The invention provides methods and apparatus for tandem mass spectrometry (MS/MS) in which parent ions generated from a sample are passed through a mass filter (2) and are fragmented into daughter ions in fragmentation means (3), the daughter ions being passed through a discontinuous output mass analyser, such as a time-of-flight analyzer (16) or an ion storage device (29). The range of possible parent mass-to-charge ratios is split into a plurality of smaller ranges, and the mass filter (2) is set to pass ions of each smaller range in turn. A flag is set for each smaller range which produces daughter ions of interest, and the mass filter (2) is set to pass each mass-to-charge ratio of the flagged ranges so that the mass-to-charge ratios of the fragmented ions produced for each of the mass-to-charge ratios passed may be determined using the discontinuous analyser (16, 29). The flagged ranges may be themselves split into a plurality of still smaller ranges, which are correspondingly flagged.
A method for enhancing the dynamic range of a mass spectrometer by first passing a sample of ions through the mass spectrometer having a quadrupole ion filter, whereupon the intensities of the mass spectrum of the sample are measured. From the mass spectrum, ions within this sample are then identified for subsequent ejection. As further sampling introduces more ions into the mass spectrometer, the appropriate rf voltages are applied to a quadrupole ion filter, thereby selectively ejecting the undesired ions previously identified. In this manner, the desired ions may be collected for longer periods of time in an ion trap, thus allowing better collection and subsequent analysis of the desired ions. The ion trap used for accumulation may be the same ion trap used for mass analysis, in which case the mass analysis is performed directly, or it may be an intermediate trap. In the case where collection is an intermediate trap, the desired ions are accumulated in the intermediate trap, and then transferred to a separate mass analyzer. The present invention finds particular utility where the mass analysis is performed in an ion trap mass spectrometer or a Fourier transform ion cyclotron resonance mass spectrometer.
A main object is to cope with an unknown structure substance thereby to identify the structure of a parent ion highly precisely and to derive a supposed structure. A method for analyzing mass spectrometric data is disclosed, which: acquires mass spectrometric data on an ionized sample and dissociated ions dissociated from the sample as a parent ion; derives dissociated ion candidates by analyzing the molecular orbits on the candidates of the structures of the parent ion; and displays the analytical results of the parent ion candidates and the dissociated ion candidates and compares the data of the dissociated ion candidates and the data of dissociated ions actually measured, to evaluate the structures of the parent ion candidates.
An improved method of parent ion scanning is disclosed. In one embodiment a quadrupole mass filter 3 upstream of a collision cell 4 is arranged to operate in a highpass mode. Parent ions transmitted by the mass filter 3 are fragmented in the collision cell 4 and detected by an orthogonal time of flight analyser 5 which obtains a daughter ion mass spectrum. Ions having a mass to charge ratio below the cutoff of the mass filter 3 are identified as daughter ions, and candidate parent ions may then be discovered and their identity confirmed by obtaining corresponding daughter ion spectra. In a second embodiment, the collision cell 4 alternates between high and low fragmentation and candidate parent ions can additionally be identified on the basis of the loss of a predetermined ion or neutral particle.
A method is disclosed of identifying parent ions by matching daughter ions found to be produced at substantially the same time that the parent ions elute from a mixture. Ions emitted from an ion source are incident upon a collision cell which alternately and repeatedly switches between a first mode wherein the ions are substantially fragmented to produce daughter ions and a second mode wherein the ions are not substantially fragmented. Mass spectra are taken in both modes, and at the end of an experimental run parent and daughter ions are recognized by comparing the mass spectra obtained in the two different modes. Daughter ions are matched to particular parent ions on the basis of the closeness of fit of their elution times, and this enables parent ions to then be identified.
A ring pole ion guide apparatus and method provide the focusing and confinement advantages of conventional multipoles and the axial field of a conventional DC ring guide all in one device. The ring pole apparatus comprises a ring stack portion and a multipole portion, wherein the ring stack portion essentially overlaps the multipole portion inside and outside along a central axis. The ring pole apparatus can be used in a mass spectrometer system to guide ions from the ion source to the mass spectrometer or between mass spectrometer stages, or to dissociate ions into daughter ions in an ion dissociation system. A single ring pole ion guide can span a plurality of pressure transition stages with several of the rings acting as pressure partitions.
