Analysis method

Abstract

Provided is a technique for shortening an analysis time in relation to analysis of a polymer material. An analysis method according to the present disclosure is a method for analyzing a polymer material. Components contained in the polymer material are dissolved in a sample. In the analysis method of the present disclosure, a mass spectrometry device subjects the sample in which the polymer material has been dissolved to ionization by means of electrospray ionization. Then, in the analysis method of the present disclosure, the mass spectrometry device subjects the sample that has been subjected to ionization by the electrospray ionization to mass spectrometry.

Description

Analysis method

[0001] The present disclosure relates to analytical methods, and in particular to analytical methods for polymeric materials.

[0002] Various proposals have been made for the analysis of polymeric materials. Conventional analysis of polymeric materials has utilized a system that combines chromatography (liquid chromatography or gas chromatography) with a mass spectrometer, as described in, for example, Non-Patent Documents 1-3.

[0003] "Analysis of Additives in Food Containers Using a Quadrupole Time-of-Flight Mass Spectrometer LCMSTM-9030," Takahiro Goda, October 2020, https: / / www.an.shimadzu.co.jp / sites / an.shimadzu.co.jp / files / pim / pim_document_file / an_jp / applications / application_note / 18185 / an_c236.pdf; "Analysis of Additives in Resin Using a Triple Quadrupole Mass Spectrometer," Chigusa Ichikawa, September 2021, https: / / www.an.shimadzu.co.jp / sites / an.shimadz "Differential Analysis of Food Packaging Films Using Pyrolysis-GC-MS," Yoshito Kawakita and Toshinari Ishii, July 2022, https: / / www.an.shimadzu.co.jp / sites / an.shimadzu.co.jp / files / pim / pim_document_file / an_jp / applications / application_note / 17538 / an_01-00404-jp.pdf

[0004] However, conventional systems require relatively long analysis times because they involve chromatography.

[0005] The present disclosure has been made in view of the above circumstances, and its purpose is to provide a technique for shortening the analysis time for analyzing polymeric materials.

[0006] An analytical method according to one aspect of the present disclosure is a method for analyzing a polymeric material, and includes: performing ionization by electrospray ionization on a sample in which the polymeric material is dissolved in a mass spectrometer; and performing mass analysis of the ionized sample in the mass spectrometer.

[0007] According to certain aspects of the present disclosure, analysis time is reduced for the analysis of polymeric materials.

[0008] 6 is a diagram showing an example of the configuration of an analysis system. FIG. 7 is a diagram showing the configuration of an MS unit 520. FIG. 8 is a flowchart of processing for analyzing a polymer material. FIG. 9 is a diagram showing an example of a screen for displaying the results of multivariate analysis. FIG. 10 is a diagram showing another example of a screen for displaying the results of multivariate analysis. FIG. 11 is a diagram showing yet another example of a screen for displaying the results of multivariate analysis. FIG. 12 is an enlarged view of a portion of the loading plot of FIG. 6.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0010] [Configuration of Analysis System] Fig. 1 is a diagram showing an example of the configuration of an analysis system. As shown in Fig. 1, the analysis system 500 includes an LC unit 510, an MS unit 520, a system controller 530, and a control unit 540.

[0011] The LC section 510 includes an HPLC. The MS section 520 includes an ionization chamber 20, a mass separation section 29 (the first intermediate vacuum chamber 21, the second intermediate vacuum chamber 22, and the analysis chamber 23 in FIG. 2), and an ion detector 235. The structure of the MS section 520 will be described in detail with reference to FIG. 2. The control section 540 is configured by a general-purpose computer and is connected to the LC section 510 and the MS section 520 via a system controller 530.

[0012] The LC unit 510 includes a mobile phase container 511, a liquid delivery pump 512, an injector 513, a flow path switching valve 514, a column 515, and a column oven 516. The column 515 may be any column for reverse-phase chromatography, but an ODS (Octa Decyl Silyl) column is suitable. The flow path switching valve 514 is configured to be switchable between a state in which multiple ports provided on the valve 514 are connected as shown by the dotted lines in FIG. 1 (hereinafter also referred to as the "first state") and a state in which they are connected as shown by the solid lines in FIG. 1 (hereinafter also referred to as the "second state").

[0013] FIG. 2 shows the configuration of the MS section 520. The MS section 520 has a multistage differential pumping system configuration with first and second intermediate vacuum chambers 21 and 22, whose vacuum levels are gradually increased, between the ionization chamber 20 and the analysis chamber 23. The ionization chamber 20 is at approximately atmospheric pressure. The analysis chamber 23 can be evacuated to a high vacuum by a vacuum pump (not shown). The ionization chamber 20 is equipped with an electrospray ionization (ESI) probe 201, which sprays the sample solution while imparting an electric charge. The ionization chamber 20 and the next-stage first intermediate vacuum chamber 21 are connected via a thin-diameter heated capillary 202. The first intermediate vacuum chamber 21 and the second intermediate vacuum chamber 22 are separated by a skimmer 212. The skimmer 212 has a small hole at its top. The first intermediate vacuum chamber 21 and the second intermediate vacuum chamber 22 are respectively equipped with ion guides 211 and 221 for focusing ions and transporting them to the downstream stage. In the analysis chamber 23, a quadrupole mass filter (Q1) 231 is arranged in the upstream stage, and a quadrupole mass filter (Q3) 234 is arranged in the downstream stage, with a collision cell 232 sandwiched between them. Both the quadrupole mass filter (Q1) 231 and the quadrupole mass filter (Q3) 234 can separate ions according to their mass-to-charge ratio. A multipole ion guide 233 is installed inside the collision cell 232. The analysis chamber 23 further includes an ion detector 235 installed downstream of the downstream quadrupole mass filter 234. A predetermined voltage is applied from the power supply unit 3 to each of the multiple elements, including the ESI probe 201, ion guides 211, 221, and 233, and quadrupole mass filters 231 and 234. Each of the quadrupole mass filters 231 and 234 has a pre-rod electrode in front of the main rod electrode to correct the disturbance of the electric field at the inlet end, and a voltage different from that applied to the main rod electrode can be applied to the pre-rod electrode.

[0014] The MS section 520 has a configuration capable of performing MS / MS analysis. In the MS section 520, only the pre-quadrupole mass filter 231 may be used as a mass separation section, no CID gas may be supplied to the collision cell 232, and a voltage may be applied to the multipole ion guide 233 and the post-quadrupole mass filter 234 so that ions mass-separated by the pre-quadrupole mass filter 231 pass through as is. Instead of an LC / MS / MS device, the analysis system 500 may employ an LC / MS device in which a mass spectrometer configured specifically for MS analysis is combined with the LC section 510.

[0015] In the MS section 520, when the eluate from the LC section 510 reaches the electrospray ionization probe 201, the eluate is sprayed while being charged at the tip of the probe 201. The charged droplets formed by the spray are fragmented and reduced in size by the action of electrostatic force due to the applied charge, and in the process, the solvent evaporates and ions derived from the compound are released. The ions thus generated are sent to the first intermediate vacuum chamber 21 through the heated capillary 202, converged by the ion guide 211, and sent to the second intermediate vacuum chamber 22 through the small hole at the top of the skimmer 212. The ions derived from the compound are then converged by the ion guide 221 and sent to the analysis chamber 23, where they are introduced into the space in the longitudinal direction of the front-stage quadrupole mass filter 231. Note that the ionization method is not limited to electrospray ionization, and atmospheric pressure chemical ionization, atmospheric pressure photoionization, etc. may also be used.

[0016] A predetermined voltage (a voltage obtained by superimposing a radio frequency voltage and a DC voltage) is applied from the power supply unit 3 to each rod electrode of the quadrupole mass filter 231. Of the various ions sent into the quadrupole mass filter 231, only ions having a specific mass-to-charge ratio corresponding to the voltage applied to each rod electrode of the quadrupole mass filter 231 pass through the quadrupole mass filter 231. The ions that have passed through the quadrupole mass filter 231 then pass through the collision cell 232 and the quadrupole mass filter 234 and are detected by the ion detector 235. The ion detector 235 is, for example, a pulse counting detector, and outputs a number of pulse signals corresponding to the number of incident ions as detection signals to the system controller 530.

[0017] (Processing Flow) Fig. 3 is a flowchart of a process for analyzing a polymer material. This process will be described below with reference to Fig. 6.

[0018] First, in step S20, the user prepares a sample. In one implementation example, to prepare a sample, the user first chops a polymer material into small pieces (e.g., about 1 cm square) with scissors and then adds 2 mL of THF (tetrahydrofuran) to 0.1 g of the chopped polymer material to create a polymer material solution. Note that the solvent added is not limited to THF and may be other types of solutions, such as a solution of equal parts cyclohexane and isopropyl alcohol. The user then applies ultrasonic vibrations to the polymer material solution for a certain period of time (e.g., 8 minutes), adds 2 mL of methanol, and collects the supernatant. The user then prepares a sample by diluting the supernatant two-fold with IS solution (a methanol solution containing 1 ppm reserpine and 5 ppm chloramphenicol as internal standards).

[0019] In step S22, the user sets the sample prepared in step S20 in the injector 513.

[0020] In step S24, the user instructs the analytical system 500 to perform flow injection analysis. In one implementation example, the instruction is input to the analytical system 500 by the user operating the control unit 540 in a given manner. In response to the instruction, the analytical system 500 performs flow injection analysis, whereby the sample is introduced from the LC unit 510 to the MS unit 520 according to the flow injection method and subjected to mass analysis in the MS unit 520.

[0021] In flow injection analysis, a sample is injected from an injector 513 into a mobile phase delivered by a liquid delivery pump 512. As a result, the sample is introduced directly into the MS unit 520 without passing through the column 515. Specifically, the system controller 530 switches the flow path switching valve 514 of the LC unit 510 to the first state described above. As a result, the mobile phase in the mobile phase container 511 is sent directly to the ionization unit 521 of the MS unit 520 without passing through the column 515. Therefore, the sample added to the mobile phase is also sent directly to the ionization unit 521 of the MS unit 520 without passing through the column 515. Then, mass analysis of the sample is performed in the MS unit 520.

[0022] In one implementation example, a mobile phase in flow injection analysis is a 10:90 mixture of ultrapure water and methanol. The flow rate in the LC unit 510 is 0.1 mL / min before sample injection, gradually changed to 0.05 mL / min 0.1 minutes after sample injection, gradually changed to 0.1 mL / min between 0.1 and 0.65 minutes, gradually changed to 1 mL / min between 0.65 and 1 minute, and then maintained at 1 mL / min. The sample injection volume is 1 μL.

[0023] In the flow injection analysis, the analysis conditions in the MS section 520 are, for example, as follows:

[0024] Ionization: ESI (positive, negative mode) Interface voltage: 3 kV (ion guide 33), -2 kV (ion guide 36) Nebulizer gas flow rate: 2.0 L / min Drying gas flow rate: 5.0 L / min Heating gas flow rate: 7.0 L / min Desolvation temperature: 450°C DL temperature: 200°C In step S26, the user causes the analysis system 500 to process the data of the analysis results from step S24. Thereafter, the processing of FIG. 3 ends.

[0025] In one implementation example, in step S26, the control unit 540 may display the results of the data processing on a display. In one implementation example, a mass spectrum of the polymer material is created by the data processing in step S26. The control unit 540 may include a memory, and the created mass spectrum may be stored in the memory. When a mass spectrum is created for each of multiple types of polymer materials as described above, the control unit 540 may perform statistical analysis using the mass spectra of the multiple types of polymer materials as the data processing in step S26.

[0026] In this embodiment, analysis of the polymeric material does not require chromatographic analysis, which can shorten the analysis time of the polymeric material. Furthermore, the sample is introduced into the mass spectrometer according to the flow injection method.

[0027] When samples are introduced into a mass spectrometer using the flow injection method, many samples can be processed in a short time, improving the throughput of the analysis system 500. Furthermore, compared to when samples are introduced into the MS unit 520 using a syringe pump, the amount of sample injected into the MS unit 520 can be reduced, thereby reducing contamination of the MS unit 520. Furthermore, sample injection is automated by injecting samples using the autosampler (injector 513) of the LC unit 510. Therefore, the amount of work required by the user is reduced, especially when there are multiple samples to be analyzed.

[0028] 3 includes data processing of the analysis results of the samples. As the data processing, multivariate analysis may be performed using the results of mass spectrometry of each of a plurality of types of samples.

[0029] Fig. 4 is a diagram showing an example of a screen displaying the results of the multivariate analysis, which includes a score plot and a loading plot.

[0030] In the example of Figure 4, four types of food containers (tofu film, tofu pack, plastic wrap, and bean sprout bag) were each analyzed five times. That is, Figure 4 shows the results of multivariate analysis using the results of a total of 20 analyses. Each of the 20 analytical data used in the multivariate analysis includes the type of food container and the analytical results (m / z values ​​and peak intensities of peaks contained in the mass spectrum). That is, the results of Figure 4 were generated using 20 mass spectra obtained for each of the 20 analyses.

[0031] In the score plot of Figure 4, it can be seen that the plots form clusters for each type of food container. More specifically, in the score plot, the plots for tofu film form a cluster in the upper left, the plots for tofu packs form a cluster in the upper right, the plots for plastic wrap form a cluster in the lower left, and the plots for bean sprout bags form a cluster in the lower right.

[0032] In the loading plot of FIG. 4, peaks characteristic of each food container can be identified based on the m / z and peak intensity of the 67 peaks contained in the 20 mass spectra, based on the score plot of FIG.

[0033] 5 is a diagram showing another example of a screen displaying the results of multivariate analysis. In displaying the results of data processing, when a specific operation is performed on a plot in the loading plot (e.g., placing the cursor on the plot), the m / z value corresponding to that plot may be displayed. In the example of FIG. 5, in response to a specific operation being performed on plot P1, information "m / z_663.52" including the m / z value corresponding to plot P1 is displayed.

[0034] Fig. 6 is a diagram showing yet another example of a screen displaying the results of multivariate analysis. When the results of data processing are displayed, if a specific operation is performed on a plot in the loading plot (for example, by right-clicking the mouse on the plot), an enlarged view of the vicinity of the plot may be displayed as a pop-up. Fig. 7 is a diagram showing an enlarged view of a portion of the loading plot in Fig. 6.

[0035] 7 shows a pop-up screen that appears when a specific operation (e.g., dragging the portion of the loading plot you want to enlarge) is performed on plot P3 in the loading plot of FIG. 6. The pop-up screen displays plot P3 and plots in the vicinity of plot P3. The pop-up screen also displays the m / z value (646.63) corresponding to plot P3.

[0036] According to the display manner of the data processing results described above with reference to Figures 5 to 7, the user can view the loading plot and recognize the m / z values ​​corresponding to peaks that are considered to be characteristic of a certain type of food container.

[0037] Aspects It will be understood by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0038] (Item 1) An analytical method according to one aspect may be a method for analyzing a polymeric material, and may include: ionizing a sample in which the polymeric material is dissolved by electrospray ionization in a mass spectrometer; and performing mass analysis of the ionized sample in the mass spectrometer.

[0039] According to the analytical method described in paragraph 1, the analysis time for analyzing a polymer material can be shortened. (paragraph 2) In the analytical method described in paragraph 1, the sample may be introduced into the mass spectrometer according to a flow injection method.

[0040] According to the analytical method described in paragraph 2, the sample can be easily introduced into a mass spectrometer. (Item 3) The analytical method described in paragraph 1 or 2 may further include preparing the sample using tetrahydrofuran as a solvent for dissolving the polymer material.

[0041] According to the analytical method described in paragraph 3, the polymeric material to be analyzed can be easily dissolved in the sample.

[0042] (Item 4) The analytical method according to any one of items 1 to 3 may further comprise preparing the sample by dividing the polymer material into small pieces.

[0043] According to the analytical method described in the fourth aspect, the polymeric material to be analyzed is more reliably contained in the sample.

[0044] (Item 5) The analytical method according to any one of items 1 to 4 may further comprise analyzing the mass spectrum obtained in the mass analysis by multivariate analysis.

[0045] According to the analytical method described in item 5, it becomes easy to classify polymeric materials and to discover characteristic components in polymeric materials.

[0046] (Item 6) In the analytical method described in Item 5, performing mass analysis of the sample may include performing mass analysis of each of a plurality of the samples prepared for each of a plurality of types of polymeric materials, and the multivariate analysis may utilize a plurality of mass spectra obtained for each of the plurality of the samples.

[0047] According to the analysis method described in Section 6, the accuracy of classification is improved and the reliability of the characteristic components discovered is also improved.

[0048] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above-described embodiments, and is intended to include all modifications within the meaning and scope of the claims. Furthermore, it is intended that each technique in the embodiments can be implemented alone or, if necessary, in combination with other techniques in the embodiments to the extent possible.

[0049] 20 ionization chamber, 21 first intermediate vacuum chamber, 22 second intermediate vacuum chamber, 23 analysis chamber, 29 mass separation unit, 201 electrospray ionization probe, 202 heated capillary, 211, 221, 233 ion guide, 235 ion detector, 500 analysis system, 510 LC unit, 520 MS unit, 511 mobile phase container, 512 liquid pump, 513 injector, 514 flow path switching valve, 515 column, 516 column oven, 521 ionization unit, 530 system controller, 540 control unit.

Claims

1. A method for analyzing a polymeric material, comprising: performing ionization by electrospray ionization on a sample in which the polymeric material is dissolved in a mass spectrometer; and performing mass analysis of the ionized sample in the mass spectrometer.

2. The analytical method according to claim 1, wherein the sample is introduced into the mass spectrometer according to a flow injection method.

3. The analytical method according to claim 1 or 2, further comprising preparing the sample using tetrahydrofuran as a solvent for dissolving the polymeric material.

4. The analytical method according to claim 1 or 2, further comprising preparing the sample by subdividing the polymeric material.

5. The analytical method according to claim 1 or 2, further comprising analyzing the mass spectrum obtained in the mass spectrometry by multivariate analysis.

6. The analytical method of claim 5, wherein performing mass analysis of the sample includes performing mass analysis of each of a plurality of the samples prepared for each of a plurality of types of polymeric materials, and the multivariate analysis utilizes a plurality of mass spectra obtained for each of the plurality of the samples.

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