JP2019124610A - Chromatograph mass spectroscope - Google Patents

Abstract

To determine an appropriate quantitative ion so that high quantitativity is obtained for all target compounds when a plurality of target compounds are collectively analyzed.SOLUTION: A pre-analysis execution control unit 41 executes GC/MS analysis on a standard sample including a plurality of target compounds with a known concentration, while performing SIM measurement aimed at a typical m/z for each target compound. A signal strength estimation unit 321 estimates, for each target compound, signal strength in an unexecuted m/z from a measured signal strength value and standard spectrum information stored in a mass spectrum information storage unit 31. A quantitative/confirmation ion selection unit 322 determines, on the basis of a signal strength value in each m/z per target compound, an m/z where strength is maximum as a quantitative ion for a target compound for which sensitivity is prioritized. For the other target compounds, an m/z indicating as high signal strength as possible in a range lower than the signal strength of quantitative ion of a compound for which strength is prioritized, is determined as a quantitative ion.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gas chromatograph mass spectrometer (GC-MS) combining a gas chromatograph (GC) and a mass spectrometer (MS) or a liquid chromatograph combining a liquid chromatograph (LC) and a mass spectrometer (MS) The present invention relates to a chromatograph mass spectrometer such as a graph mass spectrometer (LC-MS). The present invention is particularly suitable for multi-component simultaneous analysis in which quantitative analysis of a large number of compounds contained in a sample is collectively performed using a chromatograph mass spectrometer.

  In recent years, multi-component simultaneous analysis using chromatograph mass spectrometer such as GC-MS or LC-MS is common in various fields such as inspection of pesticide residue in food, inspection of pollutant in environmental water, or drug toxicological inspection. It has been done.

  When measuring a target compound contained in a sample using a chromatograph mass spectrometer, quantitative ions (also called target ions) and confirmation ions (reference ions and reference ions) to be targets in mass spectrometry for each target compound Is called in advance. Then, after the sample is injected into the chromatograph, the quantitative ion of the target compound is adjusted according to the time (that is, the retention time) at which each target compound leaves the chromatograph column and is introduced into the mass spectrometer at the subsequent stage. And signal intensity values for the identified ions are obtained with a mass spectrometer. Based on the data thus obtained, extract ion chromatograms (also called mass chromatograms) for quantitative ions and confirmation ions are created, and the ratio of peak areas on the chromatogram (or the ratio of heights) is used. The target compound is identified. In addition, a quantitative value such as the concentration of the identified target compound is calculated in light of a calibration curve which is obtained in advance in the area value (or height value) of the peak on the extraction ion chromatogram in the quantitative ion.

  In general, a mass-to-charge ratio corresponding to a peak at which the signal intensity is maximum in a typical mass spectrum of the compound is selected as the quantitative ion (see, for example, Patent Document 1). This is to improve the accuracy of quantification by performing the analysis with as high sensitivity as possible even when the concentration of the compound contained is low. In addition, as the confirmation ion, an appropriate mass-to-charge ratio different from that of the quantification ion, which characterizes the compound, is selected.

  In preparing a calibration curve to be referred to for quantification, a standard sample containing the target compound at a known concentration is used. When there are a plurality of target compounds, a standard sample containing the plurality of compounds at substantially the same concentration is usually measured by the chromatograph mass spectrometer, and the extraction ion chromatograph of quantitative ion and confirmation ion is performed for each target compound. Gram data is acquired. Depending on the type of compound, the ionization efficiency and the fragment aspect (usually when using an ion source by electron ionization method in GC-MS), etc. differ, so even if the concentrations of a plurality of compounds in the sample are the same. A considerable difference may occur in the signal intensity value of the maximum intensity peak in the mass spectrum corresponding to each of the plurality of compounds.

  Since the gain of the ion detector used in the mass spectrometer can be adjusted by the voltage applied to the detector (hereinafter referred to as the detector voltage), the signal intensity value of the peak on the mass spectrum is adjusted by the detector voltage It is possible. However, if the gain of the ion detector is too high, the output of the detector will be saturated. Therefore, when analyzing a large number of target compounds contained in a standard sample at one time, adjust the detector voltage so that the signal with the highest quantitative ion intensity among all the target compounds contained in the sample is not saturated. It is common to do.

  FIG. 10 (a) is a chromatogram obtained when a standard sample containing two compounds A and B is analyzed (exactly, an extracted ion chromatogram of quantified ions respectively corresponding to the compounds A and B was synthesized Thing) is an example. In this case, the detector voltage is adjusted so that the detection output of compound A having a relatively high signal intensity of quantitative ions is not saturated, but the detection output of compound B having a relatively low signal intensity of quantitative ions for that purpose Is quite low. If the calibration curve is prepared in such a state, the quantitative accuracy of the compound B may be lowered. On the other hand, when the detector voltage is adjusted so that the signal intensity of the quantified ion of compound B becomes sufficiently large, the detection output of compound A becomes saturated as shown in FIG. 10 (b). It is not possible to create an accurate calibration curve for

JP 2014-134385 A (paragraph [0003])

  As described above, in the conventional chromatograph mass spectrometer, when analyzing a plurality of target compounds contained in a standard sample at one time and trying to create a calibration curve based on the results, the signal intensity of quantitative ions is obtained. There has been a problem that the accuracy of quantification of compounds having a relatively low value is low.

  The present invention has been made in view of these problems, and it is an object of the present invention to saturate the detection output of any compound when analyzing a plurality of compounds in a sample at one time. It is an object of the present invention to provide a chromatograph mass spectrometer capable of selecting a quantitative ion and a confirmatory ion which can detect a compound without any problem and with as high sensitivity as possible.

The present invention made to solve the above problems includes a chromatograph unit that separates compounds in a sample in the time direction, and a mass spectrometry unit that detects each of the separated compounds, and is defined for each target compound. In a chromatograph mass spectrometer that quantifies the target compound using the quantified ion,
a) A spectral information storage unit in which standard spectral information, which is a standard mass spectrum or a standard signal intensity value at a plurality of mass-to-charge ratios or a ratio of the signal intensity values, is stored for each target compound;
b) Control the operation of the chromatograph unit and the mass spectrometry unit so that a sample containing a plurality of target compounds at known concentrations is analyzed as an ion of a specific mass-to-charge ratio defined for each compound as a mass spectrometry target Analysis control unit,
c) measured signal strength values for specific mass-to-charge ratios obtained for each target compound under the control of the analysis control unit, and standard spectral information for each target compound stored in the spectral information storage unit A signal strength value estimating unit for estimating a signal strength value for the predetermined concentration at a mass-to-charge ratio other than the specific mass-to-charge ratio, for each target compound based on
d) As a quantitative ion based on signal strength values at a plurality of mass-to-charge ratios including the signal strength value of the actual measurement and the signal strength value estimated by the signal strength value estimation unit obtained for each target compound A quantitative ion selection unit for selecting a mass-to-charge ratio to be used for each target compound;
It is characterized by having.

  In the present invention, the chromatograph part is either a gas chromatograph or a liquid chromatograph. The mass analysis unit may be, for example, a single type mass spectrometer such as a quadrupole mass spectrometer, or MS / MS analysis such as a triple quadrupole mass spectrometer or a quadrupole-time-of-flight mass spectrometer. May be any mass spectrometer capable of In the former case, the target of mass spectrometry is an ion having a specific mass-to-charge ratio, but in the latter case, the target of mass spectrometry is a combination of a mass-to-charge ratio of a specific precursor ion and a mass-to-charge ratio of a specific product ion That is, MRM (multiple reaction monitoring) transition. That is, in this case, for example, the above-mentioned "specific mass-to-charge ratio" means "specific MRM transition".

  In the present invention, the spectral information storage unit is a standard mass spectrum, that is, spectral information in which the mass-to-charge ratio value is continuous, or a standard in a plurality of mass-to-charge ratios for each target compound to be quantified. Either the signal strength values or the ratio of the signal strength values, that is to say the spectral information in which the mass to charge ratio values are discrete, are stored beforehand. Preferably, the spectrum information is acquired by the apparatus itself or another apparatus of the same model. The reason is that the spectral pattern of the spectral information for the same compound is more consistent with the spectral pattern obtained at the time of measurement.

  The analysis control unit performs analysis on a standard sample containing a plurality of target compounds at known concentrations, and the chromatography unit and mass analysis unit, specifically, in the case of GC-MS, a sample injection unit of a gas chromatograph or a column oven Control the operation of the mass spectrometer ion source, mass separator, detector, etc. At this time, in the mass spectrometer, the mass-to-charge ratio of the ion to be analyzed is switched according to the retention time so that an ion having a specific mass-to-charge ratio defined for each target compound is used as a mass analysis target. In this analysis, it is recommended to use a standard sample containing the target compound at the highest concentration among the standard samples used in preparing the standard curve. Also, in general, the concentrations of a plurality of target compounds contained in a standard sample are often the same, but here, they may not be the same if their respective concentrations are known. The mass-to-charge ratio, which is the target of mass spectrometry, may be a mass-to-charge ratio that maximizes the signal intensity for each target compound, but is not limited thereto.

  If the signal strength value at a specific mass-to-charge ratio is determined for each target compound by the above measurement, the signal strength value estimation unit refers to the standard spectral information for each target compound stored in the spectral information storage unit, Specifically, referring to the ratio of signal intensity values among a plurality of mass-to-charge ratios determined from the standard spectral information, from the actually measured signal intensity value at a particular mass-to-charge ratio, the mass other than the particular mass-to-charge ratio Signal strength values for predetermined concentrations in the charge ratio are estimated. Thereby, for each target compound, signal intensity values of a plurality of main peaks for a predetermined concentration can be roughly determined, and signals among different target compounds as well as comparison of a plurality of signal intensity values in one target compound. Comparison of intensity values is possible.

Therefore, the quantitative ion selection unit is used for quantitative ions by comparing signal intensity values at a plurality of mass-to-charge ratios and comparing signal intensity values at a plurality of mass-to-charge ratios among the target compounds for each target compound. The mass-to-charge ratio is selected for each target compound.
Specifically, for example, in the first target compound of the plurality of target compounds, the signal strength of the first target compound that emphasizes the detection sensitivity most becomes relatively larger than the signal strength of the other target compounds. Select the mass-to-charge ratio of the quantitation ion. Then, the mass-to-charge ratio of which the signal intensity is lower than the signal intensity of the quantified ion of the first object compound may be selected as the quantified ion of the object compound other than the first object compound. Alternatively, the mass-to-charge ratio at which the signal intensity in the first target compound is maximized is selected as the mass-to-charge ratio of quantitative ions of the first target compound, and as the quantitative ions of the target compounds other than the first target compound, the first target compound A mass-to-charge ratio may be selected which exhibits as low a signal strength as possible even when it is higher than the signal strength of the quantitation ion.

  As a result, in the same standard sample, the signal intensities for the quantified ions of the plurality of target compounds can not be largely different, and the signal intensities for the quantified ions of the first object compound that emphasizes detection sensitivity become as high as possible. The mass-to-charge ratio of quantified ions of each target compound can be determined.

  In the present invention, the quantitative ion selection unit may be configured to select a mass-to-charge ratio of confirmation ions as well as quantitative ions for each target compound. As a mass-to-charge ratio of confirmation ions, for example, a mass-to-charge ratio showing the next highest signal intensity of the quantitative ions may be selected.

In the chromatograph mass spectrometer according to the present invention, preferably,
The mass analysis unit includes an ion detector whose gain changes in accordance with an applied voltage,
Among the quantitative ions selected respectively by the quantitative ion selection unit for a plurality of target compounds, the applied voltage to the detector is determined so that the one showing the largest signal intensity is not saturated at the output of the ion detector. The control unit may be further provided.

  According to this configuration, after the quantitative ion is determined for each target compound to be quantified as described above, when the standard sample containing the target compounds is analyzed to create a calibration curve, the quantitative determination of any target compound The detection output for ions can also be prevented from saturation. In addition, by making the gain as high as possible within the range where the maximum signal intensity is not saturated at the output of the ion detector and making the gain as high as possible, it is possible to create a highly quantitative calibration curve for the target compound that emphasizes detection sensitivity. .

  According to the present invention, when analyzing a plurality of target compounds in a sample at one time, any target compound can be detected with as high sensitivity as possible without saturation of its detection output. Certain quantitative ions can be selected. As a result, a highly accurate calibration curve can be created for any target compound, and high quantitativity can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram of GC-MS which is 1st Example of this invention. The flowchart which shows the procedure of determination / determination ion determination processing in GC-MS of 1st Example. The figure which shows the example of the extraction ion chromatogram with respect to two compounds A and B of the same density | concentration. The figure which shows an example of the standard spectrum information with respect to two compounds A and B in GC-MS of 1st Example. The figure which shows the estimated value of the signal strength in each mass charge ratio of the compounds A and B about the same density | concentration based on the standard spectrum information and measurement result which were shown in FIG. The figure which shows the example of selection of the fixed_quantity ion and confirmation ion based on the result shown in FIG. The figure which shows the other selection example of the fixed_quantity ion and confirmation ion based on the result shown in FIG. The schematic block diagram of GC-MS which is 2nd Example of this invention. The figure which shows an example of the standard spectrum information with respect to two compounds A and B in GC-MS of 2nd Example. It is a figure which shows an example of the chromatogram obtained when analyzing the standard sample containing the compound A of the same density | concentration, B, and (a) is a detector voltage so that the detection output of the compound A may become as large as possible. (B) when the detector voltage is adjusted so as to be as large as possible within the range in which the detection output of compound B is not saturated.

[First embodiment]
Hereinafter, a first embodiment of a chromatograph mass spectrometer according to the present invention will be described in detail with reference to the attached drawings.
FIG. 1 is a schematic block diagram of a gas chromatograph mass spectrometer (GC-MS) according to a first embodiment.

  The GC-MS includes a GC unit 1, an MS unit 2, a data processing unit 3, a control unit 4, a main control unit 5, an input unit 6, and a display unit 7. The GC unit 1 comprises a sample vaporization chamber 10 for evaporating a small amount of liquid sample, a microsyringe 11 for injecting a liquid sample into the sample vaporization chamber 10, a column 13 for separating compounds in the sample in a time direction, and a column 13 And a column oven 12 for temperature control. The MS unit 2 includes an ion source 21 for ionizing a target compound by an electron ionization method, and a quadrupole mass filter 22 composed of four rod electrodes in a chamber 20 evacuated by a vacuum pump (not shown). And an ion detector that outputs a detection signal according to the amount of ions that have passed through the quadrupole mass filter and entered. The ion detector 23 is composed of, for example, a combination of a conversion dynode and an electron multiplier, and the gain of the ion detector 23 is adjusted by the voltage (detector voltage) applied to the electron multiplier.

  A detection signal from the ion detector 23 is converted into digital data by an analog-to-digital converter (ADC) 24 and input to the data processing unit 3. The data processing unit 3 includes functional blocks such as a mass spectrum information storage unit 31, a quantitative / confirmation ion determination processing unit 32, a calibration curve creation unit 33, a calibration curve storage unit 34, and a quantitative processing unit 35.

  The mass spectrum information storage unit 31 is a standard mass spectrum when mass spectrometry is performed in the MS unit 2 of the apparatus with respect to a plurality of target compounds to be quantified, or a plurality of peaks actually observed. Spectral information in which the relationship between the mass-to-charge ratio and the signal intensity value of the peak is summarized is stored in advance. Since the information required in the apparatus of this embodiment is the ratio of the mass-to-charge ratio of a plurality of peaks to the signal intensity value of the plurality of peaks in each compound, the signal intensity value is, for example, 100 with the maximum intensity. The intensity ratio may be% (see FIG. 4).

The quantitative / confirmation ion determination processing unit 32 includes a signal intensity estimation unit 321 and a quantitative / confirmation ion selection unit 322, and quantitative ions and confirmation ions to be used for quantitative analysis by the characteristic processing described later for each target compound. decide.
The calibration curve creation unit 33 creates a calibration curve for each target compound based on the analysis result of the standard sample with the quantitative ion determined in the quantitative / confirmation ion determination processing unit 32 as a target. The calibration curve storage unit 34 stores the created calibration curve. The quantitative processing unit 35 calculates the concentration for each target compound in light of the calibration curve stored in advance in the calibration curve storage unit 34 of the analysis result of the sample containing the target compound of unknown concentration.

  The control unit 4 controls the operations of the GC unit 1, the MS unit 2, and the data processing unit 3, and includes functional blocks such as the pre-analysis execution control unit 41, the standard sample analysis control unit 42, and the normal sample analysis control unit 43. Including. The main control unit 5 carries a user interface through the input unit 6 and the display unit 7 and performs overall control of the entire apparatus.

  The data processing unit 3, the control unit 4, and the main control unit 5 execute control / processing software pre-installed on the computer using the personal computer or a more advanced workstation as hardware resources on the computer. Thus, each configuration can be realized to realize each function. In this case, the input unit 6 is a keyboard or pointing device (mouse or the like) attached to the computer, and the display unit 7 is a display monitor of the computer.

  Next, the quantitative / confirmation ion determination process in GC-MS of the present embodiment will be described in detail. FIG. 2 is a flowchart showing the procedure of this quantitative / confirmation ion determination process. 3 to 7 are diagrams used to explain this process.

  When creating a calibration curve, a standard sample containing the target compound to be quantified at a known concentration is used. Here, in order to determine the quantitation ion and the confirmation ion, the highest concentration a among the standard samples a Therefore, use a standard sample containing the target compound. However, this is not essential, and any standard sample containing a plurality of target compounds at known concentrations may be used.

  For example, in response to a user instruction to execute quantitative ion determination processing from the input unit 6, the pre-analysis execution control unit 41 selects one representative mass-to-charge ratio for each target compound to be quantified which is set in advance. (Step S1). Generally, it is sufficient to select a mass-to-charge ratio that maximizes the signal strength. For example, the spectrum information corresponding to each target compound stored in the mass spectrum information storage unit 31 is read out, and the signal strength for each target compound It suffices to search for the mass-to-charge ratio at which Of course, the user may set the mass-to-charge ratio to be used for each target compound.

  Now, as an example, consider the case where the target compound is two, A and B. FIG. 4 is a view showing an example of standard spectral information for two compounds A and B. Compound A has the largest signal intensity at m / z 115, and Compound B has the largest signal intensity at m / z 121. Therefore, in step S1, m / z 115 is selected as a representative mass-to-charge ratio of compound A, and m / z 121 is selected as a representative mass-to-charge ratio of compound B.

  Next, the preliminary analysis execution control unit 41 introduces each part of the GC unit 1 and the MS unit 2 so as to introduce the prepared standard sample having the concentration a into the sample vaporization chamber 10 of the GC unit 1 and execute GC / MS analysis. Control. At this time, in the MS unit 2, the timing at which the target compound temporally separated in the GC unit 1 is introduced, that is, the selected ion monitoring (SIM) targeting ions of the mass-to-charge ratio selected in step S1 in the holding time. ) Is detected (step S2). The detection signal obtained by the ion detector 23 in the GC / MS analysis is digitized by the ADC 24 and input to the quantitative / confirmation ion determination processing unit 32.

  FIG. 3 shows an example of an extracted ion chromatogram obtained for compound A and compound B in a standard sample having a concentration a. In the figure, ta is the retention time of Compound A, and tb is the retention time of Compound B. The curves shown by dotted lines in FIG. 3 are extracted ion chromatograms assuming that ions at m / z 100 and m / z 77 are detected, and are not actually created chromatograms. As shown in FIG. 3, although the concentration is the same here, there is a large difference in peak signal intensity between compound A and compound B. As described above, this is due to, for example, the difference in ion efficiency, or the difference in the aspect of fragments during ionization.

  Next, in the quantitative / confirmation ion determination processing unit 32, the signal intensity estimation unit 321 determines, for each target compound, the signal intensity value at a representative mass-to-charge ratio obtained by measurement and the standard spectrum read out from the mass spectrum information storage unit 31. Based on the information, the signal intensity value at each mass-to-charge ratio for the sample of concentration a is estimated (step S3).

  FIG. 5 is a diagram showing estimated values of signal strength at respective mass-to-charge ratios of the compounds A and B at the same concentration based on the standard spectrum information and the measurement results shown in FIG. In this example, the signal intensity of m / z 115 in the compound A and the signal intensity of m / z 121 in the compound B are actual measurement results. Now, it is assumed that the measured signal strengths are 10000 and 200, respectively. The standard spectrum information shown in FIG. 4 shows the ratio of the signal intensity at each mass-to-charge ratio, and since this ratio should be almost irrelevant to the concentration, the ratio of the signal intensity of the actual measurement to the signal intensity is Signal strength at mass-to-charge ratio not measured can be estimated. Thus, as shown in FIG. 5, for each target compound, signal intensities at all mass-to-charge ratios at which major peaks are observed can be determined as estimated values or actual values.

In the quantitative / confirmation ion determination processing unit 32, the quantitative / confirmation ion selection unit 322 uses the relationship between the mass-to-charge ratio obtained in step S3 and the signal intensity value (measured value or estimated value) as follows. The mass-to-charge ratio of the quantitation ion and the confirmation ion is selected for each target compound.
First, attention is focused on the target compound with emphasis on sensitivity designated in advance by the user. Here, it is assumed that the compound B is a target compound with emphasis on sensitivity. Among signal intensity values at each mass-to-charge ratio relative to compound B, a mass-to-charge ratio showing the largest signal intensity value and a mass-to-charge ratio showing the next highest signal intensity value are searched. Here, for the compound B, the mass-to-charge ratio showing the largest signal strength value is m / z 121 (signal strength value is 200), and the mass-to-charge ratio showing the next highest signal strength value is m / z 77 (the signal strength value is 140). Therefore, as shown in FIG. 6, these are selected as quantitative ions and confirmation ions (step S4).

  Next, for the other compound, here, compound A, a mass-to-charge ratio that exhibits as high a signal strength as possible is selected as the mass-to-charge ratio of the quantification ion within the range not exceeding the signal intensity value of the quantification ion of the target compound with emphasis on sensitivity. Do. In this example, among signal intensity values at each mass-to-charge ratio with respect to compound A, m / z 66 (signal intensity value is 180) is the highest within the range not exceeding the signal intensity value (200) of the quantified ion of compound B. ). Furthermore, the next highest signal strength value is m / z 72 (signal strength value is 120). Therefore, m / z 66 and m / z 77 are respectively selected as mass-to-charge ratio values of the quantified ion and the confirmed ion of the compound A (step S5). In this example, although there are only two compounds, even if the number of compounds is large, one target compound of sensitivity is selected in the same manner, and after a quantitative ion and a confirmation ion of the target compound are selected. Then, quantitative intensities and confirmation ions of other target compounds may be sequentially selected by comparing signal intensity values.

  However, there may be a case where there is no mass-to-charge ratio that satisfies the condition of the process in step S5. FIG. 7 shows the results of determination of signal intensities at a plurality of mass-to-charge ratios for compounds A and B, as in FIG. In this case, the mass-to-charge ratio showing the maximum signal strength value for compound B is m / z 152 (signal strength value is 150), and the mass-to-charge ratio showing the next highest signal strength value is m / z by the process of step S4 It is determined that 121 (signal strength value is 120). This makes it possible to determine the quantitation ion and confirmation ion of the compound B, which is a compound that places importance on sensitivity, but the signal intensity of the compound A exceeds the signal intensity of the quantitation ion of the compound B. Can not determine the quantitation ion and the confirmation ion.

  Therefore, in the case where there is a compound in which two or more mass-to-charge ratios in which the signal intensity value is lower than the maximum signal intensity value of the target compound with emphasis on sensitivity exist in the target compounds other than the object compound with emphasis on sensitivity, Go to S7. On the other hand, when it is determined No in step S6, since the quantified ions and the confirmed ions have been determined for all the target compounds, the process is ended as it is.

  When the process proceeds to step S7, the quantification / confirmation ion selection unit 322 determines that there are two mass-to-charge ratios whose signal intensity value is lower than the maximum signal intensity value of the target compound with emphasis on sensitivity (total number of quantified ions and confirmation ions ) The mass-to-charge ratio with the lowest possible signal intensity value is selected as the mass-to-charge ratio of the quantification ion and the confirmation ion for the target compound determined to be absent as described above. That is, in the case of the example shown in FIG. 7, the low signal strength value for compound A is m / z 66 (signal strength value is 180) and m / z 72 (signal strength value is 160). Although the signal intensity values are larger than the signal intensity value 150 of the quantified ion of the compound B, they are selected as the quantified ion and the confirming ion of the compound A.

  In this way, quantitation ions and confirmation ions can be determined for all target compounds. Information on the determined mass-to-charge ratio of the quantitative ion and the confirmatory ion is sent to the standard sample analysis control unit 42 of the control unit 4 and stored in the standard sample analysis control unit 42 as one of the analysis conditions. The quantified ions and the confirmed ions thus determined have relatively uniform signal intensity values for the same concentration regardless of the type of the target compound. In particular, it is possible to avoid that the target compound for which sensitivity is important is extremely low in signal intensity value relative to other target compounds.

When preparing a calibration curve in the present embodiment GC-MS, standard samples having different concentrations (for example, three or five) are prepared. The standard sample analysis control unit 42 controls the respective units of the GC unit 1 and the MS unit 2 so as to sequentially execute the GC / MS analysis on a plurality of prepared standard samples. At this time, in the MS unit 2, detection in the SIM mode in which quantitative ions and confirmation ions are targeted is performed at the retention time of each target compound.
When the standard sample is subjected to GC / MS analysis, the standard sample analysis control unit 42 does not saturate the signal intensity of the target compound showing the maximum signal intensity when analyzing the standard sample of the highest concentration. The detector voltage may be adjusted to be as large as possible in the range.

  The calibration curve creation unit 33 creates an extraction ion chromatogram based on the data obtained by the above-mentioned GC / MS analysis, and calculates the peak area value on the chromatogram for each target compound. Then, a calibration curve indicating the relationship between the concentration and the peak area value is created for each target compound. Then, the created calibration curve is stored in the calibration curve storage unit 34.

  In quantitative analysis of a target compound whose concentration is unknown, the sample analysis control unit 43 normally performs GC / MS analysis on a sample containing the target compound of unknown concentration. Control each part. At this time, in the MS unit 2, detection in the SIM mode in which quantitative ions and confirmation ions are targeted is performed at the retention time of each target compound. The quantitative processing unit 35 creates an extracted ion chromatogram based on the data obtained by the above-mentioned GC / MS analysis, and calculates the peak area value on the chromatogram for each target compound. Then, the concentration is calculated from the actually measured peak area value with reference to the calibration curve stored in the calibration curve storage unit 34 for each target compound. Thereby, the concentration of each target compound in the sample can be calculated.

  In the above description, although there are one confirmation ion, a plurality of confirmation ions having different mass-to-charge ratios with respect to one compound are often used. Even in such a case, it is clear that quantitative ions and confirming ions can be determined for each target compound only by partially changing the contents of the above-mentioned treatment according to the increase in the number of confirming ions.

Second Embodiment
In the GC-MS of the first embodiment, the MS unit 2 is a single type quadrupole mass spectrometer, but as the second embodiment of the present invention, a mass spectrometer capable of MS / MS analysis is used. Next, the GC-MS that has been used will be described. FIG. 8 is a schematic block diagram of the GC-MS according to the second embodiment. In the figure, the same code | symbol is attached | subjected to the component which is the same as that of GC-MS of 1st Example, or it corresponds.

  In this GC-MS, the MS unit 200 includes an ion source 21, a front quadrupole mass filter 25, and a multipole ion guide 27 in the interior of a chamber 20 evacuated by a vacuum pump (not shown). The collision cell 26, the rear stage quadrupole mass filter 28, and the ion detector 23 are provided. The collision gas, which is an inert gas such as argon or nitrogen, is continuously or intermittently supplied to the inside of the collision cell 26, and ions having a specific mass-to-charge ratio that has passed through the front quadrupole mass filter 25 ( The precursor ions) collide with the collision gas in the collision cell 26 and dissociate. The various product ions generated thereby are introduced into the second-stage quadrupole mass filter 28, and only the product ions having a specific mass-to-charge ratio pass through the second-stage quadrupole mass filter 28 to reach the ion detector 23. .

  In this quantitative analysis in GC-MS, an MRM measurement in which the mass-to-charge ratio of precursor ions and the mass-to-charge ratio of product ions are fixed is used. Therefore, neither the quantified ion nor the confirmed ion in this case is the mass-to-charge ratio of one ion, but is an MRM transition which is a combination of the mass-to-charge ratio of the precursor ion and the mass-to-charge ratio of the product ion.

  A data processing unit 300 corresponding to the data processing unit 3 in FIG. 1 includes an MS / MS spectrum information storage unit 301 instead of the mass spectrum information storage unit 31. A control unit 400 corresponding to the control unit 4 in FIG. 1 includes functional blocks such as a pre-analysis execution control unit 401, a standard sample analysis control unit 402, and a normal sample analysis control unit 403.

The MS / MS spectrum information storage unit 301 is an MS / MS spectrum in which the relationship between a plurality of MRM transitions for which peaks are actually observed and signal intensity values of the peaks is summarized for each of a plurality of target compounds to be quantified. Information is stored in advance.
FIG. 8 is a diagram showing an example of standard MS / MS spectrum information for two compounds A and B stored in the MS / MS spectrum information storage unit 301. As shown in FIG. In the figure, CE is a value of collision energy which is one of the conditions of collision-induced dissociation in the collision cell 26. Different MRM transitions also differ in optimal collision energy (usually with the highest dissociation efficiency). Therefore, in this case, the collision energy value optimum for each MRM transition is associated in advance, and this information can be used to appropriately adjust the collision energy according to the MRM transition at the time of actual MRM measurement.

  The procedure of quantitative / confirmation ion determination processing in GC-MS of this embodiment is basically the same as that of GC-MS of the first embodiment. The difference is that in the GC-MS of the first embodiment, signal intensity values for ions having a specific mass-to-charge ratio are determined by SIM measurement, whereas in the GC-MS of this embodiment, they are specified by MRM measurement. Determining a signal strength value for a product ion having an MRM transition of and the collision energy is adjusted by the MRM transition.

  Specifically, in the example of FIG. 8, the compound A has the maximum signal intensity in the MRM transition of m / z 115 of the precursor ion and m / z 100 of the product ion, and the compound B has m / z 206 of the precursor ion The signal strength is maximum at the m / m 191 transition of the product ion m / z 191. Accordingly, in step S1 in FIG. 2, m / z 115> 100 is selected as a representative MRM transition of compound A, and m / z 206> 191 is selected as a representative MRM transition of compound B. Then, in step S2, an MRM measurement targeting these MRM transitions is performed. At this time, all collision energy is set to 8 [eV]. Similarly, for the step S3 and subsequent steps in FIG. 2, appropriate quantitative ions and confirming ions can be determined for each target compound by proceeding with the process by replacing the mass-to-charge ratio with the MRM transition.

  In general, in the MRM measurement, since the operation of ion dissociation by collision induced dissociation and the operation of selection of product ions are added to the SIM measurement, the amount of ions reaching the ion detector 23 is considerably smaller than that in the SIM measurement. Therefore, as described above, the effect of sensitivity improvement by adjusting the detector voltage and increasing the gain of the ion detector 23 becomes more remarkable.

  Also, unlike single-type quadrupole mass spectrometers, which can confirm the ion intensity of all ions in a single analysis by scanning measurements that scan mass-to-charge ratios across the mass-to-charge ratio range of the measurement object, MS / MS analysis It is virtually impossible to confirm the ionic strength of all MRM transitions in one analysis with a possible mass spectrometer (eg triple quadrupole mass spectrometer). Therefore, it has been difficult conventionally to appropriately select quantitative ions and confirmation ions in a mass spectrometer capable of MS / MS analysis. However, according to the present invention, as described above, selection of appropriate quantification ions and confirmation ions based on the standard spectrum information stored in the MS / MS spectrum information storage unit 301 and the actual measurement data acquired in step S2 It becomes possible. That is, it can be said that GC-MS using a mass spectrometer capable of MS / MS analysis is more effective than GC-MS using a single type mass spectrometer.

  In addition, although the above embodiment is an example in which the present invention is applied to GC-MS, in LC-MS and GC-MS, a plurality of compounds in a sample are temporally separated, and detected by a mass spectrometer for each compound. It is also clear that the present invention can be applied to LC-MS since the point of doing so is exactly the same.

  Furthermore, it is obvious that appropriate modifications, alterations, and additions can be made within the scope of the present invention and still be covered by the appended claims.

DESCRIPTION OF SYMBOLS 1 ... Gas chromatograph (GC) part 10 ... Sample vaporization chamber 11 ... Micro syringe 12 ... Column oven 13 ... Column 2 ... Mass spectrometry (MS) part 20 ... Chamber 21 ... Ion source 22 ... Quadrupole mass filter 23 ... Ion detection Unit 24 ... Analog to Digital Converter (ADC)
Reference Signs List 25 front stage quadrupole mass filter 26 collision cell 27 multipole ion guide 28 rear stage quadrupole mass filter 3 300 data processing unit 31 mass spectrum information storage unit 301 MS / MS spectrum information storage unit 32 ... fixed amount / confirmed ion determination processing unit 321 ... signal intensity estimation unit 322 ... fixed amount / confirmed ion selection unit 33 ... calibration curve creation unit 34 ... calibration curve storage unit 35 ... fixed processing unit 4 400 ... control unit 41, 401 ... in advance Analysis execution control unit 42, 402 ... Standard sample analysis control unit 43, 403 ... Normal sample analysis control unit 5 ... Main control unit 6 ... Input unit 7 ... Display unit

Claims (5)

A target compound is quantified using a quantitative ion defined for each target compound, including a chromatographic part that separates compounds in a sample in the time direction, and a mass spectrometry part that detects each of the separated compounds. In the chromatograph mass spectrometer,
a) A spectral information storage unit in which standard spectral information, which is a standard mass spectrum or a standard signal intensity value at a plurality of mass-to-charge ratios or a ratio of the signal intensity values, is stored for each target compound;
b) Analysis that controls the operation of the chromatograph unit and mass analysis unit so that a sample containing a plurality of target compounds at known concentrations is analyzed as an ion of a specific mass-to-charge ratio determined for each compound as a mass analysis target A control unit,
c) measured signal strength values for specific mass-to-charge ratios obtained for each target compound under the control of the analysis control unit, and standard spectral information for each target compound stored in the spectral information storage unit A signal strength value estimating unit for estimating a signal strength value for the predetermined concentration at a mass-to-charge ratio other than the specific mass-to-charge ratio, for each target compound based on
d) As a quantitative ion based on signal strength values at a plurality of mass-to-charge ratios including the signal strength value of the actual measurement and the signal strength value estimated by the signal strength value estimation unit obtained for each target compound A quantitative ion selection unit for selecting a mass-to-charge ratio to be used for each target compound;
A chromatograph mass spectrometer comprising: The chromatograph mass spectrometer according to claim 1, wherein
The quantitative ion selection unit is configured such that the signal intensity of the first object compound that emphasizes the detection sensitivity most among the plurality of object compounds is relatively greater than the signal intensity of the other object compounds. The mass-to-charge ratio of the quantitative ion of the first target compound is selected as the quantitative ion of the target compound other than the first target compound after selecting the mass-to-charge ratio of the quantitative ion of the first target compound. A chromatograph mass spectrometer characterized in that. The chromatograph mass spectrometer according to claim 1, wherein
The quantitative ion selection unit selects, as the mass-to-charge ratio of quantitative ions of the first object compound, the mass-to-charge ratio at which the signal intensity in the first object compound is the largest among the plurality of object compounds. In addition, as a quantitative ion of the target compound other than the first target compound, selecting a mass-to-charge ratio that exhibits as low a signal strength as possible even when higher than the signal strength of the quantitative ion of the first target compound Chromatographic mass spectrometer characterized by The chromatograph mass spectrometer according to any one of claims 1 to 3, wherein
The mass analysis unit includes an ion detector whose gain changes in accordance with an applied voltage,
Among the quantitative ions selected respectively by the quantitative ion selection unit for a plurality of target compounds, the applied voltage to the detector is determined so that the one showing the largest signal intensity is not saturated at the output of the ion detector. A chromatograph mass spectrometer characterized by further having a control part. The chromatograph mass spectrometer according to any one of claims 1 to 4, wherein
The chromatograph mass spectrometer according to claim 1, wherein the quantitative ion selection unit selects the confirmation ion together with the quantitative ion for each target compound.

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