A vial can have a chromatographic purity figure and a measured content result because they answer different questions. To use them together, first keep their denominators separate. This guide works through the calculations you can make from the supplied Semax report—and the tempting calculation that would misrepresent it.
Identify the three numbers
| Entry | Value | Meaning in this report |
|---|---|---|
| Label claim | 10 mg | The named vial size |
| Chromatographic purity | 99.18% | The reported main-component area percentage |
| Measured Semax content | 9.98 mg | The reported amount per vial |
Bachem's analytical guide explains that HPLC purity is based on chromatographic signal, while peptide content is a separate quantity. Water, counterions and other material can require measurements outside that area-purity result. Net peptide content also has its own basis and can include peptide-related impurities.Bachem analytical guide (opens in a new tab)
The practical consequence is simple: do not put every percentage and mass on the page into one mass-balance calculation. First ask what each measurement counts and what its reference quantity is. An area fraction and a mass fraction may both carry a percent sign without being interchangeable.
A valid comparison with the label claim
Using the report's figures, 9.98 mg divided by the 10 mg label claim equals 0.998, or 99.8% of the labelled amount. This is our arithmetic comparison of two stated masses. It is not another purity measurement and should be labelled “measured content as a percentage of label claim” if used in a record.
The absolute difference is 0.02 mg below the label claim. The document's content specification is 9.00–11.00 mg, so the displayed 9.98 mg falls within that interval. The comparison says nothing about variation between all vials in the lot; it uses the content result reported for the submitted sample.Semax report (PDF) (opens in a new tab)
Why 10 mg × 99.18% is the wrong shortcut
The multiplication produces 9.918 mg. The arithmetic itself is correct, but interpreting it as the amount measured in the vial is not supported. It assumes the label claim is a measured total mass and that area purity is the fraction of that mass attributable to the target. Neither assumption is established by those two entries.
Multiplying the separately reported 9.98 mg content by 99.18% is also not justified merely because both values appear on the same certificate. Before applying any correction, you would need the assay's calculation basis and an explanation of why a further factor is required. Otherwise the extra multiplication can change a result that already has its own analytical definition.
For this document, quote the 9.98 mg result as reported. If you need a different measurand—such as a defined dry-basis amount—request the relevant method and calculation rather than deriving it from unrelated columns.
Do not force the other results to total 100%
The report lists 4.38% water by Karl Fischer and 0.82% total related substances in its chromatographic results. Adding those values to 99.18% purity would mix measurement bases. A sum above 100% produced that way is not evidence of a contradiction; it is evidence that the chosen addition has no defined common denominator.Semax report (PDF) (opens in a new tab)
A genuine consistency check would start with the analytical definitions, sample basis and calculation rules. It could then ask which quantities belong in a shared balance. A certificate summary is not always enough to perform that exercise, and leaving the balance uncalculated is preferable to reporting a spurious total.
Use two measurements to ask two questions
Consider a hypothetical 10 mg-labelled material with 99.5% area purity but a reported assay of 8.0 mg per vial. The high area percentage would not erase the content shortfall. Conversely, a vial meeting its content requirement would still need its impurity result assessed against the relevant requirement. These examples illustrate why a single headline percentage cannot summarise the whole report.
- For composition of the measured chromatographic signal, read the purity entry and its method.
- For the amount per vial, read the assay result and its units.
- For agreement with the label, compare the stated masses and name that comparison.
- For a pass or fail, use each result's own specification and decision rule.
Sources and further detail
- Supplied Semax 10 mg certificate (opens in a new tab)
MA-PEP-0041, revision 01; task DMAS3J7; lot PEP-41-3J7. Document-specific facts are transcriptions, not authentication.
- Bachem — Quality control of amino acids and peptides (opens in a new tab)
Analytical background on chromatographic purity and peptide content; the numerical examples here are our own or transcribed from supplied reports.
Sources checked 19 September 2026. Supplied report examples are document readings, not independent authentication or new measurements.