JP2008008867A - Mass spectrometry, mass spectrometry program, and icp-ms device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately determine existence ratio of a predetermined element in a sample. <P>SOLUTION: In the mass spectrometry using an LA-ICP-MS device 1, a predetermined number of one-cycle detections for detecting the number of counts per predetermined period for each element is performed (step S5). The concentration of a predetermined element is calculated every one-cycle detection based on this number of counts (step S6). Then, the average of concentration calculated every one-cycle detection is calculated (step S9). Thus, by calculating the existence ratio every time a detection strength is acquired without using the concept of integration for a certain period or more, the existence ratio of the predetermined element can be accurately determined even if many samples are suddenly ablated and the existence ratio of each element in a dust material or a gasified material generated by sudden ablation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a mass spectrometry method for performing mass spectrometry on a sample, a mass spectrometry program, and an LA-ICP-MS apparatus.

As a conventional mass spectrometry method applied to an ICP-MS apparatus, a sample using a fine powder or gasified product generated by laser ablation of a sample containing a plurality of elements having different mass numbers from each other is used. What performs mass spectrometry is known (for example, refer patent document 1).
JP 2004-347473 A

  By the way, in the mass spectrometry method as described above, for each of a plurality of elements having different mass numbers, the detection intensity (for example, the count number) per predetermined time is integrated over a predetermined time or more, and the integration is performed. Based on the value, for example, the abundance ratio of a predetermined element is calculated by a standardized semi-quantitative method. However, in such a mass spectrometry method, when the sample is suddenly ablated in large quantities and the abundance of each element in the fine powder or gasified product caused by the sudden ablation is shifted, This greatly affects the integrated value of the detected intensity per predetermined time, and thus the accuracy of calculating the abundance ratio of the predetermined element is lowered.

  Then, this invention makes it a subject to provide the mass spectrometry method, mass spectrometry program, and ICP-MS apparatus which can obtain | require the abundance ratio of a predetermined element with high precision.

  In order to solve the above problems, a mass spectrometry method according to the present invention uses a fine powder or gasified product generated by performing laser ablation on a sample containing a plurality of elements having different mass numbers. A mass spectrometry method for performing mass spectrometry on the basis of the detection intensity, the step of performing one cycle detection for detecting a detection intensity per predetermined time for each element, the step of performing one cycle detection a predetermined number of times, and the detection intensity The method includes a step of calculating an abundance ratio of a predetermined element for each cycle detection, and a step of calculating an average value of the abundance ratios calculated for each cycle detection.

  In addition, the mass spectrometry program according to the present invention is an ICP that performs mass spectrometry on a sample using a fine powder or gasified product generated by performing laser ablation on a sample containing a plurality of elements having different mass numbers. -1 cycle detection based on the detection intensity based on the detection intensity, the process of performing the 1 cycle detection for detecting the detection intensity per predetermined time for each element of the computer of the MS device A process of calculating the abundance ratio of a predetermined element every time and a process of calculating an average value of abundance ratios calculated for each cycle detection are performed.

  In addition, the ICP-MS apparatus according to the present invention performs mass analysis on a sample using a fine powder or gasified product generated by performing laser ablation on a sample containing a plurality of elements having different mass numbers. An ICP-MS apparatus that performs one-cycle detection for detecting a detection intensity per predetermined time for each element, performs a predetermined number of cycles, and performs predetermined detection for each cycle based on the detection intensity. The present invention is characterized in that an arithmetic unit that calculates an abundance ratio of the elements and calculates an average value of the abundance ratios calculated for each cycle detection is provided.

  Thus, according to the present invention, one cycle detection for detecting the detection intensity per predetermined time for each element is performed a predetermined number of times, and based on this detection intensity, the predetermined element is detected for each cycle detection. The existence ratio is calculated. Then, the average value of the existence ratios calculated for each cycle detection is calculated. Thus, by calculating the existence ratio each time the detection intensity is acquired without using the concept of integrating over a certain time or more, even if the sample is suddenly ablated abundantly, and by sudden ablation Even if the abundance ratio of each element in the generated fine powder or gasified product is shifted, the abundance ratio of the predetermined element can be obtained with high accuracy.

Here, the detection intensity is the number of counts, and when one cycle detection is performed m times, the abundance ratio X _i of the predetermined element in the i-th one-cycle detection is:
X _i = A _x k _x / (A ₁ k ₁ +... + A _n k _n )
X _i : Presence ratio of predetermined element (i = 1,..., M)
A _x: counting a predetermined number of elements (i.e., _{A x} is any one of _A 1 to A _n)
k _x: sensitivity coefficient of a given element (i.e., _{k x} is any one of _k 1 to k _n)
A ₁ ,..., A _n : Count numbers of elements k ₁ ,..., K _n : Calculated by the sensitivity coefficients of the elements, and the average value X _ave of the abundance ratio is
X _ave = (X ₁ +... + X _m ) / m
Preferably, it is calculated by

  Thus, when calculating the abundance ratio of a predetermined element for each cycle detection, the abundance ratio of the predetermined element can be determined with higher accuracy by using a so-called standardized semi-quantitative method. The numbers m and n are integers of 2 or more.

  In addition, in the step of calculating the average value of the existence ratio, the existence ratio excluding the one existence ratio when the one existence ratio is out of the predetermined range among the existence ratios calculated for each cycle detection. It is preferable to calculate an average value of the ratios. Thereby, for example, even when the sample is suddenly ablated in large quantities and the abundance of each element in the fine powder or gasified product caused by the sudden ablation is shifted, the influence of the sudden ablation is affected. The existence ratio of the predetermined element can be determined with higher accuracy. Note that, for example, 3σ, 2σ, σ, or the like is preferably used when determining whether or not one existence ratio is out of a predetermined range.

  According to the present invention, the abundance ratio of a predetermined element in a sample can be obtained with high accuracy.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, an LA-ICP-MS apparatus 1 includes an LA apparatus 2 that performs laser ablation on a sample S containing a plurality of elements having different mass numbers, and a fine powder generated by laser ablation on the sample S. The ionization of the product or the gasified product, and for each mass / charge ratio m / z value (m: mass number, z: charge number), that is, for each element having a different mass number, the count number per predetermined time (detection intensity; Hereinafter, the ICP-MS apparatus 3 that simply detects “count number”) is provided.

  The LA device 2 has a sample chamber 4, a laser unit 5, and a CCD camera 6. A sample stage 8 on which the sample S is placed is provided in the sample chamber 4.

  In the LA device 2, the laser light emitted from the laser unit 5 at a predetermined wavelength is reflected by the mirrors 10 and 11 and enters the wavelength conversion element 12. The laser light whose wavelength has been reduced by half by the wavelength conversion element 12 is further reduced in wavelength by the wavelength conversion element 13, reflected by the mirrors 14, 15, 16, passed through the lens 17, reflected by the beam splitter 18, and sample. The sample S in the chamber 4 is irradiated.

  The laser unit 5 is equipped with, for example, an Nd-YAG laser with a wavelength of 1064 nm. For example, the laser light emitted from the laser unit 5 is converted from the wavelength 1064 nm to the wavelength 532 nm (second harmonic) by the wavelength conversion element 12, and further, from the wavelength 532 nm to the wavelength 266 nm (third order) by the wavelength conversion element 13. Harmonics). Thus, by setting the laser beam to a short wavelength, the energy of the laser beam is increased, and laser ablation can be performed on more substances.

  The CCD camera 6 can observe the sample S arranged in the sample chamber 4 via the beam splitter 18. The CCD camera 6 observes the irradiation position of the laser beam on the surface of the sample S, for example.

  Connected to the sample chamber 4 are an introduction tube 19 for introducing a carrier gas such as argon gas into the sample chamber 4 and a lead-out tube 20 for extracting the carrier gas to the outside of the sample chamber 4. As the introduction pipe 19 and the lead-out pipe 20, for example, a Tygon tube or the like is used.

  The other end of the outlet tube 20 whose one end is connected to the sample chamber 4 is connected to the rear end portion of the plasma torch 21 in the ICP-MS apparatus 3. As a result, the carrier gas introduced into the sample chamber 4 by the introduction pipe 19 goes to the ICP-MS apparatus 3 through the lead-out pipe 20 together with the sample S that has been pulverized or gasified by laser light irradiation. .

  The ICP-MS apparatus 3 includes a plasma torch 21 that generates plasma P for ionizing the sample S introduced together with the carrier gas from the introduction tube 22, and an ion introduction portion 23 in the vicinity of the tip of the plasma torch 21. It has the mass analysis part 24 which becomes.

  The plasma torch 21 has a triple tube structure, and a carrier gas is introduced from the introduction tube 22 and a plasma gas for forming plasma P is introduced from the tube 26 to cool the wall surface of the plasma torch 21. A coolant gas is introduced from the pipe 27. As the carrier gas, plasma gas, and coolant gas, for example, argon gas or the like is used.

  In the plasma torch 21, a gas having a flow rate of about 15 to 20 liters / minute is supplied as a whole, including the carrier gas, the plasma gas, and the coolant gas. As one form of each gas introduction amount, the carrier gas is about 1 liter / minute, the plasma gas is about 1 liter / minute, and the coolant gas is about 16 liter / minute.

  A high frequency coil 28 connected to a high frequency power source is provided on the tip side of the plasma torch 21. When a voltage is applied to the high-frequency coil 28, plasma P is formed inside the plasma torch 21 on the tip side.

  The ion introduction part 23 of the mass analysis part 24 has an introduction hole 29 that faces the tip of the plasma torch 21. Then, light and ions from the plasma P are introduced into the housing 30 through the introduction hole 29. The diameter of the introduction hole 29 is, for example, about 1 mm.

  The inside of the housing 30 is divided into two rooms with different degrees of vacuum, such that the ion introduction part 23 side is a low vacuum chamber and the opposite side is a high vacuum chamber by vacuum pumps 31 and 32. The mass analysis unit 24 separates light and ions from the plasma P by the ion lens 33 in the housing 30 and allows only the ions to pass through. The mass multipole unit 34 extracts only specific ions and detects the detector 35. It comes to detect in.

  By the way, the ICP-MS device 3 includes a calculation unit 40 that calculates the concentration (abundance ratio) of each element having a different mass number based on the detected count number. The calculation unit 40 is incorporated into the ICP-MS device 3 and configured integrally. In addition, the calculating part 40 may be comprised by the personal computer etc.

  As shown in FIG. 2, the calculation unit 40 includes a recording medium 50, and the recording medium 50 stores a mass analysis program 60 that causes the calculation unit 40 to execute various processes. The mass analysis program 60 includes a main module 61 that controls the operation of the entire program, a 1-cycle detection module 62 that realizes a process of performing one-cycle detection (details will be described later) a predetermined number of times, and each element for each cycle detection. A concentration calculation module 63 that realizes a process for calculating the concentration and an average value calculation module 64 that realizes a process for calculating the average value of the calculated concentration of each element are included.

  Next, a mass spectrometry method using the LA-ICP-MS apparatus 1 will be described.

  As shown in FIG. 3, first, a sample S is prepared and placed on the sample stage 8 in the sample chamber 4 (step S1). Then, the sample chamber 4 is sealed and the inside of the sample chamber 4 is purged with a carrier gas (step S2). Subsequently, in the LA apparatus 2, the sample S is irradiated with laser light, and laser ablation is performed on the sample S (step S3).

  Subsequently, the fine powder or gasified product generated by laser ablation on the sample S is introduced into the plasma torch 21 via the lead-out tube 20 and the introduction tube 22 by the carrier gas. Then, the fine powder or gasified product introduced into the plasma torch 21 is ionized (step S4).

  Subsequently, in the ICP-MS device 3, one cycle detection in which the count number is detected for each m / z value is performed (step S5), and one cycle detection is performed by the arithmetic unit 40 based on these count numbers. A standardized semi-quantitative method is performed for each element, and the concentration is calculated for each element having a different mass number in the sample S (step S6). Then, the calculation unit 40 repeatedly calculates the concentration of each element for each cycle detection a predetermined number of times (step S6 → step S5).

  Subsequently, the calculation unit 40 determines whether there is an element concentration that is repeatedly calculated out of the predetermined range (step S7), and there is an element concentration that is out of the predetermined range. Is excluded from the concentration of each element calculated repeatedly (step S8). Then, the average value of the concentration of each element calculated repeatedly is calculated (step S9), and the process ends.

  Next, one cycle detection and calculation by the calculation unit 40 (steps S5 to S9 surrounded by a broken line in FIG. 3) in the ICP-MS device 3 described above will be described in more detail.

In step S5, for each m / z value, the count number per predetermined time is sequentially and continuously detected for the ionized fine powder or gasified product. In step S6, the concentration of each element in the sample S is measured by a so-called standardized semi-quantitative method using the count number detected for each m / z value and the sensitivity coefficient obtained in advance for each m / z value. Is calculated. That is, the concentration of the measurement element (predetermined element) in the i-th one-cycle detection is calculated by the equation (1). In addition, since the count number (cps) detected by the ICP-MS apparatus 3 is different for each element even at the same concentration, the sensitivity coefficient is used to correct a difference in detection sensitivity for each element in the ICP-MS apparatus 3. belongs to. For example, the sensitivity coefficient is obtained by mass analyzing a solid standard sample such as NIST (National Institute of Standards and Technology) 610 to 613 with the LA-ICP-MS apparatus 1 and counting the number of constituent elements per 1 ppm (cps). Is calculated by taking the reciprocal thereof.
X _i = A _x k _x / (A ₁ k ₁ +... + A _n k _n ) (1)
However,
X _i : concentration of measurement element (i = 1,..., P)
p: number of repetitions of one cycle detection A _x: count measuring element (i.e., _{A x} is any one of _A 1 to A _n)
k _x: sensitivity coefficient of the measuring element (i.e., _{k x} is any one of _k 1 to k _n)
A ₁ ,..., A _n : Count number of elements of each m / z value k ₁ ,..., K _n : Sensitivity coefficients of elements of each m / z value n: All elements included in the sample S Number of “elements with different m / z values” as measurement targets

  Then, step S5 and step 6 are repeated 200 times per second, for example, and a plurality of concentrations of each element are calculated by the number of repetitions.

Here, the sample S may be suddenly ablated in large amounts, and the concentration of each element in the fine powder or gasified product generated by the sudden ablation may be shifted and unstable. In this case, among the concentration of each element calculated repeatedly, the concentration of the element affected by the sudden ablation is different from the other concentrations, resulting in a difference. Therefore, in step 7, for example, when the standard deviation in the concentration of each element calculated repeatedly is σ _i (i = 1,..., N), the absolute value of the concentration of each element is 3σ _i or more. Things are identified as the concentration affected by sudden ablation. Then, the identified concentration is excluded from the concentration of each element calculated repeatedly.

In step S8, the average value of the concentration of each element calculated repeatedly is calculated as a quantitative value of the concentration of each element. In other words, the average value of the concentration of the measured element is the predetermined element concentration calculated repeatedly for each cycle detection, and the number of repetitions (the concentration of the element affected by the sudden ablation is excluded in step 7). In this case, the average value of the concentration of the measurement element is calculated as a quantitative value by the equation (2) using the concentration and the number of repetitions in consideration of this exclusion.
X _ave = (X ₁ +... + X _p ) / p (2)
However,
X _ave : Average value of concentration of measurement element,
p: number of repetitions

  As described above, in this embodiment, for each element having a different mass number, one cycle detection for detecting a count number per predetermined time is performed a predetermined number of times, and the concentration of each element is detected for each one cycle detection. Is calculated. Then, for each element having a different mass number, an average value of the concentration calculated a predetermined number of times is obtained. Thus, without using the concept of integrating over a certain time or more, the concentration of each element is calculated each time the count number is acquired, so that the sample S is suddenly ablated in large quantities, and Even if the concentration of each element shifts and becomes unstable in the fine powder or gasified product generated by sudden ablation, the concentration of each element can be obtained with high accuracy.

  Further, as described above, the so-called standardized semi-quantitative method is applied to the calculation of the concentration of each element for each cycle detection, and thus the concentration of each element can be determined with higher accuracy.

  Further, according to the present embodiment, as described above, in calculating the average value of the concentration of each element, one concentration of the concentration of each element repeatedly calculated for each cycle detection is within a predetermined range. When deviating, the average value of the concentration of each element excluding the one concentration is calculated. As a result, even when the sample S is suddenly ablated abundantly and the concentration of each element in the fine powder or gasified product caused by the sudden ablation is deviated, the influence of this sudden ablation And the concentration of each element can be determined with higher accuracy.

  FIG. 4A is a chart showing an example of a result by a conventional mass spectrometry method, and FIG. 4B is a chart showing an example of a result by a mass spectrometry method using the LA-ICP-MS apparatus of FIG. It is. In each chart, for the sake of explanation, elements having different mass numbers in the sample are elements A, B, and C, and the sensitivity coefficient is 1 for each element A, B, and C. Moreover, the time of FIG. 4 (a) and FIG.4 (b) respond | corresponds mutually, and at the time of 0.0025sec, a sample is suddenly ablated abundantly, and the fine powder substance produced by sudden ablation or In the gasified product, the concentrations of the elements A, B, and C are deviated from the concentrations at other points in time and become unstable.

  In the conventional mass spectrometry method, the count numbers of elements A, B, and C are integrated over a certain period of time, and the concentrations of elements A, B, and C are calculated from the integrated values by a standardized semi-quantitative method. Therefore, as shown in FIG. 4A, the integrated value of the count number is greatly influenced by the count number at the time point of 0.0025 sec. As a result, the concentration of each element A, B, C is also 0.0025 sec. It can be confirmed that it is greatly influenced by the count at the time of. On the other hand, in the mass spectrometry method of the present embodiment, as described above, the detection value obtained for each cycle detection is used as a normalized semi-quantitative value. Then, for example, 200 standardized semi-quantitative values are obtained per second, and an average value of these values is finally calculated as a quantitative value. As a result, as shown in FIG. 4 (b), the influence of sudden detection data is suppressed as compared with the conventional mass spectrometry method, and the above effect, that is, the concentration of each element in the sample is highly accurate. The effect that it becomes possible to obtain | require can be confirmed.

  In addition, in the ICP-MS apparatus for introducing a solution, since the time variation of the sample amount to be analyzed is reduced because the solution is spray-introduced by the nebulizer, the integration time during the analysis of the sample (the time for integrating the count number) ) And the concentration of each element having a different mass number is required with high accuracy. On the other hand, in the conventional LA-ICP-MS apparatus, the amount of sample to be analyzed is reduced due to the large variation in the amount of sample to be ablated and the introduction efficiency of the carrier gas or the like depending on the site where the analysis value is measured. Since the fluctuation becomes large, it is difficult to increase the integration time to accurately obtain the concentration of the measurement element.

  Therefore, as described above, according to the mass spectrometric method of the present embodiment, the mass spectrometric accuracy can be greatly increased without using the concept of integrating over a certain period of time, that is, without increasing the integration time. Therefore, it is possible to obtain the concentration of the measurement element with a high accuracy equal to or higher than that of the mass spectrometry method using the ICP-MS apparatus of solution introduction.

  The present invention is not limited to the embodiment described above. For example, in the above-described embodiment, an example is shown in which the average value is calculated by removing the concentration of one measurement element from the concentration of a plurality of measurement elements calculated for each cycle detection. Of course, the number may be one or more as long as it falls outside the predetermined range.

It is a lineblock diagram showing the LA-ICP-MS device concerning the present invention concerning one embodiment of the present invention. It is a figure which shows the control part in the LA-ICP-MS apparatus of FIG. It is a flowchart which shows the mass spectrometry method using the LA-ICP-MS apparatus of FIG. (A) is a chart which shows the example of the result by the conventional mass spectrometry method, (b) is a chart which shows the example of the result by the mass spectrometry method using the LA-ICP-MS apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... ICP-MS apparatus, 40 ... Operation part, 60 ... Mass spectrometry program, S ... Sample.

Claims (5)

A mass spectrometry method for performing mass spectrometry on a sample using a fine powder or gasified product generated by performing laser ablation on a sample containing a plurality of elements having different mass numbers,
Performing one cycle detection for detecting a detection intensity per predetermined time for each of the elements;
Performing the one cycle detection a predetermined number of times;
Calculating an abundance ratio of a predetermined element for each one-cycle detection based on the detection intensity;
And a step of calculating an average value of the abundance ratio calculated for each cycle detection. The detection intensity is a count number, and when the one cycle detection is performed m times, the abundance ratio X _i of the predetermined element in the i th cycle detection is
X _i = A _x k _x / (A ₁ k ₁ +... + A _n k _n )
X _i : abundance ratio of the predetermined element (i = 1,..., M)
A _x: count of the predetermined element (i.e., _{A x} is any one of _A 1 to A _n)
k _x: sensitivity coefficient of the predetermined element (i.e., _{k x} is any one of _k 1 to k _n)
A ₁ ,..., A _n : the respective count numbers of the elements k ₁ ,..., K _n : calculated by the respective sensitivity coefficients of the elements,
The average value X _ave of the abundance ratio is
X _ave = (X ₁ +... + X _m ) / m
The mass spectrometric method according to claim 1, wherein the mass spectrometric method is calculated by:   In the step of calculating the average value of the existence ratios, when one existence ratio is out of a predetermined range among the existence ratios calculated for each one cycle detection, the one existence ratio is calculated. The mass spectrometry method according to claim 1, wherein an average value of the abundance ratios excluded is calculated. For a computer of an ICP-MS apparatus that performs mass analysis on a sample using a fine powder or gasified product generated by performing laser ablation on a sample containing a plurality of elements having different mass numbers,
A process of performing one cycle detection for detecting a detection intensity per predetermined time for each of the elements;
A process of performing the one cycle detection a predetermined number of times;
Based on the detection intensity, a process of calculating the abundance ratio of a predetermined element for each one cycle detection;
And a process for calculating an average value of the abundance ratios calculated for each cycle detection. An ICP-MS apparatus for performing mass spectrometry on a sample using a fine powder or gasified product generated by performing laser ablation on a sample containing a plurality of elements having different mass numbers,
One cycle detection for detecting the detection intensity per predetermined time for each of the elements is performed, the one cycle detection is performed a predetermined number of times, and the presence of the predetermined element for each one cycle detection based on the detection intensity An ICP-MS device comprising: an arithmetic unit that calculates a ratio and calculates an average value of the existence ratios calculated for each cycle detection.

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