The Complete Guide to Peptide Certificates of Analysis

This guide is intended for research purposes only. Nothing here constitutes medical advice.

Who Issues COAs: Third-Party vs In-House

This distinction is critical and most buyers overlook it entirely.

Third-Party Independent Labs

A third-party COA means the vendor sent a sample of their product to an external, independent laboratory for analysis. The lab has no financial relationship with the vendor beyond performing the test. This is the gold standard. Reputable third-party labs include Janoshik Analytical (widely used in the peptide community), ColMaxx, and various ISO 17025-accredited analytical labs.

In-House Testing

An in-house COA means the vendor tested their own product using their own equipment and staff. This is better than nothing, but it carries an obvious conflict of interest. The vendor has every incentive to present favorable results. In-house COAs should be treated as supplementary data, not proof of quality.

Bottom line: Always prioritize vendors who provide third-party COAs from named, contactable laboratories. If a vendor only offers in-house results, ask why they are not willing to pay for independent verification.

Key Sections of a COA

A complete COA for a research peptide should contain several distinct analytical sections. Here is what each one tells you and what numbers to look for.

HPLC Purity

High-Performance Liquid Chromatography (HPLC) is the primary method for determining peptide purity. It separates the target compound from impurities and quantifies each fraction as a percentage of the total.

• >98% purity — Research grade. This is what you want for any serious application.
• 95-98% purity — Acceptable for many research purposes, but not ideal.
• <95% purity — Concerning. Significant impurities present. The remaining percentage is unknown contaminants, truncated sequences, or degradation products.

Look for the HPLC chromatogram image if provided. A clean single peak with minimal shoulder peaks or noise indicates high purity. Multiple significant peaks suggest a poorly synthesized or degraded product.

Mass Spectrometry (MS)

Mass spectrometry confirms the molecular identity of the peptide. It measures the molecular weight of the compound and compares it against the expected (theoretical) mass. This is arguably the most important test on the COA because HPLC alone cannot tell you what the compound is — only how pure it is.

The COA should show:

• Expected molecular weight — the theoretical mass based on the amino acid sequence
• Observed molecular weight — the mass actually measured
• Acceptable deviation — typically within +/- 1 Da (Dalton) of the expected mass

If the observed mass is significantly different from the expected mass, you are not looking at the peptide on the label. It could be a different peptide, a truncated sequence, or something else entirely. A COA without mass spec data is fundamentally incomplete.

Amino Acid Analysis (AAA)

Amino acid analysis breaks the peptide down into its constituent amino acids and quantifies each one. This verifies that the peptide was synthesized with the correct sequence and ratios. It is particularly important for longer peptides where synthesis errors are more likely.

Not every COA includes AAA, but its presence is a strong quality signal. The reported ratios should closely match the theoretical values for the target sequence.

Endotoxin Testing (LAL Test)

The Limulus Amebocyte Lysate (LAL) test detects bacterial endotoxins — toxic byproducts of gram-negative bacteria. This is especially important for peptides intended for injectable research applications. Endotoxin contamination can cause severe inflammatory reactions.

Acceptable endotoxin levels are typically:

• <0.5 EU/mg — Standard threshold for injectable-grade material
• <5 EU/kg body weight — FDA guideline for parenteral drugs (for reference)

If a peptide is marketed as “injectable grade” but the COA lacks endotoxin testing, that claim is unsubstantiated.

Sterility Testing

Sterility testing confirms the absence of viable microorganisms. It is not always included on peptide COAs, particularly for lyophilized (freeze-dried) powders, since the reconstitution step introduces its own contamination variables. However, for pre-mixed or liquid formulations, sterility data is essential.

Appearance and Physical Description

This section describes the physical form of the peptide — typically “white to off-white lyophilized powder.” While basic, significant deviations (yellow color, clumping, sticky texture) can indicate degradation or contamination during manufacturing or storage.

Batch/Lot Number

The batch or lot number links the COA to a specific production run. This number must match the label on your vial. A COA is only valid for the batch it was generated for. A vendor who provides the same COA for every order regardless of batch is not providing meaningful quality data.

Red Flags: How to Spot a Fake or Misleading COA

Fraudulent and misleading COAs are common. Here are the warning signs that should make you question a document’s legitimacy.

1. No batch number or generic batch numbers — If the COA says “Batch: 001” or has no batch number at all, it is likely a template document reused for every order.
2. No lab name or contact information — A legitimate COA from a third-party lab will include the lab’s name, address, phone number, and often a signature or stamp. If you cannot identify who performed the analysis, the document is worthless.
3. Suspiciously perfect results — A COA showing 99.99% purity across every metric is almost certainly fabricated. Real analytical chemistry produces results with natural variation. A purity of 98.7% is more credible than 99.99%.
4. PDF metadata inconsistencies — Right-click the PDF, check properties. If the creation date is years old but the product is from a recent batch, or if the author field shows an unrelated company, the document may have been forged or recycled.
5. Same COA across multiple products — If a vendor provides identical COA documents for BPC-157, TB-500, and Semaglutide, something is very wrong. Each compound requires its own analysis.
6. No mass spectrometry data — HPLC alone tells you purity but not identity. Without MS data, you have no confirmation that the compound is what the label says. This is a major gap.
7. Round numbers everywhere — Real lab data has decimal points and slight imperfections. A COA showing Purity: 99.0%, Endotoxin: 0.00 EU/mg, Water Content: 0.0% is likely fabricated.

How to Verify a COA

If a COA lists a third-party lab, you can (and should) verify it.

1. Identify the lab — Find the lab name on the COA and look up their website independently (do not use a link provided by the vendor).
2. Contact the lab directly — Email or call the lab with the batch number and ask them to confirm they performed the analysis. Legitimate labs will verify results they generated.
3. Check lab credentials — Is the lab ISO 17025 accredited? Do they specialize in peptide or pharmaceutical analysis? A “lab” with no web presence, no accreditation, and no contact info is a red flag.
4. Cross-reference with community data — Forums and review communities often share and discuss COAs from specific vendors. If others have had their orders independently tested, compare your COA against community results.

What to Demand from Vendors

When evaluating a peptide vendor, your COA requirements should be non-negotiable:

• COA per batch — Not a single COA for their entire catalog. Each production batch should have its own analysis.
• Third-party laboratory — The lab should be named, contactable, and independent from the vendor.
• HPLC + Mass Spec at minimum — These two tests together confirm both purity and identity. Without both, the COA is incomplete.
• Endotoxin testing for injectable-grade products — If the vendor markets a peptide as suitable for injection research, endotoxin data should be present.
• Batch number matching — The batch number on the COA must match the batch number on your product label.
• Readily available — COAs should be downloadable on the product page or provided immediately upon request. A vendor who stalls, makes excuses, or says “we’ll email it later” is a red flag.

COA Review Checklist

Use this checklist every time you receive a new peptide shipment.

If a COA fails more than one of these checks, request a replacement or find a different vendor. Your research is only as good as your materials, and a COA is your only window into what you are actually working with.

For detailed information on specific peptides mentioned in this guide, check our BPC-157 compound guide, TB-500 compound guide, or browse the full compound guide index.