What ≥ 99 % HPLC purity actually means
Almost every research-peptide listing quotes a purity figure — 98 %, 99 %, sometimes higher. The number is meaningful, but only if you understand exactly what was measured.
Where the number comes from
Purity is a chromatography result. A sample is run through an HPLC column that separates its components into peaks based on how they interact with the column. The target peptide produces a main peak; impurities produce smaller ones. Purity is the area under the main peak divided by the total area of all peaks, expressed as a percentage.
Going from 99 % to 99.8 % means cutting the impurity fraction by four-fifths. For sensitive assays where related impurities can confound a readout, that difference can matter a great deal.
What purity does not guarantee
- It does not confirm identity — that is the job of mass spectrometry. A sample can be 99 % pure and still be the wrong molecule.
- It reflects what the detector saw under one method; impurities that do not absorb at the detection wavelength may not appear.
- It is a release figure, not a forever figure — storage after release still matters.
How to use the figure sensibly
Treat purity and identity as a pair. A high purity figure backed by a matching mass-spec identity on a lot-specific Certificate of Analysis is the combination worth looking for. Pepteed releases every lot against both, and reserves its ≥ 99.8 % grade for selected flagship peptides.