vouch for every unit.

Metals and solvents need tests of their own. Belgian public-health scientists who screened the ten falsified peptide products most often found on their market, bought from three suspected illegal online pharmacies, found widely varying amounts per unit, purity between 5% and 75% for the cysteine-containing peptides, raised arsenic in several samples and lead in one. A purity-only report would show none of the metals.

Independent laboratory or supplier-issued report?

A supplier-issued COA comes from the maker or seller. It can be accurate, but it asks the reader to trust the party with an interest in the result. A third-party report comes from a separate laboratory, ideally one that lets anyone check it online.

Independence has a second layer: who chose the sample. The GHK-Cu and NAD+ reports we publish both name the pen maker as client and manufacturer. The laboratory is independent of the seller, but the maker commissioned the test, and the record does not say how the sample was chosen. A unit bought from stock says more about what is on the shelf.

Accreditation is the other check. UKAS, the UK's national accreditation body, assesses testing laboratories against ISO/IEC 17025, which covers staff competence, test methods and equipment. A laboratory is accredited only for the activities listed on its schedule, and UKAS says ISO 9001 certification is not an alternative. The GHK-Cu and NAD+ reports we publish do not state an accreditation, so we do not claim one.

How to check that a report matches the product

Work through these checks before relying on any certificate. The GHK-Cu 100mg report we publish (Janoshik task #224435) is the example.

1. Product and strength. The sample name should match the compound and labelled content; our example names the sample ‘KLIK-GHK 100MG’, the maker's label name for the GHK-Cu 100mg pen.
2. Batch or lot number. Compare it with the packaging; our example gives batch 07/2026. The NAD+ report we publish carries the same reference, so here it appears to mark a production period rather than a unique lot for one product. A report with no batch, or ‘N/A’, cannot be tied to any stock.
3. Dates. Our example shows testing ordered on 17 August, the sample received on 28 August and the analysis done on 31 August 2026. Results describe the sample at that point, and later storage matters too (see how to store peptide pens).
4. Sample photo. Our example shows a cartridge of blue liquid marked G100 rather than a retail label (see how peptide pens are built and labelled), so only the sample name and batch reference connect the report to stock, and that connection is loose.
5. Verification key. Our example prints a unique key (which also ends the record's web address), a QR code and the instruction to verify the test at www.janoshik.com/verify/. Make sure the record opens on the laboratory's own domain (type the address if a report reached you as a PDF or screenshot) and shows the same sample, batch and results.
6. Tests performed. The ‘tests requested’ line shows what was measured, and so what was not; our example reads ‘GHK (or GHK-Cu) analysis’. It does not name its analytical methods, and the laboratory can be asked which it used.

Red flags on a certificate of analysis

• A generic report that names a compound but no strength, format or batch, or one report offered for several products or batches.
• No laboratory name or contact details, or a laboratory you cannot find independently.
• A verification key that does not resolve on the laboratory's own website, or resolves to a different sample.
• Signs of editing: mismatched fonts, misaligned numbers, a cropped header or a blurred key.
• A purity of exactly 100%, results with no units, or dates that do not fit.

If anything does not match, ask the seller and the laboratory; a genuine laboratory can usually confirm whether a report exists.

Peptide testing in the UK: choosing a laboratory

Commissioning a test, rather than relying on a supplier's report, starts with the laboratory. UKAS lists every organisation it accredits to ISO/IEC 17025 for testing on its website, so a UK laboratory's claim can be checked there, together with the schedule of activities its accreditation covers.

A laboratory does not have to be in the UK. UKAS, a member of the International Laboratory Accreditation Cooperation (ILAC), explains that under mutual recognition arrangements such as the EA MLA and the ILAC MRA, reports from laboratories accredited by a signatory body should be accepted as technically equivalent in the other signatories' countries. What matters is that the test required is on the laboratory's schedule.

Before sending a sample, ask the laboratory:

• Which tests it runs on peptides (purity, identity, content, endotoxin, sterility, metals) and which methods it uses.
• How much sample it needs, and whether the sample is used up.
• How long results take and what each test costs, as a written quote.
• Whether the report will name the methods and the batch, and can be verified on the laboratory's own website.
• Whether those tests are covered by its accreditation.

We do not recommend a particular laboratory.

How we publish laboratory reports

Our certificates page lists the Janoshik reports we have matched to an exact product and strength (last checked 5 October 2026), each linked to the original record on the laboratory's website. Not every product has one. The two used as examples in this guide are:

• GHK-Cu 100mg (Janoshik task #224435): a purity of 99.770%, with the GHK-Cu, GHK and copper concentrations described above.
• NAD+ (Janoshik task #224434): one 500mg sample (‘KLIKNAD+ 500MG’; the photo shows a cartridge of clear liquid marked N500) was tested for identity and amount. The report gives a concentration of 244.40 mg/mL, notes that the sample was tested twice and gives no purity percentage, so our library shows none. The NAD+ product is a pack of two 500mg pens, and the report covers the single 500mg sample tested. NAD+ is a coenzyme rather than a peptide, but the same reading rules apply.

A report covers the tested sample only. It does not verify every batch in stock, and current-stock batch matching has not been independently verified for our catalogue. Compare the batch on the packaging with the report. If it differs, or a product has no report, contact us for the records for that batch. Neither the GHK-Cu nor the NAD+ product is a licensed medicine, and no laboratory report makes a product suitable for human or veterinary use; everything sold here is for laboratory research only.