How to qualify a research peptide supplier before you pay

Every item on this checklist is a question whose answer is a document, a photograph or a sentence on a web page. None of them needs a laboratory. The method is to ask, keep what comes back, and not move to the next step until the current one has an answer you can file. A supplier that passes is one whose material can be tied to a record before money moves. The checklist does not describe what any compound does, and nothing here is an instruction for use.

Identity: CAS number, molecular weight and names that agree

The first question is whether the supplier quotes by CAS number. A trade name can be stretched; a CAS Registry Number cannot. BPC-157 is CAS 137525-51-0, TB-500 is CAS 885340-08-9 and GHK-Cu is CAS 89030-95-5, and a quotation that carries those numbers is making a claim that can be checked against a public database. The compound pages on this site put the CAS number in the URL for that reason: /bpc-157-cas-137525-51-0 is a page about one registry entry.

The second question is whether the molecular weight on the quotation and on the certificate is consistent with the PubChem record for that CAS number. For BPC-157 the entry is CID 9941957, listing 1419.5 g/mol. A certificate whose mass-spectrometry result is close to that figure is reporting the same molecule. A certificate whose result is far from it, or that reports no molecular-weight result at all, has not established identity, whatever the purity figure says.

The third question is whether the names agree across the three documents you will hold: the quotation, the label on the container and the certificate of analysis. Look-alike substances are the reason this matters. Full-length thymosin β4 and the acetylated fragment the trade calls TB-500 are different substances with different CAS numbers; CJC-1295 with and without DAC are two registry entries, two certificates and two lines on a quotation. Where a compound has a salt form or a variant, the quotation should say which one and the certificate should match it. A supplier that lets the names drift between documents has not fixed what it is selling.

Documentation: a lot-specific certificate you can read before paying

A certificate of analysis is only useful if it belongs to the lot you will receive. The question is not whether the supplier has a COA but whether it has the COA for this lot, with the lot number printed on it, and whether you can read it before you pay. A certificate without a lot number is a description of what the supplier hopes to sell; a certificate with one is a record of what a particular batch was on its test date.

The certificate should report chromatographic purity by HPLC and an identity result from mass spectrometry, and it should carry the manufacturing date, the test date and a retest date. It should name the manufacturer. A record that reports purity with no identity result, or identity with no purity result, is half a certificate. The guide on matching a COA to the batch you receive covers the line-by-line comparison once the parcel arrives.

The strongest form of documentation is a public batch-record library: a page on the manufacturer's own site where the records for past lots can be opened by anyone, without an account and before any enquiry. It lets you see how many lots have been documented, what the purity results have been across them, and whether the dates on the records are in a sensible order. It also lets you check, later, that the certificate you were sent matches the public one for the same lot.

Manufacturing transparency: who makes the material, and where

Ask who manufactures the material, and expect a name and an operating address, not a region. A supplier that says the material is made in a particular city but will not name the factory is asking you to take the certificate on trust without saying whose certificate it is. A supplier that names the manufacturer gives you something to check: the manufacturer's own site, its batch-record library, its address.

Ask, separately, what the relationship is between the website you are buying from and the manufacturer. The honest answers are few and short: the site is the manufacturer, a sales channel run by the manufacturer, a distributor holding its stock, or a reseller that orders on demand. Each is a legitimate arrangement. What is not acceptable is a site that will not say which one applies, because that is the difference between a certificate that came from the factory and one that came from somewhere along a chain.

Ask whether the production and dispatch photographs on the site are the supplier's own. Stock photographs of generic laboratories are a flag, not because a photograph proves anything on its own, but because a supplier with its own operation has no reason to borrow someone else's. Dispatch photographs of actual orders, with lot labels visible, are the useful kind: they show the packing you will receive and the labelling you will match to the certificate.

Commercial terms stated in writing

Every term that will matter on the day a parcel arrives should be on the written quotation before you pay: the format and the fill or net weight; the quantity and the minimum; the lead-time window; the packing; the documents that will be supplied; and what happens if the goods do not match the record.

Lead times are the term most often misstated. A plain supplier states a window and says it is typical: a sample kit typically 3–7 days after specification and payment confirmation, a production batch typically 10–14 days, an OEM repeat batch typically 14–18 days. A fixed number of days is a promise production cannot always keep, and the word to look for on the quotation is "typically".

The mismatch term is the one buyers forget to ask about. Ask, in writing, what happens if the lot number on the container does not match the certificate, if the vial count or net weight is short, or if a seal is broken on arrival. The useful answer describes a procedure: report with the lot number and photographs, within a stated period, and the matter is handled against the record. A supplier that promises more than a procedure is promising something it may not be able to keep.

Communication: one named channel and replies that quote the lot

A supplier should have one named channel for enquiries, and the reply on that channel should read as if the person has the stock list in front of them. The test is simple: ask a documentation question and see whether the reply quotes a lot. "Yes, we have a COA" is not an answer. "The allocated lot for that fill is this one, and its record is here" is.

Three other things are worth noting in the first exchange: whether the quotation arrives in writing with the CAS number, the format, the quantity, the lead-time window and the allocated lot, or whether those details have to be drawn out one by one; whether a question about what is not documented, for example endotoxin or residual solvent, gets a plain no rather than a reassurance; and whether the person is willing to say that a lead time is typical rather than fixed. A supplier that can say no, and can say typically, is one whose yes means something.

Keep the exchange. The messages in which a supplier states the lot, the window and the documents are part of the evidence you are collecting, and they are what a mismatch is later resolved against. On this site the channel is the RFQ line, and the first reply names the applicable lot record.

Red flags

Any one of the following is a reason to stop and ask again. Two or more is a reason to stop. None of them is about the material; all of them are about whether the supplier can tie the material to a record, which is the whole of what qualification tests, because the record is the only thing you can check from a desk.

• A "typical COA" instead of the lot's. A certificate offered as representative of what the supplier usually ships is not a certificate for anything you will receive.
• A purity claim with no lot. A figure on a product page or in a message, with no lot number attached, is a marketing claim, not a result.
• A certificate with no lot number on it. It cannot be matched to a container, so it cannot be matched to your material.
• Claims of certificates or registrations you cannot verify. A logo or an acronym on a web page is not evidence. Ask for the document and the issuing body; if it cannot be checked, score it as absent.
• A website that will not say who makes the material. If the manufacturer is not named, the certificate has no author.
• Dates in the wrong order, or names that drift. A test date before the manufacturing date means the certificate was not generated from the batch record; a quotation, a label and a certificate with three different names means the supplier has not fixed what it is selling.
• Pressure to pay before documents are supplied. A supplier with the record to hand has no reason to withhold it until after payment.

A scoring table: criterion, what to ask, evidence to keep

Score each criterion as met or not met, on the evidence you have kept, and do not weight them. A supplier that is strong on communication and absent on lot documentation has not passed; the criteria are conditions, not points. Keep the evidence column as a folder per supplier. If the folder is thin after the first exchange, that is itself a score.

A sample-order plan: 1 kit or 5 g, check, then scale

Qualification ends with a small order, because the one thing a desk cannot check is whether the container that arrives matches the record you were shown. The sample order is the smallest unit that carries a lot number and a certificate: 1 kit (10 vials) in one fill, or 5 g of raw powder. Order one or the other unless you will use both formats.

The sample order is also the first time the lead-time term is tested. A sample kit typically ships in 3–7 days after specification and payment confirmation. If it ships inside the window the quotation stated, the term was real; if not, ask why before the larger order, not after. The guide on comparing raw material quotes covers how to line up two suppliers once both have sent a sample.

• Ask for the lot before paying. The quotation should name the lot the sample will be filled from where stock is allocated, and you should read its record first.
• On arrival, run the paperwork match: lot number on the container against the certificate, name and fill against the quotation, dates in order, seal intact. Photograph each step, and weigh what you can weigh against the stated net weight.
• If your process needs it, send a sealed unit to an outside laboratory with the lot number and the certificate, on your own account, and compare the result with the record.
• Enter the lot in your inventory record with its retest date and storage location, as the guide on storage and retest describes.
• Only then scale: a production batch, or for a branded run the private-label OEM minimum of 50 kits (500 vials), on the same documentation and the same checks.

How this site answers each item, and what it does not claim

Identity: every compound page on this site is named by CAS number in its URL, for example /tb-500-cas-885340-08-9 and /ghk-cu-cas-89030-95-5, and lists the formula, molecular weight and PubChem CID for that registry entry. Quotations name the compound by CAS number. Documentation: the material is manufactured by Pepti, Guangzhou, and Pepti publishes batch records in its own public COA library, mirrored in the batch table on each compound page, carrying the lot alias, the fill, an HPLC purity result, a mass-spectrometry identity result and the manufacturing, test and retest dates. The quotation names the lot where stock is allocated so that its record can be read before payment; the quality page explains what the records show and do not show.

Manufacturing transparency: the manufacturer is Pepti, operating address No. 18 Zhenliangyuan 2nd Road, Zhongluotan Town, Baiyun District, Guangzhou, stated on the about page and in the footer of every page. The dispatch photographs at /order-photos are of actual orders. Commercial terms: raw powder from 5 g, cold-chain, quoted per gram; vials by the kit; a sample order of 1 kit (10 vials); private-label OEM from 50 kits (500 vials); lead times stated as typical windows on each quotation. Communication: one channel, the RFQ line, with replies that name the lot.

What is not claimed: Pepti does not publish a storage-stability study per lot, does not report endotoxin, sterility, residual solvent or water content on the public summaries, and no certificate or registration is claimed on this site. The records say what a lot was on its test date. Material is supplied for research use only, and nothing on this site describes what any compound does.