“Third-party tested” is a starting point, not an answer. A certificate of analysis shows what was measured, on which sample, using which method.
HPLC peak-area purity is a ratio of detected chromatographic signals under the reported method. It is not automatically a mass percentage of the full vial contents.
Water, salts, response differences, co-eluting material, and substances the detector does not see can affect interpretation. Identity and measured content require their own evidence.
No single line answers all five.
Look for the method, expected identity, and observed result. Mass-spectrometry evidence can support identity, but expected mass alone does not uniquely establish every sequence or structure.
Check: the reported material and method, not just a purity peak.
Read the reported HPLC peak-area percentage with the detector and separation method. It is not a direct measurement of all vial contents, and different substances can produce different detector responses.
Check: the chromatogram, method, and stated reporting basis.
Compare the label claim with the measured analyte content, units, and method. Total powder mass is not necessarily peptide content. Read measurement uncertainty where the report provides it.
Check: measured mg and their analytical basis, not the label repeated as a result.
Read the assay, result, units, reporting limit, and stated criterion. Endotoxin testing is separate from a test for living organisms. Method suitability matters, including when recombinant reagents are used.
Check: a result with units and method, rather than an unexplained “pass.”
A culture-based screen and a DNA-based screen answer different questions. Read the target organisms, method, sample quantity, and detection limit. A negative result is limited to that screen's scope.
Check: the exact screen. Do not relabel it as sterility testing.
A lab's name on a PDF is not enough. Verify the issuing source and identify precisely what was submitted for analysis.
Even a matching report describes tested samples. It does not demonstrate that each vial was tested or that all products from a supplier have the same coverage.
Primary-source foundations · checked 17 September 2026
NIST's peptide-purity research describes characterization and value assignment, rather than treating one chromatographic percentage as a complete answer.
Read the NIST publicationRead NIST's explanation of measurement uncertainty as a foundation for interpreting laboratory results.
Read the NIST explainerFDA's revised guidance and accompanying explanation include recombinant reagents. A method still needs to be suitable for its intended material and purpose.
Read the FDA explanationPublished analytical documents and access to research supply are different things. Choose the resource you need.
Open the documentation hub, then check the exact lot, accession, source, and test coverage.
View published lab reportsThe next lab's research-account route is for qualified laboratory research, not personal treatment or patient testing.
Research supply at the next lab