JP6023640B2 - Atmospheric pressure ionization method and atmospheric pressure ion source - Google Patents

Description

  The present invention relates to an atmospheric pressure ionization method and an atmospheric pressure ion source.

  Various methods are known as ionization methods. Recently, atmospheric pressure ionization method using excited gas molecules (atoms) having no charge called DART (Direct Analysis in Real Time) (US registered trademark). Is attracting attention. In this method, excited molecules generated by corona discharge or glow discharge are reacted with a sample under atmospheric pressure, the sample is ionized, and introduced into an ion inlet (hereinafter referred to as an orifice) of a mass spectrometer.

  The principle diagram of DART is shown in FIG. DART is composed of three rooms that communicate with each other at almost atmospheric pressure. First, the first chamber 51 includes a needle electrode 55 and has a role of generating excited molecules by corona discharge or glow discharge. A gas introduction pipe 54 for introducing a carrier gas such as helium, neon, or nitrogen is connected to the first chamber 51 so that the first chamber 51 can be filled with gas. Hereinafter, helium will be described as an example.

A partition 56 (counter electrode) between the first chamber 51 and the second chamber 52 is set to a ground potential, and a corona is provided between the needle electrode 55 attached to the first chamber 51 and the partition 56. Discharge or glow discharge can be caused. By this corona discharge or glow discharge, for example, a part of the ground singlet molecular helium gas He (1 ¹ S) introduced into the first chamber 51 is ionized to generate helium ions He ⁺ and electrons e ^−. , A part of the excited triplet molecule He (2 ³ S) excited to 19.8 eV is generated.

The helium ions He ⁺ , electrons e ⁻ and excited triplet molecules He (2 ³ S) generated in the first chamber 51 in this way are carried on the flow of helium gas that has not been affected by the discharge, and the second It flows into the room 52. A partition 57 (perforated disk electrode) between the second chamber 52 and the third chamber 53 is set to about 100 V, and a potential gradient is provided between the second chamber 52 and the ground potential partition 56. Therefore, the partition 57 blocks helium ions He ⁺ and electrons e ⁻ generated in the first chamber 51 and allows only neutral helium gas and excited triplet molecule He (2 ³ S) to pass through. That is, helium ions He ⁺ are reflected by the partition 57 and electrons e ⁻ are absorbed by the partition 57.

The helium gas that has flowed into the third chamber 53 together with the excited triplet molecule He (2 ³ S) is heated in the third chamber 53 by a heater (not shown). This heating is performed for the purpose of assisting vaporization and thermal desorption of the sample.

  The outlet 58 of the third chamber 53 is a grid electrode (partition), and a voltage of about 250 V is applied. On the other hand, since a voltage of about 30 V is applied to the orifice 100, a potential gradient in which positive ions are accelerated from the outlet 58 of the third chamber 53 toward the orifice 100 is generated.

  Normally, in DART, the generated excited gas molecules are smoothly moved on the helium gas flow, so that the needle electrode 55 and the openings of the partition 56, the partition 57, and the outlet 58 are arranged on a straight line L. The gas ejection axis from the outlet 58 coincides with the straight line L.

Neutral excited triplet molecule He (2 ³ S) heated in the third chamber 53 is taken out into the atmosphere on the flow of helium gas ejected through the outlet 58 and arranged in the flow. The sample 59 is contacted to ionize the sample. That is, the excited triplet molecule He (2 ³ S) reacts with water molecules in the atmosphere to penning ionize the water molecules. The positive ions of the water molecules react with water in the atmosphere to form water cluster positive ions, and further, the water cluster positive ions react with the sample 59 and the sample ions MH ⁺ in which protons H ⁺ are added to the sample molecules M. Produces. The sample 59 may be solid or liquid.

FIG. 2 shows this ionization mechanism. The positive ions MH ⁺ generated based on the mechanism shown in FIG. 2 are attracted and sucked into the orifice 10 in accordance with the potential gradient generated from the outlet 58 of the third chamber 53 toward the orifice 100, and a mass spectrometer (not shown). Is subjected to mass spectrometry.

  In addition, although the above example is an example when a positive ion produces | generates, when a negative ion produces | generates, it is necessary to reverse the direction of the electric potential gradient applied between the exit part 58 and the orifice 100. FIG. .

US Pat. No. 6,949,741.

WO 2004/098743.

JP-T-2006-523367.

It is a structural diagram of a DART ion source. It is a figure explaining the ionization mechanism by DART ionization method. It is a figure which shows an example of the conventional DART ionization apparatus. It is one Example of the DART ionization apparatus concerning this invention. It is one Example of the DART ion source concerning this invention. It is another Example of the DART ion source concerning this invention.

  An example of a conventional configuration for spraying excited molecules on a sample in such a DART ion source is shown in FIG.

  A DART ion source 11 set at a predetermined distance 14, a height 15, and an installation angle 13 is fixed to a support column 10-2 that is vertically set on the installation rail 10-1. The precise alignment is performed by adjusting screws 16 and 17.

  A sample substrate 3 on which the dropped sample 4 is placed is placed in front of the spray nozzle 12 of the DART ion source 11. Excited molecules ejected from the injection nozzle 12 together with helium gas (hereinafter, excited molecules ejected together with helium gas are referred to as “excited gas”) are sprayed on the surface of the sample 4 placed in the ejection direction, and the sample 4 is ionized. To do.

  The generated sample ions are introduced into the ion inlet 23 on the atmospheric pressure interface 22 and subjected to mass analysis by the mass spectrometer 21.

  According to such a configuration, the excited molecules can be sprayed from the oblique direction to the sample. (1) Even if the sample is a large lump, a part of the surface is ionized to be applied to the mass spectrometer. There are merits that (2) the sample can be ionized with the spot, and the ionized spot can be scanned two-dimensionally by changing the ejection direction, for example.

However, if the angle of the ion source is changed, the direction of the excitation gas flow changes, and the position where the gas flow passes with respect to the ion inlet 23 also changes. However, since the excitation gas flow is colorless and transparent, it can be visually confirmed. However, it took time to grasp the ionization point on the sample surface while adjusting the angle, height, and distance.
Conventionally, in order to cope with this problem, a sample substrate on which a calibration sample is dropped is inserted into an area assumed to be an ionization point of DART, and the intensity of the mass spectrum obtained by the mass spectrometer 21 is monitored accurately. It was a laborious and repetitive task of searching for the ionization point of a DART.

  In addition, even when the excitation gas is blown in the horizontal direction rather than in the oblique direction, the ionization point cannot be visually confirmed in the past, so the target sample spot is accurately inserted into the DART ionization point. In many cases, the sample was unnecessarily ionized.

  For example, when measuring a sample first developed on a TLC (thin layer chromatography) plate, the excitation gas flow is moved (scanned) around the target sample spot to avoid wasting the sample. The method to make was taken. In this method, measurement omission does not occur, but a portion where the sample does not exist is also measured, resulting in a time loss.

  In view of the above points, an object of the present invention is to provide an atmospheric pressure ionization method and an atmospheric pressure ion source that can easily find a DART ionization point and align a sample spot by a visual method.

  In order to achieve this object, the atmospheric pressure ionization method according to the present invention is an atmospheric pressure ionization method in which a sample is ionized by irradiating excited particles or charged particles generated by discharge or a high electric field under atmospheric pressure. A laser light source that generates laser light is arranged so that the sample is irradiated coaxially with the axial direction in which the excited particles or charged particles are irradiated, and the ionization point of the sample is irradiated from the laser light source. It is characterized in that it is discriminated by the point where the irradiated laser beam hits.

An atmospheric pressure ion source according to the present invention includes an atmospheric pressure ion source that ionizes a sample by irradiating the sample with excited particles or charged particles generated by discharge or a high electric field under atmospheric pressure,
A laser light source that generates laser light in a visible region, the laser light being arranged so that the sample is irradiated coaxially with an irradiation axis direction irradiated with the excitation particles or charged particles It is characterized by that.

  According to the atmospheric pressure ionization method of the present invention, a laser light source that generates laser light in the visible region is irradiated on the sample coaxially with the axial direction in which the laser light is irradiated with the excited particles or charged particles. Since a laser light source that generates a laser beam in the visible region is provided in the vicinity of the ion source, and the ionization point of the sample is discriminated based on the point where the laser beam emitted from the laser light source is hit, Thus, the ionization point of DART can be easily found and the sample can be aligned.

  The atmospheric pressure ion source according to the present invention is a laser light source that generates laser light in the visible region, and the laser light is irradiated on the sample coaxially with the irradiation axis direction on which the excitation particles or charged particles are irradiated. Since the laser light source arranged as described above is provided, the ionization point of the sample can be discriminated by the point where the laser beam irradiated from the laser light source is hit, and the ionization point of DART can be found visually. Thus, it is possible to provide an atmospheric pressure ion source capable of aligning the sample.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 4 shows an embodiment of an atmospheric pressure ion source according to the present invention. In FIG. 4, the same components as those in the conventional example of FIG.

  First, as omitted in FIG. 4, in the atmospheric pressure ion source (DART ion source) of the present invention, the installation rail, column, predetermined distance 14, height 15, An adjustment screw for setting the installation angle 13 is not an essential configuration. For example, the DART ion source 11 has a cylindrical shape with a diameter of about 8 cm and can be supported by the operator with one hand. The operator can adjust the distance between the sample and the excitation gas injection direction arbitrarily. Can be done.

  A laser light source 42 that generates a visible laser beam is attached to the DART ion source 11 on the side opposite to the injection nozzle 12. In order to introduce the laser beam into the DART ion source 11, a window 41 made of, for example, quartz glass is provided. As the laser light source 42, for example, a commercially available laser pointer can be used.

  If the mounting position of the laser light source 42 to the DART ion source 11 is described based on FIG. 5A illustrating the internal structure of the DART ion source 11, the laser light source 42 is adjacent to the second room 52. It is arranged outside the first room 51, and is provided on the straight line L on the opposite side to the second room 52.

  As described above, since the openings of the partition 56, the partition 57, and the outlet portion 58 are arranged on the straight line L passing through the central axis, the laser beam 33 emitted from the laser light source 42 is along the straight line L. It passes through each opening in the DART ion source 11 and is taken out together with the excitation gas flow ejected from the opening of the ejection nozzle 12.

  As shown in FIG. 5 (a), in order to avoid mutual interference between the needle electrode 55 and the laser beam 33, the needle electrode 55 of the present embodiment is located at a position where the base portion is deviated from the straight line L. The tip is arranged in the vicinity of the straight line L.

  Preferably, as shown in FIG. 5A, the angle θ formed by the needle electrode 55 and the partition 56 (the counter electrode when discharging from the needle electrode 55) is 0 ° ≦ θ ≦ 45 from the normal 90 ° state. By inclining so as to be in the range of °, it is avoided that the needle electrode 55 obstructs the laser beam.

  As another example, as shown in FIG. 5B, by disposing a plurality of needle electrodes 55 at almost equal intervals so as to surround a straight line L through which the laser beam passes, the needle electrode 55 is obstructed by the laser beam. May be avoided. In this way, if a plurality of needle electrodes 55 are arranged at equal intervals, the problem of bias in the discharge direction that occurs when one needle electrode is shifted laterally from the center as shown in FIG. Can be solved.

In the configuration as described above, the opening of the injection nozzle 12 is such that the laser beam 33 taken out together with the excitation gas flow ejected from the opening of the injection nozzle 12 travels along the ejection axis that is the center of the excitation gas flow. The direction in which the excited gas flow is ejected from is adjusted in advance. For this reason, when the excitation gas flow is directed to the sample, or when the sample 1 is arranged in the excitation gas flow, the laser beam is simultaneously projected onto the sample. The excitation gas flow reaches the sample around the projection spot, the sample is ionized, and the obtained sample ions are introduced into the ion inlet 23 on the atmospheric pressure interface 22 and subjected to mass analysis by the mass spectrometer 21.
Thus, the irradiation destination of the excitation gas of the DART ion source 11, that is, the ionization point, can be easily confirmed simply by visually confirming the spot 2 irradiated with the laser beam 33. As a result of confirmation, if the ionization point is not the desired position of the sample, the desired position can be adjusted to be the ionization point by moving the sample or changing the direction of the DART ion source 11 held by hand. .

Note that the measurer may hold both the DART ion source and the sample to be measured in hand. In that case, while the sample held in one hand is placed in front of the ion inlet 23, the direction of the DART ion source 11 held in the other hand and so that the spot 2 hits a desired position on the sample. Adjust the position. At this time, if the relative position between the sample and the DART ion source 11 is adjusted while confirming the mass spectrum obtained in real time, the excitation gas is applied to the desired position of the sample and ionized while arbitrarily selecting the angle and direction. be able to.
In addition, when a mechanism that supports either or both of the DART ion source and the sample is provided, the mutual positional relationship between the sample, the DART ion source, and the mass spectrometer orifice can be set with good reproducibility.
FIG. 6 shows another embodiment of the atmospheric pressure ion source according to the present invention. In the present embodiment, a window 41 for introducing the laser beam from the laser light source 42 is provided on the side wall portion of the third space 53, and further, the laser beam introduced into the space 53 from the window 41 is directed toward the outlet portion 58. A mirror 71 for reflection is provided on the straight line L. Since it is not necessary to arrange the laser light source 42 on the straight line L, the needle electrode 55 is arranged on the straight line L as in the conventional example of FIG. The window 41 and the mirror 71 may be provided in the second space 52.

  Also in this embodiment, it is possible to project the spot on the sample by advancing the laser beam coaxially with the ejection axis of the excitation gas flow ejected from the outlet 58 of the DART ion source. Although the mirror 71 is provided on the straight line L, since the excitation gas flows so as to avoid the mirror 71, the influence is minimal.

  In the above embodiment, a mirror is arranged on the straight line L so that the optical path of the laser beam 33 coincides with the straight line L. However, an optical fiber may be used instead of the mirror. For example, the laser beam is guided into the space 52 or 53 by an optical fiber, and the optical output end of the optical fiber is arranged on the straight line L, so that the laser beam travels on the same axis as the ejection axis of the excitation gas flow. Can project a spot.

  In the above embodiment, a DART ion source that generates excited molecules having no electric charge and ejects them as an excited gas flow is taken as an example. The present invention can also be applied to a barometric ion source.

  (1) In the inspection of defective parts such as industrial products and industrial materials, an abnormal part confirmed by visual inspection can be pinpointed and inspected by mass spectrometry.

  (2) When inspecting deposits adhering to an article, hold the article in front of the ion introduction hole as it is without pre-treatment, and apply an excitation gas to the deposit confirmed visually. It can be examined by mass spectrometry.

1: a sample substrate, 2: a portion hit by a laser beam, 3: a sample substrate,
4: sample spot for calibration, 10-1: mounting rail, 10-2: support column,
11: DART ion source, 12: excited gas ejection nozzle, 13: angle, 14: distance,
15: Height, 16: Adjustment screw, 17: Adjustment screw, 21: Mass spectrometer
22: Atmospheric pressure interface, 23: Ion introduction hole, 33: Laser beam,
42: Laser light source, 43: Helium gas inlet, 51: First chamber,
52: Second chamber, 53: Third chamber, 54: Gas introduction pipe, 55: Needle electrode,
56: partition, 57: partition, 58: outlet, 59: sample, 100: orifice

Claims (7)

In an atmospheric pressure ionization method of ionizing a sample by irradiating excited particles or charged particles generated by discharge or a high electric field under atmospheric pressure,
A laser light source that generates laser light in a visible region is arranged so that the laser light is irradiated on the sample coaxially with the axial direction on which the excitation particles or charged particles are irradiated,
An atmospheric pressure ionization method characterized in that the ionization point of the sample is discriminated based on a point where a laser beam irradiated from the laser light source is hit. An atmospheric pressure ion source that ionizes the sample by irradiating the sample with excited particles or charged particles generated by discharge or a high electric field under atmospheric pressure;
A laser light source that generates laser light in a visible region, the laser light being arranged so that the sample is irradiated coaxially with an irradiation axis direction irradiated with the excitation particles or charged particles;
An atmospheric pressure ion source. The atmospheric pressure ion source is:
A first space containing a needle electrode for exciting gas molecules by electric discharge;
A second space adjacent to the first space and containing charged particles and excited particles generated by the discharge flowing from the first space and removing charged particles from the excited gas;
A third space in which the excitation gas from which charged particles have been removed flows from the second space, and the excited excitation gas is heated;
A partition for partitioning the first space and the second space, wherein first and second excitation gas including charged particles and excited particles generated by the discharge are passed from the first space to the second space. A first partition with an opening,
A second partition provided with a second opening for partitioning the second space and the third space and allowing the excited gas from which the charged particles have been removed to pass from the second space to the third space. ,
A third opening for ejecting the excitation gas from the third space along the irradiation axis;
With
The first to third openings are provided on a straight line along the irradiation axis,
The tip of the needle electrode is arranged shifted from the straight line,
The laser light source is provided on the axis of the first space opposite to the second space, and laser light generated from the laser light source is transmitted through the first to third openings. The atmospheric pressure ion source according to claim 2, wherein the atmospheric pressure ion source is configured to travel along an irradiation axis. The atmospheric pressure ion source according to claim 3, wherein an angle θ formed by the needle electrode and the first partition is an angle of 0 ° ≦ θ ≦ 45 °. The atmospheric pressure ion source according to claim 3, wherein a plurality of the needle electrodes are arranged at substantially equal intervals around the first opening provided in the first partition. The atmospheric pressure ion source is:
A first space containing a needle electrode for exciting gas molecules by electric discharge;
A second space adjacent to the first space and containing charged particles and excited particles generated by the discharge flowing from the first space and removing charged particles from the excited gas;
A third space in which the excitation gas from which charged particles have been removed flows from the second space, and the excited excitation gas is heated;
A partition for partitioning the first space and the second space, wherein first and second excitation gas including charged particles and excited particles generated by the discharge are passed from the first space to the second space. A first partition with an opening,
A second partition provided with a second opening for partitioning the second space and the third space and allowing the excited gas from which the charged particles have been removed to pass from the second space to the third space. ,
A third opening for ejecting the excitation gas from the third space along the irradiation axis;
With
The first to third openings are provided on a straight line along the irradiation axis,
Optical means for directing laser light generated by the laser light source in the second space or the third space to travel along the irradiation axis through the third opening is provided. The atmospheric pressure ion source according to claim 2. The atmospheric pressure ion source according to claim 6, wherein the optical means is a mirror or an optical fiber.

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