How to Read a Certificate of Analysis (And Why Most People Don't)

Every peptide vendor provides Certificates of Analysis (CoAs). Most people look at the purity percentage, see something above 95%, and assume they're getting quality product.

That's not how CoAs work.

A CoA is a detailed report that tells you everything about what you're actually buying — purity, identity, contamination levels, and safety markers. But only if you know how to read it.

Most people don't. They're essentially buying blind, trusting vendors to provide accurate summaries of complex analytical data.

Let me teach you how to read CoAs like a pro — so you can tell the difference between real quality control and marketing theater.

Understanding the Basic Structure

A proper CoA contains several distinct sections, each testing different aspects of product quality:

Header Information

Product name and batch number: Should match your product exactly
Testing date: Should be recent (within 6 months for peptides)
Testing laboratory: Should be named specifically, not just "accredited lab"
Customer information: Should match the vendor you purchased from

Red flag: Generic CoAs with no specific batch numbers or customers. These are template documents, not actual test results.

Test Methods Section

This lists the analytical methods used for each test. Common methods include:

HPLC: High-Performance Liquid Chromatography (purity analysis)
MS: Mass Spectrometry (identity confirmation)
LAL: Limulus Amebocyte Lysate (endotoxin testing)
ICP-MS: Inductively Coupled Plasma Mass Spectrometry (heavy metals)

If methods aren't specified, the CoA is incomplete.

HPLC Purity Analysis — The Numbers That Matter

HPLC measures relative purity — what percentage of your sample is the target peptide versus impurities.

Reading HPLC Results

Main peak: This represents your target peptide. Should be the tallest peak on the chromatogram.

Impurity peaks: Smaller peaks representing degradation products, synthesis byproducts, or contamination.

Purity calculation: Area under target peak ÷ total area under all peaks × 100

What the Purity Numbers Actually Mean

98-99% purity: Excellent. Minimal impurities, high-quality synthesis.

95-97% purity: Good. Acceptable for most research applications.

90-94% purity: Moderate. May be acceptable depending on impurity types.

Below 90%: Poor. Significant impurities present, likely quality control issues.

Important: Purity percentage alone doesn't tell the whole story. The types of impurities matter as much as the total amount.

Understanding Impurity Patterns

Deletion sequences: Peptides missing amino acids (common synthesis error)

Addition sequences: Peptides with extra amino acids (also synthesis-related)

Oxidation products: Common with peptides containing methionine or cysteine

Degradation products: Usually indicates storage or handling issues

Some impurities are relatively harmless (minor deletion sequences). Others can be biologically active or even harmful (oxidation products, bacterial contamination).

Identity Confirmation — Proving You Got What You Paid For

HPLC measures purity, but it doesn't confirm identity. You need mass spectrometry for that.

Mass Spectrometry Basics

MS measures the exact molecular weight of your peptide. Each peptide has a specific theoretical molecular weight based on its amino acid sequence.

What to look for:

Observed mass: The actual measured molecular weight
Theoretical mass: The expected molecular weight for the target peptide
Mass difference: Should be minimal (within 1-2 mass units)

Red flags:

Large discrepancy between observed and theoretical mass
Multiple major peaks suggesting mixed compounds
Absence of MS data entirely

Why Identity Confirmation Matters

Without MS confirmation, you have no idea if you're getting the right compound. I've seen vendors sell completely different peptides with high HPLC purity but wrong molecular weight.

Example scenario: Vendor claims to sell BPC-157 (molecular weight 1419). HPLC shows 98% purity. But MS shows molecular weight 1543 — you're getting a different peptide entirely.

Endotoxin Testing — The Safety Check Most People Ignore

Endotoxins are bacterial toxins that cause fever, inflammation, and immune responses. They're particularly dangerous with injectable compounds.

LAL Test Results

The LAL (Limulus Amebocyte Lysate) test measures endotoxin levels in Endotoxin Units (EU) per milligram.

Acceptable levels:

Injectable peptides: <5 EU/mg (some standards use <10 EU/mg)
Oral compounds: <20 EU/mg
Research chemicals: Standards vary, but lower is always better

Critical point: Many vendors skip endotoxin testing entirely because it's expensive and most customers don't ask for it.

Why Endotoxin Testing Matters

High endotoxin levels can cause:

Fever and flu-like symptoms
Injection site inflammation
Immune system activation
Interfere with peptide effectiveness

If your CoA doesn't include endotoxin data, assume it hasn't been tested.

Heavy Metal Screening — The Long-term Safety Factor

Heavy metals accumulate in your body over time. Even small amounts can be harmful with repeated exposure.

Common Heavy Metals Tested

Lead: Neurological toxin, especially harmful to developing brains

Mercury: Nervous system damage, kidney problems

Cadmium: Kidney damage, bone problems

Arsenic: Cancer risk, skin problems

Acceptable Levels

Standards vary, but generally:

Lead: <1 ppm
Mercury: <0.1 ppm
Cadmium: <0.5 ppm
Arsenic: <1 ppm

Lower is always better. Non-detect (ND) results are ideal.

Water Content Analysis

Peptides are hygroscopic — they absorb water from the air. High water content affects:

Accurate dosing calculations
Peptide stability over time
Value for money (you pay for water instead of peptide)

Typical water content: 5-12% for lyophilized peptides

Red flag: Water content above 15% suggests poor lyophilization or storage

Residual Solvents

Peptide synthesis uses organic solvents that should be removed during purification. Common residual solvents include:

Acetonitrile
Methanol
Dichloromethane
Diethyl ether

High solvent levels indicate incomplete purification and can cause toxicity.

What's Missing from Bad CoAs

Red flags that suggest inadequate testing:

Missing Test Types

No mass spectrometry (identity confirmation)
No endotoxin testing
No heavy metal screening
No residual solvent analysis

Vague Results

"Passes" without specific numbers
"Within specifications" without stating specifications
Rounded numbers that look estimated

Missing Documentation

No specific batch numbers
No testing dates
No laboratory identification
No test methods specified

Verifying CoA Authenticity

Anyone can create a fake CoA. Here's how to verify authenticity:

Laboratory Verification

Contact the testing lab directly
Verify they performed the tests
Confirm the results match the CoA

Legitimate labs will verify test results if you provide batch numbers and dates.

Consistency Checks

Compare CoAs from different batches
Look for suspiciously perfect results (exactly 98.0% every time)
Check if vendor uses the same lab consistently

What to Do with CoA Information

Reading CoAs is only useful if you act on the information.

Quality Vendors Will:

Provide comprehensive CoAs without being asked
Explain test results if you have questions
Use consistent, reputable testing laboratories
Batch-test every production run

Poor Vendors Will:

Provide minimal or fake CoAs
Refuse to answer technical questions
Use different labs constantly (lab shopping)
Provide generic CoAs for all batches

The Bottom Line

CoAs are your best tool for evaluating peptide quality — but only if you know how to read them.

Key takeaways:

Purity percentage is just one data point
Identity confirmation via MS is essential
Endotoxin testing protects your safety
Comprehensive testing indicates quality vendors

Don't trust vendors who won't provide detailed CoAs or answer technical questions about their testing. Your health and your wallet deserve better.

Take the time to understand what you're buying. In the peptide space, knowledge is literally your best protection against bad products and unscrupulous vendors.

Want help interpreting CoAs or vendor recommendations based on testing quality? Join our Skool community where members share vendor experiences and technical expertise.

The Peptide Daily Brief provides educational content for research purposes only. This is not medical advice. Always consult with a qualified healthcare provider.