Device and method for detecting elements in a sample

Abstract

The present invention discloses an apparatus and method for identifying compounds using spectra generated by X-rays at two different voltage levels.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to U.S. Patent Application Serial No. 62 / 871,570, filed on July 8, 2019, which is hereby incorporated by reference in its entirety for all purposes. Technical Field

[0003] The present invention relates to an apparatus and method for identifying elements, atoms and compounds within a sample using a portable device containing an X-ray source, wherein characteristic spectral signatures of the elements within the compound may or may not be visible using the portable X-ray fluorescence spectroscopy device. Background Art

[0004] Portable X-ray fluorescence (XRF) instruments, such as field portable units, are used by inspectors around the world to determine elemental distribution in a variety of sample matrices, including soils, minerals, ceramics, metals, polymers, thin films, and paint on different substrates. For example, the Thermo Scientific NITON XL5 uses various algorithms to correctly analyze the elemental composition in these different sample matrices. Typically, a given instrument will be used for the analysis of a single class of samples in a specific situation, such as the sorting of alloys, or the analysis of soil samples, or the analysis of paint in a house. In such cases, the analyzer is most effectively used when operating in a mode specifically developed to optimize performance for the sample class. The user selects from a menu on the touch screen or an associated computer, or the analyzer can execute an automatic routine to select the mode without user intervention. The ThermoScientific NITON XL5 can be used to analyze a variety of elements or atoms or compounds in a sample, where the elements or atoms or compounds exhibit a major elemental spectral signature using X-ray fluorescence. See, e.g., US 7,899,153; US 7,170,970; and US 7,430,274, each of which is incorporated herein by reference in its entirety for all purposes.

[0005] However, such field portable devices may be unable to identify certain compounds in a sample due to the lack of detectable primary X-ray fluorescence spectral signatures of some or all elemental constituents responsive to the portable device's X-ray source. Thus, there is a need for methods using portable devices that can identify certain compounds in a sample where the primary X-ray fluorescence spectral signatures of the constituent elements are indistinguishable. Summary of the invention

[0006] Aspects of the present disclosure relate to devices and methods, such as those presented in a portable device for identifying compounds in a sample where primary X-ray fluorescence spectral features are not readily distinguishable. The present disclosure provides for identification or confirmation of the identity of a test compound, as this is sometimes desired in industries where verification of the identity of a compound is required.

[0007] According to one aspect, a device and method are described herein that can detect and / or identify and / or quantify salt compounds or oxide compounds. According to a certain aspect, the device and method described herein can be used to detect and / or identify and / or quantify ionic salts or oxides. The device and method described herein that do not rely on wet chemical methods can be used to detect, identify and / or quantify compounds, such as salt compounds or oxide compounds.

[0008] As known in the field of X-ray fluorescence detection using handheld field portable devices, one or more atoms or elements of a test compound, such as magnesium or higher, can be detected based on a characteristic fluorescence peak generated at a first voltage level in response to X-rays, so as to detect, identify or quantify the test compound being analyzed. According to the present disclosure, reference to "element" or "atom" can be used interchangeably, as long as the element can be identified if the element is in its elemental state, atomic state or ionic state. According to one aspect, the test compound of the present disclosure contains one or more elements that do not exhibit a detectable or distinguishable fluorescence peak at a first voltage level, such as an element with an atomic weight lower than magnesium, so that a positive identification of the test compound cannot be determined based on the primary element spectrum fluorescence peak alone. However, by selecting a subset of library compounds having the same element identified by the fluorescence peak, the fluorescence peak obtained at the first voltage level can be used to identify the possible identity of the test compound from within the compound library. According to the present disclosure, a second spectrum of the test compound is obtained using X-rays at a second higher voltage level. The second spectrum or a portion of the second spectrum is matched with a reference spectrum of a compound within the subset of library compounds to identify the test compound. According to the present disclosure, reference spectra of multiple compounds at a second higher voltage level are obtained to form a reference spectrum library for comparison with the test spectrum at the second higher voltage level. In addition to the specific methods disclosed herein, methods for determining whether a test spectrum matches a reference spectrum are known to those skilled in the art and can be utilized in the present disclosure.

[0009] According to one aspect, a portable device is provided that can be used to detect, identify and / or quantify a test compound that includes an element that exhibits a primary element x-ray fluorescence spectral signature and an element that does not exhibit a primary element x-ray fluorescence spectral signature. One or more primary element x-ray fluorescence spectral signatures are obtained at a first voltage level to identify a candidate compound, and then a second spectrum is obtained at a second voltage level that is higher than the first voltage level. The second spectrum or a portion of the second spectrum is matched with a reference spectrum of the candidate compound to identify the test compound.

[0010] According to one aspect, a portable device is provided that can be used to detect, identify and / or quantify a test compound that includes an element with a molecular weight lower than magnesium and an element with a molecular weight of magnesium and higher. One or more primary element X-ray fluorescence spectral features are obtained at a first voltage level to identify a candidate compound, and then a second spectrum is obtained at a second voltage level higher than the first voltage level. The second spectrum is matched with a reference spectrum of the candidate compound to identify the test compound.

[0011] The present disclosure has application in detecting, identifying and / or quantifying chemical compounds such as salts or oxides, where the elements of such salts or oxides contain one or more or all atoms that do not exhibit, produce or generate a detectable or distinguishable primary primary element X-ray fluorescence spectral signature or peak in response to X-ray probing.

[0012] Further features and advantages of certain embodiments of the present disclosure will become more apparent from the following description of the embodiments and their accompanying drawings, and from the claims.According to representative methods, one or more conventional steps, such as those associated with sample preparation, may be simplified or even omitted. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The foregoing and other features and advantages of embodiments of the present invention will be more fully understood from the following detailed description of illustrative embodiments taken in conjunction with the accompanying drawings, in which:

[0014] Figure 1 An exemplary handheld X-ray fluorescence device flow chart showing the methods described herein.

[0015] Figure 2 A flow chart showing the method described herein is shown.

[0016] Figure 3A A table showing the salt and oxide compounds of interest and their corresponding densities and u-values.

[0017] Figure 3B Shown Figure 2Elastic versus inelastic scattering for a subset of compounds plotted against the value of u at 16.61 keV.

[0018] Figure 3C Shown Figure 3B The corresponding data table for the drawing.

[0019] Figure 4A Statistical t-tests of the fitted models based on least squares for both slope and offset are presented.

[0020] Figure 4B Shown is a statistical scaling of the t-score results to D values ​​between 0 and 1, where 1 is a perfect fit.

[0021] Figure 5 Table showing areas of interest with characteristic peaks for elements commonly detectable with handheld XRF.

[0022] Figure 6 A table showing the slope fit of the D value between the evaluation set and the training set over a 30-second measurement period is shown.

[0023] Figure 7 Shown is a table of t-score slope fits between the evaluation set and the training set over a 30-second measurement period.

[0024] Figure 8 A fitted table showing the D value offset between the evaluation set and the training set over a 30-second measurement period is shown.

[0025] Fig. 9 Shown is a fitted table of the t-score offset between the evaluation set and the training set over a 30-second measurement.

[0026] Fig. 10A An example of plotting fit of Na2CO3 to the elements of the training set is shown.

[0027] Fig. 10B An overlay of spectral plots of different samples compared to Na2CO3 is shown.

[0028] Fig.11A An example of a plot fit of MgO to the elements of the training set is shown.

[0029] Fig. 11B An overlay of the spectral plots of different samples compared to MgO is shown.

[0030] Fig. 12A A table showing the calculated t-scores for NaBr and NH4Br at 10, 20 and 30 seconds.

[0031] Fig. 12B A table showing the calculated t-scores for NaBr and NH4Br at 10, 20 and 30 seconds.

[0032] Fig.13A Table showing the calculated t-scores for the slopes over a 50 second measurement.

[0033] Fig. 13B Table showing calculated D values ​​for the slope over a 50 second measurement.

[0034] Fig.14A -B shows an example match table showing the 1st match result and the 2nd match result within 15, 30 and 50 seconds.

[0035] The accompanying drawings should be understood as illustrations presenting embodiments of the invention and / or the principles involved. It will be apparent to those skilled in the art having knowledge of the present disclosure that other devices, methods and analytical instruments will have configurations and components determined in part by their specific uses. Throughout the several views of the drawings, like reference numerals refer to corresponding parts.

[0036] Like reference numerals refer to corresponding parts throughout the several views of the drawings. DETAILED DESCRIPTION

[0037] The present disclosure provides an apparatus and method for identifying a compound using an X-ray source in a portable device. The X-ray source can generate or emit X-rays using different voltage levels. X-rays at a first voltage level can be used to generate a primary element X-ray fluorescence spectrum from a compound. X-rays at a second voltage level higher than the first voltage level can be used to generate a second spectrum from a sample. The device can be field portable or handheld, containing one or more microprocessors, databases or software programs to identify and / or store and / or compare spectra, and implement one or more algorithms for comparing spectra or parts of spectra to identify test compounds from known candidate compounds. Certain algorithms and quantitative methods using X-ray fluorescence are described in US 7,899,153, which is hereby incorporated by reference in its entirety.

[0038] According to one aspect, a portable device generates X-ray radiation and emits it toward a sample for analysis. If there are elements in the sample that emit fluorescence in response to X-rays, the sample is irradiated with X-rays generated at a first voltage level and the X-ray fluorescence is detected by a detector in the device. X-ray fluorescence is detected and analyzed from the sample, for example, using a peak identification algorithm to determine the presence of a peak. The X-ray fluorescence of each element is represented by one or more spectral peaks, namely, a primary element X-ray fluorescence spectrum. Based on the primary element X-ray fluorescence spectrum, the device selects one or more candidate compounds from a stored compound library, each of which contains all identified elements and one or more unidentified elements to generate a subset of library compounds. It should be understood that a subset can be created by selecting a library compound containing all identified elements of the test compound or by deselecting a library compound that does not contain all identified elements of the test compound. If the device identifies an element that is not present in a member of the library, the member of the library cannot be a correct compound and is excluded. If one or more members in the library contain elements that are not identified by a normally detectable characteristic peak identified by X-ray fluorescence from the sample, the one or more members are excluded as possible compounds in the sample.

[0039] According to one aspect, the test compound contains an additional element that does not exhibit a primary element X-ray fluorescence spectrum in response to a first voltage level. According to this aspect, the sample is irradiated with X-rays generated at a second voltage level higher than the first voltage level, and the second spectrum is detected by a detector in the device. The second spectrum is compared to a reference spectrum obtained at a second voltage level for a subset of library compounds. If the second spectrum substantially matches the reference spectrum of a candidate compound within the subset of library compounds, the test compound is identified as a candidate compound.

[0040] According to one aspect, a method is provided that utilizes a library or training set of compounds having associated X-ray fluorescence spectra of standards. The compounds also have associated reference spectra obtained using X-rays generated at a second voltage as described herein. A library can be created by irradiating a known compound with X-rays generated by a second voltage, detecting a second spectrum, and saving the second spectrum as a reference for a known compound with a known molecular formula to compare with a test second spectrum. The library can contain any number of compounds.

[0041] According to the present disclosure, a portable device is provided that can identify a test compound that includes one or more elements having a primary X-ray fluorescence spectrum at a first voltage level and one or more elements having no discernible or detectable primary X-ray fluorescence spectrum at the first voltage level. Aspects of the present disclosure use a combination of a primary X-ray fluorescence spectrum obtained at a first voltage level and a second spectrum of the test compound obtained at a second voltage level higher than the first voltage level.

[0042] According to one aspect, the portable device uses a computer-implemented algorithm to compare the second spectrum with a reference spectrum of a subset of library compounds to identify or confirm the identity of the test compound. According to this aspect, the second spectrum is detected and analyzed, such as by dividing the full spectrum (such as between 2 and 40 keV) into different regions of interest ("ROI"), such as from 2.4 to 2.6 keV. Weighting factors can be applied to each region of interest to weight the spectral features according to their importance for identification. The weighting factors can be dynamically modified based on the sample and the compounds believed to be present in the sample.

[0043] According to one aspect, the entries in the library can be compared to the spectrum obtained from the sample being analyzed to calculate the least squares slope and intercept. A sample spectrum that perfectly matches the library spectrum has a slope of 1.0 and an intercept of 0. For example, according to C-Val = 1.0 - sqrt ((slope 2 )+Offset 2 )), a score (C-Val) is calculated for each potential match using the square root of the sum of the squares of the slope and intercept.

[0044] According to one aspect, the compound analyzed can be suspected or known, and the method can be used to confirm the identity of the sample. Therefore, the user can input the suspected or known identity of the compound or other assumptions about the compound into the method, and the similarity of the sample compound and the input compound can be analyzed. Alternatively, the compound analyzed may be unknown, and the method can be used to identify the compound of the sample. In this way, the portable device can analyze and identify the element with primary element X-ray fluorescence spectrum characteristics (such as an element with an atomic weight equal to or higher than magnesium) and the compound without the element with primary element X-ray fluorescence spectrum characteristics (such as an element with an atomic weight lower than magnesium). Such devices are particularly suitable for identifying salts containing sodium, lithium, beryllium or oxides.

[0045] After reading the following disclosure, it will be understood by those of ordinary skill in the art that the various aspects described herein may be embodied as computerized methods, systems, devices or equipment utilizing one or more computer program products. Therefore, various aspects of computerized methods, systems, devices or equipment may take the following forms: embodiments consisting entirely of hardware including one or more microprocessors, embodiments consisting entirely of software, or embodiments combining software and hardware aspects. In addition, various aspects of computerized methods, systems, devices and equipment may take the form of computer program products, which are stored by one or more non-transitory computer-readable storage media having computer-readable program codes or instructions, which are embodied in or on the storage medium. Any suitable computer-readable storage medium may be utilized, including hard disks, CD-ROMs, optical storage devices, magnetic storage devices and / or any combination thereof. In addition, various signals representing data or events as described herein may be transferred between a source and a destination in the form of electromagnetic waves, which propagate through signal-conducting media, such as metal wires, optical fibers and / or wireless transmission media (e.g., air and / or space). It should be noted that various connections between elements are understood by those skilled in the art or as described herein. It should be noted that these connections are universal and, unless otherwise specified, may be direct or indirect, wired or wireless, and that this specification is not intended to be limiting in this regard.

[0046] Thus, the present disclosure relates to a method for identifying a compound by obtaining a first X-ray fluorescence spectrum of the compound at a first voltage level, identifying one or more elements from one or more corresponding peaks of the X-ray fluorescence spectrum, selecting compounds containing the one or more elements within a compound library and creating a subset consisting of the selected compounds, obtaining a second spectrum of the compound at a second voltage level higher than the first voltage level, comparing the second spectrum with a reference spectrum generated for the selected compound in the subset at the second voltage level, and identifying the compound by matching the second spectrum with a reference spectrum corresponding to the selected compound. According to one aspect, the one or more elements have an atomic weight of magnesium or greater. According to one aspect, the compound contains one or more elements with an atomic weight lower than magnesium. According to one aspect, the compound is a salt or oxide compound containing one or more elements with an atomic weight lower than magnesium. According to one aspect, the compound library includes salt or oxide compounds that cannot be distinguished by X-ray fluorescence characteristic peak analysis alone. According to one aspect, the second spectrum is matched to a reference spectrum using a linear fitting model to compare and match the shape of the second spectrum with the shape of the reference spectrum. According to one aspect, the second spectrum is matched to a reference spectrum using a least squares slope and intercept method, and wherein the shape of the second spectrum is matched to the shape of the reference spectrum by a calculated slope of 1.0 and an intercept of 0. According to one aspect, one or more microprocessors, one or more electronic databases, and one or more software programs are used to: (1) identify the one or more elements from the first X-ray fluorescence spectrum of the compound at a first voltage level; (2) select a compound within the compound library; (3) compare the second spectrum to the reference spectrum of the selected compound in the subset; and (4) identify the compound by matching the second spectrum to the reference spectrum corresponding to the selected compound. According to one aspect, one or more regions of interest of the second spectrum are compared to the reference spectrum of the selected compound in the subset, and the compound is identified by matching the one or more regions of interest of the second spectrum to the reference spectrum corresponding to the selected compound. According to one aspect, a weighting factor is applied to the one or more regions of interest of the second spectrum to compare the one or more regions of interest to the reference spectrum of the selected compound in the subset using a linear fit model. According to one aspect, weighting factors are dynamically applied to one or more regions of interest of the second spectrum to compare the one or more regions of interest to the reference spectrum of the selected compounds in the subset using a linear fit model.According to one aspect, the first X-ray fluorescence spectrum of the compound is obtained by irradiating the compound with X-ray radiation generated at a first voltage level between 3 and 9 keV for 3 to 30 seconds using a first filter. According to one aspect, the second spectrum of the compound is obtained by irradiating the compound with X-ray radiation generated at a second voltage level between 30 and 60 keV for 30 to 300 seconds using a second filter.

[0047] Example I

[0048] Field portable devices

[0049] According to one aspect, a portable XRF device is described herein to perform the methods described herein. Suitable portable, field portable or handheld XRF devices known in the art can be modified by hardware or software to perform the methods described herein. An exemplary and useful field portable XRF device includes the Thermo Scientific NITON XL5. Such devices perform non-destructive analysis of sample compounds or materials.

[0050] According to one aspect, a portable device is used to perform non-destructive XRF analysis on a sample to identify compounds within the sample. An XRF analyzer determines the chemical composition of a sample by measuring fluorescent (or secondary) X-rays emitted by the sample when excited by an X-ray source. Elements present in the sample produce a characteristic set of X-rays unique to the element. An exemplary handheld device is Figure 1 is shown as comprising an X-ray source and a detector. The detector is operably connected to a digital signal processor, which is operably connected to a computer processing unit, which is suitable for a portable, handheld, battery-powered device. The onboard computer processing unit is capable of performing the necessary functions described herein to provide answers at the point of use while still remaining compatible with the requirements of the portable device. The portable device can optionally be connected to a computer network wirelessly or through a USB port to provide additional functionality, including data transmission, instrument status monitoring, device management, and additional computing resources for more advanced offline analysis. The handheld device includes a display unit for displaying information or for inputting information or for selecting various analysis modes provided by the handheld device.

[0051] According to one aspect, the handheld device can: (1) operate at a selected voltage between 4 kV and 60 kV; (2) operate at a selected current of up to 1000 uA; (3) operate using a filter selected from Al, Cu, Fe, Mo or no filtering, including combinations thereof; and (4) operate for a selected time period between 3 and 300 seconds.

[0052] Atoms that respond to X-rays have several electron orbitals (e.g., K shells, L shells, M shells). When the X-ray energy transfers electrons into and out of these shells, XRF peaks of varying intensities are generated and will be present in a spectrum, which is a graphical representation of the X-ray peaks as a function of energy. The peak energy identifies the element, and the peak height / intensity generally indicates the concentration of the element in the sample. X-ray fluorescence methods are known to those skilled in the art and can be utilized in the methods of the present invention based on the present disclosure.

[0053] Example II

[0054] XRF Method

[0055] according to Figure 2 In one aspect depicted in the flowchart of , a spectral library of known compounds is stored in a handheld device. Such a library can be created by inputting the molecular formula of the compound into the device and (1) scanning the compound at a selected voltage, (2) at a selected current, (3) using a selected filter and (4) within a selected time period. The device detects the fluorescence emission from the compound and then stores the relevant spectral information in the memory of the device. The process is typically repeated for each compound of interest to create a library. Alternatively, a pre-created library can be uploaded to the device via a wireless or USB connection. See step 100. For example, a user can upload or input a compound identifier (e.g., a formula or other identifier known in the art) into the device and perform a first scan of the compound. A "high" voltage (e.g., a voltage of about 50 kV) can be used to perform a first scan at a selected current such as 5 uA within a time period of about 3-30 seconds, and the fluorescence emission from the compound is detected. In some cases, it may be desirable to use a filter before the detector and / or tube to remove noise in the fluorescence signal that is not related to the compound itself.

[0056] In the first scan using the first set of preconfigured conditions, a sample that may be known or unknown is irradiated with X-rays emitted from the handheld device. The first scan radiation is usually performed using an X-ray tube as a source, wherein the endpoint energy of the X-ray tube can be 4kV to 10kV. The X-rays emitted by the source are usually not filtered in such low-energy measurements expected for detecting light elements, but can be filtered to optimize the excitation spectrum, as has been demonstrated in the art. The use of an X-ray source (such as an X-ray tube) and the use of a window and / or an element filter (such as a Cu filter or other filter) are standard XRF techniques, such as described in U.S. Pat. No. 6,765,986 to Grodzins et al., which is incorporated herein by reference. In the first scan, the sample is detected and sorted according to energy in the handheld analyzer by radiation scattering and / or resonant emission (fluorescence). See step 110. An exemplary first set of preconfigured radiation parameters lasts for a period of about 3-30 seconds between 5 and 8keV. As described above, it may be desirable to use a filter in front of the detector to remove noise from the fluorescence signal. The first set of preconfigured radiation parameters is particularly advantageous for detecting fluorescence lines of elements containing K, Cl, Mg, Ca, or S. Such elements are low Z (or light elements) elements where characteristic L lines can be seen with a handheld XRF device.

[0057] The signal processor then analyzes the detected fluorescence to identify one or more elements or atoms. See step 120. For example, the signal processor and / or CPU can perform analysis to identify characteristic peaks in the detected spectrum from the sample that indicate one or more light elements or atoms.

[0058] Then, the signal processor and / or CPU compares the identified elements or atoms from the sample with the compound library to generate a subset of possible compounds. For example, compounds in the library that do not have the identified one or more elements or atoms are not selected as possible compound matches for the subset. Further, if the processor and / or CPU fails to identify any elements or atoms, compounds with "light elements" in the library are not selected as possible compound matches for the subset. See step 130.

[0059] The sample is then subjected to a second higher voltage scan using a second set of preconfigured radiation parameters. An exemplary second set of preconfigured radiation parameters is between 30 and 50 kV at 5 uA to 10 uA for a period of about 3-30 seconds to obtain a second spectrum. As described above, it may be desirable to use a filter in front of the detector and / or tube to remove noise from the fluorescence signal. See step 140.

[0060] The resulting spectral features from the second, higher voltage scan are then compared to spectral information in a subset of compounds selected from the library. According to one aspect, the signal processor and / or CPU calculates a least squares slope and intercept that compares the entries in the candidate compound subset to the features of the spectrum obtained from the sample being analyzed. The signal processor and / or CPU selects the best match and identifies the sample as the compound associated with the best match. See step 150. For example, a sample spectrum that perfectly matches a spectrum in the subset would have a slope of 1.0 and an intercept of 0. According to C-Val=1.0–sqrt((slope 2 )+Offset 2 )), a score (C-Val) is calculated for each potential match using the square root of the sum of the squares of the slope and intercept. Further, in some applications, an algorithm can be used to first separate the detected spectrum into different regions of interest, and a weighting factor can be applied to one or more regions of interest to weight the spectral features that are important for identification. The weighting factors are dynamically modified based on the sample and the compounds believed to be present in the sample.

[0061] Example III

[0062] Analysis of ionic salts and oxides

[0063] A Thermo Niton XL2 980SDD handheld unit with a 45 kV Ag anode X-ray tube with variable tube current, 8 mm X-ray spot and Mo primary filter was used to analyze the following thirteen ionic salts and three oxides: Na 2 CO 3 、CaCO 3 , KHCO 3 NH 4 Cl, NaBr, NaI, NaCl, CaCl 2 NH 4 Br, KBr, KCl, KI, Al 2 O 3 、MgO、SiO 2 and K 2 Cr 2 O 7 A second library of spectra for each known compound ("training set") was created by irradiating each substance at a voltage of 45 kV for 100 seconds. Test samples ("evaluation set") were irradiated for 30, 20 and 10 seconds. Figure 3A , 3B and 3C depict the coherent Compton peaks of certain salts or oxides. Figure 3B As demonstrated in the figure of , the plot of the Coh / Com ratio against u gives a best fit line with R2 values ​​> 0.96 for the 16.61 keV Compton line for the tested salts and oxides. Figure 3C is a tabular representation of this data.

[0064] Each spectrum in the evaluation set was iteratively compared to each spectrum in the training set using the linear fit model. For each iteration, the following parameters were calculated: correlation coefficient R^2; slope; offset; error slope; error offset; t-statistic slope; t-score D–0≤D≤1; P-value slope; t-statistic offset; and P-value offset. The t-score D was used as the matching criterion. The fitted model was Figure 4A and 4B Although the described embodiment shows least squares estimates for both the slope and the offset, it will be appreciated that higher order fit statistics may be used. The matching criterion D is Figure 4B . In this embodiment, the t-score is scaled from zero to one to provide a consistent match score, with 1 being a perfect fit and approaching zero as the fit gets worse. Again, it should be understood that the scale can be adjusted statistically so that a relative fit scale can be established. For example, a perfect fit of 1 can be used, and scaling to larger negative numbers can indicate a decreasing likelihood of a match. In this manner, matches can be scaled from best to worst in situations where the user wants to know not only the best match, but also any number of subsequent less-than-ideal matches. The defined region of interest used is Figure 5 These regions of interest correspond to the characteristic peaks of the elements and contain a range of energies in keV. The bands around the characteristic peaks are selected as regions of interest to allow for later quantitative analysis by conventional XRF analysis techniques. These regions of interest can be adjusted based on the element library and the specific operating characteristics of the device. The correlation coefficient R^2 from the training set at 30 seconds for the evaluation set from the sample is Figure 6 Shown: The slope at 30 seconds from the training set versus the evaluation set from the sample Figure 7 and the slope of t at 30 seconds from the training set to the evaluation set from the sample Figure 8 and the slope of Dt from the training set at 30 seconds versus the evaluation set from the sample Fig. 9 Shown. Figure 6-9 The circled areas shown in the figure highlight compounds that are particularly difficult to distinguish from each other, especially NaBr, NH 4 Br and KBr. Importantly, Fig. 9 The Dt score slopes shown in show a perfect match for each of these compounds (eg, 1.0000000), where the mismatch scores easily distinguish them as incorrect matches.

[0065] Fig. 10A The linear fitting algorithm is used to plot the Na 2 CO 3Test second spectrum of sample compound with Na 2 CO 3 The reference second spectrum (line 1001) is matched with a slope of 1.000 and an offset of 0.000. Fig. 10B An overlay of all spectra on the plot is depicted for comparison.

[0066] Fig.11A Depicted is the matching of a test second spectrum of MgO to a reference second spectrum of MgO (line 1101) using a linear fit algorithm, where the slope is 1.000 and where the offset is 0.000. Fig. 11B An overlay of all spectra on the plot is depicted for comparison.

[0067] Fig. 12A Depicted are NaBr and NH 4 Br is calculated from the data for the indicated t at 30 s, 20 s and 10 s. Fig. 12B Depicted are NaBr and NH 4 The data calculations for D indicated by Br at 30 seconds, 20 seconds and 10 seconds. These tables show the positive identification results for NaBr and NH4Br at 10 seconds, 20 seconds and 30 seconds measurement time. Fig. 12B As shown in the table, the primary identification of each compound is accurate and the second best identification is indeed another Br-containing compound. Using standard characteristic peak analysis alone, it would not be possible to make a determination between these compounds.

[0068] Fig.13A Calculated t values ​​at 50 seconds are depicted for various salt and oxide compounds. Fig. 13B The calculated d scores at 50 seconds are depicted for various salt and oxide compounds.

[0069] Fig.14A -B depicts data from spectra collected at approximately 15, 30, and 50 seconds and the resulting matches of the evaluation set compounds to the training set. Column 1 is the best matching compound, column 2 is the second best match. The third column is the actual sample under evaluation. As can be seen from the table, the evaluation correlates well with the actual. For example, in Fig. 14B In the 4 Br was difficult to distinguish but could be matched correctly and had enough time to acquire the spectral features in the second scan.

[0070] Those skilled in the art will recognize, through the knowledge gained from this disclosure, that various changes may be made to the disclosed apparatus and methods to obtain these and other advantages without departing from the scope of the present invention. Thus, it should be understood that the features described herein are susceptible to modification, alteration, change or replacement. The specific embodiments shown and described herein are for illustrative purposes only and are not limitations of the invention set forth in the appended claims. Other embodiments will be apparent to those skilled in the art. It should be understood that the foregoing description is provided only for the sake of clarity and is merely exemplary. The spirit and scope of the present invention are not limited to the above examples, but are covered by the appended claims. All the disclosures and patent applications cited above are incorporated herein by reference in their entirety to the same extent for all purposes, and the extent of their reference is as if each individual disclosure or patent application was specifically and individually indicated to be incorporated by reference in this manner.

Claims

1. A method for identifying a compound, the method comprising: obtaining a first X-ray fluorescence spectrum of the compound at a first voltage level, identifying one or more elements from one or more corresponding peaks in the X-ray fluorescence spectrum, selecting compounds in the compound library that contain the one or more elements and creating a subset consisting of the selected compounds, obtaining a second X-ray fluorescence spectrum of the compound at a second voltage level higher than the first voltage level, comparing the second X-ray fluorescence spectrum to a reference spectrum generated by the selected compound in the subset at the second voltage level, and The compound is identified by matching the second X-ray fluorescence spectrum to a reference spectrum corresponding to the selected compound.

2. The method of claim 1, wherein the one or more elements have an atomic weight of magnesium or greater.

3. The method of claim 1, wherein the compound comprises one or more elements having an atomic weight lower than magnesium.

4. The method according to claim 1, wherein the compound is a salt or oxide compound containing one or more elements having an atomic weight lower than magnesium.

5. The method of claim 1, wherein the compound library comprises salts or oxide compounds that cannot be distinguished by X-ray fluorescence alone. 6 . The method of claim 1 , wherein the second X-ray fluorescence spectrum is matched with a reference spectrum using a linear fitting model to compare and match a shape of the second X-ray fluorescence spectrum with a shape of the reference spectrum.

7. The method of claim 1, wherein the second X-ray fluorescence spectrum is matched to a reference spectrum using a least squares slope and intercept method, and wherein a shape of the second X-ray fluorescence spectrum is matched to a shape of the reference spectrum by a calculated slope of 1.0 and an intercept of 0.

8. The method of claim 1, wherein one or more microprocessors, one or more electronic databases, and one or more software programs are used to: (1) identify the one or more elements from the first X-ray fluorescence spectrum of the compound at a first voltage level; (2) selecting a compound from the compound library; (3) comparing the second X-ray fluorescence spectrum with the reference spectrum of the selected compound in the subset; and (4) identifying the compound by matching the second X-ray fluorescence spectrum with a reference spectrum corresponding to the selected compound.

9. The method of claim 1 , wherein one or more regions of interest of the second X-ray fluorescence spectrum are compared to the reference spectrum of the selected compound in the subset, and the compound is identified by matching the one or more regions of interest of the second X-ray fluorescence spectrum with the reference spectrum corresponding to the selected compound.

10. The method of claim 1, wherein weighting factors are applied to one or more regions of interest of the second X-ray fluorescence spectrum to compare the one or more regions of interest to the reference spectra of the selected compounds in the subset using a linear fit model.

11. The method of claim 1 , wherein weighting factors are dynamically applied to one or more regions of interest of the second X-ray fluorescence spectrum to compare the one or more regions of interest to the reference spectra of the selected compounds in the subset using a linear fit model.

12. The method of claim 1, wherein the first X-ray fluorescence spectrum of the compound is obtained by irradiating the compound with X-ray radiation generated at a first voltage level between 3 and 9 keV using a first filter for 3 to 30 seconds.

13. The method of claim 1, wherein the second X-ray fluorescence spectrum of the compound is obtained by irradiating the compound with X-ray radiation generated at a second voltage level between 30 and 60 keV for 30 to 300 seconds using a second filter.

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