INSTRUMENTAL MEASURES TO ENHANCE THE MASS RESOLUTION IN MATRIX-ASSISTED-LASER-DESORPTION IONIZATION (MALDI) TIME-OF-FLIGHT EXPERIMENTS - COMPUTATIONAL SIMULATIONS AND EXPERIMENTAL-OBSERVATIONS/

Matrix assisted laser desorption/ionization (MALDI), one of the most s uccessful methods for producing mainly intact molecular ions in the ga s phase from large non-volatile compounds, prepares the ions in very u nfavorable conditions as far as analysis in a time-of-flight mass spec trometer is concerned. The ions not only exhibit broad distributions o f 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 fligh t-time distribution caused by these effects. In this work delayed extr action in combination with a reflectron is compared with the post sour ce pulse focusing technique by computer simulations and experimental d ata. Emphasis is given to the way the two techniques affect the indivi dual sources of flight-time distribution broadening and the detection of metastable fragments. (C) 1997 Elsevier Science B.V.