With research peptides you often see a purity of “≥98%”. But what does that number actually tell you, and what is in the rest? In this article we explain.
Purity according to HPLC
Purity is measured with HPLC (high-performance liquid chromatography). A sample is sent through a column, and the substances in it are separated from each other. Each substance produces a peak in the chromatogram. Purity is the share of the main peak, the intended peptide, relative to all peaks combined.
What is the remaining 2%?
The rest usually consists of substances formed during synthesis, such as:
- Peptide chains that are missing one amino acid or have one too many
- Small amounts of oxidised variants
- Residues of protecting groups from the manufacturing process
At a purity of 98% or higher, these by-products are limited enough that the material is suitable for most research purposes.
Purity is not the same as identity
HPLC shows how pure a sample is, but not automatically which molecule it is. For that, mass spectrometry (MS) is often used, which confirms the molecular mass. A good COA (COA) therefore states both the purity and the identity.
Why the batch matters
Each production run, the batch, is tested separately. A purity percentage therefore only says something about the batch the report belongs to. So check that the batch number on your vial matches the COA. At Peptide Europe, every batch is HPLC-tested (≥98%) and the COA per batch is online.
How to recognise a reliable report
- It shows a batch number and a test date
- The chromatogram is included, not just a percentage
- The laboratory is named
All products at Peptide Europe are intended strictly for scientific research and not for human consumption.