JP2008542767A - Eliminate dynamic background signals in data-dependent data collection for chromatography / mass spectrometry - Google Patents

Abstract

Method and system for acquiring mass spectrometry data of a substance. The method is between subjecting a substance to a chromatographic process or other separation process, ionizing its output, subjecting the ionized output to recursive mass analysis, and iterative analysis. Providing improved processing and analysis of the acquired data. A system according to one aspect of the present invention receives an ion source, a mass analyzer capable of analyzing ions of a selected mass, and a signal representing data representing a plurality of mass analyzes from the mass analyzer. The signal is held.

Description

(Field)
The present invention relates generally to the field of mass analyzers, and more specifically to automated MS / MS collection using data-dependent collection techniques to identify eluted compounds in a chromatography / mass spectrometry system. The present invention can also be used for post-collection data processing in the identification of species of interest in complex mixtures.

(Introduction)
Mass spectrometers are often combined with chromatographic systems for identification and characterization of species eluted from a test sample. In such a combined system, the eluting solvent is ionized and a series of mass spectra of the eluting solvent is acquired at specific time intervals (eg, in the range of 0.01-10 seconds) for subsequent data analysis. Is done. Because test samples can contain many species or compounds, it is possible to automatically determine or identify the species or compounds of interest that are eluting and to perform MS / MS analysis to characterize them. It is often desirable. However, identifying species of interest in complex mixtures in real time can be a difficult task.

  Various automated tools associated with mass analyzers, as well as data collection and analysis software associated with mass analyzers, have been developed to solve this problem. A well-known automated tool is the IDA (TM) (Information Dependent Acquisition (TM)) system, which is available from MDS Sciex Inc. And marketed by Applera Corporation. During the data collection process, the tool identifies mass peaks in the mass spectrum to select precursor ions. The tool then enters one or more successive stages of mass spectrometry (MS / MS or MS / MS / MS) where the selected precursor ions are fragmented. The resulting MS / MS (or higher) spectrum is a synthesis of all fragmentation processes (precursor ions to fragment ions and fragment ions to other fragment ions) that are acceptable in terms of energy. . Spectral abundance and / or dissociation pathways described by successive MS steps can be used to identify compounds when examining spectral databases or MS / MS libraries, or when providing structural information used to characterize compounds. Can be extremely useful for.

  Other manufacturers of mass spectrometry systems provide similar real-time data dependent switching functions. For example, Thermo Finning LLC (San Jose, Calif.) Has marketed the DDE (Data Dependent Experiment (TM)) tool, and Waters Corporation (Micromass (TM)) has developed the Data Directed Analysis (D) (D) tool. Commercially available.

  The real-time data-dependent switch function described above can be used, for example, in applications such as some in vivo sample analysis or single protein digestion analysis, in which the detection of the mass peak of interest is very easy. Can provide adequate results. However, when dealing with more complex sample sets, such as mixtures of biological fluids (eg urine or plasma extracts) or digested proteins (eg digested cell lysate) many other There may be a major component or species that will “shadow” the subject or species of interest, hide the subject or species of interest, Will have a weak signal strength, and as a result, it will not be possible to efficiently select the species of interest (ionized). In essence, it is often difficult to detect species eluting at low levels of concentration.

  In the IDA (TM) tool, the selection of mass peaks that are "selected" by the system for MS / MS can be done by using the inclusion list or by a more detailed survey scan (e.g., neutral loss known in the art). , Precursor) and EMC (enhanced multi-charged scan). However, these approaches assume some knowledge about the sample being analyzed and are not always applicable. Instead, a dynamic exclusion process can be used, in which ions are disregarded during the next few scans once the ions for dissociation have been selected. The ion with the highest intensity peak at is selected for dissociation. However, this does not solve the problem with small concentrations of species eluting simultaneously with many major components.

  It should be recognized that proper selection of precursor ions is important in species identification. Appropriate selection of ions also ensures that a minimum amount of useful information is collected in data-dependent collection techniques. This can facilitate faster and simpler species identification and characterization.

(Overview)
In general, systems and methods according to the present invention elute simultaneously with a small concentration of species, and many other major components, by identifying fast-rising mass signals or other characteristic mass signals. It is possible to identify other species that are present. This can be done preferably by comparing the mass analysis with a mass analysis background that includes one or more previously acquired mass analyses.

  According to one aspect of the present invention, a method for obtaining mass spectrometry data of a substance is provided. In this method, the material is subject to a chromatographic process and its output is ionized. Mass spectrometry is acquired from the ionized output. Thereafter, ions with fast rising mass signals are identified by comparing the current mass analysis with the mass analysis background that may include one or more previously acquired mass analyses. Is done. The identified ions are then fragmented and the resulting mass analysis is recorded. These steps are preferably repeated dynamically, so that virtually all eluting species from the chromatography column are identified by mass and fragmentation to obtain additional mass spectrometry information. It becomes.

  The ions associated with the fast rising mass signal can be identified, for example, by subtracting the previously acquired mass analysis from the current mass analysis or by averaging. Alternatively, ions associated with a fast rising mass signal determine the change in the proportion of each mass signal value in the current mass spectrum relative to the value or average value in the mass analysis of one or more previously acquired outputs. Can be identified.

  The identification of fast rising mass signals can be further refined or improved by using additional mathematical techniques. The mathematical techniques may include, for example, algorithms for smoothing or approximating various data or curves, and / or additional algorithms, which may be mathematically inferred curve shapes or approximated curve shapes. Is used to approximate the rate of increase, decrease, or derivative describing the elution of various analytes. For example, LC / MS / MS analysis uses data representing the ion current at a particular point in time associated with previous scans based on the intensity of these ions across many previous MS scans. By applying curve fitting or other curve approximation algorithms to this data, one or more ions having a mass-to-charge ratio (m / z) of interest can be identified and extracted. Full or partial chromatograms (XIC) of ions can be generated. The first derivative or other derivative at the time of interest (eg, the derivative with respect to time) is determined or approximated to determine if the ion elution rate is fast rising or interesting. obtain.

  Accordingly, in another aspect, the present invention provides systems and methods for obtaining mass spectrometry data describing a substance. A system according to this aspect receives a signal representing data representing a plurality of mass analyzes from an ion source, a mass analyzer capable of analyzing ions of a selected mass, and the mass analyzer, and the signal And a controller configured to hold the controller. The controller is configured to generate information useful for describing a chromatogram of at least one extracted ion by using data related to multiple mass spectrometry and non-linear or other curve approximation algorithms. And using the generated information to generate additional mass spectrometric information (including but not limited to MS / MS spectra) useful for further analysis of the ionized material. It is configured.

  The present invention further provides a method suitable for implementation using such a system.

  If desired, one or more identified ions can be placed on a dynamic exclusion list. Such ions are then not considered as being associated with a fast rising mass signal or a mass signal of interest, so for subsequent mass analysis, one or more associated with other signals with a fast rising edge. It is possible to identify and select ions. If necessary, a precursor scan or a neutral loss scan can be performed prior to identification of ions having fast rising mass signals.

  Other frameworks and processes can be used to reduce the amount of data that is recorded and subsequently processed by the mass analyzer and its controller, and even to increase the speed, efficiency, and accuracy of the analysis process. . For example, one or more thresholds may be established so that only ions of m / z ratio detected at least by the minimum intensity mass analysis desired are recorded and determined before determining the detected intensity. Further processing takes place. This is particularly useful when used in conjunction with other methods and processes according to the present invention, as it helps, for example, reduce processing of data related to impurities or materials that may be of no interest. It is.

  Once mass spectrometry data is acquired, for example, compare the fragmentation of identified ions with a mass spectrometry database for automatic identification of eluted compounds or use in compound characterization By doing so, mass spectrometry can be acquired.

  Other aspects of the invention provide systems and apparatus for performing the methods and processes described above.

(Description of various embodiments)
FIG. 1 shows the basic components of a liquid chromatography-mass spectrometry (LCMS) system 10, which includes a chromatography column 12, which is known in the art. As is known, it is connected to a mass analyzer 14 capable of performing multi-stage mass analysis. An example of such a system is the QSTAR (TM) or API 4000 (TM) LC / MS / MS system marketed by MDS Sciex, although those skilled in the art will recognize that the present invention is MS and MS / MS It can be appreciated that it can be applied to any suitably controlled system with other multi-MS performance (eg, 3D trap, TOF (time-of-flight) analyzer, or Fourier transform (FTMS) analyzer). Data collection controller 16 is capable of automatic MS and MS / MS data collection and maximum information extraction from a single LC / MS analysis.

  The controller 16 is configured to receive, store, and process data signals collected or provided by the mass analyzer 14 and command signals configured to control operations performed by the mass analyzer 14. Configured to provide. The controller 16 further provides a user interface suitable for controlling the MS system 10, which includes input / output devices suitable for receiving and executing system commands from a user, for example. Contains. In particular, the controller 16 is configured to process the data collected by the mass analyzer 14 and provide a command signal (based at least in part on information generated by processing the data) to the mass analyzer 14. ing.

  As will be appreciated by those skilled in the art, the controller 16 may include any system or device for data collection and processing suitable for achieving the objectives described herein. The controller 16 may include, for example, a suitably programmed computer, or a programmable general purpose computer, or an application specific computer, or other automatic data processing apparatus associated with programming and data collection and control devices. As described herein, the controller 16 controls and monitors, for example, an ion detection scan performed by the mass analyzer 14; for example, the mass of ions provided by the liquid chromatography (LC) column 12. Data representing the detection as described above by the analyzer 14 is configured to be collected and processed.

  Accordingly, the controller 16 may include one or more automatic data processing chips configured to provide automatic and / or bi-directional control with a suitably encoded structured program, It may include one or more applications and operating systems, and any necessary volatile or persistent storage media. As will be appreciated by those skilled in the art to which this specification pertains, a wide variety of processors and programming languages suitable for practicing the present invention are now available on the market and will continue to be developed. There is no doubt. Examples of suitable controllers, including appropriate processors and programming, appear to be incorporated into QSTAR (TM) or API 4000 (TM) LC / MS / MS marketed by MDS Sciex (Ontario, Canada). It is a thing.

  An ion source suitable for use in practicing the present invention may include any LC column or other ion source 12 that is compatible with the purposes disclosed herein. For example, as will be appreciated by those skilled in the art, any liquid chromatography or other sustained-release ion source may meet the requirements. The present invention is particularly useful in combination with LC columns and other ion sources (which produce sustained or other streams of ions of various properties), for example suitable for continuous trace deposition Includes LC-Matrix-Assisted Laser Deposition Ionization (LC-MALDI) system.

  The mass analyzer 14 may include any ion detector and / or analyzer that is compatible with the objectives disclosed herein. For example, as will be appreciated by those skilled in the art, 3D traps, TOF detectors, and other types of mass analyzers may meet the requirements. The present invention is particularly useful in combination with mass analyzers capable of repetitive or recursive scanning of ions or other sampling.

  FIG. 2 shows a portion of the data output as part of an LC / MS analysis performed on human growth hormone (Hgh) digestion using the API 3000 (TM) system. The data shown belongs to the analysis run of 57-63 minutes. Signal 40 plots the overall ionic strength (TCI) of the run, which represents the overall concentration of all species that are eluting. The mass analyzer 14 also records the ionic strength for a given range (more specifically, the m / z range) of the mass, and the signals 42 to 52 have a mass to charge ratio of 694 m / z, 578 m / z, respectively. Plotted extracted ions counting ions at 713 m / z, 734 m / z, 748 m / z, and 913 m / z. These signals depict the intensity of various (but not all) eluting species over this time.

  While it can be seen that there are many eluting species between about 58.5-59 minutes of the run, FIG. 2 shows a subset of them. The MS spectra for these eluting species acquired at times t0 and t1 are shown in FIG. 3 (time t1) and FIG. 4 (time t0), and the ionic strength at each of these times is shown in Table 1 below. It is summarized in.

  Since many mass peaks appear at approximately the same time, it was difficult for prior art systems to select mass peaks for performing secondary mass analysis. In the presence of the high intensity signal generated by the ions 694 m / z, this problem is because there are many low intensity signals (especially ions of mass 578 m / z, 713 m / z, and 748 m / z). It becomes even more difficult.

  FIG. 5 is a schematic diagram showing ions that can be selected by a prior art controller for secondary mass analysis, which uses a prior art data-dependent collection tool. It does not use dynamic background signal elimination according to the invention. FIG. 5 shows that between 57.16 and 60.76 minutes of execution, the prior art data collection controller (IDA (TM) system) allows the system to apply dynamic exclusion criteria. It shows that only ions 694 m / z were selected to perform secondary mass analysis (when not programmed). However, the other mass eluted during the above time by running the chromatography is a representative mass eluted over the area indicated in the figure. Thus, according to prior art systems, the quality of the analysis can be adversely affected.

  In contrast, in a preferred embodiment, the controller 16 compares the most recently collected MS spectrum with a dynamic “spectrographic background” at any given time point. Try to identify the fastest rising signal or other fast rising signal. For ease of illustration, a simple example of this technique can be understood by comparing FIG. 3 (later time) and FIG. 4 (previous time). From this comparison, it can be seen that the mass 748 m / z has the fastest rising signal (which corresponds to signal 50 in FIG. 2).

  This phenomenon can be quantified by the controller 16 by using two simple quantification methods: (i) subtracting the current value of the signal from the previously collected MS spectrum; (ii) the signal Changing the proportion in the value of. Table 1 shows that by using either one of these criteria, the controller 16 can move both 748 m / z and 713 m / z ions to the top of the IDA selection.

このようにして、質量７４８ｍ／ｚおよび７１３ｍ／ｚのイオンが選択されると、コントローラ１６は、これらのイオンをフラグメント化し、結果として得られた質量スペクトルを記録することによって、質量分析器１４に対し、質量分析器１４を動的に動作させ、２次質量解析を実行させるように構成されたコマンド信号を提供し得る。好適な実施形態においては、所定数の選択されたイオンがフラグメント化されるが、代替的な実施形態においては、「最良」のマッチ（例えば、７４８ｍ／ｚ）のみが、その後のフラグメント化のために選択され得る。

In this way, once ions of mass 748 m / z and 713 m / z are selected, the controller 16 fragments the ions and records the resulting mass spectrum to the mass analyzer 14. In contrast, the mass analyzer 14 may be dynamically operated to provide a command signal configured to perform secondary mass analysis. In a preferred embodiment, a predetermined number of selected ions are fragmented, but in alternative embodiments, only the “best” match (eg, 748 m / z) is for subsequent fragmentation. Can be selected.

  Both of the quantification methods described above provide advantages: in many situations, percentage or relative gain is a preferred technique when looking at growth rates, while absolute gain increases significantly. It is calculated by the subtraction method for the seeds it has. The term “fast rising signal” is specifically calculated to include signals that rise rapidly (ie, relative terms are calculated by the growth rate, absolute terms are calculated by the subtraction method). Defined).

  FIG. 6 shows the results of these techniques for data acquired between 57.16 and 60.76 minutes of execution. Each block 60 represents one or more consecutive scans, and various ion mass peaks have been selected by the controller 16 to perform a secondary MS analysis. The selected m / z ratio and number of scans (eg, 694-8 scans, 5 scans, 2 scans) are shown, and the identified m / z range is selected for the scans. FIG. 6 is a schematic diagram illustrating ions selected for secondary mass analysis according to a preferred embodiment of the present invention, which identifies a fast rising mass signal at any given time. The purpose is that. With dynamic background signal rejection, more ions are correctly selected for IDA (even when they are not the reference peak of the mass spectrum). If the ions correspond to signals that rise faster than signals corresponding to other selected ions, they are detected and the data is used for further analysis.

  In the examples provided so far, the controller 16 has used data representing one of the previous MS spectra to determine the background of mass spectrometry. However, instead of the controller 16, it is possible to obtain and compare mass analysis backgrounds by averaging the mass signals over many MS spectra. For example, FIG. 7 relates to performing LC / MS on ions of mass 668.5 m / z, 1412.0 m / z, and 1466.0 m / z (indicated by signals 62, 64, and 66, respectively). Shown are counts of various extracted ions acquired between 51.4 and 53.6 minutes. As indicated by blocks 70a, 70b, and 70c in FIG. 7, the number of spectra used to determine the average value of the signal background is the number of coverages or data points that can be selected over the mass peak. To decide. For example, in block 70a, the background average for signal 62 at time t4 is obtained from one of the previous MS spectra (obtained 0.05 minutes or 3 seconds ago) so that the controller Consider only the rising edge. As soon as the signal passes its peak value, a negative number result is obtained by using subtraction or percentage change (this subtracts the value of signal 62 at time t4 from the value of the signal at time t3). To understand).

  However, at block 70b, when controller 16 determines the background value of signal 62 by utilizing data representing the three previous spectra, a wider coverage or data point over the mass peak. Numbers are shown to be considered. Block 70c shows the coverage when 10 previous spectra are used to determine the background value of signal 62. Such techniques are similar to moving averages and help to smooth out sudden perturbations in the signal and avoid false results. The number of spectra used by the controller to determine the average value of the mass signal background can preferably be set or canceled by the user of the system.

  Further mathematics using data available from many MS mass analyzers (eg, generated by repetitive or recursive MS cycles in smoothing out sudden perturbations in the signal and reducing false results) Methods based on the application of genetic techniques include, for example, various data or curve smoothing algorithms that evaluate the rate of increase or decrease or other aspects related to elution of various analytes from an ion source, such as an LC column, for example. Used to do. As described above, the number of spectra that the controller 16 uses to determine the average value of the mass signal background can be set or canceled by the user of the system, or based on, for example, a statistical assessment of the quality of the data. Can be determined automatically.

  For example, in LC-MS analysis, the controller 16 may identify one or more ions having a mass-to-charge ratio (m / z) of particular interest and generate all or part of the XIC (see above). Generated based on the intensity of the identified ions detected by the mass analyzer 14 via a number of MS scans). This uses, for example, data representing one or more ion currents at a particular point in time associated with a specified number of previous scans and applies curve fitting or other suitable algorithms to the data Can be done. For example, based on a data curve that has been smoothed or approximated or evaluated to determine whether the elution rate of ions is a fast rise or is of interest for further analysis, At various times of interest or other points of interest in the analysis, first or higher order derivatives (eg, derivatives with respect to time) may be determined. Such a technique is particularly useful in identifying fast rising signals, for example, by calculating growth rates and the like.

  In a quick and accurate assessment of the state or content of ions being eluted or provided, the value of such a technique can be any one or more to concentrate on analysis on the desired portion of the detected mass spectrum. It can be improved by additionally using additional processes.

  For example, in some embodiments of the invention, the selection of ions for secondary MS analysis can be performed in addition to the fast rise mass signal criteria or in combination with the fast rise mass signal to other criteria. Can be based. For example, if necessary, the dynamic background comparison described above can be combined with dynamic exclusion. For example, in one framework, ions that are identified as being associated with a fast rising mass signal are placed on the exclusion list and are not considered for a predetermined number of subsequent scans. This technique can be enhanced by delaying the placement of ions on the exclusion list until a predetermined continuous time after ions having a fast rising mass signal are selected. In addition, if desired, the controller may use an MS or MS / MS scan (eg, precursor and / or neutral loss scan) prior to applying the dynamic background comparison.

  As another example, one or more threshold values may be determined by a user as a criterion in determining which data acquired in a given scan or series of scans should be stored or retained for further processing. Or by using the controller 16 can be established automatically and / or bidirectionally. As a result, data is recorded and processed only for ions of the m / z ratio detected by the mass analyzer at the desired minimum intensity ratio.

  As described above, data curve smoothing algorithms, dynamic exclusion techniques, intensity thresholds, and other techniques may be used, for example, data related to impurities or uninteresting material collected by the controller 16 and subsequently processed. Is used to improve the efficiency of data processing. Such techniques are particularly effective when used in conjunction with each other and / or in conjunction with other methods and processes related to the present invention. These are particularly useful when facing high data scanning / collection rates, for example in recursive TOFMS and / or FTMS analysis.

  FIG. 8 is a schematic diagram of an embodiment relating to a method of processing data recorded in a recursive TOFM analysis according to the present invention. Process 800 is suitable for being implemented by the system shown in FIG. 1 under the control of a controller, such as, for example, controller 16.

  At 802, the controller 16 issues a command signal that causes the mass analyzer 14 to perform a survey scan of the detector associated with the mass analyzer and relates to ions detected by the detector. It is configured to provide the controller 16 with data representing the m / z ratio. For example, in the case of a TOF mass analyzer, the mass analyzer 14 tells the controller 16 the number of m / z ratios associated with ions detected by the detector within a given time or during a given survey period. Representing data may be provided. Here, a given time or a given survey period is related to the time at which each ion is detected (eg, relative time from the start of the current survey period). In some cases, the amount of data required and provided to the controller 16 during a scan by the mass analyzer 14 is relatively large. For example, in a typical analysis performed by a QSTAR ™ LC / MS / MS system, the result of a full survey scan of the detector during the scanning time results in tens of thousands of detectors (eg, 10,000). 1 million or more, typically 500,000 data points). Each is composed of relative time and m / z ratio, which corresponds to the number of ions detected. The controller 16 may hold the acquired data in volatile memory, such as random access memory, flash memory, or other readily available buffer.

  At 804, the controller 16 determines, for example, the total number of ions of each m / z ratio detected during the survey scan at 802 and preferably holds data related to the m / z ratio of interest. On the other hand, the data provided by the mass analyzer can be sorted into a peak list by ignoring or deleting the remaining data. The controller 16 may advantageously continue to keep stored data (which may be referred to herein as a peak list) in volatile memory or other easily accessible memory. The stored data can correspond to, for example, a trace, which corresponds to a scan performed at time t1, as shown in FIG. As a result, in the case of a typical analysis performed by a QSTAR (TM) LC / MS / MS system, the number of data points of interest associated with a given survey of detectors is the same during the entire survey scan. From 10,000 to over a million data points acquired in a very small order of data points, for example, in a typical analysis, can be reduced to about 1000 data points. The reduced data set can be maintained in volatile and / or persistent memory for further access and processing.

  In step 804, the ions and / or m / z ratios contained in the retained data identified by the peak list use the process described herein, as described herein. Can be automatically identified by the controller 16 or specified, for example, by using a batch or bidirectional command signal provided to the controller 16.

  At 806, the controller 16 can retain the retained data in volatile memory, for example by applying a data reduction technique as described herein, or subsequently processed by the controller 16. Can be reduced as much as can be done. For example, the controller 16 is established by the user with the intensity of data (eg, all detected ions) representing various m / z (or peaks) detected during a given scanning survey. Or a threshold determined by system 10 may be compared. For example, the absolute or relative intensity or detection level of a given charge can be established, and the controller 16 can determine the m / z ratio corresponding to an intensity peak below an established threshold, eg, by an appropriate program. Can be ordered to ignore. For example, a threshold of 5.05e5 cps may be established, and data corresponding to the m / z ratio of detected data intensity below that threshold is not retained and considered for further processing. As a result, for example, the data corresponding to peak 901 in FIG. 9 is excluded from further consideration (peak 901 does not appear in the cumulative trace of FIG. 9) and is associated with curves or peaks 62, 64, 66. Only the data to be processed can be further processed.

  Alternatively or additionally, relative values can be established. For example, in the analysis corresponding to FIG. 3 and / or FIG. 4, relative intensity peaks below a selected threshold may be excluded from further processing. For example, if a threshold of 10% is set, the controller 16 will retrieve data related to peaks 371, 1121, 1530, 713, and 887 (as well as other peaks not shown but labeled in FIG. 3). May stop processing.

  As a further example, at 806, the controller 16 reduces the data held in volatile memory (otherwise these data are then transferred to the controller by application of the ion extraction criteria described herein. As a result, data corresponding to the selected m / z ratio can be excluded from further processing by the controller 16.

  Applying such data reduction techniques at 806, in the case of a typical analysis performed by a QSTAR (TM) LC / MS / MS system, in subsequent steps 806, the interest associated with a given survey The number of certain data points is reduced from about 1,000 retained points to about 100 (or fewer) data points. Each represents the m / z ratio of interest, as well as the intensity of the charge recorded during the respective survey or scan period. The reduced data set can be kept in volatile memory, preferably in persistent memory, for subsequent access and processing. As will be appreciated by those skilled in the art, a substantial decrease in the processed data leads to an increase in the processing time of the data of interest, thus reducing both the number and quality of output that can be generated in connection with the data. Can increase the rate at which MS scans can be processed. This may improve the quality of the data required and processed by the system as described herein.

  At 808, the controller 16 accesses data associated with the selected number of previous survey scans and generates an XIC for one or more specified ions of interest (ie, m / z ratio). obtain. This can be accomplished in various ways. For example, as a first step, a linear curve approximated by a line segment represented by a straight line drawn between individual time-m / z intensity data points may be generated. Such a curve is illustrated by curve 62 in FIG. 9, which is composed of line segments drawn between data points 62-1 to 62-22. Data related to the XIC generated in this manner can be used to identify fast rising signals, for example, as described herein.

  However, as observed in some cases, using a linear (ie, linear) curve approximation generated by a linear combination between data points in an XIC can lead to inaccuracies or other difficulties in the analysis. Will bring. For example, when the relative portion of the analyzed sample component that is eluted or provided by the ion source 12 changes at a relatively high rate when compared to the cycle time during an MS survey scan, Or peaks or valleys in the feed rate are lost and then evaluated, which can result in misidentification of the compound as well as the relative levels of the components of the compound. Similarly, when the contact ratio (due to various m / z ratio ions impinging on the area of the detector plate in the mass analyzer) is too high to be fully processed by the analyzer (ie, processing of the area of the detector). When the capacity is exceeded and the detector is saturated), peaks in the XIC trace can be evaluated and lead to similar results.

  Thus, in many cases, based on the acquired data points, an improved quadratic curve, or a higher order curve, or other non-linear curve (or there may be an improved linear curve). By using the expression, the quality in the analysis of mass spectrometry can be improved. Thus, in step 810, the controller 16 accesses the acquired trace data and executes any of a variety of XIC curve smoothing algorithms to provide all or any of the XICs generated by the controller 16. Provides a curve approximation of the part. The algorithm executed by the controller 16 may include any suitable curve fitting or smoothing algorithm, or other suitable mathematical operations, such as, for example, a variable linear curve fitting method. And non-linear curve fitting methods (least square fitting, weighted least square fitting, and robust fitting (all with or without boundaries)); splines or interpolation (second or higher order polynomials or exponential functions) And can be used to generate various information about the generated XIC. Such information can be, for example, local or global XIC curve approximation; rate of change at any one or more points on the curve (first derivative), local minimum or maximum point of the curve (where the first derivative is Zero), and the area under the curve (section).

  Any algorithm suitable for any purpose described or presented herein may be used. As will be appreciated by one of ordinary skill in the art, a number of suitable algorithms are known and will undoubtedly be developed in the future. In one embodiment, the first derivative is used with a simple non-linear smoothing of 2-3 points per data point pair to compare the intensity derivatives for dynamic ion selection.

  FIG. 9 includes a diagram of the XIC generated in accordance with this aspect of the invention. As already described, the curve 62 is a linear or straight line generated by the controller 16 by using the data provided by the mass analyzer 14 during 22 different survey scans at times t1-t22. Represents an approximation. By using data representing the intensity of ions at about 668.5 m / z during the 22 recorded survey scans, the controller 16 determines that the curve 62A (the actual ion of ions at that m / z ratio) Data describing (smoothed XIC curves that may more closely approximate elution) is generated and plotted or displayed.

  At 812, the controller 16 accesses data representing a smoothed XIC curve (eg, curve 62A) and determines a first derivative or other value or function associated with the point of interest on the XIC. To do. Using this, for example, at 814, whether the XIC is quantifying the selected point as a fast rising signal, or whether the ion associated with the XIC identifies the ion of interest, generated at 804 Whether to include in the included inclusion list. For example, as described above, the user of system 10 identifies to controller 16 one or more eluates or other ions associated with the fast rise signal provided by source 12 to be included in the peak list. Can be ordered to.

  The current list for the identified ions of interest is appropriately modified at 814 and the controller 16 causes the list to be kept in volatile or persistent memory along with one or more XICs of interest and process 800. May repeat the secondary or subsequent MS survey at 802. Loops 802-814 are repeated until all compounds of interest or all relative percentages of interest have been identified, or the user of controller 16 and / or system 10 has completed the desired mass analysis. Can be repeated until satisfied.

  The present invention improves the detection of low intensity species that may be co-eluting or provided by the source 12 in the presence of higher concentration species (typically detected at high intensity). As a result, using this approach is expected to preserve the integrity of isotopes or isotope ratios. In addition, the present invention offers the possibility of simplifying many of the criteria that the user needs to program the controller.

  The present invention also minimizes the amount of data collected while improving efficiency in collecting useful information. This provides, for example, the additional benefit of minimizing the amount of information that is shifted and improves real-time analysis capabilities for such data.

  A preferred embodiment has been described in connection with monitoring a single reaction. However, it can be appreciated that the present invention can be applied to a variety of further analysis processes. Further analysis processes include, for example, selected ion monitoring (SIM), selective reaction monitoring (SRM), multiple reaction monitoring (MRM) (including cases involving multiple generations of ion conversion), Includes charge scanning. It should be understood that the present invention can be applied to capillary electrophoresis mass spectrometry systems (CE-MS) and gas chromatography mass spectrometry systems (GC-MS). Those skilled in the art can appreciate that various modifications can be made to the preferred embodiments without departing from the spirit and scope of the present invention.

  FIG. 10 (including parts 10a and 10b thereof) provides a table of the results of a comparison between an analysis obtained in accordance with the present invention and an analysis obtained in accordance with a normal IDA process.

  FIG. 10a is detected and verified from a single LC injection by using conventional IDA features (“regular IDA”) and system and process embodiments according to the present invention (“IDA-DBS”). The analysis result of the metabolite of haloperidol is shown. As shown in the table, a significant improvement in the success rate was obtained by using the system and process according to the present invention.

  FIG. 10 b is detected and verified from a single LC injection by using conventional IDA features (“Regular IDA”) and system and process embodiments according to the present invention (“IDA-DBS”). The analysis result of the metabolite of diclofenac is shown. As shown in the table, a significant improvement in the success rate was obtained by using the system and process according to the present invention.

  FIG. 11 is a plot of sample intensity (cps) of various masses detected as a function of time (minutes) over a portion of the LC / MS run, as well as an inset of local plot derivatives. A local derivative as shown in the inset can be calculated, for example, by using a desired number of past points in the trace. In the example shown, two traces are shown, the LC peak for the selected ion is shown as a solid line, and the flat signal is shown as a dashed line. The first derivative curve for each trace is shown by using the curve approximation algorithm described herein based on the last 20 data points provided by the controller 16. When the first derivative reaches a maximum at about 13.5 seconds (shown in the middle inset), the controller 16 selects the ions associated with the solid trace for further mass analysis.

  Although the foregoing invention has been described in some detail for purposes of clarity and understanding, those skilled in the art will recognize, in form and detail, from the correct scope of the invention in the appended claims after reading this disclosure. It can be appreciated that various changes can be made without departing. Accordingly, the present invention is not limited to the exact details or constructions of the components or methods described above, but is described in this disclosure, including the drawings, except as necessary or essential to the purpose. No order to the steps or steps for the method or process is intended or suggested. In many cases, the order of the purpose steps may be changed without changing the purpose, effect, or meaning of the described methods.

The above and other aspects of the present invention will become more apparent from the description of specific embodiments of the invention and the accompanying drawings. The accompanying drawings are for illustrative purposes only and are not intended to limit the principles of the invention.
FIG. 1 is a schematic block diagram of an LC / MS system suitable for use in practicing the present invention. FIG. 2 is a graph plotting the intensity (cps) of various masses detected as a function of time (minutes) over a portion of the LC / MS run. FIG. 3 is a mass analysis performed at a first time (t1) in a portion of the LC / MS run shown in FIG. FIG. 4 is a mass analysis performed at a second time (t0) in a portion of the LC / MS run shown in FIG. FIG. 5 is a schematic diagram illustrating ions that may be selected for secondary mass analysis, which is performed using a prior art data-dependent collection tool, but according to the present invention. No background signal rejection is used. FIG. 6 is a schematic diagram illustrating ions selected for secondary mass analysis in accordance with a preferred embodiment of the present invention. FIG. 7 is a schematic diagram showing a portion of the mass peak, which can be taken into account in the detection of a fast rising mass signal. FIG. 8 is a schematic diagram illustrating a method of processing recorded data in multi-MS analysis according to the present invention. FIG. 9 is a diagram of an extracted ion chromatogram produced in accordance with the present invention. FIG. 10a provides a table of comparison results obtained using a process according to the prior art and a process according to the present invention. FIG. 10b provides a table of comparison results obtained using a process according to the prior art and a process according to the present invention. FIG. 11 is a plot of sample mass (cps) of various masses detected as a function of time (minutes) over a portion of the LC / MS run.

Claims (32)

A method for obtaining mass spectrometry data describing a substance, comprising:
Ionizing the material;
Obtaining a current mass analysis of a portion of the ionized material and retaining data representing the current mass analysis;
Obtaining a subsequent mass analysis of at least two further portions of the ionized material and retaining data representing the at least two further mass analyses;
Use the current mass analysis and the data associated with the at least two subsequent mass analyses, and generate information useful for describing a chromatogram of at least one extracted ion by using a non-linear curve approximation algorithm And
Generating further information useful for further analysis of the ionized material by using the generated information useful for describing a chromatogram of the at least one extracted ion. how to.   The generated information useful for describing a chromatogram of the at least one extracted ion is used to generate information describing a derivative associated with the chromatogram of the extracted ion. Item 2. The method according to Item 1.   The method of claim 2, wherein the derivative associated with a chromatogram of the extracted ions is used to identify at least one ion associated with a fast rising signal. The method of claim 1, comprising performing a precursor scan prior to obtaining a current mass analysis of a portion of the ionized material. The method of claim 1, comprising performing a neutral loss scan prior to obtaining a current mass analysis of a portion of the ionized material. Including automatically identifying substances by comparing data representing at least one mass analysis with data stored in a database representing a plurality of previously determined mass analyses. The method of claim 1. Reduce the amount of retained data representing at least one mass analysis by comparing the data associated with at least one mass analysis with specified criteria and retaining only data that meets the criteria The method of claim 1, comprising:   The method of claim 7, wherein the specified criteria includes an intensity threshold.   8. The method of claim 7, wherein the specified criteria identifies at least one ion of interest.   8. The method of claim 7, wherein the specified criteria identifies at least one uninteresting ion. A mass spectrometry system comprising:
An ion source;
A mass analyzer capable of analyzing at least one ion of a selected mass;
A controller,
Receiving a signal representing data representing a plurality of mass analyzes from the mass analyzer and retaining the signal;
Generating information useful for describing a chromatogram of at least one extracted ion by using data related to the plurality of mass spectrometry and a non-linear curve approximation algorithm;
A controller configured to use the generated information to generate further information useful for further analysis of the ionized material.   The controller generates information describing a derivative associated with the chromatogram of the extracted ions by using the generated information useful for describing the chromatogram of the at least one extracted ion. The system of claim 11, wherein the system is configured to:   The system of claim 12, wherein the controller is configured to identify at least one ion associated with a fast rise signal by using the derivative associated with a chromatogram of the extracted ions.   The controller automatically identifies a substance by comparing data representing at least one mass analysis and data stored in a database representing a plurality of previously determined mass analyses. The system according to claim 11, which is configured as follows.   The controller compares the data represented by the signal received from the mass analyzer with a specified criterion, and retains only the data that meets the criterion to determine the amount of data retained. The system of claim 11, wherein the system is configured to reduce.   The system of claim 15, wherein the specified criteria includes an intensity threshold.   The system of claim 15, wherein the specified criteria identifies at least one ion of interest.   The system of claim 15, wherein the specified criteria identifies at least one ion of interest. A controller for a mass analyzer, the controller comprising a detector capable of detecting at least one ion of a selected mass, the controller comprising:
Receiving a signal representing data representing a plurality of mass analyzes from the mass analyzer and retaining the signal;
Generating information useful for describing a chromatogram of at least one extracted ion by using data related to the plurality of mass spectrometry and a non-linear curve approximation algorithm;
A controller configured to use the generated information to generate further information useful for further analysis of the ionized material.   Configured to generate information describing a derivative associated with the chromatogram of the extracted ions by using the generated information useful for describing a chromatogram of the at least one extracted ion. The controller of claim 19.   21. The controller of claim 20, configured to identify at least one ion associated with a fast rising signal by using the derivative associated with a chromatogram of the extracted ions.   Configured to automatically identify a substance by comparing data representing at least one mass analysis with data stored in a database representing a plurality of previously determined mass analyses. The controller of claim 19.   Comparing the data represented by the signal received from the mass analyzer with a specified criterion and configured to reduce the amount of data retained by retaining only data that meets the criterion The controller of claim 19. A computer-usable medium, the computer-usable medium having computer-readable code embodied therein, the computer-readable code being transmitted to the controller of the mass analyzer
Receiving a signal representing data representing a plurality of mass analyzes from the mass analyzer;
Generating information useful for describing a chromatogram of at least one extracted ion by using data related to the plurality of mass spectrometry and a non-linear curve approximation algorithm;
Using the generated information to generate further information useful for further analysis of the ionized material;
Computer usable media.   Computer-readable code embodied in the computer-usable medium, the computer-readable code useful for describing to the controller a chromatogram of the at least one extracted ion 25. The computer-usable medium of claim 24, wherein the information is used to generate information describing a derivative associated with a chromatogram of the extracted ions.   Computer-readable code embodied in the computer-usable medium, the computer-readable code using the derivative associated with the chromatogram of the extracted ions in the controller 26. The computer usable medium of claim 25, wherein at least one ion associated with the signal is identified.   Computer-readable code embodied in the computer-usable medium, the computer-readable code having the controller represent data representing at least one mass analysis and a plurality of previously determined masses. 25. The computer-usable medium of claim 24, wherein the substance is automatically identified by comparison with data stored in a database representing the analysis.   A computer readable code embodied in the computer usable medium, the computer readable code being provided to the controller as a reference designated as data represented by a signal received from the mass analyzer; 25. The computer-usable medium of claim 24, wherein the amount of retained data is reduced by comparing to and retaining only data that meets the criteria.   30. The computer usable medium of claim 28, wherein the specified criteria includes an intensity threshold.   29. The computer-usable medium of claim 28, wherein the specified criteria identifies at least one ion of interest.   29. The computer-usable medium of claim 28, wherein the specified criteria identifies at least one uninteresting ion.   Any or all novel other features described, mentioned and exemplified herein.

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