JP4823794B2 - Mass spectrometer and detection method - Google Patents

Description

  The present invention relates to environmental substance detection, harmful chemical substance detection, narcotics and explosive detection techniques, and more particularly to a detection apparatus using a mass spectrometer.

  As a conventional detection technique, Japanese Patent Laid-Open No. 7-134970 (Prior Art 1) determines a plurality of m / z values (mass number of ions / valence of ions) indicating a specific drug from a measured mass spectrum. A method for determining whether or not a specific drug is contained in the test gas is described. In WO2002-025265 (prior art 2), when the detection target substance and the contaminant substance have the same m / z using tandem mass spectrometry, the precursor ion of the m / z is dissociated and the fragment ion m A method for determining the presence / absence of a substance to be detected based on the / z value is described.

  Japanese Patent Laid-Open No. 2004-361297 (Prior Art 3) discloses that when a plurality of ion components of a first ion component and a second ion component are detected in a detection target substance, only the first ion component is repeatedly measured. When the first ion component is detected, the second ion component corresponding to the first ion component is detected, and when the second ion component exceeds the threshold, the detection target substance It is described that an alarm is sounded when it is judged that exists. Furthermore, the first ion component or the second ion component is divided into a high volatile component measured at the beginning of detection and a low volatile component measured at the latter half of the detection, and the detection target component to be measured is prioritized to be efficient. In particular, a method for enabling detection in a short time is described.

  In Japanese Patent No. 2545528 (prior art 4), Japanese Patent No. 3345695 (prior art 5), and Japanese Patent Laid-Open No. 5-256838 (prior art 6), an application is applied to an intermediate pressure part in an atmospheric pressure ionization mass spectrometer. A method for collisional dissociation of sample molecules with a drift voltage is described. Japanese Laid-Open Patent Publication No. 4-342946 (Prior Art 7) describes a method of acquiring a highly sensitive spectrum at all mass numbers by continuously changing the drift voltage according to a high mass number from a low mass number. . Japanese Patent Application Laid-Open No. 2006-86002 (Prior Art 8) describes a method in which a gas chromatograph column is introduced into an ion source and ionized.

JP-A-7-134970 WO2002-025265 JP 2004-361297 A Japanese Patent No. 2545528 Japanese Patent No. 3345695 JP-A-5-256838 JP-A-4-342946 JP 2006-86002 A

  In the method of Prior Art 1, there is a possibility that the substance to be detected and the contaminants have the same m / z ion peak, and the ability to distinguish the substance (hereinafter referred to as selectivity) is lowered, which may result in a false alarm. It was. The method of the prior art 2 performs tandem mass spectrometry in order to solve the problem of the prior art 1. Even if the detection target substance and the contaminants have the same m / z ion peak, the presence of the detection target substance is judged by the fragment peak obtained by dissociating the ion peak, so that the selectivity is extremely high. However, in this method, since ions are once trapped and only ions of the detection target substance are selected and dissociated, the measurement requires about 0.1 seconds and takes time. In particular, in explosive detection, it is necessary to specify a substance to be detected in a short time. Moreover, since collision gas is required for dissociation, there is a problem that the apparatus becomes large.

  In the method of the prior art 3, a measure has been devised to shorten the detection time by repeatedly measuring only the first ion component. FIG. 2 is a diagram for explaining an example of an operation sequence of the prior art 3. The horizontal axis is time, and the vertical axis is drift voltage. In the prior art 3, the drift voltage is not controlled. The figure shows an example in which four types of detection target substances A, B, C, and D are detected. Since the detection target substance A is a highly volatile substance, it always starts first. Furthermore, it becomes a low-volatile substance according to the detection target substances B, C, and D. In one cycle of measurement, the m / z ion peak of the first ion component of the detection target substances A, B, C, and D is monitored. When this one cycle is repeated and the m / z ion peak of the first ion component corresponding to the detection target substance B exceeds the threshold set in the ion intensity of the database, the second ion of the detection target substance B The m / z ion peak of the component is detected. When the ion intensity of the ion peak exceeds a preset threshold value, it is determined that the detection target substance B has been detected, and an alarm is sounded.

  In the prior art 3, the first ionic component can be efficiently detected in a short time by assigning a priority between the high volatile component and the low volatile component. Further, even if the first ion component and the impurity component have the same m / z ion peak, detection is performed by comprehensive judgment of the priority order and the second ion component. However, in many cases, the peak intensity of the second ion component is smaller than the peak intensity of the first ion component. Therefore, there is a possibility of being buried in the peak of the contaminated component, which may cause a false alarm.

  In the prior arts 4, 5, and 6, molecular structures are identified by acquiring and comparing two points of mass spectra with varying drift voltages. However, this method has a problem that it is not efficient and takes time to identify and detect substances. Prior art 7 attempts to increase the sensitivity in the entire range of low and high mass numbers by lowering the drift voltage as the mass number increases, but changes the drift voltage in the entire mass number range. Therefore, it is not efficient and takes time. The prior art 8 has a problem that it takes time to identify the sample gas component separated by the gas chromatograph.

  In the present invention, the m / z ion peak specific to the detection target material is monitored by controlling the drift voltage to be optimum for the m / z ion peak of the detection target material based on the information registered in the database. When an m / z ion peak specific to the detection target substance is detected, the fragment peak is monitored by changing the drift voltage to a voltage at which the m / z ion peak of the detection target substance dissociates. The drift voltage for dissociating the detection target substance detected at this time is registered in the database in advance. Further, when a fragment peak specific to the detection target substance registered in the database is detected, it is determined that the detection target substance exists and an alarm is sounded.

  According to the present invention, it is possible to identify a sample gas with high speed and high sensitivity. In particular, it is effective for an apparatus that must detect in a short time such as explosives detection.

Embodiments of the present invention will be described below with reference to the drawings.
[Example 1]
FIG. 1 is a schematic diagram showing an example of a mass spectrometer according to the present invention. The apparatus of the present embodiment is configured by an ion source unit in the atmosphere, a differential exhaust unit having an intermediate pressure, and a mass analyzing unit in a vacuum. In the case of explosive detection, the detection target substance existing on the surface of the subject is collected by wiping the subject with a collection sheet. Sampling paper is put into the sample introduction device 1 and the sample collected is vaporized by lamp heating or heater heating. The vaporized sample vapor (or sample fine particles) containing the substance to be detected is introduced into the ion source 3 by being sucked by the suction pump 2. The suction pump 2 sucks at a flow rate of 0.5 liters per minute. The ion source 3 is heated to 150 ° C. with a heater so that sample vapor does not adhere inside. A needle-like electrode 4 is disposed in the ion source 3, a high voltage is applied between the ion source 3 and the counter electrode 5, and a corona discharge is generated near the tip of the needle-like electrode 4. By this corona discharge, nitrogen, oxygen, water vapor, etc. in the air are ionized to become primary ions. The generated primary ions move to the first pore 6 side by an electric field. The inner diameter of the first pore 6 of the device of this embodiment is about 0.1 mm. At this time, the sample vapor sucked from the sample introducer 1 reacts with the primary ions, so that the sample vapor is ionized to become sample molecular ions. In the negative ionization mode in which a negative high voltage is applied to the needle electrode 4 to generate negative ions, the primary ions are often oxygen molecular ions. A typical negative ionization reaction in the sample molecule (M) is shown below.
M + (O ₂ ) ⁻ → (M) ⁻ + O ₂

  Since the generated sample molecular ions have a potential difference of about 1 kV between the counter electrode 5 and the first pore 6, the sample molecular ions enter the differential exhaust section through the first pore 6. In the differential exhaust section, adiabatic expansion occurs, and clustering in which solvent molecules adhere to ions occurs. In order to reduce this clustering, it is desirable to heat the first pores 6 with a heater or the like. In the present embodiment, the first pore 6 is heated to 180 ° C. with a heater. The differential exhaust unit is exhausted by a differential exhaust pump 7.

  The generated sample molecular ions are introduced into the mass spectrometer through the first pore 6, the differential exhaust portion, and the second pore 8. A drift voltage is applied between the first pore 6 and the second pore 8 by a drift voltage power source 9. This drift voltage drifts in the direction of the 2nd pore 8 by the ion taken in by the differential exhaust part, and the effect which improves the ion transmittance of the 2nd pore 8 remains in a differential exhaust part. It has the effect of desorbing solvent molecules such as water adhering to ions by collision with gas molecules. Further, when this drift voltage is further increased, the collision energy with the residual gas molecules is further increased, and a phenomenon occurs in which the sample molecule ions are dissociated.

  The sample molecular ions passing through the second pore 8 are efficiently converged on the quadrupole analysis tube 11 by applying a voltage to the electrostatic lens 10. The mass analyzer is evacuated by a vacuum pump 17. By controlling the frequency component and voltage applied to the quadrupole analysis tube 11 by the mass spectrometry control device 12, only ions having a target mass number are selected, passed, and detected by the detector 13. The arithmetic processing unit 14 changes the drift voltage with the drift power supply voltage 9 based on the information in the database 16 recorded in the storage device 15, and selects only ions having the target mass number with the mass spectrometry control unit 12. It passes through and is detected by the detector 13.

  FIG. 3 is a diagram illustrating an example of the database 16 that stores information on the detection target substance. The database 16 stores the mass number and threshold value of a signal to be detected based on the reference mass spectrum data regarding the substance to be detected. The substance name 100 to be detected stores a plurality of substances to be detected in the present invention. For each substance, a drift voltage A101, an ion mass number 102 at that time, and a threshold value C103 are stored. Further, a drift voltage B104, a fragment ion mass number 105, and a threshold value D106 necessary for dissociating the detection target substance are stored. The threshold value C103 and the threshold value D106 are numerical values for determining the presence or absence of detection, and it is sufficient that the amount of ions such as the number of ions (count number) and ion current can be determined.

  In this example, a quadrupole mass spectrometer is used for mass spectrometry. However, any ion trap mass spectrometer, ion mobility spectrometer, time-of-flight mass spectrometer, or magnetic field mass can be used as long as it can identify ions. Other methods such as analyzers can also be applied. Further, other methods such as a radiation source, electrons, light, laser, corona discharge, and Penning discharge can be applied as long as the ion source can generate sample ions.

The example which investigated the characteristic of the various explosives with respect to drift voltage with the apparatus of a present Example is demonstrated. The normal drift voltage of the apparatus of the present embodiment is 60 V at which the ion transmittance is the highest. A typical explosive component is TNT. When TNT was subjected to mass spectrometry, a TNT molecular ion (M) ⁻ was obtained at m / z = 227, and a molecular ion (M—OH) ⁻ from which an OH group was eliminated from the TNT molecular ion at m / z = 210 was m / z = 210. At z = 197, a molecular ion (M-ON) ^{− in} which the NO group is eliminated from the TNT molecular ion is detected. (M-OH) ^- and (M-ON) ^- is a fragment ion.

FIG. 4 shows an example of S / N (signal / background noise) change due to the drift voltage of TNT. The concentration of TNT is 10 ng (nanogram). From this graph, the T / N molecular ion (M) ^{− with} m / z = 227 has a maximum S / N at a drift voltage of 60V. On the other hand, when the drift voltage is increased to 60 V or more, the S / N of fragment ions m / z = 210 and m / z = 197 increases. This is a dissociation of TNT molecular ion (M) ^{− of} m / z = 227 by the drift voltage.

  FIG. 5 shows an example of the drift voltage dependence of the background peak at m / z = 210. A black circle in the figure is a background peak at m / z = 210 without a sample. This background peak decreases at a drift voltage of 60 V or higher. This is because a background component in the atmosphere, which is a noise component, is dissociated by increasing the drift voltage.

Dissociation by drift voltage is effective for substances that make NO _X adducts such as PETN, RDX, and NG in the explosive component. FIG. 6 shows an example of the S / N change due to the NG drift voltage. The concentration of NG is 20 ng (nanogram). When mass spectrometry of NG is performed, NG molecular ion (M) ⁻ is obtained at m / z = 228, and molecular ion (M + NO ₂ ) ^{− in} which NO ₂ group is added to NG molecular ion at m / z = 289 is m / z. Fragment molecular ion (NO ₃ ) ^{− in} which NG molecular ion is decomposed at = 62 is detected. The NO ₂ addition molecular ion (M + NO ₂ ) ^{− with} m / z = 289 has a high ionic strength at 40 V, which is lower than the normally used drift voltage 60 V. This is because the NO ₂ adduct is added to the NG molecular ion with a very weak binding energy, so that the bond is broken by increasing the drift voltage. Therefore, when detecting NG, the detection sensitivity is further improved by detecting the drift lower than 60V.

On the other hand, when the drift voltage is increased, the ionic strength of (NO ₃ ) ⁻ which is a fragment molecular ion increases. FIG. 7 shows an example of the drift voltage dependence of the m / z = 62 background peak. A black circle in the figure is a background peak of m / z = 62 without a sample. This background peak decreases at a drift voltage of 60 V or higher. Normally, many impurity ions exist at m / z = 62, but the impurity ions are dissociated and the NG molecular ions are also dissociated by increasing the drift voltage, and therefore, fragment molecular ions (NO ₃ ). ^- the detection becomes easy as.

  As an embodiment of the present invention, a method for detecting a fragment peak by changing a drift voltage will be described. FIG. 8 is a flowchart of an operation for detecting a fragment peak by changing the drift voltage. When the detection is started, the drift voltage suitable for the ion component of the detection target substance is changed based on the information stored in the database 16 (S11), and mass spectrometry is performed (S12). From this mass analysis result, the presence / absence of an intrinsic m / z ion peak generated from the detection target substance is determined (S13). If the m / z ion peak specific to the detection target substance is not detected, the process returns to step 11 to change to a drift voltage suitable for the ion component of the next detection target substance and repeat the measurement. When the ion peak of m / z specific to the detection target substance is detected in the determination of step 13, the drift voltage is changed to a fragment ion component generated in the detection target substance (S14), and mass analysis is performed (S15). From this mass analysis result, the presence / absence of a unique m / z fragment ion peak generated from the detection target substance is determined (S16), and an alarm is sounded if detected (S17). If a unique m / z fragment ion peak generated from the detection target substance is not detected, the process returns to the beginning, and the measurement is repeated while changing to a drift voltage suitable for the ion component of the next detection target substance.

More specifically, an operation sequence in which a change in drift voltage is known will be described. FIG. 9 is a diagram illustrating an example of an operation sequence of the drift voltage. The horizontal axis is time, and the vertical axis is drift voltage. The figure shows an example in which four types of detection target substances A, B, C, and D are detected. When the detection is started, the drift voltage (for example, 40V in the case of NG) suitable for the detection target substance A (for example, NG) is changed based on the information read from the database 16, and mass spectrometry is performed. The detection target substance A is a highly volatile substance and is preferably measured first. It is determined whether or not an intrinsic m / z ion peak (for example, (M + NO ₂ ) ⁻ ion of m / z = 289 in the case of NG) generated from the detection target substance A is detected from the mass analysis result. Next, based on the information read from the database 16, the drift voltage (for example, 60 V in the case of TNT) is changed to a drift voltage suitable for the detection target substance B (for example, TNT), and mass spectrometry is performed. Then (in the case of TNT, for example, the m / z = 227 (M) ^- ion) ion peaks unique m / z generated from detection target substance B determines whether the detected. Furthermore, based on the information read from the database 16, the drift voltage suitable for the detection target substances C and D is changed in order, and mass spectrometry is performed. Then, it is determined whether or not an inherent m / z ion peak generated from the detection target substances C and D is detected. In this manner, the detection target substances A, B, C, and D are repeatedly measured while changing the drift voltage based on the information stored in the database 16 recorded in the storage device 15.

At this time, for example, when mass analysis is performed by setting a drift voltage suitable for the detection target substance B, an intrinsic m / z ion peak generated from the detection target substance B (in the case of TNT, for example, m / z = 227). (M) ^- ions) is assumed to be detected. Then, based on the information in the database 16, a drift voltage (TNT) suitable for generating fragment ions of the detection target substance B (in the case of TNT, for example, (M−OH) ⁻ of m / z = 210). In the case of (1), for example, it is changed to 100 V) and mass spectrometry is performed. When a specific m / z fragment ion peak generated from the detection target substance B is detected from the mass analysis result, it is determined that the detection target substance B exists, and an alarm is sounded. Furthermore, the measurement is continued to check whether other substances to be detected exist. When an ion peak of m / z unique to the detection target substance A (in the case of NG, for example, (M + NO ₂ ) ⁻ ion of m / z = 289) is detected, the drift voltage is determined by the fragment ion of the detection target substance A. The voltage is changed to a voltage suitable for generation (in the case of NG, for example, 80 V), and mass spectrometry is performed. When a specific m / z fragment ion peak (in the case of NG, for example, (NO ₃ ) ^{− with} m / z = 62) generated from the detection target substance A is detected from the mass analysis result, the detection target substance A Sounds an alarm.

  In this embodiment, the subject is wiped with a collection sheet, and is heated and evaporated by the sample introduction device 1 to vaporize the detection target substance. As another method of the present embodiment, the vapor or fine particles of the detection target material may be collected by gas suction without using the sample introducing device 1. In this case, since it is not known when the detection target substance is aspirated, it is effective to constantly measure the detection target substances A, B, C, and D.

[Example 2]
FIG. 10 is a diagram showing an example of an operation sequence in consideration of the volatility of the detection target substance as one embodiment of the present invention. When the sample collected in the sample introducer 1 is heated and evaporated, the time to reach the ion source 3 varies depending on the volatility of the detection target substance. For example, a highly volatile detection target substance typified by NG quickly reaches the ion source, and then a medium volatile detection target substance TNT or the like arrives. Finally, a low-volatile detection target substance typified by PETN, RDX, or HMX reaches the ion source 3.

At the start of detection, based on the database 16 recorded in the storage device 15, the drift voltage is changed to a voltage (for example, 40V in the case of NG) optimum for the highly volatile detection target substance A (for example, NG), The presence / absence of detection of an intrinsic m / z ion peak (for example, (M + NO ₂ ) ⁻ ion with m / z = 289 in the case of NG) generated from the detection target substance A is determined. In the first half of the detection, only the highly volatile detection target substance reaches the ion source, so only the detection target substance A is measured several times. In the embodiment shown in FIG. 10, only one type of highly volatile detection target substance is detected. If there are a plurality of highly volatile detection target substances, the measurement is repeated with the plurality of highly volatile detection target substances. If a unique m / z ion peak is detected in the detection target substance A, the drift voltage is changed to an optimum drift voltage (for example, 80 V in the case of NG) based on the information in the database 16 to detect the ion peak. It is determined whether a unique m / z fragment ion peak generated from the target substance A (in the case of NG, for example, (NO ₃ ) ^{− with} m / z = 62) is detected.

Next to the detection target substance A, the drift voltage (for example, 60 V in the case of TNT) is changed to the optimum drift voltage for the detection target substances B (for example, TNT) and C, which are medium volatile substances, in order. It is determined whether a unique ion peak of m / z to be generated (in the case of TNT, for example, (M) ⁻ ion of m / z = 227) is detected. For example, (in the case of TNT, for example, the m / z = 227 (M) ^- ion) ion peaks unique m / z generated from detection target substance B when is detected, based on the information in the database 16 By changing the drift voltage (for example, 100 V in the case of TNT) suitable for generating fragment ions of the detection target substance B (in the case of TNT, for example, (M-OH) ⁻ of m / z = 210), Perform mass analysis. When a specific m / z fragment ion peak generated from the detection target substance B is detected from the mass analysis result, it is determined that the detection target substance B exists, and an alarm is sounded.

  The detection is further continued, and then the drift voltage optimum for the low-volatile detection target substance D is changed to determine whether an m / z ion peak specific to the detection target substance D is detected. In the present embodiment, the detection target substance C is less volatile than the detection target substance B. Therefore, the drift voltage is changed to the optimum drift voltage for the detection target substance C, and the intrinsic m / z ion peak generated from the detection target substance C is measured. In the second half, only the low-volatile detection target substance D is detected.

[Example 3]
FIG. 11 is a diagram showing an apparatus configuration example of another embodiment of the present invention in which an ion trap mass spectrometer is mounted in the mass spectrometer. In the case of an apparatus equipped with an ion trap mass spectrometer, if dissociation analysis is not performed, a mass spectrum can be acquired at a higher speed than a quadrupole mass spectrometer, and there is an advantage that the detection speed is high.

  Sampling paper is put into the sample introduction device 1 and the sample collected is vaporized by lamp heating or heater heating. The vaporized sample vapor (or sample fine particles) containing the substance to be detected is sucked by the suction pump 2 and introduced into the ion source 3. The suction pump 2 sucks at a flow rate of 0.5 liters per minute. The ion source 3 is heated to 150 ° C. with a heater so that sample vapor does not adhere inside. A needle electrode 4 is disposed in the ion source 3, and a high voltage is applied between the ion source 3 and the counter electrode 5, and a corona discharge is generated near the tip of the needle electrode 4. By this corona discharge, nitrogen, oxygen, water vapor, etc. in the air are ionized to become primary ions. The generated primary ions move to the first pore 6 side by an electric field. In this embodiment, the inner diameter of the first pore 6 is about 0.1 mm. At this time, the sample vapor sucked from the sample introducer 1 reacts with the primary ions, whereby the sample vapor is ionized to become sample molecular ions. Since the generated sample molecular ions have a potential difference of about 1 kV between the counter electrode 5 and the first pore 6, they enter the differential exhaust section via the first pore 6. In the differential exhaust section, adiabatic expansion occurs, and clustering in which solvent molecules adhere to ions occurs. In order to reduce this clustering, it is desirable to heat the first pores 6 with a heater or the like. In the present embodiment, the first pore 6 is heated to 180 ° C. with a heater. The differential exhaust unit is exhausted by a differential exhaust pump 7.

  The generated sample molecular ions are introduced into the mass spectrometer through the first pore 6, the differential exhaust portion, and the second pore 8. A drift voltage is applied between the first pore 6 and the second pore 8 by a drift voltage power source 9. This drift voltage drifts in the direction of the 2nd pore 8 by the ion taken in by the differential exhaust part, and the effect which improves the ion transmittance of the 2nd pore 8 remains in a differential exhaust part. There is an effect of desorbing solvent molecules such as water adhering to ions by collision with gas molecules. Further, when this drift voltage is further increased, the collision energy with the residual gas molecules is further increased, and a phenomenon occurs in which the sample molecule ions are dissociated.

  The sample molecular ions that have passed through the second pore 8 are efficiently converged on the ion trap mass spectrometer by applying a voltage to the electrostatic lens 10. The mass analyzer is evacuated by a vacuum pump 17. The ion trap analyzer is composed of end cap electrodes 18 and 19, a ring electrode 20, a gate electrode 21, a quartz ring 22, and the like, and a collision gas such as helium is introduced from a gas supply device 24 through a gas introduction pipe 23. Is done. The gate electrode 21 serves to prevent ions from being introduced into the ion trap from the outside when the ions trapped in the ion trap portion are taken out of the ion trap. The ions introduced into the ion trap have a smaller orbit due to collision with a collision gas such as helium, and then the high frequency voltage applied between the end cap electrodes 18 and 19 and the ring electrode 20 is scanned to scan the mass number. Every time, ions are discharged out of the ion trap. The discharged ions are detected by the detector 13. The arithmetic processing unit 14 changes the drift voltage with the drift power supply voltage 9 based on the information in the database 16 recorded in the storage unit 15, selects only ions having the target mass number with the mass analysis control unit 12, and passes And detected by the detector 13.

An example of detection using the apparatus shown in FIG. 11 will be described. When the detection is started, a drift voltage (for example, 40 V in the case of NG) suitable for the detection target substance A (for example, NG) is set based on the information stored in the database 16 recorded in the storage device 15, and mass spectrometry is performed. do. It is determined whether or not an intrinsic m / z ion peak (for example, (M + NO ₂ ) ⁻ ion of m / z = 289 in the case of NG) generated from the detection target substance A is detected from the mass analysis result. Next, based on the information in the database 16, the drift voltage (for example, 60 V in the case of TNT) is changed to a drift voltage suitable for the detection target substance B (for example, TNT), and mass spectrometry is performed. Then (in the case of TNT, for example, the m / z = 227 (M) ^- ion) ion peaks unique m / z generated from detection target substance B determines whether the detected. Furthermore, based on the information in the database 16, the drift voltage suitable for the detection target substances C and D is changed in order, and mass spectrometry is performed. Then, it is determined whether or not an inherent m / z ion peak generated from the detection target substances C and D is detected. Thus, the detection target substances A, B, C, and D are repeatedly measured while changing the drift voltage based on the information read from the database 16.

Now, when mass analysis is performed by setting a drift voltage suitable for the detection target substance B, a specific m / z ion peak generated from the detection target substance B (in the case of TNT, for example, (M / z = 227 (M ) ^- ions) is assumed to be detected. At this time, based on the information in the database 16, the drift voltage is a voltage suitable for generating fragment ions of the detection target substance B (in the case of TNT, for example, (M-OH) ⁻ of m / z = 210) ( In the case of TNT, it is changed to, for example, 100 V) and mass spectrometry is performed. When a specific m / z fragment ion peak generated from the detection target substance B is detected from the mass analysis result, it is determined that the detection target substance B exists, and an alarm is sounded. Furthermore, the measurement is continued to check whether other substances to be detected exist. For example, if a unique ion peak of m / z is detected also in the detection target substance A (in the case of NG, for example, (M + NO ₂ ) ⁻ ion of m / z = 289), drift is made based on information in the database 16. Mass spectrometry is performed by changing the voltage (for example, 80 V in the case of NG). When a specific m / z fragment ion peak (in the case of NG, for example, (NO ₃ ) ^{− with} m / z = 62) generated from the detection target substance A is detected from the mass analysis result, the detection target substance A Sounds an alarm.

  In this embodiment, the subject is wiped with a collection sheet, and is heated and evaporated by the sample introduction device 1 to vaporize the detection target substance. As another method of the present embodiment, the vapor or fine particles of the detection target material may be collected by gas suction without using the sample introducing device 1. In this case, since it is not known when the detection target substance is aspirated, it is effective to constantly measure the detection target substances A, B, C, and D.

[Example 4]
As an embodiment of the detection method according to the present invention, the presence or absence of a substance to be detected is detected by detecting both the intrinsic m / z ion peak and fragment ion peak generated from the substance to be detected by changing the drift voltage. An example of a method for determining the above will be described. In the present embodiment, detection accuracy can be improved by detecting both an intrinsic m / z ion peak and a fragment ion peak generated from the detection target substance.

FIG. 12 is a diagram illustrating an example of a mass spectrum when no detection target substance exists. The horizontal axis is m / z, and the vertical axis is ionic strength. (A) ion peak of specific m / z generated from detection target substance is detected (in the case of NG, for example, the m / z = 289 (M + NO 2) - ions), the (B) is detection target substance It is the unique m / z fragment ion peak produced (in the case of NG, for example, (NO ₃ ) ^{− with} m / z = 62). Based on the information stored in the database 16, the optimum drift voltage A for (A) (for example, 40V in the case of NG) is applied by a drift voltage power source. Whether or not an ion peak is detected in (A) is determined based on threshold information stored in the database 16 based on whether or not the ion intensity exceeds the threshold. In the case of the example of FIG. 12, since the ion intensity of (A) does not exceed the threshold value, it is determined that there is no substance to be detected and no alarm is sounded.

FIG. 13 is a diagram illustrating an example of a mass spectrum in the case where the contaminant substance and the detection target substance have the same ion peak of m / z. When a mass spectrum is acquired at a drift voltage A (40 V in the case of NG, for example) based on the information in the database 16, the intrinsic m / z ion intensity generated from the detection target substance in (A) (in the case of NG, For example, it is assumed that (M + NO ₂ ) ⁻ ion (m / z = 289) exceeds the threshold value. However, there is a possibility that the ion peak of the contaminant exists at the same m / z, and the threshold value is exceeded as a result of addition.

Therefore, in order to separate the contamination component and the detection target component, based on the information read from the database 16, the drift voltage is changed to the voltage B (for example, 80V in the case of NG), and a mass spectrum is acquired. As a result, as shown in the upper part of FIG. 13, the fragment ion intensity of the specific m / z generated from the substance to be detected in (B) (in the case of NG, for example, (NO ₃ ) ^{− with} m / z = 62) If the threshold value stored in the database 16 does not exceed the threshold, it is determined that there is no substance to be detected and no alarm is sounded. On the other hand, as shown in the lower part of FIG. 13, the intrinsic ion intensity of m / z generated from the substance to be detected in (B) (in the case of NG, for example, (NO ₃ ) ^{− with} m / z = 62). When the threshold stored in the database 16 is exceeded, it is determined that there is a substance to be detected and an alarm is sounded.

[Example 5]
As another embodiment of the detection method according to the present invention, when the drift voltage is changed, the specific m / z fragment ion intensity generated from the detection target material becomes the specific m / z of the specific m / z generated from the detection target material. Focusing on whether or not the ion intensity is higher, an example of a method for determining the presence or absence of a detection target substance will be described.

FIG. 14 is a diagram illustrating an example of a mass spectrum when a substance to be detected exists and the intensity ratio of two ion peaks is reversed by changing the drift voltage. Based on the information in the database 16, when a mass spectrum is acquired with a drift voltage A (in the case of NG, for example, 40 V), a specific m / z ion intensity generated from the detection target substance in (A) (in the case of NG) For example, it is assumed that (M + NO ₂ ) ⁻ ion) at m / z = 289 exceeds the threshold value. However, there is a possibility that the ion peak of the contaminant exists at the same m / z, and the threshold value is exceeded as a result of addition.

Therefore, in order to separate the contamination component and the detection target component, the mass spectrum is acquired by changing the drift voltage to the voltage B (for example, 80 V in the case of NG) based on the information in the database 16. The inherent m / z fragment ion intensity generated from the detection target substance in (B) (in the case of NG, for example, (NO ₃ ) ^{− with} m / z = 62) exceeds the threshold value stored in the database 16. (For NG, for example, the m / z = 289 (M + NO 2) - ion) At this time detection of specific m / z generated from the target material ion peak of (A) because the to be dissociated, ionic strength is Decrease. Therefore, when the drift voltage is changed from A to B, the specific m / z ion intensity generated from the detection target material in (A) decreases, and the specific generation generated from the detection target material in (B). When the fragment ion intensity of m / z increases, it is judged that there is a substance to be detected, and an alarm is sounded.

[Example 6]
As another embodiment of the detection method according to the present invention, an embodiment in which the drift voltage and the mass spectrometry timing are synchronized will be described.

  When changing the drift voltage, it is necessary to synchronize the timing with mass spectrometry. FIG. 15 is a diagram showing an example of the operation sequence of the drift voltage according to the present embodiment in consideration of the detection timing. The horizontal axis is time, the upper vertical axis is the drift voltage, and the lower is the mass analysis timing. In this example, four types of detection target substances A, B, C, and D are detected.

When detection is started, the drift voltage (for example, 40 V in the case of NG) suitable for the detection target substance A (for example, NG) is changed based on the information in the database 16, and mass spectrometry is performed. At this time, the mass spectrometry is measured with a delay of several tens of milliseconds with respect to the change of the drift voltage. The detection target substance A is a highly volatile substance and is preferably measured first. A specific m / z ion peak (in the case of NG, for example, (M + NO ₂ ) ⁻ ion of m / z = 289) generated from the detection target substance A is detected from the mass analysis result. Next, based on the information in the database 16, the drift voltage (for example, 60 V in the case of TNT) is changed to a drift voltage suitable for the detection target substance B (for example, TNT), and mass spectrometry is performed. Then (in the case of TNT, for example, the m / z = 227 (M) ^- ion) ion peaks unique m / z generated from detection target substance B to detect. Furthermore, the drift voltage suitable for the detection target substances C and D is changed in order, and mass spectrometry is performed. Then, an intrinsic m / z ion peak generated from the detection target substances C and D is detected. Repeat this.

Now, when the drift voltage is set to a voltage suitable for the detection target substance B, an intrinsic m / z ion peak generated from the detection target substance B (in the case of TNT, for example, (M) ⁻ of m / z = 227). Ion) is detected. In this case, it immediately changes to a drift voltage (for example, 100 V in the case of TNT) suitable for generating fragment ions of the detection target substance B (in the case of TNT, for example, (M-OH) ⁻ of m / z = 210). I want to perform mass spectrometry. However, the drift voltage is changed from a voltage suitable for the detection target substance B to a voltage suitable for the detection target substance C before the result of mass spectrometry of the detection target substance B is obtained. Therefore, it is possible to perform efficient detection by performing mass analysis after performing mass analysis of the detection target substance C and then changing to a drift voltage suitable for generating fragment ions of the detection target substance B. . When a specific m / z fragment ion peak generated from the detection target substance B is detected, it is determined that the detection target substance B exists, and an alarm is sounded. Furthermore, the measurement is continued to check whether other substances to be detected exist.

  In the example shown in FIG. 15, the fragment ions of the detection target substance B are detected after the measurement of the detection target substance C. However, the detection of the fragment ions of the detection target substance B is generated from the detection target substance B. The timing may be any time after a unique m / z ion peak is detected.

[Example 7]
FIG. 16 is a diagram showing an embodiment of an apparatus according to the present invention in which a gas chromatograph (hereinafter referred to as GC) is mounted between a sample introducing device and an ion source.

  A sample to be detected is introduced into the sample introduction device 1. At this time, the sample to be detected was heated and evaporated after being collected by dropping or wiping directly on the collection paper. In addition to this method, it may be introduced directly like injection. The sample vapor (or sample fine particles) containing the vaporized detection target material is introduced into the ion source 3 through the heated GC 25. At this time, air, helium gas, nitrogen, or the like may be used as a carrier gas that flows to the GC 25. The suction pump 2 sucks at a flow rate of 0.5 liters per minute. The ion source 3 is heated to 150 ° C. with a heater so that sample vapor does not adhere inside. A needle-like electrode 4 is disposed in the ion source 3, a high voltage is applied between the ion source 3 and the counter electrode 5, and a corona discharge is generated near the tip of the needle-like electrode 4. By this corona discharge, nitrogen, oxygen, water vapor, etc. in the air are ionized to become primary ions. The generated primary ions move to the first pore 6 side by an electric field. In this embodiment, the inner diameter of the first pore 6 is about 0.1 mm. At this time, the sample vapor sucked from the sample introducer 1 reacts with the primary ions, whereby the sample vapor is ionized to become sample molecular ions.

  Since the generated sample molecular ions have a potential difference of about 1 kV between the counter electrode 5 and the first pore 6, the sample molecular ions enter the differential exhaust section through the first pore 6. In the differential exhaust section, adiabatic expansion occurs, and clustering in which solvent molecules adhere to ions occurs. In order to reduce this clustering, it is desirable to heat the first pores 6 with a heater or the like. In the present embodiment, the first pore 6 is heated to 180 ° C. with a heater. The differential exhaust unit is exhausted by a differential exhaust pump 7.

  The generated sample molecular ions are introduced into the mass spectrometer through the first pore 6, the differential exhaust portion, and the second pore 8. A drift voltage is applied between the first pore 6 and the second pore 8 by a drift voltage power source 9. This drift voltage drifts in the direction of the 2nd pore 8 by the ion taken in by the differential exhaust part, and the effect which improves the ion transmittance of the 2nd pore 8 remains in a differential exhaust part. There is an effect of desorbing solvent molecules such as water adhering to ions by collision with gas molecules. Further, when this drift voltage is further increased, the collision energy with the residual gas molecules is further increased, and a phenomenon occurs in which the sample molecule ions are dissociated.

  The sample molecular ions passing through the second pore 8 are efficiently converged on the quadrupole analysis tube 11 by applying a voltage to the electrostatic lens 10. The mass analyzer is evacuated by a vacuum pump 17. By controlling the frequency component and voltage applied to the quadrupole analysis tube 11 by the mass spectrometry control device 12, only ions having a target mass number are selected, passed, and detected by the detector 13. The arithmetic processing unit 14 changes the drift voltage with the drift power supply voltage 9 based on the information in the database 16 recorded in the storage device 15, and selects only ions having the target mass number with the mass spectrometry control unit 12. It passes through and is detected by the detector 13.

  By connecting the GC 25, the sample gas is separated by the GC 25 and introduced into the ion source. In particular, since the contaminant component is separated from the sample gas in the GC 25, the time for reaching the ion source varies. The time of the sample gas reaching the ion source can be set in advance by the type of GC 25, the temperature, the flow rate of the carrier gas, and the like. Therefore, the time from the sample introduction to the ion source is constant.

The drift voltage is detected based on the information in the database 16 in accordance with the time when the detection target substance (for example, in the case of NG) contained in the sample gas introduced into the sample introduction device reaches the ion source through the column. Is changed to an optimum voltage (in the case of NG, for example, 40 V). (For NG, for example, the m / z = 289 (M + NO 2) - ion) ion peaks unique m / z generated from detection target substance in the sample gas if exists, on the basis of the information in the database 16 The drift voltage is changed to a voltage (for example, 80 V in the case of NG) that generates fragment ions (in the case of NG, for example, (NO ₃ ) ^{− with} m / z = 62). When a specific m / z fragment ion peak (for example, (NO ₃ ) ⁻ of m / z = 62) generated from the detection target substance A is detected from the mass analysis result, the detection target substance A Sounds an alarm.

  When the GC 25 is used, the retention time for the substance to be detected to reach the ion source has a wide range, which is suitable for generating fragment ions by changing the drift voltage. A high speed GC may be used as the GC 25. Further, the same application is possible in a liquid chromatograph (LC).

  INDUSTRIAL APPLICABILITY The present invention can be applied to a technique for quickly identifying a substance to be detected from an unknown sample in environmental substance detection, harmful chemical substance detection, and narcotic and explosive detection techniques.

The figure which shows the apparatus structural example of this invention. The figure explaining an example of the operation sequence of a prior art. The figure which shows the example of the database which memorize | stores the information regarding a detection target substance. The figure which shows the example of S / N change by the drift voltage of TNT. The figure which shows the example of drift voltage dependence of m / z = 210 background peak. The figure which shows the example of S / N change by the drift voltage of NG. The figure which shows the example of drift voltage dependence of m / z = 62 background peak. The flowchart of the operation | movement which detects a fragment peak by changing a drift voltage. The figure which shows the operation | movement sequence example of a drift voltage. The figure which shows the example of an operation | movement sequence which considered the volatility of the detection target substance. The figure which shows the apparatus structural example which mounts the ion trap mass spectrometer in a mass spectrometer. The figure which shows the example of a mass spectrum in case a detection target substance does not exist. The figure which shows the example of a mass spectrum in case an impurity substance and a to-be-detected substance have the same m / z ion peak. The figure which shows the example of a mass spectrum in case a detection target substance exists and an intensity ratio reverses by changing a drift voltage. The figure which shows the example of an operation | movement sequence of the drift voltage which considered detection timing. The figure which shows the apparatus structural example which mounted | wore GC between the sample introducer and the ion source.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sample introduction device 2 Suction pump 3 Ion source 4 Needle-like electrode 5 Counter electrode 6 First pore 7 Differential exhaust pump 8 Second pore 9 Drift voltage power supply 10 Electrostatic lens 11 Quadrupole analysis tube 12 Mass spectrometry control Device 13 Detector 14 Arithmetic processing device 15 Storage device 16 Database 17 Vacuum pump 18 End cap electrode 19 End cap electrode 20 Ring electrode 21 Gate electrode 22 Quartz ring 23 Gas introduction tube 24 Gas supply device 25 Gas chromatograph

Claims (11)

A sample introduction part for introducing a sample gas;
An ion source that generates ions of the sample gas introduced from the sample introduction unit under atmospheric pressure;
The sample gas ions generated by the ion source are introduced through the first pores, sandwiched between the first partition walls having the first pores and the second partition walls having the second pores. A differential pumping portion derived through the second pore;
A power supply for applying a drift voltage between the first partition and the second partition;
A mass analyzer that measures the mass of the ions introduced through the second pores;
An arithmetic processing unit that determines whether or not a detection target substance is included in the sample gas based on the mass measured by the mass analyzing unit,
The arithmetic processing unit determines whether or not a mass of ions unique to the detection target substance exists in a first mass measured by applying a predetermined first drift voltage, and the unique ions If there is a mass of a fragment ion unique to the detection target substance in the second mass measured by changing the drift voltage to a predetermined second drift voltage The mass of the fragment ion specific to the substance to be detected exists in the second mass, and the intensity of the fragment ion is higher than the intensity of the ion specific to the substance to be detected, A mass spectrometer characterized by determining that the detection target substance is present in the sample gas . 2. The mass spectrometer according to claim 1, wherein when there are a plurality of detection target substances, the arithmetic processing unit generates a drift voltage suitable for an ion component of a first detection target substance among the plurality of detection target substances. When it is determined that there is no ion mass specific to the first detection target substance as the first drift voltage, the second detection target is lower in volatility than the volatility of the first detection target substance. A mass spectrometer that sets a drift voltage suitable for an ion component of a substance as the first drift voltage. 2. The mass spectrometer according to claim 1, wherein when there are a plurality of detection target substances, the arithmetic processing unit generates a drift voltage suitable for an ion component of a first detection target substance among the plurality of detection target substances. When the first drift voltage is used and it is determined that there is a mass of ions unique to the first detection target substance, the second detection target substance is lower in volatility than the volatility of the first detection target substance. Is set as the first drift voltage, and then the drift voltage suitable for generating fragment ions of the first detection target substance is set as the second drift voltage. A mass spectrometer characterized by that. The mass spectrometer according to claim 1,
For detection of the mass number of ions specific to the detection target substance, the first drift voltage suitable for detection of the ions and the detection threshold of the ions, and the mass number of fragment ions of the detection target substance and the fragment ions A storage unit storing a suitable second drift voltage and a detection threshold value of the fragment ion;
The mass spectrometer according to claim 1, wherein the arithmetic processing unit performs the determination by comparing the mass measured by the mass analyzing unit with information stored in the storage unit. 2. The mass spectrometer according to claim 1 , wherein the ion source has means for generating a corona discharge.   The mass spectrometer according to claim 1, wherein the mass spectrometer is a quadrupole mass spectrometer.   The mass spectrometer according to claim 1, wherein the second drift voltage is higher than the first drift voltage.   The mass spectrometer according to claim 1, wherein a column of a gas chromatograph is connected between the sample introduction unit and the ion source. In a method of detecting a substance to be detected in a sample gas using a mass spectrometer,
A first analysis step of acquiring a mass by applying a first drift voltage suitable for detecting a first m / z ion specific to the substance to be detected to the mass spectrometer;
A first determination step of determining whether or not the first m / z ion is detected;
When it is determined in the first determination step that the first m / z ion is detected, a second drift voltage suitable for dissociating the first m / z ion is determined by the mass spectrometry. A second analysis step that is applied to a meter to obtain mass;
A second determination step of determining whether or not a second m / z ion generated by dissociation of the first m / z ion is detected ;
In the second determination step, it is determined that the second m / z ion is detected, and the intensity of the second m / z ion is higher than the intensity of the first m / z ion. And determining that the detection target substance is present in the sample gas,
A detection method comprising:   The detection method according to claim 9, wherein the first drift voltage and the second drift voltage are read from a database.   The detection method according to claim 9, wherein the mass spectrometer ionizes a sample gas under atmospheric pressure.

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