What Does Purity Mean for Peptides?
Peptide purity is most commonly expressed as a percentage of the target peptide relative to all UV-absorbing species detected in a High-Performance Liquid Chromatography (HPLC) analysis. When OzPeptides states 99%+ purity, it means at least 99% of the detected material is the target peptide sequence.
How HPLC Purity Is Measured
Reverse-phase HPLC (RP-HPLC) is the gold standard for peptide purity analysis:
- The peptide sample is dissolved in an appropriate solvent
- Injected into an HPLC system with a C18 reverse-phase column
- Eluted with a gradient of water/acetonitrile (typically with TFA modifier)
- UV absorbance is detected at 220nm (peptide bond) or 280nm (aromatic residues)
- Peak area integration gives the purity percentage
What Impurities Are Measured?
Common impurities in synthetic peptides include:
- Deletion sequences — peptides missing one or more amino acids from incomplete coupling
- Truncation sequences — shorter chains from premature termination
- Oxidised methionine — if the sequence contains Met residues
- Deamidated residues — Asn or Gln converted to Asp or Glu
- Diastereomers — racemised amino acids
Mass Spectrometry Confirmation
HPLC purity alone does not confirm the peptide's identity — it only measures relative abundance of UV-absorbing species. Mass spectrometry (MS) — typically ESI-MS or MALDI-TOF — is required to confirm the molecular weight matches the target sequence.
All OzPeptides Certificates of Analysis include both HPLC purity data and MS confirmation. You can view example CoA documentation on our About page.
Why Third-Party Testing?
Third-party testing at an accredited, independent laboratory is critical because it removes manufacturer bias from quality data. OzPeptides uses independent laboratories to verify every batch — we do not self-certify purity claims.
This is why our purity guarantee is meaningful for research purposes: you can verify the data yourself on the CoA, which is available for every product batch in our catalogue.
All products are sold for research and laboratory purposes only. Not intended for human consumption.