TL;DR
A Certificate of Analysis is only meaningful if it comes from a named, verifiable third-party laboratory and includes three things: an HPLC purity result with method details, mass spectrometry identity confirmation, and a batch-specific lot number. Everything else — round-number purities, internal lab testing, generic reports reused across products — is a red flag. This guide walks you through every section of a real COA so you know exactly what you’re looking at.
The certificate of analysis is the single most important document in research peptide procurement. It is also the most routinely faked, misrepresented, recycled, and misunderstood document in the industry.
In a 2008 peer-reviewed quality control study published in Analytical Biochemistry (Verlaan et al.), researchers purchased synthetic peptides from commercial suppliers and subjected them to independent impurity profiling. One product was an entirely different compound. Two-thirds of the remaining peptides failed to meet the minimum quality threshold for experimental use — purity below 95% or individual impurities exceeding 1% — despite accompanying COAs that claimed otherwise.
That study is seventeen years old. The market has grown dramatically since then. The problem has not disappeared; it has scaled.
Understanding how to read a COA is not a nice-to-have skill for a research buyer. It is the only practical quality control tool available to you before product reaches your laboratory.
For research use only. Nothing in this article constitutes medical or legal advice.
Before getting into specifics, here is the minimum viable COA:
A document missing any one of these three is not a COA. It is a marketing document.
A well-structured peptide COA contains the following sections, typically in this order. Here is what each one means and what to check.
(Refer to our sample COA at canadapeptidesupply.ca/assets/sample-coa.jpg for an annotated visual.)
What you should see:
What it means: The batch number is your audit trail. Every vial in a lot should carry the same batch ID, and that ID should appear on the COA, the product label, and your purchase record. Without a real batch ID, you cannot match a product to a COA — which means the document is decorative.
What you should see:
What it means: High-Performance Liquid Chromatography separates the target peptide from all other UV-absorbing material in the sample. The purity percentage represents the target peptide’s peak area as a proportion of all detected peaks. A result of 98.5% means 98.5% of the UV-absorbing material is the compound you ordered.
ICH Q6A guidelines — the international harmonised standard for drug substance specifications, adopted by Health Canada — require that assay and purity determinations be performed using stability-indicating, validated analytical methods. For research peptides, HPLC is the standard. As the ICH Q6A document notes, identification testing should discriminate between compounds of closely related structure.
Why the chromatogram matters: A single-page COA stating “purity: 98%” without a chromatogram tells you almost nothing. The chromatogram shows you the actual peak profile. A clean, research-grade peptide should have one dominant, sharp peak. Multiple significant secondary peaks indicate impurities. A jagged baseline may indicate degradation products. Look at the graph, not just the number.
Research-grade threshold: ≥98% purity by HPLC is the standard minimum for reliable experimental use. For high-sensitivity applications (e.g., receptor binding assays, cell-based studies), ≥99% is preferred.
What you should see:
What it means: HPLC tells you how pure the sample is. Mass spectrometry tells you what the compound is. A contaminant could theoretically co-elute with the target peptide under HPLC and produce a falsely elevated purity reading. Mass spec provides identity confirmation independent of chromatographic purity.
For a peptide with theoretical mass of 1,419 Da (BPC-157, for example), the mass spec should report an observed mass within ±0.5 Da of that value. A mismatch — even a small one — indicates either a different compound or a significant structural modification.
As Waters Corporation’s 2018 application note on synthetic peptide impurity profiling demonstrates, incorporating high-resolution mass spectrometry into the analytical workflow enables accurate mass-based identification of both the API (active pharmaceutical ingredient) and co-eluting impurities that optical detection alone would miss.
What you should see:
What it means: This is the most misunderstood section of a COA — and arguably the most practically important for research.
A lyophilised peptide powder is not 100% peptide. It contains:
A nominal 5 mg vial with 85% net peptide content actually contains approximately 4.25 mg of active peptide. A supplier who reports only gross mass — without NPC — is not giving you enough information to calculate the actual amount of peptide in your experiment.
The three “purity” numbers explained:
All three numbers should be reported on a complete COA. Verified Peptides’ knowledge hub describes this distinction clearly: reviewing a COA is about confirming identity, purity, and potency — ensuring you know how much active peptide you actually have.
What you should see (if applicable to your research use):
What it means: Endotoxins are cell wall fragments from gram-negative bacteria. Even at very low concentrations, they can confound cell culture results, cause non-specific inflammatory responses in animal models, and — in human-adjacent research contexts — pose significant risk. The ICH Q6A guideline specifically identifies endotoxin testing as a required specification for parenteral drug products.
For routine in vitro research, endotoxin data may not be required. For in vivo animal studies or cell-based assays where pyrogen contamination would confound results, it is essential. For any research involving human-adjacent exposure, endotoxin certification is non-negotiable.
A clean result is typically stated as less than 1 EU/mg for research grade, or less than 0.1 EU/mL in solution.
A COA without a unique batch ID cannot be matched to a specific production lot. It may have been generated once and applied to every shipment. The batch number on your vial should match the batch number on the COA.
“99.99% purity” is not a HPLC result — it is a rounded number that no analytical instrument produces at that precision. Legitimate HPLC results look like 98.3%, 97.6%, or 99.1%. Round numbers suggest the document was created without actual analysis.
If the document does not name the testing laboratory — ideally with a physical address, contact email, and reporting analyst name — there is no third-party accountability. The supplier may have generated the document internally.
A supplier testing its own products is not independent testing. Internal quality control may have value, but it does not provide the same assurance as a third-party laboratory with no financial interest in the outcome. Look for a named external lab — one you can search, contact, and verify independently.
Each batch of each peptide should have a unique COA. A single COA with batch “GENERAL” applied to multiple products from the same supplier, or a COA where all products show the same analysis date regardless of when they were manufactured, indicates document recycling.
A legitimate COA is a PDF generated from the analytical instrument’s software or a typed laboratory report. A photograph of a computer screen displaying results — often blurry, with visible reflections or aliasing — is a reproduction of unknown provenance. The original document may have been altered between the instrument and your screen.
Most buyers do not know that you can verify a third-party COA directly. If the COA lists a laboratory name and contact information, email them with the batch ID and ask for confirmation that the analysis was performed by their facility. Legitimate analytical laboratories will confirm or deny, usually quickly. This takes five minutes and is the highest-confidence verification step available.
For Canadian suppliers, you can also check whether the listed laboratory is a recognised analytical facility — ResolveMass Laboratories, Eurofins, ALS, or similar — by searching their name independently before accepting the COA at face value.
At Canada Peptide Supply, every batch is sent to an independent, third-party analytical laboratory. We receive the COA directly from the laboratory — not through the manufacturer — which eliminates the possibility of supplier-side document modification.
Our COAs include:
Clinic operators and wholesale buyers may request full analytical reports, including raw instrument data, for any batch we carry. We provide this as standard — it is the level of transparency our audience requires.
≥98% by area is the broadly accepted minimum for research-grade material. Below that threshold, impurity content becomes significant enough to affect experimental results, particularly in receptor binding assays and cell-based studies. For applications requiring high sensitivity, ≥99% is preferred. Analytical guidance from the peptide research community consistently places ≥98% as the standard threshold.
That depends on your experimental context. 97.2% is not research-grade by standard definitions, but it may be acceptable for some pilot or exploratory work where impurity load is not critical. Understand that the 2.8% impurity fraction is unknown in composition and could include truncated sequences, oxidised residues, or synthesis by-products. Where data quality matters, use ≥98% material.
A mismatch of more than ±0.5 Da (for a peptide below ~2,000 Da) strongly suggests you do not have the correct compound. Possible causes: a different peptide sequence, a modification (acetylation, oxidation of methionine), or a degradation product. Do not use the material for research until the discrepancy is resolved. Contact your supplier.
Internal quality control testing is better than no testing, but it is not a substitute for third-party analysis. An internal COA cannot be independently verified. The supplier has a financial interest in results that are favourable. For any research application where the identity and purity of your reagent matter, require third-party documentation.
Canada Peptide Supply publishes sample COAs and our testing policy at canadapeptidesupply.ca/coa-policy/. Every product page links to the current batch COA so you can review it before you order.
Every batch we sell is accompanied by a third-party COA with HPLC chromatogram, mass spec ID, and net peptide content. View our sample COA and testing commitments.