KR101087079B1 - Multiplexed ms3 mass spectrometer - Google Patents

Abstract

The present invention relates to a three-step mass spectrometer composed of a linear potential reflectron, a PD cell, a quadratic potential reflectron, and using MALDI ionization for biological polymer analysis. . Molecular ions produced at the ionization source are separated by linear potential reflectrons and enter the PD cell, and molecular ions absorbed by the PD laser within the cell are decomposed inside or outside the PD cell (P), and PD After primary degradation in the cell, it may be degraded again outside the PD cell (C). That is, the C component is produced by the continuous reaction of m ₁ ⁺ → m ₂ ⁺ → m ₃ ⁺ , there are several C components depending on the intermediate (m ₂ ⁺ ), all m ₂ to make the same m ₃ ⁺ Three-step mass spectrometry spectra for ⁺ can be obtained. That is, in the present invention, by applying a voltage to the PD cell to change the kinetic energy of each C component and separating them using quadratic potential reflectrons, the mass of all m ₂ ⁺ can be accurately determined, and also all m ₂ ⁺ can be determined. By simultaneous detection, very good sensitivity three-step mass spectrometry can be obtained.

Mass, Analysis, Photolysis, Ions, Spectrum, Reflectron

Description

Three stage mass spectrometer {MULTIPLEXED MS3 MASS SPECTROMETER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass spectrometer, and more particularly, selects only the desired ions from ions generated from an ionization source and irradiates a photodissociation laser. The present invention relates to a three-stage mass spectrometry apparatus capable of detecting degradation products.

In general, two-step mass spectrometry is a useful technique for studying the structure and mechanism of biomolecule ions. This method selects molecular ions with the first analyzer and analyzes the generated ions produced by the decomposition reaction with the second analyzer. In addition, three-step mass spectrometry is widely used to select ions generated from one decomposition reaction and to analyze ions produced by decomposition reaction again.

As one of the two-stage mass spectrometry, multi-stage mass spectrometry can be easily performed in a two-stage mass spectrometer using a trapping-type spectrometer, while a spatially separated form of time of flight mass (TOFMS) In a spectrometer, multi-step mass spectrometry becomes complex and expensive.

In addition, sensitivity is dramatically reduced when using multi-step mass spectrometry. Accordingly, four-ier transform (FT) -mass (FT), which can be repeatedly detected, is most useful as a multi-step method. In this case, multi-step mass spectrometry through matrix assisted laser desorption ionization (MALDI) -TOF may be possible, but the sensitivity is very low to perform multi-step mass spectrometry in the form of TOF-TOF.

On the other hand, in MALDI-tandem TOF using a photolysis laser, the generated fragment ions were analyzed by linear plus quadratic potential reflectron (LPQ), and three kinds of components were observed for each fragment ion. That is, when the final chip ions are made in the cell (in-cell component, component I), the cells are made out of the post-cell component (component P), and the chip ions produced in the cell are decomposed again and again. This is the case where the cation is formed (consecutive component, C component). At this point, the spectrum of all the intermediates that make up a particular final chip ion is the 'constant granddaughter spectrum', which is a type of three-step mass spectrum.

However, the LPQ potential reflectron used in the existing mass spectrometer is an energy analyzer, which complements the separation before the reflectron, thereby improving the final mass fractionation performance, but it is disadvantageous for the temporal separation of the I, C, and P components, There was a problem that made the determination of mass difficult.

Accordingly, the present invention is to solve the above problems of the prior art, by using a quadratic potential reflectron (quadratic potential reflectron) to accurately detect the mass of the intermediate material appearing in the three-step mass spectrum It is intended to provide a step mass spectrometer.

The present invention described above is a three-stage mass spectrometer, comprising: an ionization source for delayed release of ions; A deflector for adjusting the direction of the ions passing through the tube, a linear potential reflecton reflecting the ions passing through the deflector, and positioned between the deflector and the linear potential reflectron and the ions under predetermined control An ion gate for selectively passing a light source, a PD (photolysis) cell for applying a potential to each ion generated when the ions reflected from the linear potential reflecton are photolyzed, and a laser to the ions passing through the PD cell PD laser for irradiating and a plurality of intermediate ions generated by decomposition by the laser And a quadrature potential reflecton for reflecting, and a detector for detecting, by mass, the intermediate ions reflected from the quadratic potential reflecton.

In the present invention, the I, C, and P components generated through PD cell experiments were analyzed by quadratic potential reflectron, and the detection time of the C component for each PD product was calculated to more accurately determine the mass of the intermediate product. There is an advantage to this. In addition, the present invention is useful in the study of decomposition reaction of peptide ions and has the advantage of finding out unstable ions that disappear rapidly due to very short lifespan.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the present invention. In the following description of the present invention, if it is determined that a detailed description of a known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intentions or customs of the user, the operator, and the like. Therefore, the definition should be based on the contents throughout this specification.

That is, in the present invention, by installing one more reflecton, the position where the PD laser is irradiated is positioned after the linear potential reflecton so that the isotope can be selectively photolyzed (monoisotope selection PD) more accurately. In addition, when the PD cell is placed at the position where the PD laser is irradiated and the PD laser is applied under high voltage and the PD laser is irradiated, the same PD product is found in the PD cell or in the post-cell component (P component). The difference in kinetic energy caused by the flight time depends on whether the final product (consecutive component (C component)) is produced outside the PD cell via the intermediate ion (m _i ⁺ ) in the PD cell. Afterwards, PD products having different flight times are separated and detected by quadratic potential reflectron to determine the mass of the intermediate product, thereby obtaining a three-step TOF mass spectrometry. These intermediates can be detected simultaneously for all PD products.

1 illustrates a schematic diagram of a three-stage mass spectrometer according to an embodiment of the present invention, wherein the three-stage mass spectrometer according to the present invention uses a MALDI ion source 100 using a delayed extraction (DE) mode. And a linear potential reflectron 108, a high voltage PD cell 110, a PD laser 112, a quadratic potential reflectron 114, a detector (116) and the like.

The distance between the exit of the MALDI ionization source 100 and the entrance of the linear potential reflecton 108 is 1250 mm. Two ion gates 106 are provided at a distance of 70 mm at the inlet and 52 mm at the outlet of the linear potential reflecton 108. A stainless steel tube 102 is installed between the MALDI ionization source 100 and the linear potential reflector 108 to block the influence of a field that impedes the direction of travel of the ions, and the ions move in the desired direction. A deflector 104 for controlling the direction of movement of the ions so as to be ions is provided at a position 103 mm away from the inlet and the outlet of the linear potential reflecton 108.

Hereinafter, the operation of each component of the three-stage mass spectrometer of the present invention will be described in detail with reference to FIG. 1.

First, the linear potential reflecton 108 is 210 mm long so that the second time focusing point is 370 mm from the exit. It is installed for the high resolution of molecular ion selection rather than being used as the second analyzer in a two-stage mass spectrometer.

The PD cell 110 is composed of four circular electrodes, E1-E4, and the distance from the center of the PD cell 110 to the linear potential reflecton 108 is 170 mm. The outer two electrodes E1 and E4 of the plurality of circular electrodes in the PD cell 110 are grounded, and the two inner electrodes E2 and E3 are connected to have the same voltage. The distances of E1-E2, E2-E3 and E3-E4 are 9.5, 11.5 and 9.5 mm, respectively. PD cell 110 is a quadratic potential reflectron 114 tilted 3 degrees to allow ions to proceed as well as possible.

The PD laser 112 is irradiated between E2 and E3 in the PD cell 110. At this time, E1, E2, and E4 are installed with a nickel network having a 95% transmittance, E3 is installed with a nickel network having a 90% transmittance, which is ionized by the PD laser 112, the residual gas is ionized spectral pollution To prevent giving.

The quadratic potential reflectron 114 is composed of 47 circular electrodes and is formed with a total length of 458 mm and is installed at the second time focusing position. At this time, the high voltage 27kV is applied to the 44th electrode, and the voltage distribution is performed so that quadratic potential is formed inside the reflectron 114.

In addition, the 44th electrode of the circular electrode of the quadratic potential reflectron 114 is provided with a nickel network showing 98% transmittance, the 45th, 46th, 47th electrode is subjected to a voltage of 26, 21, 10kV, respectively, 45 The first electrode is provided with a nickel network showing 95% transmittance. This is to reduce the influence of the field and to prevent the ions generated during the process after the ion generation hit the bottom of the quadratic potential reflecton 114 to the contamination of the spectrum.

In the conventional analyzer, the PD laser was irradiated to the first time focusing position, and only the selected ions hit the PD laser by synchronizing the molecular ion pulse generated by the MALDI laser irradiated on the sample plate with the pulse of the PD laser. However, according to the MALDI experimental conditions, the time that the molecular ions arrive at this position is slightly changed, which makes it difficult to accurately investigate the PD laser.

Accordingly, in the present invention, the PD is further attempted after passing the linear potential reflecton 108 by additionally installing the linear potential reflecton 108. Accordingly, even if the PD cell 110 is installed 200mm away from the second time focusing position, the arrival time of the molecular ions is almost constant, and PD can be selected by selecting only one specific isotope of the molecular ion with high fractionation performance. It was.

Hereinafter, a three-step mass spectrometry operation in the three-step mass spectrometer as described above will be described.

Operation: A nitrogen laser (VSL-337ND-S, Laser Science, Franklin, Mass., USA) was used as the laser of the MALDI ionization source (100). The two ion gates 106 are turned off when obtaining the MALDI-TOF spectrum and turned on for the PD experiment and PD cell 110 experiment. PD laser 112 (193 nm, PSX-100, MPB Communication Inc., Montreal, Quebec, Canada) was synchronized with the lowest mass-to-charge ratio (m / z) of isotopes or desired A peak ions.

Samples: Peptide samples YPFVEPI and RLLAPITAY were purchased from Peptron and α-cyano-4-hydroxycinnamic acid (CHCA) was purchased from Sigma (St. Louis, MO, USA). Matrix solution was prepared by mixing acetonitrile (acetonitrile) and 0.1% trifluoroacetic acid (trifluoroacetic acid) with a peptide solution. The final concentration of the peptide was about 10 pmol / μL. 1 μL of this solution is loaded onto a sample plate of MALDI ionization source 100.

Mass determination of three-step mass spectra

After irradiation of the laser from the PD laser 112, the velocity of the ions in the circular electrodes E2-E3 in the PD cell 110 has the same value regardless of decomposition. Therefore, the section affecting the flight time of the ions is the section E3-E4 (ℓ ₃ ), which is affected by the high voltage applied to the PD cell 110, and the section from E4 to the entrance of the quadratic potential reflecton 114. (d ₁ ) and the distance d ₂ from the quadratic potential reflectron 114 exit to the detector 116. The mass of the intermediate can be determined in these sections with different flight times for the I, C and P component ions. The flight time of the ions is changed in one dimension according to the voltage applied to the PD cell 110. In addition, since the P component is not affected by the voltage of the PD cell 110, there is no change in time and can be found immediately.

Hereinafter, the flight time calculation of the ions decomposed in the PD cell 110 will be described.

** Flight time of P component ions **

Let K to _0, the kinetic energy of the velocity before entering ion (m ⁺ ₁₎ cells in PD _{(110) v 0 (= (} 2K 0 / m 1) 1/2), then m ₁ ⁺ a voltage V is taken When entering the PD cell 110, the speed v _I is as shown in Equation 1 below.

v _I = v ₀ {1- (eV / K ₀ )} ^1/2

Then, m ₁ ⁺ becomes the equivalent velocity movement in the E3-E4 section in the PD cell 110 and becomes the velocity v ₀ at E4, and m ₁ ⁺ in the section from E4 to the inlet of the quadratic potential reflecton 114. When P is decomposed into other isotopes (m ₂ ⁺ ), P component ions of m ₂ ⁺ with a rate of v ₀ are produced. The flight time t _P of these P component ions is shown in Equation 2 below.

t _P = 2ℓ ₃ / (v ₀ + v _I ) + (d ₁ + d ₂ ) / v ₀

In this case, if the new parameters C ₁ -C ₃ are defined as in Equation 3 below,

C ₁ = (d ₁ + d ₂ ) / (2K ₀ / m ₁ ) ^1/2 ,

C ₂ = 2ℓ ₃ / (d ₁ + d ₂ ),

C ₃ = eV / K ₀

Equation 2 above is changed as shown in Equation 4 below.

t _P = C ₁ [1 + C ₂ / {1+ (1-C ₃ ) ^1/2 }]

** Flight time of C component ions **

C component ions are ions having a velocity of v _I and a kinetic energy of (m _i / m ₁ ) (K ₀ -eV) at the circular electrode E3 in the PD cell 110. Since m _i ⁺ performs the equivalent acceleration movement in the E3-E4 section, the kinetic energy in E4 becomes (m _i / m ₁ ) (K ₀ -eV) + eV, where, at E4, the quadratic potential reflecton (114) The velocity v _C ⁱ to the inlet of) is given by Equation 5 below.

v _C ⁱ = {(2K ₀ / m ₁ ) + 2eV (m ₁ -m _i ) / m ₁ m _i } ^1/2 (5)

At this time, the flight time (t _C ⁱ ) of the C component ions in the entire section affecting the overall flight time is as shown in Equation 6 below.

t _C ⁱ = 2ℓ ₃ / (v _I + v _C ⁱ ) + (d ₁ + d ₂ ) / v _C ⁱ

= C ₁ [{1 + C ₃ (m ₁ -m _i ) / m _i } ^-1/2 + C ₂ / {(1-C ₃ ) ^1/2 + (1 + C ₃ (m ₁ -m _i ) / m _i ) ^1/2 }]

At this time, if m _i is replaced with m ₂ in Equation 6 above, it is obtained as shown in Equation 7 below as a flight time t _I for I component ions.

t _I = C ₁ [{1 + C ₃ (m ₁ -m ₂ ) / m ₂ } ^-1/2 + C ₂ / {(1-C ₃ ) ^1/2 + (1 + C ₃ (m _1- m ₂ ) / m ₂ ) ^1/2 }]

** Determine the mass of m _i ⁺ **

The time difference between the C and P component ions, Δt ⁱ = t _p ⁱ -t _c ^i, can be obtained using Equations 4 and 6 and the result is shown in Equation 8 below. Same as

Δt ⁱ / C ₁ = F ⁱ

= 1 + C ₂ / {1+ (1-C ₃ ) ^1/2 }

_{- {1 + C 3 (m} 1 -m i) / mi} -1/2 - C 2 / [(1-C 3) 1/2 + {1 + C 3 (m 1 -m i) / m i } ^1/2 ]

Summarizing Equation 8 above with respect to m _i , we get the same value as in Equation 9 below.

m _i = m ₁ / {1+ (X ² -1) / C ₃ }

In this case, X in Equation 9 is defined as in Equation 10 below.

X = [1 + C ₂ -AB + {(1 + C ₂ -AB) ² + 4AB} ^1/2 ] / 2A

In addition, A and B are defined as shown in Equation 11 below.

A = 1 + C ₂ / (1 + B)-Δt ⁱ / C ₁

B = (1-C ₃ ) ^1/2 .

-PD experiment and PD cell experiment using laser of 193nm wavelength

The mass fractionation performance of the mass spectrometer of the present invention is approximately 5000. It is less than 10000-13000 obtained from a previous machine because it was made for the PD cell 110 experiment. The fractionation performance at the position where the PD laser 112 is irradiated is about 2000 and the peak width (FWHM, full width at half maximum) of m / z 1000 is about 8 ns. In addition, selective irradiation of only the A peak is possible with a PD laser 112 of 193 nm wavelength having a pulse width of 5 ns with a time of about 20 ns apart from an ion of m / z 1001. In particular, the flight time of the peptide ions at this position is very constant and the change is measured to be 0.5ns or less. Therefore, it was confirmed that only the A peak selectively fits the PD laser 112, but the A + 1 peak does not match.

FIG. 2 shows a 193 nm PD spectrum of [YPFVEPI + H] ⁺ (m / z 864.45) obtained by applying voltages 0 kV, 3 kV, and 5 kV to the PD cell 110.

As shown in FIG. 2, it can be seen that more peaks appear in the voltage spectrum than in the voltage spectrum. When the spectrum is obtained by applying a voltage to the PD cell 110, the flying time of molecular ions increases little by little depending on the applied voltage. By correcting the flight time of these molecular ions, the P component ions of each m ₂ ⁺ ion can be easily identified because the difference in flight time from the molecular ions is constant regardless of the cell voltage. It is expected to appear in the position with the most time difference. To confirm this, m / z values of each ion were calculated by Equation 8 and Equation 9 using the experimental values obtained from the voltage 5kV-on spectrum and m ₁ = m ₂ . In particular, each m ₂ ⁺ F ([Equation 8]), the value of the ion are calculated parameter determined by the voltage and the device design values used for the test parameters C _2, using the C ₃ value, C ₂ values and the C ₃ value Were 0.10123 and 0.25641, respectively.

In this case, Δt and F are linear functions having a value of correlation coefficient 0.9994 as shown in FIG. 3. The slope value of this linear function, 2.8449, was taken as the C ₁ value.

Then, using the above parameters C ₁ , C ₂ , and C ₃ , the mass of each m ₂ ⁺ is calculated using Equation 9, and the mass is determined by small error in the small mass region and in the large mass region. , The largest error in the middle mass region was obtained. That is, it turned out that the largest mass error of 6.6 Da is shown with respect to m <_2> ⁺ of m / z 473.2.

In general, it is well known that organic mass spectrometry rarely causes loss of 4-14 Da heavy molecules. This is unlikely to occur with peptide ions. Therefore, finding the I component of each m ₂ ⁺ ion is considered to be no problem. In addition, the expectation that the component I ions will be located farthest from the P component ions was found to be correct.

In the present invention, it was calculated whether the mass of m _i ⁺ ions which determines the detection time of C component ions can be determined. That is, the method of determining the mass of the calculated component I ions is improved to calculate the ratio Δt / F for each m _i ⁺ ion from the first function of Δt and F of the component I ions in the 5 kV-on spectrum obtained in FIG. 3. Take the C ₁ value. The mass of m _i ⁺ ions is determined using the C ₁ values and the C ₂ and C ₃ values used to determine the I component ions.

4 shows the mass error of m _i ⁺ ions for all m ₂ ⁺ ions. In the present invention, the mass error was able to determine the mass of m _i ⁺ ion with the value of 3Da, and the largest mass error was -4.3 Da.

From the peak width (FWHM) of the C component ions of each m ₂ ⁺ in the 5 kV-on spectrum, the mass discrimination ability was about 17 Da for 864.5 ⁺ → 636.3 ⁺ → 507.3 ⁺ and 7 Da for 864.5 ⁺ → 227.1 ⁺ → 70.1 ⁺ .

Looking at the 5kV-on spectrum in Figure 2, the peak and peak overlap occurs, which occurs less in the 3kV-on spectrum. We can see the longer quad reotik potential reflective torch or if using a low voltage, without an overlap phenomenon of the other peaks in the next m ⁺ _2, such as is thrown I, C, P ion component.

As described above, in the present invention, in a MALDI-tandem TOF using a PD laser, a plurality of decomposed ions having different kinetic energies are formed by decomposing ions with a PD laser while installing a PD cell and applying a high voltage thereto. Can create them. In this case, the ions of each of the I, C, and P components generated by the PD laser have different kinetic energy even though they are the same PD product, and the time to reach the quadratic potential reflecton inlet after the PD laser irradiation is different. That is, component I arrives first and components C and P arrive next.

In addition, the quadratic potential reflector used in the present invention has the same characteristics of staying in the reflectron if the mass is the same even though the kinetic energy is different. Therefore, the I, C, and P components generated through PD cell experiments are detected while maintaining the temporal separation from the PD laser irradiation to the quadratic potential reflecton, and the C component is calculated by calculating the time difference for each of these components. The mass of intermediate (m ₂ ⁺ ) ions can be determined from the flight time of the ions. In this way, the mass of intermediate ions can be effectively determined.

In addition, in the three-step mass spectrometry, an ion activation step is generally used twice, but in the present invention, a continuous reaction caused by one step of ion activation is observed. It also detects all intermediates (m _i ⁺ ) of all the resulting ions simultaneously, resulting in very high sensitivity.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. That is, in the present invention, for example, the decomposition of ions using a PD laser in a PD cell has been described, but neutral gases such as argon (Ar), neon (Ne), and xenon (Xe) that decompose ions in the PD cell are described. It is also possible by inflow. Accordingly, the scope of the invention should not be limited by the described embodiments but should be defined by the appended claims.

1 is a schematic diagram of a three-step mass spectrometer according to an embodiment of the present invention,

2 is a diagram illustrating a 193 nm PD spectrum when PD cell voltages of [YPFVEPI + H] ⁺ (m / z 864.45) are 0 kV, 3 kV, and 5 kV according to an embodiment of the present invention;

3 is a graph showing the relationship between Δt and F for the final generated ions when the PD cell voltage is 5 kV in FIG.

4 is a table of mass error for intermediate generated ions of the final produced ions of [YPFVEPI + H] ⁺ (m / z 864.45) according to an embodiment of the present invention.

<Brief description of the major symbols in the drawings>

100 ionization source 102 tube

104: reflector 106: ion gate

108: linear potential reflecton 110: PD cell

112: PD laser 114: quadratic potential reflectron

116: detector

Claims (16)

As a three-step mass spectrometer, An ionization source for delayed release of ions, A tube through which the ions emitted from the ionization source pass and block the influence of an ambient electric field on the direction of travel of the ions, A deflector for adjusting the direction of the ions passing through the tube, A linear potential reflecton reflecting the ions passing through the deflector, An ion gate positioned between the deflector and the linear potential reflecton to selectively pass the ions under predetermined control; A PD (photolysis) cell for applying a potential to each ion generated when the ions reflected from the linear potential reflecton are photolyzed; A PD laser for irradiating a laser to the ions passing through the PD cell, A quadratic potential reflectron reflecting a plurality of intermediate ions generated by decomposition by the laser according to mass; A detector for detecting the intermediate ions by mass reflected from the quadratic potential reflectron, The PD cell is formed of a plurality of circular electrodes positioned between the linear potential reflector and the quadratic potential reflectron, and is formed of a second electrode to which the same voltage is applied between the first electrodes connected to the ground. Three-step mass spectrometer characterized by. delete The method of claim 1, The PD laser is a three-step mass spectrometer, characterized in that to generate a plurality of intermediate ions ions passing through the PD cell by irradiating the laser between the second electrode in the PD cell. The method of claim 3, wherein The PD cell is a three-step mass spectrometer, characterized in that the kinetic energy of the intermediate ions generated inside, middle or outside of the PD cell is set differently according to the voltage applied to the second electrode. The method of claim 4, wherein The intermediate ion is a three-step mass spectrometer, characterized in that reached at different times with the quadratic potential reflectron according to the different kinetic energy. The method of claim 5, The quadratic potential reflectron is a three-step mass spectrometry characterized by reflecting a corresponding mass of each intermediate ion according to the order in which each intermediate ion is reached for a plurality of intermediate ions generated through the PD cell. Device. The method of claim 1, The first electrode is a three-step mass spectrometer, characterized in that the upper and lower outer two electrodes of the circular electrode. The method of claim 1, The second electrode is a three-step mass spectrometer, characterized in that the two electrodes of the inside of the circular electrode. The method of claim 1, Each circular electrode of the PD cell is a three-step mass spectrometer, characterized in that the nickel network is covered. The method of claim 1, And a field free section having a predetermined interval or more between the PD cell and the quadratic potential reflectron. The method of claim 1, The quadratic potential reflectron is a three-step mass spectrometer, characterized in that consisting of 47 circular electrodes. The method of claim 11, And a nickel network is coated on the first electrode, the 44th electrode, and the 45th electrode of the quadratic potential reflectron. The method of claim 1, The ionization source is a three-stage mass spectrometer, characterized in that the MALDI ionization source. The method of claim 3, wherein The intermediate ion is a three-step mass spectrometer, characterized in that the isotope of the ion. As a mass spectrometer, An ionization source for delayed release of ions, A tube through which the ions emitted from the ionization source pass and block the influence of an ambient electric field on the direction of travel of the ions, A deflector for adjusting the direction of the ions passing through the tube, A linear potential reflecton reflecting the ions passing through the deflector, An ion gate positioned between the deflector and the linear potential reflecton to selectively pass the ions under predetermined control; A PD (photolysis) cell for applying a potential to each ion generated when the ions reflected from the linear potential reflecton are photolyzed; A neutral gas located in the PD cell and colliding with the ions passing through the PD cell, A quadratic potential reflectron reflecting a plurality of intermediate ions decomposed and generated by the neutral gas according to mass; A detector for detecting the intermediate ions by mass reflected from the quadratic potential reflectron, The PD cell is formed of a plurality of circular electrodes positioned between the linear potential reflector and the quadratic potential reflectron, and is formed of a second electrode to which the same voltage is applied between the first electrodes connected to the ground. Characterized Three-step mass spectrometer comprising a. The method of claim 15, The neutral gas, argon (Ar), neon (Ne) or xenon (Xe) comprises a three-step mass spectrometer.

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