Peptide Purity Testing
Purity is the most important specification for a research peptide, but purity alone does not prove identity. Reliable characterization requires two orthogonal methods — chromatography to quantify impurities and mass spectrometry to confirm the molecule is the intended one.
HPLC purity
Reverse-phase high-performance liquid chromatography (HPLC) separates the target peptide from related impurities — truncated sequences, deletion peptides, protecting-group artifacts and oxidized variants — based on hydrophobicity. The result is reported as the area percent of the main peak, which is the stated purity.
A high-purity HPLC trace means the sample is dominated by a single chromatographic species, but it does not, by itself, prove that the species is the correct peptide.
Mass spectrometry for identity
Mass spectrometry (commonly MALDI-TOF or ESI-MS) measures the molecular weight of the intact peptide. The observed mass must agree with the calculated mass for the intended sequence within instrument tolerance. This confirms identity — that the molecule has the right formula — which HPLC cannot do alone.
Used together, HPLC and MS demonstrate that the correct molecule is present at the stated purity. This is why a complete Certificate of Analysis reports both a chromatogram and a mass spectrum.
Orthogonal confirmation
For some sequences, additional methods supplement HPLC and MS — for example, amino acid analysis for composition, or ion-exchange chromatography for charged variants. The principle is the same: no single method is sufficient, and orthogonal data gives confidence in both identity and purity.
For how to interpret these results on a supplier document, see how to read a peptide COA.
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Peptide Hub Biotech World Wide provides research compounds and scientific information for laboratory research use only. Products are not intended to diagnose, treat, cure or prevent any disease. This article is presented for research context and is not medical advice.