How HPLC and Mass Spectrometry Verify Purity

Two tests, two questions

Reverse-phase HPLC answers how much of this material is the main component. Mass spectrometry answers is the main component the molecule it claims to be. Neither substitutes for the other, and a serious certificate carries both.

Reverse-phase HPLC

The sample is carried across a hydrophobic stationary phase under a gradient of increasing organic solvent. Components elute in order of hydrophobicity and are detected by UV absorbance at 214–220 nm, where the peptide bond absorbs. Purity is reported as the main peak area as a percentage of total integrated peak area. What to read on the chromatogram:

• Retention time of the main peak and whether it is consistent lot to lot
• Peak symmetry — tailing or shoulders indicate co-eluting related substances
• The impurity profile, not just the headline number: several small late-eluting peaks tell a different story than one large early peak
• Baseline quality and the integration limits used

Mass spectrometry

High-resolution LC-MS measures the mass-to-charge ratio of the ionized peptide. The observed monoisotopic or average mass is compared against the theoretical mass calculated from the sequence. A match within instrument tolerance confirms identity; a mass offset frequently points to a specific defect — an oxidation (+16), a deletion sequence, or an incomplete deprotection.

The supporting tests

Purity and identity still leave gaps that a full release package closes: net peptide content (how much of the vial mass is actually peptide), Karl Fischer moisture, residual solvents, LAL endotoxin, and sterility. PX1 runs the full package on every lot and publishes the records at /coa.

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Research use only. PX1 Research supplies compounds for laboratory and in-vitro research. Nothing on this page is medical advice, a dosing recommendation, or an offer for human or veterinary use.