Two tests, two questions
HPLC (High-Performance Liquid Chromatography) answers the question: how pure is this peptide? Mass spectrometry answers: is this the correct peptide? Together, they provide both quantitative purity data and qualitative identity confirmation.
How HPLC works
HPLC separates a sample into its individual components by passing it through a column under high pressure. Each component elutes at a characteristic retention time, and the detector measures the relative area under each peak. The main peak area divided by total peak area gives the purity percentage.
How mass spectrometry works
Mass spectrometry ionizes molecules and measures their mass-to-charge ratio. By comparing the observed molecular weight against the known theoretical weight of the target peptide, analysts can confirm molecular identity with high precision.
Why both are necessary
A peptide could show 99.5% purity by HPLC but be the wrong molecule entirely — HPLC alone cannot confirm identity. Conversely, mass spectrometry confirms identity but doesn't quantify impurities. Using both methods together closes the verification gap that either method leaves open individually.