An accurate and clean calibration method for MALDI-MS.

A new method for the mass calibration of the matrix-assisted laser desorption/ionization-mass spectrometry spectrum is introduced. This method achieves the same accuracy as that of internal calibration but without its drawbacks. The interference and signal suppression by calibration standard are avoided, and a pure/clean sample spectrum is obtained. No prior knowledge about the sample quantity is required for the calibration. The effectiveness of the method is demonstrated with protein identification data.