WO2007129495A1 - Method of droplet ionization, mass spectrometry and apparatus therefor - Google Patents

Abstract

It is intended to irradiate a sample with laser to thereby attain immediate ionization of the sample and guide the ionized sample to a mass spectrograph so as to carry out identification of the sample by means of simple apparatus. It has been ascertained that when a falling droplet at the center thereof is irradiated with laser beams, the droplet undergoes instantaneous vaporization and is simultaneously ionized. Accordingly, there is provided accurately irradiating of a droplet sample at its position of fall with laser beams to thereby simultaneously attain vaporization and ionization of the droplet sample.

Description

 Droplet ionization method, mass spectrometry method and apparatus thereof

 Technical field

 [0001] The present invention relates to mass spectrometry of a substance, and more particularly, to an ion ion of a sample prior to mass spectrometry.

 Background art

 [0002] Koichi Tanaka invented the Matrix Assisted Laser Desorption / Ionization Method (MALDI), which is effective for soft ion mass spectrometry of macromolecules, and received the Nobel Prize. However, this MALDI cannot avoid the generation of fragments for environmental samples with many contaminants, and should be a sufficient method.

 [0003] The electrospray ionization method (ESI) and the atmospheric pressure ionization method (APCI) can be applied to a relatively large number of target samples. However, in environmental samples, contaminants become obstacles and their applications are limited. ing. In 1984, Fujii of the National Institute for Environmental Studies developed a mass spectrometry method for the deposition of lithium ions in the gas phase with the primary purpose of detecting gas phase radicals, and in 2000, commercialized an ion attachment mass spectrometer (IAMS). Have been!

 [0004] Elucidating the risks and dynamics of these chemical substances such as “I want to prove that there are no harmful substances going back in the past” and “I measured all chemical substances in the environment as they were” This research is an important research subject in advanced environmental science with a view to analyzing environmental infomatics.

 [0005] The importance of comprehensive testing for the search for harmful substances present in the environment has been pointed out by environmental administrative research institutions, and the abundance is assessed by chemical substance units. Improving the law · The concept of comprehensive evaluation and database creation by screening, bio-assessment has been recently started.

[0006] Suspended particulate matter (SPM) in the atmosphere, which is attracting international attention for human effects, is widely distributed in particle diameters ranging from several tens / zm force to several nm. Among them, nanoparticles with a particle size of less than 0.1 μm may be taken into the body directly by lungs due to respiration. [0007] In the current SPM composition analysis, it is difficult to detect all constituent molecules of fine particles as they are, and multi-component simultaneous measurement is desired. As for suspended particles, there is a problem in the force pretreatment that has reached the level where it is possible to measure one particle in the US and Europe, and only the main components can be identified, and simple inorganic components can be identified. Organic arsenic compounds are a recent representative example of environmental substances that are difficult to perform mass spectrometry.

 [0008] Soft ionic technology such as MALDI and ESI has been highly evaluated for its practicality in the advanced biotechnology field. MALDI was performed under atmospheric pressure, and sugar chain compounds in breast milk were detected as lithium adducts, indicating that they can be applied to biochemical 'medicine' pharmacy.

 [0009] JEOL developed a Direct Analysis in Real Time (DART) ion source and won a gold medal at the 2005 Pittsburgh Conference for its in situ detection of low molecular weight volatile sample materials For example, soft ion studies related to mass spectrometers have made significant progress worldwide.

[0010] By the way, environmental substances are forces that exist in the environment in various forms such as gas 'floating particles' droplets containing solids. Ion has been carried out by dropping the solution onto the substrate and irradiating it with laser light.

 [0011] However, when laser light is applied to the droplets on the substrate, the incident laser light is applied not only to the sample but also to the substrate, so it is possible to determine how the laser energy is absorbed by the sample. I couldn't have a debate.

 [0012] At this time, while the droplet is falling, it is evaporated by irradiating the droplet with infrared laser light, and the vaporized gaseous molecules are introduced under a high vacuum to perform multiphoton ionization and mass spectrometry. Technology has been developed (see Non-Patent Document 1 below).

[0013] However, in this method, the laser beam is irradiated on the droplet only for evaporation, and ionic liquid has a drawback in that a separate device is required. It was.

Non-Patent Document 1: 1P030, Development of a droplet laser evaporation mass spectrometer (Kampon Lab., Ltd. 1, Toyoda Inst. jp / "bkinfo I 2004 /proglp.html) Disclosure of the invention

 Problems to be solved by the invention

 [0014] An object of the present invention is to immediately ionize a sample by irradiating the sample with a laser, guide the ionized sample to a mass spectrometer, and achieve sample identification with a simpler apparatus. .

 Means for solving the problem

[0015] It was confirmed that when a laser beam was applied to the center of a falling droplet, the droplet evaporated instantaneously and ionized. When the laser beam deviates from the central force of the droplet, the energy from the laser is not sufficiently absorbed by the droplet, and it was confirmed that evaporation was insufficient and ionization was insufficient.

In the present invention, the liquid droplet sample is evaporated and ionized by accurately irradiating a laser beam to the drop position of the liquid droplet sample.

 The invention's effect

 [0017] In the present invention, since the droplet sample can be directly ionized by laser light, the apparatus shown in Non-Patent Document 1 requires a necessary ionization apparatus. Therefore, it is possible to obtain a mass spectrometer that is simpler and cheaper than the above apparatus.

 Brief Description of Drawings

[0018] FIG. 1 is a schematic diagram of an apparatus according to the present invention.

 [FIG. 2] State change diagram of a droplet by laser irradiation according to the method of the present invention

 [Figure 3] (A) Output diagram when the laser beam is sufficiently absorbed by the droplet (B) Output diagram when the laser beam is sufficiently absorbed by the droplet

 BEST MODE FOR CARRYING OUT THE INVENTION

[0019] The best mode for carrying out the present invention will be described below.

[0020] An overview of the apparatus will be described.

As shown in FIG. 1, the analyzer is roughly divided into three parts: an ionization part 1, an ion guide part 2, and a time-of-flight measurement part (TOF) 3. In the ionizer section 1, the droplet 5 is introduced from the droplet introduction device 4. As a droplet supply method, a method of dropping the supply nozzle force and a method of pushing upward from the nozzle can be considered.

 As the droplet sample, a solution in which the sample and lithium are dissolved in a solvent is used. The droplet introduction device is an off-the-shelf microdrop generator that generates droplets with a diameter of 70 m.

 [0022] This droplet is irradiated with a laser beam. The laser may be a long panoreth laser with a panorace width longer than that of a 355 nm wavelength Nd-YAG laser or YAG laser.

 [0023] FIG. 2 shows the state change of the droplet when the droplet is irradiated with the YAG laser light.

 At 0 ns, before the laser beam irradiation, at 10 ns, the laser beam was emitted from the left side of the photo. After 20 ns, a picture of the process of droplet explosion and evaporation is shown. When the droplet is irradiated with laser light, the droplet force S ion is generated and light is emitted.

 [0024] Figure 3 compares the TOF signal when the acetone solution is used as the sample and the laser beam is proved to be effective, and the case where the laser beam is not effectively applied to the droplet. The

 Fig. 3 (A) shows the signal waveform when effective irradiation is performed, and Fig. 3 (B) shows the signal waveform when irradiation is not effective. The signal intensity is proportional to the total number of ions detected.

 [0025] As described above, when the laser beam collides with the center of the sample, most of the sample is ionized, and it is possible to obtain data with a very large SZN ratio by conducting this to the TOF section and performing mass spectrometry. Was confirmed. On the other hand, when the laser beam collided off the center of the sample, it was confirmed that the SZN was small.

 Therefore, mass analysis with a large SZN ratio can be performed by irradiating the center of the droplet with laser light.

 [0026] The timing of irradiating the droplets with the laser light can be determined by experiment in consideration of the droplet ejection conditions from the droplet supply device and the laser irradiation conditions.

Claims

The scope of the claims  [1] A liquid sample ionization method characterized by ionizing a liquid sample by irradiating the liquid droplet with a laser beam by irradiating the liquid droplet with the sample.  [2] The method for ionizing a liquid sample according to [1], wherein lithium is added to the liquid sample.  [3] The method for ionizing a liquid sample according to [1], wherein the droplet is dropped from above and the laser beam is irradiated during the dropping. [4] The method of ionizing a liquid sample according to [1], wherein the laser beam is irradiated in a state where the droplet is supported on a tip of a nozzle whose tip is directed upward. [5] The method for ionizing a liquid sample according to [1], wherein the laser is a YAG laser or a long pulse laser. [6] A mass spectrometry method, characterized in that a sample ionized by the ionization method of a liquid sample according to claim 1 is guided to a mass spectrometer and the sample is identified. [7] An ionization device for a liquid sample, a droplet supply device for supplying the sample as droplets, evaporating the droplets by irradiating the droplets supplied from the device with laser light, and An ionization apparatus for a liquid sample, comprising: a laser light source that is turned on;  [8] A mass spectrometer, wherein the sample ionized from the liquid sample ionizer according to claim 7 is guided to a mass analyzer, and the sample is identified.