WO2013138326A2

WO2013138326A2 - Selective analyte detection and quantitation in mass spectrometry using multiplication of high resolution signal channels

Info

Publication number: WO2013138326A2
Application number: PCT/US2013/030492
Authority: WO
Inventors: Jeffrey S. PATRICK; Kevin SIEK
Original assignee: Leco Corporation
Priority date: 2012-03-12
Filing date: 2013-03-12
Publication date: 2013-09-19
Also published as: WO2013138326A3

Abstract

Systems and methods for detecting and identifying the presence of an analyte in a sample using a high resolution mass spectrometry system. In an implementation the method includes ionizing an analyte to yield ions, passing the ions into the mass spectrometry system, fragmenting a portion of the ions passed into the mass spectrometry system such that there may be both fragment ions and non-fragmented ions passing through the system, identifying a first signal associated with the fragment ions, identifying a second signal associated with the non- fragmented ions, multiplying the first signal with the second signal to derive a third signal, and analyzing the third signal to identify a peak that is indicative of the presence of an analyte.

Description

SYSTEM AND METHOD FOR DETECTING AND OUANTIATING ANALYTES IN A

MASS SPECTROMETER

FIELD

[0001] This disclosure relates to a method and system for detecting and quantitating analytes.

BACKGROUND

[0002] High resolution mass spectrometers are generally available, such as the time-of-flight mass spectrometers discussed in U.S. Patent No. US 7,385,187 Al, filed on Jun. 18, 2004; U.S. Patent Application Publication No. US 2006/0214100 Al, filed on Mar. 22, 2006; and U.S. patent application Ser. No. 11/548,556, filed on Oct. 11, 2006 entitled "MULTI-REFLECTING TIME-OF-FLIGHT MASS SPECTROMETER WITH ORTHOGONAL ACCELERATION, each of which are fully incorporated herein by reference and those which are commercially available from LECO Corporation, such as, for example, the Citius™ LC-HRT system. The systems and methods discussed herein leverage the information obtained in such exemplary spectrometers to detect and quantitate a presence of analytes that may be present within samples.

SUMMARY

[0003] Systems and methods for detecting and identifying the presence of an analyte in a sample using a high resolution mass spectrometry system. In an implementation the method includes ionizing an analyte to yield ions, passing the ions into the mass spectrometry system, fragmenting a portion of the ions passed into the mass spectrometry system such that there may be both fragment ions and non-fragmented ions passing through the system, identifying a first signal associated with the fragment ions, identifying a second signal associated with the non- fragmented ions, multiplying the first signal with the second signal to derive a third signal, and analyzing the third signal to identify a peak that is indicative of the presence of an analyte.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The accompanying drawings illustrate various embodiments of the present system and method and are a part of the specification. The illustrated embodiments are merely examples of the present apparatus and method and do not limit the scope of the disclosure.

[0005] Figure 1 is a flowchart that describes and illustrates a method for detecting and quantitating analytes in a mass spectrometer, according to an implementation; [0006] Figure 2 is an electrical diagram in block form of a spectrometer system including a data acquisition system, according to an embodiment;

[0007] Figure 3 illustrates an ion optical rail and mass analyzer, according to an embodiment;

[0008] Figure 4 illustrates an ion interface, according to an embodiment.

[0009] Figure 5 illustrates an exploded view of the ion interface to show the fragmentation region, according to an embodiment.

[0010] Figure 6 illustrates an example of an application of an implementation of a system and method for detecting and quantitating analytes in a mass spectrometer, according to an implementation; and

[0011] Figure 7 illustrates another example of an application of an implementation of a system and method for detecting and quantitating analytes in a mass spectrometer, according to an implementation.

[0012] The details of one or more implementations of the disclosure are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims.

DETAILED DESCRIPTION

[0013] The following description of the various embodiments is merely exemplary in nature and is in no way indented to limit the invention, its application or uses. Based on the foregoing, it is to be generally understood that the nomenclature used herein is simply for convenience and the terms used to describe the invention should be given the broadest meaning by one of ordinary skill in the art.

[0014] Although the specific examples detection and quantitation systems and methods for detecting analytes are discussed in connection with directed time-of-flight (TOF) mass spectrometers, the methods and systems herein describe have applicability in many respects to all other forms of mass spectrometers, and to other systems for analyzing components by detecting analytes.

[0015] An implementation of a method for detecting and identifying the presence of an analyte in a sample using a high resolution mass spectrometry system is shown and described in Figure 1. At step SI 02, ions are passed into a high-resolution mass spectrometry system. Next, at step SI 04, a portion of the passed ions are fragmented such that there are, or may be, both fragment ions and non-fragmented ions passing through the system. The fragmentation may or may not involve so-called isolation of the ion prior to fragmentation. A first signal associated with the fragmented ions (e.g. product or daughter ions) is identified at step SI 06 and a second signal associated with the non-fragmented ions (e.g., precursor or parent ions) is identified at step S108.

[0016] Next, the first signal is multiplied with the second signal at step SI 10 to derive a third signal. The third signal is then analyzed to determine whether the multiplication of the first signal with the second signal yields a peak that is determinative of a presence of an analyte in the sample at SI 12.

[0017] Referring now to Figure 2, an electrical diagram in block form of an exemplary high- resolution mass spectrometer system that could be utilized to perform the foregoing method is shown at 10. Spectrometer system 10 includes a data acquisition system 11, a TOF mass spectrometer 12, including, but not limited to, an orthogonal or on-axis flight tube configuration using any one of a number of sources 14, such as a liquid chromatograph, a gas chromatograph, a glow discharge source, an inductively coupled plasma source, or the like. For the purposes of example only, source 14 is disposed at one end of a sample chamber 15, coupled with a flight tube 16. Disposed at one end of flight tube 16 is an ion detector 18.

[0018] As previously discussed, spectrometer 12 may generally have any configuration known in the art. Preferably, spectrometer 12 is a multi-reflecting TOF mass spectrometer or other embodiment having high-resolution capabilities. Examples of multi-reflecting TOF mass spectrometers for which the present disclosure may be used are described in the following commonly-assigned patent applications: U.S. Patent No. US 7,385,187 Al, filed on Jun. 18, 2004; U.S. Patent Application Publication No. US 2006/0214100 Al, filed on Mar. 22, 2006; and U.S. patent application Ser. No. 11/548,556, filed on Oct. 11, 2006 entitled "MULTI- REFLECTING TIME-OF-FLIGHT MASS SPECTROMETER WITH ORTHOGONAL ACCELERATION". The entire disclosures of each of these applications are incorporated herein by reference. In an implementation, the associated data acquisition system is may be a system as set forth in U.S. 7,501,621, U.S. 7,825,373, U.S. 7,884,319, the entire disclosures of each are fully incorporated by reference herein.

[0019] As discussed, the disclosed systems and methods for detection and quantitation can be used in various spectrometer systems. Accordingly, Figures 2-5 identify exemplary data collection systems but it is to be appreciated that the techniques herein discussed should not be so limited to the exemplary systems disclosed.

[0020] Referring now to Figure 3, an exemplary ion rail and mass analyzer is shown. Ion rail and mass analyzer may include ion interface 22, ion mirrors 24, an orthogonal accelerator 26, a lens array 28 (e.g., an Einzel lens array) and an ion detector 30. [0021] Figure 4 depicts an exemplary high resolution ion interface 32 having a sample nozzle 34, first and second ion guides 36, 38 separated by an ion skimmer 40. Based on this disclosure, it is to be appreciated that CID occurs about the ion skimmer 40. Interface 32 may further include an ion optics stack 42 and an orthogonal accelerator 44. Figure 5 depicts an exploded view of the CID area where ion fragmentation occurs.

[0022] With continued reference now to Figure 4 and Figure 5, in an implementation, the potentials of the lenses in the optical rail are adjusted to increase the extraction energy and pull ions passing therethrough through a relatively high pressure region, which results in collision- induced fragmentation of the ions. Other forms of fragmentation may also be applied to create the fragment ions, including electron induced dissociation, photo dissociation or the like. As earlier discussed, in an implementation, the fragmented ions are then mass analyzed with the same high performance characteristics of the non-fragmented, or native, ions. In an implementation, information associated with the fragmented ions and the native ions can be achieved by substantially rapidly switching the potentials (ion energy) in a manner that yields alternating parent and fragmentation channels and information associated therewith and the deconvolution in the Chromatof HRT, as described in US U.S. 7,501,621, U.S. 7,825,373, U.S. 7,884,319, which provides for the analysis of the fragment ions in the same manner as the native, non-fragmented or parent ions. In an implementation, the foregoing system provides an ability to acquire fragmentation information at up to 100 spectra/sec in each channel with de minimis loss of signal.

[0023] In an implementation, the multiplication of the two or more signals from the first and second channels in a high resolution mass spectrometer is performed to create a selective amplification of the signal for a specific analyte or group of analytes.

[0024] In an implementation, a non-MS/MS set of data channels are utilized (e.g., one not involving ion isolation). For example, a precursor ion signal may be multiplied by the signal generated by a fragment ion to create an amplified signal unique to analytes and time windows containing only those two signals.

[0025] In an implementation, the tolerance window (e.g. mass accuracy) for the signals may be sufficiently confined such that the inclusion of non-selective signal is minimized. In an implementation, a narrow mass window is used to achieve the selective nature of the process. After considering this disclosure, it may be realized that the ability to be selective can be lost when mass windows are used that are too large.

[0026] While the foregoing example perceives the use of signals and related information from separate channels (e.g., one from a precursor channel and one from a product ion channel) the invention should not be so limited thereto. But, it is to be appreciated that the operation of a mass spectrometer in a pulsed fashion (e.g., whereby energies and signal channels are switched rapidly) is most amenable to this type of operation.

[0027] An implementation of the detection and quantitation process is depicted mathematically below using two signals and is shown in connection with various examples in Figures 6 and 7. As will be appreciated after reviewing and understanding this disclosure, the invention should not be limited to first and second signals but can further be performed across multiple signals. This mathematical process may be logically extrapolated to more than two signals.

Derived Third Signal = (signal from (— ) (A) ± * (signal from (— ) B ± )

[0028] In an implementation,

(A)and ( )(fl) are related as fragments, precusors, adducts or isotopes for a signal analyte or a group of related analytes. In an implementation, the (—) values can (i) be identified from experimentation; (ii) derived from theoretical calculations; or (iii) pre-identified from prior work product. In an embodiment, the mass tolerance values (x) and (y) are millimass units (ppm) and should be sufficiently small to maintain selectivity and, upon understanding this disclosure and the available instruments, will be determined by the capabilities of the instrument. In an implementation, this mass window is used as a determining factor in the selectivity of the operation and of the resultant new signal.

[0029] In an implementation the following combinations for Signals (A) and (B) above are:

[0030] And, as described above, the foregoing table may be extended to beyond signals A and B to A, B, C, D and the like.

[0031] Among other things, some possible advantages of this operation are as follows: (i) an ability to quickly identify analytes of interest by the selective enhancement of signal associated uniquely with that analyte; (ii) an ability to selectively quantify an analyte in a non-linear response which can be calibrated and modeled; (iii) an ability to rapidly verify analyte identifications by leveraging the fragment ion associations with the precursor ion; and (iv) an ability to perform all of these manipulations using experimental data, theoretical calculations or prior data. [0032] Exemplary applications of the foregoing system and method will now be provided.

[0033] Figure 6 depicts the XIC for the molecular ion of THG using a 5 ppm window showing the S/N for that signal, according to an embodiment. The bottom trace illustrates the product of the signals from the parent ion of THG (5 ppm window) and a prominent fragment ion with the same 5 ppm window. This analysis shows that the selected analyte was present in urine extract and an enhanced XIC illustrates clear and selective increase in signal.

[0034] The sample at the left in Fig. 7 is an eXIC using 377.202(7 mDa) and 140.011 (11 mDa) to achieve end, one trace of which is BPI, according to an embodiment. The chart in the right is the sample on the left except that the scale is expanded to show the enhanced signal for the small peak at ca. 400 sec. Analytes are in methanol extracts from liver samples.

[0035] Various implementations of the systems and techniques described here can be realized in digital electronic circuitry, integrated circuitry, specially designed ASICs (application specific integrated circuits), computer hardware, firmware, software, and/or combinations thereof. These various implementations can include implementation in one or more computer programs that are executable and/or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device.

[0036] These computer programs (also known as programs, software, software applications or code) include machine instructions for a programmable processor, and can be implemented in a high-level procedural and/or object-oriented programming language, and/or in assembly/machine language. As used herein, the terms "machine-readable medium" and "computer-readable medium" refer to any computer program product, apparatus and/or device (e.g., magnetic discs, optical disks, memory, Programmable Logic Devices (PLDs)) used to provide machine instructions and/or data to a programmable processor, including a machine- readable medium that receives machine instructions as a machine-readable signal. The term "machine-readable signal" refers to any signal used to provide machine instructions and/or data to a programmable processor.

[0037] Implementations of the subject matter and the functional operations described in this specification can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Moreover, subject matter described in this specification can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer readable medium for execution by, or to control the operation of, data processing apparatus. The computer readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter affecting a machine-readable propagated signal, or a combination of one or more of them. The terms "data processing apparatus", "computing device" and "computing processor" encompass all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal that is generated to encode information for transmission to suitable receiver apparatus.

[0038] A computer program (also known as an application, program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

[0039] The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0040] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read only memory or a random access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. However, a computer need not have such devices. Moreover, a computer can be embedded in another device, e.g., a mobile telephone, a personal digital assistant (PDA), a mobile audio player, a Global Positioning System (GPS) receiver, to name just a few. Computer readable media suitable for storing computer program instructions and data include all forms of nonvolatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and CD ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

[0041] To provide for interaction with a user, one or more aspects of the disclosure can be implemented on a computer having a display device, e.g., a CRT (cathode ray tube), LCD (liquid crystal display) monitor, or touch screen for displaying information to the user and optionally a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input. In addition, a computer can interact with a user by sending documents to and receiving documents from a device that is used by the user; for example, by sending web pages to a web browser on a user's client device in response to requests received from the web browser.

[0042] One or more aspects of the disclosure can be implemented in a computing system that includes a backend component, e.g., as a data server, or that includes a middleware component, e.g., an application server, or that includes a frontend component, e.g., a client computer having a graphical user interface or a Web browser through which a user can interact with an implementation of the subject matter described in this specification, or any combination of one or more such backend, middleware, or frontend components. The components of the system can be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a local area network ("LAN") and a wide area network ("WAN"), an inter-network (e.g., the Internet), and peer-to- peer networks (e.g., ad hoc peer-to-peer networks).

[0043] The computing system can include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. In some implementations, a server transmits data (e.g., an HTML page) to a client device (e.g., for purposes of displaying data to and receiving user input from a user interacting with the client device). Data generated at the client device (e.g., a result of the user interaction) can be received from the client device at the server.

[0044] While this specification contains many specifics, these should not be construed as limitations on the scope of the disclosure or of what may be claimed, but rather as descriptions of features specific to particular implementations of the disclosure. Certain features that are described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

[0045] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multi-tasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

[0046] A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results.

Claims

analyzing the third signal to identify a peak that is indicative of the presence of an analyte.

19. A computer program product as set forth in claim 18, wherein the first signal includes information that is identified from experimentation.

20. A computer program product as set forth in claim 18, wherein the first signal includes information derived from theoretical calculations.

21. A computer program product as set forth in claim 18, wherein the first signal includes information pre-identified from prior work product.

22. A computer program product as set forth in claim 18, wherein the first signal and the second signal are associated with the mass-to-charge ratio of the fragment ions and the non- fragmented ions.

4423. A computer program product as set forth in claim 22, wherein the step for multiplying the first signal with the second signal to derive a third signal comprises the following equation, where x and y are millimass units

Derived Third Signal = B

2½ 24. A computer program product as set forth in claim 18, further comprising:

isolating at least some of the ions prior to fragmentation.

54 25. A computer program product as set forth in claim 18, wherein the fragmentation step is selected from the group consisting of: collision-induced dissociation, electron induced dissociation and photo dissociation.

13 CLAIMS

WHAT IS CLAIMED IS:

1. A method for detecting and identifying the presence of an analyte in a sample using a high resolution mass spectrometry system, the method comprising:

ionizing an analyte to yield ions;

passing the ions into the mass spectrometry system;

fragmenting a portion of the ions passed into the mass spectrometry system such that there are, or may be, both fragment ions and non-fragmented ions passing through the system; identifying a first signal associated with the fragment ions;

identifying a second signal associated with the non-fragmented ions;

multiplying the first signal with the second signal to derive a third signal; and

2. A method for detecting and identifying the presence of an analyte as set forth in claim 1, wherein the first signal is associated with precursor ions and the second (or greater) signal is associated with product ions.

3. A method for detecting and identifying the presence of an analyte as set forth in claim 1, wherein the first signal is associated with a first parent ion isotope and the second signal is associated with a second parent ion isotope.

4. A method for detecting and identifying the presence of an analyte as set forth in claim 1, wherein the first signal is associated with a first product ion and the second signal is associated with a second product ion.

5. A method for detecting and identifying the presence of an analyte as set forth in claim 1, wherein the first signal and the second signal are associated with the mass-to-charge ratio of the fragment ions and the non-fragmented ions.

10

6. A method for detecting and identifying the presence of an analyte as set forth in claim 5, wherein the step for multiplying the first signal with the second signal to derive a third signal comprises the following equation, where x and y are millimass units:

Derived Third Signal = [signal from (— ) ( (.A4)) ++ ** (ssiiggnnaall ffrroomm (— ) B ± )

7. A method for detecting and identifying the presence of an analyte as set forth in claim 1, further comprising:

isolating at least some of the ions prior to fragmentation.

8. A method for detecting and identifying the presence of an analyte as set forth in claim 1, wherein the fragmentation step is selected from the group consisting of: collision-induced dissociation, electron induced dissociation and photo dissociation.

9. A method for detecting and identifying the presence of an analyte in a sample using a high resolution mass spectrometry system, the method comprising:

identifying a first signal associated with one or more fragment ions;

identifying a second signal associated with one or more non-fragmented ions;

10. A method for detecting and identifying the presence of an analyte as set forth in claim 9, further comprising:

ionizing an analyte to yield ions;

passing the ions into the mass spectrometry system;

fragmenting a portion of the ions passed into the mass spectrometry system such that there may be both fragment ions and non-fragmented ions passing through the system.

11. A method for detecting and identifying the presence of an analyte as set forth in claim 9, further comprising:

isolating at least some of the ions prior to fragmentation.

11

12. A method for detecting and identifying the presence of an analyte as set forth in claim 10, wherein the fragmentation step is selected from the group consisting of: collision-induced dissociation, electron induced dissociation and photo dissociation.

13. A method for detecting and identifying the presence of an analyte as set forth in claim 9, wherein the first signal includes information that is identified from experimentation.

14. A method for detecting and identifying the presence of an analyte as set forth in claim 9, wherein the first signal includes information derived from theoretical calculations.

15. A method for detecting and identifying the presence of an analyte as set forth in claim 9, wherein the first signal includes information pre-identified from prior work product.

16. A method for detecting and identifying the presence of an analyte as set forth in claim 9, wherein the first signal and the second signal are associated with the mass-to-charge ratio of the fragment ions and the non-fragmented ions.

17. A method for detecting and identifying the presence of an analyte as set forth in claim 16, wherein the step for multiplying the first signal with the second signal to derive a third signal comprises the following equation, where x and are millimass units

Derived Third Signal = [Signal from B ± y

18. A computer program product encoded on a non-transitory computer readable storage medium comprising instructions that when executed by a data processing apparatus cause the data processing apparatus to perform operations of a method comprising:

ionizing an analyte to yield ions;

passing the ions into a mass spectrometry system;

fragmenting a portion of the ions passed into the mass spectrometry system such that there may be both fragment ions and non-fragmented ions passing through the system;

identifying a first signal associated with the fragment ions;

identifying a second signal associated with the non-fragmented ions;

12 analyzing the third signal to identify a peak that is indicative of the presence of an analyte.

19. A computer program product as set forth in claim 22, wherein the step for multiplying the first signal with the second signal to derive a third signal comprises the following equation, where x and y are millimass units

Derived Third Signal = [Signal from B ± y

23. A computer program product as set forth in claim 18, further comprising:

isolating at least some of the ions prior to fragmentation.

24. A computer program product as set forth in claim 18, wherein the fragmentation step is selected from the group consisting of: collision-induced dissociation, electron induced dissociation and photo dissociation.

13