The rules every peptide sample is run against, written down. What has to pass before we touch your sample, what each identity tier can and cannot claim, how purity and content are actually calculated, and what we do not yet publish.
Most testing decisions in this market are made on a purity percentage and a logo. Very little is published about what a lab actually checks before it will report a number, or what that number is permitted to mean. This page is our criteria. It is here so you can judge them, and so that when a result comes back you already know how it was decided.
System suitability runs at the start of every sequence, on the same instrument and column your sample will use. It is the check that the system is capable of producing a meaningful result at all.
| Check | Acceptance limit |
|---|---|
| Blank at analyte retention time | No interfering peak |
| Reference standard retention time, RSD | Not more than 1.0% |
| Reference standard peak area, RSD (when assay is reported) | Not more than 2.0% |
| Peak tailing factor | 0.8 to 2.0 |
| Retention factor (k) | ≥ 1.0, target ≥ 2 |
| Reference standard bracketing | Every 10 injections and at end of sequence |
The retention factor limit is worth understanding, because it is where a lot of weak identity claims come from. A compound eluting at or near the solvent front has not been separated from anything. We do not claim identity on the void. If a compound will not retain on the assigned method, it moves to a different method rather than being reported anyway.
Identity is not a single thing. These are the three levels we run, in plain terms, including what each one cannot tell you.
The sample principal peak retention time is compared against the mean reference standard retention time from the same sequence. Acceptance is a relative retention time of 0.98 to 1.02, or an absolute difference of not more than 0.2 min where retention falls between 8 and 15 minutes.
On the first lot of any SKU we also co-inject: sample and reference standard 1:1 in the same vial, which must give a single principal peak. A split or shouldered peak on co-injection means it is not the same compound, and identity fails.
Cannot tell you: the sequence. Retention time identity says the compound behaves like the standard on this method. It is not sequence confirmation and we do not describe it as such.Adds a UV spectral overlay of the sample peak against the reference standard across the full acquisition range, plus peak purity assessment. Peptides are read primarily at 214 nm with 280 nm as a qualifier. NAD+ is read at 260 nm with a λmax acceptance of 258 to 262 nm.
Adds intact mass confirmation. The observed mass must be consistent with the theoretical mass for the claimed compound within instrument tolerance, and the charge state used is recorded on the report.
Cannot tell you: sequence order. Mass spectrometry confirms molecular weight. Two peptides built from the same amino acids in a different order carry the same mass. Anyone selling intact mass as sequence confirmation is overstating it.Chromatographic purity is an area percentage: the area of the principal peak divided by the total integrated peak area at the method wavelength, with the solvent front discarded.
| Purity answers | Purity does not answer |
|---|---|
| What fraction of the UV-absorbing material that came off the column eluted as the target peak | How much peptide is in the vial. Purity is a ratio, not a mass. |
| Whether substantial chromatographic impurities are present | Which compound it is. Purity says one species dominates. It does not say which. |
| The composition of the lot that was tested | Anything about a different lot. The figure belongs to the batch in front of us. |
Lyophilized powder is not pure peptide by weight. It carries counterion salt, typically TFA or acetate, plus residual moisture. Both add mass to the vial without adding peptide. Content is measured against a reference standard of known assigned potency:
We report content as-is on the powder and, where the vial is intact, milligrams per vial against the label claim. Where Karl Fischer moisture and counterion data exist, we also report on an anhydrous free-analyte basis. The reference standard lot and its assigned potency appear on the certificate, because the content figure is only as good as the standard behind it.
A blend is not one compound and we do not report it as one. Each named active is identified and quantified against its own reference standard, and reported separately with its own content figure.
Formal validation of our platform peptide methods is in progress. What follows is not a claim about results we already have. It is the standard the work is being executed against, which is fixed by the compendia rather than chosen by us.
USP General Chapter <1225> determines which performance characteristics have to be established, according to what the method is for. A quantitative assay of the major component is a Category I procedure. Quantitative determination of impurities and related substances is Category II. The two categories require different work:
| Characteristic | Category I — assay of the main component | Category II — related substances |
|---|---|---|
| Accuracy | Required | Required |
| Precision (repeatability) | Required | Required |
| Specificity | Required | Required |
| Linearity | Required | Required for quantitative tests |
| Range | Required | Required for quantitative tests |
| Detection limit | Not required | Required for limit tests |
| Quantitation limit | Not required | Required for quantitative tests |
USP <1225> specifies what must be established. It does not set the numbers. The numeric acceptance limits are fixed in the validation protocol before any data is generated, guided by ICH Q2(R2) and ordinary pharmaceutical practice. Setting them afterwards, once the results are in, is how a validation becomes a formality. Ours are set in advance, and these are they:
| Parameter | Protocol acceptance target |
|---|---|
| Repeatability, RSD | Not more than 2.0% |
| Intermediate precision, RSD | Not more than 3.0% |
| Accuracy, mean recovery | 98.0 to 102.0% of nominal |
| Linearity, correlation coefficient | r ≥ 0.999 |
| Range | 80 to 120% of nominal test concentration |
| Specificity | No interference at the analyte retention time from blank or diluent; peak purity confirmed by diode array where available |
| Solution stability | Established across the working interval used in routine analysis |
System suitability for the chromatography itself is governed by USP <621>, and those limits are the ones published above. They apply to every sequence today, validated or not, because system suitability is what tells you the instrument was capable at the moment your sample was injected.
The table above is the target. We are not publishing demonstrated accuracy, precision or measurement uncertainty figures, because those studies have not closed. Quoting performance we have not established would be the exact failure this page exists to argue against.
When the studies close, the demonstrated values will be published here beside the targets, so you can see both the bar and what we actually cleared it by.
If you need validated methods now, for a regulated submission or a supplier qualification, say so and we will give you a straight answer on timing rather than a hopeful one.