IN-SERIES COMBINATION OF A MAGNETIC-SECTOR MASS-SPECTROMETER WITH A TIME-OF-FLIGHT QUADRATIC-FIELD ION MIRROR

A tandem mass spectrometer consisting of a double-focusing magnetic-se ctor mass analyzer in series with a time-of-flight (TOF) mass analyzer has been designed and constructed. The TOF analyzer was a quadratic-f ield ion mirror. The method of ionization used was matrix-assisted las er desorption/ionization. Precursor ions were mass selected with the m agnetic-sector analyzer, and time focused by ion bunching prior to fra gmentation in a collision cell. The fragment ions were mass analyzed w ith the TOF analyzer, which possessed the property that residence time s (i.e., times of flight) in the mirror were independent of ion veloci ty. The theoretical background to the instrumental design is presented . Experimental results are presented, showing resolutions of 4000 in f ragment ion spectra and demonstrating effective high-energy collision- induced decomposition of peptide molecule ions. (C) 1998 American Inst itute of Physics.