JP2014222190A - Specimen solution mass spectrometry, and device for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a specimen solution mass spectrometry that enables an analysis in real time as performing a consecutive injection of a specimen solution to a vacuum chamber, without requiring a frit.SOLUTION: An analysis method of irradiating a specimen introduced inside a vacuum chamber with laser beam, ionizing the specimen, and thereby performing mass spectrometry is configured to: prepare a solution introduction pipe that supplies a specimen solution from a storage part of the specimen solution including a specimen to the vacuum chamber, and pulse injection means that performs a pulse injection of the specimen from a tip end of the solution introduction pipe to the vacuum chamber; and inject the specimen solution from the tip end of the solution introduction pipe to the vacuum chamber by the pulse injection means in a pulse-like state, irradiate the specimen solution introduced to the vacuum chamber in the pulse-like state with the laser beam, and generate a specimen ion.

Description

The present invention relates to a mass spectrometry method and apparatus for generating sample ions by irradiating a sample introduced into a vacuum chamber with laser light, and in particular, a sample solution such as an aqueous solution containing a sample can be subjected to mass analysis by a simple method. It relates to a possible method and apparatus.

This type of mass spectrometry is based on laser ionization time-of-flight mass spectrometry (LI / TOFMS), which detects and measures sample ions by size based on the relationship between charge and mass of sample ions. Is well known). This analysis method is widely used for environmental analysis and spectroscopic analysis because it enables real-time and highly selective analysis of aromatic compounds using an ultraviolet laser as a light source.
However, the measurement target of the LI / TOFMS method is generally a gas sample, and a solid sample or a liquid sample has to be vaporized using heating or laser light.
For example, for 2,4-xylenol and its isomers, solid phase extraction was performed on water samples in which they were dissolved, and after elution with acetonitrile, dehydrated with anhydrous sodium sulfate to obtain a measurement sample, This solution is injected into a gas chromatograph, and the vaporized sample is introduced into a laser ionization time-of-flight mass spectrometer for analysis.
As described above, in order to perform solid or liquid sample analysis by the LI / TOFMS method, a complicated and time-consuming pretreatment is required.

  Therefore, the solvent is evaporated from the sample solution using a frit, and the remaining solid sample is vaporized by irradiating it with laser light (see, for example, Patent Document 1).

JP 2003-35699 A

However, it is difficult to design and manufacture an optimum frit for each type of sample to be analyzed. On the other hand, real-time analysis of sample solutions is required.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a mass analysis method and apparatus for a sample solution that does not require a frit and can be analyzed in real time while continuously introducing the sample solution into a vacuum chamber. To do.

In order to solve the above problems, the inventors of the present invention conducted experiments by removing the frit from the tip of the solution introduction tube (column). When the frit is removed, the sample solution is continuously introduced from the solution introduction tube into the vacuum chamber, and the vacuum degree of the vacuum chamber decreases.However, adjusting the inner diameter of the solution introduction tube may hinder the analysis of the vacuum degree of the vacuum chamber. Can be kept at no level.
In the case of a highly volatile sample solution, it is possible to ionize the sample by irradiating a laser beam with the sample solution jumping out into the vacuum chamber without frit, but the efficiency is very poor. Further, it was found that in the case of a sample solution with low volatility, the sample solution is solidified at the tip of the solution introduction tube and is difficult to introduce into the vacuum chamber.
Therefore, as a result of intensive studies by the inventors of the present invention, by heating the sample solution in a pulse form at the tip of the solution introduction tube, the vaporized sample solution is introduced into the vacuum chamber in a pulse form and has high volatility. In the case of the sample solution, it was found that the analysis efficiency is high, and in the case of the sample solution with low volatility, the sample solution can be injected into the vacuum chamber without solidifying.

Specifically, the present invention relates to an analysis method in which mass analysis is performed by irradiating a sample introduced into a vacuum chamber with a laser beam and ionizing the sample solution, and the sample solution is supplied from the storage portion of the sample solution containing the sample to the vacuum chamber. And a sample solution pulse injection means for pulse-injecting the sample solution from the tip of the solution introduction tube to the vacuum chamber, and the vacuum injection from the tip of the solution introduction tube by the pulse injection means In this method, the sample solution is ejected into the chamber in a pulsed manner, and the sample solution introduced in a pulsed manner into the vacuum chamber is irradiated with laser light to generate sample ions.
As the pulse injection means, for example, a heater or a pulse laser irradiation device that intermittently heats the sample solution at the tip of the solution introduction tube can be used.
A gas introduction tube may be provided outside the solution introduction tube, and the gas introduced from the gas introduction tube may suppress the solidification of the sample solution at the tip of the solution introduction tube.
In this case, the tip of the solution introduction tube may be positioned inside or outside the tip of the outer tube with a size smaller than 3 mm.

  According to the method and apparatus of the present invention, a frit for evaporating the solvent from the sample solution and introducing the sample molecules into the vacuum chamber becomes unnecessary, and laser irradiation is performed while continuously introducing the sample solution into the vacuum chamber. Therefore, the sample solution can be analyzed easily and in real time.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram for explaining the configuration of an analyzer according to an embodiment of the present invention, and FIG. 2 is a schematic diagram for explaining the configuration of another embodiment of the analyzer of the present invention.
The analyzer 1 of the embodiment of FIG. 1 includes a vacuum chamber 11 that is kept in a vacuum state by a vacuum pump P, a solution introduction pipe 12 that introduces a sample solution into the vacuum chamber 11, and a vacuum chamber 11 that extends from the solution introduction pipe 12. The sample solution introduced into the ion beam is irradiated with an ionization laser beam 16 to be ionized, and the sample solution at the tip of the solution introduction tube 12 is irradiated with an injection pulse laser beam 18 to pulse the sample solution. An injection pulse laser irradiation unit 17 for injecting into the vacuum chamber 11 in a shape, an introduction window 28 for introducing the injection pulse laser beam 18 irradiated from the injection pulse laser irradiation unit 17 into the vacuum chamber 11 were generated. And a time-of-flight mass analyzer 15 for analyzing ions.

  The time-of-flight mass analyzer 15 includes a detector 20 such as a microchannel plate detector and an oscilloscope 21 that processes a signal from the detector 20. In FIG. 1, reference numerals 22 to 24 are electrodes, 25 is a mirror, and 27 is an introduction window for introducing the ionized laser light 16 into the vacuum chamber 11.

  In the analyzer 1, the sample solution is irradiated with the pulse laser beam 18 for injection at the tip of the solution introduction tube 12 to evaporate the solvent, and the sample molecules are introduced into the vacuum chamber 11 from the tip of the solution introduction tube 12. In order to irradiate the introduced sample molecules with the ionized laser light 16, the irradiation timing of the emission pulse laser light 18 and the irradiation timing of the ionized laser light 16 are shifted using a delay device (not shown).

FIG. 2 is an enlarged view of the distal end portion of the solution introduction tube 12 according to another embodiment of the analyzer of the present invention.
In this embodiment, an outer tube 13 is provided outside the solution introduction tube 12, and outside air is introduced into a gap between the solution introduction tube 12 and the outer tube 13. The tip of the solution introduction tube 12 is positioned slightly inside or outside the tip of the outer tube 13. The distance S between the distal end of the outer tube 13 and the distal end of the solution introduction tube 12 is preferably about −3 mm <S <3 mm with the distal end of the outer tube 13 as a reference (S = 0), and −1 mm ≦ S ≦ It is preferably about 1 mm.
When the sample solution is introduced into the vacuum chamber 11 from the tip of the solution introduction tube 12, it is rapidly cooled by the heat of vaporization and is easily solidified at the tip of the solution introduction tube 12. Can be prevented from coagulating. In particular, such a double tube structure is effective for analysis of a sample solution having low volatility and easily coagulating like an emulsion.

FIG. 3 is a graph for explaining the irradiation timing of the ejection pulse laser beam 18 and the ionized laser beam 16. In this graph, the horizontal axis represents the delay time of the irradiation timing of the ionized laser beam 16 with respect to the irradiation timing of the emission pulse laser beam 18. The vertical axis represents the molecular ion peak area of 2,4-xylenol, which is a sample. The energy of the injection pulse laser irradiation unit 17 was 1 mJ.
From the graph of FIG. 3, it can be seen that the sample molecules are introduced into the vacuum chamber 11 in a pulsed manner by the irradiation of the pulsed laser beam 18 for injection.
In addition, the graph of FIG. 3 has a peak when the delay time is 8 μsec, so that it can be seen that the delay time of both lasers may be 8 μsec.
If the distance between the tip of the solution introduction tube 12 and the ionized laser beam 16 is 2 mm, the sample molecule speed can be determined to be about 250 m / s from the delay time of 8 μsec.

The solution introduction tube 12 is not particularly limited as long as it can supply the sample solution from the sample solution storage section S into the vacuum chamber 11. However, the solution introduction tube 12 is formed of a non-dielectric material such as quartz and causes adhesion of organic molecules. A difficult capillary is preferred.
In the analyzer 1 of the present invention, heating the tip of the solution introduction tube 12 by irradiation with the pulsed laser beam 18 for injection causes a reduction in the vacuum degree of the vacuum chamber 11.

Therefore, the inner diameter of the solution introduction tube 12 was changed in various ways, and the pressure was measured while continuously introducing water into the vacuum chamber 11 instead of the sample solution. The ultimate vacuum of the vacuum chamber 11 by the pump P was 1.0 × 10 ⁻³ Pa. When the tip portion of the solution introduction tube 12 having an inner diameter of 50 μm was heated at 100 ° C., the degree of vacuum decreased to 1.0 × 10 ⁻² Pa, which hindered the analysis. However, when the inner diameter was 20 μm, the degree of vacuum was maintained at 3.4 × 10 ⁻³ Pa even at a heating temperature of 100 ° C., which was a level that did not hinder the analysis.
From the above, it can be seen that the vacuum degree of the vacuum chamber 11 can be adjusted by the inner diameter of the solution introduction tube 12. Further, although different depending on the type of solvent, in the sample solution mainly composed of water, 20 μm is one guide for the inner diameter of the solution introduction tube 12.

Next, the relationship between the energy of the emission pulse laser beam 18 and the degree of vacuum in the analyzer 1 will be described with reference to FIG.
As shown in FIG. 4, the peak area increases as the energy of the pulse laser beam 18 for emission increases, and it can be seen that more solution is vaporized. On the other hand, when the energy of the pulse laser beam 18 for injection exceeds a certain value (in the example of FIG. 4, 1 mJ when the solution introduction tube 12 having an inner diameter of 100 μm is used), the degree of vacuum in the vacuum chamber 11 changes. In the illustrated example, the degree of vacuum suddenly decreased when it exceeded 1.5 mJ. From this, it can be seen that the variation in the degree of vacuum is closely related to the inner diameter of the solution introduction tube 12 and the energy of the pulse laser beam 18 for injection. And when using the pulsed laser beam 18 for injection, 1 mJ becomes one standard as the energy.

It is preferable that the tip of the solution introduction tube 12 and the ionized laser beam 16 be as close as possible to increase ionization efficiency.
As the ionization laser irradiation unit 14, an appropriate one is selected according to the type of the sample. For example, an ultraviolet pulse laser may be used for a sample having a property of absorbing photons in the ultraviolet region.
The injection pulse laser irradiation unit 17 may be of any type as long as it can inject the sample solution into the vacuum chamber 11 by irradiating the sample solution at the tip of the solution introducing tube 12 with the injection pulse laser beam 18. Although the same thing as the ionization laser irradiation part 14 can also be used, it is necessary to adjust the wavelength etc. for using for injection | emission.

The operation of the analyzer 1 having the above configuration will be described.
In the analyzer 1 of FIG. 1, first, a sample solution to be analyzed is collected, and impurities are filtered using a filter paper or the like. Unnecessary impurities can be removed by repeating the filtration a plurality of times as necessary or using a solid phase extraction cartridge. The sample solution thus obtained is held in the cylinder S or the like by an amount necessary for analysis.
The solution introduction tube 12 is inserted into the cylinder S and supplied to the vacuum chamber 11 due to a pressure difference with the vacuum chamber 11. At this time, the sample solution at the tip of the solution introduction tube 12 is irradiated with the pulsed laser light 18 for injection to evaporate the solvent, and the sample molecules are introduced into the vacuum chamber 11 from the tip of the solution introduction tube 12.
In the vacuum chamber 11, the sample solution introduced from the solution introduction tube 12 is ionized by irradiating the ionized laser beam 16. The sample ions accelerated by the electrodes 23 and 24 are introduced into the mass analyzer 15 and collide with the detector 20. The oscilloscope 21 outputs the difference in time for the sample ions to reach the detector 20 as an analysis result.

[Example]
Hereinafter, specific examples using the analyzing apparatus having the above configuration will be described.
[Example 1]
Capillary column: GL Sciences, length 40 cm, inner diameter 20 μm
Ionized laser irradiation unit: manufactured by Rayture Systems, GAIA
II Nd: YAG laser (wavelength 266 nm, pulse width 5 ns, frequency 10 Hz)
Pulse laser irradiation unit for injection: Continuum, Minilite II Nd: YAG laser (wavelength 532 nm, pulse width 5 ns, frequency 10 Hz)
Distance between the tip of the solution introduction tube 12 and the ionized laser beam 16: 2 mm
Adjustment of irradiation timing of two laser beams: Stanford Research Systems, DG 535 delay / pulse generator Vacuum reach of vacuum chamber: 1.0 × 10 ⁻³ Pa
Sample solution: 2,4-xylenol aqueous solution (1 ng / μl)
In Example 1, the time difference between the irradiation timings of the two laser beams was set to 0, so that the analysis was performed without substantially irradiating the emission pulse laser beam 18. The result is shown in the graph of FIG.
From the mass spectrum of FIG. 5 (a), a molecular ion peak of 2,4-xylenol and several fragment ion peaks can be observed. This is considered to be because 2,4-xylenol was vaporized and ionized because 2,4-xylenol was highly volatile. That is, it can be seen that a sample having high volatility such as 2,4-xylenol can introduce the sample solution into the vacuum chamber 11 without irradiation with the pulse laser beam 18 for injection.

[Example 2]
Example 2 is the same as Example 1 except that the time difference between the irradiation timings of the two laser beams is 8 μsec. The result is shown in the graph of FIG. In Example 2, the tip of the solution introduction tube 12 is irradiated with an injection pulse laser, whereby the solvent water evaporates and 2,4-xylenol molecules are introduced into the vacuum chamber 11 in a pulsed manner.
From the graph of FIG. 5B, it can be seen that the signal intensity is increased by about 1.5 times the molecular ion peak of FIG. Thus, it can be said that the improvement in sensitivity can be expected by irradiating the pulsed laser beam 18 for injection, and it can be said that it is suitable for microanalysis.
In addition to optimization of various experimental conditions, this multiplication factor is considered to be larger for molecules with lower volatility. That is, a sample solution with low volatility is easily solidified at the tip of the solution introduction tube 12, and it is difficult to introduce the sample solution into the vacuum chamber 11 as it is, but the sample is irradiated by irradiating the pulsed laser beam 18 for injection. It becomes possible to inject the solution into the vacuum chamber 11 in a pulse shape.

Although a preferred embodiment of the present invention has been described, the present invention is not limited to the above description.
For example, in the above description, the sample solution is ejected from the tip of the solution introduction tube 12 by irradiating the pulsed laser irradiation light 18, but if the sample solution can be ejected in a pulsed manner, it is intermittent. A heater that can heat the tip of the solution introduction tube 12 may be used. Further, in another embodiment shown in FIG. 2, the gas passed through the gap between the solution introduction tube 12 and the outer tube 13 is not limited to the outside air, and other gases (nitrogen and nitrogen) can be used as long as they do not hinder the analysis. Other inert gases etc. can be used.

  The method and apparatus of the present invention are suitable for directly analyzing a sample solution in real time, and can be widely applied to analysis of water quality of rivers, lakes and the like, as well as analysis of factory drainage and soil contamination. .

It is the schematic concerning one Embodiment of the analyzer of this invention, and explaining the structure. It is the schematic which concerns on other embodiment of the analyzer of this invention, and demonstrates the structure. It is a graph explaining the irradiation timing of the pulsed laser beam for injection and the ionized laser beam. It is a graph which shows the relationship between the energy of the pulse laser beam for injection | emission, and a signal output. According to the embodiment of the present invention, (a) is a mass spectrum when irradiation with pulsed laser light for injection is not performed, and (b) is a mass spectrum when irradiated with pulsed laser light for injection.

DESCRIPTION OF SYMBOLS 1 Analyzer 11 Vacuum chamber 12 Solution introduction tube 13 Outer tube 14 Ionization laser irradiation part 15 Mass analyzer 16 Ionization laser light 17 Ejection pulse laser irradiation part 18 Ejection pulse laser light 20 Photodetector 21 Oscilloscope 22, 23, 24 Electrode 25 Mirror 27, 28 Introduction window

Claims (9)

In an analysis method that performs mass spectrometry by irradiating a sample introduced into a vacuum chamber with laser light and ionizing it,
A solution introduction tube for supplying a sample solution from a storage portion of a sample solution containing a sample to the vacuum chamber and a sample solution pulse injection means for pulse-injecting the sample solution from the tip of the solution introduction tube to the vacuum chamber are prepared. And
By the pulse ejection means, the sample solution is ejected in a pulse form from the tip of the solution introduction tube to the vacuum chamber,
Irradiating the sample solution pulsed into the vacuum chamber with laser light to generate sample ions;
A method for mass spectrometry of a sample solution characterized by the above. 2. The pulse injection means is a heater that intermittently heats the sample solution at the tip of the solution introduction tube, and the sample solution is injected into the vacuum chamber in pulses by intermittent heating by the heater. A method for mass spectrometry of the sample solution according to 1. The pulse injection means is a pulse laser irradiation apparatus, and the sample solution is introduced into the vacuum chamber in a pulse shape by irradiating the sample solution at the tip of the solution introduction tube with pulse laser light. Item 2. A method for mass spectrometry of a sample solution according to Item 1. The gas introduction pipe is provided outside the solution introduction pipe, and solidification of the sample solution at the tip of the solution introduction pipe is suppressed by the gas introduced from the gas introduction pipe. A method for mass spectrometry of the sample solution according to claim 1. In an analyzer that performs mass spectrometry by ionizing a sample introduced into a vacuum chamber by irradiating it with laser light,
A solution introduction tube for supplying a solution from a reservoir of a sample solution containing a sample to the vacuum chamber;
A sample solution pulse injection means for pulse-injecting the sample solution from the tip of the solution introduction tube to the vacuum chamber;
Laser irradiation means for generating sample ions by irradiating the sample solution pulsed into the vacuum chamber with laser light;
An apparatus for mass analysis of a sample solution, comprising: 6. The sample solution mass spectrometer according to claim 5, wherein the pulse injection means is a heater that intermittently heats the sample solution at the tip of the solution introduction tube. 6. The sample solution mass spectrometer according to claim 5, wherein the pulse injection means is a pulse laser irradiation device. The sample solution mass spectrometer according to any one of claims 5 to 7, wherein a gas introduction tube is provided outside the solution introduction tube. 9. The mass spectrometer of sample solution according to claim 8, wherein the tip of the solution introduction tube has a dimension smaller than 3 mm and is located inside or outside of the tip of the outer tube.

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