Nondestructive tandem mass spectrometry using a linear quadrupole ion trap coupled to a linear electrostatic ion trap.

A novel hybrid tandem mass spectrometer is presented that combines a linear quadrupole ion trap (QLIT) with a linear electrostatic ion trap (ELIT), which is composed of opposing ion mirrors. The QLIT is used both as an accumulation device for the pulsed injection of ions into the ELIT and as a collision cell for ions released from the ELIT and back into the QLIT. Ions are subjected to mass analysis in the ELIT via Fourier transformation of the time-domain signal obtained from an image current measurement using a pick-up electrode in the field-free region of the ELIT. The nondestructive nature of ion detection and the relatively straightforward axial entrance and exit of ions into and from the ELIT allow for the execution of nondestructive tandem mass spectrometry experiments whereby both the initial mass spectrum and the product ion spectrum are obtained on the same initial ion population. The timed pulsing of a deflection electrode, in conjunction with the release of ions from the ELIT, allows for the selection of precursor ions for recapture by the QLIT. The transfer of ions back and forth between the QLIT and ELIT is illustrated with Cs ions, the selection of precursor ions is demonstrated with isotopes of tetraoctylammonium cations, and complete nondestructive tandem mass spectrometry experiments are demonstrated with a mixture of angiotensin II and bradykinin cations. With the current apparatus, the efficiency for the process of recapturing ions and then reinjecting them into the ELIT is 35%-40%. The instrument is capable of isolating an ion from a neighbor with a mass as close as 1 part in 500, with negligible loss of the desired species.