Peptide Purity Explained: What HPLC and MS Testing Actually Measure

Purity figures appear on almost every research peptide listing, but the number is only meaningful if you understand where it comes from. Two analytical methods do most of the work: HPLC and Mass Spectrometry.

HPLC (High-Performance Liquid Chromatography)

HPLC separates the components of a sample and measures the relative proportion of each. The peptide purity percentage typically quoted on a Certificate of Analysis comes from this method — it tells you how much of the sample is the target compound versus leftover synthesis by-products.

Mass Spectrometry (MS)

MS confirms molecular identity — that the peptide is actually the sequence it is labelled as, rather than a similar but incorrect compound. Purity and identity are two separate checks, and a reliable CoA should include both.

Why This Matters

A high purity percentage on its own does not confirm identity, and a confirmed identity does not tell you about purity. Research relying on peptide batches should ideally have both pieces of data available.

Our Approach

We supply a Certificate of Analysis for the batches we stock, covering identity and purity testing carried out by independent labs. See our Peptide Glossary for more terminology explained.

This article is provided for general research information only. All products are sold strictly for laboratory research use.