JP2007327910A - Matrix compound for mass analysis, substrate for mass analysis and mass analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a matrix compound for mass analysis which performs the detection of a high-molecular weight compound due to dissociation/ionization with high sensitivity and can avoid fragmentation to the utmost so as not to substantially cause trouble in the analysis of a low-molecular region. <P>SOLUTION: The matrix compound for mass analysis has properties for dissociating/ionizing a measuring target molecule by main decomposition products decomposed into compounds with a mass number of below 160 by an irradiating laser beam. A mass analyzer using the matrix compound for mass analysis is also disclosed. Alternatively, in a substrate for mass analysis, a microporous film or a mesoporous film is provided on the surface of a metal or semiconductor substrate, the matrix compound is carried by micropores or mesopores and only the compounds with a mass number of below 160 are selectively produced outside pores by the irradiating laser beam. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention provides high-accuracy mass spectrometry that can efficiently desorb / ionize high-molecular-weight measurement target molecules for mass spectrometry and that has few complex peaks due to decomposition products even in a low molecular weight region. The present invention relates to a mass spectrometric matrix compound, a mass spectrometric substrate, and a mass spectroscope using the mass spectrometric matrix compound, which can be easily performed by the method.

  The mass spectrometer ionizes the molecule to be measured by some method, applies an electric field or magnetic field to the molecule, separates it according to the mass / charge number (m / z), and then determines the measurement target from the electrically detected mass spectrum. Qualitative analysis and quantitative analysis can be performed. In this case, ionization methods include electron spray ionization (ESI), electron impact ionization (EI), chemical ionization (CI), fast atom bombardment (FAB), field desorption (FD), and laser desorption ionization (LDI). There are various methods such as matrix-assisted laser desorption ionization (MALDI). For example, in a laser ionization mass spectrometer, a sample can be irradiated with a pulsed laser beam to be ionized, and the mass spectrum or the like can be measured by introducing the ions to an analysis unit such as a time-of-flight type.

  Conventionally, in a laser ionization mass spectrometer such as the LDI method, a sample solution in which a measurement target compound is dissolved in water or an organic solvent is first prepared, and this sample solution is applied to a smooth surface of a metal holder and dried. When a sample is formed into a thin film and the sample thin film is irradiated with laser light, the laser light is absorbed by the metal sample support substrate, and a rapid temperature rise occurs at the irradiated location, causing ionization of the sample.

  However, in this sample preparation method, in addition to desorption / ionization of the molecule to be measured by laser light irradiation, a decomposition reaction (hereinafter also referred to as fragmentation) occurs simultaneously, and the mass spectrum of the molecule to be measured can be obtained with sufficient intensity. Or the peak of the decomposed product itself is detected, so that the mass spectrum becomes complicated and the analysis becomes difficult.

  Therefore, as a solution to this problem, a mixture of a highly viscous and low vapor pressure liquid such as glycerin and metal fine particles (for example, Patent Document 1), 2,5-dihydroxybenzoic acid (DHB), In the MALDI method using solid organic molecules (for example, Patent Documents 2 and 3) such as synaptic acid and α-cyano-hydroxy-cinnamic acid (CHCA) as a matrix, the matrix itself uses the energy of the irradiation laser light. Absorption and desorption / ionization occur, and the influence of irradiation laser light on the measurement target molecule itself contained in the matrix is reduced, so that fragmentation of the measurement target molecule is suppressed and detection can be performed with high sensitivity. It has become possible. The progress of this MALDI method makes it possible to measure even a very small amount of a high molecular weight measurement target compound that could not be handled by conventional mass spectrometry, and it is widely used for analysis of biomaterials and synthetic polymers. It became so.

  However, even with this MALDI method, the degradation product of the molecule to be measured can be considerably suppressed, but many peaks derived from complex reactions caused by the matrix itself absorbing the laser light are detected. Spectral analysis in the molecular weight range is often difficult. In particular, in the field of proteomics and metabolomics in recent years, there is an increasing need to comprehensively analyze not only single molecular species but also compounds contained in blood, body fluids, and the like. In the case of this exhaustive analysis, analysis of relatively low molecular weight compounds having a mass number of about several hundreds such as substrates and metabolites will also provide important information, but the conventional MALDI method provides complex information derived from the matrix. Due to the peak, the problem that this low molecular weight region cannot be analyzed with high accuracy is highlighted. Also in the field of synthetic polymer materials, it is very common to include additives having a molecular weight of several hundreds, such as antioxidants, ultraviolet absorbers, and plasticizers, in molded articles of polymer materials. In addition, there is a need to analyze a high molecular weight material and a low molecular weight compound in a lump, and the complex peak derived from the matrix in the MALDI method is an obstacle to the analysis as in the comprehensive analysis in the biochemistry described above.

  Furthermore, when a high molecular weight compound is analyzed by the MALDI method, it may be possible to positively cause fragmentation of the measurement target compound by changing measurement conditions such as the intensity of irradiation laser light. By analyzing the generated fragment ions, it is possible not only to analyze the molecular weight but also to obtain information on the molecular structure of the measurement target compound such as substituents and side chain structures. However, when there are a large number of complex peaks derived from the matrix, it also becomes a major obstacle in the analysis of the fragment ions from the above-mentioned measurement target compound.

As a technology that enables mass spectrometry in such a low molecular weight region at the same time, a molecule to be measured is directly placed on a sample support substrate having a fine porous structure on the surface of a porous silicon substrate or the like formed by electrolytic etching. A method of desorbing and ionizing a molecule to be measured without causing a complex peak derived from a matrix by irradiating a laser beam after adhering: SALDI (surface assisted laser desorption ionization) method has been proposed. (For example, patent document 4). This method makes it possible to achieve both efficient desorption, ionization, and suppression of decomposition product generation during laser irradiation, but the upper limit of the molecular weight of the measurement target compound is about several thousand, and more compounds Is said to be difficult to desorb or ionize.
JP-A-62-43562 JP-A-10-182704 JP 2005-326391 A US Pat. No. 6,288,390

  As described above, in the technique of desorption by laser light irradiation and mass spectrometry based on ionization, it is difficult to detect from a low molecular weight range to a high molecular weight range in a collective manner. There are issues that cannot be done.

  Accordingly, the object of the present invention is to detect a high molecular weight compound by desorption / ionization with high sensitivity and to analyze a substantially low molecular region in the technique of desorption and ionization mass spectrometry by laser light irradiation. It is an object to provide a matrix compound for mass spectrometry and a substrate for mass spectrometry that enable fragmentation to be avoided as much as possible without causing trouble.

  Another object of the present invention is to provide a mass spectrometer using the matrix compound for mass spectrometry.

  According to the present invention, a matrix compound for mass spectrometry is characterized in that, in a matrix compound for mass spectrometry, a molecule to be measured is desorbed and ionized by a main decomposition product decomposed into a compound having a mass number of less than 160 by irradiation laser light. Is provided.

  Further, according to the present invention, in the substrate for mass spectrometry, a microporous film or mesoporous film is provided on the surface of a metal or semiconductor substrate, and a matrix compound is further supported in the micropore or mesopore, and the mass is irradiated by irradiation laser light. There is provided a substrate for mass spectrometry, wherein only a compound having a number of less than 160 is selectively generated outside the pores.

  Furthermore, according to this invention, the mass spectrometer using the said matrix compound for mass spectrometry is provided.

  According to the present invention, a MALDI-type mass spectrometer, particularly a MALDI-IT (matrix-assisted laser desorption / ionization-ion trap) type, MALDI-IT-TOF (matrix-assisted laser desorption / ionization-ion trap-time of flight) type, In a MALDI-FTICR (Matrix Assisted Laser Desorption / Ionization-Fourier Transform Ion Cyclotron Resonance) type mass spectrometer, it is possible to obtain a mass spectrum with high sensitivity and a small signal derived from impurities in a wide molecular weight range.

  The method of the present invention is a method for measuring the mass number of a substance to be measured using a mass spectrometer having a MALDI (Matrix Assisted Laser Desorption / Ionization) ion source. Here, at present, the mechanism of desorption, ionization, and fragmentation in the MALDI method is not completely elucidated. In the present specification, the present invention will be described on the basis of the interpretation of the currently most accepted mechanism.

  The general measurement by MALDI method is explained. Solid organic molecules such as nitroanthracene (9NA), 2,5-dihydroxybenzoic acid (DHB), synaptic acid, α-cyano-hydroxy-cinnamic acid (CHCA) are used as matrix molecules, and measurement is performed in the matrix. A mixed crystal containing a trace amount of the target molecule is formed on the sample support substrate for analysis. At this time, it is preferable that the measurement target molecule is in a dilute state and has no interaction between the measurement target molecules. Next, this mixed crystal is irradiated with laser light, and the matrix molecules that have absorbed the laser light are vaporized by electronic excitation and / or vibration excitation. The vaporization of matrix molecules not only vaporizes while maintaining the molecular structure, but also includes light and thermal reactions such as complex decomposition and ionization. While the matrix molecules are vaporized, the molecules to be measured in the crystal are also vaporized at the same time. However, if there are few interactions between the molecules to be measured, it is necessary to vaporize them independently in a single molecule unit. . Since most of the energy of the laser light is absorbed by the matrix molecules, it is ideal that the measurement target molecule itself does not fragment. In addition, in order to actually measure the mass of the molecule to be measured, the molecule to be measured needs to be ionized. This ionization process also involves protonation from matrix molecules (cation generation by proton addition), Addition of ions from ionization promoters such as deprotonation (anion generation by proton extraction), radical cation (cation generation by electron extraction), radical anion (anion generation by electron donation), metal salt (metal) Ion addition: cation generation, halogen ion addition: anion generation) and the like are known.

  As described above, in the MALDI method, it is considered that the matrix molecule is deeply involved in the vaporization (desorption) and ionization processes of the measurement target molecule, and the measurement target molecule is efficiently desorbed and ionized. In particular, in the MALDI method, even a compound with a molecular weight of tens of thousands or more can be treated as a molecule to be measured because the matrix molecule itself and its decomposition products act as a carrier for the molecule to be measured when the matrix molecule is vaporized. It is thought that there is.

  However, the matrix molecules and their decomposition products are often ionized at the same time, and these compounds also appear as uninvited customers in the mass spectrum. Furthermore, the reaction process of decomposing the matrix molecules is complicated, and various molecules such as measurement target molecules, ionization accelerators, solvents used for sample preparation, laser light intensity, wavelength, polarity of measurement target, ion acceleration voltage, etc. Due to the influence of the measurement parameters, the peaks derived from the matrix appearing in the mass spectrum are very complex and it is impossible to identify substantially all of them.

  Thus, as a result of intensive studies by the present inventors, if a compound that decomposes to a mass number of less than 160, preferably a mass number of less than 50, is selected as a matrix by laser light irradiation, In the analysis of the mass spectrum, it was found that there was almost no trouble as a contaminant. In a biochemical material in which the MALDI method is used, as a compound that may appear in a low molecular weight range, for example, an essential amino acid has a mass number of about 120 to 200, a monosaccharide has about 150 to 180, and constitutes DAN. Four bases are about 110 to 150, and most of the plasticizers and antioxidants used as added to the synthetic polymer material are compounds having a mass number of 200 or more.

  By using a compound represented by the following general formula (1), the present inventors decomposed these compounds into compounds having a mass number of less than 160 by irradiation with laser light, and almost hindered the analysis of mass spectrometry results. I found out that I would not come.

In the general formula (1), R ₁ , R ₂ and R ₃ are each selected from an alkyl group, an alkoxy group, a hydroxy group, a morpholino group and an aryl group, and represent a substituent. R ₂ and R ₃ may form a ring with each other. R ₄ represents a substituent selected from a hydrogen atom, a hydroxy group, an amino group, an ether group, a thioether group, and an alkyl group.

  Examples of the compound represented by the general formula (1) include the following compounds.

  Although not all the reactions to such compounds to light have been clarified, the mechanism of the photodegradation reaction described below has been elucidated for some compounds. The mass number of any decomposition product is generally less than 160, and since no ionic species are generated, it is not detected as an anion or cation in the mass spectrum.

  However, these reaction processes are also under limited conditions, and the same reaction as in the measurement of the mass spectrum does not always occur. In addition, these decomposition products also contain active radical species. For example, as shown in the following reaction formula, these radical species may produce another by-product having a large mass number. .

  As a result of further detailed studies by the present inventors, it is effective to use a compound that is decomposed to a smaller unit by laser light irradiation in order to obtain a peak with less impurities in a lower molecular weight region. I found out. Examples of the compound that satisfies this requirement include compounds represented by the following structural formula.

  These compounds are decomposed mainly into compounds having a mass number of less than 50, such as nitrogen gas, carbon dioxide, carbon monoxide, and water, by heating during laser light irradiation. Furthermore, since these decomposition products do not have a reaction activity such as radical species, there is little probability that a complicated side reaction will occur.

  However, phenylsulfonylhydrazide-based compounds such as B-5 and B-6 cause not only the release of nitrogen gas and water, but also a reaction in which a by-product represented by the following reaction formula is also generated. Since some of these by-products include those having a mass number of about 200 to 280, it may occur that these compounds interfere with the analysis in the mass spectrum.

  As a result of further investigations on compounds that generate by-products having a mass number of about 200 to 280 by irradiation with laser light, or that are desorbed and ionized as they are without being decomposed, these compounds are converted into microporous membranes. By supporting it in the pores or in the mesopores of the mesoporous film, the compound having a mass number of less than 160 and further using the exemplified compounds B-1 to B-6 by irradiation with laser light, only the compound having a mass number of less than 50 is used. Has been found to be able to be selectively generated outside the pores, and more effective results can be obtained in the present invention.

  Further, when the laser beam of the mass spectrometer does not necessarily have sufficient light absorption, it is difficult to efficiently decompose the matrix. In this case, the matrix molecules of the present invention are supported in the micropores of the microporous film or the mesoporous film of the mesoporous film that absorbs the irradiated laser light, thereby absorbing the laser light energy in the microporous film or mesoporous film. The energy can be transferred to the matrix molecules through the pore walls in the membrane, and as a result, even in a matrix that does not absorb laser light, the low molecular weight compound can be selectively microporous or It was found that it can be generated outside the mesopores.

  Here, porous films such as a microporous film and a mesoporous film will be described. These porous membrane plates used in the present invention are microporous membranes having a pore size of 2 nm or less, or mesoporous membranes having a pore size of 2 nm to 50 nm. This is because when a so-called macroporous membrane having a pore diameter exceeding 50 nm is used, it is difficult to suppress a compound having a mass number of 160 or more and having a relatively large mass number from being released outside the macropores. Moreover, there is no limitation in particular about the raw material which forms these porous membranes, It is possible to use an inorganic compound, an organic compound, and an inorganic-organic hybrid compound. In particular, it is preferable to use an inorganic material in view of the generation of substances that cause impurities from the porous film itself by laser light irradiation.

  Conventionally known inorganic microporous or mesoporous films can be used. In particular, porous silica and silica gel made of zeolite or silicon dioxide have many examination examples, and the pore diameter and specific surface area can be easily adjusted according to the purpose.

  The pore diameter in the porous film can be observed using an electron microscope, a transmission electron microscope, or the like. Moreover, regarding the regularity of the pore structure, X-ray diffraction measurement can be used. When the pore membrane has a regular structure, the pore structure interval d100 (nm) is obtained from the peak diffraction angle 2θ observed by the X-ray diffraction analysis based on Bragg's law by the following formula (1). .

d100 = λ / 2sin θ (1)
Here, λ (nm) is an X-ray wavelength, and CuKα is used as a radiation source in the present invention.

  Further, a nitrogen laser having a wavelength of λ = 337 nm is currently widely used as a laser light source used in the MALDI method. Examples of inorganic materials that have sufficient absorption in the wavelength of this nitrogen laser include titanium oxide and tungsten oxide. Even when a matrix that does not have sufficient absorption with respect to 337 nm light is supported in the pores of porous titanium oxide or porous tungsten oxide having these pore walls, the decomposition reaction is efficiently performed. Thus, it becomes possible to release a low molecular weight compound that can act as a carrier for the compound to be measured out of the pores.

The matrix compound of the present invention may be used by adding a metal salt such as CF ₃ COOM (M = Li, Na, K, Ce, Ag) for the purpose of promoting ionization of the molecule to be measured. It is also possible to use a mixture of two or more of the matrices of the present invention. Furthermore, the matrix of the present invention can be used by mixing conventionally known matrix molecules such as 9-NA, DHB, and CHCA in a range that does not interfere with the measurement and analysis of the peaks of the contaminants. It is.

  The substrate for mass spectrometry of the present invention is provided with a microporous film or mesoporous film on the surface of a metal or semiconductor substrate, further supports a matrix compound in the micropore or mesopore, and measures for mass spectrometry by irradiation laser light. The target molecule can be continuously and efficiently desorbed and ionized. According to the mass spectrometer for the substance desorption and ionization method of the present invention using the substrate for mass spectrometry, the molecule to be measured for mass spectrometry can be ionized continuously under relatively mild conditions, and sample preparation is simple. In addition, the noise derived from the ionization aid during mass spectrometry can be greatly reduced to improve analysis accuracy. Therefore, by using this ionization method, it is possible to easily mass-analyze substances with a wide range of molecular weights with high accuracy, and in particular, it is possible to easily perform partial structure analysis, molar distribution, molecular weight distribution, etc. of low molecular weight compounds. it can.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

<Measured substances>
Triacetyl-β-cyclodextrin (molecular formula = C ₈₄ H ₁₁₂ O ₅₆ / molecular weight = 2017.75, Tokyo Kasei: product code = T1844) was dissolved in tetrahydrofuran, and a measurement sample of 100 μmol / L. A solution was prepared.

<Example 1>
1 mL of a tetrahydrofuran solution of the substance to be measured is taken, and the compound represented by the structural formula A-1 (2,2-dimethoxy-1,2-diphenylethane-1-one, trade name: RGACURE, as a matrix molecule) 651, manufactured by Ciba Specialty Chemicals Co., Ltd.) was added so that the concentration of the matrix molecule was 5 mmol / L. 1 μL of this mixed solution was taken with a pipetter and dropped onto a sample target substrate made of stainless steel for MALDI-TOF MS measurement and dried.

<Examples 2 to 10>
In Example 1, except that the matrix molecules were changed to the compounds shown in Table 1, a measurement sample was prepared in the same manner and dropped onto a sample target substrate and dried.

<Comparative Example 1>
In Example 1, a measurement sample was prepared and dropped in the same manner except that 9-nitroanthracene (manufactured by Aldrich, product number: N10209) was used instead of the matrix molecule A-1.

<Comparative example 2>
In Example 1, a measurement sample was prepared and dropped in the same manner except that α-cyano-hydroxy-cinnamic acid (manufactured by Aldrich, product number: 145505) was used instead of the matrix molecule A-1.

<Comparative Example 3>
In Example 1, a measurement sample was prepared in the same manner except that the measurement target molecule solution was dropped as it was without adding matrix molecules.

<Example 11>
20 parts by mass of tetraethylorthosilicate (manufactured by Aldrich, product number = 86578) and 6.5 parts by weight of triethoxyvinylsilane (manufactured by Aldrich, product number = 95080), 1 part by weight of tetraisopropoxytitanium (manufactured by Aldrich, product number) = 205273) and 7.5 parts by mass of stearyltrimethylammonium chloride were added and mixed (Ti / Si molar ratio = 1/50). To this, 2 parts by mass of 0.1 N hydrochloric acid was further added and mixed for 30 minutes. The obtained transparent viscous liquid was spin-coated (rotation speed: 1000 RPM) on an n-type silicon wafer (antimony dope, manufactured by Mitsubishi Sumitomo Silicon Co.) and dried at 60 ° C. for 1 day.

  This was calcined in air at 500 ° C. for 3 hours to remove the template stearyltrimethylammonium chloride, and a thin film of porous silica-titania composite material was obtained.

  When this substrate was subjected to X-ray diffraction analysis (X'Pert PRO, Philip), a clear diffraction peak was observed at an interplanar spacing of 5 nm, so it can be said that it has a regular mesoporous pore structure.

  1,1,1,3,3,3-hexamethyldisilazane (product code = H0089) manufactured by Tokyo Chemical Industry Co., Ltd. was formed by forming a porous silica-titania film having mesoporous pores on the silicon wafer. It was immersed for 30 minutes and rinsed with hexane for hydrophobization. Further, the porous substrate subjected to the hydrophobization treatment was immersed in a chloroform saturated solution (25 ° C.) of the matrix molecule represented by the structural formula A-1 for 3 hours and rinsed with methanol. This substrate was bonded and fixed to the sample target substrate for MALDI-TOF MS measurement cut by 0.6 mm with a conductive double-sided tape. On this matrix-containing porous substrate, 1 μL of 100 μmol / mL sample solution (tetrahydrofuran) was dropped and dried to prepare a measurement sample.

<Examples 12 to 17>
In Example 11, a measurement sample was prepared in the same manner except that the compounds shown in Table 1 were used instead of the matrix molecule A-1.

<Measurement of mass spectrum>
The measurement was performed using a commercially available MALDI-TOF MS apparatus (trade name: REFLEX-III, manufactured by Bruker Daltonics). The irradiation laser was a nitrogen laser (wavelength = 337 nm), and a positive ion reflection mode (reflector mode) was used. The irradiation laser intensity is measured at an intensity 2% stronger than the intensity at which the peak of the parent ion starts to appear, and the spectrum for 20 pulses is integrated at one location, and integrated over 10 locations, for a total of 200 pulses. A spectrum obtained by summing up signal intensities obtained from laser irradiation was obtained.

  In addition, the acceleration voltage was set to 26.5 kV, and peaks with a mass number of 0 to 2500 were captured.

  Further, the cut-off value in the low molecular weight region in the measurement was 0 or more, that is, the cation species flying to the detector were taken in all regions without the cut-off.

  Evaluation of the obtained spectrum is a molecule to be measured (a peak appearing in the molecular weight range: 2018-2125 as a parent ion as an adduct of a proton or a monovalent metal cation such as Na, K, and Ag on a substrate) And the intensity and type of peaks of contaminants derived from the degradation product and matrix of the measured molecule in the molecular weight region 160 to 100, and derived from the degradation product and matrix of the measured molecule in the molecular weight region 50 to 160 Judgment was made based on the intensity of the peaks and the number of types of impurities. In each spectrum, the relative intensities of parent ions and contaminant peaks were compared, and those without any intensity were ranked 0, or less, and ranked 1-5 as the intensity increased or the types increased. . The evaluation results are summarized in Table 1.

  From the above Examples and Comparative Examples, by using the matrix compound of the present invention, it is possible to suppress the degradation peak of the measurement molecule in the low molecular weight range and the contaminant peak derived from the matrix, and to obtain the parent peak with high intensity. It is confirmed that Furthermore, it is confirmed that the effect is more effectively exhibited by supporting the matrix on the porous substrate.

Claims (11)

  A matrix compound for mass spectrometry characterized in that a molecule to be measured is desorbed and ionized by a main decomposition product decomposed into a compound having a mass number of less than 160 by irradiation laser light in the matrix compound for mass spectrometry.   The matrix compound for mass spectrometry according to claim 1, wherein the main decomposition product decomposed by the irradiation laser beam has a mass number of less than 50. The matrix compound for mass spectrometry according to claim 1 or 2, wherein the matrix compound has a structure represented by the following general formula (1).

In (the above general formula _(1), R 1, _{R 2} and _{R 3} are each an alkyl group, an alkoxy group, hydroxy group, morpholino group, selected from an aryl group or a substituted group. Further, _{R 2} and _{R 3} are each (R ₄ may represent a substituent selected from a hydrogen atom, a hydroxy group, an amino group, an ether group, a thioether group, and an alkyl group.) The matrix compound for mass spectrometry according to claim 1 or 2, wherein the matrix compound is a compound selected from the following structural formula group.
  In a substrate for mass spectrometry, a compound having a mass number of less than 160 by irradiation laser light provided with a microporous film or a mesoporous film on a metal or semiconductor substrate, further supporting a matrix compound in the micropore or mesopore. A mass spectrometric substrate characterized by selectively generating only outside the pores.   The substrate for mass spectrometry according to claim 5, wherein the mass number of the compound selectively generated outside the micropores or the mesopores is less than 50. The substrate for mass spectrometry according to claim 5 or 6, wherein the matrix compound has a structure represented by the following general formula (1).

In (the above general formula _(1), R 1, _{R 2} and _{R 3} are each an alkyl group, an alkoxy group, hydroxy group, morpholino group, selected from an aryl group or a substituted group. Further, _{R 2} and _{R 3} are each (R ₄ may represent a substituent selected from a hydrogen atom, a hydroxy group, an amino group, an ether group, a thioether group, and an alkyl group.) The substrate for mass spectrometry according to claim 5 or 6, wherein the matrix compound is a compound selected from the following structural formula group.
  The substrate for mass spectrometry according to any one of claims 5 to 8, wherein the substrate for mass spectrometry has absorption with respect to an irradiation laser.   The substrate for mass spectrometry according to any one of claims 5 to 9, wherein the substrate for mass spectrometry has at least one diffraction peak in an angle region corresponding to a structural periodicity of 1 nm or more in X-ray diffraction measurement.   A matrix-assisted laser desorption / ionization mass spectrometer, wherein the mass spectrometer substrate according to any one of claims 5 to 10 is mounted.