CN116615648A

CN116615648A - Mass and/or ion mobility spectrometry

Info

Publication number: CN116615648A
Application number: CN202180084246.XA
Authority: CN
Inventors: 詹森·维尔德古斯; 马丁·格林; 大卫·兰格里奇; 凯文·贾尔斯; 雅库布·乌伊玛
Original assignee: Micromass UK Ltd
Current assignee: Micromass UK Ltd
Priority date: 2020-12-24
Filing date: 2021-12-23
Publication date: 2023-08-18

Abstract

The present application provides a method of analysing ions, the method comprising: separating ions according to a first physicochemical property by passing the ions through an ion separation device; and measuring the transit time of ions through the ion separation device. The method further comprises the steps of: detecting the ions using a charge resolving ion detector to determine the charge of the ions; and determining a second physical chemical property of the ion using the transit time and the charge of the ion.

Description

Mass and/or ion mobility spectrometry

Cross Reference to Related Applications

The present application claims priority and equity from uk patent application 2020575.3 filed on 12/month 24 and uk patent application 2106850.7 filed on 5/month 13 2021. The entire contents of these applications are incorporated herein by reference.

Technical Field

The present application relates generally to methods of analyzing particles and/or ions, and in particular to methods of analyzing particles and/or ions using mass spectrometry and/or ion mobility spectrometry.

Background

Charge Detection Mass Spectrometry (CDMS) is becoming a popular method of mass spectrometry of high charge species because this technique employs a method that allows for separation of ions having similar or identical mass to charge ratios (m/z) but different charges (z), thereby ultimately improving the resolution and mass measurement of the mass spectrum.

These methods typically use ion trapping techniques to simultaneously measure mass-to-charge ratio (m/z) and charge (z). However, these methods are relatively slow compared to other m/z separations, such as time-of-flight mass spectrometry (ToF-MS). The velocity is further affected by limitations limited to analyzing individual particles or molecules to avoid space charge effects and by overlapping signals due to the captured ions following non-unique flight paths or trajectories.

Applicants believe that there is still room for improvement in mass spectrometry methods.

Disclosure of Invention

According to one aspect, there is provided a method of analysing ions, the method comprising:

separating ions according to a first physicochemical property by passing the ions through an ion separation device;

measuring the transit time of ions through the ion separation device to determine the transit time of the ions;

detecting the ions using a charge resolving ion detector to determine the charge of the ions; and

the transit time and the charge of the ion are used to determine a second physical chemical property of the ion.

Various embodiments relate to a method of analyzing ions, wherein the ions are separated according to a first physicochemical property by passing the ions through an ion separation device. For each (individual) one or more of the ions, the transit time of the ion through the separation device is measured to determine the transit time (i.e., the "drift time") of the ion. In addition, charge resolving ion detectors are used to detect ions in order to determine the charge (i.e., the "state of charge" or "charge number") of the ions. The transit time and charge of the ion are then used (e.g., combined) to determine a second physical and chemical property of the ion.

For example, in the case of ion separation according to the mass-to-charge ratio (m/z) of the ions (i.e. in the case where the first physicochemical property comprises a mass-to-charge ratio), the transit time of each ion will be related to its mass-to-charge ratio. Thus, by combining the transit time and charge of an ion, the mass (or mass-related property) of the ion can be determined.

According to particular embodiments, the process is repeated for each ion of the plurality of ions, e.g., to determine a second physical chemical property (e.g., mass) of each individual ion, and the results are combined to produce a spectrum (e.g., mass spectrum) of the analyzed ions.

Embodiments are particularly suitable for analyzing particles that may produce ions having different charge states but relatively close mass-to-charge ratios (m/z). This is often the case for high quality particles (which are typically highly charged), e.g. mass >1 MDa.

In general, in order to derive the mass of such particles, the different charge states have to be distinguishable in terms of mass-to-charge ratio (m/z). However, this may require high resolution (and thus expensive) instruments. Sample heterogeneity and/or adducts may also render the different charge states indistinguishable. Although Charge Detection Mass Spectrometry (CDMS) methods may be used to separate such highly charged ions, as described above, these methods may be relatively slow.

Various embodiments utilize the inherent speed of separation-based methods (e.g., time-of-flight (ToF) mass spectrometry). Furthermore, embodiments utilize the charge state resolution provided by the charge resolving ion detector (in addition to, for example, the mass-to-charge ratio (m/z) resolution of the separation device) to resolve ions, for example, having similar or identical mass-to-charge ratios (m/z) but having different charges (z).

This facilitates improved resolution of the final spectrum (e.g., mass spectrum) without requiring either high resolution instrumentation or the use of slower methods such as Charge Detection Mass Spectrometry (CDMS). The process of the various embodiments is orders of magnitude faster than the CDMS process.

Accordingly, it will be appreciated that the various embodiments provide an improved method of analyzing ions.

The method may include ionizing the particles to produce ions.

The particle, plurality and/or one ion may (each) have a mass of >1 MDa.

The first physicochemical property may include a mass to charge ratio (m/z) or an ion mobility.

Where the first physicochemical property comprises a mass to charge ratio (m/z), the ion separation device may comprise a time of flight (ToF) separation device configured to separate the ions according to their mass to charge ratio. For example, the ion separation device may comprise a time of flight (ToF) mass analyzer.

Alternatively, the ion separation device may comprise an ion separation device in which one or more time-varying electric fields are used to push ions through the gas so that the ions are separated according to mass to charge ratio.

For example, the ion separation device may be a travelling wave separation device. The method may comprise applying one or more voltages to different electrodes of the ion separation device in succession so as to form one or more travel barriers that move along the ion separation device so as to push ions through the gas.

In the case where the first physicochemical property comprises ion mobility, the ion separation device may comprise an ion mobility separation device configured to separate ions according to their ion mobility.

The step of measuring the transit time of the ions through the ion separation device may comprise measuring the transit time of the ions using the charge resolving ion detector.

In these embodiments, the charge-resolving ion detector may comprise (i) a faraday cup or a cylindrical electrode detector; (ii) an electron multiplier detector; (iii) a photomultiplier or scintillation counter detector; and/or (iv) a Superconducting Tunnel Junction (STJ) detector. The method may include determining the charge of the ion when the ion is detected based on the intensity, amplitude and/or area of a signal generated by the charge-resolving ion detector.

Alternatively, the step of measuring the transit time of the ions through the ion separation device may comprise measuring the transit time of the ions using a second (different) ion detector. Thus, the (each) ion may be detected by a first charge resolving ion detector to determine the charge of the ion and a second, different ion detector to determine the transit time of the ion.

In these embodiments, the charge-resolving ion detector may comprise any suitable (non-destructive) charge-resolving ion detector configured to measure the charge of ions. For example, the charge-resolving ion detector may comprise an inductive charge detector, such as an inductive plate or an inductive tube.

The second ion detector may comprise (i) a faraday cup or a cylindrical electrode detector; (ii) an electron multiplier detector; (iii) a photomultiplier or scintillation counter detector; and/or (iv) a Superconducting Tunnel Junction (STJ) detector. The charge resolving ion detector may be arranged upstream of the second ion detector.

Determining the second physical property of the ion using the transit time and the charge of the ion may include combining the transit time and the charge of the ion to determine the second physical property of the ion.

The method may comprise controlling the ion flux at the one or more detectors such that (some, most or all) individual ions are distinguishable from each other when detected by the one or more detectors.

For each ion of a plurality of (individual) ions, the method may comprise:

measuring the transit time of the ions through the ion separation device to determine the transit time of the ions;

detecting the ions using the charge resolving ion detector to determine the charge of the ions; and

the transit time and the charge of the ion are used to determine the second physical and chemical properties of the ion.

The method may further comprise: the determined second physical and chemical properties of each ion of the plurality of ions are combined to produce a spectrum of the ion.

The second physical and chemical property may comprise mass, or collision or reaction cross section. Thus, the spectra may include mass spectra, or collision or reaction cross-section spectra.

The method may include reducing the charge of the ions prior to separating the ions.

According to an aspect, there is provided an analytical instrument comprising:

an ion separation device, wherein the ion separation device is configured to separate ions according to a first physicochemical property when the ions are passed through the ion separation device; and

An ion detector disposed downstream of the ion separation device, wherein the analysis instrument is configured such that ions eluted from the ion separation device are detectable by the ion detector;

wherein the analysis instrument is configured to measure a transit time of ions through the ion separation device to determine the transit time of the ions;

wherein the ion detector comprises a charge-resolving ion detector configured to determine the charge of the ion; and is also provided with

Wherein the analysis instrument is configured to determine a second physical chemical property of the ion using the transit time and the charge of the ion.

The analysis instrument may include an ion source configured to ionize particles so as to generate ions.

The particle, plurality and/or one ion may (each) have a mass of >1 MDa.

Where the first physicochemical property comprises a mass to charge ratio (m/z), the ion separation device may comprise a time of flight (ToF) separation device configured to separate ions according to their mass to charge ratio. For example, the ion separation device may comprise a time of flight (ToF) mass analyzer.

Alternatively, the ion separation device may comprise an ion separation device in which one or more time-varying electric fields are used to push ions through the gas so that the ions are separated according to mass to charge ratio. For example, the ion separation device may be a travelling wave separation device.

The analysis instrument may be configured to apply one or more voltages to different electrodes of the ion separation device in succession so as to form one or more travel barriers that move along the device so as to push ions through the gas.

The analysis instrument may be configured to measure the transit time of the ions through the ion separation device using the charge-resolving ion detector.

In these embodiments, the charge-resolving ion detector may comprise (i) a faraday cup or a cylindrical electrode detector; (ii) an electron multiplier detector; (iii) a photomultiplier or scintillation counter detector; and/or (iv) a Superconducting Tunnel Junction (STJ) detector. The analysis instrument may be configured to determine the charge of the ion when the ion is detected based on the intensity, amplitude and/or area of the signal generated by the charge-resolving ion detector.

Alternatively, the analysis instrument may comprise a second ion detector and the analysis instrument may be configured to use the second ion detector to measure the transit time of the ions through the ion separation device. Thus, the analysis instrument may be configured to determine the charge of the (each) ion using a first charge resolving ion detector and to determine the transit time of the (each) ion using a second, different ion detector.

The analysis instrument may be configured to combine the transit time and the charge of the ion to determine a second physical chemical property of the ion.

The analysis instrument may be configured to control ion flux at one or more detectors such that (some, most or all) individual ions are distinguishable from one another when detected by the one or more detectors.

The analytical instrument may be configured to:

for each ion of a plurality of (individual) ions:

The analysis instrument may be further configured to: the determined second physical and chemical properties of each ion of the plurality of ions are combined to produce a spectrum of the ion.

The analysis instrument may include one or more devices configured to reduce the charge of the ions, which may be disposed upstream of the ion separation device.

Detecting ions using an induced charge detector;

determining a charge of the ion from a signal generated by the induced charge detector when the ion is detected;

determining a transit time of the ion from the signal generated by the induced charge detector when the ion is detected; and

the transit time and the charge of the ion are used to determine a (second) physicochemical property of the ion.

According to an aspect, there is provided an analytical instrument comprising:

an induced charge detector configured to detect ions;

wherein the analytical instrument is configured to:

determining the charge of the ion from the signal generated by the induced charge detector when the ion is detected;

These aspects may include, and in various embodiments do include, any one or more or each of the optional features described elsewhere herein.

For example, the method may include:

For each ion of the plurality of ions:

detecting the ions using an induced charge detector;

determining a (second) physicochemical property of the ion using the transit time and the charge of the ion; and

the determined second physical and chemical properties of each ion of the plurality of ions are combined to produce a spectrum of the ion.

The second physical and chemical property may include (i) a mass, or (ii) a collision or reaction cross section.

isolating ions having a first value of a first physicochemical property by passing the ions through an ion filtration device;

a second physical chemistry of the ion is determined using the first value of the first physical chemistry of the ion and the charge.

According to an aspect, there is provided an analytical instrument comprising:

An ion filtration device, wherein the ion filtration device is configured to filter ions according to a first physicochemical property when passing ions through the ion separation device; and

an ion detector disposed downstream of the ion filtering device, wherein the analysis instrument is configured such that ions eluted from the ion filtering device are detectable by the ion detector;

wherein the analysis instrument is configured to isolate ions having a first value of a first physicochemical property by passing the ions through the ion filtering device;

Wherein the analysis instrument is configured to determine a second physical chemical property of the ion using the first value of the first physical chemical property of the ion and the charge.

For example, the method may include:

isolating ions of different values having a first physicochemical property by passing the ions through an ion filtration device, optionally while simultaneously changing (e.g., scanning) a (first physicochemical property) transmission window of the ion filtration device; and

For each ion of the plurality of ions:

determining a second physical chemistry of the ion using the value of the first physical chemistry of the ion and the charge of the ion; and

The first physicochemical property may include a mass to charge ratio (m/z). The second physical and chemical property may include mass.

The ion filter device may comprise a quadrupole mass filter.

According to one aspect, provided herein is a method of mass spectrometry comprising:

separating groups of ions over time, wherein time is related to two or more physicochemical properties, and wherein one of the physicochemical properties is a charge number;

detecting ions using a detector having a response as a function of the charge state of the detected ions;

controlling the ion flux at the detector such that the responses of individual ions are distinguishable and measurable from each other; and

the detector signal is processed in each separation cycle to produce a spectrum based on one or more physicochemical properties other than the state of charge.

Drawings

Various embodiments will now be described, by way of example only, and with reference to the accompanying drawings, in which:

FIG. 1 schematically illustrates an analytical instrument configured according to an embodiment;

FIG. 2 shows the percent reduction in average particle velocity as a function of α and γ for a one-dimensional smooth moving traveling wave device;

FIG. 3 schematically illustrates an analytical instrument configured according to an embodiment;

FIG. 4 schematically illustrates an analytical instrument configured according to an embodiment;

FIG. 5 schematically illustrates an analytical instrument configured according to an embodiment; and is also provided with

Fig. 6 shows simulated data from a simple audiometric tube.

Detailed Description

CDMS is becoming a popular method of mass spectrometry of high charge materials because this technique employs a method that allows for separation of ions having similar or identical mass to charge ratios (m/z) but with different charges (z), thereby ultimately improving resolution and mass measurement of the mass spectrum.

These methods typically use ion trapping techniques to measure m/z and z simultaneously. However, these methods are relatively slow compared to other m/z separations such as time of flight mass spectrometry (ToF-MS). The velocity is further affected by the limitation of being limited to analyzing individual particles and/or molecules to avoid space charge effects, and by overlapping signals due to the captured ions following non-unique flight paths and/or trajectories.

In the case of separating ions according to their ion mobility (i.e., in the case where the first physicochemical property comprises ion mobility), the transit time of each ion will be related to its ion mobility. By combining the transit time and charge of an ion, the collision or reaction cross-section (or a property related to the collision or reaction cross-section) of the ion can be determined.

According to particular embodiments, the process is repeated for each ion of the plurality of ions, e.g., to determine a second physical chemical property (e.g., mass) of each individual ion, and the results are combined to produce a spectrum (e.g., mass spectrum) of the analyzed ions. To facilitate this, ion flux at one or more detectors may be controlled such that (some, most, or all) individual ions are distinguishable from one another when detected by the one or more detectors.

Fig. 1 schematically shows an analysis instrument in the form of a mass spectrometer and/or an ion mobility spectrometer according to an embodiment.

As shown in fig. 1, the analysis apparatus includes an ion source 10, an ion separation device 20 disposed downstream of the ion source 10, and a detector 30 disposed downstream of the ion source 10 and downstream of the ion separation device 20. As shown in fig. 1, the analysis instrument may be configured such that ions may be provided (sent) to the analyzer 30 by (from) the ion source 10 via the ion isolation apparatus 20.

As also shown in fig. 1, the analytical instrument may include a control system 40 configured to control operation of the analytical instrument, for example, in the manner of the various embodiments described herein. The control system may include suitable control circuitry configured to cause the instrument to operate in the manner of the various embodiments described herein. The control system may include suitable processing circuitry configured to perform any one or more or all of the necessary processing and/or post-processing operations with respect to the various embodiments described herein. The control system may include one or more of a suitable computing device, microprocessor system, programmable FPGA (field programmable gate array), or the like.

The ion source 10 is configured to ionize particles to produce ions.

The particles may be high quality particles, for example, wherein each particle has a mass of >1 MDa. Likewise, the ions may each have a mass of >1 MDa. Such high mass particles, which are typically highly charged, can generally produce ions having different charge states but relatively close mass-to-charge ratios (m/z).

The high quality particles may include any high quality particles such as, for example, viruses, capsids, nanoparticles (such as nanoparticles comprising surface active molecules (e.g., vesicles, nanodiscs), lipoprotein particles (e.g., cholesterol), polyoxometalates and other supramolecular constructs, metal clusters, polymer chains, and the like.

The ion source 10 may comprise any suitable ion source, such as an ambient ionization ion source, i.e., an ion source configured to ionize particles at ambient or atmospheric pressure.

The ion source 10 may be an ion source selected from the group consisting of: (i) an electrospray ionization ("ESI") ion source; (ii) an atmospheric pressure photoionization ("APPI") ion source; (iii) An atmospheric pressure chemical ionization ("APCI") ion source; (iv) A matrix-assisted laser desorption ionization ("MALDI") ion source; (v) a laser desorption ionization ("LDI") ion source; (vi) an atmospheric pressure ionization ("API") ion source; (vii) a desorption ionization on silicon ("DIOS") ion source; (viii) an electron impact ("EI") ion source; (ix) a chemical ionization ("CI") ion source; (x) a field ionization ("FI") ion source; (xi) a field desorption ("FD") ion source; (xii) an inductively coupled plasma ("ICP") ion source; (xiii) a fast atom bombardment ("FAB") ion source; (xiv) A liquid secondary ion mass spectrometry ("LSIMS") ion source; (xv) a desorption electrospray ionization ("DESI") ion source; (xvi) a source of nickel-63 radioactive ions; (xvii) An atmospheric pressure matrix assisted laser desorption ionization ion source; (xviii) a thermal spray ion source; (xix) An atmospheric sampling glow discharge ionization ("ASGDI") ion source; (xx) a glow discharge ("GD") ion source; (xxi) an impactor ion source; (xxii) a real-time direct analysis ("DART") ion source; (xxiii) a laser spray ionization ("LSI") ion source; (xxiv) an acoustic spray ionization ("SSI") ion source; (xxv) A matrix-assisted inlet ionization ("MAII") ion source; (xxvi) A solvent assisted inlet ionization ("SAII") ion source; (xxvii) A laser ablation electrospray ionization ("LAESI") ion source; (xxviii) A surface-assisted laser desorption ionization ("SALDI") ion source; (xxix) a low temperature plasma ("LTP") ion source; (xxxi) a helium plasma ionization ("HePI") ion source; (xxxi) A rapid evaporative ionization mass spectrometry ("REIMS") ion source; and/or (xxxii) a laser-assisted rapid evaporative ionization mass spectrometry ("LA-REIMS") ion source.

In a particular embodiment, the ion source 10 is an electrospray ionization (ESI) ion source.

The analytical instrument may optionally include a chromatographic separation device or other separation device (not shown in fig. 1) located upstream of (and coupled to) the ion source 10. The chromatographic separation device may comprise a liquid chromatography device or a gas chromatography device. Alternatively, the separation device may comprise: (i) a capillary electrophoresis ("CE") separation device; (ii) a capillary electrochromatography ("CEC") separation device; (iii) A substantially rigid ceramic-based multilayer microfluidic substrate ("tile") separation device; or (iv) a supercritical fluid chromatographic separation device.

The ion isolation device 20 is configured to receive ions from the ion source 10 (optionally via one or more ion guides or other ion optical elements), isolate the ions according to a first physicochemical property, and then pass the isolated ions to the detector 30 for detection (optionally via one or more ion guides or other ion optical elements). Ions may be separated within the ion separation device 20 as they travel through the ion separation device 20.

The ions may be separated according to the first physicochemical property such that ions of different values of the first physicochemical property arrive at the outlet region of the ion separation device 20 at different times, for example such that ions of a relatively higher value of the first physicochemical property arrive at the outlet region prior to ions of a relatively lower value of the first physicochemical property (or such that ions of a relatively lower value of the first physicochemical property arrive at the outlet region prior to ions of a relatively higher value of the first physicochemical property).

This means that the transit time of an ion through the ion separation device 20 will be related to the value of the first physicochemical property of that ion. Thus, by measuring the transit time of ions through the ion isolation device 20, a particular value of the first physicochemical property of the ions can be determined.

The ion separation device 20 may comprise any suitable device configured to (temporarily) separate ions according to a first physicochemical property. Likewise, the first physicochemical property may comprise any suitable physicochemical property. In particular embodiments, the first physicochemical property is (i) a mass to charge ratio (m/z) or (ii) an ion mobility collision or reaction cross section.

Where the first physicochemical property comprises a mass to charge ratio (m/z), the ion separation device 20 may comprise a time of flight (ToF) separation device, such as a time of flight (ToF) mass analyser, configured to separate ions according to their mass to charge ratio (m/z).

In these embodiments, the mass analyzer may include acceleration (pusher) electrodes, acceleration regions, and field-free or drift regions (e.g., in the form of "drift tubes"). The mass analyzer may further comprise a (pusher) drive unit and a circuit configured to supply the accelerating (pusher) electrode of the mass analyzer with the electrical pulses generated by the drive unit.

Ions from the ion source 10 may be arranged to enter an acceleration region in which they may be driven into a field-free or drift region by applying electrical pulses (generated by a (pusher) drive unit) to accelerating (pusher) electrodes. Accordingly, a time-of-flight (ToF) mass analyzer may be configured to accelerate ions into a field-free or drift region as a result of an electrical pulse being supplied to an acceleration electrode.

The ions may be accelerated to a velocity determined by the energy applied by the pulse and the mass-to-charge ratio (m/z) of the ions. Ions with a relatively low mass to charge ratio will achieve a relatively high velocity and reach the exit of the field-free or drift region before ions with a relatively high mass to charge ratio. Thus, the ions may reach the exit of the field-free or drift region after a transit time determined by their velocity and travel distance, which enables the mass-to-charge ratio of the ions to be determined.

Thus, ions may be separated according to their mass to charge ratio (m/z), and the transit time of the (each) ion through the ion separation device may be measured to determine the transit time of the ion (which may be related to the mass to charge ratio of the ion).

In these embodiments, the ion separation device 20 (its drift tube) may be maintained at a relatively low pressure, such as the following pressures: about (i) <0.00001mbar; (ii) 0.00001mbar to 0.0001mbar; (iii) from 0.0001mbar to 0.001mbar; (iv) 0.001mbar to 0.01mbar; or (iv) from 0.01mbar to 0.1mbar.

In various alternative embodiments, the ion separation device 20 may comprise a high pressure m/z separation device. In these embodiments, the ion separation device 20 may be configured to separate ions according to mass to charge ratio by using one or more time-varying electric fields to push the ions through the gas.

The separation region of the ion separation device 20 may be filled with a gas, such as an inert (buffer) gas, such as nitrogen. As the ions pass through the gas, the ions may be separated within the ion separation device 20 according to their mass to charge ratio (m/z).

The ion separation device 20 (its separation region) may be operated at (maintained at) any suitable pressure, such as (i) <0.1mbar; (ii) 0.1mbar to 0.5mbar; (iii) 0.5mbar to 1mbar; (iv) from 1mbar to 2mbar; (v) 2mbar to 5mbar; (vi) 5mbar to 10mbar; (vii) 10mbar to 15mbar; (viii) 15mbar to 20mbar; (ix) 20mbar to 25mbar; (x) 25mbar to 30mbar; or (xi) >30mbar. In a particular embodiment, the ion separation device 20 (its separation region) is maintained at a pressure of between about 0.1mbar and 20 mbar. The use of an ion separation device configured to separate ions as they pass through a (relatively high pressure) gas advantageously means that m/z separation can be achieved without the need for high vacuum pumping. Thus, embodiments provide a particularly simple and low cost method of analyzing particles, and a particularly simple and low cost analytical instrument.

The ion separation device 20 may be configured to use one or more time-varying electric fields to push ions through the gas such that the ions are separated according to a mass-to-charge ratio (m/z). In a particular embodiment, the ion separation device 20 comprises a Traveling Wave (TW) ion separation device.

The ion separation device 20 may comprise a plurality of electrodes, for example in the form of ion guides. The electrodes of the ion guide may define an ion path along which ions are transported in use.

The ion separation device 20 may comprise any suitable ion guide, such as an ion guide comprising a plurality of electrodes, such as a stacked ring (or stacked plate) ion guide, or a segmented quadrupole ion guide, each electrode having an aperture through which ions are transported in use. The segmented quadrupole ion guide can provide a more uniform radial distribution of charge states. The ion guide may be a linear (straight) ion guide, or a closed loop or cyclic ion guide.

The ion separation device 20 may include one or more voltage sources configured to apply voltages to electrodes of the ion guide. A voltage may be continuously applied to the electrodes of the device 20 so as to form a wave along the barrier of movement of the device in a first direction so as to push ions through the gas in the first direction.

In the case where the ion guide comprises a linear ion guide, the first direction may be an axial direction along the length of the ion guide. A traveling wave may be formed along the device 20, moving in a direction from the inlet end to the outlet end of the separation device 20. Moving the DC barrier may push ions through the gas toward the outlet end of the separation device 20. In the case where the ion guide comprises a closed loop or cyclic ion guide, the first direction may be a circumferential (azimuthal) direction around the circumference of the ion guide. Moving the DC barrier may push ions around the ion guide one or more times.

The ions may be separated according to their mass to charge ratios such that ions of different mass to charge ratios arrive at the exit region of the ion guide at different times, for example such that ions of relatively higher mass to charge ratios arrive at the exit region before ions of relatively lower mass to charge ratios (or such that ions of relatively lower values of mass to charge ratios arrive at the exit region before ions of relatively higher values of mass to charge ratios).

A plurality of DC barriers may be sequentially applied to (and travel along or around) the separating apparatus 20. The parameters of the DC potential may be selected such that each ion passes through the DC travelling potential multiple times as it travels through the separation device 20, i.e. the ions will roll over multiple DC barriers. This can be achieved, for example, by selecting appropriate speed and voltage amplitude for the DC barrier.

In embodiments, the amplitude of each DC voltage may be about (i)<1V; (ii) 1V to 10V; (iii) 10V to 20V; (iv) 20V to 30V; (V) 30V to 40V; (vi) 40V to 50V; (vii) 50V to 60V; (viii) 60V to 70V; (ix) 70V to 80V; (x) 80V to 90V; (xi) 90V to 100V; and (xii)>100V. Each voltage may be applied to the electrode about 10 ^-4 ms to 5ms. The waves may have any suitable velocity, such as about (i)<50m/s; (ii) 50m/s to 100m/s; (iii) 100m/s to 200m/s; (iv) 200m/s to 300m/s; (v) 300m/s to 400m/s; (vi) 400m/s to 500m/s; (vii) 500m/s to 1000m/s; (viii) 1000m/s to 1500m/s; (ix) 1500m/s to 2000m/s; or (x)>2000m/s。

Traveling Wave (TW) -induced ion transport depends on both ion mobility and mass to charge ratio (m/z). As described, for example, in US 2020/0161119 (the contents of which are incorporated herein by reference), the m/z dependence has previously been characterised in terms of velocity relaxation, which increases with the mass-to-charge ratio (m/z) of the ions (for a selected set of operating parameters). Thus, the operating parameters may be adjusted to produce a separation dictated by m/z or mobility, or a combination of both.

The separation characteristics of such devices are conveniently parameterized according to the following parameters:

Wherein V is ₀ Is the applied wave amplitude, v is the wave velocity, λ is the wavelength, and K and m/z are the mobility and mass-to-charge ratio of the particle, respectively.

Figure 2 shows the percentage reduction of the average particle velocity as a function of alpha and gamma for a one-dimensional smooth moving traveling wave device. Qualitative behavior in more realistic devices where ions can move off-axis and where waves move forward in a stepwise fashion rather than smoothly, is similar and can be characterized by numerical or simulation.

At higher values of alpha the degree of velocity relaxation (and thus the dependence on the m/z ratio) increases. Thus, in an embodiment, the parameters of the DC potential may be selected such that ions are (predominantly) separated according to mass to charge ratio.

The applied travelling wave may be smoothly moved or stepped. For step waves, the step size can be adjusted to optimize the relative amounts of mass-to-charge ratio (m/z) and ion mobility separation.

The ion separation device 20 may operate with or without radially confining the RF voltage. When the ion separation device 20 is operated without radially confining the RF voltage, the traveling wave conditions may be selected to produce sufficient m/z separation and confinement at the same time.

When the ion separation device 20 is operated with a radially-limited RF voltage, the ion separation device 20 may include one or more additional voltage sources configured to supply AC or RF voltages to the electrodes. The opposite phase of the AC or RF voltage may be applied to successive electrodes. The AC or RF voltage may have an amplitude selected from the group consisting of: (i) <50V peak-to-peak; (ii) 50V peak-to-100V peak-to-peak; (iii) 100V peak-to-150V peak-to-peak; (iv) 150V peak-to-200V peak-to-peak; (V) 200V peak-to-250V peak-to-peak; (vi) 250V peak-to-300V peak-to-peak; (vii) 300V peak-to-350V peak-to-peak; (viii) 350V peak-to-400V peak-to-peak; (ix) 400V peak-to-450V peak-to-peak; (x) 450V peak-to-500V peak-to-peak; and (xi) >500V peak-to-peak. The AC or RF voltage may have a frequency selected from the group consisting of: (i) <100kHz; (ii) 100kHz to 200kHz; (iii) 200kHz to 300kHz; (iv) 300kHz to 400kHz; (v) 400kHz to 500kHz; (vi) 0.5MHz to 1.0MHz; (vii) 1.0MHz to 1.5MHz; (viii) 1.5MHz to 2.0MHz; (ix) 2.0MHz to 2.5MHz; (x) 2.5MHz to 3.0MHz; (xi) 3.0MHz to 3.5MHz; (xii) 3.5MHz to 4.0MHz; (xiii) 4.0MHz to 4.5MHz; (xiv) 4.5MHz to 5.0MHz; (xv) 5.0MHz to 5.5MHz; (xvi) 5.5MHz to 6.0MHz; (xvii) 6.0MHz to 6.5MHz; (xviii) 6.5MHz to 7.0MHz; (xix) 7.0MHz to 7.5MHz; (xx) 7.5MHz to 8.0MHz; (xxi) 8.0MHz to 8.5MHz; (xxii) 8.5MHz to 9.0MHz; (xxiii) 9.0MHz to 9.5MHz; (xxiv) 9.5MHz to 10.0MHz; and (xxv) >10.0MHz.

The ion isolation device 20 may be configured to (receive and) isolate ion packets (packets). Where the ion source 10 comprises a pulsed ion source, ion packets may be generated by the ion source 10.

However, in certain embodiments, wherein the ion source 10 is a pulsed ion source or a continuous ion source, the analysis apparatus further comprises an ion trap (not shown in fig. 1), which may be arranged between the ion source 10 and the ion separation device 20. Ions generated by the ion source 10 may accumulate in the ion trap and the ion trap may be configured to deliver ion packets to the ion isolation apparatus 20, such as by periodically delivering ion packets to the ion isolation apparatus 20. Each ion packet may comprise ions of a mixture of particles to be analyzed.

The ion trap may comprise any suitable ion trap such as, for example, (i) a 2D or linear quadrupole ion trap; (ii) a Paul or 3D quadrupole ion trap; (iii) penning ion trap; (iv) a stacked ring ion trap; or (v) another type of ion trap.

Thus, particular embodiments employ a gas-filled ion separation device 20 for mass-to-charge ratio separation, wherein a traveling wave of voltage (TW) propels ions along the device 20. The apparatus 20 may be implemented between an ion source 10, such as an electrospray ionization (ESI) ion source, and a detector 30. The ions may be delivered to the TW device 20 in the form of packets for subsequent separation. The TW device 20 may be operated under conditions such that a substantially temporary m/z separation is achieved during ion propulsion through the gas. Ions may then be detected.

This arrangement does not require high vacuum levels or conventional mass analyzers. The ion separation device 20 of the various embodiments advantageously requires relatively low voltages and does not require precise control of these voltages. Thus, embodiments provide a particularly simple and low cost method of analyzing particles, and a particularly simple and low cost analytical instrument.

Fig. 3 schematically shows an analysis instrument in the form of a mass spectrometer and/or an ion mobility spectrometer according to these embodiments. As shown in fig. 3, the instrument may include an ambient ion source 10 in the form of a nano ESI ion source. Ions generated by the ion source 10 may be sampled into an initial vacuum chamber 11 of the instrument via an atmospheric pressure interface 12.

The initial vacuum chamber 11 may be operated at (maintained at) any suitable pressure, such as (i) <1mbar; (ii) from 1mbar to 2mbar; (iii) from 2mbar to 5mbar; (iv) 5mbar to 10mbar; (v) 10mbar to 15mbar; (vi) 15mbar to 20mbar; (vii) 20mbar to 25mbar; (viii) 25mbar to 30mbar; or (ix) >30mbar. In a particular embodiment, the initial vacuum chamber 11 is maintained at a pressure of between about 1mbar and 20 mbar. For this purpose, as shown in fig. 3, the initial vacuum chamber 11 may be pumped by a backing pump (rough pump) 13.

As also shown in fig. 3, one or more ion guides or other ion optical elements 14 are provided in the initial vacuum chamber 11 (e.g., in the form of dual combined ion guides), wherein the one or more ion guides or other ion optical elements 14 are configured to transfer ions received from the atmospheric pressure interface 12 to (and through) an aperture 15 disposed between the initial vacuum chamber 11 and a second vacuum chamber 21 of the analytical instrument.

In the embodiment shown in fig. 3, the ion separation device 20 is a Traveling Wave (TW) ion separation device that (as described above) includes a plurality of electrodes in the form of ion guides 22. The ion guide 22 may be arranged within the second vacuum chamber 22 and the second vacuum chamber 21 may be maintained at a pressure of between about 0.1mbar and 20 mbar.

Once separated by the ion separation device 20, the ions are transferred to the detector 30 via a second aperture 23 arranged between the second vacuum chamber 21 and the third vacuum chamber 31 of the analysis instrument.

The third vacuum chamber accommodates (at least) the detection surface 32 of the detector 30 and may be maintained at a pressure of about 0.0001 mbar. To this end, as shown in fig. 3, the initial third chamber 31 may be pumped by a turbo molecular pump 33.

In various further embodiments, the first physicochemical property (described above) is ion mobility. In these embodiments, the ion separation device 20 may include an ion mobility separator configured to separate ions according to their ion mobility.

The ion mobility separator may comprise a drift tube that may be pressurized with a gas. An electric field, for example comprising a DC voltage gradient and/or a travelling DC voltage wave, may be arranged to push ions along the length of the ion mobility separator, i.e. through the gas, such that the ions are separated according to their ion mobility. Ions may optionally be pushed against the reverse airflow.

Alternatively, the gas flow may be arranged to push ions along the length of the ion mobility separator, while an electric field, for example comprising a DC voltage gradient and/or a travelling DC voltage wave, may be arranged to resist the gas flow so that ions are separated according to their ion mobility.

The ion mobility separator may operate in line with the ion beam path of the analytical instrument. For example, in particular embodiments, the ion mobility separator may be substantially in accordance with the mass-to-charge ratio separator configuration described above and shown in fig. 3, except that the separator 20 (e.g., TW device 20) may be operated under conditions such that a substantially temporary ion mobility separation is achieved during ion advancement through the gas.

Alternatively, the ion mobility separator may comprise a circulating (closed loop) ion separator. The Ion mobility separation Device may comprise any or all of the features of the Ion separation Device disclosed in US 9984861 entitled "Ion Entry/Exit Device" in the name of Micromass english limited (Micromass UK Limited), the entire contents of which are incorporated herein by reference. Higher degrees of separation, and thus higher ion mobility resolution, can be achieved using a circulating ion mobility separator.

Returning to fig. 1, the detector 30 is configured to detect ions received from the ion isolation apparatus 20. The analysis instrument may be configured such that ions eluted from the ion separation device 20 are detected by the detector 30.

Ions may reach the ion detector 30 after a time determined by their velocity and travel distance. Thus, the transit time may be related to (and may enable determination of) the first physicochemical property of the ion.

The detector 30 may be configured to output a signal from which the transit time (i.e., the "drift time") of each ion may be measured. For example, the detector 30 may be configured to detect the intensity of each ion received at the detector 30 as a function of time. Each ion reaching the detector 30 may be sampled by the detector 30 and the signal from the detector 30 may be digitized, for example using an ADC (analog to digital converter).

The processor may then determine a value indicative of the transit time (e.g., time of flight) of the ion. This may use a known or measured start time with the time at which the ion was detected. For example, in the case where an ion produces a peak having a certain width, the centroid or weighted average of the peak may be determined (from the digitized signal) and used as the detection time for the ion. The start time may be subtracted from the detection time to determine the transit time.

Thus, in various embodiments, the instrument is configured to measure the transit time (i.e., the "drift time") of each ion using the detector 30.

The detector 30 is a charge-resolving ion detector configured to determine the charge (i.e., the "state of charge" or "number of charges") of each (individual) ion. The charge-resolving ion detector may be configured to output a signal from which the charge (i.e., the "state of charge" or "charge number") of each ion may be determined.

The charge of each ion may be determined from the same signal from which the transit time of the ion was measured or from different signals.

In the case where the charge of the ion is determined using the same signal from which the transit time of the ion is determined, the charge of the ion may be determined from the intensity, amplitude and/or area of the (digitized) signal. In practice, the area may be a more accurate measurement than the amplitude or intensity, for example due to limitations of the acquisition electronics, such as sampling rate and ADC number of bits.

The charge state may be determined from the area and/or intensity of the signal, as the response of some detectors may vary with the charge state. For example, a faraday cup will directly convert the charge into a signal. Furthermore, standard ToF detectors (such as e.g. electron multipliers) have an impact energy dependent response, and the impact energy may depend on the charge.

Thus, in these embodiments, the charge-resolving ion detector 30 may comprise (i) a faraday cup or a cylindrical electrode detector; (ii) an electron multiplier detector; (iii) a photomultiplier or scintillation counter detector; and/or (iv) a Superconducting Tunnel Junction (STJ) detector.

In the case of determining the charge of an ion using a different signal from that from which the transit time of the ion is determined, the analysis instrument may comprise two ion detectors. The first ion detector may be configured to determine the charge of each ion and the second detector may be configured to determine the transit time of each ion. The first ion detector may be arranged upstream of (and in proximity to) the second ion detector.

In these embodiments, the second ion detector may be configured substantially as described above, and may comprise, for example, any suitable ion detector, such as, for example, (i) a faraday cup or a cylindrical electrode detector; (ii) an electron multiplier detector; (iii) a photomultiplier or scintillation counter detector; and/or (iv) a Superconducting Tunnel Junction (STJ) detector.

The first charge-resolving ion detector may comprise any suitable charge-resolving ion detector configured to output a signal from which the charge of each ion may be determined. The first charge-resolving ion detector may comprise a non-destructive charge-resolving ion detector, i.e. such that ions detected by the first ion detector will continue to be detected by (and generate a signal on) the second detector.

The charge-resolving ion detector may comprise, for example, an inductive charge detector configured such that passing ions will induce charge within the detector. In certain embodiments, the charge-resolving ion detector comprises a sensing plate or tube.

An induced charge detector may also be used to determine the transit time of the ions and their charge. For example, the shape of the signal derived from the induced charge detector may give mass-to-charge ratio (m/z) information, e.g. where the time difference between the two (positive and negative) peaks is actually a time-of-flight measurement, from which the mass-to-charge ratio (m/z) can be determined.

It will thus be appreciated that, according to an embodiment, the transit time of each (individual) ion through the ion separation device 20 is determined, as well as the charge state of that ion. The transit time (i.e., the "drift time") and charge (i.e., the "state of charge" or "number of charges") of each ion are then used (e.g., combined) on an ion-by-ion basis, for example, to determine a second physical and chemical property of each ion.

To facilitate such ion-by-ion processing, ion flux at one or more detectors may be controlled such that (some, most, or all) individual ions are distinguishable from one another when detected by the one or more detectors.

In the case of separating ions, for example, according to their mass-to-charge ratio (m/z), i.e. in the case where the first physicochemical property comprises a mass-to-charge ratio, the transit time of each ion will be related to its mass-to-charge ratio. Thus, by combining the transit time and charge of an ion, the mass (or mass-related property) of the ion can be determined.

In the case of ion separation according to ion mobility of the ions (i.e. in the case of the first physicochemical property comprising ion mobility), the transit time of each (individual) ion will be related to its ion mobility. By combining the transit time and charge of an ion, the collision or reaction cross-section (or a property related to the collision or reaction cross-section) of the ion can be determined.

The transit time and charge may be combined in any suitable manner to obtain the second physical and chemical property. For example, in the case of a ToFMS, if the time measurement is first converted to a mass-to-charge ratio (m/z), the value of the mass-to-charge ratio (m/z) may be multiplied by the state of charge to obtain the mass (m). However, if the initial time measurement is scaled, the time measurement will be scaled, for example, by the square root of the charge, to account for the non-linear relationship between the time measurement and the mass-to-charge ratio (m/z).

According to particular embodiments, the process is repeated for each (individual) ion of the plurality of ions, e.g., to determine a second physical chemical property (e.g., mass, or collision or reaction cross section) of each individual ion, and the results are combined (e.g., summed, binned, and/or histogram) to produce a spectrum (such as a mass spectrum, or collision or reaction cross section spectrum) of the ion being analyzed.

Thus, according to various embodiments, the transit time (i.e., the "drift time") and the charge (i.e., the "state of charge" or the "number of charges") of each (individual) ion of the plurality of ions are used (e.g., combined) to determine a second physical chemical property of each (individual) ion of the plurality of ions. The so determined second physical and chemical properties of each (individual) ion of the plurality of ions are then used (combined) to produce a spectrum (e.g., mass spectrum, or collision or reaction cross-section spectrum).

Embodiments utilize the inherent speed of the separation-based method and also utilize the charge state resolution provided by the charge-resolving ion detector (in addition to the first physicochemical resolution of the separation device 20) to resolve ions. Even if the ion separator 20 lacks sufficient resolution to resolve different charge states at a first physicochemical property, this may allow ions having similar or identical values of the first physicochemical property (e.g., mass-to-charge ratio (m/z)) but having different charges (z) to be resolved at a second physicochemical property (e.g., mass). For example, even if the ion separator 20 lacks sufficient m/z resolution to resolve different charge states, this may allow for resolving ions having similar or identical mass-to-charge ratios (m/z) but different charges (z).

It should be appreciated that the various embodiments take advantage of the inherent speed of separation methods such as, but not limited to, time-of-flight mass spectrometry (ToF-MS).

Using time of flight mass spectrometry (ToF-MS) as an example, ions may enter a time of flight (ToF) mass analyzer at a time determined by the electronics of the mass analyzer. The start time is measured or known. The ions are separated according to m/z such that ions with different mass to charge ratios arrive at the detector at different times, wherein the different arrival times are measured. Typically, data from multiple separations will be summed and/or binned into histograms to provide a time-of-flight (ToF) spectrum, which may then be converted to an m/z spectrum.

However, in an embodiment, the time-of-flight measurement of each (individual) ion is combined with the charge state of each (individual) ion before summing and/or binning the data of the plurality of ions into the histogram in order to generate a final spectrum (e.g., mass spectrum).

The charge state information for each (individual) ion may be determined based on the intensity of the signal from the same detection event used to measure the time of flight. Alternatively, a separate detector may be used to independently measure the charge state.

The intrinsic speed of a single time-of-flight mass spectrometry (ToF-MS) experiment is several orders of magnitude faster than a trapping experiment, such as CDMS, so that significant improvements in sample analysis time are expected even with the limitation that only one ion is analyzed per experiment. Furthermore, in time of flight mass spectrometry (ToF-MS), ions follow a unique flight path and/or trajectory, which means that multiple ions can be analyzed in the same time of flight mass spectrometry (ToF-MS) experiment, as long as signals from different ions can be distinguished at the detector.

Fig. 4 schematically illustrates an analytical instrument configured according to an embodiment. As shown in fig. 4, the analysis instrument includes a temporary ion separation device 20 (such as a ToF mass analyzer) and an ion detector 30 downstream of the ion separation device 20. The ion separation device 20 is configured to separate ions according to a first physicochemical property (such as m/z) as the ions pass through the ion separation device.

The ion detector 30 comprises a charge-resolving ion detector configured to detect ions so as to determine the charge of the ions. Further, the detector 30 is configured to measure the drift time of the ions in order to determine the transit time of the ions. For example, a single detector 30 may have charge-dependent characteristics and may be configured to output a signal from which the charge of the ion may be determined and from which the transit time of the ion may be measured.

In various embodiments, the charge of the ions may be determined from the area of the signal output from the detector 30, and the drift time of the ions may be determined by a weighted average of the signals.

As shown in fig. 4, the transit time and charge of the ions are combined to determine a second physical chemical property of the ions, such as mass. This occurs before summing and/or binning data from that ion with data from other ions into a histogram or spectrum across multiple separations. For example, if the charge state of the detected ions is linear with the area of the signal from the detector 30, the product of the transit time and the area of the signal may be determined and binned into histograms. Exemplary detectors whose charge state is linear with signal include faraday cups and inductive "audiometric" electrodes. Superconducting Tunnel Junction (STJ) detectors also exhibit this property.

Fig. 5 schematically illustrates an analytical instrument configured according to an alternative embodiment. The analysis instrument includes a temporary ion isolation device 20 (which may be configured as described above), a first detector 30 and a second detector 40 downstream of the ion isolation device 20.

The first detector 30 comprises a charge-resolving ion detector configured to measure or determine the charge state of ions. The second detector 40 is configured to measure or determine the time of flight or arrival of ions.

As shown in fig. 5, the time of flight or arrival time and charge state of the ions are combined to determine a second physical chemical property of the ions, such as mass. This is done before summing and/or binning the data of the ion with data from other ions into histograms (spectra) across multiple separations.

Fig. 6 shows simulated data from a simple audiometric tube. Particles of mass 4MDa and charge 200 were accelerated at 5kV and passed through the tube. The tube has an inner diameter of 5mm and a length of 10 mm. The resulting induced charge and associated current are shown in fig. 6.

As shown in fig. 6, simulations indicate that individual charge state resolution is possible by the method as described herein. For example, assuming that the response is linear with charge, the total induced charge diffusion is equal to about 2/3 of the charge state, considering that non-divergent ions enter the tube along the axis or offset of 1 mm.

Various alternative embodiments are possible.

For example, in various embodiments, the charge of the ions may be reduced prior to entering the ion separation device 20. This can be done as follows: (i) to reduce the charge of the ions to a point at which the peaks of the charge states can be distinguished, (ii) to increase the m/z and hence the velocity relaxation effect, and/or (iii) to increase the percent charge difference between the unresolved charge states to a point at which the unresolved charge states can be distinguished by a low charge resolution detector.

Charge reduction may be induced by any suitable technique, such as, for example, solution additives (charge reducing agents and/or charge reducing surfactants) and/or reactant vapors (containing neutral and/or ionized molecules). Evaporation of the solution additives may also result in the formation of suitable reactant vapors.

Although various specific embodiments have been described in terms of T-wave mass-to-charge ratio separation, other separation or filtration devices utilizing a time-dependent electric field in an aeration cell may be employed, such as where at least a portion of the ion motion exhibits significant velocity relaxation. Thus, for example, the ion separation device 20 may comprise an ion trap and/or a sector device, such as, for example, a 3D quadrupole ion trap, a linear ion trap, a toroidal ion trap, a pulsed sector electric filter, a parallel electrode filter, a coaxial electrode filter, or the like, optionally driven by a substantially pulsed electric field.

Although the above embodiments focus on time of flight mass spectrometry (ToF-MS) as the separation method, the separation may be any time-based method such as, for example, high pressure m/z separation, scanning quadrupoles, and the like.

The scanning resolving quadrupole will only pass ions within a limited mass-to-charge ratio (m/z) range at any given time because the scanning resolving quadrupole operates as a mass-to-charge ratio (m/z) filter. Varying (scanning) the transmitted mass-to-charge ratio (m/z) range over time results in ions having different mass-to-charge ratios (m/z) reaching the detector at different times. In the case of an ion detector having charge resolving properties, i.e. in a manner corresponding to that described above, the determined charge of each ion may be combined with the mass to charge ratio (m/z) of the ion in order to determine the mass of each ion.

In addition, other physicochemical properties may benefit from the method, such as, for example, ion Mobility Spectrometry (IMS). In IMS, ions are substantially separated in time according to the cross-sectional charge ratio, so measuring charge and arrival time will allow overlapping mobility spectra to be converted to higher resolution cross-sectional spectra with improved cross-sectional measurements.

Although simulations are shown above for a single audiometric device, it should be appreciated that significant improvements may be made by using multiple audiometric devices, thereby increasing the accuracy of charge state measurements and reducing the effects of electronic noise.

In various embodiments, the characteristics of the induced charge and/or current distribution may be used to calculate the mass-to-charge ratio (m/z) of each (individual) ion of the one or more ions. For example, referring to FIG. 5, the shape of the signal obtained from sense tube 30 may give mass to charge ratio (m/z) information. For example, the time difference between two (positive and negative) peaks is actually a time-of-flight measurement from which the mass-to-charge ratio (m/z) can be determined.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the invention as set forth in the following claims.

Claims

1. A method of analyzing ions, the method comprising:

the transit time and the charge of the ion are used to determine a second physical and chemical property of the ion.

2. The method of claim 1, wherein measuring the transit time of the ions through the ion separation device comprises measuring the transit time of the ions using the charge-resolving ion detector.

3. The method of any one of the preceding claims, wherein the charge-resolving ion detector comprises (i) a faraday cup or a cylindrical electrode detector; (ii) an electron multiplier detector; (iii) a photomultiplier or scintillation counter detector; and/or (iv) a Superconducting Tunnel Junction (STJ) detector.

4. The method of any one of the preceding claims, wherein the method comprises determining the charge of the ion from the intensity, amplitude and/or area of a signal generated by the charge-resolving ion detector when the ion is detected.

5. The method of claim 1, wherein the step of measuring the transit time of the ions through the ion separation device comprises measuring the transit time of the ions using a second ion detector.

6. The method of claim 5, wherein the charge-resolving ion detector comprises an inductive charge detector.

7. The method of claim 5 or 6, wherein the second ion detector comprises (i) a faraday cup or a cylindrical electrode detector; (ii) an electron multiplier detector; (iii) a photomultiplier or scintillation counter detector; and/or (iv) a Superconducting Tunnel Junction (STJ) detector.

8. The method of any of the preceding claims, wherein determining the second physical property of the ion using the transit time and the charge of the ion comprises combining the transit time and the charge of the ion to determine the second physical property of the ion.

9. A method according to any preceding claim, further comprising controlling ion flux at the ion detector such that individual ions are distinguishable from one another when detected by the ion detector.

10. The method according to any of the preceding claims, wherein the method comprises:

for each ion of the plurality of ions:

determining the second physical and chemical properties of the ion using the transit time and the charge of the ion; and

combining the determined second physical and chemical properties of each ion of the plurality of ions to produce a spectrum of the ions.

11. The method of any one of the preceding claims, wherein the first physicochemical property is mass to charge ratio (m/z).

12. The method of claim 11, wherein the ion separation device comprises a time of flight (ToF) separation device configured to separate ions according to their mass to charge ratio.

13. The method of claim 11, wherein the ion separation device comprises an ion separation device in which one or more time-varying electric fields are used to push ions through a gas such that ions are separated according to mass to charge ratio.

14. The method of claim 13, wherein the ion separation device comprises a traveling wave separation device, and wherein the method comprises sequentially applying one or more voltages to different electrodes of the device so as to form one or more travel barriers that move along the device so as to push ions through the separation device.

15. The method of any one of claims 1 to 10, wherein the first physicochemical property is ion mobility.

16. The method of claim 15, wherein the ion separation device is an ion mobility separation device configured to separate ions according to their ion mobility.

17. A method of analyzing ions, the method comprising:

detecting ions using an induced charge detector;

determining a transit time of the ions from the signal generated by the induced charge detector when the ions are detected; and

18. A method of analyzing ions, the method comprising:

a second physical chemistry property of the ion is determined using the first value of the first physical chemistry property of the ion and the charge.

19. The method of any one of the preceding claims, wherein the second physical chemical property comprises mass.

20. The method of any one of claims 1 to 18, wherein the second physical chemical property comprises a collision or reaction cross section.

21. The method of any one of the preceding claims, wherein one or more of the ions has a mass of >1 MDa.

22. An analytical instrument, the analytical instrument comprising:

an ion separation device, wherein the ion separation device is configured to separate ions according to a first physicochemical property as the ions are passed through the ion separation device; and

Wherein the analysis instrument is configured to measure the transit time of ions through the ion separation device to determine the transit time of the ions;

wherein the ion detector comprises a charge-resolving ion detector configured to determine the charge of the ions; and is also provided with