What a Certificate of Analysis Actually Proves, and What It Doesn’t

By Mike Vance, LabFirst Peptides

Nine peptide suppliers shut down in the last year. Buyers who lost deposits mostly tell the same story afterwards: the vendor looked legitimate, the website was professional, and every product page carried a certificate of analysis. The paperwork was there. It just did not say what people assumed it said. Replacing a supplier mid-project starts with reading that same document properly.

A certificate of analysis is a laboratory report on a specific batch of material. In chemistry supply it is the closest thing to a receipt for what is in the container, and reading one properly takes about ninety seconds. Most buyers spend four, looking for a number above ninety-nine per cent, and stop there.

That number is the least informative thing on the page.

Three measurements, sold as one

Purity, identity and content are separate tests answering separate questions, and they get collapsed into a single percentage all the time.

Purity asks what proportion of the material one substance is rather than a mixture. It is usually measured by high-performance liquid chromatography, which separates a sample into its components and reports the size of each. A result of 99% means the largest peak accounts for 99% of what came off the column. The test has a price of its own, and it is worth knowing what that fee buys.

It does not say the peak is the right substance. That is identity, and it takes a different instrument: mass spectrometry, which weighs the molecule and compares it against what the label claims. A vial can be 99% pure and 100% the wrong compound. Both statements fit on the same certificate, and only one of them is usually there. A worked example of how identity is confirmed on a single compound shows what that second report looks like.

Content is the third. A vial labelled ten milligrams can contain nine, with the remainder being water absorbed from the air or salt left from manufacture. The material is pure. The identity is correct. There is simply less of it than the label says. This is measured separately, and on most certificates, it is not measured at all.

A buyer reading “99%” has learned the answer to one of three questions and has no way to tell which two are missing.

The field that decides whether any of it is real

Everything above assumes the certificate is genuine. The single check that tests that assumption is whether the document can be verified at the laboratory that issued it.

Real analytical laboratories put a report number, a QR code or a lookup link on their work, and entering that code on the laboratory’s own website returns the same document. Not a PDF hosted by the seller. The laboratory’s site, the laboratory’s copy.

If a certificate carries no verification mechanism, it proves nothing about anything, because a PDF is a picture and pictures are trivial to alter. If it carries a mechanism that does not resolve, that is worse than none, and it is worth understanding why: somebody built the appearance of verifiability on purpose.

Three related things to check while you are there. The lot number on the certificate should match the lot on the container in your hand, because a real report for a different batch is still the wrong report. There should be a test date, since a certificate with no date could describe material from any year. And the document should state who submitted the sample. A report commissioned by the seller covers the material the seller chose to send, which may or may not resemble what ships to you.

What the closures had in common

Reading back through the suppliers that folded, the pattern is not fraud so much as absence. The certificates were often real documents from real laboratories. What was missing was the connective tissue: a lot number that tied the report to the box on the shelf, a date, a route to check it with somebody other than the seller.

That is a useful lesson for anyone buying laboratory materials, and it generalizes well past this industry. The question is never whether a supplier has documentation. Everyone has documentation. The question is whether any of it can be checked by someone who does not work there.

Reading one in ninety seconds

Six things, in order.

Is the issuing laboratory named, with a legal name rather than a logo? Is there a code, QR or link that resolves on that laboratory’s own site? Does the lot number match the container? Is there a test date? Is a method printed beside the purity figure, or just a percentage? And are identity and net content reported separately, or is the whole thing one number wearing three hats?

These are the checks LabFirst Peptides sets out in its supplier checklist for buyers of research materials, and they work on any supplier’s paperwork, including its own.

Six answers. If five are yes and no one is, you have learned something specific about where the supplier’s process stops. If four are missing, you have learned something about the supplier.

A word about my own position

I run a company that sells research chemicals, so I have an obvious interest in buyers caring about paperwork. It is worth saying where our own certificates stand, because it is a useful example of the difference between a certificate and a laboratory.

They are not published yet. The first lots are at the laboratory now, and each certificate posts on its product page and on our verification page the day it clears, with a lookup code that resolves at the laboratory’s own site rather than ours. Until then our verification page says exactly that, in those words, because a pending result stated plainly is worth more to a buyer than a number nobody can check.

Which is, in a way, the whole point. A number is not proof. The ability to verify it somewhere other than the seller’s website is proof.

Frequently asked questions

What does a certificate of analysis prove?

It reports what one laboratory measured on one batch of material, usually purity, sometimes identity, and less often net content. It says nothing about a different batch, and nothing at all if the document cannot be checked with the laboratory that issued it.

Is 99% purity enough on its own?

No. Purity describes what proportion of the sample is a single substance. It does not say that the substance is the one named on the label, which is a separate measurement made by mass spectrometry, and it does not say how many milligrams are in the container.

How do you check that a certificate is genuine?

Find the report number, QR code or lookup link, then enter it on the issuing laboratory’s own website rather than opening a PDF the seller hosts. A certificate with no way to check it, or one whose code does not resolve, is worth treating as absent.

What is the difference between purity and identity?

Purity is the proportion of the sample that is one substance, measured by chromatography. Identity is whether that substance is the compound on the label, measured by mass spectrometry. A vial can pass one and fail the other, and most certificates report only the first.

About the author

Mike Vance runs LabFirst Peptides, a research-use-only chemical supplier in Santa Ana, California. A fuller guide to reading certificates, including the checks above, is at labfirstpeptides.com/coa.