How to Read a Certificate of Analysis

Why the COA Matters

A Certificate of Analysis (COA) is a document issued by a testing laboratory that reports the results of quality testing performed on a specific batch of product. For peptides, the COA is the single most important document a consumer can review, because it provides objective, measurable data about what is actually in the vial — as opposed to what the label claims.

Every legitimate compounding pharmacy and reputable peptide supplier provides batch-specific COAs. If a vendor cannot or will not provide one, that alone is sufficient reason to look elsewhere. But having a COA is only the first step. You need to be able to read it critically, because not all COAs are created equal.^[1]

Identity Testing: Is This Actually What It Claims To Be?

The identity section confirms that the compound in the vial matches what's on the label. The gold standard for peptide identity testing is High-Performance Liquid Chromatography (HPLC), often coupled with mass spectrometry (LC-MS).

What to look for:

• Method: Should state "HPLC" or "LC-MS." If the method is listed as "visual inspection" or "organoleptic," that's not identity testing — it's someone looking at the powder.
• Result: Should confirm the compound identity matches the reference standard. Look for language like "Conforms to reference standard" or a matching retention time.
• Retention time: The HPLC retention time should be reported and should match the expected value for that peptide. A significant deviation suggests the product may not be what it claims.

Red flag: A COA that lists identity as "Pass" without specifying the analytical method used. Legitimate labs always report their methodology.^[2]

Purity and Assay: How Much and How Clean?

The purity section is the most scrutinized part of any peptide COA. It tells you two things: the percentage of the target peptide in the sample (purity) and the total amount of peptide present (assay/potency).

Purity (HPLC):

• Acceptable range: For research-grade peptides, 95%+ purity is standard. For pharmaceutical-grade (USP-compliant), 98%+ is expected. Anything below 95% should be viewed with caution.
• Method: Should be reverse-phase HPLC (RP-HPLC). The mobile phase, column type, and detection wavelength (typically 220nm for peptides) should ideally be specified.
• Impurity profile: A thorough COA will list related substances — these are synthesis byproducts, truncated sequences, or degradation products. Each individual impurity should be below 1%, with total impurities below 5% for research grade or 2% for pharmaceutical grade.

Assay/Potency:

• What it means: The assay tells you the actual amount of active peptide per vial. A vial labeled "5mg" should contain between 90-110% of labeled amount (4.5-5.5mg) per USP standards.
• Net peptide content: Peptides are often sold with counter-ions (acetate, TFA) and residual moisture. A product may be "99% pure by HPLC" but have only 70-80% net peptide content after accounting for these. Some COAs report this separately as "peptide content" or "net peptide."

Red flag: Purity listed as exactly "99.9%" across multiple batches. Real analytical results show batch-to-batch variation. Identical numbers across batches suggest fabricated data.^[3]

Endotoxin Testing (LAL): The Silent Danger

Bacterial endotoxins are lipopolysaccharides (LPS) released from the cell walls of gram-negative bacteria. They are heat-stable, meaning they survive autoclaving, and they can cause fever, inflammation, sepsis, and even death when injected. This makes endotoxin testing critical for any injectable product.

The test: The Limulus Amebocyte Lysate (LAL) test is the standard method. It uses an extract from horseshoe crab blood that clots in the presence of endotoxins.

What to look for:

• Units: Results are reported in Endotoxin Units per milliliter (EU/mL) or per milligram (EU/mg).
• USP limit for injectables: Less than 5 EU/kg of body weight per dose. For a typical peptide injection, the specification is usually <0.25 EU/mg or <5 EU/mL in the reconstituted solution.
• Result: Should state a specific value (e.g., "<0.1 EU/mg") or "Passes USP <85>." A result of simply "Pass" without a numeric value is less informative but acceptable if the specification is stated.

Red flag: Endotoxin testing completely absent from the COA. For any product intended for injection, this is non-negotiable. A vendor who doesn't test for endotoxins either doesn't understand the risks or doesn't care about them.^[4]

Sterility Testing

If a product is sold as sterile (ready to inject), the COA should include sterility testing results. USP chapter <71> describes the standard sterility test, which involves incubating product samples in growth media for 14 days and monitoring for microbial growth.

What to look for:

• Method: Should reference USP <71> or equivalent pharmacopeial method.
• Media: Typically Fluid Thioglycollate Medium (FTM) and Soybean-Casein Digest Medium (SCDM/TSB), testing for both aerobic and anaerobic organisms.
• Result: "No growth detected" after 14-day incubation.

Important distinction: Lyophilized (freeze-dried) peptide powders are not sterile products. They require aseptic reconstitution by the user. Sterility testing applies to the final reconstituted product or to pre-filled solutions. If a vendor sells lyophilized powder and claims "sterile," question what exactly was tested and at what stage.^[5]

Appearance, pH, and Moisture Content

Appearance: For lyophilized peptides, the expected result is "white to off-white lyophilized powder" or "white cake." A yellowish color or collapsed cake may indicate degradation or improper lyophilization. The COA should note the visual appearance and confirm it meets specification.

pH: For reconstituted solutions, pH should be within a specified range, typically 4.0-7.0 depending on the peptide. Extreme pH values can indicate degradation or contamination.

Residual Moisture (Karl Fischer): Lyophilized peptides should have low residual moisture, typically <3% by weight. Excess moisture accelerates degradation and reduces shelf life. The Karl Fischer titration method is the standard for this measurement.

How to Verify the Lab

A COA is only as trustworthy as the laboratory that issued it. Here's how to verify:

• Check accreditation: Look for ISO 17025 accreditation or cGMP compliance. These can be verified through the accrediting body's public database.
• Verify the lab exists: Search for the laboratory name and address. Legitimate analytical labs have websites, published methods, and verifiable physical locations.
• Contact the lab: Most accredited labs will confirm whether they performed testing for a specific company if you contact them directly with the batch number.
• Cross-reference batch numbers: The batch number on the COA should match the batch number on the product label. If they don't match, the COA may not apply to your product.

Red flag: COAs from laboratories that don't appear in any accreditation database, have no web presence, or share an address with the peptide vendor. In-house testing without third-party verification is a significant quality concern.^[6]

Summary: The COA Quick-Check

When you receive a COA, run through this checklist: Does it include identity testing by HPLC or LC-MS? Is purity above 95% with a proper impurity profile? Are endotoxin levels reported and within limits? Is the issuing laboratory accredited and independent? Does the batch number match your product? If any of these checks fail, you should think carefully about whether that product belongs in your body.