Method for averaging and ion accumulation

Abstract

A method of operating an analytical instrument to analyze ions is provided. The analytical instrument includes an ion storage device. The method includes determining a target accumulation time and determining whether the target accumulation time is greater than a threshold accumulation time. When the target accumulation time is determined to be less than the threshold accumulation time, the method includes accumulating ions in the ion storage device for the target accumulation time and injecting the accumulated ions in a pulsed manner for analysis. When the target accumulation time is determined to be greater than the threshold accumulation time, the method includes defining a plurality of shorter accumulation times, each shorter accumulation time being less than the target accumulation time, determining the shorter accumulation times based on the target accumulation time and the threshold accumulation time, and, for each shorter ion accumulation time in turn: accumulating ions in the ion storage device for the shorter ion accumulation time and injecting the ions accumulated for the shorter ion accumulation time in a pulsed manner for analysis; and analyzing the / injected ions.

Description

Technical Field

[0001] This disclosure relates to the field of mass spectrometry, and in particular to a mass spectrometry method for accumulating ions in an ion trap. Background Technology

[0002] Many mass analyzers operate in a pulsed manner, accumulating ions from a continuous ion source before analysis. Due to this ion concentration, such analyzers are particularly susceptible to space charge effects, where the mutual repulsion between a large number of ions begins to overwhelm the directional force applied by the mass analyzer. The space charge effect can affect the dynamic range of the mass analyzer.

[0003] The accumulation time required to obtain a useful mass spectrum varies greatly depending on the ions being analyzed. Too short an accumulation time leads to insufficient collection and wasted mass spectra. On the other hand, too long an accumulation time may cause saturation effects and / or exceed the analyzer's repetition cycle, resulting in a reduced rate of different analytes that can be studied.

[0004] Mass analyzers with accumulation traps typically use automatic gain control (AGC) to determine the ion current or number of ions in the pre-scan and then determine the appropriate accumulation time. Some mass analyzers may use predictive AGC, where a full mass scan over a wider mass range is used to determine the accumulation time for the ion fragmentation scan.

[0005] Current mass analyzers without accumulation traps (such as orthogonal time-of-flight instruments) can achieve very high repetition rates, change the measurement time for different numbers of ions, and potentially perform repeated scans and dynamically control the time and number of averaging operations.

[0006] Ion trap time-of-flight (IT-ToF) mass analyzers accumulate ions in an ion trap and eject them in the form of pulsed ion packets for mass analysis. The ion trap can accumulate ions within a controlled accumulation time, depending on the accumulation time required for the useful mass spectrometry of a particular precursor ion. The accumulation time for low-intensity precursor ions may be significantly longer than the repetition cycle of an IT-ToF mass analyzer. This means that when the accumulation time exceeds the time required for ion fragmentation scanning, the analyzer needs to be shut down between subsequent analyses.

[0007] Therefore, there is still a need for an improved method for controlling a quality analyzer with an accumulation trap, which can provide improved efficiency and improved dynamic range. Summary of the Invention

[0008] In summary, a method for operating an analytical instrument for analyzing ions is provided, wherein the analytical instrument includes an ion storage device. The method includes: determining a target accumulation time (i.e., a desired accumulation time); determining whether the target accumulation time is greater than a threshold accumulation time; when the target accumulation time is determined to be shorter than the threshold accumulation time: accumulating ions in the ion storage device within the target accumulation time; injecting the accumulated ions in a pulsed manner for analysis; when the target accumulation time is determined to be greater than the threshold accumulation time: defining a plurality of shorter accumulation times, each shorter than the target accumulation time, determining the shorter accumulation time based on the target accumulation time and the threshold accumulation time; and sequentially for each shorter ion accumulation time: accumulating ions in the ion storage device within the shorter ion accumulation time, and injecting the accumulated ions in a pulsed manner within the shorter ion accumulation time for analysis; and analyzing said / each injection pulse.

[0009] Advantageously, this approach can provide improved efficiency and improved dynamic range.

[0010] The instrument includes a downstream mass analyzer downstream of the ion storage device, and the step of analyzing the / each injection pulse includes analyzing the / each pulse using the downstream mass analyzer. This method is advantageously applicable to analyses performed using a mass analyzer, such as a time-of-flight mass analyzer or a multiple-reflection time-of-flight mass analyzer.

[0011] The ion storage device may include an ion extraction trap. In some embodiments, the step of pulsed injection of accumulated ions may include pulsed extraction of accumulated ions from the extraction trap.

[0012] Optionally, the ion storage device may also include other ion storage devices for ion accumulation. For example, these other ion storage devices may be located upstream of the extraction trap.

[0013] Optionally, ions are accumulated in the ion storage device / extraction trap during the analysis steps of each injection pulse. This can improve the time efficiency of the analytical instrument.

[0014] To improve efficiency and dynamic range, the threshold accumulation time can be determined based on a number of parameters, including those listed below.

[0015] Optionally, the threshold accumulation time is based at least in part on the time required to perform a single analysis of the pulse using a downstream quality analyzer.

[0016] The method may include separating sample molecules in a liquid chromatograph, in which the threshold accumulation time may be at least partially based on the resolution of the liquid chromatograph.

[0017] The analytical instrument may include an ion source upstream of an ion storage device / extraction trap and one or more ion optical devices disposed between the ion source and the ion storage device / extraction trap, wherein the threshold accumulation time is at least partially based on the additional time ions spend passing through one or more ion optical devices.

[0018] Threshold accumulation time can be based at least in part on the space charge limitation of the ion storage device / extraction trap and / or the space charge limitation of the downstream mass analyzer.

[0019] Analyzing each injection pulse can produce results, namely mass spectrometry data, such as mass spectrometry. When it is determined that the target cumulative time is greater than a threshold cumulative time, the method may include averaging, summing, or weighting the results of analyzing each injection pulse.

[0020] The method may optionally include limiting the number of short accumulation times based on a predetermined maximum quantity. The supply of certain precursor ions may be very low (i.e., only trace levels) and may become a dominant factor affecting the time required to operate the analytical instrument.

[0021] Multiple shorter cumulative times can be equal or unequal. Therefore, the cumulative time can be determined flexibly.

[0022] The analysis of the injected pulses can be performed using one or more parameters of the instrument, which may include, for example, fragmentation energy (e.g., collision energy during collision-induced dissociation (CID), amplitude and / or frequency of the applied RF voltage (e.g., capture voltage applied to the ion storage device), gain of the ion detector of the mass analyzer, etc. Optionally, when a target accumulation time is determined to be greater than a threshold accumulation time, the method includes modifying one or more parameters between the injected pulses, i.e., analyzing each injected pulse using one or more different parameters. This allows for adjustment of the analytical parameters or the use of a range of different analytical parameters. For example, different collision energies allow for different fragmentation characteristics at the cost of time, thus additional scans can provide richer characterization. Similarly, changing the RF amplitude and / or frequency applied to the ion storage device can enhance the achievable mass range across multiple scans, while changing the detector gain can expand the dynamic range.

[0023] In some embodiments, the ion extraction trap is a radio frequency voltage ion extraction trap, which includes electrodes for extracting ions from the ion extraction trap by applying a direct current (DC) voltage. This method is particularly suitable for analytical instruments with such ion extraction traps because it can reduce or avoid space charge effects that may occur in such ion extraction traps.

[0024] The target accumulation time can be determined by analyzing an ion sample, for example, where the ion sample represents ions that will be analyzed by a downstream mass analyzer. The ion sample can be analyzed using a mass analyzer or some other ion analyzer, such as an electrometer.

[0025] If a mass analyzer is used, the mass analyzer used to analyze the ion sample to determine the target accumulation time can be a downstream mass analyzer or a second mass analyzer (a component different from the downstream mass analyzer). The second mass analyzer may optionally be an electrostatic orbit trap mass analyzer, such as an Orbitrap. TM Quality analyzer. Attached Figure Description

[0026] To better understand this disclosure and to illustrate how it may be implemented, reference will now be made to the accompanying drawings by way of example only, in which:

[0027] Figure 1 A schematic arrangement of a mass spectrometer suitable for performing the methods according to embodiments of the present disclosure is shown;

[0028] Figure 2 Three figures are shown illustrating problems that may arise from overfilling of ion traps in the prior art;

[0029] Figure 3 The operation is shown Figure 1 Known methods for mass spectrometry;

[0030] Figure 4 A method for operating a mass spectrometer according to this disclosure is shown;

[0031] Figure 5 A method for operating a mass spectrometer according to this disclosure is shown;

[0032] Figure 6 A method for operating a mass spectrometer according to this disclosure is shown;

[0033] Figure 7 A schematic arrangement of a mass spectrometer suitable for performing the methods according to embodiments of the present disclosure is shown;

[0034] Figure 8 A method for operating a mass spectrometer according to this disclosure is shown. Detailed Implementation

[0035] Figure 1 A schematic arrangement of a mass spectrometer that can be operated according to embodiments of the present disclosure is shown; it should be understood that the instrument shown in FIG1 is a non-limiting example and may have various variations.

[0036] Figure 1The instrument includes an ion source 15, an ion transfer stage 100, an initial mass analyzer 110, an extraction trap 151, and a downstream mass analyzer 150.

[0037] Ion source 15 is configured to generate ions from the sample. Ion source 15 can be a continuous or pulsed ion source, such as an electrospray ionization (ESI) ion source, a MALDI ion source, an atmospheric pressure ionization (API) ion source, a plasma ion source, an electron ionization ion source, a chemical ionization ion source, etc. More than one ion source can be provided and used. Ions can be, for example, small and large organic molecules, biomolecules, DNA, RNA, proteins, peptides, fragments thereof, etc.

[0038] Ion source 15 can be coupled to a separation device, such as a liquid chromatography separation device or a capillary electrophoresis separation device (not shown), so that the sample ionized in ion source 15 comes from the separation device.

[0039] Ion transfer stage 100 may be located downstream of ion source 15 and upstream of extraction trap 151. Ion transfer stage 100 may include capillary 20, ion funnel 30, calibrator source 40, quadrupole pre-filter 50, ion director 60, quadrupole mass filter 70, charge detector 75, curved linear ion trap (C trap) 80, collision cell 90, and multipolar ion director 95. Ion director 60 may be the design described in U.S. Patent No. 9,536,722.

[0040] Ions from the ion source can be accumulated in the C trap 80 and / or the collision cell 90 by opening and closing the ion gate 74 located within the charge detector 75. The charge detector 75 may be located between the quadrupole mass filter 70 and the C trap 80.

[0041] Optionally, the initial mass analyzer 110 is an electrostatic orbital trap mass analyzer. An example of such a mass analyzer is the Orbitrap® mass analyzer sold by Thermo Fisher Scientific, Inc. Figure 1 As shown, the initial mass analyzer 110 may include an internal electrode 111 extending along the axis of the orbital trap and a pair of separate external electrodes 112, 113. The pair of external electrodes surrounds the internal electrode 111 and defines a trap volume therebetween in which ions are trapped and oscillated by orbiting around the internal electrode 111, applying a trapping voltage to the internal electrode while oscillating back and forth along the axis of the trap. The pair of external electrodes 112, 113 serve as detection electrodes to detect the mirror current caused by the oscillation of ions in the trap volume, thereby providing a detection signal.

[0042] External electrodes 112 and 113 are typically used as a differential detection electrode pair and are coupled to a differential amplifier (not in...). Figure 1 The differential amplifier (shown in the diagram) then forms part of a digital data acquisition system to receive the detected signal. The detected signal can be processed using Fourier transform to obtain a first mass spectrum of the ions within the initial mass analyzer 110.

[0043] Once ions have accumulated in the ion trap 80 and / or collision cell 90, they can be injected into the initial mass analyzer 110. For this purpose, ions can be ejected from the trap 80 in a direction perpendicular to the trap's axis (orthogonal ejection), for example, by applying one or more suitable DC voltages to the ion trap 80. Ions can then be injected into the mass analyzer 110 via one or more lenses and deflection electrodes.

[0044] Optionally, the downstream mass analyzer 150 is an ion trap time-of-flight (IT-ToF) mass analyzer. An example of such a mass analyzer is the Astral® mass analyzer sold by Thermo Fisher Scientific, Inc. The IT-ToF mass analyzer can be a multiple reflection time-of-flight mass analyzer (mr-ToF) as described in U.S. Patent No. 9,136,101. The mr-ToF mass analyzer 150 is constructed around two opposing ion mirrors 153 extending along the drift direction D. The mirrors are opposite each other in a direction perpendicular to the drift direction. An extraction trap 151 injects ions into the first mirror of the two mirrors 153, and the ions then oscillate between the two mirrors 153. The ejection angle of the ions from the extraction trap 151 and an additional deflector 154 allows control of the ion energy in the drift direction, causing the ions to move along the length of the two mirrors 153 during oscillation, thus producing a Z-shaped trajectory. The two mirrors 153 are tilted relative to each other, creating a potential gradient that slows the drift velocity of the ions and causes them to be reflected back along the drift dimension and focused onto the detector 157. The tilting of the mirrors generally has the negative side effect of altering the ion oscillation period as the ions travel along the drift dimension. However, this can be corrected using a strip electrode 155 (as a compensation electrode) that alters the flight potential of the portion of the inter-mirror space that varies along the length of the two opposing mirrors 153. By combining the varying width of the strip electrode 155 with the varying distance between the two mirrors 153, reflection and spatial focusing of ions towards the detector 157 are achieved while maintaining good temporal focusing performance.

[0045] The downstream quality analyzer 150 is configured to operate at a repetition period T. R Operation. During each repetition cycle, the mass analyzer performs mass analysis on the ion packets while simultaneously accumulating new ion packets in extraction trap 151. The repetition cycle T of the downstream mass analyzer 150 is...R This can be primarily defined by the time it takes for the ion pack to accumulate in extraction trap 151 and be injected into the mass analyzer. Additionally, it may be necessary to operate extraction trap 151 in non-accumulation mode for a minimum amount of time within each repetition cycle (e.g., to allow time to process accumulated ions, etc.). Of course, the repetition cycle should also be long enough to allow for mass analysis of each ion pack (i.e., to allow the ions to pass through the mass analyzer, reach detector 157, and be subjected to mass spectrometry analysis of the data), but the time required for mass analysis of the ion pack is typically shorter than the time required for its accumulation.

[0046] In some implementations, the downstream analyzer 150 has a repetition period of 5 ms or less. The repetition period is the reciprocal of the repetition rate, which is the number of mass spectra acquired by the downstream analyzer 150 per second. In some implementations, the downstream analyzer 150 has a repetition rate of 200 Hz or higher.

[0047] Extraction trap 151 may be an ion processor as described in U.S. Patent No. 9,548,195. Extraction trap 151 is provided to form an ion bag before ion implantation into ToF mass analyzer 150. Extraction trap 151 accumulates ions over a accumulation time, allowing the continuous ion beam from the ion source to be converted into a concentrated ion bag. The accumulation time may be controlled by an ion gate 74, which may be located in charge detector assembly 75. After the accumulation time ends, the accumulated ion bag is pulsed from extraction trap 151 into ToF mass analyzer 150. The pulse may occur very quickly, much shorter than the accumulation time.

[0048] Extraction trap 151 may contain a buffer gas and incorporate two trapping regions: a first region under a first pressure for rapid ion cooling and a second region under a second pressure for ion extraction. The first pressure is higher than the second pressure. Ions are cooled in the first high-pressure region and then transferred to the second low-pressure region, where they are pulsed into the ToF analyzer. Pulsed injection may involve applying a DC voltage to extraction trap 151.

[0049] Figure 3 illustrates a method for sample analysis using instruments such as those shown in Figure 1. The method may involve first performing an MS1 ​​scan (e.g., a full mass scan) in an initial mass analyzer 110, followed by an MS2 scan in a downstream mass analyzer 150. The MS1 scan provides measurements (i.e., MS1 spectra) of ions provided by the ion source 15 (optionally filtered by mass-to-charge ratio (m / z)).

[0050] During the MS2 scan, the instrument filters ions supplied by ion source 15 to provide a series of precursor ions filtered by mass-to-charge ratio (m / z). The filtered precursor ions are then fragmented, and the resulting fragmented ions are analyzed in a downstream mass analyzer 150 to provide the ion measurement results (i.e., the MS2 spectrum).

[0051] In step 202, the ions are passed through different ion transfer stages 100, such as... Figure 1 Those included in the process. These include mass filters, such as quadrupole pre-filter 50 and quadrupole filter 70. Ions are passed through the mass filters and filtered according to their mass-to-charge ratio (m / z) (step 204). When MS1 ​​scan is completed, the range of ion masses allowed to pass through quadrupole filter 70 is typically wider than that during MS2 scan.

[0052] Upon completion of the MS1 scan, ions are accumulated and cooled in C trap 80 in step 212, and then vertically injected into an electrostatic orbital trap or orbitrap in step 214. TM The analysis is performed in quality analyzer 110. (Orbitrap) TM A scan of the quality analyzer MS1 may take hundreds of milliseconds, for example, about 250 milliseconds.

[0053] Upon completion of the MS2 scan, in step 222, ions pass through C trap 80, then through multipolar ion guide 95, and enter extraction trap 151, where they accumulate. In step 224, ions are broken down in the high-pressure region of extraction trap 151. The accumulation time of ions in extraction trap 151 is determined by an ion gate 75 upstream of the trap, which may be located within charge detector 74 between quadrupole filter 70 and C trap 80. In step 226, the accumulated ions are pulsed from extraction trap 151 into ToF mass analyzer 150 by applying an extraction voltage to the electrodes of extraction trap 151. The ion pack is then analyzed in downstream analyzer 150 in step 228.

[0054] Figure 4 A method combining AGC and dynamic averaging according to this disclosure is illustrated. As shown in Figure 4, an initial scan (e.g., an MS1 ​​scan or a full mass scan) is performed, through which ion flow information of AGC can be obtained in step 400. Optionally, the initial scan is performed using an initial mass analyzer 110.

[0055] In data-dependent acquisition, the initial scan can be used to provide measurement information for the precursor ions. For example, the initial scan can provide a list of precursor ions. The precursor ion to be analyzed can be selected from the list (step 402). Using the information from the initial scan, the ion current of the precursor ion can be calculated (step 404). Based on this, the required accumulation time T can be calculated. D And based on the required cumulative time T D Determine whether to take the average and how many can be determined (step 406).

[0056] Then an MS2 scan is performed (step 408) to generate a fragment mass spectrum, and it is possible to check if there are any remaining precursor ions to be analyzed. At this point, the next precursor ion in the list is selected and an MS2 scan is performed on that precursor ion, or the instrument moves to the next MS1 scan (step 410). Optionally, each MS2 scan 408 is performed by the downstream mass analyzer 150.

[0057] Figure 5 A method for dynamically determining whether an average value should be taken in the quality analyzer is illustrated according to an embodiment of this disclosure. For example... Figure 5 As shown, the required cumulative time T D Accumulation time T of ion trap threshold T Compare (step 300) and determine the required cumulative time T. D Is the cumulative time greater than the threshold T? T .

[0058] The threshold accumulation time can be based on a variety of factors, including but not limited to any combination of the following: the repetition period T of the downstream quality analyzer 150. R Time cost T O Or the space charge capacity limit of extraction trap 151 (and / or mass analyzer 150).

[0059] The space charge capacity limit of extraction trap 151 is the limit to the extent to which extraction trap 151 can be filled before the linear relationship between ion number and filling time is broken. Exceeding the space charge capacity may also negatively affect the resolution of the resulting mass spectrum, and increase the mass transfer of high m / z ions. These effects are illustrated in Figure 2.

[0060] To avoid increasing the repetition rate, the time cost T O It can be used to determine the threshold accumulation time T T .

[0061] Time cost T OThis is the time required between filling and emptying the extraction trap 151, for example, because it is necessary to allow ions to travel from the ion source 15 through the ion transfer stage 100 to the extraction trap 151 in order to process accumulated ions, etc.

[0062] In some embodiments, pre-accumulation can actually be used to reduce time overhead T. O During the time that extraction trap 151 cannot be directly filled, ions for the next analysis accumulate in one of the ion transfer stages 100 upstream of extraction trap 151. In embodiments where the results of one scan affect the parameters of the next scan, the necessary computation time may result in a time overhead T. O .

[0063] If used for separating sample molecules, the threshold accumulation time T T It can also be based on the peak width of ions in liquid chromatography, or even the opposite.

[0064] In some implementations, a narrower peak width in liquid chromatography corresponds to a higher intensity peak, thus requiring a shorter injection time, while a wider peak width corresponds to a lower intensity peak, thus requiring a longer injection time. For example, for a narrower peak width, the threshold accumulation time T... T It may decrease; conversely, for a wider peak width, the threshold accumulation time T... T It may increase. Alternatively, the number of shorter accumulation times can be limited based on peak width. For example, a larger peak width limits the number of shorter accumulation times (because more scans are required). A smaller peak width limits the number of shorter accumulation times (because more scans are required).

[0065] Required cumulative time T D The required accumulation time T can be determined based on automatic gain control (AGC) methods known to those skilled in the art. D The extraction trap is filled or will be filled with the number of ions required for complete analysis of the sample. Required cumulative time T D Ensure, or will ensure, that each ion pack has at least the required minimum number of ions, such that the resulting ion pack reaching detector 157 will represent the entire target mass range of the selected parent ion.

[0066] If the required cumulative time T D Less than or equal to the threshold cumulative time T T Then, the required accumulation time T for ions to accumulate in extraction trap 151. D (Step 302), then injected as a single pulse into the downstream mass analyzer 150 (Step 304) and analyzed to produce a mass spectrum (Step 306), without the need for further processing. Figure 3 The method needs to be modified.

[0067] If the required cumulative time T D Accumulation time T greater than the threshold T Then based on the threshold accumulation time T T The required accumulation time T D Divide into n shorter cumulative times, T1 to T N (Step 310). The n shorter times can be of the same duration or of different durations. If the durations of the n times are not equal, the resulting n mass spectra may have different gain levels. The number of n shorter times can be determined by adjusting the required accumulation time T. D Divide by the threshold accumulation time T T And rounded to the nearest integer. The duration of n shorter times can be determined by taking the required cumulative time T. D Determined by dividing by the number of shorter times n, or it may be equal to the threshold cumulative time T. T Or it could be a mixture of different durations selected through different methods. n shorter cumulative times T1 to T... N The sum of the durations may be greater than, less than or equal to the required cumulative time T. D .

[0068] Optionally, n shorter cumulative times T1 to T N The sum of the durations may be greater than the required cumulative time T. D Not exceeding 10%. Optionally, n shorter cumulative times T1 to T... N The sum of the durations may be less than the required cumulative time T. D No more than 10%.

[0069] n can be compared with the maximum value of n (step 312). The maximum value of n can be chosen such that the required accumulation time T may be very long. D The trace precursor ion does not affect the instrument time. Therefore, when n is greater than the maximum value, n can be set to the maximum value, or the instrument can skip the trace precursor ion and proceed to the next step (step 313).

[0070] During the first shorter accumulation time T1, ions accumulate in extraction trap 151 (step 314), and are then pulsed into the ToF analyzer (step 316). While the first ion packet is being analyzed in the ToF analyzer, the second ion packet accumulates in extraction trap 151 during the second shorter accumulation time T2 (step 315), and is then pulsed into the ToF analyzer (step 317), and so on, until n ion packets have accumulated and been pulsed and analyzed over n accumulation times (steps 318, 319).

[0071] The resulting n mass spectra are then processed into a single mass spectrum (step 320). This can be done by summing the n mass spectra or averaging the n mass spectra. This is relative to the original required accumulation time T. D Mass spectra acquired on individual ion packs that accumulate within the cell result in mass spectra with improved dynamic range.

[0072] The method may involve modifying one or more parameters of the instrument between any of the n injections. Modifiable parameters may include, for example, the collision energy and / or the ion trap RF amplitude.

[0073] In some implementations, the method may involve analyzing the first of the n ion packets before subsequent n-1 ion packets. This allows for checking for trap saturation effects and space charge peaks to identify the output before subsequent injections, thereby improving the quantification and confidence of the identified output. Optionally, if the instrument or scanning parameters change in the subsequent n-1 injections after the first injection, the first ion packet and the resulting mass spectrum may not be included in the total mass spectrum or average mass spectrum.

[0074] Figure 6 shows the total cumulative time T required. D The cumulative time is divided into n shorter cumulative times, where n is 3. In the example shown in Figure 6, the required cumulative time T D The threshold accumulation time is 3 ms, which is 9 ms. In the example in Figure 6, the n shorter times have the same length. By splitting the required accumulation time as shown in the figure, the total accumulation time is equal to or greater than the required accumulation time T. D However, it allows for more efficient use of analytical instruments and avoids trap overflow.

[0075] In this example, the method of dynamically determining whether to divide the cumulative time by the average is applied to the ion trap time-of-flight mass analyzer, but this method can also be applied to other mass analyzers, including but not limited to analytical ion traps and Fourier transform analyzers.

[0076] Although Figure 1 illustrates the use of ion extraction trap 151, in practice the method and apparatus can more generally be used in place of ion storage devices of any form, such as: ion trap (more general); ion accumulation device; ion trapping region; analytical ion trap; orthogonal accelerator; pyrolysis cell; reaction cell and / or collision cell, or any combination thereof.

[0077] In some implementations, ions may be accumulated in one or more ion storage devices upstream of the extraction trap (or equivalent) for injection into the analyzer.

[0078] In some embodiments, ions can be accumulated in both the extraction trap and an ion storage device upstream of the extraction trap, for example, by pre-accumulating ions in the upstream ion storage device, transferring the pre-accumulated ions from the upstream ion storage device to the extraction trap, and then accumulating additional ions in the extraction trap. In these embodiments, the accumulation time can correspond to the sum of the pre-accumulation time in the upstream ion storage device and the additional accumulation time in the extraction trap.

[0079] In some implementations, the ion storage device is a region of the ion scheduling device, such as a capture region (e.g., an accumulation region). In the ion scheduling device, various potentials allow different ions with different m / z ratios to accumulate at different locations within the device and to be released individually from the device according to their m / z ratios. For example, the ion scheduling device can continuously accumulate up to 10 precursor ions with different m / z ranges.

[0080] The ion sorting device 750 can be used to provide additional selectivity for mass analysis or to reduce ion loss due to mass separation prior to typical MS / MS analysis by providing a narrower mass range to the filter.

[0081] Figure 7 illustrates a schematic diagram of a mass spectrometer operable according to an embodiment of the present disclosure, wherein the method includes accumulating ions in an ion grading device 750. Except for including an ion grading device, this mass spectrometer is in all respects... Figure 1 The mass spectrometer is the same.

[0082] Within the mass spectrometer, the ion sorting device 750 may be located upstream of at least one ion transfer stage 100. The ion sorting device 750 may be located downstream of the ion source 15 and upstream of the mass analyzer 150. The ion sorting device 750 may be located upstream of any one or all of the quadrupole mass filter 70, charge detector 75, curved linear ion trap (C trap) 80, collision cell 90, and multipolar ion director 95. The ion sorting device 750 may be located downstream of any one or all of the capillary 20, ion funnel 30, calibration source 40, and quadrupole pre-filter 50. Within the mass spectrometer, the ion sorting device 750 may replace the ion director 60.

[0083] In the above embodiments of the invention, the method may involve performing an MS1 ​​scan (e.g., a full mass scan) followed by an MS2 scan of precursor ions with a narrow mass range or filtered by mass-to-charge ratio (m / z). In the method described with reference to Figures 4 and 5, each precursor ion in the list to be analyzed is sequentially scanned using MS2, and after each scan is completed, the next precursor ion in the list is analyzed until the precursor ions are depleted. In embodiments of the method, the ion storage device is a region of the ion scheduling device 750, selecting multiple precursor ions, for example, m precursor ions.

[0084] For each of the m precursor ions, the ion current in the precursor ion list can be calculated based on the information from the initial MS1 scan. For each of the m precursor ions, the required accumulation time T is determined. D For each of the m precursor ions, the required cumulative time T can be calculated based on the ion current of each of the m precursor ions. D Based on the required cumulative time T D For each of the m parent ions, determine whether to take the average value and how many can be determined.

[0085] The m precursor ions can be simultaneously accumulated in the accumulation region of the ion sorting device 750 for analysis by MS2 scan. The precursor ions are accumulated separately in the accumulation region of the ion sorting device 750 according to their mass-to-charge ratio range. The ion sorting device 750 can, for example, simultaneously accumulate up to 10 different precursor ions. Ion accumulation takes a certain accumulation time, which can be controlled by an ion gate upstream of the ion sorting device or by a gate via the quadrupole pre-filter 50.

[0086] After a cumulative time, the ion scheduling device 750 individually pulses the precursor ions to be analyzed in the MS2 scan. For example, precursor ions can be ejected sequentially according to the m / z ratio range of the precursor ions. For example, the ions of the first precursor ion are ejected and analyzed first, then the ions of the second precursor ion are ejected and analyzed, and so on, until the mth precursor ion is ejected and analyzed. The parent ion and all accumulated ions have been ejected from the ion scheduling device 750.

[0087] After ejection and before analysis, the precursor ions ejected from the ion sorting device undergo mass filtration and cleavage in the ion transfer stage 100.

[0088] Figure 8 It shows the applicability Figure 7 The method for dynamic averaging of ion accumulation in the mass spectrometer shown includes an ion scheduling device 750. As shown in Figure 8, m precursor ions accumulate simultaneously in the accumulation region of the ion scheduling device 750 during the accumulation time of the scheduler (step 800).

[0089] For ion storage devices, the scheduler accumulation time can be equal to the threshold accumulation time T. T In this embodiment, the ion storage device is the accumulation region of the ion scheduling device 750. Threshold accumulation time T T and each required cumulative time T for each parent ion D It can be determined according to the above content described in Figure 5.

[0090] The scheduler's cumulative time can be fixed.

[0091] The first precursor ion out of m precursor ions is pulsed from the ion scheduling device 750, passed through at least some ion transfer stages 100, and injected into a downstream mass analyzer, such as an MR-ToF analyzer 150 (step 802). The ion packet of the first precursor ion is analyzed in the MR-ToF analyzer 150, and a first spectrum of the first precursor ion is obtained (step 804). Then, the ion packet of the next precursor ion is ejected from the ion scheduling device 750 (step 806), and a first mass spectrum of the next precursor ion is obtained (step 814), until all m precursor ions accumulated in the ion scheduling device 750 have been ejected from the ion scheduling device, injected into the MR-ToF analyzer, and analyzed. The accumulation of all ions in the ion scheduling device and the subsequent ejection and analysis constitute a single ion scheduling cycle.

[0092] The ion scheduling cycle is repeated, and m precursor ions accumulate in the ion scheduling device 750 during the cumulative time of the scheduler, and are then ejected and analyzed individually.

[0093] Each precursor ion has a required accumulation time T.D This can be achieved after n ion scheduling cycles.

[0094] For ion scheduling devices, when the required accumulation time T of the precursor ions... D Less than or equal to the threshold cumulative time T T If n is 1, then the precursor ion is analyzed and a single mass spectrum is generated within a single ion scheduling cycle, and averaging or summing of the mass spectra is not required. The ions accumulate over the desired time T. D Internal accumulation, and if the scheduler's accumulation time is fixed and exceeds the required accumulation time T. D The accumulated time may be longer than the required accumulated time T. D Longer.

[0095] When the required accumulation time T of the precursor ion D Accumulated time T greater than the threshold T When n is greater than 1, the precursor ion is analyzed in multiple ion scheduling cycles. In this case, the precursor ion is analyzed n times in n ion scheduling cycles, and n mass spectra are processed into a single mass spectra.

[0096] When the required accumulation time T of the precursor ion D Accumulated time T greater than the threshold D Given multiple n shorter accumulation times, each shorter accumulation time is shorter than the required accumulation time T. D Based on the required cumulative time T D and threshold cumulative time T D Determine multiple shorter cumulative times. This includes determining the number n of shorter cumulative times and the duration n of each shorter cumulative time. The shorter cumulative time can be equal to the scheduler cumulative time, which can be equal to the threshold cumulative time.

[0097] The sum of the cumulative times of n schedulers may be greater than, less than or equal to the required cumulative time T. D .

[0098] Optionally, the sum of the durations of the n shorter accumulation times may be greater than the required accumulation time T. D The percentage should not exceed 10%. Optionally, the sum of the durations of the n shorter cumulative times may be less than the required cumulative time T. D No more than 10%.

[0099] n can be compared to its maximum value. The maximum value of n can be chosen such that the required accumulation time T may be very long. DThe trace precursor ion does not affect the instrument time. Therefore, when n is greater than the maximum value, n can be set to the maximum value, or the instrument can skip the trace precursor ion and proceed to the next step.

[0100] If, after n ion scheduling cycles, the required cumulative time T for a specific parent ion is satisfied... D For example, for the first precursor ion, the device can terminate the accumulation of the precursor ion (steps 810, 818). Then, the n mass spectra of each precursor ion are processed into a single mass spectrum (steps 812, 820). This can be done by summing the n mass spectra or averaging the n mass spectra. This is relative to the original required accumulation time T. D Mass spectra acquired on a single ion pack that has accumulated within the cell result in mass spectra with improved dynamic range.

[0101] In the next ion scheduling cycle, new precursor ions are accumulated to replace the terminated precursor ions (step 822). In this way, different precursor ions with different required accumulation times and different n values ​​can be accumulated and analyzed in the ion scheduling device.

[0102] Before step 822, it may be checked whether there are any remaining precursor ions to be analyzed. If there are any remaining precursor ions to be analyzed, they are accumulated in step 822 to replace any terminated precursor ions. If there are no remaining precursor ions to be analyzed, the instrument may proceed to the next MS1 scan.

[0103] The selection and / or order of the precursor ions to be analyzed can be determined and / or optimized by an algorithm that considers the m / z ratio of each precursor ion, and each simultaneously accumulated precursor ion must be fully separated according to the m / z ratio so that the ion scheduling device can fully separate the different precursor ions.

[0104] In data independence acquisition analysis, a set of preprogrammed precursor ions can be accumulated in the ion scheduling device, and the ion scheduling cycle can be repeated a fixed number of times before replacing all the precursor ion sets with a new set of preprogrammed precursor ions.

[0105] The method described in Figure 8 can be combined with the methods or method steps described with reference to Figures 3, 4 and / or 5.

[0106] Although Figure 1 depicts a specific type of initial quality analyzer 110 and downstream quality analyzer 150, only one quality analyzer is required, and other types of quality analyzers can be provided.

Claims

1. A method of operating an analytical instrument for analyzing ions, wherein the analytical instrument includes an ion storage device, the method comprising: Determine the target cumulative time; Determine whether the target cumulative time is greater than the threshold cumulative time; When the target cumulative time is determined to be less than the threshold cumulative time: Ions accumulate in the ion storage device within the target accumulation time. as well as Accumulated ions are injected in a pulsed manner for analysis; When the target cumulative time is determined to be greater than the threshold cumulative time: Multiple shorter cumulative times are defined, each shorter than the target cumulative time. The shorter cumulative time is determined based on the target cumulative time and the threshold cumulative time. as well as For each shorter ion's cumulative time: Ions are accumulated in an ion storage device within a short ion accumulation time, and the accumulated ions are injected in a pulse manner within the short ion accumulation time for analysis. as well as Each injected pulse is analyzed.

2. The method of claim 1, wherein the instrument includes a downstream mass analyzer downstream of the ion storage device, and the step of analyzing the / each implantation pulse includes analyzing the / each pulse using the downstream mass analyzer.

3. The method according to claim 2, wherein the downstream quality analyzer is a time-of-flight quality analyzer, such as a multiple reflection time-of-flight quality analyzer.

4. The method according to claim 2 or 3, wherein ions are accumulated in the ion storage device during the step of analyzing the / each injection pulse.

5. The method according to any one of claims 2 to 4, wherein the threshold accumulation time is at least partially based on the time required to perform a single analysis of the pulse using the downstream quality analyzer.

6. The method according to any one of the preceding claims, further comprising separating sample molecules in liquid chromatography, wherein the threshold accumulation time is at least partially based on the resolution of the liquid chromatography.

7. The method according to any one of the preceding claims, wherein: The analytical instrument includes an ion source upstream of the ion storage device and one or more ion optical devices disposed between the ion source and the ion storage device. as well as The threshold accumulation time is based at least in part on the additional time that ions spend passing through one or more ion optics devices.

8. The method according to any one of the preceding claims, wherein: The analytical instrument includes a downstream mass analyzer downstream of the ion storage device and one or more ion optical devices disposed between the ion storage device and the downstream mass analyzer. as well as The threshold accumulation time is based at least in part on the additional time that ions spend passing through one or more ion optics devices.

9. The method according to any one of the preceding claims, wherein the threshold accumulation time is at least partially based on the space charge limit of the ion storage device or downstream mass analyzer.

10. The method of claim 9, wherein the threshold accumulation time is at least partially based on the ions to be accumulated in the ion storage device.

11. The method according to any one of the preceding claims, wherein the method includes, when it is determined that the target cumulative time is greater than the threshold cumulative time, taking the average, sum, or weighted sum of the results of the step of analyzing each injected pulse.

12. The method according to any one of the preceding claims, wherein the method includes limiting the number of shorter cumulative times based on a predetermined maximum number.

13. The method according to any one of the preceding claims, wherein the plurality of shorter cumulative times are not equal.

14. The method according to any one of the preceding claims, wherein the method includes adjusting one or more analysis parameters between each injection pulse when it is determined that the target cumulative time is greater than the threshold cumulative time.

15. The method according to any one of the preceding claims, wherein the ion storage device is a radio frequency (RF) voltage ion storage device comprising electrodes for extracting ions from the ion storage device by applying a DC voltage.

16. The method according to any one of the preceding claims, wherein determining the target accumulation time includes analyzing an ion sample representing ions to be accumulated in the ion storage device.

17. The method of claim 16, wherein the ion sample is analyzed using a second mass analyzer to determine the target accumulation time, wherein the second mass analyzer is different from the downstream mass analyzer.

18. The method of claim 17, wherein the second mass analyzer is an electrostatic orbital trap mass analyzer.

19. The method according to any one of the preceding claims, wherein the ion storage device is or includes one or more of the following: an ion trap; an ion extraction trap; an ion accumulation device; an ion trapping zone; an analytical ion trap; an orthogonal accelerator; a cell lysis device; a reaction cell and / or a collision cell.

20. The method according to any one of the preceding claims, wherein: An ion storage device is one area of ​​an ion scheduling device; Accumulated ions in an ion storage device include the simultaneous accumulation of multiple precursor ions separated by a certain mass-to-charge ratio in the ion storage device; and Accumulated ions are injected in a pulsed manner for analysis, including both individual and sequential injections of accumulated ions from each parent ion from the ion storage device.

21. The method of claim 20, wherein each of the plurality of precursor ions has a different target accumulation time, the method further comprising terminating the accumulation of precursor ions when the target accumulation time is reached or a limit for a shorter accumulation time is reached.

22. The method of claim 21, further comprising accumulating additional precursor ions after termination of precursor ion accumulation.

23. The method according to any one of claims 20 to 22, further comprising using an algorithm that takes into account the mass-to-charge ratio of each precursor ion to determine and / or optimize the selection and / or order of precursor ions to be accumulated simultaneously.

24. An analytical instrument for analyzing ions, the analytical instrument comprising: Ion storage devices; as well as Control system; The control system is configured to determine the target cumulative time and whether the target cumulative time is greater than the threshold cumulative time. The control system is configured such that when the target cumulative time is determined to be shorter than the threshold cumulative time: To enable the instrument to accumulate ions in the ion storage device within the target accumulation time; and The instrument injects accumulated ions in a pulsed manner for analysis; The control system is configured to, when the cumulative time of the target is determined to be greater than the cumulative time of a threshold: Multiple shorter cumulative times are defined, each shorter than the target cumulative time. The shorter cumulative time is determined based on the target cumulative time and the threshold cumulative time. as well as For each shorter ion accumulation time, the instrument is adjusted accordingly: Ions are accumulated in an ion storage device within a short ion accumulation time, and the accumulated ions are then pulsed and analyzed within the same short ion accumulation time; and The control system is configured to enable the instrument to perform analysis of the injected pulses.

Images