What to Look for in a Certificate of Analysis (COA)

A Certificate of Analysis (COA) is a document issued by a laboratory — either the manufacturer's in-house lab or an independent third party — that details the quality, purity, and identity of a specific batch of peptide.

Think of it as a peptide's passport. It tells you exactly what's in the vial, how pure it is, and whether it meets the specifications claimed by the supplier. Without a valid COA, you have no objective way to verify what you're purchasing.

Every reputable peptide supplier should provide a COA for every batch they sell. If a supplier doesn't offer COAs, or only provides generic documents not tied to specific batch numbers, that's a significant red flag.

A good COA typically includes the peptide name, batch or lot number, date of analysis, the analytical methods used, and the results of each test performed.

Not all COAs are created equal. Here are the critical data points you should look for and understand:

HPLC Purity (High-Performance Liquid Chromatography) This is the most important number on any peptide COA. HPLC separates the components of a sample and measures what percentage is the target peptide vs impurities. For research-grade peptides, look for ≥95% purity — many quality suppliers achieve 98%+ on popular peptides like BPC-157 and TB-500.

Mass Spectrometry (MS) Mass spec confirms the molecular weight of the peptide, verifying that the correct molecule was synthesised. The observed molecular weight should match the theoretical molecular weight within a tight margin (typically ±1 Da). This is your identity confirmation — it proves the peptide is what it claims to be.

Amino Acid Sequence Verification Some COAs include sequencing data confirming the correct amino acid order. This is especially important for longer peptides where synthesis errors are more likely.

Endotoxin Testing (LAL Test) Endotoxins are bacterial contaminants that can cause inflammatory reactions. The Limulus Amebocyte Lysate (LAL) test measures endotoxin levels. Results should show <5 EU/mg for research-grade peptides. Not all suppliers test for endotoxins, but those who do demonstrate a higher commitment to quality.

Appearance and Solubility Basic physical descriptions — typically "white lyophilised powder" — confirm the peptide was properly processed and freeze-dried.

Learning to spot a questionable COA is just as important as knowing what a good one looks like. Watch for these warning signs:

• •No batch or lot number — A COA without a batch number could be a generic template reused across products. Every legitimate COA should reference a specific production batch.

• •No date of analysis — Without a date, you can't verify when testing was performed or whether the COA relates to your specific order.

• •Purity below 95% — While some complex peptides may have lower purity, most common research peptides should achieve ≥95%. Anything below 90% is a serious concern.

• •No laboratory name or accreditation — A COA should identify who performed the analysis. Ideally, this should be an ISO 17025 accredited lab or a named third-party facility.

• •Mass spec data missing or inconsistent — If the observed molecular weight doesn't match the expected value, the wrong peptide may have been synthesised.

• •Suspiciously perfect results — Real analytical data has minor variations. A COA showing exactly 99.99% purity across every metric may be fabricated.

• •PDF metadata inconsistencies — Check the document properties. If a COA claiming to be from 2026 has creation metadata from 2019, it may have been altered.

The gold standard for peptide quality assurance is independent third-party testing — where a supplier sends samples to an external laboratory that has no financial relationship with the manufacturer.

Why third-party testing matters: In-house testing can be accurate, but there's an inherent conflict of interest. A third-party lab has no incentive to inflate purity numbers or overlook contamination.

How to verify a third-party COA: - Check the lab name — Search for the laboratory online. Legitimate analytical labs have websites, accreditations, and verifiable addresses. - Look for accreditation numbers — ISO 17025 or GLP (Good Laboratory Practice) accreditation indicates the lab meets international quality standards. - Contact the lab — Most reputable labs will confirm whether they tested a specific batch if you provide the COA reference number. - Cross-reference batch numbers — The batch number on the COA should match the label on your product. If they don't align, ask the supplier for clarification.

Some UK and European suppliers now offer QR codes on their products that link directly to the COA for that specific batch. This is an excellent transparency practice and a strong indicator of supplier quality.

When in doubt, you can also commission your own independent testing. Several UK-based analytical laboratories offer peptide analysis services, though costs typically range from £100-300 per sample.