How to Read a Peptide Certificate of Analysis (COA)
A Certificate of Analysis is the primary quality document for research peptides. This guide explains what each section means, what acceptable results look like, and how to identify documents that have been fabricated or altered.
Updated: March 2026
What Is a Certificate of Analysis?
A Certificate of Analysis (COA) is a document issued by an analytical testing laboratory that reports the results of quality and purity tests performed on a specific batch of a chemical compound. For research peptides, a COA typically reports:
- ›The chemical identity of the peptide (confirming it is what it claims to be)
- ›Purity percentage (how much of the product is the intended compound vs. impurities)
- ›Analytical methods used to determine these results
- ›Batch or lot number linking the document to a specific production run
- ›Date of analysis and laboratory name
A COA does not guarantee a product is safe to use, does not constitute pharmaceutical testing, and does not mean the product has been approved or reviewed by any regulatory body. It is a statement from the testing lab about what was measured on a given sample.
Key Components Explained
HPLC Purity (High-Performance Liquid Chromatography)
- ›HPLC is the most common method for measuring peptide purity. The peptide sample is passed through a column under high pressure, separating components by their chemical properties.
- ›The output is a chromatogram — a graph showing peaks for each detected compound. The main peak represents your target peptide; other peaks represent impurities (truncated sequences, oxidized forms, reagent residues).
- ›Purity is calculated as: (area of target peak) ÷ (total area of all peaks) × 100.
- ›A legitimate HPLC report should include the actual chromatogram image, not just a number.
Mass Spectrometry (MS) — Identity Confirmation
- ›Mass spectrometry measures the molecular weight of compounds in the sample. This confirms whether the correct peptide is present.
- ›Each peptide has a known theoretical molecular weight. If the measured mass matches the expected mass within acceptable tolerance, identity is confirmed.
- ›MS alone does not measure purity — it only confirms identity. A sample could contain 50% of the correct peptide and pass MS identity testing.
- ›Both HPLC purity AND MS identity should be present on a complete COA. One without the other is incomplete.
Endotoxin Testing (LAL or Recombinant Factor C)
- ›Endotoxins are lipopolysaccharides from gram-negative bacteria cell walls — a common contamination in peptides produced via bacterial synthesis.
- ›Even at very small amounts, endotoxins cause fever, inflammation, and in severe cases, septic shock when injected.
- ›Endotoxin level is measured in Endotoxin Units per milligram (EU/mg) or EU/mL.
- ›Not all vendors provide endotoxin testing. Its absence on a COA is a significant concern for any injectable use.
Sterility Testing
- ›Sterility testing confirms the product does not contain viable bacteria, yeast, or fungi.
- ›This is distinct from endotoxin testing — endotoxins can be present even in a sample with no living bacteria.
- ›Sterility testing is rarely performed for research-use peptides and is primarily relevant for pharmaceutical-grade preparations.
- ›Most research peptide vendors do not provide sterility testing; this is another reason these products are classified as research-use only.
How to Spot a Fake or Inadequate COA
Fabricated or misleading COAs are a known problem in the research chemical industry. Red flags to look for:
Third-Party Testing vs. In-House Testing
Not all COAs are equivalent. The credibility of a COA depends significantly on who performed the testing:
Third-Party Testing (Preferred)
- ✓Testing performed by an independent laboratory with no financial relationship to the vendor
- ✓Results cannot be selectively reported or adjusted
- ✓Lab can be independently verified and contacted
- ✓Provides genuine quality assurance, not marketing
- ✓Some vendors list the lab name and allow customers to verify results directly
In-House Testing (Lower Assurance)
- ⚠Testing performed by the vendor's own laboratory
- ⚠Conflict of interest: vendor has financial incentive to report favorable results
- ⚠No independent verification possible
- ⚠Equipment calibration and technician competency are unverified
- ⚠Not necessarily fraudulent — some vendors invest in quality equipment — but cannot be independently confirmed
Where to Get Independent Testing
If you want to verify a peptide product independently, contract testing laboratories accept samples from individuals. The following are examples of laboratories known to offer analytical testing services — this is educational information only, not an endorsement or affiliate recommendation:
Czech Republic-based laboratory frequently used by the research chemical community. Offers HPLC and MS testing. Results are publicly posted for community submissions.
US-based contract laboratory offering HPLC, MS, and other analytical services. Accepts samples for third-party testing.
Listing of testing laboratories is for educational reference only. PeptideScholar has no financial relationship with any laboratory mentioned.
What Purity Levels Mean
HPLC purity by area percentage is the standard measure for research peptides. Here is a general interpretation framework used in the research community:
Significant impurities present. Impurities may include truncated peptide sequences, oxidized forms, or synthetic byproducts. Not suitable for any use. A reputable vendor should not sell below this threshold.
Below standard for the research peptide industry. Acceptable for some basic in vitro cell culture experiments where high purity is not critical, but below what most serious researchers require.
Standard range for research-grade peptides. Most reputable vendors target this range. Suitable for research use as described by the vendor.
High-purity research grade. Some vendors describe this as “pharmaceutical grade” — note this term is informal and does not imply FDA review. Impurities are minimal by HPLC measurement.
Note: HPLC purity by area is the most widely reported metric but has limitations. It measures relative peak areas, not absolute mass. Water content and counterion salts are typically not captured. No single purity number fully characterizes a product's suitability for any specific use.
Medical Disclaimer
This content is for informational and educational purposes only and does not constitute medical advice, diagnosis, or treatment recommendations.
Always consult a qualified healthcare provider before starting, stopping, or modifying any treatment. Do not disregard professional medical advice based on information found on this site.
No claims of therapeutic efficacy are made for substances that are not FDA-approved for the discussed indications. Research citations reflect published findings and do not imply endorsement.