JP5125248B2 - Ion mobility spectrometer - Google Patents

Description

  The present invention relates to an ion mobility spectrometer.

There is an increasing demand for monitoring devices for detecting explosives, chemical agents (toxic substances used in chemical terrorism, etc.), illegal drugs such as narcotics, and various environmental pollutants. Since mass spectrometry provides information on molecular weight, it has the advantage of being able to detect a target substance with high selectivity from various mixtures. Therefore, the monitoring device based on mass spectrometry has a feature that there are few false alarms (false positives). However, since the mass spectrometer requires a vacuum system, there is a problem that the apparatus is large. The selectivity of a mass spectrometer depends on the mass resolution, and the higher the resolution, the higher the selectivity.
However, in general, the resolution of the mass spectrometer and the apparatus size are in a trade-off relationship, and the apparatus becomes larger when the resolution is increased. In addition, it is known that the selectivity of a mass spectrometer is remarkably improved because information on a partial structure of a molecule can be obtained by equipping a tandem mass spectrometry function. However, in order to perform tandem mass spectrometry, it is necessary to introduce a target gas into the vacuum apparatus in order to collide and dissociate ions. Therefore, it is necessary to increase the evacuation capacity, and the apparatus becomes large.

  Attempts have been made to improve selectivity while keeping the size of the mass spectrometer unchanged. For example, Patent Document 1 discloses a chemical agent detection method using a mass spectrometer. According to this, protonation molecule (M + H) +, which is a molecular weight related ion, is generated when sarin, which is a target substance, is ionized by corona discharge in the atmosphere. Dissociation occurs due to collision with residual gas in the exhaust part, and dissociated ions are generated. By determining that sarin has been detected when both molecular weight related ions and dissociated ions are detected, selectivity is improved and false alarms are reduced.

  On the other hand, an ion mobility spectrometer (IMS) that identifies substances based on a difference in ion mobility at or near atmospheric pressure is known. Since IMS does not require a vacuum system, it is easy to miniaturize the device, and a palm-sized monitoring device using this device is also commercially available. However, IMS is generally less selective than mass spectrometry, and as a result, there are problems with many false alarms. Therefore, attempts have been made to improve the selectivity of IMS. For example, Patent Document 2 discloses a dopant that can selectively ionize a narcotic substance.

Japanese Patent No. 3787116 Japanese Patent No. 3045655

  In the mass spectrometer described in Patent Document 1, the molecular weight related ions of the measurement target substance are generated in the ion source, and the molecular weight related ions and a part thereof are generated by dissociation in the differential exhaust part of the mass spectrometer. The selectivity is improved by determining that the substance to be measured is detected when both dissociated ions are detected. However, just observing in the mass spectrum the ion related to the molecular weight of the substance to be measured and the ion of the mass-to-charge ratio corresponding to the dissociated ion does not guarantee that one is the other dissociated ion. That is, the reliability cannot be said to be sufficient, and the effect of improving the selectivity is limited. This technique is a method of generating dissociated ions by collisional dissociation between ions and gas molecules inside the vacuum apparatus, and is realized in a mass spectrometer that requires a vacuum system. Therefore, it is not suitable for downsizing of the apparatus.

Patent Document 2 discloses a technique for improving the selectivity of IMS that does not require a vacuum system. According to this, when analyzing an alkaloid-based narcotic substance, the narcotic substance can be selectively ionized by adding ammonia or nicotinamide to the ion source. However, the selectivity is limited because it has the same effect on a substance having similar chemical properties to the analyte. In addition, it is common to measure multiple substances with a single device, but in that case, it is necessary to prepare multiple dopant substances and switch them for each substance to be measured, which complicates the equipment. Or it will enlarge and operation will also become complicated.
An object of the present invention is to provide a monitoring device with high selectivity while being a small analyzer that does not require a vacuum system.

  IMS is equipped with two types of ion sources, an ion source that generates molecular weight-related ions (non-dissociative ion source) and an ion source that generates dissociated ions (dissociable ion source). A switching mechanism with the dissociative ion source is provided. Further, the non-dissociable ion source mainly means an ion source from which molecular weight related ions are generated. Further, the dissociative ion source means an ion source that mainly generates dissociated ions.

  In addition, the molecular weight related ions generated by the non-dissociable ion source and the characteristic values of the dissociated ions generated by the dissociative ion source (ion mobility or values correlated therewith) are registered in the database. When ions matching the database are detected in both the non-dissociative ion source and the dissociative ion source, it is determined that the measurement target substance has been detected. At this time, reliability is improved by investigating the presence / absence of dissociated ions during the operation of the non-dissociative ion source and conversely checking the presence / absence of molecular weight related ions during the operation of the dissociative ion source. To do.

  Switching between dissociative and non-dissociative ion sources is realized by switching the direction in which the sample flows through the discharge part in the atmospheric pressure chemical ionization method using corona discharge. Alternatively, it can be realized by switching between atmospheric pressure ionization by a radiation source and atmospheric pressure chemical ionization by corona discharge. An ultraviolet irradiation method can also be applied as the dissociative ion source.

  According to the present invention, it is possible to realize a monitoring device with high selectivity while being a small analyzer that does not require an advanced vacuum system.

  FIG. 1 shows a first configuration of the ion mobility spectrometer of the present invention. This device can be used to detect molecular toxic substances and hazardous substances contained in the atmosphere. This device is roughly divided into an atmospheric pressure ion source, a separation unit (so-called drift tube) for spatially separating ions generated by the atmospheric pressure ion source based on a difference in ion mobility, and separated ions. It is comprised from the detector for detecting. The atmospheric pressure ion source, separation unit, and detector are controlled by the control unit 1.

  The atmospheric pressure ion source has a pipe for passing the atmosphere and a corona discharge part for generating a corona discharge inside the pipe. The corona discharge part is composed of a discharge needle 3 and a counter electrode 4. Fans 5 and 6 are provided for flowing air on both sides of the corona discharge part. The air flow direction of the fans 5 and 6 is such that when one fan is operated, the air flows from the discharge needle toward the counter electrode, and when the other fan is operated, the reverse direction, that is, from the counter electrode 4 toward the discharge needle 3 It is set so that the atmosphere flows. Here, the former flow direction is referred to as forward flow, and the latter flow direction is referred to as reverse flow. In order to reduce dust or moisture in the atmosphere, filters 7 and 8 are attached to both ends of the pipe.

  As for the drift tube and the detector 15, various configurations adopted in the conventional IMS can be applied. In FIG. 1, one of the simplest configurations is used. An electrode stack 14 in which ring-shaped electrodes 11 and insulating materials 12 are alternately stacked in the direction from the ion source side to the detector side is disposed inside the drift tube. Adjacent ring electrodes are electrically connected via an electrical resistance. The ring-shaped electrode closest to the ion source in the electrode stack 14 is a grid electrode 13 having a grid-like opening.

  Both positive ions and negative ions are generated in the discharge part. In the positive ion mode for measuring positive ions, the discharge needle 3 is set to a positive potential with respect to the counter electrode 4 to generate corona discharge. At this time, the grid electrode 13 is set at a lower potential than the counter electrode 4 and the adjacent ring electrode. By doing so, positive ions generated in the ion source enter the drift tube and accumulate in the vicinity of the grid electrode 13. Next, by switching the potential of the grid electrode 13 to an intermediate potential between the counter electrode 4 and the adjacent ring electrode, the ions accumulated in the vicinity of the grid electrode 13 move toward the detector all at once, depending on the difference in ion mobility. Each reaches a detector at a different time and is detected as an ion current. An ion mobility spectrum is obtained by plotting the flight time of ions from the time when the potential of the grid electrode is switched to a high potential until reaching the detector on the horizontal axis and the signal intensity on the vertical axis.

  In the negative ion mode for measuring negative ions, an ion mobility spectrum is obtained in the same sequence as in the positive ion mode, except that the potentials of the discharge needle 3 and each electrode are inverted.

  Inside the drift tube, a counter gas is allowed to flow in a direction substantially opposite to the ion traveling direction, that is, in a direction from the detector side toward the ion source side. A counter gas flow is generated by the fan 9. At this time, impurities in the gas are removed by the filter 10. By flowing the counter gas, the degree of ion separation is improved as compared to the case where the counter gas is not.

  FIG. 2 shows the types of ions generated when ionizing with the ion source of FIG. 1 by adding trinitrotoluene (TNT), which is one type of explosive, to the laboratory atmosphere. This figure is a mass spectrum obtained by connecting a mass spectrometer to the ion source of FIG. The sample flow at this time is a reverse flow, and the polarity of the ions is negative. The figure shows that a main peak is observed at m / z = 227. This ion is considered to be a molecular ion (M-) of TNT from its mass-to-charge ratio. Peaks are also observed at m / z = 210 and m / z = 197, which are considered to be dissociated ions of TNT (M-OH)-and (M-NO)-, respectively, but the intensity is higher than that of molecular ions. weak. When the ion source is switched to the forward flow, the mass spectrum shown in FIG. 3 is obtained. Many peaks that were not observed in the backflow configuration were observed, and most of them are considered to be dissociated ions of TNT, as shown in the figure. Although molecular ions of TNT are also observed, they are weaker than some dissociated ions. Thus, it can be seen that the generation of molecular ions of TNT and the generation of dissociated ions can be controlled by switching backflow and forward flow in the negative ion mode. That is, switching between a non-dissociable ion source that mainly generates molecular weight-related ions and a dissociative ion source that mainly generates dissociated ions is realized.

  An experiment similar to that of TNT was also conducted for o-nitrotoluene (o-MNT), one of the explosive detection agents. The results are shown in FIG. 4 and FIG. FIG. 4 shows a mass spectrum which is a result of analyzing with a mass spectrometer the types of ions generated in the negative ion mode of reverse flow. An ion of m / z = 137, which is considered to be a molecular ion of o-MNT, is strongly observed, and almost no dissociated ions are observed. FIG. 5 shows a mass spectrum which is a result of analyzing the types of ions generated in the forward negative ion mode with a mass spectrometer. (MO)-, (M-NO + H)-and (M-NO2 + H)-, which are considered to be dissociated ions of o-MNT at m / z = 121, 108, 92, respectively, in addition to molecular ions Observed. At m / z = 153, a peak considered to be an oxygen addition ion of o-MNT is also observed. Thus, it can be seen that the generation of molecular ions and the generation of dissociated ions can also be controlled for o-MNT by switching between reverse flow and forward flow in the negative ion mode. That is, switching between the non-dissociative ion source and the dissociative ion source is realized.

  In constructing the database 2, the gas of the substance to be measured is mixed with the laboratory atmosphere or similar air (for example, pure air with water added), and an ion mobility spectrum is acquired. The spectrum is measured with an ion source in a non-dissociation mode and a dissociation mode, and the flight time of the molecular weight related ions of the measurement target substance and the dissociated ions is examined. This is performed for each substance to be measured, and the time of flight of each molecular weight related ion and dissociated ion is stored in the database 2.

  FIG. 6 shows an example of a measurement algorithm in actual operation. Specify the measurement target substance and start measurement. Next, the ion source is set to a non-dissociation mode and the presence or absence of molecular weight related ions is examined. Here, the presence or absence of an ion is checked by comparing the signal intensity at the time of flight of the ion stored in the database 2 with a preset threshold, and if the signal intensity exceeds the threshold, the ion exists. If it is not, it means that it is determined that the ion does not exist. The threshold is set in consideration of ionization efficiency and the like. Specifically, a calibration curve is acquired in advance, and it is determined based on the signal intensity at the alarm alarm concentration. When molecular weight-related ions are detected in the non-dissociation mode, that is, when the signal intensity (M1) exceeds the threshold value (X1), the ion source is switched to the dissociation mode to check for the presence of dissociated ions. When dissociated ions are detected, that is, when the signal intensity (F1) exceeds the threshold value (Y1), it is determined that the measurement target substance has been detected, and an alarm is displayed. Of course, when the dissociated ion mode is first detected and the dissociated ions are detected, the ion source may be switched to the non-dissociated mode to check for the presence of molecular weight related ions. In FIG. 6 and the description thereof, for the sake of simplification, it is assumed that there is only one kind of measurement target substance. However, in actual operation, it is almost always necessary to detect a plurality of substances. When there are a plurality of substances to be measured, the presence / absence of the second target substance is determined in addition to the presence / absence of the first substance to be measured in A5 in the algorithm of FIG. If one of them exists, go to A6 of the algorithm. In A8 of the algorithm, the presence or absence of the dissociated ions is determined for the measurement target substance in which the molecular weight related ions are detected in A5.

  In the measurement of the ion mobility spectrum, all ions having a certain range of ion mobility determined by the relationship between the magnitude of the electric field inside the drift tube and the flow velocity of the counter gas can be measured. Therefore, even if the number of substances to be measured increases, the measurement time does not change if these molecular weight related ions and dissociated ions are within the measurement range. In addition, the calculation time required to determine the presence or absence of ions is negligible compared to other times. Therefore, it is possible to increase the number of substances to be measured without extending the measurement time.

  In the above operation method, by using the determination logic that also uses the signal intensity of the dissociated ions in the non-dissociation mode and the signal intensity of the molecular weight-related ions in the dissociation mode, the reliability of the determination can be improved. For example, in the non-dissociation mode, when the molecular weight related ion is detected and the dissociated ion is not detected, and when the dissociated ion is detected and the molecular weight related ion is not detected in the dissociation mode, it is determined that the measurement target substance is detected. To do. Note that the threshold for determining the presence or absence of molecular weight related ions in the dissociation mode is not necessarily the same as the threshold for determining the presence or absence of molecular weight related ions in the non-dissociation mode. Similarly, the threshold for determining the presence or absence of dissociated ions in the non-dissociation mode is not necessarily the same as the threshold for determining the presence or absence of dissociated ions in the dissociation mode.

  When there are multiple dissociated ions of a target substance, only one of them may be used for detection of the target substance, but various determination logics based on the presence or absence of multiple dissociated ions can be used. Can be assembled. For example, detection of both two dissociated ions can be a necessary condition for determining that the measurement target substance has been detected, and that any one of the two dissociated ions can be detected. It may be a necessary condition. For example, if there is a possibility of fatal damage if a detection failure occurs, such as when detecting an explosive, the latter judgment logic is used to reduce the detection failure, and even if a detection failure such as drug detection occurs, the damage will occur. If the number is small, the former logic is used to reduce false positives, so that it is possible to respond flexibly according to the purpose.

  In the present invention, the molecular weight related ions are not limited to molecular ions, but may be additional ions in which other ions such as dopant ions are added to the molecules. The dissociated ions may be molecular ions generated by dissociating additional ions or molecular dissociated ions.

  FIG. 7 shows a second configuration of the ion mobility spectrometer of the present invention. This apparatus is the same as the apparatus of FIG. 1 in that it includes an atmospheric pressure ion source, a drift tube, and a detector, but the structure of the ion source is different from that of FIG. This ion source includes one pipe 21 and one fan 21 for passing the air through the pipe in one direction. The air is sucked from the filter 22 attached to one end of the pipe, and exhausted from the other end 29 of the pipe through the inside of the pipe. There are two corona discharge parts inside the pipe. In the first discharge section, the discharge needle 26 and the counter electrode 28 are arranged in this order from the upstream side with respect to the atmospheric flow to constitute a forward flow mode atmospheric pressure chemical ion source. The second discharge part is located on the downstream side of the first discharge part, and the counter electrode 27 and the discharge needle 25 are arranged from the upstream side with respect to the atmospheric flow to constitute an atmospheric pressure chemical ion source in the reverse flow mode. . A part of the side wall of the pipe is opened between the first and second discharge parts, that is, between the two counter electrodes, and communicates with the drift tube. A mesh electrode 24 is disposed in the open portion, and is set to a potential lower than that of the two counter electrodes. An extrusion electrode 23 is disposed on the opposite side wall of the mesh electrode, and is set at a higher potential than the mesh electrode 24. By such potential setting, an electric field for introducing ions existing between the two counter electrodes into the drift tube is formed.

   By operating only one of the two discharge parts, either the dissociation mode or the non-dissociation mode is realized. The operation of the discharge unit is controlled by setting the voltage applied to the discharge needle. Since the method for detecting and determining the substance to be measured by switching between the dissociation mode and the non-dissociation mode is the same as that in the case of the apparatus in FIG.

  In this apparatus, by operating two discharge parts simultaneously, ions generated in dissociation mode and non-dissociation mode can be measured simultaneously. In this case, both molecular weight related ions and dissociated ions are observed in the spectrum. When both ions are detected, it is determined that the measurement target substance has been detected. According to this method, since it is not necessary to switch the ion source, there is an advantage that a highly reliable determination can be made in about half a short time as compared with the apparatus having the configuration of FIG. However, in this method, it is unclear whether ions determined to be dissociated ions are derived from a dissociative ion source. Similarly, it is unclear whether ions determined to be molecular weight related ions are derived from non-dissociable ion sources. Therefore, as shown in the measurement algorithm of FIG. 8, when molecular weight-related ions and dissociated ions are detected in algorithms B5 and B6, respectively, the process proceeds to algorithm B7, where only the discharge part in dissociation mode is operated to Check for presence. By determining that the measurement target substance is detected when no molecular weight related ions are detected in algorithm B9, the accuracy of the determination is improved. Further, proceed to Algorithm B10, operate only the discharge part in the non-dissociation mode to check for the presence of dissociated ions, and if it is determined that the substance to be measured is detected on condition that no dissociated ions are detected in Algorithm B12, The certainty of the is further improved

FIG. 9 shows a third configuration of the ion mobility spectrometer of the present invention. This apparatus is the same as the apparatus of FIG. 1 in that it includes an atmospheric pressure ion source, a drift tube, and a detector, but the structure of the ion source is different from that of FIG. In this apparatus, a back-flow atmospheric pressure chemical ionization method is used as a non-dissociative ion source, and an ionization method using a radiation source is used as a dissociative ion source. A foil such as ⁶³ Ni is used as the radiation source 41 and is affixed in the pipe. High energy electrons are generated from the radiation source 41, and thereby oxygen molecules, water molecules, etc. in the atmosphere are ionized. The substance to be measured may be directly ionized by collision with electrons, but in many cases, it is ionized by ion-molecule reaction with a large amount of oxygen molecular ions and water molecular ions. It is known that certain ions further react with electrons to generate their dissociated ions.

  When the ion source is operated in the non-dissociation mode, the fan 31 is rotated so that the air is sucked from the filter 33 attached to the first intake port while the corona discharge unit is operated. Part of the sucked air flows through the corona discharge portion in the direction from the counter electrode 4 toward the discharge needle 3, that is, in the reverse flow direction, and is exhausted from the exhaust port 30. The remaining atmosphere passes through the radiation source 41 and is exhausted to the atmosphere through the filter 32 attached to the intake / exhaust port. At this time, ions generated by the radiation source 41 are also exhausted into the atmosphere, and therefore do not enter the drift tube. Ions generated in the corona discharge part move into the drift tube by the electric field force. When the ion source is operated in the dissociation mode, the rotation direction of the fan 31 is reversed after the corona discharge is stopped. At this time, as shown in the drawing, the air is sucked from the filter 32 that is an intake / exhaust port and exhausted from the filter 33 that is an intake / exhaust port. At this time, ions are generated in the radiation source section. The generated ions flow through the pipe and move into the drift tube due to a potential difference provided between the counter electrode and the drift tube. Apart from this, the atmosphere is also sucked through the corona discharge part, but the components in the atmosphere are exhausted from the filter 33 which is an inlet / outlet without being ionized. In this configuration, since the flow passing through the corona discharge unit merges with the flow passing through the radiation source unit, the flow from the radiation source unit is pressed against the drift tube side. Therefore, the efficiency of introducing ions into the drift tube is improved.

  FIG. 10 shows a fourth configuration of the ion mobility spectrometer of the present invention. This apparatus comprises an atmospheric pressure ion source, an atmospheric pressure ion filter, and a detector. The atmospheric pressure ion source has the same configuration as that shown in FIG. The atmospheric pressure ion filter is based on the principle of FAIMS (High-Field Asymmetric Waveform Ion Mobility Spectrometry). A high voltage of about several kV and a low voltage of about several volts are alternately applied between the two parallel plate electrodes 51 and 52 by a power source 50 at a constant cycle, and a direct current voltage (herein called a filter voltage) is applied. Apply by overlapping. As a result, only ions having a specific ion mobility pass through the filter and reach the detector. The ion mobility of ions passing through the filter depends on the filter voltage. Therefore, the ion mobility spectrum is obtained by scanning the filter voltage and plotting the filter voltage on the horizontal axis and the signal intensity on the vertical axis.

  In constructing the database 2, the gas of the substance to be measured is mixed with the laboratory atmosphere or similar air (for example, pure air with water added), and an ion mobility spectrum is acquired. The spectrum is acquired by switching the ion source between the non-dissociation mode and the dissociation mode, and the filter voltage value at which the molecular weight related ions of the measurement target substance and the dissociated ions are detected is acquired. This is performed for each substance to be measured, and the filter voltage values corresponding to the respective molecular weight related ions and dissociated ions are stored in the database 2. When determining whether or not a certain ion exists, the filter voltage value at which the ion passes through the filter is set with reference to the database 2. If the signal intensity obtained at this time exceeds a preset threshold value for the ion, it is determined that the ion is present. Since the logic for switching the dissociation mode and the non-dissociation mode to detect and determine the substance to be measured is the same as in the case of the apparatus in FIG. When an ion filter is used, the duty cycle is higher than that of the time-of-flight device as shown in FIG.

FIG. 11 shows an example of the measurement algorithm. This is a case where there is one kind of measurement target substance, but when measuring a plurality of measurement target substances, it is necessary to change the filter voltage for each measurement target substance. Therefore, the algorithms C3 to C8 in FIG. 11 are repeated.
As the ion filter, other methods such as an ion mobility analyzer can be used.

  The present invention is particularly used for monitoring devices for detecting explosives, chemical agents (toxic substances used in chemical terrorism, etc.), illegal drugs such as narcotics, various environmental pollutants, and the like.

The 1st structure of the ion mobility spectrometer of this invention. Mass spectrum of negative ions generated when TNT is ionized with an atmospheric pressure chemical ion source in reverse flow mode Mass spectrum of negative ions generated when TNT is ionized with an atmospheric pressure chemical ion source in forward flow mode Mass spectrum of negative ions generated when o-MNT is ionized with an atmospheric pressure chemical ion source in reverse flow mode Mass spectrum of negative ions generated when o-MNT is ionized with atmospheric chemical ion source in forward flow mode An example of a measurement algorithm. The 2nd structure of the ion mobility spectrometer of this invention. An example of the measurement algorithm of the ion mobility spectrometer of a 2nd structure. The 3rd structure of the ion mobility spectrometer of this invention. 4th structure of the ion mobility spectrometer of this invention. An example of the measurement algorithm of the ion mobility spectrometer of a 4th structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Control part, 2 ... Database, 3, 25, 26 ... Discharge needle | hook, 4, 27, 28 ... Counter electrode 5, 6, 9, 21, 31 ... Fan, 7, 8, 10, 22, 32, 33 ... Filter, 11 ... Ring-shaped electrode, 12 ... Insulating material, 13 ... Grid electrode, 14 ... Electrode stack,
15 ... Detector, 23 ... Extruded electrode, 24 ... Mesh electrode, 29 ... Exhaust port,
30 ... Intake / exhaust port, 41 ... Radiation source, 50 ... Power source, 51, 52 ... Parallel plate electrode.

Claims (6)

First and second ion sources for ionizing sample molecules;
An analyzer for measuring a characteristic value of the ion and a signal amount of the ion;
A characteristic value of molecular weight related ions of the sample molecules generated in the first ion source, a threshold value of signal intensity for determining the presence or absence of the molecular weight related ions, and the sample generated in the second ion source A database storing characteristic values of dissociated ions of molecules and a threshold value of signal intensity for determining the presence or absence of the dissociated ions;
A calculation unit for determining the presence or absence of the sample molecule,
The first ion source has a corona discharge portion configured such that a pair of discharge needles and a plate electrode are opposed to each other, and a reverse flow type atmospheric pressure chemical ion source in which a sample gas flows from the plate electrode toward the discharge needle And
The second ion source has a corona discharge portion configured such that a pair of discharge needles and a plate electrode are opposed to each other, and a forward flow type atmospheric pressure chemical ion source in which a sample gas flows from the discharge needle toward the plate electrode. This is a chemical substance analyzer characterized by that . 2. The chemical substance analyzer according to claim 1, further comprising a switching unit that switches between an analysis process of ions generated by the first ion source and an analysis process of ions generated by the second ion source. Characteristic chemical substance analyzer. 2. The chemical substance analyzer according to claim 1, wherein the first and second ion sources share a corona discharge portion constituted by the pair of discharge needles and a plate electrode, and the flow direction of the sample gas is changed to the first gas source. A chemical substance analyzer characterized by having a switching mechanism for switching between a reverse flow type and the forward flow type. 2. The chemical substance analyzer according to claim 1, wherein the first and second ion sources are arranged so that the plate electrodes are opposed to each other, and the molecular weight related ions and the dissociated ions are extracted from between the plate electrodes. A chemical substance analyzer configured to be introduced into the analyzer. First and second ion sources for ionizing sample molecules;
An analyzer for measuring a characteristic value of the ion and a signal amount of the ion;
A characteristic value of molecular weight related ions of the sample molecules generated in the first ion source, a threshold value of signal intensity for determining the presence or absence of the molecular weight related ions, and the sample generated in the second ion source A database storing characteristic values of dissociated ions of molecules and a threshold value of signal intensity for determining the presence or absence of the dissociated ions;
A calculation unit for determining the presence or absence of the sample molecule,
The first ion source has a corona discharge portion configured such that a pair of discharge needles and a plate electrode are opposed to each other, and a reverse flow type atmospheric pressure chemical ion source in which a sample gas flows from the plate electrode toward the discharge needle And
2. The chemical substance analyzer according to claim 1, wherein the second ion source is an atmospheric pressure chemical ion source having a radiation source . 6. The chemical substance analyzer according to claim 5, wherein the sample gas is configured to flow in the order of the second ion source and the first ion source, and the second ion source and the first ion source. A chemical substance analyzer configured to extract the molecular weight related ions and the dissociated ions from an intermediate region and introduce them into the analyzer.

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