A Certificate of Analysis (COA) is the primary quality document in research peptide sourcing. It should tell you, unambiguously, what molecule is in your vial and in what quantity — verified by a laboratory with no financial stake in the answer. This guide walks through a real COA from our library, field by field, so you can evaluate any peptide COA from any vendor.

What a COA Is — and What It Isn’t

A COA is a lab-issued document reporting the results of analytical testing on a specific batch of a specific compound. A legitimate COA for a research peptide should include:

• The name and address of the testing laboratory
• The compound name and batch number being tested
• The date the testing was performed
• The analytical method used for each test
• The result of each test with units and pass/fail determination
• A signatory (the name and credentials of the analyst who reviewed the results)

A COA is not a guarantee of human safety or efficacy. It is a quality control document for research use. The presence of a COA does not indicate FDA approval, clinical testing, or any regulatory clearance for human use.

The Difference Between a Third-Party COA and a Vendor COA

This is the most important distinction in evaluating peptide quality documentation.

A vendor COA is produced by the company selling the peptide, using their own equipment and personnel. There is an obvious conflict of interest: the vendor has a financial incentive to report high purity numbers. This doesn’t mean every vendor COA is fraudulent — but it means you cannot verify the result independently.

A third-party COA is produced by an independent analytical laboratory that does not manufacture or sell peptides. The lab has no financial stake in whether the result is high or low — they report what the instruments show. The most widely recognized labs in the research peptide space are Janoshik Analytical, Colmaric Analitika, and Auriga Research. COAs from these labs carry independent verification that vendor COAs cannot provide.

When evaluating any vendor, always check: does the COA come from an independent lab, or is it on the vendor’s own letterhead? The answer is one of the clearest signals of operational credibility in this industry.

Reading Each Section of a Peptide COA

Header Information

The COA header should show: the lab’s name and contact information, the sample submission date, the report date, the client (vendor) name, the compound name, and the batch or lot number. The batch number is critical — it links the COA to the specific production run of the peptide. When you receive a vial, the batch number on the label should match the batch number on the COA.

Identity — LCMS (Liquid Chromatography–Mass Spectrometry)

This section answers the most fundamental question: is the molecule in the vial the molecule on the label?

LCMS works by separating the compounds in a sample by liquid chromatography, then ionizing and measuring the mass-to-charge ratio of the resulting fragments. For a peptide, the key number is the observed monoisotopic mass (or average mass, depending on the instrument settings). This should match the theoretical mass for the peptide sequence within the instrument’s mass accuracy (typically ±0.5 Da or ±0.01%).

What to look for: a COA should show both the theoretical mass and the observed mass, and they should match. Some COAs also show the full mass spectrum as a graphic — the dominant peak should correspond to the expected m/z for the protonated peptide. If the COA shows “identity: confirmed” without showing the observed vs. theoretical mass, that is insufficient documentation.

Purity — RP-HPLC (Reverse-Phase High-Performance Liquid Chromatography)

HPLC measures what percentage of the material in the vial is the intended peptide versus everything else — synthesis byproducts, deletion sequences, oxidized forms, counter-ions, and residual reagents.

The result is expressed as a percentage by peak area at UV detection (typically 210–220 nm, where the peptide bond absorbs strongly). A result of “99.2% by HPLC” means 99.2% of the integrated peak area in the chromatogram corresponds to the target peptide.

What to look for: the COA should show the chromatogram (the visual graph of peaks over time), not just the number. The main peptide peak should dominate. Minor peaks to the left or right represent impurities. The integration table should show the area percentages. If a COA shows “purity: 99%” with no chromatogram, you’re being asked to trust a number you cannot verify.

At Life Link Research, we ship at ≥99% by HPLC peak area and publish the chromatogram on every COA.

Residual Solvents — GC (Gas Chromatography, per ICH Q3C)

Solid-phase peptide synthesis uses several organic solvents — trifluoroacetic acid (TFA), dimethylformamide (DMF), acetonitrile, dichloromethane, and others. These solvents must be removed in the purification process. GC testing confirms they have been reduced below the limits specified in ICH Q3C, the international regulatory guideline for residual solvent limits in pharmaceutical substances.

Why it matters: residual TFA can affect biological assays, alter solution pH, and interfere with cell-based experiments at even low concentrations. Most research peptide vendors do not test for residual solvents. The absence of this test on a COA is a meaningful data gap for researchers running sensitive assays.

What to look for: results expressed in ppm (parts per million) for each solvent, with comparison to ICH Q3C Class 1, Class 2, and Class 3 limits. A pass result means every solvent detected is below the applicable limit.

Heavy Metals — ICP-MS (per USP <232>/<233>)

Inductively Coupled Plasma–Mass Spectrometry quantifies trace elemental impurities — arsenic, lead, cadmium, mercury, and others — that can enter a peptide preparation from raw amino acids, synthesis reagents, or glassware. USP <232> specifies acceptable limits; USP <233> specifies the validated test methods.

Why it matters: heavy metals bind non-specifically in many biological systems. Even sub-micromolar concentrations of some metals can alter cell viability, receptor binding, or enzymatic activity — confounding any experimental result that involves cell culture, receptor binding assays, or toxicology. The vast majority of research peptide vendors do not test for heavy metals.

What to look for: results for each tested element in µg/g or ppb, compared against the USP <232> permitted daily exposure limit for each element. All results should be below limits.

Bacterial Endotoxin — LAL Assay (per USP <85>)

The Limulus Amebocyte Lysate (LAL) assay detects bacterial endotoxins — lipopolysaccharides (LPS) released from the outer membrane of gram-negative bacteria. Endotoxin is a potent activator of the innate immune system via TLR4.

Why it matters: endotoxin activates inflammatory pathways at picogram concentrations. If you are studying any aspect of immune function, inflammation, or cell viability, endotoxin contamination in your peptide will generate confounding signal that is indistinguishable from the biology you’re studying. This is the most critical test for researchers using peptides in cell-based assays or animal models.

What to look for: results expressed in EU/mg (endotoxin units per milligram). The USP <85> limit for parenteral drug substances is 0.5 EU/mL. A high-quality COA will show the actual quantified result, not just “pass” — confirming the endotoxin level is at or near the limit of detection.

Sterility — USP <71>

The USP <71> sterility test inoculates the sample into two culture media — fluid thioglycollate medium (for anaerobic bacteria) and soybean–casein digest medium (for aerobic bacteria, yeast, and fungi) — and incubates for 14 days. No growth in either medium = sterile.

Why it matters: sterility is what allows a peptide to be used in injectable animal-model protocols without introducing microbial contamination into the experimental system. For any in vivo work, this test is a prerequisite for experimental validity.

What to look for: a pass/fail result per USP <71> with the lab’s attestation. The COA should note the incubation period (14 days) and the media used.

Red Flags on a Peptide COA

• No batch number — you cannot link the COA to a specific production run
• Vendor letterhead only — no independent lab listed anywhere on the document
• Purity number with no chromatogram — you cannot verify the integration
• No LCMS data — purity without identity confirmation is incomplete
• Vague method descriptions — “HPLC testing” with no wavelength, column, or method details
• No date or analyst signature — not a traceable quality document
• Only 2 tests listed — identity and purity with nothing else signals a minimal QA program

How to Use Our COA Library

All current and historical Life Link Research COAs are available at lifelinkresearch.com/coa/. Each entry includes the product name, batch number, test date, and a direct link to the Janoshik Analytical COA document. The batch number on your vial label should match the batch number in the library.

If you have questions about interpreting any specific COA result, email our support team — we will walk you through it.

Frequently Asked Questions

Q: What does “≥99% purity” actually mean?
A: It means that 99% or more of the integrated peak area in the HPLC chromatogram at 210–220 nm corresponds to the target peptide. Everything else — deletion sequences, oxidized forms, unreacted starting materials, counter-ions — makes up ≤1%. This is the standard threshold for research-grade peptides.

Q: Can I send the peptide I received to an independent lab myself?
A: Yes. Janoshik Analytical accepts direct customer submissions. If you want to independently verify a batch result, you can request a sample vial be tested. We welcome this — it’s exactly the kind of due diligence serious researchers should do.

Q: What is the monoisotopic mass vs. average mass on an LCMS result?
A: Monoisotopic mass uses the mass of the most abundant isotope of each element (e.g., carbon-12, hydrogen-1). Average mass uses the atomic weight averaged across all natural isotopes. For smaller peptides (<2,000 Da), LCMS typically reports monoisotopic mass. For larger peptides, average mass is more commonly used. The COA should specify which is reported.

Q: Why does the purity percentage sometimes differ slightly between batches?
A: Minor batch-to-batch variation is normal and expected in peptide synthesis. A result of 99.1% vs. 99.4% between two batches reflects normal variation in synthesis yield and purification efficiency — not a quality problem. Both meet the ≥99% threshold. The chromatogram is more informative than the number alone: a clean chromatogram with one dominant peak and no significant impurity peaks is the gold standard, regardless of whether the number is 99.1% or 99.7%.

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This guide is for informational purposes. Products described are intended strictly for laboratory research use and are not for human or veterinary consumption.

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Apply what you’ve learned here to our own documentation. All current batch COAs are in the COA library, with results for Semaglutide, Tirzepatide, Cagrisema, BPC-157, Retatrutide, and all other products in our catalog. Learn more about the 6-test panel behind every COA.