JPH02115761A - Method and apparatus for mass spectrometric analysis of organic compound - Google Patents

Abstract

PURPOSE:To facilitate the identification of an org. compd. by irradiating the neutral particle released in a prescribed period of time by irradiation of another laser beam, thereby ionizing the particle. CONSTITUTION:A secondary ion 5 and the neutral particle 12 are released when a sample 4 is irradiated with the laser beam 11 by a 1st laser generator 10. The secondary ion 5 is immediately led out by a leader electrode 6 at this time but the neutral particle 12 is gradually released from the sample surface. The neutral particle 12 is irradiated with the laser beam 14 by the 2nd laser generator 13 with a prescribed time delay after the irradiation of the laser beam 11, by which the particle is ionized to a photoexcited ion 15 which is subjected to mass spectrometric sepn. by a TOF type mass spectrometer 16. Then, the photoexcited ion 15 is detected after the arrival of the secondary ion 5 at an ion detector 9 and, therefore, the structure of the sample is easily identified by the photoexcited on which well indicates the mass number of the side chain.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a method for identifying an organic compound as an analyte by measuring the mass number of molecules generated by decomposing the organic compound by mass spectrometry. The present invention relates to an organic compound mass spectrometry method for identifying the molecular structure of the organic compound and an apparatus thereof.

(Prior art) Conventionally, a solid organic compound is irradiated with a laser beam or an ion beam to decompose the compound, and the secondary ions that are generated in the small molecules are subjected to mass spectrometry to determine their mass distribution. Mass spectrometry is being used to identify the original organic compound.

As an example of a specific method for measuring organic compounds, FIG. 4 shows the configuration of an example of a static secondary ion mass spectrometer.

An ion beam (-order ion beam) 2 that sputters the surface of the sample 4 is generated from a −order ion generator 1 . This secondary ion beam 2 is an ionized gas or metal vapor. - When a partial ion beam 2 from the secondary ion generator 1 is irradiated onto the surface of the sample 4 through the converging lens system 3, secondary ions 5 are sputtered from the sample 4 due to the impact. The secondary ions 5 are extracted through an extraction electrode 6 and then through a converging lens system 7. The extracted secondary ions 5 pass through a mass spectrometer 8, are separated by X amount, and reach an ion detector 9. In this case, the current amount of negative ions is about 1 nA.

Further, FIG. 5 shows the configuration of an example of a laser excitation mass spectrometer. A pulsed laser beam 11 generated by a laser generator 10 is irradiated onto the surface of the sample 4. This pulsed laser beam 11 generates secondary ions 5 similar to the static secondary ion mass spectrometer described above, and similar mass spectrometry systems 6 to 6 are generated.
Secondary ions are detected through 8 by an ion detector.

(Problem B to be solved by the invention) Figure 6 shows the mass spectrum measured with the above-mentioned Statec secondary ion mass spectrometer (D, Br1gg5゜5u
rf Interface Anal, 9.391
．． (1986) ), the sample is polyhydroxy methacrylate. The peak indicated by the arrow represents the mass of the underlined portion of the side chain, but when the sample is a large molecule like this, there are molecules with various masses other than the peak representing the mass of a part of the compound. Detected. This is because complex hydrocarbon molecular ions and cluster ions, which are aggregates of carbon, are generated due to recombination of decomposed molecules. Due to the ordering of molecular ions in this manner, it is difficult to distinguish only molecules with masses that indicate the molecular structure of the original compound, making it difficult to identify the molecular structure. Note that the number written x3 in FIG. 3 indicates that the portion to the right of the broken line was measured at a measurement magnification of 3.

FIG. 7 is a diagram showing a mass spectrum of laser excitation mass spectrometry, which uses an ultraviolet laser as a means for decomposing a compound and measures secondary ions generated by the laser. In this case as well, complex molecular ions are generated.

As described above, conventional mass spectra were complicated due to the generation of complex molecular ions, making it difficult to identify high-molecular organic compounds such as polymers.

Additionally, organic compounds such as polymers are generally insulators;
Charge is retained on the sputtered surface due to secondary ions and secondary electrons generated by ion and laser beam irradiation. Due to the influence of this charge, the ion collection efficiency is lowered and the analytical sensitivity is lowered.

(Means for Solving the Problems) In laser excitation mass spectrometry, generation of secondary ions ends within about 100 nsec after irradiation with a laser beam with a pulse width of 10 nsec. In contrast, the inventors of the present application have clarified the behavior of neutral particle generation when a sample is decomposed with a laser beam, which was not clear until now. The situation is shown in FIG. The sample is GaAs. The horizontal axis is the elapsed time after the sample was irradiated with the laser beam (the time between the generation of the first laser beam and the generation of the second laser beam), and the vertical axis is the time elapsed since the sample was irradiated with the laser beam. Indicates the intensity (amount of generation) of sexual particles. From this result, it was found that neutral particles continue to be generated for several tens of microseconds, which is several hundred times longer than secondary ions. The surface temperature of the sample immediately after laser beam irradiation is several thousand degrees, but it rapidly drops within several tens of microseconds. In other words, the conditions for generating secondary ions are extremely high temperature and unstable conditions, whereas the conditions for generating neutral particles are relatively stable. From this, it can be concluded that neutral particles generate fewer molecular ions than secondary ions, and particles that reflect the molecular structure of the original compound are more likely to be generated.

The present invention uses a pulsed laser beam as a means for decomposing a sample made of an organic compound, and after irradiating the laser beam,
Neutral particles emitted at a predetermined time are ionized and detected by irradiating a laser beam different from the laser beam described above. As a result, fewer molecular ions are generated than in conventional measurements of secondary ions, and it becomes possible to detect only the mass spectrum representing the structure of the organic compound.

(Example) Examples of the present invention will be described in detail below.

Since neutral particles have no charge, it is difficult to perform mass separation as they are. Therefore, the generated neutral particles are ionized by irradiating them with a high-power laser beam. The configuration of the mass spectrometer for organic compounds of the present invention is shown in FIG. A first pulsed laser beam 11 is generated from a first laser generator 10 .

Next, the sample 4 is irradiated with the first laser beam 11 .

Secondary ions 5 are removed from the sample 4 by irradiation with the laser beam 11.
and neutral particles 12 are released. The secondary ions 5 are quickly extracted by the extraction electrode 6. On the other hand, neutral particles 1
2 is gradually released from the sample surface.

This is ionized by irradiating it with a second pulsed laser beam 14 generated from a second laser generator 13.

Photoexcited ions 15, which are neutral particles ionized, are extracted by an extraction electrode 6 and subjected to mass separation by a mass spectrometer 16. In this case, the mass analyzer 16 is a TO
It is a P-type mass spectrometer. The results of W content analysis of polyphenyl methacrylate measured by this mass spectrometer are shown in FIG. The horizontal axis is the flight time, which indicates the time from when the sample particles were ejected by the first laser beam irradiation. Since the secondary ions 5 are drawn out to the t-quantity analysis system at the same time as they are generated, they quickly reach the ion detector 9. Thereafter, the photoexcited ions 15 separated by ¥ti are detected. In this case, secondary ions 5 are detected first, and photoexcited ions 1 are detected later.
In order to distinguish the photoexcited ions 15 from the secondary ions 5, the photoexcited ions 15 must be generated after the generation of molecular ions contained in the secondary ions 5 has completely completed. Molecular ions are released for a maximum of about 30 μsec after the first ion is detected. Therefore, the light emission of the second pulsed laser needs to be delayed by 30 μsec or more from the laser irradiating the sample. The photoexcited ions well represent the mass numbers of side chains, as shown in FIG. Furthermore, there were almost no molecular ions among the photoions, which proved to be effective in identifying the structure of the sample.

If the emission of the second laser that ionizes neutral particles is delayed, the mass number of photoexcited ions that can be measured tends to increase, which is advantageous for identification. On the contrary, the intensity of photoexcited ions decreases, so it is necessary to freely change the laser emission time depending on the measurement purpose and obtain mass spectra at several different emission times.

Sharp application 1 If the wavelength of the laser beam 11 irradiated onto the sample is in the infrared region, high temperatures will not be generated on the sample surface, so the generation of secondary ions can be suppressed. For this reason, it becomes impossible to perform conventional laser excitation tt analysis, but since neutral particles are generated, mass analysis of photoexcited ions according to the present invention is possible. By suppressing the generation of secondary ions, there is no charge accumulation on the sample surface, making it easier to measure insulating polymers. Furthermore, more stable neutral particles can be generated than under conditions where secondary ions are generated. FIG. 3 shows an example in which the wavelength of the laser beam irradiated onto the sample was set in the infrared region. The feature is that there is no generation of secondary ions.

(Effects of the Invention) As explained above, the mass spectrometry method for organic compounds of the present invention has the advantage that organic compounds can be identified more easily than before.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the mass spectrometer for organic compounds of the present invention. Figure 2 is a diagram showing an example of measurement by the mass spectrometry method of the present invention. Figure 3 shows the wavelength of the laser beam irradiated to the sample in the infrared region. Figure 4 is a configuration diagram of an example of a conventional static secondary ion ffff1 analyzer, and Figure 5 is a configuration diagram of an example of a laser-excited mass spectrometer. , Figure 6 shows an example of a spectrum obtained by conventional static secondary ion mass spectrometry, Figure 7 shows a spectrum obtained by laser excitation mass spectrometry, and Figure 8 shows the generation of neutral particles by laser irradiation. It is a diagram showing behavior. 1...-Next ion generator 2...-Next ion beam 3...Convergent lens system 4.
...Sample 5...Secondary ion 6...Extraction electrode 7...Converging lens system 8...Mass spectrometer 9...Ion detector 10...First laser generator 11...・First pulsed laser beam 12...Neutral particles 13...Second laser generator 14...Second pulsed laser beam 15...Photoexcited ions 16...TOF mass spectrometer No. Figure 2: Tomb Gyōsō-ma (, US) Figure 3: 4 Old I-Ikuji 15 (ps) Figure 4! 0-・Luther 1 Generator 11--・Harrus U-Sa” Beam ion 5#, degrees (α, U,)

Claims (1)

[Claims] 1. A mass spectrometry method for organic compounds in which the molecular structure of the organic compound is determined by evaporating the constituent molecules of the organic compound that is the sample to be analyzed and measuring the mass of the evaporated molecules, irradiating the organic compound with a first pulsed laser beam to evaporate constituent molecules of the organic compound; generating a second pulsed laser beam at a predetermined time after irradiating the first laser beam; An organic compound characterized in that the molecular structure of the organic compound is identified by ionizing the vaporized molecules by irradiating the vaporized molecules with a second pulsed laser beam and subjecting the ionized molecules to mass spectrometry. Mass spectrometry. 2. A first laser generator that irradiates a sample made of an organic compound with a first laser beam; and a second laser generator that irradiates the sample with a second laser beam later than the first laser beam. , comprising an electrode for extracting secondary ions emitted from the sample and photoexcited ions ionized by irradiation with a second laser beam, and a mass spectrometer for mass-separating the photoexcited ions extracted by the electrode. Characteristic mass spectrometer for organic compounds.