Exact mass determination with maldi time-of-flight mass spectrometers

摘要

A method relates to exact mass determination of analyte ions in time-of-flight mass spectrometers using an ionization of analyte substances on sample supports by matrix-assisted laser desorption (MALDI), and an improvement in mass resolution by time-delayed ion acceleration in the field between the sample support and an intermediate acceleration electrode. It particularly relates to methods for the stabilization of a once calibrated mass scale when there are unwanted changes in the distance of the sample support from the intermediate acceleration electrode.An unknown change of this distance can be compensated for by a coupled change of both total accelerating voltage and partial acceleration voltage between sample support and intermediate electrode in a simple manner by adjusting the time of flight of ions from a reference substance to the value given by the calibrated mass scale. Oligomeric ions from the matrix of the MALDI method serve very well as reference ions. Furthermore, if the range of optimum focus is shifted by a change in the time delay, the calibrated mass scale can be kept valid for all masses through a simultaneous change of the accelerating voltage.