Operation of a hybrid tandem mass spectrometer of BEqQ configuration in scan modes using uncoupled analysers

Abstract

Experimental methods are described for a tandem BEqQ instrument, which permit exploitation of the unit-mass resolution of the quadrupole mass filter, Q, in conjunction with desirable characteristics of collisionally activated reactions at keV energies. Existing methods require appropriate linked-scans of Q with the electric sector field, E. These linked-scans are difficult to generate accurately over wide scan ranges and, in any case, are inappropriate for cases in which large organic ions suffer appreciable energy-loss shifts upon collisional activation. The present method exploits the properties of Q as a true mass filter. The mass assignments of the fragment-ion peaks thus obtained are wholly independent of any energy shift and the experimental procedure requires absolutely no linkage of E and Q. Problems of reduced absolute sensitivity, encountered in the present exploratory experiments, are described. In addition, a related procedure is described which permits disentangling grand-daughter spectra from a mass-selected parent ion, arising via several daughter ions formed by high-energy CID and thus poorly resolved from one another.