In particular, the droplets or ions are entrained in a background gas and transported from the ion source through an ion transfer tube that passes through a first partition element or wall a into an intermediate-vacuum chamber which is maintained at a lower pressure than the pressure of the ionization chamber but at a higher pressure than the pressure of the high-vacuum chamber The ion transfer tube may be physically coupled to a heating element or block that provides heat to the gas and entrained particles in the ion transfer tube so as to aid in desolvation of charged droplets so as to thereby release free ions.
Frontmatter - Quadrupole Ion Trap Mass Spectrometry - Wiley Online Library
Due to the differences in pressure between the ionization chamber and the intermediate-vacuum chamber FIG. A second plate or partition element or wall b separates the intermediate-vacuum chamber from a second intermediate-pressure region , likewise a third plate or partition element or wall c separates the second intermediate pressure region from the high-vacuum chamber A first ion optical assembly a provides an electric field that guides and focuses the ion stream leaving ion transfer tube through an aperture in the second partition element or wall b that may be an aperture of a skimmer A second ion optical assembly b may be provided so as to transfer or guide ions to an aperture in the third plate or partition element or wall c and, similarly, another ion optical assembly c may be provided in the high vacuum chamber containing the mass analyzer The ion optical assemblies or lenses a - c may comprise transfer elements, such as, for instance a multipole ion guide, so as to direct the ions through aperture and into the mass analyzer The mass analyzer comprises one or more detectors whose output can be displayed as a mass spectrum.
Vacuum ports a , b and c may be used for evacuation of the various vacuum chambers. Such controller may be implemented in any suitable form, such as one or a combination of specialized or general purpose processors, field-programmable gate arrays, and application-specific circuitry. In operation, the controller effects desired functions of the mass spectrometer system e. The controller may be additionally configured to store and run data-dependent methods in which output actions are selected and executed in real time based on the application of input criteria to the acquired mass spectral data.
The data-dependent methods, as well as the other control and data analysis functions, will typically be encoded in software or firmware instructions executed by the controller.
As illustrated in FIG. The mass analyzer may be implemented as a quadrupole ion trap. Various modes of operation are known. In other modes of operation, the first quadropole device is operated as an ion filter which transmits only ions of certain mass-to-charge ratio or ratios to the second quadrupole device.
In many modes of operation, the second quadrupole device is employed as a fragmentation device which causes collision induced fragmentation of the selected precursor ions through interaction with molecules of an inert collision gas introduced through tube The precursor or fragment ions are transmitted from the second quadrupole device to the third quadrupole device for mass analysis of the various ions. As discussed above, mass spectrometer system FIG. The accurate-mass mass analyzer preferably is capable of at least 5 ppm accuracy and, even more preferably, is capable of at least 1 ppm accuracy.
In such instances, either precursor or product ions that are analyzed or produced in the triple-quadrupole component may be passed to the accurate-mass mass analyzer system. The accurate-mass mass analyzer system may then be employed to perform further or alternative analyses on the passed-through ions.
US9048074B2 - Multinotch isolation for MS3 mass analysis - Google Patents
The single mass spectrometer system may also include a different type of fragmentation or reaction cell within which the passed-through ions may be further fragmented or manipulated. The ion source, , ionization chamber , ion transfer tube , heating element or block and skimmer are as described previously in regard to FIG. The ions are transported from ionization chamber , which for an electrospray source will typically be held at or near atmospheric pressure, through several intermediate chambers , and of successively tower pressure, to a vacuum chamber in which differential-pressure dual ion trap mass analyzer resides.
Efficient transport of ions from ion source to mass analyzer is facilitated by a number of ion optic components, including quadrupole RF ion guides and , octopole RF ion guide , skimmer , and electrostatic lenses and Ions may be transported between ionization chamber and the first intermediate chamber through the ion transfer tube Intermediate chambers , and and vacuum chamber are evacuated by a suitable arrangement of pumps connected to vacuum ports a - d to maintain the pressures therein at the desired values.
Dual ion trap mass analyzer includes first and second quadrupole traps and positioned adjacent to one another. For reasons that will become evident in view of the discussion set forth below, first quadrupole ion trap will be referred to as the high-pressure trap HPT , and second quadrupole ion trap will be referred to as the low-pressure trap LPT. Generally described, a two-dimensional quadrupole ion trap may be constructed from four rod electrodes disposed about the trap interior. The rod electrodes are arranged into two pairs, each pair being opposed across the central longitudinal axis of the trap.
Quadrupole ion trap mass spectrometry.
In order to closely approximate a pure quadrupole field when the RF voltages are applied, each rod is formed with a truncated hyperbolic surface facing the trap interior. In other implementations, round circular or even planar flat electrodes can be substituted for the hyperbolic electrodes. In some implementations, each rod electrode is divided into three electrically isolated sections, consisting of front and back end sections flanking a central section.
Sectioning of the rod electrodes allows the application of different DC potentials to each of the sections, such that ions may be primarily contained within a volume extending over a portion of the length of the trap. For example, positive ions may be concentrated within a central volume of the trap interior which is roughly longitudinally co-extensive with the central sections of the rod electrodes by raising the DC potential applied to the end sections relative to the central sections. A generally tubular enclosure engages and seals to front lens , inter-trap lens and back lens to form an enclosure for HPT and LPT This arrangement enables the development of the desired pressures within HPT and LPT by restricting communication between the two traps and between each trap and the exterior region to flows occurring through the various apertures.
Enclosure may be adapted with elongated apertures to permit passage of ejected ions to detectors A buffer gas, typically helium, is added to the interior of HPT via a conduit that penetrates sidewall The pressures that are maintained within HPT and LPT will depend on the buffer gas flow rate, the sizes of lens apertures , and , the pressure of vacuum chamber , the construction of enclosure including any apertures formed therein and the associated pumping speed of the pumping port for vacuum chamber Broadly described, therefore, the mass spectrometer includes a dual-trap mass analyzer.
The dual-trap mass analyzer includes adjacently disposed first and second two-dimensional quadrupole ion traps operating at different pressures. The first ion trap has an interior volume maintained at a relatively high pressure, for example in the range of 5. The cooled and optionally fragmented ions are transferred through at least one ion optic element to the interior of the second ion trap, which is maintained at a significantly lower buffer gas pressure for example, in the range of 1.
In addition, the lower pressure region also allows the possibility of higher resolution ion isolation. The dual-trap mass analyzer of the mass spectrometer system may be operated in a number of different modes.
In another mode, ions are trapped and cooled in the first trap, and precursor ions are selected isolated for fragmentation by ejecting from the first trap all ions outside of a mass-to-charge range of interest. In accordance with the CID technique, the precursor ions are then kinetically excited and undergo energetic collisions with the buffer gas to produce product ions. The product ions are then transferred to the second ion trap for mass analysis. Yet another mode of operation makes use of the potential for high-resolution isolation in the second ion trap.
In this mode, ions are trapped and cooled in the first ion trap and then transferred into the second ion trap. Precursor ions are then isolated in the second ion trap by ejecting all ions outside of a mass-to-charge range of interest.
Due to the low pressure within the second ion trap, isolation may be effected at higher resolution and greater efficiency less loss of precursor ions than is attainable at higher pressures, so that precursor ion species may be selected with greater specificity. The precursor ions are then transferred back into the first ion trap and are thereafter fragmented by the aforementioned CID technique. The resulting product ions are then transferred into the second ion trap for mass analysis.
Other known dissociation or reaction techniques, including without limitation photodissociation, electron transfer dissociation ETD , electron capture dissociation ECD , and proton transfer reactions PTR may be used in place of or in addition to the CID technique to yield product ions. The product ions may then be transferred back into the second ion trap for mass analysis. The dual-trap mass analyzer of the mass spectrometer system FIG. The accurate-mass mass analyzer is preferably is capable of at least 5 ppm accuracy and, even more preferably, is capable of at least 1 ppm accuracy.
In such instances, either precursor or product ions that are analyzed or produced in the dual-trap mass analyzer may be passed to the accurate-mass mass analyzer system. An example of a generalized mass spectrometer system on which the invention according to some of its aspects may be practiced is shown in FIG. Analyte material is provided to an ion source so as to generate ions The ions are admitted to a first mass analyzer MS 1 that has mass analysis and mass selection functionality and in which, optionally, fragmentation may be performed.
For instance, the first mass analyzer MS 1 may comprise an ion trap or quadrupole mass analyzers. In addition, multiple ion sources may be used. It is to be noted that, in the system , ions are transferred from one component to the next via ion optics e. RF multipoles which, in some cases, are not specifically illustrated.
An automatic gain control AGC detector may be provided in the mass spectrometer system to quantitatively measure or sample an ion flux or number of ions for purposes of controlling the number of ions in a subsequent ion population. Any of the known AGC methods may be used to determine the optimum ionization time for fills of the downstream intermediate ion storage or the accurate-mass mass analyzer MS 2 Otherwise, ions are transferred from MS 1 along path a to the intermediate ion storage Still with reference to the system shown in FIG. The intermediate ion store may comprise, for instance, an ion trap device.
Ions released from the intermediate ion store may be transferred along path to an accurate-mass mass analyzer MS 2 The accurate-MS may receive, for analysis, either unfragmented precursor ions, a set of ions formed by fragmentation of a single selected precursor ion, or a mixture of a plurality of sets of ions, each such set formed by fragmentation of a different respective precursor ion. With reference to the systems illustrated herein, ions produced using the optimum ionization time may be fragmented in either the first mass analyzer or a separate reaction cell , for example, by collision-induced dissociation.
A controller , which may comprise a general purpose computer or, perhaps, a specialized electronic logic device, is electronically coupled to other components along electronic control lines The electronic control lines may send control signals from the controller to the mass spectrometers, intermediate ion storage device, ion source, the various ion optics, etc.
For instance, the controller may send signals to set potentials on the electrodes of the various parts at the various appropriate times. The electronic control lines may also transmit signals from one or more of the components of the system back to the controller For instance, the controller may receive signals from the AGC detector and from the accurate-mass MS , such signals relating to number of ions detected. The system shown in FIG. In a first mode of operation, selected ions are delivered along pathway a from MS 1 to the intermediate ion storage device where they are trapped.
Once a suitable time delay has passed, the controller may cause the ions to be transported to the reaction cell for fragmentation or other manipulation so as to produce fragment or product ions. The intermediate ion store may have a gas introduced therein, thereby reducing the energy of the ions through collisional cooling as they pass through the intermediate ion store and enter the reaction cell Precursor ions or pre-existing fragments may be fragmented in the reaction cell Pre-existing fragments may be produced, for instance, in MS 1 Ion fragmentation may be effected by any suitable fragmentation technique, such as collision-induced dissociation CID.
The resulting fragment ions if any or precursor ions if any are then transferred, in the opposite direction, back along path b from the reaction cell to the intermediate ion storage device After storage in the intermediate ion storage device for an appropriate time, these fragment ions are transferred to the accurate-mass MS for analysis along pathway Multiple fills of the accurate-mass MS may be formed using different respective processing techniques for instance, high energy versus low energy fragmentation in the reaction cell The flexibility provided by these various operation options provides the capability of performing both precursor ion as well as fragment ion analyses using the accurate-mass MS.
The mass spectrometer system shown in FIG. In the illustrated system, ions provided by ion source are transferred to one or more evacuated chambers enclosed by housing The ions are transferred or guided by ion optics not shown so as to be admitted to a first mass analyzer system The mass analyzer system may comprise one or more stages of any of mass filters, collision or reaction cells, ion traps or detectors.
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- Quadrupole ion trap.
- Global Positioning System: An Overview: Symposium No. 102 Edinburgh, Scotland, August 7–8, 1989?
- Development of an ion trap mass spectrometer for elemental analysis - UBC Library Open Collections.
- Quadrupole Ion Trap Mass Spectrometry.
The mass analyzer system may thus comprise may comprise mass analysis or mass selection functionality and may, optionally, provide the capability to perform collision induced fragmentation of precursor ions so as to produce a first generation of fragment ions. Accordingly, the mass analyzer system may provide all the functionality of either the mass spectrometer system FIG.
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