Two results that answer different questions
A peptide test report usually prints two analytical results side by side: a purity percentage from high-performance liquid chromatography (HPLC) and a mass spectrometry (MS) result. HPLC separates the components of a sample and reports how much of the detected signal falls in the main peak. MS measures the mass of the molecules present and shows whether a mass consistent with the expected compound was found. Read each result for what it measures; one cannot stand in for the other.
| Point | HPLC purity | Mass spectrometry |
|---|---|---|
| What is measured | The share of the detected signal, usually UV absorbance, that falls in the main peak, as an area percentage. | The mass-to-charge ratio (m/z) of ions formed from the sample. |
| What it supports | That the sample contains little of anything else the method separates and detects. | That a molecule with the expected mass is present. |
| What it cannot show alone | Which compound the main peak is; water, counter-ions or anything the detector does not see. | How much of the sample that molecule makes up, or which of two molecules with the same mass is present. |
| On the BC10 report | Purity (LCMS/HPLC): 99.87% (specification ≥ 99.0%) | Mass Spectrum: Detected (specification: Conforms to [M+2H]2⁺, [M-H]-) |
What an HPLC purity percentage means
In reversed-phase HPLC, the dissolved sample passes through a packed column and its components leave it at different times. A detector, commonly measuring UV absorbance at a wavelength where peptide bonds absorb, records each component as a peak. The purity figure is normally the area of the main peak divided by the total area of all integrated peaks.
That calculation has limits. It counts only what the method separates and the detector sees: an impurity that leaves the column together with the main peak, or that barely absorbs at the chosen wavelength, does not lower the figure. Water and counter-ions do not appear as peptide peaks at all, so purity is not the share of the powder’s weight that is peptide. The figure also depends on the method (column, gradient, wavelength and integration settings), so read it with the report’s own specification and, where available, the chromatogram. Keep these details with every purity figure:
- The method named on the report, such as HPLC or LC-MS.
- The report’s own specification for the result.
- The chromatogram, if you need to see the peaks yourself.
What a mass spectrum result means
Mass spectrometry converts molecules into charged ions and measures their mass-to-charge ratio. Peptides analysed by electrospray ionization often carry more than one charge, so a single molecule can give several signals. In the notation printed on reports, [M+2H]2⁺ is the molecule with two added protons and [M-H]- is the molecule with one proton removed.
For BPC-157, the compound profile lists the formula C62H98N16O22 and a monoisotopic mass of 1418.7042 Da. From these, a [M+2H]2⁺ ion is expected near m/z 710.36 and a [M-H]- ion near m/z 1417.70. The BC10 report gives the result as “Detected” against the specification “Conforms to [M+2H]2⁺, [M-H]-” and prints no m/z values. If your review needs the observed values, ask for the spectrum.
A matching mass is good evidence that the expected molecule is present, but the result is qualitative. It does not say how much of the sample that molecule makes up, and molecules with the same formula, such as a peptide with two residues exchanged, have the same mass. Confirming the sequence itself needs further techniques, for example fragmentation in tandem mass spectrometry (MS/MS).
Read the two results together
Purity and mass support each other only when they describe the same sample. In a combined LC-MS run, the mass is measured on the peaks being separated, which ties the two results more closely than two independent tests. The ARA-290 10 mg report COA-1AvcSX-K-0F from PRISTINBIO (lot 20260905) follows the same pattern as the BC10 report with a different specification: Peptide Purity (HPLC) 99.77 % against ≥ 98.0%, and Mass Spectrum “Detected” against “Conforms to structure”.
- Check that both results name the same sample and lot.
- Keep each result with its method and its own specification.
- Do not turn a purity percentage into an amount, or a “Detected” mass result into a purity.
Keep each report’s limits
Each report covers only the sample and batch printed on it. Verify it on the issuer’s website and check that the lot number matches the goods you receive.
The issuer (TJQXGD) states that the data come from a third-party partner laboratory, that neither it nor the laboratory holds CMA/CNAS accreditation, and that this document has no legal certification validity. The issuer (PRISTINBIO) states that the analysis is for information only and applies to the sample provided.
Ask for the documents for the exact lot in your quote. A report describes only the batch it tested, so check that its lot number matches the lot you receive.
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