The Peptide Purity Problem: 5 Red Flags in Vendor COAs That Researchers Miss

A legitimate third-party HPLC report always carries the testing laboratory's name, address, and accreditation — usually as a header or footer on every page. If the COA only shows the vendor's logo and no independent lab identifier, it was almost certainly generated in-house.

The three most commonly cited legitimate testing labs in the peptide space are:

• Janoshik Analytical (Czech Republic) — the most widely recognized independent lab for peptide purity testing. Janoshik reports include a unique sample ID, HPLC chromatogram, and mass spectrometry data in a standardized format.
• MZ Biolabs (USA) — Arizona-based analytical laboratory specializing in peptide and protein characterization. MZ Biolabs reports include HPLC purity, mass spectrum, and peptide content analysis.
• Lab4Tox (Poland/EU) — independent analytical toxicology and purity testing laboratory with growing adoption among EU-based peptide vendors.

What to look for: The COA should prominently display the testing lab's name, not the vendor's branding. If you see a vendor logo but no independent lab name, treat the document as unverified marketing material.

A real HPLC analysis produces a chromatogram — a graph showing detector response over time, with peaks corresponding to different compounds in the sample. The area under each peak is integrated to calculate the percentage of each component.

A vendor COA that states "Purity: 99.4%" without showing the actual chromatogram is worthless. Why? Because without seeing the chromatogram, you cannot verify:

• Whether the "99.4%" figure refers to the main peak area relative to total peak area (the standard HPLC purity metric) or to some other measurement
• How many impurity peaks were detected and at what relative abundance
• Whether the baseline was clean or noisy (a noisy baseline can mask small impurity peaks)
• Whether the peak shape suggests co-elution of multiple compounds under a single peak

What to look for: A legitimate COA includes the full HPLC chromatogram with labeled axes (retention time in minutes vs. detector response in mAU), peak integration tables showing retention time, peak area, area percentage, and peak height for each detected component. Janoshik reports typically show this in a clean, standardized format.

HPLC purity tells you how pure the sample is. Mass spectrometry (MS) tells you what the compound actually is. A sample can show 99% purity on HPLC and still be the wrong peptide entirely if it was mislabeled or substituted.

Mass spectrometry confirms the exact molecular weight of the compound. For a research peptide with a known sequence, the expected molecular weight is calculable to within 1 Dalton. If the MS spectrum shows a mass that differs by more than 1 Da from the expected value, the compound is not what it claims to be — regardless of what the HPLC purity says.

What to look for: A complete COA includes both HPLC purity data AND a mass spectrum showing the molecular ion peak with the expected m/z ratio. Janoshik reports label this as "MS spectrum" or "Mass confirmation." If a vendor shows only HPLC data without MS confirmation, treat the identity of the compound as unverified.

A COA describes the analysis of one specific sample from one specific batch. It is not a blanket certification of a vendor's entire product line. A legitimate COA must include:

• Date of analysis: When was the sample tested? A COA from 2022 tells you nothing about the batch you're buying in 2026.
• Batch or lot number: Which production batch does this COA correspond to? If the vendor sells multiple batches under the same COA, the document is meaningless.
• Sample receipt date: When did the lab receive the sample? This helps verify that the testing was performed on recently manufactured material.

A common vendor tactic: post one COA from a single batch tested 18 months ago, and leave it on the product page indefinitely as if it certifies every batch they've ever sold. Legitimate vendors update COAs with each new production batch.

This is the simplest test and often the most revealing. Ask the vendor: "Can you send me the original laboratory PDF for this COA?"

A vendor with a legitimate third-party testing relationship will have the original PDF from the testing laboratory — typically a digitally signed document with the lab's letterhead, contact information, and unique report number. A vendor who stalls, offers excuses, or sends a screenshot instead of a PDF is almost certainly using a fabricated or outdated COA.

Some vendors go further: they provide a QR code or direct link to the lab's verification portal, where you can enter the report number and view the original results directly on the testing laboratory's website. This is the gold standard — it eliminates any possibility of document tampering between the lab and the customer.