Abstract: In the field of mass spectrometry, a method and apparatus for fragmenting ions with a relatively high degree of resolution and efficiency. The technique includes trapping the ions in a linear ion trap, in which the background or neutral gas pressure is preferably on the order of 10-5 Torr. The trapped ions are resonantly excited for a relatively extended period of time, e.g., exceeding 50 ms, at relatively low excitation levels, e.g., less than 1 Volt (0-pk). The technique allows selective dissociation of ions with a high discrimination. High fragmentation efficiency may be achieved by superimposing a higher order multipole field onto the quadrupolar RF field used to trap the ions. The multipole field, preferably an octopole field, dampens the radial oscillatory motion of resonantly excited ions at the periphery of the trap. This reduces the probability that ions will eject radially from the trap thus increasing the probability of collision induced dissociation.

Abstract: The invention solves the problem of artifact ghost peaks which can sometimes arise in mass spectrometers that employ a quadrupole rod set for both trapping and mass analyzing the trapped ions. The problem arises as a result of randomly distributed voltage gradients along the length of the rods. Three solutions are presented. The first approach involves improving the conduction characteristics of the rod sets. The second approach involves the application of at least one continuous axial DC field to the trapping quadrupole rod set in order to urge ions towards a pre-determined region of the trap, thereby avoiding voltage gradients. The third approach involves the application of one or more discrete axial fields to create one or more potential barriers along the axial dimension of the trap (in addition to the barriers used to initially trap the ions). These barriers prevent ions of differing voltage gradients from equilibrating with one another.

Abstract: A method of and apparatus for analyzing a stream of ions first subjects astream of ions to a first mass analysis step, to select ions having a mass-to-charge ratio in a first desired range; this enables a mass analyzer with highresolution to be used. The selected ions are then passed into a radiofrequency linear ion trap containing a gas. The trapped ions are caused to collide with the gas, either by being injected with a high axial energy or by application of external excitation to cause fragmentation. Fragment ions of a given mass-to-charge ratio can then be isolated and excited to produce fragments of fragments. This process can be repeated to give multiple steps of mass spectrometry, MSn. The fragment ions, and undissociated precursorions are then passed out of the linear ion trap and subjected to a further mass analysis step, for example in a time of flight device, to determine the mass spectrum of the ions.

Abstract: An improved method of operating a mass spectrometer having a linear ion trap wherein ions are axially ejected from the trap to a detector or subsequent mass analysis stage. The DC barrier field produced at the exit lens of the trap is scanned in conjunction with the scanning of other fields used to energize ions of select mass-to-charge ratios past the barrier field/exit lens. The technique can maximize the resolution obtainable from axial ejection over a wide mass range.

Abstract: The invention solves the problem of artifact ghost peaks which can sometimes arise in mass spectrometers that employ a quadrupole rod set for both trapping and mass analyzing the trapped ions. The problem arises as a result of randomly distributed voltage gradients along the length of the rods. Three solutions are presented. The first approach involves improving the conduction characteristics of the rod sets. The second approach involves the application of at least one continuous axial DC field to the trapping quadrupole rod set in order to urge ions towards a pre-determined region of the trap, thereby avoiding voltage gradients. The third approach involves the application of one or more discrete axial fields to create one or more potential barriers along the axial dimension of the trap (in addition to the barriers used to initially trap the ions). These barriers prevent ions of differing voltage gradients from equilibrating with one another.

Abstract: An improved method of operating a mass spectrometer having a linear ion trap wherein ions are axially ejected from the trap to a detector or subsequent mass analysis stage. The DC barrier field produced at the exit lens of the trap is scanned in conjunction with the scanning of other fields used to energize ions of select mass-to-charge ratios past the barrier field/exit lens. The technique can maximize the resolution obtainable from axial ejection over a wide mass range.

Abstract: In the field of mass spectrometry, a method and apparatus for fragmenting ions with a relatively high degree of resolution. The technique includes trapping the ions in an ion trap, preferably a linear ion trap, in which the background or neutral gas pressure is preferably on the order of 10−5 Torr. The trapped ions are resonantly excited for a relatively extended period of time, e.g., exceeding 50 ms, at relatively low excitation levels, e.g., less than 1V(0−pk). The technique allows selective dissociation of ions with a discrimination of at least about 1 m/z at a practical fragmentation efficiencies. Apparatus and related methods are also disclosed for obtaining MS, MS2, MS3 and MSn spectrums at relatively high resolutions using the low pressure fragmentation technique.

Abstract: In the field of mass spectrometry, a method and apparatus for fragmenting ions with a relatively high degree of resolution and efficiency. The technique includes trapping the ions in a linear ion trap, in which the background or neutral gas pressure is preferably on the order of 10−5 Torr. The trapped ions are resonantly excited for a relatively extended period of time, e.g., exceeding 50 ms, at relatively low excitation levels, e.g., less than 1 Volt(0-pk). The technique allows selective dissociation of ions with a high discrimination. High fragmentation efficiency may be achieved by superimposing a higher order multipole field onto the quadrupolar RF field used to trap the ions. The multipole field, preferably an octopole field, dampens the radial oscillatory motion of resonantly excited ions at the periphery of the trap. This reduces the probability that ions will eject radially from the trap thus increasing the probability of collision induced dissociation.

Abstract: A method is provided of operating a mass spectrometer apparatus comprising a pair of quadrupole rod sets. Each quadrupole rod set is operated in a mass resolving mode. They may be operated in the same or different stability regions. The rod sets are operated to select essentially ions of the same mass to charge ratio, and are operated such that the combined resolution of the two rod sets is greater than the resolution of either rod set. The rod sets can be operated at relatively low resolution, with the combined peak shape from the two rod sets showing high resolution. This can make up for mechanical imperfections in the rod sets, losses due to high gas pressures, etc. A mass shift can be provided to give the desired resolution. The rod sets can be close coupled, and for this purpose neutralizing capacitors can be provided to prevent electrical interference between adjacent rod sets.

Abstract: A method and apparatus are provided for determining rates and mechanisms of reactions in solution. The method comprises mixing reactants together and then passing the reactants, after mixing, to an electrospray or other ion source. The apparatus is configured so that the reaction time can be determined. This can either be by way of a capillary of known length and volume extending from a reaction tee or other mixing device, so that the reaction time can be determined from the capillary volume and flow rate, and/or by way of a container of fixed volume from which the reactants pass. From the ion source, ions pass into a mass spectrometer, where a mass spectrum is measured. By varying the reaction time, and measuring the different mass spectra, the rate of reaction can be determined.