A certificate of analysis (COA) is the document that records the analytical results for one specific lot of a material. If you buy research peptides, knowing how to read one quickly tells you four things: who produced it, which lot it covers, what was measured, and whether each result met its limit. This guide walks through the parts you'll see on a typical peptide COA, using the layout of the certificates we publish as the example.
Start with who issued it
Before you look at any numbers, check who produced the document and when. At Vitaluxe Labs, the COAs we publish are Manufacturer COAs (SENOBIO), listed by product, where available, on our COAs page. Our vial labels don't currently show a lot number, so a certificate may not be for the lot you receive. They are the manufacturer's own records of the lots they tested, and we describe them that way so you can judge the data for yourself.
Whenever you compare certificates from any supplier, look for the name of the organisation that issued the report, the report date, and the lot it relates to. A certificate tells you what its issuer measured. It doesn't tell you what anyone else measured.
The header: identity details
The top section of a peptide COA usually lists:
- Product name: the compound as the manufacturer names it.
- Lot (batch) number: the reference that ties the certificate to one production lot.
- Sequence and modifications: for example "Gly-His-Lys (Cu2+ chelated)". Check this against the structure you expect.
- Storage conditions: the manufacturer's stated conditions for the dry material.
- Report date: when the analysis was reported.
The lot number matters most. Whenever you compare certificates, check which lot each one covers before you compare any results, because a COA says nothing about any other lot. A certificate relates to the lot printed on it. Our vial labels don't currently show a lot number, so we can't yet confirm which lot a vial came from.
Specification versus result
The main table has three columns: the test item, the specification and the result.
- The specification is the acceptance limit set before testing, for example "purity greater than 98%" or "molecular weight 403.8 ± 1.0 Da".
- The result is what was actually measured on that lot.
- "Conforms" means the result met a descriptive specification, such as appearance or retention time, where there isn't a single number to report.
A result only means something next to its specification and its method.
Here are three rows from a GHK-Cu manufacturer certificate. Each row gives a test, the limit it had to meet and, on the real certificate, the measured result for that lot.
| Test item | Specification |
|---|---|
| Appearance | Blue to blue-violet lyophilised powder |
| Molecular weight (MS) | 403.8 ± 1.0 Da |
| Purity (HPLC) | >98% |
A certificate's results apply to its own lot only. They aren't a statement about other lots or about any particular vial.
Every manufacturer certificate we hold is listed by lot number on our COAs page, so you can read the real results for each lot there.
What HPLC shows
High-performance liquid chromatography (HPLC) separates a sample into its components as it passes through a column. A detector, usually UV, records each component as a peak. Purity is normally reported as the main peak's share of the total detected peak area, as a percentage.
Two related rows are worth knowing:
- Retention time: when the main peak came off the column, compared with a reference standard. "Conforms" means it appeared within the stated window.
- Related substances: limits on individual and total impurities.
HPLC purity has limits. It only counts what the detector can see, so it doesn't measure water or counter-ions such as acetate. That means an HPLC purity figure isn't the same thing as the amount of peptide by weight in the vial.
What mass spectrometry shows
Mass spectrometry (MS) measures the mass-to-charge ratio of ions made from the sample. On a COA it supports identity: the specification gives the expected molecular weight with a tolerance, and the result shows what was observed.
A result can sit slightly above or below the calculated figure. That's partly because instruments often detect an ion with a proton added or removed, and partly because of rounding. MS confirms the mass is right. It doesn't measure purity on its own, and it can't always tell apart two structures that have the same mass.
Other rows you may see
Depending on the compound, certificates may also list residual solvents (such as acetic acid or TFA, in ppm), heavy metals and microbial counts. The GHK-Cu certificate also has copper content and free copper ion rows. "N.D." means not detected at the method's limit. Read every row the same way: specification, result and units.
A quick checklist
- Who issued the certificate, and when?
- Do the product name and sequence match what you expect?
- Which lot does the certificate cover, and is it the lot you're interested in?
- Is every result within its specification, with consistent units?
- Are the methods named (HPLC, MS)?
- Remember what the certificate can't tell you: it doesn't describe other lots, and it isn't a guide to handling or use. We don't provide preparation or usage instructions of any kind.
Finding our certificates
Go to our COAs page and find the row by product name or lot number. Each row shows the product, lot number, COA date and the HPLC result printed on that certificate, with a link to the PDF. Product pages link to the manufacturer certificate we hold for that product and show which lot it covers. Where we don't hold a certificate for a product, its product page says so.
Manufacturer storage conditions, where we hold them, are quoted on each product page. The full range is in Research Peptides UK, including BPC-157 and GHK-Cu.
For laboratory research use only. Not for human or veterinary use. 18+
