How to Read a Peptide Certificate of Analysis (COA): A Researcher’s Complete Guide

A Certificate of Analysis is the single most important document in peptide research. If you can’t read one, you can’t verify what you’re actually working with. This guide breaks down every section so you can evaluate purity, identity, and quality with confidence.

What Is a Certificate of Analysis?

A COA is a quality control document issued by an analytical laboratory — ideally a third party independent of the manufacturer. It confirms that a specific batch has been tested and meets defined specifications.

The 5 Key Sections of a Peptide COA

1. Product Identification

• Peptide name and sequence — amino acid chain confirmation
• Molecular weight and formula — should match known values (e.g., BPC-157 = ~1419.53 g/mol)
• CAS number — universal chemical identifier
• Lot/batch number — must match your vial’s label exactly

2. HPLC Purity Analysis

High-Performance Liquid Chromatography — the gold standard for measuring peptide purity:

• Purity percentage — research-grade should be ≥98%; below 95% is substandard
• Retention time — must match expected value for the compound
• Chromatogram — a single sharp dominant peak = high purity; multiple peaks = impurities
• Method details — column type, mobile phase, gradient, detection wavelength (usually UV 220nm)

3. Mass Spectrometry (MS) Confirmation

HPLC tells you how pure. Mass spectrometry tells you what it actually is:

• Observed molecular weight — must match theoretical weight within ±1 Da
• MS spectrum — dominant peak should correspond to expected [M+H]+ or [M+2H]2+ ion

4. Amino Acid Analysis (Optional but Valuable)

Breaks the peptide into constituent amino acids and measures each quantity — confirms the correct sequence was synthesized. Especially valuable for longer or complex peptides.

5. Endotoxin and Sterility Testing

• LAL test endotoxin level — should be below 0.5 EU/mg (Endotoxin Units per milligram)
• Sterility confirmation — no bacterial or fungal contamination
• Appearance — typically “white to off-white lyophilized powder”

Red Flags on a COA

Warning signs that suggest unreliable analytical data:

• No batch/lot number — generic COA not tied to specific batch = meaningless
• No laboratory name or accreditation — legitimate labs are ISO 17025 accredited
• Missing chromatogram or spectrum — numbers without graphical data can’t be verified
• Suspiciously perfect numbers — every batch at exactly 99.9% is statistically unlikely
• In-house testing only — the COA that matters is from an independent third party
• Outdated testing — peptides degrade; old COAs may not reflect current quality

How Blank Peptides Approaches COAs

Every product ships with a batch-specific third-party COA including HPLC purity analysis, mass spectrometry identity confirmation, and endotoxin testing. We publish COA data on each product page so researchers can evaluate quality before purchasing.