HPLC — measuring how pure
High-performance liquid chromatography separates the contents of a sample into peaks as they elute from a column. The area of the main peak versus everything else gives you the purity percentage.
Mass spec — confirming what it is
Mass spectrometry weighs molecules. By comparing the measured molecular weight against the theoretical weight for your peptide sequence, you confirm the molecule on the chromatogram is the molecule on the label.
Why both matter
HPLC alone tells you something is pure — not what it is. Mass spec alone tells you the right molecule is present — not whether contaminants are too. You need both for a defensible result.
Frequently asked questions
What's the difference between HPLC and UHPLC?+
UHPLC uses smaller particles and higher pressures for faster, sharper separations. Both produce a chromatogram you can interpret the same way.