JP7078382B2 - Time-of-flight mass spectrometer and mass spectrometry method - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act Publications The 66th Annual Meeting of the Japan Society for Analytical Chemistry Publication Date August 26, 2017 [Publications, etc.] Meeting Name The 66th Annual Meeting of the Japan Society for Analytical Chemistry Date 2017 September 11, 2014

The present disclosure relates to a time-of-flight mass spectrometer and a mass spectrometry method.

Time-of-flight mass spectrometers are widely used for the analysis of organic compounds due to their high sensitivity. Toxic substances such as dioxins and carcinogens such as nitroaromatic compounds, which have extremely low concentrations, are desired to have sufficiently high sensitivity for analysis with subfemtogram accuracy. As a method for achieving such high sensitivity, a time-of-flight mass spectrometer using a femtosecond laser beam has been proposed (for example, Non-Patent Document 1).

“Gaschromatography / multiphotonization / time-of-flight mass spectrometry using afemtosecond laser”, Anal Bioanal Chem, (2013) 405: 6907-6912

In order to improve the analytical sensitivity of trace components, it is preferable to irradiate as many molecules as possible contained in the measurement sample with laser light. From this point of view, it is considered effective to use a laser with a high repetition rate. However, when the repetition rate is high, the ion signals for each optical pulse are overlapped and observed, so it is necessary to shorten the flight time of the ions. Further, although it is considered that the installation space is reduced and the convenience is improved if the size is reduced, the flight time of ions is shortened when the flight area is shortened. Here, if the flight time of the ions is shortened, there is a concern that the mass resolution will be lowered.

Therefore, it is an object of the present disclosure to provide a time-of-flight mass spectrometer that can be miniaturized in one aspect, has a wide dynamic range of measurement, and has excellent mass resolution. Further, in another aspect, it is an object of the present invention to provide a mass spectrometric method having a wide dynamic range of measurement and excellent mass resolution.

In one aspect, the present invention is generated in a light emitting portion that emits a femtosecond laser beam or a picosecond laser beam, an ionization region that ionizes a component to be measured by the femtosecond laser light or the picosecond laser light, and an ionization region. Time correlation that measures the time interval between the flight area where the ions fly, the detector that detects the ions that have flown in the flight area, and the femtosecond laser light or picosecond laser light and the ion detection signal detected by the detector. Provided is a flight time type mass analyzer comprising a single ion counting unit and having a distance between a repeller electrode provided on the upstream side of the flight region and a detection unit of 20 cm or less.

The time-of-flight mass spectrometer of the present invention includes a time-correlated single ion counting unit that counts the time interval between a light emitting unit that emits femtosecond laser light or picosecond laser light and an ion detection signal detected by the detection unit. Be prepared. Therefore, it is possible to reduce noise, improve the S / N ratio, and reduce the lower limit of detection of the component to be measured. On the other hand, when the time-correlated single-ion counter is used, it is necessary to increase the number of times of integration of the flight time data of the ions in order to widen the dynamic range (measurable concentration range) of the measurement. Here, if the number of times the flight time data is integrated is increased, the time required for mass spectrometry tends to increase.

Therefore, the flight time type mass analyzer of the present invention includes a light emitting unit that irradiates a sample with femtosecond laser light or picosecond laser light. By increasing the repetition rate of the pulse of the femtosecond laser beam or the picosecond laser beam in the light emitting unit, the number of times the flight time is integrated can be easily increased and the dynamic range of the measurement can be widened. Since the time-correlation single-ion counter can process high-speed data, flight time data can be integrated even if the pulse repetition rate is increased. Further, since it has a light emitting unit that irradiates a femtosecond laser beam or a picosecond laser beam and a time-correlated single ion counting unit, mass resolution can be improved.

Further, the distance between the repeater electrode provided on the upstream side in the flight region and the detection unit is 20 cm or less. Therefore, the time-of-flight mass spectrometer can be downsized. As a result, the installation space of the time-of-flight mass spectrometer can be reduced, and the portability and operation of the device can be facilitated. Generally, the shorter the flight area, the lower the mass resolution tends to be. However, since the time-of-flight mass spectrometer of the present invention includes a time-correlated single-ion counter, it is possible to maintain high mass resolution even if the flight region is short. Further, since the collision between the ion and the residual gas in the flight region can be reduced, an inexpensive exhaust device having a small exhaust capacity can be used. Further, since the flight time can be further shortened, an organic molecule having a large molecular weight may be contained in the measurement target component.

It is preferable to use a fiber laser as the light emitting unit. A fiber laser having a high repetition rate can reduce the energy per pulse to reduce the space charge effect and increase the number of integrations. Therefore, the dynamic range can be sufficiently widened while improving the mass resolution. In addition, it is low in cost and excellent in reliability.

The flight time of ions in the flight region is preferably 30 μs or less. By shortening the flight time, it is possible to utilize a high-power fiber laser with a high repetition rate. In addition, the number of signal integrations can be increased to widen the dynamic range. Therefore, the sensitivity of the analysis can be increased and the measurement time can be shortened.

The energy per pulse of femtosecond laser light or picosecond laser light is preferably 100 μJ or less. As a result, the space charge effect can be reduced and the saturation of the detected peak can be suppressed. Therefore, the dynamic range can be widened while further improving the mass resolution.

It is preferable to use a capillary in the portion where the component to be measured is introduced into the ionization region. As a result, when the gas chromatograph is provided on the upstream side of the ionization region, the dead volume can be ignored, and the deterioration of the resolution of the gas chromatograph can be suppressed.

The time-of-flight mass spectrometer of the present invention preferably has a gas chromatograph on the upstream side of the ionization region. Thereby, even a sample containing a plurality of components can be analyzed separately. In order to perform mass spectrometry of each component separated by gas chromatograph, it is necessary to perform mass spectrometry in a short time. Since the flight time type mass analyzer of the present invention includes a light emitting unit that irradiates a femtosecond laser beam or a picosecond laser beam and a time-correlated single ion counting unit, a pulse of the femtosecond laser light or the picosecond laser light is provided. By increasing the repetition rate of, mass analysis can be performed in a short time.

In another aspect, the present invention is a mass analysis method using a time-of-flight mass analyzer, wherein the component to be measured is irradiated with a femtosecond laser beam or a picosecond laser beam to ionize the component to be measured. Using the process of detecting ions that have flown in the flight area with the detection unit and the time-correlated single ion counting method, the time interval between the femtosecond laser light or picosecond laser light and the ion detection signal detected by the detection unit is determined. Provided is a mass analysis method having a step of measuring and having a distance between a repeller electrode provided on the upstream side of a flight region and a detection unit of 20 cm or less.

The mass spectrometric method of the present invention uses a time-correlated single ion counting method and includes a step of counting ions. Therefore, it is possible to reduce noise, improve the S / N ratio, and reduce the lower limit of detection of the component to be measured.

Further, in this mass spectrometry method, a femtosecond laser beam or a picosecond laser beam is applied to a sample to generate ions. By using a femtosecond laser beam or a picosecond laser beam having a high repetition rate, the number of times the ion flight time data is integrated can be increased. Since the time-correlation single-ion counter can process high-speed data, flight time data can be integrated even if the pulse repetition rate is increased. That is, the analysis method of the present invention improves the analysis sensitivity and mass resolution by using a high-power femtosecond laser beam or picosecond laser beam having a high repetition rate and adopting a time-correlated single-ion counting method. , The dynamic range can be widened.

Further, in the flight time type mass spectrometer used in the above mass spectrometry method, the distance between the repeller electrode provided on the upstream side of the flight region and the detection unit is 20 cm or less. Therefore, the time-of-flight mass spectrometer can be downsized. As a result, the installation space of the time-of-flight mass spectrometer can be reduced, and the portability and operation of the device can be facilitated. Generally, the shorter the flight area, the lower the mass resolution tends to be. However, in the present invention, since the time-correlated single ion counting method is used, the mass resolution can be maintained high even if the distance is short. Further, since the collision between the ion and the residual gas in the flight region can be reduced, an inexpensive exhaust device having a small exhaust capacity can be used. Further, since the flight time can be further shortened, an organic molecule having a large molecular weight may be contained in the measurement target component.

According to the present disclosure, it is possible to provide a time-of-flight mass spectrometer which can be miniaturized, has a wide dynamic range of measurement, has high sensitivity, and has excellent mass resolution. Further, it is possible to provide a mass spectrometry method having a wide dynamic range of measurement and excellent mass resolution.

FIG. 1 is a diagram showing an outline of an embodiment of a time-of-flight mass spectrometer. FIG. 2 is a diagram for explaining the internal structure of the main body of the time-of-flight mass spectrometer. FIG. 3 is a diagram showing an example of the relationship between the pulse interval of the laser beam and the flight time. FIG. 4A is a diagram showing a mass spectrum of Example 1. FIG. 4B is the result of theoretical calculation of the absorption spectrum of pinene contained in the sample measured in Example 1. FIG. 5 is a diagram showing a mass spectrum of Example 2. FIG. 6 is a graph showing the relationship between the concentration of pinene and the counting probability of the peak corresponding to pinene. FIG. 7A is a diagram showing a mass spectrum of Example 4. FIG. 7B is the result of theoretical calculation of the absorption spectrum of eugenol contained in the sample measured in Example 4.

Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings as the case may be. However, the following embodiments are examples for explaining the present invention, and the present invention is not intended to be limited to the following contents. In the description, the same reference numerals are used for the same elements or elements having the same function, and duplicate description may be omitted in some cases. The dimensional ratio of each element is not limited to the ratio shown in the figure.

FIG. 1 is a diagram showing an outline of an embodiment of a time-of-flight mass spectrometer. The flight time type mass analyzer 100 includes a light emitting unit 10 that emits femtosecond laser light or picosecond laser light, an ionization region that ionizes the component to be measured with femtosecond laser light or picosecond laser light, and an ionization region. Data obtained by the main body 20 having a flight region in which the generated ions fly, the signal processing unit 30 having a time-correlated single ion counting unit 33 for counting the ions, and the multi-channel analyzer 34, and the signal processing unit 30 (the signal processing unit 30). A display unit 50 for displaying (mass spectrum) is provided.

As the light emitting unit 10, a light emitting unit that emits femtosecond laser light or picosecond laser light used as an ionization light source of a sample can be appropriately used. As the light emitting unit 10, for example, a titanium sapphire laser may be used, or a fiber laser may be used. Of these, it is preferable to use a fiber laser. Since the fiber laser has a high repetition rate, the energy per pulse can be reduced to reduce the space charge effect, and the number of times of integration of flight time data can be increased to sufficiently widen the dynamic range. Therefore, the mass resolution can be further improved and the accuracy of the analysis value can be improved. In addition, the fiber laser can reduce the cost while being excellent in reliability. The fiber laser may be a Yb (itterbium) fiber laser or an Er (erbium) fiber laser. Of these, the Yb fiber laser is preferable from the viewpoint of further increasing the average output.

The upper limit of the pulse width of the femtosecond laser beam is preferably 700 fs, more preferably 100 fs, from the viewpoint of improving the analysis sensitivity. The lower limit of the pulse width of the femtosecond laser beam is, for example, 1 fs. From the same viewpoint, the upper limit of the pulse width of the picosecond laser beam is preferably 700 ps, more preferably 100 ps. The lower limit of the pulse width of the picosecond laser beam is, for example, 1 ps. From the viewpoint of sufficiently improving the analysis sensitivity, the light emitting unit 10 preferably emits femtosecond laser light.

The energy per pulse of the femtosecond laser beam or picosecond laser beam is preferably 100 μJ or less, more preferably 60 μJ or less, and further preferably 60 μJ or less, from the viewpoint of reducing the space charge effect and suppressing the saturation of the detection peak. It is preferably 40 μJ or less. The magnitude of energy may be adjusted by providing an energy adjusting unit between the light emitting unit 10 and the main body unit 20. A known filter can be used as the energy adjusting unit.

In order to perform quantitative analysis with high accuracy, the ratio of the ion counting rate to the repetition rate of the pulse of the femtosecond laser light or the picosecond laser light should be 1/10 or less in the time-correlated single ion counting unit 33. Is preferable. If this ratio exceeds 1/10, it becomes difficult to establish a proportional relationship between the number of ions and the intensity of the detected peak, and the accuracy of quantitative analysis may decrease. From this point of view, it is preferable that the repetition rate of the pulse of the femtosecond laser beam or the picosecond laser beam is high.

The repetition frequency of the pulse of the femtosecond laser light or the picosecond laser light emitted from the light emitting unit 10 is preferably 40 kHz or more, more preferably 100 kHz or more. By increasing the pulse repetition frequency of the femtosecond laser beam or picosecond laser beam, that is, increasing the pulse repetition rate, more sample molecules can be ionized and the analysis sensitivity can be increased. Further, since the ion counting speed can be increased, the integrated time of the flight time data can be shortened. Therefore, it is advantageous in analyzing the mixture in combination with a gas chromatograph. In the gas chromatograph, a normal commercial product can be connected to the sample introduction section 21 on the upstream side of the main body section 20.

By increasing the repetition frequency of pulses of femtosecond laser light or picosecond laser light and reducing the energy per pulse, it is possible to widen the dynamic range while suppressing signal saturation.

The wavelength of the femtosecond laser beam or the picosecond laser beam may be adjusted according to the type of the component to be measured. The light emitting unit 10 may have a wavelength adjusting unit for adjusting the wavelength to, for example, an ultraviolet region or a near infrared region. As the wavelength adjusting unit, a known one composed of beta-type barium borate or the like, which is a kind of nonlinear optical crystal, can be used. If the wavelength of the femtosecond laser beam or the picosecond laser beam is included in the absorption band of the component to be measured, the concentration of the sample can be measured with higher sensitivity.

Since the femtosecond laser light or the picosecond laser light is used in this embodiment, the wavelength of the femtosecond laser light or the picosecond laser light irradiated to the measurement target component is included in the absorption band of the measurement target component. It does not have to be. Even in such a case, by using the femtosecond laser beam or the picosecond laser beam, the phenomenon that electrons are once excited from the ground state to a virtual energy level and then ionized occurs frequently. Since the molecule can be efficiently ionized even in the case of non-resonance as described above, for example, even if the component to be measured is unknown, the measurement can be performed with high sensitivity.

The femtosecond laser beam or picosecond laser beam (laser light 12) from the light emitting unit 10 is introduced into the main body unit 20 after the traveling direction is adjusted by the reflecting plate 13. The component to be measured is introduced into the main body 20 from the introduction section 21. The component to be measured may be diluted with an inert gas or the like. The introduction unit 21, which is a portion into which the component to be measured is introduced, has a capillary. As a result, the gas chromatograph can be easily connected to the upstream side of the introduction unit 21.

FIG. 2 is a diagram for explaining the internal structure of the main body portion 20. The main body 20 includes an ionization region 24 for ionizing the sample with the laser beam 12, a flight region 27 for the ions generated in the ionization region 24 to fly, and a detection unit 28 for detecting the ions flying in the flight region 27.

The main body 20 has a repeater electrode 22 that applies a voltage for accelerating ions, and a pair of grid electrodes 26a and 26b that function as grounds. The ionization region 24 is partitioned by the repeater electrode 22 and the grid electrode 26a. In the ionization region 24, a sample containing the component to be measured is introduced into the ionization region 24 from the introduction unit 21 of FIG. 1. The sample is a gas containing an inert gas such as nitrogen or helium and a component to be measured. The component to be measured is, for example, an organic compound. The component to be measured is irradiated with the laser beam 12 in the ionization region 24 and is ionized. The generated ions are accelerated by the potential difference between the repeater electrode 22 and the grid electrode 26a, and fly toward the detection unit 28.

The potential difference between the repeater electrode 22 and the grid electrode 26a is preferably large from the viewpoint of accelerating the ions in the ionization region 24 and shortening the flight time of the ions flying in the flight region 27. The potential difference is preferably 3 kV or more, more preferably 10 kV or more, and further preferably 20 kV or more.

One grid electrode 26a is provided on the upstream side of the flight region 27, and the other grid electrode 26b is provided on the downstream side of the flight region 27. The pair of grid electrodes 26a and 26b thus arranged so as to face each other divide the flight region 27. The ions generated in the ionization region 24 are accelerated in the ionization region 24, pass through the grid electrode 26a, and fly in the flight region 27 toward the detection unit 28. The ions that have flown through the flight region 27 pass through the grid electrode 26b and reach the detection unit 28.

The distance L between the repeater electrode 22 and the detection unit 28 is 20 cm or less, and is preferably 15 cm or less, more preferably 10 cm or less, from the viewpoint of avoiding the overlap of the ion signals generated for each pulse of the laser light. More preferably, it is 8 cm or less. If the size is reduced in this way, the installation space of the time-of-flight mass spectrometer 100 can be further reduced and the portability can be further facilitated. For example, it can be used as a handy type monitor or a wristwatch-sized sensor.

The flight time of the ions flying in the flight region 27 partitioned by the pair of grid electrodes 26a and 26b is preferably 30 μs or less, more preferably 10 μs or less, still more preferably 4 μs or less. By shortening the flight time in this way, it is possible to use a high-power laser having a high repetition rate. Further, since the number of times the flight time data is integrated can be increased, the time required for mass spectrometry can be shortened.

Any electrode may be provided between the repeater electrode 22 and the grid electrode 26a in order to perform two-stage acceleration of ions. By providing such an electrode, it is possible to reduce the difference in ion detection timing due to the difference in ionization position and improve the mass resolution.

FIG. 3 is a diagram schematically showing an example of the relationship between the repetition frequency of the pulse of the laser light and the ion flight time in the flight region 27. 3 (A), 3 (B), and 3 (C) show the case where the frequency (repetition speed) of the pulse P of the laser light is 1 kHz, 100 kHz, and 1 MHz, respectively. In FIGS. 3 (A), 3 (B) and 3 (C), the horizontal axis indicates time and the vertical line indicates the irradiation timing of the pulse P. The intervals of the pulses P in FIGS. 3 (A), 3 (B) and 3 (C) are 1 ms (1 millisecond), 10 μs (10 microseconds) and 1 μs (1 microsecond), respectively.

If the flight time FT is longer than the pulse P interval, the mass spectra overlap. Therefore, it is preferable to adjust the flight time FT according to the pulse P interval and make the flight time FT sufficiently shorter than the pulse P interval. .. The ratio of flight time FT to pulse P interval is preferably 0.8 or less, more preferably 0.2 or less.

Returning to FIG. 1, when an ion reaches the detection unit 28, the detection unit 28 outputs a pulse signal. This pulse signal is input to the time-correlated single ion counting unit 33 shown in FIG. 1 as a stop signal 29. The signal processing unit 30 has a time-correlated single ion counting unit 33 and a multi-channel analyzer 34. The signal processing unit 30 is configured so that the start signal 15 and the stop signal 29 are input to the time-correlated single ion counting unit 33.

The time-correlation single-ion counting unit 33 may include an amplifier that amplifies the stop signal 29, a constant fraction discriminator (CFD) for improving the time resolution, a time-voltage converter (TAC), and the like. Time-voltage converters (TACs) are useful in that they have high time resolution and low cost. The time-correlation single-ion counting unit 33 is not limited to such a configuration, and may include a time digital converter (TDC) that directly measures the time interval of the pulse instead of the time-voltage converter (TAC).

The time-correlation single ion counting unit 33 measures the flight time of ions from the time interval between the start signal 15 and the stop signal 29. The measured flight time is integrated as a digital signal by the multi-channel analyzer 34, and a histogram of the flight time is created. A mass spectrum can be obtained based on this histogram. The mass spectrum is displayed on the display unit 50 of a personal computer or the like connected to the multi-channel analyzer 34.

The time-correlation single ion counting unit 33 is configured to integrate the flight time obtained by using the laser light from the light emitting unit 10 as the start signal 15 and the detection signal from the detection unit 28 as the stop signal 29 as a digital signal. .. The flight time is measured repeatedly, for example, 1 to 1 million times, the flight time is integrated, and a histogram of the flight time is created. A mass spectrum can be obtained based on this histogram. Since the time-correlated single ion counting unit 33 integrates only the flight time without integrating noise, the S / N ratio can be increased. The analog signal of the detection unit 28 may be integrated and measured without being converted into a digital signal, but it is preferable to integrate the analog signal as a digital signal from the viewpoint of improving the time resolution and reducing noise.

As the time-correlated single ion counting unit 33, a commercially available time-correlated single photon counting device can be used. Examples of such an apparatus include a high-speed fluorescence lifetime measuring apparatus (FluoroCube) manufactured by HORIBA, Ltd.

The time-of-flight mass analyzer 100 includes a time-correlated single ion counting unit 33 that measures the time interval between the laser beam and the detection signal of the ion detected by the detection unit 28. Therefore, it is possible to reduce noise, improve the S / N ratio, and reduce the lower limit of detection of the component to be measured in the sample.

The time-of-flight mass spectrometer 100 includes a light emitting unit 10 that irradiates a sample with laser light. Since the femtosecond laser beam or the picosecond laser beam has a small pulse width and can increase the repetition rate, it is possible to improve the time resolution and increase the number of times the flight time is integrated. Since the time-correlation single-ion counting unit 33 is capable of high-speed data processing, it is possible to integrate the flight time without counting down the signals even if the repetition speed of the laser beam pulse is increased. That is, since the flight time type mass analyzer 100 includes a light emitting unit 10 that irradiates a femtosecond laser beam or a picosecond laser beam and a time-correlated single ion counting unit 33, it is excellent in both mass resolution and analysis sensitivity.

The time-of-flight mass spectrometer of the present embodiment is extremely effective for analyzing an organic compound having a molecular weight of, for example, 100 or more. Even when the concentration of the organic compound is low, it can be analyzed with high accuracy. For example, it is useful for microanalysis of toxic substances such as dioxins and carcinogens such as polychlorinated biphenyls, pesticides, and nitroaromatic compounds.

Although the embodiment of the time-of-flight mass spectrometer of the present invention has been described above, the present invention is not limited to the above-described embodiment. For example, the time-of-flight mass spectrometer may be provided with a gas chromatograph on the upstream side of the main body 20. By introducing the components separated by the gas chromatograph from the introduction section 21 to the main body section 20, even if the sample contains a component other than the component to be measured or a sample containing a plurality of components to be measured, these can be distinguished. Can be analyzed. Further, in the signal processing unit 30, the time-correlated single ion counting unit 33 and the multi-channel analyzer 34 may be integrated instead of having a separate hardware configuration. Further, the signal processing unit 30 may include a display unit 50.

One embodiment of the mass spectrometry method of the present invention uses the time-of-flight mass spectrometer 100 described above. In the mass analysis method of the present embodiment, the laser irradiation step of irradiating the measurement target component with the laser light 12 from the light emitting unit 10 to generate ions in the ionization region 24, and the detection unit 28 detects the ions flying in the flight region 27. Data for measuring the flight time of ions by a time-correlated single ion counting method in which the detection step for detection and the detection signal of the laser beam and the ion detected by the detection unit 28 are used as a start signal 15 and a stop signal 29, respectively. Has a processing step. Each step can be performed based on the description of the time-of-flight mass spectrometer 100 described above. The measurement of the flight time of ions by the time-correlated single-ion counting method can be performed by the time-correlated single-ion counting unit 33.

The mass spectrometric method may include a separation step of separating a sample into a plurality of samples in a gas chromatograph. In this case, in the laser irradiation step, one or more separated components to be measured can be irradiated with laser light to generate ions. Therefore, even a sample containing a plurality of components can be analyzed separately.

The mass spectrometric method of the present invention is not limited to the above-described embodiment. The above-mentioned mass spectrometry method may be performed using a time-of-flight mass spectrometer having a device configuration different from that of the time-of-flight mass spectrometer 100. For example, a time-of-flight mass spectrometer having a signal processing unit in which the time-correlated single-ion counting unit 33 and the multi-channel analyzer 34 are integrated instead of having a separate hardware configuration may be used.

The contents of the present invention will be described in more detail with reference to Examples and Reference Examples , but the present invention is not limited to the following examples.

( Reference example 1)
Using a time-of-flight mass spectrometer having the same configuration as in FIGS. 1 and 2, pinene (molecular weight = 136), which is an allergic substance represented by the following formula, was analyzed. First, a sample containing pinene, which is a component to be measured (a sample obtained by evaporating pinene in a sample bottle and diluting it with nitrogen gas) was prepared.

The distance L between the repeater electrode 22 and the detection unit 28 in the main body 20 of the time-of-flight mass spectrometer used here was about 42 cm. The potential difference between the repeller electrode 22 and the grid electrode 26a was set to 1780V. The femtosecond laser light from the titanium sapphire laser was changed to a wavelength of 267 nm in the wavelength conversion unit, and then the sample was irradiated in the ionization region 24. The pulse width of the irradiated femtosecond laser beam was 100 fs, the repetition rate was 1 kHz, and the energy per pulse was 0.142 μJ. The integrated time of the flight time data was set to 205 seconds. The obtained mass spectrum was as shown in FIG. 4 (A).

FIG. 4B is a diagram showing the results of theoretical calculation of the absorption spectrum of pinene. From FIG. 4B, it can be seen that there is no absorption band of pinene near the wavelength (267 nm) of the femtosecond laser beam used for the measurement. As described above, even though the wavelength of the femtosecond laser light is not included in the absorption band, as shown in FIG. 4A, even if the energy per pulse of the femtosecond laser light is low, it is sufficient. It was confirmed that pinen could be measured.

( Reference example 2)
A sample with a different concentration of pinen (a sample in which pinen was adjusted to about 6.4 volumes by volume ppm with nitrogen gas) was used, and the energy per pulse of the irradiated femtosecond laser light was set to 2.6 μJ. Same as Reference Example 1 except that different mass spectrometers of the same size were used, the potential difference between the repeater electrode 22 and the grid electrode 26a was set to 1980 V, and the integrated time of flight time data was set to 600 seconds. Mass spectrometry was performed. The obtained mass spectrum was as shown in FIG.

As shown in FIG. 5, it was confirmed that components on the order of ppm can also be measured. It is considered that the phenol and hexane detected in the mass spectrum are derived from the impurities contained in the plastic sampling bag used for preparing the sample. The vertical axis (Counts) of the graph of FIG. 5 is the number of measured ions. The ion counting probability is calculated by the following formula. When the energy per pulse of the laser beam becomes high, the counting probability becomes high and the signal tends to be saturated. However, in this reference example, the counting probability is sufficiently smaller than 0.1, and the signal intensity can be measured accurately. did it.
Counting probability = number of measured ions [times] / (measurement time [seconds] x laser beam repetition frequency [Hz])

( Reference example 3)
A plurality of samples in which the concentration of pinene was changed in the range of 1.7 to 6.4 volumes by volume were prepared, and mass spectrometry was performed in the same manner as in Reference Example 2. The obtained analysis results are plotted in FIG. FIG. 6 is a graph showing the relationship between the concentration of pinene and the counting probability of the peak corresponding to pinene. As shown in FIG. 6, a high correlation was observed between the two. From this result, it was confirmed that quantitative analysis can be performed with sufficiently high accuracy even on the order of ppm. The lower limit of detection was obtained from the height of noise in the mass spectrum obtained by mass spectrometry of each sample. That is, the concentration of pinene having an S / N ratio of 3 was determined. As a result, the lower limit of detection of pinene was 0.36 volume ppm. From this, it was confirmed that the lower limit of detection was sufficiently low and the analysis sensitivity was excellent.

(Example 4)
A sample containing eugenol (molecular weight = 164), which is an allergen, represented by the following formula (a sample in which eugenol was adjusted to 30 volumes ppt with nitrogen gas) was used, and between the repeater electrode 22 and the detection unit 28. The flight time type mass analyzer equipped with the main body 20 having a distance L of about 6.4 cm was used, the energy per pulse of the femtosecond laser beam was set to 34 μJ, and the integrated time was set to 1500 seconds. Except for this, mass analysis was performed in the same manner as in Reference Example 1. The obtained mass spectrum was as shown in FIG. 7 (A).

FIG. 7B is a result obtained by theoretical calculation of the absorption spectrum of eugenol. As shown in FIG. 7B, the wavelength (267 nm) of the femtosecond laser beam used for the measurement is contained in the absorption band of eugenol.

Based on the mass spectrum of FIG. 7A, the lower limit of detection, that is, the concentration of eugenol having an S / N ratio of 3 was determined and found to be 1.2 ppt. As described above, it was confirmed that the lower limit of detection was sufficiently low and the analysis sensitivity was sufficiently excellent.

According to the present disclosure, it is possible to provide a time-of-flight mass spectrometer that can be miniaturized, has a wide dynamic range of measurement, and has excellent mass resolution. Further, it is possible to provide an analysis method having a wide dynamic range of measurement and excellent mass resolution.

10 ... light emitting part, 12 ... laser light, 13 ... reflector, 15 ... start signal, 20 ... main body part, 21 ... introduction part, 22 ... repeater electrode, 24 ... ionization region, 26a, 26b ... grid electrode, 27 ... flight Region, 28 ... detection unit, 29 ... stop signal, 30 ... signal processing unit, 33 ... time correlation single ion counting unit, 34 ... multi-channel analyzer, 50 ... display unit.

Claims (7)

A light emitting part that emits a pulse of femtosecond laser light ,
A main body including an ionization region that ionizes the component to be measured by the pulse, a flight region in which the ions generated in the ionization region fly, and a detection unit that detects the ions that have flown in the flight region.
An introduction unit that introduces the component to be measured into the ionization region of the main body from the upstream side of the main body, and an introduction unit.
A time-correlated single ion counting unit for measuring the time interval between the pulse and the detection signal of the ion detected by the detection unit is provided.
In the main body portion, the distance between the repeater electrode provided on the upstream side of the flight region and the detection portion is 10 cm or less.
The repetition frequency of the pulse applied to the component to be measured in the ionization region is 1 kHz or more .
A time-of-flight mass spectrometer in which the potential difference between the repeater electrode that partitions the ionization region and the grid electrode functioning as a ground is 3 kV or more . The time-of-flight mass spectrometer according to claim 1, wherein a fiber laser is used as the light emitting unit. The time-of-flight mass spectrometer according to claim 1 or 2, wherein the flight time of the ion in the flight region is 30 μs or less. The time-of-flight mass spectrometer according to any one of claims 1 to 3, wherein the energy per pulse of the femtosecond laser beam is 100 μJ or less. The time-of-flight mass spectrometer according to any one of claims 1 to 4, wherein the introduction unit has a capillary. The time-of-flight mass spectrometer according to any one of claims 1 to 5, wherein a gas chromatograph is provided on the upstream side of the introduction portion. Time-of-flight mass spectrometry including a main body having an ionization region for ionizing a component to be measured, a flight region in which ions generated in the ionization region fly, and a detection unit for detecting the ions flying in the flight region. It is a mass spectrometry method using an instrument.
A step of introducing a component to be measured into the ionized region of the main body from the upstream side of the main body, and a step of introducing the component to be measured.
The step of irradiating the measurement target component with a pulse of femtosecond laser light to ionize the measurement target component, and
The process of detecting the ions that have flown in the flight area with the detection unit, and
It comprises a step of measuring the time interval between the pulse and the detection signal of the ion detected by the detection unit by using the time-correlation single ion counting method.
In the main body portion, the distance between the repeater electrode provided on the upstream side of the flight region and the detection portion is 10 cm or less.
The repetition frequency of the pulse is 1 kHz or more, and
A mass spectrometric method in which the potential difference between the repeater electrode that partitions the ionization region and the grid electrode functioning as a ground is 3 kV or more .

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