Behind every vial in the Peptalis catalogue sits a series of measurements. They are not a formality. They are how an abstract promise (“this is peptide X, pure and complete”) is reduced to something that can be checked. The analytical panel is built deliberately: each method is on it because it answers a question the others cannot. No single number is asked to prove more than it can. That is exactly what makes the whole reliable.
The three core questions
Characterising a synthetic peptide turns on three separate quantities that are often read as one. Identity is the question of whether the right molecule was made. Purity is the question of how small the impurities are relative to the main component. Content is the question of how much of the weighed powder is actually peptide. They do not measure the same thing, and a high figure on one axis guarantees nothing on another. The panel therefore approaches them as three questions that each deserve their own answer.
Identity: mass spectrometry
The first question is identity, and mass spectrometry (MS) answers it most sharply. A mass spectrometer weighs ionised molecules with great accuracy and determines their mass-to-charge ratio. For a peptide that yields a highly precise measurement of the molecular mass, accurate enough to compare against the theoretical mass that follows from the amino acid sequence. If the measured mass matches, that is strong evidence the correct molecule was synthesised; if it deviates, it points to a missing amino acid, a residual protecting group, or a modification.
MS is on the panel because it does one thing exceptionally well: confirm what is in the vial. What it deliberately does not establish is how much of it is present, or whether it is biologically active; those are other questions, for other methods.
Purity: HPLC
The second question is purity, and it comes from high-performance liquid chromatography (HPLC). A dissolved sample is pushed through a column under high pressure; the different molecules emerge at different times and each forms a peak. The software expresses the main peak as a percentage of the total peak area. “98%” then means: of everything the detector saw with this method, 98% belongs to a single component.
HPLC is on the panel because it makes visible the related impurities that MS as a standalone measurement can miss: degradation products, synthesis residues, related peptides. It is a relative measure: a ratio, not a quantity. Which is precisely why it cannot answer the third question.
Content: amino acid analysis
The third question is content, and it is often forgotten. Not all of the powder in the vial is peptide: bound water, salts and counterions register on the balance without being peptide. For synthetic peptides the counterion form is the largest unknown, because the final product usually emerges from purification as a trifluoroacetate salt. The reference method for determining content is amino acid analysis (AAA): the peptide is fully hydrolysed into its individual amino acids, which are quantified precisely, from which the absolute amount of peptide follows.
AAA therefore measures mass where HPLC measures ratio. A peptide can be 98% pure by chromatography and at the same time have a net content of, say, 80%. The two do not contradict each other; they are two different numbers that are both honest. Content is determined or, where it has not been established, named as such.
Where the research calls for it: water, residual solvents and more
Beyond identity, purity and content, some measurements are not needed on every batch but appear on the panel on indication. Water content (determined by Karl Fischer titration) shows how much of the weight is bound moisture and speaks to stability. Residual solvents (by gas chromatography) reveal traces of solvents from synthesis and purification. Where the nature of a study calls for it, endotoxins can also be tested. These tests are not on every certificate by default; they appear where they answer a real question, and their absence is not read as the presence of a guarantee.
Why methods complement each other
The heart of the panel is that the methods cover each other rather than replace each other. HPLC separates the components and shows how clean the profile is; MS confirms the identity of the main component and helps name deviating peaks; AAA supplies the amount neither of them measures. Coupled as LC-MS, separated components are identified directly by mass. Each number answers its own question, and reliability arises precisely from that division of labour, not from one figure asked to carry everything.
What Peptalis does and does not establish itself
Transparency belongs to this panel. Peptalis obtains peptides from specialised laboratories and manufacturers and requires extensive analytical lab testing as part of selection (such as identity by mass spectrometry and purity by HPLC, with the accompanying documentation) as the first layer of data. Then comes the internal assessment by Peptalis following a fixed procedure: checks on identity, purity and stability, visual inspection and vial integrity, and where relevant a reconstitution test. Where Peptalis sees reason to, a batch can additionally be tested at an independent European laboratory: an internal control instrument on its own initiative, not a seal of approval and not a public partner claim. The lab testing behind the release stays an internal source; what the buyer receives is Peptalis's own Certificate of Analysis, in Dutch or English.
What has been verified is shown; what could not be established itself is named. That distinction, showing what the panel does and does not cover, is exactly what makes a certificate of analysis useful rather than merely reassuring.