The header, the table and the signature block

A certificate of analysis is not a test result. It is a statement, made by whoever signs it, that a defined quantity of material identified by a batch number was subjected to defined tests by defined methods and produced results within defined limits on a defined date. Every element of that sentence is load-bearing, and a document missing any of them is not a weak certificate but a different kind of object: an assertion of quality with no way back to the evidence. The Journal has read several hundred of these and the distribution is not encouraging, though the reason is more mundane than the trade’s more excitable commentary suggests.

A certificate is a document, not a test

The confusion at the root of almost every dispute about certificates is a category error. A certificate of analysis is not a measurement. It is a record asserting that measurements were made, by named methods, on identified material, on a stated date, with stated outcomes, and that somebody reviewed and released the batch on that basis. The measurements exist elsewhere: in instrument data files, in analyst notebooks, in a laboratory information system. The certificate is the summary that travels with the goods.

This distinction has a practical consequence. When the Journal wants to know whether a purity figure is sound, we do not scrutinise the certificate; we ask for the underlying laboratory report and, where possible, the chromatogram. The certificate can only tell us what somebody concluded. The chromatogram tells us what the instrument saw, and the two are separated by decisions about integration, thresholds and reporting that the certificate does not record.

It follows that a certificate’s value is almost entirely a function of whether it can be traced back to that underlying evidence. A document with a batch number, a date, a named method and a named analyst is checkable in principle even if nobody ever checks it. A document with a percentage and a logo is not checkable by anyone, including the company that issued it, and the difference between those two situations is invisible to a buyer who reads only the number.

The header block: identifying the object

The top of a certificate answers the question, what is this document about. A complete header names the product, gives a catalogue or item number, gives the batch or lot number, states the quantity or fill weight, names the manufacturer and the site, and identifies the customer or order where applicable. Some add a chemical name, a sequence in single-letter code, a molecular formula and a molecular weight, all of which are useful because they let a reader check the theoretical values used elsewhere on the page.

The sequence in particular is worth insisting on. A certificate that prints the one-letter sequence has given a reader the means to calculate the expected mass independently, and therefore to check the identity line. Two of the twenty companies in the Journal’s dossier programme do this as standard. It costs nothing and it converts one line of the document from an assertion into a verifiable claim.

What a header should never do is identify the product only by a trade name. A vial described as a proprietary blend with no chemical identity, no formula and no sequence cannot be checked against anything, and a certificate for such a product is a document about a name. This is a documentary observation rather than an accusation, and the remedy is trivial: print the sequence.

The test table: four columns, and most certificates carry two

The body of a certificate is a table, and a complete one has four columns: the test performed, the method used, the specification applied, and the result obtained. Four columns, one row per test. That structure is not a convention peculiar to pharmaceuticals; it is what a record of controlled testing looks like in any field, because each column answers a question the other three cannot.

The method column is where the detail belongs — not the word HPLC but a method identifier, a gradient, a wavelength, a column chemistry. The specification column states what the batch had to achieve. The result column states what it did. A certificate carrying only test and result has dropped the two columns that make the result interpretable, and this is by far the commonest structural deficiency the Journal encounters.

The compendial framework for validating an analytical procedure exists precisely to establish that a stated method can discriminate what it claims to discriminate, which is why a method reference is not bureaucratic ornament but the hook on which everything else hangs.¹² A named method can be looked up, compared, criticised and repeated. An unnamed one cannot be, and a result generated by one is a number whose provenance stops at the page.

The lines nobody reads: appearance and solubility

Near the top of most test tables sit two entries that buyers skip and chemists do not: appearance and solubility. Appearance is reported as something like “white to off-white lyophilised powder”, and it is a real test with real discriminating power. A peptide cake that is yellow, or grey, or that has collapsed into a glassy plug rather than a light lyophilised mass, is telling you something about the drying cycle, about oxidation, or about a temperature excursion in transit.

Solubility is similarly underrated. A specification reading “clear, colourless solution on reconstitution in water at 1 mg/mL” establishes that the material dissolves at the concentration a user will need, without haze, and haze on reconstitution is a genuine finding: it can indicate aggregation, incomplete removal of a protecting group, or particulate contamination. It is also the only test on most certificates that a buyer can repeat at home.

The reason to press on these lines is that they are cheap, they are already on the form, and they degrade in a way the purity figure does not capture. A certificate reporting a white powder for material that arrives faintly yellow has not been falsified. It has been overtaken by events, which is exactly what a certificate with an eleven-month-old date of analysis should be expected to be.

Water, counter-ion and the mass in the vial

A lyophilised peptide is not pure peptide even when it is chromatographically pure. It is a salt, usually of trifluoroacetic or acetic acid, containing residual water that a hygroscopic powder acquires readily, and sometimes residual solvent from purification. Three lines on a certificate address this and they are usually absent: water content, counter-ion identity and content, and residual solvent.

Water is determined by Karl Fischer titration or by loss on drying, and the pharmacopoeial methods for it are old, settled and inexpensive.³ A peptide containing eight per cent water by mass contains eight per cent less peptide than its label implies, and the figure is not stable: it depends on how the vial was stoppered and how long it has been open. Counter-ion content is a larger contribution still for basic peptides purified in trifluoroacetic acid, where the counter-ion fraction can reach ten to twenty per cent of total mass.⁴

Put these together and the practical statement is the one this department repeats: the nominal mass on a research vial is an upper bound on the peptide it contains, not a value. A certificate that reports purity and is silent on water and counter-ion has told you the material is clean and nothing at all about how much of it there is.

What remains genuinely absent from this market is any documentation of what happens to a vial between the date of analysis and the day it is opened. Every certificate is a snapshot at manufacture; nothing records the four months in transit and storage that follow. Until somebody prices a cheap release-and-receipt check, the honest statement about any research vial is that its purity was measured once, some time ago, by a method that may not be stated.