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Peptide Purity Testing
Reverse-phase HPLC with UV detection produces the area-percent purity number. LC-MS confirms that the main peak is what the label says it is. Together they form the minimum credible purity result for any research-grade peptide.
The Method
C18 column, water/acetonitrile gradient with 0.1% TFA modifier. Detection at 214 nm (peptide bond) and 280 nm (aromatic residues). Area-percent purity is calculated from integrated peaks at 214 nm. Method adapted from USP <621>.
Electrospray ionization in positive (and negative when needed) mode per USP <736>. The observed mass is compared to the theoretical monoisotopic mass to ±0.01 Da. Confirms the main HPLC peak is the target peptide and not a co-eluting impurity.
Every peak above the reporting threshold (typically 0.1% area) is integrated. The chromatogram and integration table are released with the COA so reviewers can see the full impurity landscape, not just the headline number.
Gravimetric fill check combined with assay-corrected active content gives the true mass of peptide per vial — distinct from the purity percent.
Specifications
Minimum sample
5–10 mg dry powder for purity + identity. 25 mg for full panel.
Reporting threshold
0.1% area at 214 nm. All peaks above threshold integrated.
Mass accuracy
±0.01 Da against theoretical monoisotopic mass.
Standard turnaround
5 business days from sample receipt.
Rush turnaround
3 business days at +50% surcharge.
Data retained
Raw chromatograms and spectra held 3+ years.
FAQ
SteriGenix Lab
Independent peptide analytics
