What to ask a peptide supplier before you buy

Before closing any transaction with a peptide supplier, there are five points you need to verify independently. If any one of them cannot be verified, the certificate on your screen does not prove what the supplier says it proves.

The certificate of analysis: per batch, not per compound

The most important document in any peptide purchase is the certificate of analysis (CoA). The standard trap is that "we have a CoA" says nothing about the specific batch you are about to receive.

A certificate issued against a different sample than the current batch does not report the purity or content of what is being dispatched. Batches vary: different synthesis processes, different starting material suppliers, and different storage conditions produce different results. A certificate that is accurate for one synthesis run may not reflect the next one from the same supplier.

The right questions are:

• What is the task number on the certificate?
• Does that number correspond to the batch being dispatched to me?
• Can I verify the certificate directly on the laboratory's website?

PeptoClinic publishes batch reports on its quality page with task number, analysis date, and content per vial. If a supplier cannot answer all three questions with documents in hand, move on to the next.

The laboratory: who signed it and whether verification works

The laboratory name on a certificate needs to be independently verifiable. Janoshik Analytical, for example, has an online verification system where you can enter the task number and confirm that the report exists and matches what the supplier provided.

Ask:

• Which laboratory issued the certificate?
• Does that laboratory have active online verification?
• Does the verification link work right now?

The third point matters more than it sounds. Some laboratories have verification portals that return an error when opened. A certificate that cannot be confirmed at the source is not independent verification — it is a PDF. The four reports published by PeptoClinic, issued by Janoshik Analytical on April 13, 2026, each carry an identifiable task number. Two of the four have working verification links at the time of publication; the other two carry the task number but no active portal address, a distinction noted on the quality page rather than obscured.

Purity: method and exact number

"99% pure" appears on nearly every peptide supplier's site. The question that separates those who have the document from those who copied the phrase is: what analytical method was used?

The reference standard for peptides is HPLC (high-performance liquid chromatography). The result is expressed as a percentage of peak area. That number is reproducible and comparable across laboratories.

Ask:

• Was purity measured by HPLC?
• Is the result expressed as peak area?
• Does the certificate include the chromatogram?

The last question has a purpose. A chromatogram shows the full peak profile of the sample — not only the area assigned to the target compound, but any visible impurities alongside it. A certificate that states a purity number without the underlying chromatogram cannot be independently checked. The chromatogram is what a reviewer uses to confirm the figure.

The lowest purity result published by PeptoClinic across its four reports is 99.669%. That is the number to use when discussing minimum purity, not the highest result in the series. A supplier that avoids publishing specific results and settles for "≥99%" may be accurate — but without the per-batch certificate showing the exact figure, there is no way to confirm it.

Customs documentation for shipments to Argentina

For shipments to Argentina, there is a point not every supplier is aware of: how the import is classified determines which customs pathway it follows. Laboratory reference material enters through a different channel than a consumer product. The distinction affects both inspection procedures and duties.

A supplier who has not shipped research material through Argentine customs before is unlikely to know which classification applies, and the consequences of guessing wrong fall on the buyer, not the supplier. A package that arrives without the correct documentation as a reagent or research material can be held — and a hold the supplier did not anticipate is one the supplier will not know how to resolve.

The question to ask before purchasing is whether the supplier prepares customs documentation so the shipment enters as a reagent or research material. For compounds with specific demand in the Argentine market — such as retatrutide or BPC-157 — the supplier should know the tariff classification that applies to the material as a laboratory reagent rather than as a supplement or medicine.

Temperature and what happens with delays

Lyophilized peptides are stable at room temperature for weeks when properly sealed and kept away from moisture and light, which is why transit needs no cold chain. The picture changes in a customs warehouse, where temperature and humidity may not be controlled and a hold can last days or weeks. Storage recommendations also vary by compound: conditions appropriate for one peptide may not be appropriate for another.

Ask:

• Does the vial travel sealed and with desiccant?
• What storage temperature do you recommend for this specific compound?
• What is your protocol if the package is held at customs?

The answer to the third question says a great deal about the supplier's actual experience on that route. A supplier without a concrete answer has probably not shipped to that destination with any regularity. PeptoClinic's shipping terms are available on the shipping page.

Regulatory status

None of PeptoClinic's compounds is approved by ANMAT or the FDA. No certificate of analysis, however detailed, changes that. Purity results report the composition of the sample; they say nothing about safety or suitability for administration in a living organism.

A physician reviews every PeptoClinic consultation before anything ships. Prices are on the pricing page; anything not listed there can be asked about through a consultation.

The direct question to any supplier is: what is the regulatory status of the material, and who reviews the request? The answer has to be clear, without qualification.

The five questions in order

Before contacting any supplier, be clear on which specific compound you need. A supplier will ask exactly that, and if the answer is vague, the guidance will not be specific.

The five minimum questions:

• Do you have a per-batch certificate of analysis for that compound?
• Which laboratory issued it, and does it have active online verification?
• What was the HPLC purity result for that specific batch?
• How do you classify the material in customs documentation for Argentine shipments?
• What is the regulatory status of the material, and who reviews the request?

If all five answers are clear and documented, there is something to work with. If any one is not, the supplier has not finished answering.