“99% pure” is the most common claim in the research peptide market. Understanding where that number comes from helps laboratories compare suppliers and interpret their own results.
How HPLC works, in brief
High-performance liquid chromatography pushes a dissolved sample through a packed column under pressure. Different molecules interact with the column differently and exit at different times. A detector, typically UV absorbance for peptides, records each component as a peak. For peptides, reversed-phase HPLC is the standard approach.
How the purity percentage is calculated
Purity by HPLC is usually reported as area percent: the area under the main peak divided by the total area of all detected peaks. If the target peptide accounts for 99 out of every 100 units of detected peak area, the result is 99%.
What the number does and does not mean
- It is method-dependent. A different column, gradient or detection wavelength can give a slightly different result.
- It only counts what is detected. Components that do not absorb at the detection wavelength, or that co-elute with the main peak, may not be resolved.
- It is not identity. A single clean peak does not prove the peak is the correct peptide. That is the job of mass spectrometry.
Common impurities in synthetic peptides
Synthetic peptides can contain truncated or deletion sequences (missing one or more amino acids), incompletely deprotected sequences, and oxidized or deamidated forms. Well-controlled synthesis and purification reduce these, and HPLC is the primary way to see how much remains.
Purity versus net peptide content
Lyophilized peptides are usually salts (for example acetate or trifluoroacetate) and retain some water. Net peptide content is the fraction of the powder’s weight that is peptide. A sample can have 99% HPLC purity and a net peptide content well below 100%, because counter-ions and water contribute weight without appearing as impurity peaks.
Reading the chromatogram
When a COA includes the chromatogram, look for one dominant peak, a flat baseline and the integration table listing each peak’s area. Large secondary peaks close to the main peak deserve a closer look.
Frequently asked questions
Is 98% purity enough for research?
It depends on the application. Many in-vitro protocols accept 95–98%, while sensitive assays may require higher purity. Check your protocol’s requirements.
Why do two labs report slightly different purity for the same batch?
HPLC purity depends on method conditions, so small differences between laboratories are normal.
Where can I see OxygenLab’s HPLC results?
Batch certificates with HPLC and MS results are published on our COAs page.
Research use only. OxygenLab products are supplied for in-vitro laboratory research and analytical use only. They are not for human or animal use and are not intended to diagnose, treat, cure or prevent any disease. See our Legal & Compliance policy.
Lab tool: Working out solution concentration? Try the free OxygenLab Peptide Calculator — enter vial mass and diluent volume to get mg/mL, µg/mL and molarity.
