Choosing a US peptide supplier — what separates them

The website tells you almost nothing

Supplier sites in this category converge on the same vocabulary — pharmaceutical grade, third-party tested, made in the USA, 99% purity. From the outside, most of those phrases are hard to check. Evaluating a supplier means asking questions whose answers are specific, checkable, and awkward to fake.

Ask where the API is synthesised

Most research peptides sold in the United States are synthesised overseas and finished domestically. That is normal and not disqualifying. What matters is whether the supplier says so plainly. A supplier who describes their finishing operation as manufacturing, without distinguishing where the active ingredient came from, has chosen ambiguity for a reason.

Ask who signs the Certificate of Analysis

A COA signed only by the company selling you the material is self-certification. It may be entirely accurate; it is not independent. Ask for the testing laboratory's name, and ask whether documentation is per-lot or per-product — a per-product certificate describes a batch you did not receive, which defeats the purpose of a lot number.

• ◆Per-lot COA with the lot number matching your vials.
• ◆The chromatogram itself, not only an area-percent figure.
• ◆Mass spectrometry confirming the expected molecular weight.
• ◆The testing laboratory named and identifiable.

Ask what goes in the agreement

This is the question that separates suppliers fastest. Verbal claims cost nothing. A supplier who will warrant conformity to the Certificate of Analysis in a signed agreement, state their payment terms in writing, and put their fulfillment fees on paper is describing a business. One who prefers to keep terms conversational is describing something else.

Questions worth asking before the first order

• ◆Where is the active ingredient synthesised, and where is it filled and finished?
• ◆Is the Certificate of Analysis per lot, and who performed the analysis?
• ◆What is the counter-ion, and is peptide content reported separately from gross mass?
• ◆What are your payment terms, and will you put them in writing?
• ◆What happens if a lot does not conform — replacement, credit, or a conversation?
• ◆Will you re-issue Certificates of Analysis in my name, and what exactly changes when you do?

A six-step verification checklist

1. 1.Match the lot number. The lot number printed on the vial label should appear on the certificate. A certificate for another lot, or one with no lot number, does not describe the vial in front of you.
2. 2.Identify the laboratory. The certificate should name the laboratory that ran the tests. Look the laboratory up, check its accreditation (for example ISO/IEC 17025) and what that accreditation covers, and confirm the report through the laboratory's own verification route where one exists.
3. 3.Compare the dates. The analysis date should fall after the lot was made and before it was shipped. A certificate dated long before the lot, or after it left the supplier, describes something else.
4. 4.Check identity by mass spectrometry. The observed mass should agree with the expected molecular weight within the tolerance the laboratory states. A purity figure alone does not show the material is what the label says.
5. 5.Check the purity method. An HPLC purity figure should state the method and the detection wavelength, and the chromatogram should be attached. A number with no method and no trace cannot be checked.
6. 6.Know how you would re-test. Decide which accredited laboratory you would send a sealed vial to, which tests you would ask for (identity by mass spectrometry, purity by HPLC), and what the supplier commits to in writing if the result disagrees.

What a COA cannot tell you

A Certificate of Analysis reports what one laboratory measured, on one sample, on one date, by the methods it names. It cannot tell you:

• ◆How the vial was stored and shipped after the sample was tested.
• ◆Whether every vial in the lot matches the sample the laboratory received.
• ◆Net peptide content, unless it was measured separately: HPLC area-percent purity is not the same measurement.
• ◆Contaminants the listed methods do not detect, such as residual solvents, endotoxin or heavy metals, unless those tests are reported.
• ◆Whether the material suits a particular experimental design.

What we publish

Our own answers: per-lot third-party testing with chromatograms on the site, US synthesis, fill and finish through US partners with the domestic and international origin of starting materials stated, and written terms — a price sheet for each account and a warranty of conformity to the Certificate of Analysis. The program is at /wholesale.