Certificates of analysis for research peptides typically report two analytical results: a mass spectrometry result and an HPLC purity. Customers often read them as the same number expressed twice. They are not. Each test answers a different question, and a certificate is only meaningful when both are present.
Identity: mass spectrometry
Mass spectrometry measures the mass-to-charge ratio of the molecules in a sample. For a peptide, the result is compared with the theoretical molecular weight calculated from the sequence. BPC-157, for example, has a calculated mass of about 1,419 Da; a spectrum with the main signal at that mass (or at the corresponding multiply charged ions) confirms that the compound in the vial is BPC-157 and not something else. Mass spectrometry therefore answers the identity question. It does not say how pure the sample is, because the signal intensity depends on ionisation, not directly on quantity.
Purity: HPLC
High-performance liquid chromatography separates the components of a sample on a column and records them as peaks. The area of the main peak relative to the total area of all peaks is reported as purity, for example 98.7 %. The remaining area belongs to related impurities: truncated sequences from the synthesis, oxidised or deamidated forms, and residual protecting groups. HPLC answers the purity question. On its own it does not prove identity, because a wrong peptide can also produce a single clean peak.
What the numbers do not tell you
Purity by HPLC refers to the peptide fraction. It says nothing about water content, counter-ions such as acetate or trifluoroacetate, or residual solvents, which together are the difference between the labelled amount and the net peptide content. Neither test detects bacterial endotoxin or microbial contamination; those are separate assays. A certificate that reports identity and purity is the standard for research compounds, and anything beyond that is additional.
Reading a certificate in one minute
Lot number on the certificate matches the lot number on the vial.
Mass spectrometry: observed mass agrees with the calculated mass of the compound.
HPLC: main peak area in the high nineties, method and column stated.
Test date and laboratory named.
Products in our lab-tested category have a certificate of analysis on file for documented batches. Send us the lot number on your vial and we send the report.
For laboratory research use only. Not dosing or medical advice.