← Research Blog

How to Read a Peptide Certificate of Analysis (COA)

A Certificate of Analysis is the single most important document when evaluating a research peptide. It tells you what's actually in the vial — not what the marketing says, not what the website claims, but what independent laboratory testing confirmed.

This guide explains every section of a peptide COA so you can evaluate quality before purchasing from any supplier.

What Is a Certificate of Analysis?

A COA is a document issued by a testing laboratory that reports the results of quality control tests performed on a specific production lot. For peptides, it typically includes purity analysis (HPLC), identity confirmation (mass spectrometry), appearance, and additional quality metrics.

Critical distinction: A legitimate COA is lot-specific — it matches the exact batch number on the vial you receive. A generic COA that says "BPC-157" without a lot number is a red flag.

HPLC Purity (The Most Important Number)

What it is: High-Performance Liquid Chromatography separates the contents of a sample by passing it through a column. Each component appears as a peak on a chromatogram.

What to look for:

• ≥99% purity is the research-grade standard for most peptides
• ≥98% is acceptable for many applications but indicates more impurities
• Below 95% is not research-grade and may contain significant degradation products or synthesis byproducts
• The chromatogram should show one dominant peak (your peptide) with minimal or no secondary peaks

Red flags: No chromatogram shown, purity listed without test method, purity claims without lot number reference.

Mass Spectrometry (Identity Confirmation)

What it is: MS measures the mass-to-charge ratio of molecules. For peptides, it confirms molecular identity — proving the compound is what it claims to be.

What to look for:

• Observed molecular weight should match the theoretical/expected value for the peptide
• Common methods: ESI-MS (Electrospray Ionization) or MALDI-TOF
• The mass spectrum should show a clear peak at the expected m/z value

Why it matters: HPLC tells you how pure the sample is, but not necessarily what it is. Mass spectrometry confirms identity. A sample could be 99% pure but the wrong compound — MS catches that.

Lot Number

What it is: A unique identifier for a specific production batch.

What to look for:

• The lot number on the COA must match the lot number on your vial
• Different lots can have slightly different purity levels — that's normal
• If a supplier provides the same COA for all orders regardless of lot, that's a red flag

Appearance

The COA should describe the expected visual characteristics of the compound. For most peptides: "White to off-white lyophilized powder." For copper peptides like GHK-Cu: "Blue lyophilized powder."

Discoloration, clumping, or liquid in a lyophilized vial indicates storage or handling issues.

Endotoxin Testing

What it is: Tests for bacterial endotoxins (lipopolysaccharides) that can contaminate peptide synthesis.

What to look for:

• <0.5 EU/mg is a good standard for research-grade peptides
• LAL (Limulus Amebocyte Lysate) is the standard test method
• Not all suppliers include endotoxin testing — those that do are generally more thorough

Test Laboratory

• Independent third-party: Best — testing is done by a lab that doesn't sell the peptide
• In-house testing: Acceptable but less independent
• Manufacturer-provided only: Weakest — the company making the peptide is testing their own work

The gold standard is independent, accredited laboratory testing with the lab name, accreditation number, and analyst signature on the COA.

COA Red Flags

• ❌ No lot number
• ❌ No chromatogram or mass spectrum
• ❌ Same COA document for every order/lot
• ❌ Purity claims without test method specified
• ❌ No laboratory name or accreditation
• ❌ COA date significantly older than purchase date
• ❌ "Certificate of Analysis available upon request" with no follow-through

What a Good COA Looks Like

Every product page on OPSEK Labs includes an inline Certificate of Analysis showing:

• ✅ Compound name and lot number
• ✅ Test date
• ✅ Testing laboratory (Intertek Pharmaceutical Services)
• ✅ Test method (HPLC / ESI-MS)
• ✅ Molecular weight — confirmed
• ✅ Purity percentage
• ✅ Appearance
• ✅ Endotoxin level
• ✅ Release status

Summary

A Certificate of Analysis is not optional documentation — it's the foundation of reliable research. Before purchasing peptides from any supplier, verify that the COA is lot-specific, includes both HPLC purity and mass spectrometry identity testing, and comes from an identified testing laboratory. Your experimental results are only as good as your starting materials.