Instrumental measures to enhance the mass resolution in matrix assisted laser desorption/ionization (MALDI) time-of-flight experiments: computational simulations and experimental observations

Abstract

Matrix assisted laser desorption/ionization (MALDI), one of the most successful methods for producing mainly intact molecular ions in the gas phase from large non-volatile compounds, prepares the ions in very unfavorable conditions as far as analysis in a time-of-flight mass spectrometer is concerned. The ions not only exhibit broad distributions of the initial velocity and the point of ion formation but also of the ion formation time. All these factors have a negative influence on the achievable mass resolution and precision. A number of techniques have been developed that try to compensate for the broadening of the flight-time distribution caused by these effects. In this work delayed extraction in combination with a reflectron is compared with the post source pulse focusing technique by computer simulations and experimental data. Emphasis is given to the way the two techniques affect the individual sources of flight-time distribution broadening and the detection of metastable fragments.