How to compare research peptide raw material quotations like for like

This guide is written for a procurement reader who has three quotations on the desk and needs to know which ones are for the same material before deciding which one costs less. It quotes no prices and it does not describe what any compound does. It compares paperwork, because paperwork is what you are buying along with the solid.

Why three quotations for one CAS number do not line up

A quotation for research peptide raw material is a short document, and most of the variation between suppliers hides in what it leaves out. One supplier quotes per gram, another per vial. One states gross weight including counter-ion and residual water, another states net peptide content. One attaches a certificate for the lot that will ship, another attaches a "typical" certificate from a lot that was tested some time ago and may no longer exist. The headline figures look comparable. They are not.

The way to compare like for like is to refuse to compare until every quotation states the same set of facts. In practice it takes one message per supplier, and the suppliers who cannot answer in writing have told you something useful before you have spent anything.

The rest of this guide lists those facts, shows how to normalise the two pricing bases without quoting a price, walks through a worked comparison in words, and ends with a checklist you can paste into your own enquiry template. It applies to every compound on the compounds list, from a short tripeptide such as KPV to a copper complex such as GHK-Cu.

What a quotation must state

A quotation you can compare states the following in writing, on the quotation itself rather than in a chat message that will be hard to find later. If a field is missing, ask for it before the quotation goes into the comparison.

• CAS number. The registry number for the exact substance, not a trade name. CJC-1295 without DAC and with DAC are different CAS numbers, different molecular weights and different lines on a quotation.
• Format. Raw powder in a sealed container, or lyophilized vials. The two are quoted on different bases; the guide on vials versus raw powder covers the choice.
• Fill or grams. For vials, the stated fill per vial in milligrams and the number of vials per kit. For powder, the number of grams. A quotation that says "10 mg vials" without saying how many vials is not a quotation for a quantity.
• Net or gross weight, and salt form. Whether the stated mass is the gross weight of the solid, including counter-ion and residual water, or the net peptide content. Research peptides are commonly supplied as acetate or trifluoroacetate salts; the quotation should say which.
• Lot reference. The lot number the order will be filled from, where stock is allocated, or a written statement that a new lot will be produced and documented on the same template.
• COA terms. What the certificate for that lot reports (HPLC purity, MS identity, manufacturing, test and retest dates), whether it is supplied before payment, and whether it is a public record you can open yourself.
• Lead-time window. A window in days, described as typical, counted from a defined start point such as specification and payment confirmation.
• Incoterm or delivery basis. Whether the figure covers goods at the factory, goods handed to a carrier, or goods delivered to your door, and who is the importer of record.
• Cold-chain packing. Whether the parcel is packed cold-chain, and whether that is included or a separate line.
• Retest date. The retest date that will appear on the certificate for the lot offered, so you know how long the material can sit in your store before it is due for re-examination.
• Validity and payment terms. How long the quotation holds and what the payment terms are. The terms need to be the same across the quotations you line up.

Where this site stands on each field

This site quotes raw powder per gram from 5 g, cold-chain, and lyophilized vials per kit of ten. A sample order is 1 kit (10 vials); a private-label OEM run starts at 50 kits (500 vials). The quotation names the compound by CAS number, the format, the quantity, the delivery basis, the lead-time window and, for allocated stock, the lot it will be filled from. Lead times are stated as typical windows: a sample kit typically 3–7 days, a production batch typically 10–14 days, an OEM repeat batch typically 14–18 days, counted after specification and payment confirmation. They are not commitments and the quotation says so.

Normalising per-gram and per-vial offers

Raw powder is quoted per gram. Vials are quoted per kit of a stated fill. To compare them you need to put both on the same basis, and the basis that works is mass of solid per unit of money. No prices appear in this guide, so the arithmetic is shown in words.

For a vial quotation, multiply the stated fill by the number of vials in the kit to get the milligrams of solid per kit, then divide the kit figure by that mass. A kit of ten vials at a 5 mg fill is fifty milligrams of solid. A kit of ten at a 10 mg fill is one hundred milligrams. Only after that conversion does a per-milligram figure exist that can sit next to a per-gram powder figure divided by one thousand.

Then correct for the weight basis. If one quotation is gross weight and the other is net peptide content, the gross figure includes counter-ion and water that the net figure excludes. The difference is not trivial for short peptides with several basic residues, where the counter-ion can be a visible fraction of the weighed mass. If neither supplier states the basis, you cannot correct, and the comparison is a guess.

Finally, add back what the vial figure already includes and the powder figure does not: the weighing, the filling, the freeze-drying in the vial, the stoppering and capping, the label, and the per-unit chain of custody. A vial quotation is a quotation for a finished unit. A powder quotation is a quotation for material you will handle yourself. Which one costs less depends on what you were going to do with the powder once it arrived.

What cannot be normalised

A purity figure cannot be normalised. A lot at one purity result and a lot at another are different lots, and the difference in their figures does not tell you which one you want. Purity is a result on a certificate for a specific lot; it is a filter you apply before pricing, not a factor you multiply by.

A lead-time window cannot be normalised either. If your work needs material within a fortnight, a quotation that typically takes longer does not cost less; it is unavailable for that purpose. Put the lead-time window in a column of its own and read it as a pass or fail against your date.

Hidden differences that change the comparison

The fields above are the ones a quotation can state. The differences below are the ones it can omit without appearing to omit anything, and they are where like-for-like comparisons usually go wrong.

• A purity figure from a different lot. The quotation cites a purity result, and the certificate attached is for a lot other than the one that will ship. The number is real, but it is not yours. Ask which lot the order will be filled from and ask for the record of that lot.
• A "typical COA" instead of the certificate for the lot. A typical certificate is a template with representative numbers. It proves the supplier has a template. The certificate that matters is issued for one lot number and reports what that lot measured on a stated test date.
• No MS identity result. An HPLC purity figure without a molecular-weight result tells you how much of the chromatogram is one peak, not what that peak is. A certificate that reports purity and no identity has left out the half that tells you the material is the compound on the CAS line.
• Undocumented fill mass. A vial quotation at "10 mg" where the fill is stated on neither the label nor the certificate is a quotation for an unknown quantity. The fill should appear on the vial label and on the record for the lot.
• A lead time without a start point. Seven days counted from enquiry, from payment, or from the day the batch is released are three different windows. The quotation should say what day one is.
• Delivery basis left blank. A figure that stops at the factory gate is not lower once carriage, cold-chain packing and import handling are added. Ask for the Incoterm or a plain statement of what is included.

Reading a public batch record against a quotation

A public batch record removes several of these differences at once, because the lot number, the fill, the purity result, the molecular-weight result and the dates are all on one page that you can open without asking anyone. Pepti publishes its records in its own public COA library, one record per lot and fill, each linking to a PDF summary, and each compound page on this site mirrors the records for that compound in a batch table. The records also show the range a production has reported: the five public BPC-157 records report purity between 98.73% and 99.72%. Those are results for specific lots, not a specification for future lots, and a quotation citing one of them should name which one.

A worked comparison in words

Here is how three quotations for the same compound look once the fields are lined up. The suppliers are placeholders. The cells say what each quotation states, not what it costs, because the point of the exercise is to see which quotations are comparable at all before any figure is read.

What the table shows

Supplier A and Supplier B can be compared with each other once the vial figure is converted to a per-milligram figure and the weighing and filling that the vial figure includes are given a value. Supplier C cannot be compared with either until it states the weight basis, names a lot, reports identity and defines the lead-time start. It may turn out to be the smallest figure on the page. Until the fields are filled, it is a figure for an unknown quantity of an unconfirmed substance.

The table contains no numbers apart from the mention of fills. That is deliberate. A comparison that starts with price ends by rationalising the smallest figure. A comparison that starts with documentation ends with a short list of quotations that are for the same thing, and only then does price decide.

Red flags

None of the following is proof of a problem. Each is a reason to ask one more question before the quotation goes into the comparison, and a reason to write the answer down.

• A purity figure quoted in the body of a message with no certificate, no lot number and no test date behind it.
• A certificate without a molecular-weight or mass-spectrometry result, so that identity rests on the product name alone.
• A "typical" certificate offered in place of the lot record, with the lot record promised after payment.
• A lead time stated as a single number with no start point and no "typically" in front of it.
• A supplier who describes what the compound does when asked what the certificate reports. The question was about documentation; the answer was about something else.
• A refusal to state the manufacturer or the city of manufacture.
• Superlatives in place of fields. A quotation that calls its material pure and its service reliable, and leaves the lot reference blank, has filled the space where the facts go.

The comparison checklist

Copy this into your enquiry template. Every row is a yes or a no per quotation. A quotation enters the price comparison only when every row is a yes.

After the checklist

Once two or more quotations pass, convert them to a common basis as described above and compare. Keep the losing quotations on file; a supplier that answered every field is one you can go back to with one message. The supplier qualification checklist covers questions beyond a single quotation; the guide to matching a certificate to a batch covers the parcel when it arrives.

What Pepti publishes, and what is not claimed

Material on this site is manufactured by Pepti in Guangzhou. Pepti publishes batch records in its own public COA library, and each compound page mirrors them in a batch table. Each record is for one lot at one fill and reports an HPLC chromatographic purity result and a molecular-weight result from mass spectrometry, together with the manufacturing date, the test date and a retest date, and each links to a PDF summary. The record for the lot you are offered is the figure that applies to your material; the range across records is context, not a promise.

A quotation from this site names the lot where stock is allocated, so the record can be read before payment. For a lot that has not been published yet, the certificate is issued on the same template and supplied with the order documents. The quality page describes the documentation in more detail, order photographs show what the paperwork and packing look like on dispatch, and the FAQ answers common procurement questions.

What is not claimed: no certificate or registration is claimed on this site. The public records report purity and identity; they do not report sterility, endotoxin, residual solvent, water content or net peptide content, and this guide does not suggest otherwise. Nothing on this site describes what any compound does. Comparing quotations is about documentation and logistics, and that is all this guide has covered.