Mass correction

Abstract

A method for mass spectrometry which includes the following steps: Providing a library of matrix data wherein the matrix data exhibit one or more physicochemical properties of one or more matrix components as a function of the chromatographic retention time, wherein the matrix components are endogenous compounds of a matrix, chromatographic separation of a sample, wherein the sample contains at least some of the matrix components and one or more analyte components, Using a mass spectrometer to analyze the sample at several chromatographic retention times to obtain sample data, wherein the sample data exhibit one or more physicochemical properties of a plurality of sample components as a function of the chromatographic retention time, Calculating one or more error values ​​as a function of the chromatographic retention time based on a comparison between the sample data and the matrix data, wherein the step of calculating one or more error values ​​comprises: determining the difference between a physicochemical property of the matrix components in the sample data and a corresponding physicochemical property of the matrix components in the matrix data at a given chromatographic retention time or in a given chromatographic retention time range, wherein the one or more error values ​​correspond to the determined difference, and wherein the one or more physicochemical properties include one or more of the following: mass / charge ratio, drift time, collision cross section (“CCS”), interaction cross section, ion mobility, and differential ion mobility.

Description

AREA OF INVENTION

[0001] The present invention relates generally to mass spectrometry and in particular to mass spectrometers and methods for mass spectrometry. BACKGROUND

[0002] Many analyses involve the analysis of small amounts of target analytes or unknown analytes in the presence of a known, well-defined complex matrix. Chromatographic techniques such as liquid chromatography (LC) and gas chromatography (GC) in conjunction with mass spectrometry are routinely used to separate the analyte from the matrix components.

[0003] Biological matrices include plasma, urine, feces, and bile. In other fields of application, many other common matrices exist, such as soil and various food types, for example, oranges, ginger, and apples, etc.

[0004] It is known to correct for mass-to-charge ratio drift in chromatography techniques. For example, continuous background ions, such as characteristic solvent ions (or ions escaping from the column in the case of gas chromatography), which generally have a low mass-to-charge ratio, are rare within the data, and do not change chromatographically during the chromatographic run, have been used to correct for mass-to-charge ratio drift.

[0005] Because there are relatively few continuous background ions, the probability of mass interference at points in the chromatogram due to matrix ions can be relatively high. This is also the case with internal reference compounds. Additionally, the statistical accuracy of these ions can reduce confidence in the mass assignment. In some cases, very high concentrations of matrix ions can suppress the signal from these background ions, making correction at certain points in the chromatogram impossible.

[0006] Reference is made to “Analysis of mycotoxins in barley using ultra high liquid chromatography high resolution mass spectrometry: comparison of efficiency and efficacy of different extraction procedures” by Josep Rubert et al., Talanta, Volume 99, pp. 712-719, July 20, 2012 (“Talanta”).

[0007] GB2383963 A discloses the correction of the time axis of local chromatographic data compared with stored reference data.

[0008] US2014 / 0260509 A1 discloses a method for calibrating a chromatography system.

[0009] Further relevant prior art is known from US 2014 / 0326871 A1, US 2011 / 0101215 A1, US 2014 / 0012515 A1, US 2014 / 0132607 A1, WO 2012 / 131620 A1, and WO 2006 / 110848 A2.

[0010] It is desirable to provide an improved method for mass analysis of a sample using chromatographic techniques. SUMMARY

[0011] The invention is defined in the attached independent claims. Advantageous embodiments are the subject of the dependent claims. Some further disclosed embodiments are not the subject of the present invention, but serve to facilitate understanding of the invention.

[0012] According to one aspect of the present disclosure, a method for mass spectrometry with the features of claim 1 is proposed.

[0013] This method improves error analysis by using the physicochemical properties of matrix components to calculate error values ​​as a function of retention time.

[0014] “Analysis of mycotoxins in barley using ultra-high liquid chromatography high-resolution mass spectrometry: comparison of efficiency and efficacy of different extraction procedures” by Josep Rubert et al., Talanta, Volume 99, pp. 712–719, July 20, 2012 (“Talanta”) describes a method in which a sample is separated by ultra-high-performance liquid chromatography and analyzed in an Orbitrap (RTM) mass spectrometer. Talanta does not disclose, nor does it suggest, the use of matrix components to generate error values ​​as a function of retention time.

[0015] GB2383963 A discloses a method for correcting local chromatographic data and does not disclose a method for mass spectrometry as described herein. Agilent further differs from the present disclosure in that it describes the generation of retention time correction functions based on calibration compounds. In contrast, the present disclosure uses matrix components to generate error values, wherein the matrix compounds may be contained in a sample that has analyte components dispersed in a matrix.

[0016] US2014 / 0260509 A1 describes the use of a standard solution for repeated calibration of a chromatography system and does not disclose or suggest the use of matrix components to generate error values ​​as described herein.

[0017] Several embodiments disclosed herein can enable the maintenance of mass accuracy without the introduction of additional internal or external barrier ions. Reference is made to "Matrix Effects—A Challenge Toward Automation of Molecular Analysis" (Journal of Laboratory Automation, 2010, 15:233). This can significantly simplify instrument operation and maximize the time available for analyte acquisition. One problem that arises with an external barrier is that its application can lead to gaps in the data where the barrier is introduced. For very fast chromatography, this can result in data loss.

[0018] Several samples can be provided, one of which may be the sample described above, and the several samples may share a common matrix (e.g., urea, soil, apples, etc.) such that the one or more physicochemical properties of the one or more matrix components are essentially the same for all samples. The steps of analyzing the sample and calculating one or more error values ​​can be repeated for additional samples taken from the multiple samples.

[0019] The one or more samples may contain analyte components dispersed in one or the common matrix.

[0020] In various embodiments, the mass-to-charge ratio values ​​of certain ions eluting from a chromatograph or chromatography system are optionally identified as common, known, or predetermined matrix ions. The identified common, known, or predetermined matrix ions can then be used to calculate error values ​​and / or to set a mass calibration as a function of retention time. The error values ​​and / or modified mass calibrations can then optionally be used to correct for mass-to-charge ratio drift during analysis or a subsequent experimental run. Instead of the mass-to-charge ratio, other physicochemical properties such as one or more of the drift time, collision cross-section (CCS), interaction cross-section, ion mobility, differential ion mobility, and retention time could be used.

[0021] References to "a function of the retention time" can be interpreted to mean that the proposed values ​​are given with an associated retention time or retention period. For example, an error value can be calculated for a period corresponding to a retention period, or it can be calculated for a single retention time value. The applied correction can refer to mass spectra generated within the retention period. Alternatively, the mass spectra within a retention period can be summed, and the correction can be applied to the summed mass spectrum.

[0022] The step of providing a matrix data library may include the following: chromatographic separation of a sample or matrix containing the matrix components, for example, in one or more initial chromatographic separations, and optionally, analysis of the sample or matrix at one or more retention times to obtain the matrix data. The initial chromatographic separation may be non-analytical and / or not part of an analytical run. The matrix data library step may be performed prior to the sample separation and analysis step to obtain the sample data.

[0023] The sample data can be obtained during one or more analysis runs.

[0024] The step of calculating one or more error values ​​involves determining the difference between a physicochemical property in the sample data and a corresponding physicochemical property in the matrix data at a specific retention time or within a specific retention time range. The physicochemical property can refer to the same matrix component. For example, the matrix can be urine, and the matrix component can be uric acid. The physicochemical property could be the mass-to-charge ratio of the uric acid.

[0025] The comparison can be a comparison of one or more physicochemical properties of one or more matrix components in the matrix data with the same physicochemical properties of the same matrix components in the sample data.

[0026] The matrix data can exhibit one or more physicochemical properties of several different matrix components as a function of retention time, and the step of calculating one or more error values ​​can involve calculating multiple error values ​​as a function of retention time, with each error value optionally relating to a different matrix component.

[0027] The matrix data can include one or more physicochemical properties of at least 2, 4, 8, 16, 32, 64 or 128 different matrix components as a function of the retention time, and the step of calculating one or more error values ​​can include calculating at least 2, 4, 8, 16, 32, 64 or 128 respective error values ​​as a function of the retention time, each error value optionally relating to a different matrix component.

[0028] The method, according to various embodiments, optionally further includes the calculation of one or more setting or correction values ​​based on one or more error values. The one or more setting or correction values ​​can be assigned to a respective retention time, a respective mass, a respective mass / charge ratio, or another physicochemical property.

[0029] The step of calculating one or more setting or correction values ​​may involve plotting or calculating multiple error values ​​as a function of the retention time and optionally determining the setting or correction values ​​based on the plot.

[0030] The step of calculating a setting or correction value may involve plotting or determining multiple error values ​​as a function of retention time and determining the setting or correction values ​​using an adjustment line in connection with plotting or determining error values ​​as a function of retention time.

[0031] Each error, setting or correction value can be recorded with a corresponding retention time and / or physicochemical property, for example the mass, mass / charge ratio, drift time, collision cross section (“CCS”), interaction cross section, ion mobility or differential ion mobility.

[0032] The method according to various embodiments may further include: adjusting or correcting mass spectrum data, for example, mass / charge ratio values, in relation to the sample using one or more adjustment or correction values. Adjusting or correcting mass spectrum data may include: identifying a mass spectrum at a given retention time, calculating an adjustment or correction value at the retention time as described above, and applying this adjustment or correction value to the mass spectra. The adjustment or correction value may include a ppm error or correspond to a shift value for the spectrum.

[0033] It should be noted that the adjustment or correction of mass spectrum data or mass / charge ratio values ​​differs from prior art methods that correct or adjust retention times. The error, adjustment, or correction values ​​can be calculated by: identifying, for a given retention time, one or more mass / charge ratio peaks in the sample data that correspond to matrix peaks, and comparing the respective values ​​associated with these peaks (e.g., intensity, mass / charge ratio) with the values ​​stored in the library for these specific matrix peaks, and calculating the error, adjustment, or correction value based on the difference between the sample and library values.Typically, a number of matrix peaks are identified for a given retention time or retention period, and the error, setting, or correction value for a given retention time or retention period can be calculated using multiple matrix peaks (for example, at least 2, 4, 8, 16, 32, 64, or 128), where, for example, an average value could be used.

[0034] The method according to various embodiments may further include the setting or correction of one or more instrument parameters using the setting or correction value.

[0035] One or more instrument parameters may include one or more of the detector gain, transmission efficiency, ionization efficiency, time-of-flight voltage, and reflectron voltage.

[0036] The adjustment or correction step can be performed in real time or as a post-processing technique.

[0037] The error values ​​can be used to modify or improve a calibration or calibration model. For example, the difference between the physicochemical properties of the matrix component in the sample data and the physicochemical properties of the matrix component in the matrix data can be used to modify or change a calibration or calibration model. The calibration model can be modified as a function of the retention time; that is, the modification or change can be applied to the calibration or calibration model as a function of the retention time. The calibration or calibration model can be changed at each retention time or retention period.

[0038] Any of the physicochemical properties described here can exhibit one or more of the following characteristics: mass, mass / charge ratio, drift time, collision cross-section (“CCS”), interaction cross-section, ion mobility, differential ion mobility, and retention time.

[0039] Any of the physicochemical properties described here can be or include intensity or frequency.

[0040] Furthermore, one or more matrix components can be determined using this method. The step of determining one or more matrix components can be performed separately from the step of chromatographic separation and analysis of the sample, for example, before or after.

[0041] The error value and / or multiple error values ​​and / or setting or correction values ​​can be used to correct mass spectrum data with respect to the analyte components. The known or determined matrix components can be used as a barrier mass for the analyte components.

[0042] The sample can be analyzed using a mass spectrometer, and the procedure may further involve introducing a reference or barrier mass component into the mass spectrometer during an experiment if one or more error values ​​exceed a defined limit. The reference may be an internal or external standard. The reference or barrier mass may be introduced into the mass spectrometer with the sample or separately. The reference or barrier mass component may interrupt the flow or introduction of the sample into the mass spectrometer.

[0043] The procedure may also involve the introduction of a reference or barrier mass component into the mass spectrometer during an experiment if one or more error values ​​exceed a predetermined limit.

[0044] The method may further include mixing the matrix components and the analyte components to form the sample prior to mixing the sample with a solvent. The method may further include mixing the matrix components and the analyte components to form the sample prior to separating the sample.

[0045] According to another aspect of the present disclosure, a mass spectrometer with the features of claim 13 is proposed.

[0046] Furthermore, a method for mass spectrometry is revealed, which comprises the following steps: Providing a library of matrix data wherein the matrix data exhibit one or more physicochemical properties of one or more matrix components, Imaging a sample at multiple spatial locations, wherein the sample contains at least some of the matrix components and one or more analyte components, Analyzing the sample at multiple spatial locations to obtain sample data, wherein the sample data exhibit one or more physicochemical properties of one or more sample components, Calculating one or more error values ​​based on a comparison between the sample data and the matrix data, where each error value is assigned to a given spatial location.

[0047] The comparison can be a comparison of one or more physicochemical properties of one or more matrix components in the matrix data with the same physicochemical properties of the same matrix components in the sample data.

[0048] Furthermore, a mass spectrometer has been revealed which exhibits the following: a control system that is set up and designed to perform the following: Providing a library of matrix data, wherein the matrix data exhibit one or more physicochemical properties of one or more matrix components, the mass spectrometer further comprising: an ion imaging system that is set up and designed to perform the following: Imaging a sample at multiple spatial locations, wherein the sample contains at least some of the matrix components and one or more analyte components, and Analyzing the sample at one or more spatial locations to obtain sample data, wherein the sample data exhibit one or more physicochemical properties of one or more sample components, wherein the control system is further configured and designed to perform the following: Calculating one or more error values ​​based on a comparison between the sample data and the matrix data, where each error value is assigned to a given spatial location.

[0049] Furthermore, a method for mass spectrometry is disclosed, which has the following features: chromatographic separation of a sample containing a mixture of analyte and matrix compounds, Record at least one of the mass, mass / charge ratio, ion mobility, and drift time data during the chromatographic elution time. Processing the data to determine at least one of the mass, mass / charge ratio, ion mobility, and drift time properties of each ion species, and Identifying one or more ion species at one or more different retention times and / or at one or more mass / charge ratios by comparison with a library of ion species in relation to the properties, wherein the ion species in the library are limited to those matrix ions that are known to be in the mixture or are very likely to be in the mixture, and the identified ion species originate from a chromatographic elution of at least some of the compounds within the mixture, the procedure further includes the following: Determine at least one of the mass, mass / charge ratio, ion mobility, and drift time errors between the identified species and the library values. Calculate at least one of a mass, mass / charge ratio, ion mobility, and drift time correction value as a function of the retention time or retention time range and Setting at least one mass, mass / charge ratio, ion mobility and drift time calibration as a function of the retention time or retention time range for the ion species in the data based on the function.

[0050] The spectrometer may include an ion source selected from the group consisting of: (i) an electrospray ionization (“ESI”) ion source, (ii) an atmospheric pressure photoionization (“APPI”) ion source, (iii) an atmospheric pressure chemical ionization (“APCI”) ion source, (iv) a matrix-assisted laser desorption ionization (“MALDI”) ion source, (v) a laser desorption ionization (“LDI”) ion source, (vi) an atmospheric pressure ionization (“API”) ion source, (vii) a desorption ionization on silicon (“DIOS”) ion source, (viii) an electron impact (“El”) ion source, (ix) a chemical ionization (“Cl”) ion source, (x) a field ionization (“Fl”) ion source. (xi) a field desorption (“FD”) ion source, (xii) an inductively coupled plasma (“ICP”) ion source, (xiii) a fast atom bombardment (“FAB”) ion source, (xiv) a liquid secondary ion mass spectrometry (“LSIMS”) ion source,(xv) a desorption electrospray ionization (“DESI”) ion source, (xvi) a radioactive nickel-63 ion source, (xvii) an atmospheric pressure matrix-assisted laser desorption ionization ion source, (xviii) a thermospray ion source, (xix) an atmospheric sampling glow discharge ionization (“ASGDI”) ion source, (xx) a glow discharge (“GD”) ion source, (xxi) an impactor ion source, (xxii) a direct analysis in real time (“DART”) ion source, (xxii) a laser spray ionization (“LSI”) ion source, (xxiv) a sonic spray ionization (“SSI”) ion source, (xxv) a matrix-assisted Intake ionization (“MAII”) ion source, (xxvi) a solvent-assisted intake ionization (“SAII”) ion source, (xxvii) a desorption electrospray ionization (“DESI”) ion source,(xxviii) a laser ablation electrospray ionization (“LAESI”) ion source and (xxix) a surface-assisted laser desorption ionization (“SALDI”) ion source.

[0051] The spectrometer can have one or more continuous or pulsed ion sources.

[0052] The spectrometer can have one or more ion guides.

[0053] The spectrometer may include one or more ion mobility separation devices and / or one or more field asymmetric ion mobility spectrometer devices.

[0054] The spectrometer can have one or more ion traps or one or more ion confinement regions.

[0055] The spectrometer may include one or more collision, fragmentation, or reaction cells selected from the group consisting of: (i) a collision-induced dissociation (“CID”) fragmentation device, (ii) a surface-induced dissociation (“SID”) fragmentation device, (iii) an electron transfer dissociation (“ETD”) fragmentation device, (iv) an electron capture dissociation (“ECD”) fragmentation device, (v) an electron impact or collision dissociation fragmentation device, (vi) a photo-induced dissociation (“PlD”) fragmentation device, (vii) a laser-induced dissociation fragmentation device, (viii) an infrared radiation-induced dissociation device, (ix) a Ultraviolet radiation-induced dissociation device, (x) a nozzle-skimmer interface fragmentation device, (xi) an in-source fragmentation device,(xii) an in-source impact-induced dissociation fragmentation device, (xiii) a thermal or temperature source fragmentation device, (xiv) an electric field-induced fragmentation device, (xv) a magnetic field-induced fragmentation device, (xvi) an enzyme digestion or enzyme degradation fragmentation device, (xvii) an ion-ion reaction fragmentation device, (xviii) an ion-molecule reaction fragmentation device, (xix) an ion-atom reaction fragmentation device, (xx) an ion-metastable ion reaction fragmentation device, (xxi) an ion-metastable molecule reaction fragmentation device, (xxii) an ion-metastable atom reaction fragmentation device, (xxiii) an ion-ion reaction device for reacting ions to form adducts or productions, (xxiv) an ion-molecule reaction device for reacting ions to form adducts or productions,(xxv) an ion-atom reaction device for reacting ions to form adducts or productions, (xxvi) an ion-metastable ion reaction device for reacting ions to form adducts or productions, (xxvii) an ion-metastable molecule reaction device for reacting ions to form adducts or productions, (xxviii) an ion-metastable atom reaction device for reacting ions to form adducts or productions, and (xxix) an electron ionization dissociation ("EID") fragmentation device.

[0056] The spectrometer may include a mass analyzer selected from the group consisting of: (i) a quadrupole mass analyzer, (ii) a two-dimensional or linear quadrupole mass analyzer, (iii) a Paul or three-dimensional quadrupole mass analyzer, (iv) a Penning trap mass analyzer, (v) an ion trap mass analyzer, (vi) a magnetic sector mass analyzer, (vii) an ion cyclotron resonance (ICR) mass analyzer, (viii) a Fourier transform ion cyclotron resonance (FTICR) mass analyzer, (ix) an electrostatic mass analyzer configured to generate an electrostatic field with a quadrologarithmic potential distribution, (x) an electrostatic Fourier transform mass analyzer, (xi) a Fourier transform mass analyzer, (xii) a time-of-flight mass analyzer,(xiii) an orthogonal acceleration time-of-flight mass analyzer and (xiv) a linear acceleration time-of-flight mass analyzer.

[0057] The spectrometer can have one or more energy analyzers or electrostatic energy analyzers.

[0058] The spectrometer can have one or more ion detectors.

[0059] The spectrometer may include one or more mass filters selected from the group consisting of: (i) a quadrupole mass filter, (ii) a two-dimensional or linear quadrupole ion trap, (iii) a Paul or three-dimensional quadrupole ion trap, (iv) a Penning ion trap, (v) an ion trap, (vi) a magnetic sector mass filter, (vii) a time-of-flight mass filter, and (viii) a Wien filter.

[0060] The spectrometer may include a device or ion gate for pulsing ions and / or a device for converting an essentially continuous ion beam into a pulsed ion beam.

[0061] The spectrometer can have a C-trap and a mass analyzer with an outer tubular electrode and a coaxial inner spindle-shaped electrode forming an electrostatic field with a quadrologarithmic potential distribution, wherein in a first operating mode ions are transferred to the C-trap and then injected into the mass analyzer, and wherein in a second operating mode ions are transferred to the C-trap and then transferred to a collision cell or electron transfer dissociation device where at least some ions are fragmented into fragment ions, and wherein the fragment ions are then transferred to the C-trap before being injected into the mass analyzer.

[0062] The spectrometer can have a ring-stack ion guide with multiple electrodes, each having an opening through which ions are allowed to pass during use, wherein the distance between the electrodes increases along the ion path, and wherein the openings in the electrodes in an upstream section of the ion guide have a first diameter, and wherein the openings in the electrodes in a downstream section of the ion guide have a second diameter that is smaller than the first diameter, and wherein opposite phases of an alternating or RF voltage are applied to successive electrodes during use.

[0063] The spectrometer may include a device that is set up and designed to supply an alternating or RF voltage to the electrodes. The AC or RF voltage optionally has an amplitude selected from the following group: (i) approximately < 50 V peak-to-peak, (ii) approximately 50–100 V peak-to-peak, (iii) approximately 100–150 V peak-to-peak, (iv) approximately 150–200 V peak-to-peak, (v) approximately 200–250 V peak-to-peak, (vi) approximately 250–300 V peak-to-peak, (vii) approximately 300–350 V peak-to-peak, (viii) approximately 350–400 V peak-to-peak, (ix) approximately 400–450 V peak-to-peak, (x) approximately 450–500 V peak-to-peak and (xi) approximately > 500 V peak-to-peak.

[0064] The alternating or RF voltage can have a frequency selected from the following group: (i) < about 100 kHz, (ii) about 100–200 kHz, (iii) about 200–300 kHz, (iv) about 300–400 kHz, (v) about 400–500 kHz, (vi) about 0.5–1.0 MHz, (vii) about 1.0–1.5 MHz, (viii) about 1.5–2.0 MHz, (ix) about 2.0–2.5 MHz, (x) about 2.5–3.0 MHz, (xi) about 3.0–3.5 MHz, (xii) about 3.5–4.0 MHz, (xiii) about 4.0–4.5 MHz, (xiv) about 4.5–5.0 MHz, (xv) approximately 5.0 - 5.5 MHz, (xvi) approximately 5.5 - 6.0 MHz, (xvii) approximately 6.0 - 6.5 MHz, (xviii) approximately 6.5 - 7.0 MHz, (xix) approximately 7.0 - 7.5 MHz, (xx) approximately 7.5 - 8.0 MHz, (xxi) approximately 8.0 - 8.5 MHz, (xxii) approximately 8.5 - 9.0 MHz, (xxiii) approximately 9.0 - 9.5 MHz, (xxiv) approximately 9.5 - 10.0 MHz and (xxv) > approximately 10.0 MHz.

[0065] The spectrometer may include a chromatography or other separation device upstream of an ion source. The chromatography separation device may be a liquid chromatography or gas chromatography device. Alternatively, the separation device may include: (i) a capillary electrophoresis ("CE") separation device, (ii) a capillary electrochromatography ("CEC") separation device, (iii) a separation device with an essentially rigid ceramic-based multilayer microfluidic substrate ("ceramic tile"), or (iv) a supercritical fluid chromatography separation device.

[0066] The ion guidance can be maintained at a pressure selected from the group consisting of the following: (i) < about 0.0001 mbar, (ii) about 0.0001 - 0.001 mbar, (iii) about 0.001 - 0.01 mbar, (iv) about 0.01 - 0.1 mbar, (v) about 0.1 - 1 mbar, (vi) about 1 - 10 mbar, (vii) about 10 - 100 mbar, (viii) about 100 - 1000 mbar and (ix) > about 1000 mbar.

[0067] Analyte ions can be subjected to electron transfer dissociation (ETD) fragmentation in an electron transfer dissociation fragmentation device. Analyte ions can be caused to interact with ETD reagents within an ion guide or fragmentation device.

[0068] Optionally, to effect electron transfer dissociation, either: (a) analyte ions are fragmented or dissociated to form product or fragment ions after interacting with reagent ions, and / or (b) electrons are transferred from one or more reagent anions or negatively charged ions to one or more multiply charged analyte cations or positively charged ions, whereupon at least some of the multiply charged analyte cations or positively charged ions are dissociated to form product or fragment ions, and / or (c) analyte ions are fragmented or dissociated to form product or fragment ions after interacting with neutral reagent gas molecules or atoms or a non-ionic reagent gas.and / or (d) electrons are transferred from one or more neutral non-ionic or uncharged starting gases or vapors to one or more multiply charged analyte cations or positively charged ions, whereupon at least some of the multiply charged analyte cations or positively charged ions are caused to dissociate and form product or fragment ions, and / or (e) electrons are transferred from one or more neutral non-ionic or uncharged superbase reagent gases or vapors to one or more multiply charged analyte cations or positively charged ions, whereupon at least some of the multiply charged analyte cations or positively charged ions are caused to dissociate and form product or fragment ions, and / or (f) electrons are transferred from one or more neutral,(a) electrons are transferred from one or more non-ionic or uncharged alkali metal gases or vapors to one or more multiply charged analyte cations or positively charged ions, whereupon at least some of the multiply charged analyte cations or positively charged ions are caused to dissociate and form product or fragment ions, and / or (g) electrons are transferred from one or more neutral, non-ionic or uncharged gases, vapors or atoms to one or more multiply charged analyte cations or positively charged ions, whereupon at least some of the multiply charged analyte cations or positively charged ions are caused to dissociate and form product or fragment ions, wherein the one or more neutral, non-ionic or uncharged gases, vapors or atoms are selected from the group consisting of: (i) sodium vapor or atoms, (ii) lithium vapor or atoms, (iii) potassium vapor or atoms,(iv) rubidium vapor or atoms, (v) cesium vapor or atoms, (vi) francium vapor or atoms, (vii) C, 60 -vapor or atoms and (viii) magnesium vapor or atoms.

[0069] The multiply charged analyte cations or positively charged ions can include peptides, polypeptides, proteins, or biomolecules.

[0070] Optionally, to effect electron transfer dissociation: (a) the reagent anions or negatively charged ions are derived from a polyaromatic hydrocarbon or a substituted polyaromatic hydrocarbon and / or (b) the reagent anions or negatively charged ions are derived from the group consisting of: (i) anthracene, (ii) 9,10-diphenylanthracene, (iii) naphthalene, (iv) fluorine, (v) phenanthrene, (vi) pyrene, (vii) fluoranthene, (viii) chrysene, (ix) triphenylene, (x) perylene, (xi) acridine, (xii) 2,2'-dipyridyl, (xiii) 2,2'-biquinoline, (xiv) 9-anthracenecarbonitrile, (xv) dibenzothiophene, (xvi) 1,10'-phenanthroline, (xvii) 9'-Anthracene carbonitrile and (xviii) anthraquinone and / or (c) contain the reagents or negatively charged ions azobenzene anions or azobenzene radical anions.

[0071] The process of electron transfer dissociation fragmentation can involve the interaction of analyte ions with reagents, where the reagents include dicyanobenzene, 4-nitrotoluene, or azulene.

[0072] A chromatography detector can be provided, wherein the chromatography detector has the following features: a destructive chromatography detector, optionally selected from the group consisting of: (i) a flame ionization detector (“FID”), (ii) an aerosol-based detector or a nanoquantity analyte detector (“NQAD”), (iii) a flame photometry detector (“FPD”), (iv) an atomic emission detector (“AED”), (v) a nitrogen phosphorus detector (“NPD”) and (vi) an evaporative light scattering detector (“ELSD”), or a non-destructive chromatography detector, optionally selected from the group consisting of: (i) a fixed or variable wavelength UV detector, (ii) a thermal conductivity detector (TCD), (iii) a fluorescence detector, (iv) an electron capture detector (ECD), (v) a conductivity monitoring device, (vi) a photoionization detector (PID), (vii) a refractive index detector (RID), (viii) a radio flow detector, and (ix) a chiral detector.

[0073] The spectrometer can be operated in various operating modes, including a mass spectrometry (“MS”) mode, a tandem mass spectrometry (“MS / MS”) mode, an operating mode in which starting or precursor ions are alternatively fragmented or reacted to produce fragments or productions, and are not fragmented or reacted or are fragmented or reacted to a lesser extent, a multiple reaction monitoring (“MRM”) mode, a data-dependent analysis (“DDA”) mode, a data-independent analysis (“DIA”) mode, a quantification mode, or an ion mobility spectrometry (“IMS”) mode. BRIEF DESCRIPTION OF THE DRAWING

[0074] Various embodiments of the present disclosure are now described only as examples with reference to the accompanying drawing. The drawing shows: Fig. 1 a chromatogram of a sample of human urine and Fig. 2. A graph of an error as a function of retention time. DETAILED DESCRIPTION

[0075] A method for mass spectrometry is presented that can begin with the step of providing a library of matrix data. The matrix data comprises one or more physicochemical properties of one or more matrix components as a function of retention time in the form of mass / charge ratios of a number of matrix tips. A sample, which can be taken from a number of samples of the same origin (for example, urine samples from several individuals, soil samples from a specific area), is separated chromatographically. The sample contains at least some of the matrix components and one or more analyte components. For example, the sample may consist of urine, and the one or more matrix components may be urea, uric acid, etc., while the one or more analyte components may be traces of certain drugs.

[0076] The sample is analyzed at multiple retention times to obtain sample data, which includes one or more physicochemical properties of one or more sample components as a function of the retention time. The sample components may include or correspond to one or more matrix components, which may, for example, be the same matrix components used to provide the library of matrix data.

[0077] One or more error values ​​can be calculated as a function of retention time based on a comparison between the sample data and the matrix data. This comparison involves comparing a physicochemical property of one or more matrix components in the sample data with the corresponding physicochemical property of the same matrix components in the matrix data at one or more retention times. The one or more error values ​​can then correspond to the difference between the physicochemical property of the matrix component in the sample data and the physicochemical property of the matrix component in the matrix data at one or more retention times.

[0078] Matrix components or compounds can be defined as the components of a mixture different from one or more analytes. For a given sample origin, the presence of common or known matrix ions can be highly predictable. The matrix can be a biological matrix, such as plasma, urine, feces, or bile.

[0079] A matrix may be known prior to the start of the analysis, and in many cases, matrix-matched standards have been prepared. A matrix, such as plasma, urine, feces, bile, soil, or a specific foodstuff, may contain many endogenous compounds that, over the retention time range in which analytes of interest elute, give rise to many highly reproducible chromatographic peaks. The composition of each matrix type is essentially constant regardless of the sample's origin. Various designs exploit this by using the matrix's endogenous compounds, which elute at different retention times during a single analytical run, to correct errors in a sample containing these compounds as a function of retention time.

[0080] It should be noted that the composition of the matrix may be known in advance, in the sense that it has a standard chromatographic elution profile that can be provided with reference to a known library.

[0081] However, the library of matrix data, including the physicochemical properties of the matrix components, can alternatively be provided by chromatographic separation of a sample containing the matrix components in an initial pass prior to the analytical pass of the sample, in order to determine the physicochemical properties of the matrix components as a function of the retention time.

[0082] In this way, it is not necessary for the matrix itself or the matrix components to be identifiable, as long as the library of matrix data exhibits physicochemical properties as a function of retention time. For example, the matrix and / or the matrix components may be unknown during the analysis. What is important is how the physicochemical property of the matrix (whatever it may be) changes during the analysis run, because this is what is used to calculate the error values.

[0083] The approach, according to various embodiments, optionally also eliminates the need for an internal or external locking mass or an ion mobility locking drift, and optionally also reduces experimental and instrumental complexity.

[0084] Fig. Figure 1 shows a basic peak chromatogram of a human urine sample obtained by liquid chromatography-time mass spectrometry. The chromatogram is dominated by many intense peaks, each resulting in a mass spectra at every retention time. Many of these peaks relate to matrix ions and are of little or no analytical interest.

[0085] These matrix ions may be present in samples from different species or individuals at different concentrations; however, a sufficiently high proportion or a sufficiently large subset of these components is present in every urine sample at a sufficient concentration to be considered characteristic of that matrix.

[0086] It should be noted that it may not be necessary to fully characterize these matrix ions with respect to elucidating the elemental composition, the exact mass, etc., in order to use these matrix ions to perform an internal calibration of all mass spectrum peaks during analysis.

[0087] First, multiple samples can be provided, and the chromatographic profile and / or mass, mass-to-charge ratio, or ion mobility spectra of the multiple samples can be recorded in an initial or non-analytical run. The system may have been calibrated with reference standards prior to analysis. The samples may comprise analyte components of interest dispersed in a matrix, which may be common to all samples and may contain endogenous matrix components or compounds.

[0088] For example, the samples could be multiple urine samples. Among other things, the common endogenous compounds found in a urine matrix can include urea, creatinine, uric acid, citrate, host / pathogenic DNA, host / pathogenic RNA, amino acids, immunoglobulin, Tamm-Horsfall protein, albumin, and many other compounds. These compounds can be common to all samples and exhibit the same physicochemical properties regardless of the specific sample taken.

[0089] Alternatively, samples can be taken from one or more apples, where the matrix in this case would be, for example, endogenous sugars in the apple, and the method can include the detection of levels of a specific analyte, such as a pesticide. The samples can all contain common endogenous matrix components that exhibit the same physicochemical properties, regardless of the specific sample taken. These could be used as matrix components of the method disclosed herein.

[0090] Secondly, the data can be processed to generate a library of components, and a determination can be made regarding which components of the matrix are common, regardless of their origin. A library of mass, mass-to-charge ratio, ion mobility, differential ion mobility, drift time, collision cross-section (CCS), interaction cross-section, and / or retention time can be created for the matrix components.

[0091] A two-dimensional tip detection algorithm such as APEX3D or -4D can be used to reduce each chromatographic feature to mass, mass / charge ratio, ion mobility, drift time, collision cross section (“CCS”), interaction cross section and / or retention time.

[0092] A sample can undergo multiple passes, or different samples can be subjected to passes and analyzed to improve confidence in the library entries for the matrix components.

[0093] Certain samples may be well-known, and the first and second steps provided above may not be necessary. For example, a library of matrix data exhibiting one or more physicochemical properties of one or more matrix components as a function of retention time may be provided with reference to a known database.

[0094] Alternatively, for matrix tips with an unknown composition, the expected physicochemical property values ​​in connection with the library can initially be determined using conventional internal or external barrier mass approaches known in the field.

[0095] The expected mass-to-charge ratio values ​​for matrix peaks with a known elemental composition can be calculated directly. Similarly, if the ion mobility, collision cross-section (CCS), or interaction cross-section value for a matrix ion is known, it can be directly recorded in the library. Alternatively, internal or external barrier mobility approaches can be used to ensure accurate library entries.

[0096] Care must be taken to avoid mass peaks that exhibit mass interference or are statistically inaccurate. The presence of potential interference can be investigated, for example, by comparing the peak shape or width to a model peak shape, expected peak shape, model peak width, or expected peak width. If a peak contains interference, it can be rejected and not added to the library.

[0097] The statistical accuracy of the mass and / or mobility measurement can be recorded with each measurement and optionally used to weight the contribution of certain signals to the final applied calibration.

[0098] Third, further samples can then be analyzed in subsequent or analytical runs. The data are optionally post-processed to locate and record the physicochemical properties (e.g., mass-to-charge ratio values) of the matrix peaks in the library, which can then be compared with corresponding matrix peaks in the subsequent or analytical samples. Optionally, as many matrix peaks as possible should be located. Signals that are very weak or exhibit mass interference are optionally avoided. Not all peaks in the library can be located or used for a specific analysis. Peaks can be located using one or more of the following parameters: mass, mass-to-charge ratio, ion mobility, differential ion mobility, drift time, collision cross-section (CCS), interaction cross-section, or retention time.

[0099] Fourthly, one or more error values ​​can be calculated as a function of the retention time based on a comparison between the physicochemical properties of one or more matrix components in the sample data with the corresponding physicochemical properties of the same matrix components in the matrix data at one or more retention times.

[0100] For example, a graph can be generated or otherwise calculated that plots (or calculates) error values, such as mass or mass / charge ratio error values ​​as a function of the retention time for the matrix ions in one or more of the mass spectra generated in subsequent or analysis passes. In the case of ion mobility spectrometry, the error values ​​might be, for example, a percentage error of the collision cross-section. Most spectra contain at least one matrix ion that is matched to the library. The errors calculated for each matched peak at each retention time can be averaged to a single value and assigned to a suitable statistical error or processed separately.

[0101] Fifth, an error function can be generated from the error values ​​as a function of the retention time. For example, a fitted curve can be plotted on the graph or otherwise computed, or a function corresponding to a fitted curve can be calculated. Outliers can be ignored, and statistical accuracy can be taken into account. The maximum curvature can be limited based on the gradual short-term drift expected by the system. Methods for determining a best fit to such data and for detecting outliers are known.

[0102] It should be noted that the error values ​​plotted as a function of retention time are due to the fact that retention time is the timescale of chromatographic separation.

[0103] Fig.Figure 2 shows a representation of a fit curve 1 for a defect plot as a function of retention time. The shown fit curve 1 represents the mass-to-charge ratio error in parts per million (ppm) of the peaks in the sample, which correspond to entries in the library, as a function of retention time. Fit curve 1 may be a best-fit curve.

[0104] Three outliers 2 are shown, which were determined not to fit the data trend and were therefore excluded from the calculation of the fitted line 1. The outliers 2 may fall outside the general trend line due to interference or mass assignment. The curve shape optionally represents the way in which the mass assignment drifted during the experimental retention time. This is known as mass / charge ratio drift and can occur, for example, as a result of ambient temperature changes during the experimental time. For a given system, the maximum rate of change of the mass / charge ratio, and thus the maximum curvature of this line, may be known or calculated. This can be used to constrain the curve and can serve as a basis for outlier suppression.

[0105] By fitting a smooth curve across all data, inherent statistical variations can be smoothed out, and the expected behavior of the system can be closely modeled. This can also allow for the correction of region 3 of the chromatogram, where few or no matrix ions match the library, for example, based on the general trends observed before or after these regions.

[0106] Alternatively, each spectrum or an averaged area of ​​spectra can be corrected independently. Other error processing methods (e.g., ppm) against time data can be used, such as calculating a moving average of the error over time.

[0107] Sixth, the mass / charge ratio of one or more analyte tips at their respective retention times can be corrected based on the error function, for example by using the best fit line to calculate an error value in the analyte tip retention time.

[0108] If MS E For planned or data-driven MS-MS experiments, the library can contain precursor and fragment ions from the matrix. This increases the number of peaks at each retention time that can be used for mass correction and improves the confidence in assigning matrix ions in the sample to the entries in the library. Correction values ​​calculated from the MS and MS-MS data at each retention time can be aggregated or averaged to improve accuracy.

[0109] According to another embodiment, a correction during chromatographic elution can be calculated and applied in real time, optionally based on identified matrix peaks. For example, a real-time correction of a current spectrum can use a moving average of correction values, optionally calculated from identified matrix ions in a number of previously acquired spectra.

[0110] Other instrument parameters can be monitored (for example, mass resolution) to monitor instrument operation, apply real-time correction, or adjust settings.

[0111] By using real-time monitoring of matrix ion mass-to-charge ratio values, mass shifts caused by detector saturation in time-of-flight mass spectrometers, space charge aberrations in analytical RF or electrostatic ion traps, or drift time shifts in ion mobility spectrometers or separation devices can be identified. This information can be used in real time to adjust instrument parameters, such as one or more of the ion transmission, ionization efficiency, detector gain, or ion trap fill time, to compensate for these effects.

[0112] Alternatively, this information can be used during post-processing to determine a correction to be applied to an analyte signal to compensate for shifts or other aberrations, for example, due to space charge effects at a given retention time.

[0113] Mobility can be recorded, and the disclosed methods can be used to correct mobility drift or locking drift. The collision cross section (CCS), interaction cross section, or drift time can be used to confirm the identity of a matrix tip, thus improving library allocation.

[0114] In proteomics, it may be known that many samples contain commonly found proteins, such as keratin or ubiquitin. Peptides of these proteins can be used to correct for drift during separation. In proteomics, the database can be a protein / peptide database containing precursor and fragment ions.

[0115] According to embodiments, a known matrix or calibration compound can be added to an analyte sample, forming a peak within it or being introduced in any other way, such that known chromatographic peaks with known mass-to-charge ratios appear within the final data. The added matrix or calibration mixture can be designed to elute at a time other than the analyte of interest and therefore cannot cause ionization suppression effects, interference, or mass interference. Additionally, the added matrix or calibration compound can be designed to separate from the analyte during the mass-to-charge ratio or drift period, optionally reducing the possibility of mass interference.

[0116] For example, when protein digestions are analyzed, a known digestion of a protein or another type of compound mixture in the sample can form a spike to act as a barrier mass during the chromatographic elution of the analyte peptides.

[0117] When quantifying small molecules, C13-labeled isotopes of the analyte are frequently used as internal quantification standards. These have the same retention time as the analyte but a different known mass-to-charge ratio. They can be used to correct for mass drift during chromatographic elution.

[0118] A multi-point blocking mass can also be generated. In this case, a blocking mass correction above the first order can be applied. This can be used to correct time drift in electronic timing circuits in time-of-flight systems. In the limiting case, a mass calibration curve can be generated for each retention time or retention time range, optionally using the described method applied to the data.

[0119] According to one embodiment, the method can be used in combination with a standard internal or external locking mass, for example as a quality control check to ensure that the instrument calibration and / or the locking mass is correct.

[0120] Alternatively, the method can be used in combination with an external barrier mass, allowing the drift in the matrix ion mass / charge ratio to be monitored and used for internal correction, and optionally to determine when to introduce an external barrier mass during the chromatography run. For example, a correction of up to 5 ppm can be achieved using the described method. Once it is determined that the drift is outside this value, an external barrier mass correction can be performed. This can minimize the number of external barrier mass events and allow the frequency of barrier mass introduction to be adjusted to the ambient conditions, optionally by the measured drift in the matrix ion mass / charge ratio.

[0121] Various embodiments can also eliminate the requirement for an internal or external locking mass or ion mobility locking drift, thereby reducing experimental and instrumental complexity.

[0122] The method can be applied to ion imaging, for example matrix-assisted laser desorption / ionization (“MALDI”) or desorption electrospray ionization (“DESI”) tissue imaging, optionally using an orthogonal acceleration time-of-flight instrument.

[0123] In many imaging experiments, such as MALDI or DESI imaging, the origin of the sample to be imaged may be well known. For example, the sample may be liver, muscle, or other tissue from a known species. A library can be generated containing one or more physicochemical properties of matrix components, where the matrix components correspond to common, reproducible compounds found in the sample.

[0124] Many matrix compounds or components can be found, and these compounds or components may be essentially common across specific areas of the surface or across the entire surface of a given sample. These compounds or components can be used to form an accurate library of matrix data for use in the disclosed method. In the case of animal tissue, for example, the matrix ions may originate from lipids, small proteins, or peptides.

[0125] The method can include providing a library of matrix data, wherein the matrix data comprises one or more physicochemical properties of one or more matrix components. The library containing the physicochemical properties of one or more matrix compounds or components can be generated by analyzing multiple tissue samples of a similar type. This library may not contain spatial information.

[0126] The method can include imaging a sample at multiple spatial locations, wherein the sample contains at least some of the matrix components and one or more analyte components. The method can include analyzing the sample at the multiple spatial locations to obtain sample data, wherein the sample data exhibit one or more physicochemical properties of one or more sample components (including at least some of the matrix components).

[0127] When the sample is imaged in one or more analytical runs, an array of mass spectra can be generated, each associated with a given spatial location or range of spatial locations. The time or period during which each mass spectrum is generated can also be recorded along with the spatial information.

[0128] One or more matrix compounds or components can be identified in the mass spectrum or mass spectra obtained during one or more analytical runs. One or more physicochemical properties of the one or more matrix compounds or components in the sample data can be recorded or determined. The physicochemical properties may include one or more of the mass / charge ratio, drift time, collision cross-section (CCS), interaction cross-section, ion mobility, and differential ion mobility.

[0129] Error values ​​can be determined or calculated by comparing the physicochemical properties of the matrix components in the library (i.e., the matrix data) with the physicochemical properties of the same matrix components in the (analytical) sample data. A time value or time period can be assigned to each error value by determining the time or times at which the one or more mass spectra containing the respective matrix component were recorded. Accordingly, the error values ​​can be recorded as a function of time and therefore assigned to a given spatial location or range of spatial locations.

[0130] The analytical data (i.e., the data not corresponding to the matrix) acquired at each spatial location can then be corrected based on the error values. For example, a plot of the error values ​​as a function of time (and therefore spatial location) can be generated, and one or more adjustment or correction values ​​can be determined from the plot. For example, a function corresponding to a best-fit line for the plot of the error values ​​can be determined, and one or more adjustment or correction values ​​can be determined from the function corresponding to the best-fit line.

[0131] The analyte data (for example, a mass spectrum or mass spectra) can therefore be corrected at any spatial location or at any range of spatial locations. It will be understood that the data being corrected may be mass / charge ratio values ​​in one or more mass spectra.

[0132] Some or all of the mass spectra obtained during the analysis run can be corrected or adjusted by determining the times or periods at which each mass spectrum was recorded, determining an adjustment or correction factor for each time or period (using the function), and applying each adjustment or correction factor to the mass spectrum obtained at that time or period.

[0133] In some cases, the sample may be inhomogeneous. For example, a cross-section of an entire animal may be imaged. In this case, optical imaging can be used to locate the spatial coordinates containing known common tissue types (liver, heart, brain, etc.).

[0134] When the library of matrix data is created, the detected matrix components can be assigned to a specific area of ​​the image corresponding to a known tissue type. This is equivalent to assigning a measured matrix value to a specific retention time according to the embodiments described above.

[0135] In some cases, certain matrix components are associated only with specific regions of the sample. This information can be used to directly compare matrix ions observed in subsequent (analytical) sample data. For example, the physicochemical properties of matrix components can be recorded in the library along with an associated location or sample region (e.g., liver, heart, brain, etc.).

[0136] When the analysis is performed, the matrix components or compounds identified in the mass spectra (i.e., the sample data) can be restricted to those components or compounds corresponding to the same location or sample region as the mass spectra. This can, for example, reduce the possibility of using the same matrix component but with an incorrect physicochemical property.

[0137] The matrix components used in the comparison between the sample data and the matrix data can be limited to those matrix components or compounds that correspond to the same location or sample area as the mass spectra.

[0138] This approach can be extended to other analyses that employ imaging or other surface scanning techniques. For example, in MALDI, it is known that an eluent from a chromatographic separation can be spatially applied to a target strip, thereby generating an image of the chromatographic separation. Again, matrix ions can be used to apply drift correction using the methods described above.

[0139] Samples for MALDI or DESI, etc., can be individually applied to specific locations on a target plate and subsequently analyzed. Again, the time at which each location on the target plate is analyzed can be recorded as described above, allowing drift at each target plate location to be corrected using the correlation between the matrix library and the sample.

[0140] Many other surface analysis or ion imaging techniques are known. For example, the methods described above can be used in direct real-time analysis (“DART”), matrix-assisted induction ionization (“MAIV”), liquid-microtransition surface sampling (“LJM-SSP”), liquid extraction surface analysis (“LESA”), low-temperature plasma (“LTP”), flowing atmospheric pressure afterglow (“FAPA”), or laser ablation electrospray ionization (“LAESI”).

[0141] Although the present disclosure has been described with reference to various embodiments, those skilled in the field will understand that various changes to the form and details can be made without deviating from the scope of protection of the disclosure set out in the attached claims.

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