CN1788327A - Linear ion trap and mass analyzer systems and methods - Google Patents

Abstract

A new shape of ion trap and its use as a mass spectrometer are described. Ion traps can be combined linearly and in parallel to form systems for mass storage, analysis, fragmentation, separation, and the like. The ion trap has a simple rectilinear geometry and has a high trapping capacity. It is operable to provide mass analysis in both the mass selection stable mode and the mass selection unstable mode. An array of multiple ion traps allows a combination of multiple gas phase processes to be applied to trapped ions to achieve high sensitivity, high selectivity, and/or higher throughput in ion analysis.

Description

Linear ion trap and mass analyzer systems and methods

This application claims priority to Provisional Application Serial No. 60/439,350 filed January 10,2003.

technical field

The present invention generally relates to an ion trap and an ion trap mass analyzer, in particular to a linear ion trap and a mass analyzer using the linear ion trap.

Background technique

A three-dimensional ion trap with a quadrupole field in both r and z (in a polar coordinate system) exerts a linear force on the ions and can be used as an ion trap for ions with a wider or narrower range of mass/charge ratios. The shape of the field is usually determined by a set of three electrodes consisting of a ring electrode and two hyperbolic end cap electrodes. Such a device is called a Paul or quadrupole ion trap. In a simpler alternative, cylindrical ion traps (CITs), the inner surface of the ring is cylindrical and the end caps are flat.

Paul traps and cylindrical ion traps are known to have some disadvantages. They include limitations on the number of ions that can be trapped and low efficiency of external ion injection. In order to minimize space charge effects and thus achieve high resolution in commercial mass spectrometers, only 500 or fewer ions can be trapped in a typical experiment. All ions injected through the entrance aperture of the end cap electrode experience the RF field, and only those ions injected at the proper RF phase are efficiently trapped. Collisions with the buffer gas aid in trapping, and generally the trapping efficiency of continuously injected ions is less than 5%, and in many cases even less.

Another type of ion trap, the linear ion trap, focuses on these problems. A linear ion trap consists of elongated spaced apart multipole rods to which RF and DC voltages are applied to trap ions in the volume defined by the multipole rods. A linear ion trap with an elongated multipole rod arrangement is described in US Patent 6,177,668. The two-dimensional RF field radially confines these trapped ions within the mass range of interest. These ions are contained axially within the volume defined by the rod by the dc field applied to the end electrodes. Trapped ions are mass-selectively axially ejected by mixing of the ions' degrees of freedom induced by fringing fields. US Patent 6403955 is directed to a quadrupole ion trap mass spectrometer, the trapping volume of which is defined by spaced rods. The movement of the ions in the trapping volume produces the current-like properties of the ions. US Patent 5420425 describes a linear quadrupole ion trap in which ions are ejected through elongated openings formed in one of the spaced linear rods defining a trapping volume. All of the above ion traps, with the exception of the cylindrical ion trap, require precise mechanical processing such as machining, assembly, etc., which are more complicated when manufacturing small portable mass analyzers using ion traps.

US Patent 6483109 discloses a multi-segment mass spectrometer. A preferred embodiment comprises a pulsed ion source coupled to a linear array of mass selective ion trap arrangements, at least one trap coupled to an external ion detector. Each ion trap is configured with storage cells for the trapping of ions of interest interspersed between a pair of guard cells aligned along its z-axis. Radio frequency (RF) and direct current (DC) voltages are applied to the electrodes of the ion trap device to retain ions in the storage cells. Each trapping cell has a subregion in which the dynamic motion of ions along the z-direction exhibits an m/z-dependent resonance frequency, allowing the motion of ions to be selectively excited by the m/z value. The AC voltage can be combined with time-resolved changes in the applied DC voltage so that individual trapping cells can be switched between ion trapping, mass selective and ion fragmentation modes. Ions can be selectively transported in ion traps and selectively dissociated in each trap to enable ^MSn operation. Linear arrays of ion traps include harmonic linear traps (HLTs) consisting of several open cells. The cells of HLTs consist of parallelepiped-shaped rectangular electrodes oriented on the ZX and ZY planes, while there are no rectangular electrodes on the XY plane.

Contents of the invention

A general object of the present invention is to provide an ion trap with a new and simple geometry.

Another object of the present invention is to provide an ion trap which allows trapping gas phase ions with high trapping power in a simple geometry.

Another object of the present invention is to provide an ion trap operable to provide mass analysis in a mass selective unstable mode, while being identical to other traps in a mass selective stable mode and in a destruction detection mode. Alternatively, mass analysis can be easily accomplished using non-destructive detection mode when using hyperbolic and cylindrical ion traps.

Another object of the present invention is to provide a linear ion trap array for mass storage, mass analysis and mass separation.

Yet another object of the present invention is to provide a linear ion trap array that allows a combination of multiple gas phase processes to be applied on the ion trap to achieve high sensitivity, high selectivity and/or higher ion analysis throughput.

providing a linear ion trap comprising x and y counter electrodes spaced apart on zx and zy planes to define a trapping volume, an RF voltage source for applying an RF voltage between the x and y counter electrodes, to generate an RF trapping field on an xy-plane end electrode at the end of a trapping volume defined by said pair of x and y electrodes, a DC voltage source for applying a voltage to at least said end electrode to provide a DC trapping along the z-axis To obtain a field whereby ions are trapped within the trapping volume, an AC voltage source is used to apply an AC voltage to at least one pair of said x or y electrodes to excite ions in the corresponding zx or zy plane. The terminal electrodes may comprise planar electrode plates or pairs or combinations thereof arranged in the xy plane. An AC voltage can be applied to the end electrodes to excite ions in the z direction. The Rf electrodes and end plates may include slits or openings to eject ions in the x, y and z directions.

A multi-segment ion processing system is provided that includes several linear ion traps interconnected so that ions can move between the traps. The traps are arranged in series or parallel or a combination thereof so that ions move between the traps in x, y or z direction.

Description of drawings

The present invention can be clearly understood by reading the following description with reference to the accompanying drawings, in which:

Figures 1a-b show a linear ion trap that allows injection/exit of ions along the z-axis and DC trapping voltage;

Figures 2a-b show a linear ion trap with a slit along the x-axis for ion injection/exit and a DC trapping voltage;

Figure 3a-b shows a linear ion trap with three RF sections and DC trapping voltage;

Figures 4a-b show a linear ion trap with three RF sections and end plates and a DC trapping voltage;

Figure 5 schematically shows a linear ion trap of the type shown in Figure 2 in a mass analysis system;

Figure 6 shows a mass spectrum obtained using the system in Figure 5 for acetophenone;

Figure 7 shows the mass spectrum of the parent m/z105 ion and the mass spectrum of the fragment ion m/z105 of acetophenone obtained by CID in the system of Figure 5;

Fig. 8 shows the ionization effect to dichlorobenzene with different time for obtaining the ion of mass m/z111;

Figure 9 shows a plot of stability using RF and DC voltages for a linear ion trap (defined below);

Figures 10a-10b show AC and RF voltages for mass selective ion ejection along the z-axis through apertures in the end electrodes of the linear ion trap of Figure 1;

Figure 11 shows a linear ion trap for mass selective ejection through slits in the end electrodes, AC voltage is applied between the x electrodes;

Figure 12 shows a linear ion trap for mass selective ejection through slits in the end electrodes, AC voltage is applied between the x or y electrodes;

Figure 13 shows a linear ion trap for scanning ions through slits in the x RF electrodes by applying an AC scan voltage on the x electrodes;

Figure 14 shows a linear ion trap for scanning ions through slits in respective x or y RF electrodes by applying an AC scanning voltage across the respective electrodes;

Figure 15 shows a linear ion trap with slits on the RF and end electrodes to allow ions to be ejected in any direction;

Figure 16 shows a cubic linear ion trap with intersecting slits on each electrode whereby application of RF and AC voltages between selected pairs of electrodes allows ions to be ejected in the x, y or z direction;

Figure 17 shows a series combination of linear ion traps and applied DC voltage;

Figure 18 schematically shows a serial array of ion traps of the same size;

Figures 19a-e schematically illustrate various modes of operation for three linear ion traps connected in series;

Figure 20 schematically illustrates a series array of linear ion traps of different sizes;

Figure 21 is a perspective view showing a parallel array of linear ion traps;

Figure 22 is a perspective view showing a parallel array of linear ion traps performing a series of operations on a population of ions;

Figure 23 is a perspective view showing a parallel array of two linear ion traps arranged in series;

Figure 24 is a perspective view of a parallel array for measurement of ion mobility;

Figure 25 schematically shows a parallel array of linear ion traps of variable size for non-RF scanning multi-process analysis;

Figure 26 schematically illustrates another parallel array of linear ion traps of indeterminate size for non-RF scanning multi-process analysis; and

Figure 27 is a perspective view of linear ion traps arranged in a three-dimensional array.

Detailed ways

Figures 1-4 illustrate four linear ion trap geometries and as possible DC, AC and RF voltages applied to the electrode plates to trap and analyze ions. The trapping volume is defined by x and y pairs of spaced planar or planar RF electrodes 11, 12 and 13, 14 in the zx and zy planes. Ions are trapped in the z direction, Figures 1 and 2, by a DC voltage applied to planar or plate end electrodes 16, 17 arranged in the xy plane at the spaced ends of the trapping volume defined by the x,y pair of plates , or in FIG. 3 by a DC voltage applied together with RF to the components 18, 19, where each component 18, 19 comprises several pairs of planar or plate electrodes 11a, 12a and 13a, 13b. In Fig. 4, in addition to the RF section, planar or plate electrodes 16, 17 may be added. The DC trapping voltage is shown for each of the geometries in Figures 1b, 2b, 3b and 4b. Ions are trapped in the x, y direction by a quadrupole RF field generated by an RF voltage applied to the plate. As will be described immediately, ions may be ejected along the z-axis through openings formed in the end electrodes or along the x- or y-axis through openings formed in the x- or y-electrodes. The ions to be analyzed or excited can be formed within the trapping volume by ionizing the sample gas while it is within the volume, eg electron impact ionization, or the ions can be ionized externally injected into the ion trap. Ion traps usually work with the aid of a buffer gas. Thus when ions are injected into the ion trap they lose kinetic energy by collision with the buffer gas and are trapped by the DC potential well. When ions are trapped by the applied RF trapping voltage, AC and other waveforms can be applied to the electrodes to separate or excite ions in a mass selective manner as will be described in detail below. To perform an axial exit scan, the RF amplitude is swept while AC voltage is applied to the end plate. Axial ejection relies on the same principles that govern the axial ejection of linear traps with circular rod electrodes (US Patent 6177668). To perform an orthogonal ion ejection scan, the RF amplitude is swept and an AC voltage is applied to the set of electrodes including the openings. The AC amplitude can be swept for easy firing. Circuits for applying and controlling RF, AC and DC voltages are well known.

Ions trapped in the RIT can be moved out of the trap along the z-axis when the DC voltage is varied to remove the barrier at the end of the RIT. In the RIT structure in Figure 1, distortion of the RF field at the end of the RIT can cause undesired effects on trapped ions during processing such as partitioning, collision-induced decomposition (CID) or mass analysis. The addition of two end RF components 18 and 19 to the RIT as shown in Figures 3a and 4a can help to generate a uniform RF field for the central portion. A DC voltage applied across the three sections establishes a DC trapping potential, while ions are trapped in the central section, where various processes are performed on the ions. In cases where ion separation or ion focusing is required, end electrodes 16, 17 may be installed as shown in Fig. 4 . Thus FIGS. 1-4 and other illustrations to be described merely indicate voltages applied from suitable voltage sources.

To demonstrate the performance of the linear ion trap, an analytical system was constructed and tested using a linear ion trap (RIT) in an ITMS system sold by Thermo Finnigan in San Jose, CA. The RIT is of the type shown in FIG. 2 and the overall system is schematically shown in FIG. 5 . The half-distance between the two electrodes in the x-direction (x ₀ ) with the opening and between the two electrodes in the y-direction (y ₀ ) was 5.0 mm. The distance between the x and y electrodes and the z electrode is 1.6mm. The x and y electrodes are 40mm long. The slit on the x-electrode is 15 mm long and 1 mm wide and is positioned in the middle. The applied RF voltage has a frequency of 1.2 MHz and is applied between the y-electrode and ground. An AC bipolar field is applied between the two x-electrodes 11 , 12 . Figure 2, a positive DC voltage (50-200V) is applied across the z electrodes 16, 17 to trap positive ions in the RIT along the Z direction. Helium was added as a buffer gas until the indicated pressure was 3 x 10 ^-5 torr.

The volatile compounds to be analyzed in the experiment were infiltrated into the vacuum chamber until the indicated pressure was 2 x 10 ^-6 torr. Electrons emitted from the filament 21 are injected into the RIT to ionize the volatile compound to form ions within the RIT by electron impact (EI) ionization. Ions are trapped by the applied RF and DC fields. After a cooling period, the RF ramps up and ions are ejected through the slits on the x-electrode and detected by electron multiplier 22 equipped with switching dynode 23 . Figure 6 shows the mass spectrum of acetophenone recorded in the experiment. The spectrum shows relatively abundant molecular and fragment ions of the compound that would typically be seen in other types of mass spectrometry.

The MS/MS capability of RIT was also tested. The fragment ion m/z 105 of acetophenone was isolated using RF/DC isolation and then excited by applying an AC field with 0.35 V amplitude and 277 kHz frequency. Separation of precursor ions and spectra of MS/MS generated ions are shown in FIG. 7 .

The trapping ability was tested using the onset phenomenon of observable space charge effects ("spectral confinement") as a criterion for estimating the number of trapped ions. When the number of ions exceeds the spectral limit of the space charge, the resolution of the spectrum deteriorates significantly. To discern the spectral limitations of the RIT, ionization times of 0.1, 1, and 10 ms were used (0.1 is the shortest ionization time that can be set using the ITMS control circuit; when using ionization times longer than 10 ms, the signal strength exceeds the limit of the detector) Ionized dichlorobenzene. Trapped ions were mass analyzed in the RIT to generate spectra. As shown in Figure 8, the mass resolution was compared using the m/at 111 peak shape for each ionization time. When the ionization time was changed by a factor of 100 from 0.1 ms to 10 ms, the FWHM of the peak did not change, which means that the spectral limit (defined below) was not reached when the limit of the dynamic range of the electron multiplier was reached.

The relationship between the mass-to-charge ratio of trapped ions, the geometry of the RIT, and the applied RF and DC voltages can be estimated by the following equation.

$\frac{m}{e}=A_2\frac{8V_{\mathrm{RF}}}{q_x{x}_0^2{\mathrm{\Ω}}^2}$ Equation 1

$\frac{m}{e}=-{\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="A20038011012600171.png,A20038011012600172.png"\; state="\{\{state\}\}">A</figure-callout>}}_2\frac{16u_{\mathrm{DC}}}{a_x{x}_0^2{\mathrm{\&Omega;}}^2}$ Equation 2

where _A2 is the quadrupole expansion coefficient in the multipole expansion expression of the electric field, V _RF and U _DC are the amplitudes of the RF and DC voltages applied between the x and y electrodes, and a _x and q _x are the Mathieu parameters , _x0 is the center of the distance to the x-electrode, and Ω is the frequency of the applied RF. The long-term frequency ω _u (u=x or y) can be estimated by the following formula:

${\mathrm{\&omega;}}_u=\frac{1}{2}{\mathrm{\&beta;}}_u\mathrm{\&Omega;}$ Equation 3

in

${\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="u"\; filenames="A20038011012600171.png,A20038011012600172.png"\; state="\{\{state\}\}">u</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}}{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; q</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>}}}$

$+\frac{q_u}{{({\mathrm{\&beta;}}_u-2)}^2-a_u-\frac{q_u^2}{{({\mathrm{\&beta;}}_u-4)}^2-a_u-\frac{q_u^2}{{({\mathrm{\&beta;}}_u-6)}^2-a_u-....}}}$ Equation 4

A stable representation of the RIT is shown in FIG. 9 .

As can be seen from the foregoing equations, by applying an RF voltage of a predetermined frequency to the RF electrodes and a DC voltage to the electrodes, ions are trapped over a mass range that also depends on the size of the ion trap. Trapped ions can be isolated, ejected, mass analyzed and monitored. Ion separation is accomplished by applying RF/DC voltages to xy electrode pairs. The RF amplitude determines the center mass of the separation window, while the ratio of RF to DC amplitude determines the separation window width. Another method of isolating ions is to trap ions over a broad mass range by applying appropriate RF and DC voltages, then applying a broadband waveform containing the long-term frequencies of all ions except those to be isolated. The waveform is applied between two opposing (typically x or y) electrodes for a predetermined period of time. Ions of interest are unaffected while other ions are ejected. The long-term frequency for any ion of any given m/z value can be determined from Equation 3 and can be varied by varying the RF amplitude. Trapped ions can be excited by applying an AC signal having the same frequency as the long-term frequency of the particular ion to be excited between two opposing RF electrodes. Ions with this long-term frequency are excited in the trap and will either fragment or escape the trapping field. A similar process can be carried out by applying an AC signal to the terminal electrodes. A DC voltage pulse can be applied between any two opposing electrodes, and a wide mass range of trapped ions can be ejected from the RIT.

Quality analysis in several modes can be done using RIT as described below:

a) Scanless ion monitoring

Using the simplest structure shown in Figure 1, single or multiple ion monitoring can be achieved by completing ion separation and RF amplitude adjustment. Separation of ions of interest can be achieved by using RF/DC (mass selective stability) or the waveform method described above.

i) For single ion monitoring, isolate the ions of interest and then allow the ions to drift out of the RIT in the z direction by lowering the DC trapping field or they can be pulsed out or AC excited for detection.

ii) For multiple ion monitoring, several m/z values of ions are sequentially monitored using various examples of single ion monitoring described above.

iii) For MS ⁿ mass analysis, ions with m/z values of interest can be separated and excited by applying AC voltage and fragmentation at the CID. Generated ions can be mass analyzed with single or multiple ion monitoring.

b) scanning ions through the openings on the end electrodes

Mass instability scanning can be achieved using a RIT with the geometry shown in Figure 11.

i) Fig. 10b, apply an AC signal between the x (or y) electrodes and scan while doing the RF scan. Figure 10a, ions are mass-selectively ejected in the appropriate direction according to their m/z value (low to high). Figure 11, the opening in the end plate 16 is a slit 26 along the x-axis to allow ions oscillated by the AC signal to be efficiently ejected along the x-axis.

ii) Figure 12, double slits 27, 28 (crossed) on the end plates of the RIT allow AC to be applied both between either the x-electrodes or between the y-electrodes or between the x-electrodes and between the y-electrodes. By selecting the electrode pair (x or y) to which AC is applied, the orientation of the ion beam emerging from the RIT (along the x or y axis) is selected. This option is suitable when the shape of the exiting ion cloud needs to cooperate with the opening of the next device, eg another RIT. If AC voltages of different frequencies are applied to the x and y electrodes, ions of two different masses will be ejected from the slit seed.

c) Scanning ions through a slit on the RF electrode

i) Figure 13, by adding openings or slits 29 on the x (or y) electrodes and applying an AC voltage of a selected frequency between these two electrodes, ions can be mass-selectively passed through the slits by sweeping the RF amplitude shoot out. Typically, the amplitude of the AC voltage can also be swept for higher resolution.

ii) The RIT shown in Figure 14 has slits 29 and 31 on both the x and y electrodes. By selecting the electrode pair, x or y or both, to apply the AC signal, the direction of emission can be selected. Ions of different masses can emerge from each slit.

d) Scanning ions in any direction by electrodes

The RIT device shown in Figure 15 combines the features of the structures described above and allows ion implantation and mass selective or non-selective ejection along any x, y or z axis. This type of RIT can move ions in any x, y, or z direction by applying DC pulses or AC signals to the corresponding electrodes. The selection rules are as described above. An alternative geometry is shown in FIG. 16, which is cubic with symmetrical features on each electrode.

i) Figure 16, RF signals that are 120 degrees out of phase can be applied to each pair of electrodes in a cubic device to generate (rotate) a 3D RF trapping field.

ii) The RF trapping plane and DC trapping axis can be selectively changed by selecting the electrode pair to apply RF or DC. Shooting modes using AC and DC can be applied by adding an AC or DC signal to the corresponding electrodes. The device can act as a direction switch in ion transport operations.

iii) Selectable trapping mode: Any two pairs of electrodes can be electrically connected to the same RF signal to form a "cubic trap" similar to the one in a cylindrical ion trap, the other pair being grounded or applied 180 out of phase degrees of RF as a pair of end electrodes.

e) Multilateral combination of linear ion traps to construct a variety of devices

i) Figure 17 shows a typical serial arrangement of RITs. This arrangement uses two RITs, part II and part IV, and RF trapping parts I and III and an end plate 31 and an end plate 32 with a slit 33 through which ions are introduced. The DC trapping voltages 34 and 36 applied to the electrodes are schematically shown. In Mode I, the DC potential well is established in such a way that ions can be trapped in both Part II and Part IV. In mode II, ions in part II are allowed to transfer into part IV. Part III is used to minimize interference between parts II and IV, where different operations are performed on ions. For example, ions can be accumulated (mass-selectively or non-selectively) in section II while various operations such as partitioning, CID, ion/ion or ion-molecule reactions, and mass-selective ejection can be performed in section IV.

ii) Figure 18 shows RITs of the same size arranged in a tandem structure as a tandem mass spectrometer with characteristics similar to a triple quadrupole mass spectrometer. Ions were transferred from one RIT to the next by varying the DC potential in the same manner as shown in Figure 17.

iii) Figure 19a-e shows several modes of operation of the three RITs 41, 42 and 43 for ion/ion reactions. Use short RIT46, 47 instead of end plate lens for ion transfer to improve ion transfer efficiency. Figure 19a shows ions injected into the RITs 41, 42 and 43 from external ion sources A, B and C respectively, Figure 19a, ions injected from the ion source and trapped by applying DC to the end plate 44, short RF sections 46, 47 voltage and apply RF voltage to RITs 41, 42 and 43 to accumulate ions in each. Figure 19b, by varying the DC trapping voltage as shown, ions trapped in RIT 41 are transferred to RIT 42 where they can react. Figure 19c shows the DC voltage used to transfer accumulated ions from RIT 41, 43 to RIT 42. Figures 19d and 19e show the DC voltages used to transfer ions from RIT42 to RIT41 and from RIT42 to RIT43, respectively. It can be noted that these modes of operation have distinctly different characteristics from those of conventional series structures such as triple quadrupoles. Ions can be introduced at any stage in the structure; ions trapped in any stage can be separated or excited to generate fragments; ions trapped in any stage can be separated in two directions (forward and backward). ) to other ions and react with other ions or neutral particles.

iv) Figure 20, operating three RITs of different sizes with a single RF signal of fixed amplitude. Two sets of waveforms, one for ion separation and one for ion excitation, are applied to all x or y electrodes at different times to accomplish the desired operation. The size of the first RIT is chosen based on the desired q value for separating precursor ions. The equation used to calculate the size is:

Equation 5

where x ₀ (y ₀ ) is half the distance between the x(y) electrodes.

Waveform I for ion separation is also calculated based on this q value. After the ions are injected into the RIT 51 and cooled, waveform I is applied to separate the precursor ions with the desired m/z values; the DC potential along the beam axis is adjusted to transfer the precursor ions to the second RIT 52. The size of the RIT 52 is selected based on the m/z value of the precursor ion and the desired q-value for CID or ion/molecule reactions, and the waveform II for CID is also calculated based on this q-value. Interrupting the precursor ions by applying waveform II or reacting the precursor ions with molecules or other ions to generate generated ions; the generated ions are transferred to RIT53 when the DC potential is adjusted. The size of the third RIT53 is calculated based on the m/z of the generated ions to be separated and monitored. The q value for separation can be the same as for RIT51 so that the same waveform can be used for separation in RIT53; the size of RIT53 is calculated based on the q value and the m/z values of the ions to be separated/monitored. Separator ions are emitted for external detection. This type of tandem arrangement provides for analytical processing using RIT's such as MS ⁿ without the need for sophisticated electronics to sweep the RF voltage. Separation can also be achieved in RIT I and III using RF/DC separation at appropriate q values.

v) Because of their rectangular shape and ability to eject ions in x and y as well as z directions, there can be series arrays as well as parallel arrays and combinations of series and parallel arrays. Figure 21 shows that ions are injected into all RITs of a parallel array in the z direction from a single sample, cooled and then mass analyzed. The total number of ions that are trapped and detected is proportional to the number of RITs and the sensitivity of the multichannel RIT array cluster. Ions from different samples can be injected into different RITs and each RIT can be used as an independent mass analyzer. A separate detector, not shown, can be used for each channel, or an image detector processing the spatially resolved signal can be used to detect the emitted ions. The ionization and mass analysis of analytes in multiple samples can be performed simultaneously to achieve high-throughput analysis of a large number of samples. Highly selective analysis can also be accomplished using the same parallel array by allowing ions to pass through multiple selection processes in the gas phase before final mass analysis and detection. As shown in Figure 22, ions injected into RIT1 can be mass-selectively separated, transferred to RIT2 for ion/ion reactions through the slits on the electrodes, and then transferred through the slits on the electrodes into the RIT3 for ion/ion reactions and then mass analyzed by ejecting through a slit in the electrode. Obviously, the device could have more channels to allow more processing in high selectivity mode and stronger signal in high selectivity mode and to be able to analyze more samples simultaneously in high throughput mode. Figure 23 shows the combination of parallel arrays connected in series.

The ability to collectively transfer ions to adjacent traps in either the x or y direction allows ions of a given mass/charge ratio to be placed anywhere within the three-dimensional ion trap array. The ability to fix chemically specific kinds of spatial positions allows for a variety of potential applications including (i) transfer of ions to adjacent surfaces via ion/surface reactions and ion soft landings; (ii) ion annihilation assays, where at electrode voltage Reduction to allow storage of oppositely charged ions in adjacent elements before reaction mixing (iii) High density information storage consisting of three spatial dimensions and one mass/charge dimension.

vi) As shown in Figure 24, when DC pulses are used to transfer ions from one RIT to another, ions ejected from the first RIT can only enter the second RIT between certain narrow RF phase windows. Ions leaving the exit slit of the first RIT at the same time may not reach the entrance slit of the second RIT at the same time due to the difference in collision cross section for collision with He. By careful selection of either the injection RF phase, the distance between the RITs, or the pressure of He, ions with different cross-interfaces will be spatially separated due to different ion mobilities, some of them can be in the second RIT trap while others may not. By comparing the ions in the first RIT with the ions trapped in the first RIT, the cross-section of the ions can be estimated.

vii) As in the case of series RITs, parallel or different sized RITs can be operated with one RF signal of fixed amplitude. The size of the RITs can be calculated using Equation 1 so that the ions to be monitored operate at the same q value for ion separation in each RIT. As shown in Figure 25, a single waveform with gaps is applied to all RITs at the same q value, while ions with corresponding m/z values or ranges of m/z values are separated and trapped in each RIT. Trapped ions are later ejected in x/y or z directions for detection. An alternative ion separation method is the RF/DC method. Figure 26 shows an alternative arrangement for parallel arrays. Instead of moving ions along the z-axis, ions are transferred along the y-axis and sequentially through the steps shown in the tandem array of FIG. 20 .

Another way to construct an array of RITs is to use cubic ion traps as junctions between RITs (Fig. 27). Ions from one RIT can be transferred into the cubic trap, stored and then transferred to the next RIT. With the same structure, ions injected into the cubic trap can be transferred in any of six directions by applying a DC pulse or an AC waveform. RITs of different sizes can be connected using cubic wells to form a variety of arrays.

The foregoing are merely examples of how to use and combine RITs for ion analysis and processing. The plate structure facilitates and simplifies the manufacture of the ion trap. The simplest rectangular structure of ion traps allows multilateral combinations of rectilinear ion traps.

Claims (25)

1. rectilinear ion trap mass analyzer comprises:

Be arranged on zx and the zy plane x at interval and y to plane electrode to limit a trapping volume;

The RF voltage source, it is used for applying RF voltage to produce RF trapping field on the xy plane between x and y are to electrode;

The termination electrode of the end in the trapping volume that limits by described x and y electrode pair

The dc voltage source, its be used on described at least termination electrode, applying dc voltage with provide along the z axle DC trapping field thus ion be trapped in this trapping volume; And

The AC voltage source, it is used for applying AC voltage with excited ion in corresponding zx or zy plane to the x at least one pair of described interval or y electrode.

2. rectilinear ion trap as claimed in claim 1, wherein termination electrode comprises the plate that is arranged in the xy plane.

3. rectilinear ion trap as claimed in claim 1, wherein termination electrode comprises the end RF electrode pair on the plane that is arranged on the interval in zx and the zy plane.

4. rectilinear ion trap as claimed in claim 3 comprises the end plate that is arranged in the xy plane at the end of the end RF electrode pair on the plane at described interval.

5. as claim 2 or 4 described rectilinear ion traps, wherein at least one described termination electrode be included in the identical direction that applies AC voltage on the slit that is orientated penetrate with the ion that improves on the z direction thus.

6. as claim 2 or 4 described rectilinear ion traps, wherein at least one described end plate is included in the slit that is orientated on x and the y direction.

7. rectilinear ion trap as claimed in claim 1, wherein the x that applied of AC voltage or y are included in the slit that is orientated on the z direction or the opening of elongation to one in the plate at least.

8. rectilinear ion trap as claimed in claim 5, wherein one of x and y battery lead plate comprise the opening of slit or elongation at least.

9. rectilinear ion trap as claimed in claim 2, wherein x and y electrode and termination electrode limit a cube trapping volume, and all plates comprise the slit of intersection or the opening of elongation.

One kind the multistage ion processing system comprise:

Several rectilinear ion traps, each comprises:

Be arranged on zx and the zy plane x at interval and y to plane electrode to limit a trapping volume;

The RF voltage source, it is used for applying RF voltage to produce RF trapping field on the xy plane between x and y are to electrode;

The termination electrode of the end in the trapping volume that limits by described x and y electrode pair

The dc voltage source, its be used on described at least termination electrode, applying dc voltage with provide along the z axle DC trapping field thus ion be trapped in this trapping volume; And

The AC voltage source, it is used for applying AC voltage with excited ion in corresponding zx or zy plane to the x at least one pair of described interval or y electrode.Can to termination electrode apply AC voltage with the zx that intercouples at corresponding described rectilinear ion trap or zy plane on excited ion, ion can shift between ion trap thus.

11. multistage as claimed in claim 10 the ion processing system, comprise at least three rectilinear ion traps.

12. multistage as claimed in claim 11 the ion processing system, wherein termination electrode comprises the end plate with at least one slit, and rectilinear ion trap is an arranged in series, ion shifts between ion trap on the z direction thus.

13. multistage as claimed in claim 11 the ion processing system, one that wherein is arranged at least in the plane electrode on zx and the zy direction is included in the slit that is orientated on the z direction, and rectilinear ion trap is for being arranged in parallel, and ion shifts between ion trap on x or y direction thus.

14. multistage as claimed in claim 11 the ion processing system, wherein said several rectilinear ion traps are made up with series connection and parallel connected array.

15. multistage as claimed in claim 11 the ion processing system, wherein said rectilinear ion trap is arranged as their axle quadrature arrangement, and trap intercouples by rectilinear ion trap, ion can shift on x, y and z direction thus.

16. multistage as claimed in claim 15 the ion processing system, what wherein make the rectilinear ion trap coupling is cubic ion trap.

17. multistage as claimed in claim 12 the ion processing system, wherein the RF electrode of trap has different spacings.

18. multistage as claimed in claim 13 the ion processing system, wherein the RF electrode of trap has different spacings.

19. operational rights requires 1 described ion trap to resemble the RF electrode and apply RF/DC and separate voltage with trapping ion interested to separate the method for ion interested, to comprise.

20. method as claimed in claim 19 applies AC voltage to interrupt ion to a pair of RF electrode after being included in isolated ions.

21. operational rights requires 1 described ion trap to separate the method for ion interested, comprise to a pair of RF electrode apply one in frequency spectrum gapped broadband AC voltage, resonated outside the trap except having the ion of the stimulating frequency at gap frequency place other ions thus.

22. operational rights requires the method for 5 described ion traps, comprises to applying AC voltage at the RF of slit direction electrode pair.

23. operational rights requires the method for 7 described ion traps, comprises to the RF electrode applying RF trapping voltage and applying AC voltage to this group RF electrode that comprises slit.

24. operational rights requires the method for 7 described ion traps, comprises to one group of RF electrode applying RF voltage and applying the AC voltage of different frequency to penetrate the ion of different quality in the x and y direction to another group RF electrode.

25. operational rights requires the method for 9 described ion traps, comprises that the combination that is applied to RF, the AC of electrode pair and DC waveform by change selects the direction of motion of trapped ions.

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