HPLC and mass spectrometry: two different questions

High-performance liquid chromatography (HPLC) separates the components of a sample. The resulting chromatogram shows relative peak areas, which is where a percentage purity figure comes from.

Mass spectrometry (MS) measures mass-to-charge ratios and is used to confirm identity: whether the molecule present matches the expected molecular weight of the declared sequence.

A sample can be highly pure and still be the wrong compound, which is why identity and purity are reported separately. A batch document without an identity method is incomplete.

Additional tests such as water content, residual solvents or endotoxin screening answer further questions and are reported independently.