| 摘要 |
The invention relates to the exact mass determination of analyte ions in time-of-flight mass spectrometers with ionization of analyte substances on sample supports by matrix-assisted laser desorption (MALDI), and with an improvement in mass resolution by delayed ion acceleration in the field between the sample support and an intermediate electrode. It particularly relates to methods for subsequent correction of the flight time values if, during the scan, an incorrect adjustment of the distance from the sample support to the nearest acceleration electrode has occurred. The invention obtains a correction parameter for the flight times of all ions in the spectrum from an internal reference substance and corrects all flight times using a quadratic correction equation, before using the calibrated mass scale for the calculation of the exact masses. The quadratic correction equation contains a control parameter which multiplicatively affects both the linear and quadratic correction term. If no better suitable reference ions are available, oligomeric ions from the matrix of the MALDI method may be used as reference ions. The method can be applied regardless of adjustment in the optimum focus range before measurement of the spectrum, if the adjustments were made in a particular manner.
|
