Patent Application
20210407787
The present disclosure relates generally to charge detection mass spectrometry instruments, and more specifically to performing mass and charge measurements with such instruments.
Mass Spectrometry provides for the identification of chemical components of a substance by separating gaseous ions of the substance according to ion mass and charge. Various instruments and techniques have been developed for determining the masses of such separated ions, and one such technique is known as charge detection mass spectrometry (CDMS). In CDMS, ion mass is determined as a function of measured ion mass-to-charge ratio, typically referred to as “m/z,” and measured ion charge.
High levels of uncertainty in m/z and charge measurements with early CDMS detectors has led to the development of an electrostatic linear ion trap (ELIT) detector in which ions are made to oscillate back and forth through a charge detection cylinder. Multiple passes of ions through such a charge detection cylinder provides for multiple measurements for each ion, and it has been shown that the uncertainty in charge measurements decreases with n1/2, where n is the number of measurements. However, in the continued quest for greater measurement resolution, the ELIT remains limited by uncertainties in both m/z measurements and charge measurements. Accordingly, it is desirable to seek improvements in ELIT design and/or operation which further reduce measurement uncertainties for either or both of ion charge and mass-to-charge ratio (m/z).
The present disclosure may comprise one or more of the features recited in the attached claims, and/or one or more of the following features and combinations thereof. In a first aspect, an electrostatic linear ion trap may comprise a first ion mirror defining a first axial passageway therethrough, a second ion mirror defining a second axial passageway therethrough, a charge detection cylinder defining a third axial passageway therethrough, the charge detection cylinder positioned between the first and second ion mirrors such that the first, second and third axial passageways are in-line with each other, and at least one voltage source coupled to the first and second ion mirrors, the at least one voltage source configured to establish electric fields in each of the first and second ion mirrors configured to reflect an ion entering a respective one of the first and second axial passageways from the third axial passageway of the charge detection cylinder back through the third axial passageway of the charge detection cylinder and toward the other of the first and second axial passageways such the ion oscillates back and forth through the charge detection cylinder between the first and second ion mirrors with a duty cycle, corresponding to a ratio of time spent by the ion in the third axial passageway of the charge detection cylinder and total time spent traversing a combination of the first and second ion mirrors and the charge detection cylinder during one complete oscillation cycle, of approximately 50%.
In a second aspect, an electrostatic linear ion trap may comprise a first ion mirror defining a first axial passageway therethrough, a second ion mirror identical to the first ion mirror and defining a second axial passageway therethrough identical to the first axial passageway defined through the first ion mirror, a charge detection cylinder defining a third axial passageway therethrough, the charge detection cylinder positioned between the first and second ion mirrors such that the first, second and third axial passageways are in-line with each other, and at least one voltage source coupled to the first and second ion mirrors, the at least one voltage source configured to establish electric fields in each of the first and second ion mirrors configured to reflect an ion entering a respective one of the first and second axial passageways from the third axial passageway of the charge detection cylinder back through the third axial passageway of the charge detection cylinder and into the other of the first and second axial passageways such the ion oscillates back and forth through the charge detection cylinder between the first and second ion mirrors with a time spent by the ion passing each time through the charge detection cylinder approximately equal to a sum of time spent by the ion travelling from a stopped position within one of the first and second ion passageways into a respective end of the charge detection cylinder and time spent by the ion traveling from an opposite respective end of the charge detection cylinder to a stopped position within the other of the first and second ion passageways.
In a third aspect, a method is provided for operating an electrostatic linear ion trap having first and second ion mirrors separated by a charge detection cylinder, wherein each of the first and second ion mirrors and the charge detection cylinder axially aligned with one another. The method may comprise establishing a first electric field in the first ion mirror, the first electric field configured and oriented to stop in the first ion mirror an ion exiting a first end of the charge detection cylinder proximate to the first ion mirror and traveling into the first ion mirror, and to accelerate the stopped ion in the first ion mirror back into the first end of the charge detection cylinder, and establishing a second electric field in the second ion mirror, the second electric field configured and oriented to stop in the second ion mirror an ion exiting a second end of the charge detection cylinder, opposite the first end thereof, proximate to the second ion mirror and traveling into the second ion mirror, and to accelerate the stopped ion in the second ion mirror back into the second end of the charge detection cylinder, such that the at least one ion oscillates through the charge detection cylinder back and forth between the first and second ion mirrors under the influence of the first and second electric fields, wherein the first and second electric fields are established such that time spent by the at least one ion passing through the charge detection cylinder during each oscillation cycle is approximately equal to a sum of time spent in each of the first and second ion mirrors.
In a fourth aspect, a method is provided for operating an electrostatic linear ion trap having first and second ion mirrors separated by a charge detection cylinder, wherein each of the first and second ion mirrors and the charge detection cylinder axially aligned with one another. The method may comprise establishing a first electric field in the first ion mirror, the first electric field configured and oriented to stop in the first ion mirror an ion exiting a first end of the charge detection cylinder proximate to the first ion mirror and traveling into the first ion mirror, and to accelerate the stopped ion in the first ion mirror back into the first end of the charge detection cylinder, and establishing a second electric field in the second ion mirror, the second electric field configured and oriented to stop in the second ion mirror an ion exiting a second end of the charge detection cylinder, opposite the first end thereof, proximate to the second ion mirror and traveling into the second ion mirror, and to accelerate the stopped ion in the second ion mirror back into the second end of the charge detection cylinder, such that the at least one ion oscillates through the charge detection cylinder back and forth between the first and second ion mirrors under the influence of the first and second electric fields, wherein the first and second electric fields are established such that the ion oscillates back and forth through the charge detection cylinder between the first and second ion mirrors with a duty cycle, corresponding to a ratio of time spent by the ion in the third axial passageway of the charge detection cylinder and total time spent traversing a combination of the first and second ion mirrors and the charge detection cylinder during one complete oscillation cycle, of approximately 50%
In a fifth aspect, a system for separating ions may comprise an ion source configured to generate ions from a sample, at least one ion separation instrument configured to separate the generated ions as a function of at least one molecular characteristic, and the electrostatic linear ion trap as described in any of the first through fourth aspects, wherein one of the first and second ion mirrors defines an aperture configured to allow passage of at least one ion exiting the at least one ion separation instrument into the one of the first and second ion mirrors for oscillation thereof back and forth through the charge detection cylinder between the first and second ion mirrors.
In a sixth aspect, a system for separating ions may comprise an ion source configured to generate ions from a sample, a first mass spectrometer configured to separate the generated ions as a function of mass-to-charge ratio, an ion dissociation stage positioned to receive ions exiting the first mass spectrometer and configured to dissociate ions exiting the first mass spectrometer, a second mass spectrometer configured to separate dissociated ions exiting the ion dissociation stage as a function of mass-to-charge ratio, and a charge detection mass spectrometer (CDMS), including the electrostatic linear ion trap as described in any of the first through fourth aspects, coupled in parallel with and to the ion dissociation stage such that the CDMS can receive ions exiting either of the first mass spectrometer and the ion dissociation stage, wherein masses of precursor ions exiting the first mass spectrometer are measured using CDMS, mass-to-charge ratios of dissociated ions of precursor ions having mass values below a threshold mass are measured using the second mass spectrometer, and mass-to-charge ratios and charge values of dissociated ions of precursor ions having mass values at or above the threshold mass are measured using the CDMS.
For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to a number of illustrative embodiments shown in the attached drawings and specific language will be used to describe the same.
Referring to
In the illustrated embodiment, the ion mirror M1 includes three spaced-apart, electrically conductive mirror electrodes ME1-ME3 with a plate or cover PL1 over the exposed face of the electrode ME1. The plate or cover PL1 defines an aperture A1 centrally therethrough which serves as an ion entrance to the ELIT 10. The spaces S1, S2 between the electrodes ME1, ME2 and ME2, ME3 respectively may be voids in some embodiments, and in other embodiments the spaces S1, S2 may be filled with one or more electrically non-conductive, e.g., dielectric, materials. The mirror electrodes ME1-ME3 are each illustratively of thickness D1 and define a cylindrical passageway therethrough of diameter P1. The mirror electrodes ME1-ME3 are axially aligned such that a longitudinal axis C passes centrally through each aligned cylindrical passageway and also centrally through the aperture A1. In embodiments in which the spaces S1, S2 include one or more electrically non-conductive materials, such materials will likewise define respective passageways therethrough which are axially aligned with the cylindrical passageways defined through the mirror electrodes ME1-ME3 and which have diameters of P1 or greater. In any case, the spaces S1, S2 each illustratively define a length d1 between opposing faces of the respective mirror electrodes ME1-ME3 such that the axial length, AL1, of the ion mirror M1 is AL1=3D1+2d1. The ion entrance A1 defined through the plate or cover PL1 illustratively has a diameter P2.
Another ion mirror M2 includes mirror electrodes ME4, ME5 and ME6 substantially identical in arrangement, construction and dimensions to the mirror electrodes ME1, ME2 and ME3 respectively of the ion mirror M1 as described above, and is spaced apart from the ion mirror M1 such that the distal face of the mirror electrode ME3 faces the distal face of the mirror electrode ME4. A plate or cover PL2 is disposed over the exposed face of the electrode ME6 of the ion mirror M2, and the plate or cover PL2 defines an aperture A2 centrally therethrough, also illustratively of diameter P2, which serves as an ion exit from the ELIT 10. The longitudinal axis C extends centrally through the passageways defined by the mirror electrodes ME4-ME6 and spaces S1, S2 of the mirror electrode M2 as illustrated in
A charge detector CD in the form of an electrically conductive cylinder of length D3 is positioned between the spaced apart ion mirrors M1, M2. The charge detection cylinder CD illustratively defines a cylindrical passageway axially therethrough of diameter P3, and the charge detection cylinder CD is oriented relative to the ion mirrors M1, M2 such that the longitudinal axis C extending centrally through the passageways defined through the ion mirrors M1, M2 also extends centrally through the passageway defined through the charge detection cylinder CD. In some embodiments, as illustrated by example in
The total axial length, TL, of the ELIT 10, not including the end plates or covers PL1, PL2, is TL=6D1+2D2+D3+6d1+2d2. In one specific example embodiment, the various dimensional parameters described above may have the numerical values set forth in the following TABLE I, although it will be understood that such numerical values are provided only by way of example and should not be considered limiting in any way.
Although the mirror electrodes ME1-ME6 of the ion mirrors M1, M2 are illustrated in
Referring now to
The charge detection cylinder CD is electrically connected to a signal input of a conventional charge pre-amplifier 16 (CP) having a signal output electrically connected to the processor 12. As an ion within the ELIT 10 oscillates back and forth between the ion mirrors M1, M2 as briefly described above, it passes each time through the charge detection cylinder CD where it induces at least a portion of its charge onto the charge detection cylinder CD. The charge pre-amplifier 16 is illustratively responsive to each such induced charge detected at its input to produce a corresponding amplified charge detection signal which is provided as an input to the processor 12. The processor 12 is illustratively operable to receive and digitize such charge detection signals produced by the charge pre-amplifier 16, and to store the digitized charge detection signals in the memory 14. The processor 12 is further illustratively coupled to one or more peripheral devices 18 for providing signal input(s) to the processor 12 and/or to which the processor 12 provides signal output(s). In some embodiments, the peripheral devices 18 include at least one of a conventional display monitor, a printer and/or other output device, and the memory 14 has instructions stored therein which, when executed by the processor 12, cause the processor 12 to control one or more such output peripheral devices 18 to display and/or record analyses of the stored, digitized charge detection signals. In some embodiments, a conventional microchannel plate detector 20 may be disposed at the ion outlet of the ELIT 10 and electrically connected to the processor 12 as shown by dashed-line representation in
As further illustrated in
In the example embodiment illustrated in
Referring now to
With reference to
Following step 102, the process 100 advances to step 104 where the processor 12 is operable to pause and determine when to advance to step 106. In one embodiment, the processor 12 is operable at step 104 to pause for a predefined or programmable time period to allow ions exiting the ion source 25 to enter and pass through the ELIT 10. As one non-limiting example, the selected time period which the processor 12 spends at step 104 before moving on to step 106 is on the order of 1 millisecond (ms), although it will be understood that such selected time period may, in other embodiments, be greater than 1 ms or less than 1 ms. Until the selected time period has elapsed, the process 100 follows the NO branch of step 104 and loops back to the beginning of step 104. After passage of the selected time period, the process 100 follows the YES branch of step 104 and advances to step 106. In some alternate embodiments of step 104, such as in embodiments which include the microchannel plate detector 20, the processor 12 may be operable to control the voltage sources V1-V6 to hold the ion mirrors M1, M2 in their transmission modes until at least one ion 30 is detected at the microchannel plate detector 20. Until such detection, the process 100 follows the NO branch of step 104 and loops back to the beginning of step 104.
Following the YES branch of step 104, the processor 12 is operable at step 106 to control the voltage sources V4-V6 to set the output voltages VO4-VO6 in a manner which changes or switches the operation of the ion mirror M2 from transmission mode of operation to a “reflection mode” of operation in which the ion mirror M2 operates to “reflect” an ion contained therein back toward the ion mirror M1 (and through the charge detector CD) by first decelerating and stopping the ion, and then accelerating the ion back in the opposite direction while focusing the ion toward the longitudinal axis C such that the ion passes in a narrow trajectory about the longitudinal axis C from the ion mirror M2 back toward the ion mirror M1. Illustratively, the output voltages VO4-VO6 produced by the voltage sources V4-V6 respectively are controlled by the processor 12 at step 106 to establish a net “reflection” electric field EN3 in the ion mirror M2 oriented to reflect the ion 30 entering therein from the charge detector CD back toward the ion mirror M1 (and through the charge detector CD) as illustrated by example in
In one embodiment of step 108, the ELIT 10 is illustratively controlled in a “random trapping mode” in which the ion mirror M2 is held in the reflection mode and the ion mirror M1 is held in the transmission mode for a selected time period as one or more ions 30 enter the ion mirror M1 from the ion source 25. As one non-limiting example, the selected time period which the processor 12 spends at step 108 before moving on to step 110 is on the order of 1 millisecond (ms), although it will be understood that such selected time period may, in other embodiments, be greater than 1 ms or less than 1 ms. Until the selected time period has elapsed, the process 100 follows the NO branch of step 108 and loops back to the beginning of step 108. After passage of the selected time period, the process 100 follows the YES branch of step 108 and advances to step 110.
In some alternate embodiments of step 108, the ELIT 10 may illustratively be controlled by the processor 12 in a first version of a “trigger trapping mode” in which the ion mirror M1 is held in the transmission mode and the ion mirror M2 is held in the reflection mode until an ion 30 is detected by the charge detector CD. Until such detection, the process 100 follows the NO branch of step 108 and loops back to the beginning of step 108. Detection by the processor 12 of the ion by the charge detector CD serves as a trigger event which causes the processor 12 to follow the YES branch of step 108 and advance to step 110 of the process 100. In this version of the trigger trapping mode, the detected ion serving as the trigger event may be an ion entering the ELIT 10 from the ion source 25 and passing through the charge detection cylinder CD toward the ion mirror M2, or an ion reflected by the ion mirror M2 and passing back through the charge detection cylinder CD toward the ion mirror M1.
In a second version of the “trigger trapping mode,” steps 104 and 106 may be omitted, and detection by the processor 12 of an ion by the charge detector CD at step 108 again serves as a trigger event which causes the processor 12 to follow the YES branch of step 108 and advance to step 110. In this version of the trigger trapping mode, the ion mirrors M1, M2 are both in transmission mode such that the detected ion serving as the trigger event may only be an ion entering the ELIT 10 from the ion source 25 and passing through the charge detection cylinder CD toward the ion mirror M2.
Following the YES branch of step 108 in any of the trapping modes described above, the processor 12 is operable at step 110 to control the voltage sources V1-V3 to set the output voltages VO1-VO3 in a manner which changes or switches the operation of the ion mirror M1 from transmission mode of operation to the reflection mode of operation in which the ion mirror M1 operates to reflect an ion contained therein back toward the ion mirror M2 (and through the charge detector CD). Illustratively, the output voltages VO1-VO1 produced by the voltage sources V1-V3 respectively are controlled by the processor 12 at step 110 to establish a net “reflection” electric field EN4 in the ion mirror M1, which is identical or similar to the ion reflection electric field EN3 established within the ion mirror M2, and which is oriented to reflect the ion 30 entering therein from the charge detector CD back toward the ion mirror M2 (and through the charge detector CD) as illustrated by example in
Following step 110, the process 100 advances to step 112 where, as the ion is oscillating within the ELIT 10 back and forth between the ion mirrors M1, M2 during a “detection phase,” detection by the charge preamplifier CP of the charge induced on the charge detector CD by each passage of the ion therethrough (hereinafter referred to as a “charge detection event”) is recorded, i.e., stored in the memory 14, by the processor 12. Illustratively, the detection information recorded at step 112 includes amplitude and timing information, i.e., the amplitudes of each charge detection signal as well as the time of each charge detection signal relative to a reference time and/or relative to a time of a previous charge detection signal.
Following step 112, the process 100 advances to step 114 where the processor 12 is operable to pause and determine when to advance to step 114. In one embodiment, the processor 12 is configured, i.e. programmed, to allow the ion(s) to oscillate through the ELIT 10 back and forth between the ion mirrors M1, M2 during the detection phase for a selected time period during which charge detection events are recorded by the processor 12. As one non-limiting example, the selected time period which the processor 12 spends in the detection phase at step 114 before moving on to step 116 is on the order of 100 millisecond (ms), although it will be understood that such selected time period may, in other embodiments, be greater than 100 ms or less than 100 ms. Until the selected time period has elapsed, the process 100 follows the NO branch of step 114 and loops back to the beginning of step 114. After passage of the selected time period, the process 100 follows the YES branch of step 114 and advances to step 116. In some alternate embodiments of step 114, the ELIT 10 may illustratively be controlled by the processor 12 to allow the ion(s) to oscillate back in forth through the charge detector CD during the detection phase a selected number of times during which charge detection events are recorded by the processor 12. Until the processor counts the selected number charge detection events, the process 100 follows the NO branch of step 114 and loops back to the beginning of step 114. Detection by the processor 12 of the selected number of charge detection events serves as a trigger event which causes the processor 12 to follow the YES branch of step 114 and advance to step 116 of the process 100.
Following the YES branch of step 114, the processor 12 is operable at step 116 to control the voltage sources V1-V6 to set the output voltages VO1-VO6 in a manner which changes or switches the operation of both of the ion mirrors M1 and M2 from reflection mode of operation to the transmission mode of operation in which the ion mirrors M1, M2 each operate to allow passage of ions therethrough. Illustratively, the output voltages VO1-VO6 produced by the voltage sources V1-V6 respectively are controlled by the processor 12 at step 116 to re-establish net electric fields EN1 and EN2 in the ion mirrors M1, M2 as described above and as illustrated in
As described above, each detection by the charge preamplifier CP of a charge induced on the charge detector CD by passage of an ion therethrough is referred to as a “charge detection event.” As the ion oscillates back and forth between the ion mirrors M1, M2, multiple charge detection events are recorded. The total number of oscillations allowed before the process 100 advances from step 114 to step 116, or the total time allowed between step 110 and advancement of the process 100 from step 114, is referred to an ion trapping event. By either definition, the ion 30 oscillates back and forth between the ion mirrors M1, M2 for a “total trapping time” of an ion trapping event during which multiple charge detection events are recorded.
Following another YES branch of step 114, the process 100 additionally advances to step 120 to analyze the data collected during the ion trapping event just described. In the illustrated embodiment, the data analysis step 120 illustratively includes step 122 where the processor 12 is operable to compute a Fourier transform of the collected set of stored charge detection signals recorded during the ion trapping event. The processor 12 is illustratively operable to execute step 122 using any conventional digital Fourier transform (DFT) technique such as for example, but not limited to, a conventional Fast Fourier Transform (FFT) algorithm. Following step 122, the process 100 advances to step 124 where the processor 12 is operable to compute values of ion mass-to-charge ratio (m/z) and ion charge (z), each as a function of the computed FFT, and thereafter at step 126 the processor 12 is operable to store the computed results in the memory 14 and/or to control one or more of the peripheral devices 18 to display the results for observation and/or further analysis.
It is generally understood that the mass-to-charge ratio (m/z) of an ion 30 oscillating in an ELIT is inversely proportional to the square of the fundamental frequency ff of the oscillating ion 30 according to the equation:
m/z=C/ff
2,
where C is a constant that is a function of the ion energy and also a function of the dimensions of the ELIT. Typically, C is determined using conventional ion trajectory simulations. In any case, the value of the ion charge, z, is proportional to the magnitude of the fundamental frequency of the FFT, taking into account the number of ion oscillation cycles. Ion mass, m, is then calculated as a product of m/z and z. In some cases, the magnitude(s) of one or more of the harmonic frequencies of the FFT may be added to the magnitude of the fundamental frequency for purposes of determining the ion charge, z.
Multiple, e.g., hundreds or thousands or more, ion trapping events are typically carried out for any particular sample from which the ions are generated by the ion source 25, and ion mass-to-charge, ion charge and ion mass values are determined/computed for each such ion trapping event at step 120 of the process 100. The ion mass-to-charge, ion charge and ion mass values for such multiple ion trapping events are, in turn, combined to form spectral information relating to the sample. Such spectral information may illustratively take different forms, examples of which include, but are not limited to, ion count vs. mass-to-charge ratio, ion charge vs. ion mass (e.g., in the form of an ion charge/mass scatter plot), ion count vs. ion mass, ion count vs. ion charge, or the like.
Generally, uncertainty in the determination of ion mass with an ELIT depends on the uncertainties in the m/z and z measurements. In the process 100 just described, the measured m/z values are inversely proportional to the square of the fundamental frequency, ff, and the measured charge values are proportional to the magnitude of the FFT fundamental frequency. It has been determined through simulation and experimentation that because the measured charge values are proportional to the magnitude of the fundamental frequency, ff, of the oscillating charge detection signal, uncertainty in the charge measurements can be reduced by increasing the signal-to-noise ratio of the fundamental frequency ff of the oscillating charge detection signal relative to one or more harmonics of the oscillating charge detection signal.
The oscillating charge detection signal just described is substantially a square-wave signal having a duty cycle, DC, defined as a ratio of the time spent by the ion 30 in the charge detection cylinder CD and the time spent by the ion 30 traversing the entire ELIT during one oscillation cycle. In particular, and referring again to
Referring to
In order to achieve a 50% duty cycle, the time spent by an ion 30 traversing the distance DZ1+Z3+DZ2 must be equal to the time spent by the ion 30 traversing the distance DZ2+Z3+DZ2 in the opposite direction. The duty cycle equation set forth in the previous paragraph thus simplifies to DC=TZ3/(TDZ1+TZ3+TDZ2), where TZ3 is the time spent by the ion 30 traversing D3 in either direction, TDZ1 is the time spent by the ion 30 travelling through each of DZ1 and DZ2 toward the other and TDZ2 is the time spent by the ion 30 traveling into each of DZ1 and DZ2 prior to being reflected, i.e., prior to changing directions under the influence of the net electric fields EN4 and EN3 respectively. Moreover, the requirement DC=½ results in TZ3=TDZ1+TDZ2, such that, during each single-direction pass through the ELIT 10, the time spent by the ion 30 passing each through the charge detection cylinder CD should be approximately equal to the sum of the time spent reflecting the ion 30 from a stopped state in one of the ion mirrors M1, M2 to the respective end or entrance of the charge detection cylinder CD and the time spent by the ion exiting the opposite end of the charge detection cylinder CD and traveling toward and into the other ion mirror M1, M2 to a stopped state.
Referring now to
Referring again to
Referring now to
Focusing on the ion source 25, it will be understood that the source 25 of ions entering the ELIT 10 may be or include, in the form of one or more of the ion source stages IS1-ISQ, one or more conventional sources of ions as described above, and may further include one or more conventional instruments for separating ions according to one or more molecular characteristics (e.g., according to ion mass, ion mass-to-charge, ion mobility, ion retention time, or the like) and/or one or more conventional ion processing instruments for collecting and/or storing ions (e.g., one or more quadrupole, hexapole and/or other ion traps), for filtering ions (e.g., according to one or more molecular characteristics such as ion mass, ion mass-to-charge, ion mobility, ion retention time and the like), for fragmenting or otherwise dissociating ions, for normalizing or shifting ion charge states, and the like. It will be understood that the ion source 25 may include one or any combination, in any order, of any such conventional ion sources, ion separation instruments and/or ion processing instruments, and that some embodiments may include multiple adjacent or spaced-apart ones of any such conventional ion sources, ion separation instruments and/or ion processing instruments. In any implementation which includes one or more mass spectrometers, any one or more such mass spectrometers may be implemented in any of the forms described above with respect to
Turning now to the ion processing instrument 210, it will be understood that the instrument 210 may be or include, in the form of one or more of the ion processing stages OS1-OSR, one or more conventional instruments for separating ions according to one or more molecular characteristics (e.g., according to ion mass, ion mass-to-charge, ion mobility, ion retention time, or the like) and/or one or more conventional ion processing instruments for collecting and/or storing ions (e.g., one or more quadrupole, hexapole and/or other ion traps or guides), for filtering ions (e.g., according to one or more molecular characteristics such as ion mass, ion mass-to-charge, ion mobility, ion retention time and the like), for fragmenting or otherwise dissociating ions, for normalizing or shifting ion charge states, and the like. It will be understood that the ion processing instrument 210 may include one or any combination, in any order, of any such conventional ion separation instruments and/or ion processing instruments, and that some embodiments may include multiple adjacent or spaced-apart ones of any such conventional ion separation instruments and/or ion processing instruments. In any implementation which includes one or more mass spectrometers, any one or more such mass spectrometers may be implemented in any of the forms described above with respect to
As one specific implementation of the ion separation instrument 200 illustrated in
As another specific implementation of the ion separation instrument 200 illustrated in
As yet another specific implementation of the ion separation instrument 200 illustrated in
As still another specific implementation of the ion separation instrument 200 illustrated in
Referring now to
MS/MS, e.g., using only the ion separation instrument 230, is a well-established approach where precursor ions of a particular molecular weight are selected by the first mass spectrometer 232 (MS1) based on their m/z value. The mass selected precursor ions are fragmented, e.g., by collision-induced dissociation, surface-induced dissociation, electron capture dissociation or photo-induced dissociation, in the ion dissociation stage 234. The fragment ions are then analyzed by the second mass spectrometer 236 (MS2). Only the m/z values of the precursor and fragment ions are measured in both MS1 and MS2. For high mass ions, the charge states are not resolved and so it is not possible to select precursor ions with a specific molecular weight based on the m/z value alone. However, by coupling the instrument 230 to the CDMS 40 illustrated and described herein, it is possible to select a narrow range of m/z values using MS1 and then use the CDMS 40 to determine the masses of the m/z selected precursor ions. The mass spectrometers 232, 236 may be, for example, one or any combination of a magnetic sector mass spectrometer, time-of-flight mass spectrometer or quadrupole mass spectrometer, although in alternate embodiments other mass spectrometer types may be used, non-limiting examples of which are described hereinabove. In any case, the m/z selected precursor ions with known masses exiting MS1 can be fragmented in the ion dissociation stage 234, and the resulting fragment ions can then be analyzed by MS2 (where only the m/z ratio is measured) and/or by the CDMS instrument 40 (where the m/z ratio and charge are measured simultaneously). Low mass fragments, i.e., dissociated ions of precursor ions having mass values below a threshold mass value, e.g., 10,000 Da (or other mass value), can thus be analyzed by conventional MS, using MS2, while high mass fragments (where the charge states are not resolved), i.e., dissociated ions of precursor ions having mass values at or above the threshold mass value, can be analyzed by CDMS.
It will be understood that one or more charge detection optimization techniques may be used with the ELIT 10 alone and/or in any of the systems 40, 200, 220 illustrated in the attached figures and described herein, e.g., for trigger trapping and/or other charge detection events. Examples of some such charge detection optimization techniques are illustrated and described in co-pending U.S. Patent Application Ser. No. 62/680,296, filed Jun. 4, 2018 and in co-pending International Patent Application No. PCT/US2019/13284, filed Jan. 11, 2019, both entitled APPARATUS AND METHOD FOR CAPTURING IONS IN AN ELECTROSTATIC LINEAR ION TRAP, the disclosures of which are both expressly incorporated herein by reference in their entireties.
It will be further understood that one or more charge calibration or resetting apparatuses may be used with the charge detection cylinder CD of the ELIT 10 alone and/or in any of the systems 40, 200, 220 illustrated in the attached figures and described herein. An example of one such charge calibration or resetting apparatus is illustrated and described in co-pending U.S. Patent Application Ser. No. 62/680,272, filed Jun. 4, 2018 and in co-pending International Patent Application No. PCT/US2019/13284, filed Jan. 11, 2019, both entitled APPARATUS AND METHOD FOR CALIBRATING OR RESETTING A CHARGE DETECTOR, the disclosures of which are both expressly incorporated herein by reference in their entireties.
It will be still further understood that the design concepts for achieving a desired duty cycle within the ELIT 10 alone and/or in any of the systems 40, 200, 220 illustrated in the attached figures and described herein may be implemented in an ELIT array including two or more ELITs and/or in any ELIT including two or more ELIT regions. Examples of some such ELITs and/or ELIT arrays are illustrated and described in co-pending U.S. Patent Application Ser. No. 62/680,315, filed Jun. 4, 2018 and in co-pending International Patent Application No. PCT/US2019/13283, filed Jan. 11, 2019, both entitled ION TRAP ARRAY FOR HIGH THROUGHPUT CHARGE DETECTION MASS SPECTROMETRY, the disclosures of which are both expressly incorporated herein by reference in their entireties.
It will be further understood that one or more ion source optimization apparatuses and/or techniques may be used with one or more embodiments of the ion source 25 illustrated and described herein in combination with the ELIT 10 along and/or in any of the systems 40, 200, 220 illustrated in the attached figures and described herein, some examples of which are illustrated and described in co-pending U.S. Patent Application Ser. No. 62/680,223, filed Jun. 4, 2018 and entitled HYBRID ION FUNNEL-ION CARPET (FUNPET) ATMOSPHERIC PRESSURE INTERFACE FOR CHARGE DETECTION MASS SPECTROMETRY, and in co-pending International Patent Application No. PCT/US2019/13274, filed Jan. 11, 2019 and entitled INTERFACE FOR TRANSPORTING IONS FROM AN ATMOSPHERIC PRESSURE ENVIRONMENT TO A LOW PRESSURE ENVIRONMENT, the disclosures of which are both expressly incorporated herein by reference in their entireties.
It will be still further understood that the charge detection mass spectrometer 40, the ion separation instrument 200, the ion separation instrument 230 and/or the ELIT 10 illustrated in the attached figures and described herein may be implemented in accordance with real-time analysis and/or real-time control techniques, some examples of which are illustrated and described in co-pending U.S. Patent Application Ser. No. 62/680,245, filed Jun. 4, 2018 and co-pending International Patent Application No. PCT/US2019/13277, filed Jan. 11, 2019, both entitled CHARGE DETECTION MASS SPECTROMETRY WITH REAL TIME ANALYSIS AND SIGNAL OPTIMIZATION, the disclosures of which are both expressly incorporated herein by reference in their entireties.
It will be yet further understood that one or more ion inlet trajectory control apparatuses and/or techniques may be used with the ELIT 10 alone and/or in any of the systems 40, 200, 220 illustrated in the attached figures and described herein to provide for simultaneous measurements of multiple individual ions within the ELIT 10. Examples of some such ion inlet trajectory control apparatuses and/or techniques are illustrated and described in co-pending U.S. Patent Application Ser. No. 62/774,703, filed Dec. 3, 2018 and in co-pending International Patent Application No. PCT/US2019/13285, filed Jan. 11, 2019, both entitled APPARATUS AND METHOD FOR SIMULTANEOUSLY ANALYZING MULTIPLE IONS WITH AN ELECTROSTATIC LINEAR ION TRAP, the disclosures of which are both expressly incorporated herein by reference in their entireties.
While this disclosure has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as illustrative and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of this disclosure are desired to be protected. For example, while the ELIT 10 illustrated in the attached figures has been described herein as being designed and operated with an oscillating charge detection signal having a duty cycle of approximately 50% for the purpose of reducing noise in fundamental frequency magnitude determinations resulting from harmonic frequency components of the signal, this disclosure also contemplates alternatively or additionally employing other structures and/or techniques for reducing the effects of harmonic frequency components on such fundamental frequency magnitude determinations. Examples of such other structures and/or techniques may include, but are not limited to, one or more harmonic component filtering structures and/or techniques, one or more wave-shaping structures and/or techniques, one or more multi-phase operating structures and/or techniques, and the like. As another example, although the ion mirrors M1 and M2 are illustrated in the attached figures and described herein as each including an aligned arrangement of three spaced-apart mirror electrodes, it will be understood that such embodiments are provided only by way of example and should not be considered limiting in any way. Alternate embodiments in which either or both of the ion mirrors M1, M2 include more or fewer mirror electrodes are intended to fall within the scope of this disclosure. As yet another example, it will be understood that the steps of the process 100 illustrated in the attached figures and described herein are also provided only by way of example and should not be considered limiting in any way. Alternate techniques for operating the ELIT 10 described herein to capture the measurements and data described herein are intended to fall within the scope of this disclosure, and it will be recognized that any such alternate techniques will be a mechanical step for one skilled in the art using the concepts described herein as a template. As still another example, it will be understood that the ELIT 10 illustrated in the attached figures and described herein is provided only by way of example, and that the concepts, structures and techniques described above may be implemented directly in ELITs of various alternate designs. Any such alternate ELIT design may, for example, include any one or combination of two or more ELIT regions, more, fewer and/or differently-shaped ion mirror electrodes, more or fewer voltage sources, more or fewer DC or time-varying signals produced by one or more of the voltage sources, one or more ion mirrors defining additional electric field regions, or the like.
This application is a continuation of U.S. patent application Ser. No. 16/960,170, filed Jul. 6, 2020, which is a U.S. national stage entry of PCT Application No. PCT/US2019/013251, filed Jan. 11, 2019, which claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 62/616,860, filed Jan. 12, 2018 and to U.S. Provisional Patent Application Ser. No. 62/680,343, filed Jun. 4, 2018, the disclosures of which are incorporated herein by reference in their entireties.
This invention was made with government support under CHE1531823 and 0832651 awarded by the National Science Foundation. The United States Government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 62680343 | Jun 2018 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16960170 | Jul 2020 | US |
| Child | 17468791 | US |
