| 摘要 |
The invention relates to methods and instruments for measuring daughter-ion spectra in reflector time-of-flight mass spectrometers with post-acceleration of parent and daughter ions selected by means of a parent-ion selector. The invention consists of using a second selector to mask out all or at least a large fraction of the parent ions as well as those metastable daughter ions, which are produced by the decomposition of parent ions after post-acceleration. These ions not only produce 'ghost' peaks but also a high level of background noise as well as a parent ion peak which is excessively saturated and cannot be evaluated. This peak's ion current is capable of damaging the detector. The remaining small fraction of parent ions or the special addition of a small portion of parent ions, practically free of metastable ions, to the daughter ion spectra, produce a parent ion peak which can be used as a mass reference for a mass calculation to correct all instrument and control-related effects on the mass calculation.
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