CALIBRATION POINT FOR LIQUID SECONDARY-ION MASS-SPECTROMETRY TANDEM MASS-SPECTRA MEASURED WITH AN EBQQ HYBRID MASS-SPECTROMETER

A protocol for establishing standard instrument conditions for the mea surement of product ion tandem mass spectra from parent ions generated by liquid secondary ion mass spectrometry (LSIMS) is presented. The i on at m/z 319 (C+) from 2-butyltriphenylphosphonium bromide is selecte d as the parent ion and then is subjected to collision-induced dissoci ation. The relative abundances of product ions at m/z 263 and 183 are monitored as a function of collision energy while keeping the target g as pressure constant. The collision energy at which these two most abu ndant product ions are equal is defined as the calibration point at th at collision gas pressure. LSIMS tandem mass spectra acquired at the c alibration point show good reproducibility for several model compounds . Spectra obtained at the calibration point at two different collision gas pressures, representing multiple and single collision conditions, also show a high degree of similarity. Use of this protocol may aid i n the establishment of a tandem mass spectral library.