Method for controlling liquid chromatograph mass spectrometer

Abstract

The objective of the present disclosure is to provide a liquid chromatograph mass spectrometry device control method with which it is possible to detect contamination of a mobile phase solvent by foreign matter without employing an internal standard substance. In a liquid chromatograph mass spectrometry device control method according to the present disclosure: a first ratio of a signal strength at a first time point to a signal strength at a second time point during measurement employing a first mobile phase solvent is calculated, and a second ratio of the signal strength at the first time point to the signal strength at the second time point during measurement employing a second mobile phase solvent is calculated; and a determination of whether the second mobile phase solvent is contaminated is made in accordance with an absolute difference between the first ratio and the second ratio (see Fig. 2).

Description

[Technical field]

[0001] The present disclosure relates to a method for controlling a mass spectrometer. [Background technology]

[0002] The mobile phase solvent used in measurements using a liquid chromatograph mass spectrometer (LC / MS) comes into contact with the solvent bottle, synthetic resin tubes, filters, etc. The components of the solvent bottle, tubes, and filters, or substances adhering to their surfaces, gradually dissolve into the mobile phase solvent over time and can become impurities that contaminate the mobile phase solvent. When the mobile phase solvent is contaminated with impurities, a phenomenon occurs in which the ionization of the target substance that should be ionized is suppressed (ion suppression), and the measurement sensitivity of the target substance decreases.

[0003] In Patent Document 1 listed below, an internal standard substance is added to the mobile phase solvent and measurement is carried out, and if the intensity of this internal standard substance becomes smaller than a standard, it is determined that ion suppression is occurring (see abstract). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO09 / 123297 Summary of the Invention [Problem to be solved by the invention]

[0005] In the conventional technique of adding an internal standard substance as in Patent Document 1, the internal standard substance itself can become a contaminant that contaminates the mobile phase solvent. Therefore, there is a demand for a technique that can detect contamination of the mobile phase solvent without adding a substance that can become a contaminant.

[0006] The present disclosure has been made in consideration of the above-mentioned technical problems, and aims to provide a control method for a liquid chromatograph mass spectrometer that is capable of detecting contamination of a mobile phase solvent by impurities without using an internal standard substance. [Means for solving the problem]

[0007] A control method for a liquid chromatograph mass spectrometer according to the present disclosure calculates a first ratio of signal intensities at a first time and a second time during measurement using a first mobile phase solvent, and further calculates a second ratio of signal intensities at the first time and the second time during measurement using a second mobile phase solvent, and determines whether or not the second mobile phase solvent is contaminated based on the absolute difference between the first ratio and the second ratio. Effect of the Invention

[0008] According to the control method of the liquid chromatograph mass spectrometer of the present disclosure, it is possible to detect contamination of a mobile phase solvent by impurities without using an internal standard substance. Problems, configurations, and effects other than those described above will become apparent from the description of the following embodiments. [Brief description of the drawings]

[0009] [Figure 1] 1 shows the configuration of a mass spectrometer 5 according to a first embodiment. [Diagram 2] 1 is a graph illustrating measurement results of a chromatogram signal. [Figure 3A] 10 is a flowchart illustrating a procedure for determining whether or not the second mobile phase solvent is contaminated. [Figure 3B] 13 is a flowchart illustrating another procedure for determining whether the second mobile phase solvent is contaminated. [Figure 4A] 1 is an example of a total ion chromatogram obtained by operating the mass spectrometer 5 in a scan mode. [Figure 4B] An example of the measurement result of the ion signal intensity in FIG. 4A is shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <Embodiment 1> 1 shows the configuration of a mass spectrometer 5 according to a first embodiment of the present disclosure. A measurement sample delivered by a pump such as a liquid chromatograph is ionized by an ion source 500. Since the ion source 500 operates under atmospheric pressure and the mass spectrometer 5 operates in a vacuum, ions 510 are introduced into the mass spectrometer through an interface 520 between the atmosphere and the vacuum.

[0011] Ions generated from the ion source have various masses, but an AC voltage (high frequency voltage) and a DC voltage that allow the target ions to pass are applied from a quadrupole power supply 580 to a first quadrupole electrode section 540 (with a quadrupole electrode 530 inside), and only the target ions originating from the measurement sample are selectively passed through. A collision gas 570 (nitrogen gas, argon gas, etc.) for dissociating the target ions is introduced from a supply source through a gas line 571 to the second quadrupole electrode section 541.

[0012] The second quadrupole electrode 531 normally has only an AC voltage applied from the quadrupole power supply 580 to eliminate mass selectivity, and generates fragment ions by colliding the target ions that have passed through the first quadrupole electrode section 540 with gas. The generated fragment ions pass through the second quadrupole electrode section 541 and enter the third quadrupole electrode section 542.

[0013] When a radio frequency voltage and a DC voltage for passing the target fragment ions are applied from a quadrupole power supply 580 to the third quadrupole electrode 532, only the target fragment ions pass through the third quadrupole electrode section 542. The passed target fragment ions are detected by a detector 550. A detection signal is sent to a data processing section 560 (controller), which then performs mass analysis.

[0014] Here, a triple quadrupole mass spectrometer called TripleQMS is shown as an example of the device configuration, but the technology disclosed herein can also be applied to a quadrupole mass spectrometer, such as a SingleQMS with a single QMF installed inside. Also, in the embodiment, a quadrupole is used as an example of a mass filter, but the technology disclosed herein can be applied to multipole mass filters, not limited to quadrupoles.

[0015] FIG. 2 is a graph illustrating the measurement results of a chromatogram signal. Here, both the first mobile phase solvent and the second mobile phase solvent are mixtures of liquid A (pure water) and liquid B (methanol). When the ratio of liquid B in the mobile phase solvent changes over time as shown in the upper part of FIG. 2, a blank sample was measured by the gradient elution method using a mass spectrometer 5. The horizontal axis of FIG. 2 is the elapsed time from the start of elution. The vertical axis of the lower part of FIG. 2 is the ion signal intensity acquired by the mass spectrometer 5 by measuring the blank sample.

[0016] The mass spectrometer 5 first measures the ion signal intensity using the first mobile phase solvent. The first mobile phase solvent is an uncontaminated mobile phase solvent. For example, the following can be used as the first mobile phase solvent: (a) a mobile phase solvent that has just been prepared; (b) a mobile phase solvent that has been stored under temperature and humidity controlled conditions (such as in a refrigerator) from preparation until use. The mass spectrometer 5 measures the ion signal intensity I at time t1, with the time when elution using the first mobile phase solvent is started as time 0. 1,t1 and the ion signal intensity I at time t 1,t2 are measured. The time t1 and the time t2 are times when the composition ratio of the solvent (the ratio of solution B in FIG. 2) is different from each other. The mass spectrometer 5 calculates the ratio R1 of the signal intensities of each ion as follows: 1,t2 / I 1,t1 =R1.

[0017] Next, the mass spectrometer 5 measures the ion signal intensity using the second mobile phase solvent. The second mobile phase solvent is a determination target for determining whether it is contaminated. The second mobile phase solvent is at least a mobile phase solvent different from the first mobile phase solvent, and includes, for example, the one obtained by installing the first mobile phase solvent in the mass spectrometer 5 and allowing time to pass as it is. The mass spectrometer 5 sets the time when the elution using the second mobile phase solvent starts as time 0, and measures the ion signal intensities I 2,t1 , I 2,t2 at the same times t1 and t2 as those of the first mobile phase solvent, respectively. The mass spectrometer 5 calculates the ratio R2 of each ion signal intensity as follows: I 2,t2 / I 2,t1 = R2.

[0018] If the second mobile phase solvent is contaminated and contains a large amount of impurities, it is considered that due to the influence, as the ratio of the B solution increases, the ion signal intensity increases more than when not contaminated. By utilizing this, it is possible to determine whether the second mobile phase solvent is contaminated by comparing R1 and R2. Specifically, when R2 / R1 or R2 - R1 is equal to or greater than the threshold value (that is, when the two deviate greatly and the absolute difference between the two is equal to or greater than the threshold value), it is determined that the mobile phase solvent used for the measurement of R2 is contaminated.

[0019] Depending on the change over time of the ratio of the B solution (that is, the way of applying the gradient in the gradient method) and the properties of the mobile phase solvent, etc., it is also possible that when the second mobile phase solvent is contaminated, the rate of increase in the ion signal intensity is smaller (that is, R2 < R1). Even in this case, a similar determination can be carried out depending on whether R1 / R2 or R1 - R2 is equal to or greater than the threshold value.

[0020] Since it is possible to know in advance which of R1 and R2 is larger during contamination depending on the type of mobile phase solvent, etc., it is also possible to know in advance which of the calculation formulas should be used: (a) R2 / R1 or R2-R1, or (b) R1 / R2 or R1-R2. If it is unclear which is larger for some reason, a similar judgment may be made depending on whether the absolute difference |R2-R1| is equal to or greater than a threshold value.

[0021] It is desirable to set times t1 and t2 so as to avoid the time expected as the elution time of the target substance to be measured by the mass spectrometer 5. Although the measurement in FIG. 2 is performed using a blank sample, there is a possibility that the target substance from the previous measurement may be carried over, and the ion signal of the carried over target substance may be superimposed when the elution time of the target substance has passed. Note that the target substance here refers to the substance that is expected to be measured by the mass spectrometer 5 using the change over time in the ratio of solution B as shown in the upper part of FIG. 2.

[0022] The following is a supplementary explanation of the method for performing the measurement shown in Fig. 2. The mass spectrometer 5 is operated in, for example, selected ion monitoring (SIM) mode, multiple reaction monitoring (MRM) mode, or the like, and only ions with an arbitrary m / z value are measured. From the mass chromatogram signal value (ion signal) obtained by this measurement, the measurement result shown in Fig. 2 can be obtained.

[0023] 3A is a flow chart for explaining a procedure for determining whether the second mobile phase solvent is contaminated. In step S301, the mass spectrometer 5 calculates R1 using the first mobile phase solvent according to the procedure explained in FIG. 2, and stores the result in a storage device or the like. After S301, at the time of determining whether the second mobile phase solvent is contaminated, step S302 is started. In S302, the mass spectrometer 5 calculates R2 using the second mobile phase solvent according to the procedure explained in FIG. 2, and compares the result with R1.

[0024] S301 may be performed, for example, when a user operates a user interface (e.g., a button on the device, an operation part on a screen interface, etc.) provided in the mass spectrometer 5. S302 may be performed when the user wishes to determine contamination of the second mobile phase solvent. For example, S302 and subsequent steps may be performed while the target substance is being measured, or only S302 (and S303 and subsequent steps, as necessary) may be performed independently during a spare time when the target substance is not being measured.

[0025] In step S303, the mass spectrometer 5 determines whether the second mobile phase solvent is contaminated or not based on the result of comparing R1 and R2. If it is not contaminated, the sample to be analyzed is measured (S304). If it is contaminated, the user is notified and the measurement of the sample to be analyzed is canceled (S305).

[0026] Fig. 3B is a flow chart illustrating another procedure for determining whether the second mobile phase solvent is contaminated. S301 to S304 are the same as those in Fig. 3A. In Fig. 3B, S306 is performed instead of S305. In S306, the mass spectrometer 5 switches the solvent used from the second mobile phase solvent to another mobile phase solvent. The following example is one possible method for switching.

[0027] (FIG. 3B: Step S306: Example 1 of switching method) There are cases where a combination of a container containing liquid A and a container containing liquid B is connected to the mass spectrometer 5 via a valve in multiple sets. For example, as shown in Example 1 of FIG. 3B, there is a case where two sets of liquid A and liquid B are connected via a valve. In this case, the connection destination of the valve (i.e., the liquid path for obtaining the mobile phase solvent) can be switched from the set of A1 and B1 to the set of A2 and B2.

[0028] (FIG. 3B: Step S306: Example 2 of switching method) When the mass spectrometer 5 has a mechanism for replacing the mobile phase solvent in the container, the mechanism may be used to replace the second mobile phase solvent in the container with another mobile phase solvent. In the example shown in Fig. 3B, the A1 liquid of the second mobile phase solvent is replaced with the A1' liquid, and the B1 liquid of the second mobile phase solvent is replaced with the B1' liquid.

[0029] After switching the second mobile phase solvent to another mobile phase solvent, the ion signal intensity may be measured again at times t1 and t2 for the switched mobile phase solvent, R2 may be calculated, and contamination of the second mobile phase solvent may be determined again. Furthermore, if the switched mobile phase solvent is fresh and corresponds to the first mobile phase solvent, the first mobile phase solvent may be regarded as being reintroduced, and the ion signal intensity may be measured again at times t1 and t2, and R1 may be calculated again.

[0030] <First embodiment: Summary> The mass spectrometer 5 according to the first embodiment calculates the ratio R1 of the ion signal intensities at times t1 and t2 when a blank sample is measured using the first mobile phase solvent, and the ratio R2 of the ion signal intensities at times t1 and t2 when a blank sample is measured using the second mobile phase solvent, and compares the difference or ratio with a threshold value to determine whether the second mobile phase solvent is contaminated. This makes it possible to determine the presence or absence of contamination without adding an internal standard, thereby preventing the internal standard itself from acting as a contaminant.

[0031] The mass spectrometer 5 according to the first embodiment judges contamination of the second mobile phase solvent using the ratio of ion signal intensities (R1 and R2 are both calculated as the ratio of ion signal intensities at times t1 and t2, respectively). By using the ratio of ion signals at different times instead of the ion signal intensity values ​​themselves, contamination can be judged while suppressing the influence of the instrumental difference.

[0032] When the mass spectrometer 5 according to the first embodiment determines that the second mobile phase solvent is contaminated, it notifies the user of the fact and cancels the measurement, or replaces the second mobile phase solvent with another mobile phase solvent and then performs the measurement, thereby making it possible to avoid obtaining erroneous measurement results by using the contaminated second mobile phase solvent as is.

[0033] <Embodiment 2> In the first embodiment, an example is described in which ion signal intensity is measured only for a specific m / z. Alternatively, a certain range of m / z may be scanned, and ion signal values ​​obtained within the range may be used. In the second embodiment of the present disclosure, an example is described. The configuration of the mass spectrometer 5 is the same as that of the first embodiment.

[0034] 4A is an example of a total ion chromatogram obtained by operating the mass spectrometer 5 in scan mode. The scan mode is a measurement operation for acquiring ion detection signals in a certain range of m / z. The total ion chromatogram is obtained by adding up the ion detection signals of all m / z. In contrast, the SIM mode described in the first embodiment is different from the scan mode in that it is a measurement operation for acquiring ion detection signals only for a specific m / z.

[0035] The mass spectrometer 5 measures ion detection signals using a blank sample for each of the first mobile phase solvent (indicated as new in FIG. 4A) and the second mobile phase solvent (indicated as PP in FIG. 4A) in the same manner as in embodiment 1. The solvent ratio is assumed to change as shown in the lower part of FIG. 4A. The mass spectrometer 5 measures the ion signal intensities at times t1 and t2, respectively, and calculates their ratios R1 and R2, in the same manner as in embodiment 1.

[0036] FIG. 4B shows an example of the measurement result of the ion signal intensity in FIG. 4A. In this example, R1=6.37, R2=94.5. If R2 / R1 or R2-R1 is equal to or greater than the threshold, the second mobile phase solvent is determined to be contaminated. FIG. 4B shows a numerical example in the case of contamination.

[0037] <Embodiment 3> In the second embodiment, the mass spectrometer 5 performs the scan mode, thereby obtaining a total ion chromatogram for a certain range of m / z. A mass spectrum is obtained at the same time by setting the ion signal obtained at this time as the vertical axis and the m / z as the horizontal axis. Using this mass spectrum, the component composition and the amount of impurities contained in the second mobile phase solvent can be analyzed. The mass spectrometer 5 may present the analysis result together with the contamination determination result. However, since the measurement accuracy in the scan mode is lower than that in the SIM mode or the MRM mode, it is considered desirable to treat the composition and the amount of impurities analyzed by the scan mode as an estimated result.

[0038] <Fourth embodiment> The SIM mode or MRM mode of the mass spectrometer 5 has the advantage that the measurement time is short and many data points can be obtained (i.e., the resolution of the measurement results is high) because ion signals are acquired only for a single m / z. However, mass spectra cannot be obtained. On the other hand, the scan mode has the advantage that ion signals are acquired over a certain m / z range, so although the measurement time is long, a mass spectrum can be obtained. It is also possible to combine these modes to utilize the advantages of both.

[0039] For example, in order to determine whether the second mobile phase solvent is contaminated, first, the SIM mode or MRM mode is performed to obtain a chromatographic signal intensity, and the flow chart of FIG. 3A to FIG. 3B is performed using this. If it is determined that the second mobile phase solvent is contaminated, the mass spectrum is obtained by performing the scan mode, and the component composition and the amount of impurities contained in the second mobile phase solvent are analyzed using this. By combining such modes, the measurement is performed quickly under normal circumstances, and the impurities are analyzed by the scan mode only when the second mobile phase solvent is contaminated, so that both measurement efficiency and impurity analysis can be achieved.

[0040] <Modifications of the present disclosure> The present disclosure is not limited to the above-mentioned embodiment, and includes various modified examples. For example, the above-mentioned embodiment has been described in detail to clearly explain the present disclosure, and is not necessarily limited to those having all the configurations described. In addition, it is possible to replace a part of the configuration of a certain embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of a certain embodiment. In addition, it is possible to add, delete, or replace other configurations with respect to a part of the configuration of each embodiment. In addition, the control lines and information lines are shown as those considered necessary for explanation, and not necessarily all control lines and information lines are shown in the product. In reality, it may be considered that almost all configurations are connected to each other.

[0041] In the above embodiment, the first mobile phase solvent (or another fresh mobile phase solvent when replacing the second mobile phase solvent) is described on the premise that it is not contaminated. Since the first mobile phase solvent is a standard for the presence or absence of contamination, it is desirable that the first mobile phase solvent is not contaminated. However, depending on, for example, the required determination accuracy, if it is possible to ensure that the degree of contamination is less than a predetermined standard value, the mobile phase solvent may be used as the first mobile phase solvent.

[0042] In the above embodiment, each flow chart may be performed by a calculation device such as data processing unit 560, or may be performed by an operator manually operating mass spectrometer 5. [Explanation of symbols]

[0043] 5: Mass spectrometer 500: Ion source 510: Ion 520: Interface 530: Quadrupole electrode 531: Second quadrupole electrode 532: Third quadrupole electrode 540: First quadrupole electrode part 541: Second quadrupole electrode part 542: Third quadrupole electrode section 550: Detector 560: Data processing unit 580: Quadrupole power supply 570: Collision Gas 571: Gas line

Claims

1. A method for controlling a liquid chromatograph mass spectrometer, comprising: Calculating a first ratio of chromatographic signal intensities at two different times obtained by measuring a blank sample by a gradient elution method using a first mobile phase solvent having a contamination level less than the reference value; Calculating a second ratio of chromatographic signal intensities at two different times obtained by measuring a blank sample by gradient elution using a second mobile phase solvent having the same composition as the first mobile phase solvent; determining whether the second mobile phase solvent is contaminated using the first ratio and the second ratio; having In the step of calculating the first ratio, a ratio between a chromatogram signal intensity at a first time when a first hour has elapsed since the start of elution using the first mobile phase solvent and a chromatogram signal intensity at a second time when a second hour has elapsed and the solvent ratio is different from that at the first time is calculated as the first ratio; In the step of calculating the second ratio, a ratio between a chromatogram signal intensity at a time when the first time has elapsed since the start of elution using the second mobile phase solvent and a chromatogram signal intensity at a time when the second time has elapsed is calculated as the second ratio; In the determining step, when an absolute difference between the first ratio and the second ratio is equal to or greater than a threshold value, it is determined that the second mobile phase solvent is contaminated. Control methods.

2. The first time and the second time are both set to be different from a time point at which the elution time of the target substance measured by the liquid chromatograph mass spectrometer using the solvent ratio at each of the first time and the second time is expected to elapse.

2. The control method according to claim 1.

3. The control method further comprises: a step of notifying a user of the fact that the second mobile phase solvent is contaminated in the step of determining; a step of starting measurement of a target substance to be measured by the liquid chromatograph mass spectrometer when it is determined in the step of determining that the second mobile phase solvent is not contaminated; have 2. The control method according to claim 1.

4. The control method further comprises: If it is determined in the determining step that the second mobile phase solvent is contaminated, switching the second mobile phase solvent to another mobile phase solvent; a step of starting measurement of a target substance to be measured by the liquid chromatograph mass spectrometer when it is determined in the step of determining that the second mobile phase solvent is not contaminated; have 2. The control method according to claim 1.

5. the liquid chromatograph mass spectrometer includes a container containing a third mobile phase solvent having the same composition as the second mobile phase solvent; In the step of switching to another mobile phase solvent, a route for obtaining a mobile phase solvent is switched from a container containing the second mobile phase solvent to a container containing the third mobile phase solvent, thereby switching the second mobile phase solvent to the other mobile phase solvent.

5. The control method according to claim 4.

6. the liquid chromatograph mass spectrometer includes a mechanism for replacing the second mobile phase solvent in a container for storing the second mobile phase solvent with the second mobile phase solvent that is not contaminated; In the step of switching to another mobile phase solvent, the mechanism replaces the second mobile phase solvent in a container containing the second mobile phase solvent with the uncontaminated second mobile phase solvent, thereby switching the second mobile phase solvent to the other mobile phase solvent.

5. The control method according to claim 4.

7. The control method further comprises: re-performing the steps of calculating the second ratio and determining after the step of switching to another mobile phase solvent.

5. The control method according to claim 4.

8. The control method includes, after the step of switching to the different mobile phase solvent, recalculating the first ratio using the different mobile phase solvent.

5. The control method according to claim 4.

9. The method further comprises the step of measuring only ion signals of a particular m / z; In the step of calculating the first ratio and the step of calculating the second ratio, the first ratio and the second ratio are calculated using a chromatogram signal obtained in the step of measuring only the ion signal of the specific m / z.

2. The control method according to claim 1.

10. The method further comprises the step of measuring ion signals having m / z within a particular range by scanning within the range; In the step of calculating the first ratio and the step of calculating the second ratio, the first ratio and the second ratio are calculated using a total ion chromatogram signal obtained in the step of measuring by scanning.

2. The control method according to claim 1.

11. The control method according to claim 10, further comprising a step of estimating impurities and their amounts in the second mobile phase solvent using the mass spectrum obtained in the step of measuring by scanning.

12. The method further comprises the step of measuring only ion signals of a particular m / z; In the step of calculating the first ratio and the step of calculating the second ratio, the first ratio and the second ratio are calculated using a chromatogram signal obtained in the step of measuring only the ion signal of the specific m / z, The control method further includes a step of measuring ion signals of m / z included in a specific range by scanning within the range when it is determined in the determining step that the second mobile phase solvent is contaminated, The control method according to claim 1 , further comprising a step of estimating impurities and their amounts in the second mobile phase solvent using the mass spectrum obtained in the step of measuring by scanning.

13. The control method includes carrying out a step of calculating the second ratio and a step of determining during a spare time during which the liquid chromatograph mass spectrometer is not measuring a target substance to be measured using the solvent ratios at the first time and the second time.

2. The control method according to claim 1.

14. A liquid chromatograph apparatus comprising a controller which implements the control method according to claim 1.

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