JP2001324476A - Inductively-coupled plasma mass spectrometeric analysis method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inductively-coupled plasma mass spectrometric analysis method, capable of accurately determinating a target element, even if the peak of molecular ions with which a coexisting substance or the coexisting substance and a gas component are coupled overlaps with the peak of the mass spectrum of the target element. SOLUTION: When the peak of molecular ions, with which the coexisting substrate or the coexisting substrate and the gas component are coupled, overlaps with the peak of the mass spectrum of the target element at the determination of the trace amount of a substance in a sample, correction intensity is calculated from the intensities of two arbitrarily selected overlapped peaks according formula: I'=iI-(iDB/jDB)jI (where I' is correction intensity; iI is the measured intensity of a mass number i; and iDB is the isotoptip ratio of the mass number i of interference ions) to determinate the target element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for quantifying a trace substance (target element) in various samples using an inductively coupled plasma mass spectrometer, and more particularly, to a coexisting substance in a sample, a gas component, and a combination thereof. The present invention relates to an inductively coupled plasma mass spectrometry method in a case where at least one of the peaks of the molecular ions overlaps with the peak of the mass spectrum of the target element.

[0002]

2. Description of the Related Art For example, as shown in FIG.
In the case where there is spectral interference in which the peak of the interfering element B overlaps the peak of the target element A, conventionally, the following interfering ion interference correction formula (a) is used to calculate the mass number j in which only interfering ions appear. From the intensity, the molecular ion intensity of the mass number i overlapping with the target element ion is obtained using the isotope ratio as a coefficient, and this is subtracted to obtain the net intensity of the target element A. _{^{I '= i I- (i D}} B / j D B) j I ...... (a) I': correction ^intensity, i I: measured intensity of mass number ^i, j _{D B:} isotopes of mass number i of interfering ions Body ratio

In addition, the mass number at which only molecular ions appear is
If three elements overlap, repeat the same correction
The strength of the child ion is obtained. For example, As,
ArCl and Se spectra interfere with each other as shown in FIG.
If so, the net intensity of As is⁷⁵ I_As=⁷⁵I- (⁷⁵D_ArCl/⁷⁷D
_ArCl) ｛⁷⁷I- (⁷⁷D _Se/⁷⁸D_Se)
⁷⁸I｝. Here,ⁱD_ArCl,ⁱD_SeIs ArC
It is an isotope ratio at the mass number i of 1 and Se.

[0004]

In the above-mentioned conventional correction equation, the calculation of molecular ion intensity requires that there is a mass number at which only the peak of the molecular ion appears without the peak of the target element ion. It is assumed. However, depending on the combination of the target element and the coexisting element, there is no mass number at which only the peak of such molecular ions appears, or at a mass number at which only the peak of molecular ions appears, which is undesirable for measurement and is a very weak peak. In some cases, it is difficult to perform sufficient correction.

The present invention has been made to solve the above-mentioned problems, and it has been found that, when an inductively coupled plasma mass spectrometer is used to quantify trace substances in various samples, coexisting substances or molecular ions in which coexisting substances and gas components are combined are used. It is an object of the present invention to provide an inductively coupled plasma mass spectrometry capable of accurately quantifying a target element even when such a peak overlaps a peak of a mass spectrum of the target element.

[0006]

In order to achieve the above object, an inductively coupled plasma mass spectrometry method according to the present invention comprises: (a) a coexisting substance, a gas component (atmosphere, plasma gas) in a sample; At least one of the peaks of the mass spectrum of the molecular ion that has occurred, causing spectral interference overlapping the peak of the mass spectrum of the measurement element, and the peak of the mass spectrum of the target element, the peak of the mass spectrum of the interfering ion When there is no overlapping peak, or (b) at least one of the peaks of the mass spectrum of the coexisting substance, the gas component (atmosphere, plasma gas), and the molecular ion combined with these in the sample is the mass spectrum of the measured element. When there is spectral interference that overlaps with the peak, and the interference in the peak of the mass spectrum of the target element An arbitrarily chosen overlap in any case where the intensity of the peak that does not overlap the peak of the ON mass spectrum is less than one tenth of the intensity of the peak that overlaps the peak of the interfering ion mass spectrum; The method is characterized in that the target element is quantified by obtaining the corrected intensity from the intensity of two peaks having the following equation (1). _{^{I '= i I- (i D}} B / j D B) j I ...... (1) I': correction intensity ⁱ I: measured intensity of mass number i ⁱ D _B: isotope ratio mass number i of interfering ions

As described above, the arbitrarily selected overlapping 2
From the intensity of this peak, the corrected intensity is determined by the equation (1) to determine the target element, and at least one of the peaks of the coexisting substance, the gas component, and the bonded molecular ion in the sample becomes the target element. It is possible to accurately quantify the target element even when the peak overlaps with the peak of the mass spectrum.

Hereinafter, the present invention will be described with reference to a model in which the peak of an interfering ion (interfering element) overlaps the peak of a target element in the inductively coupled plasma mass spectrometry (see FIG. 1).

As shown in FIG. 1, when the target element A is subject to spectral interference of interfering ions (interfering elements) B, that is, when the peaks of the mass spectra of A and B overlap as shown in FIG. The intensity of the mixed peak of B is considered to be the sum of “concentration × isotopic abundance × detection sensitivity” for both. Mass number i, the mixed peak two of the intensity of j, two yuan one following equations _{^{i I = i I A + i}} I B = i D A A A C A + i D B A B C
_{^{B j I = j I A +}} j I B = j D A A A C A + j D B A B C
_B, however, i, j: mass number to be measured (hereinafter, shows the case of a mass number i, the same applies to _{^{j.) I I A, i}} I B: The purpose element A and the interference with the mass number i strength of net ionic B C _{a, C B:} concentration ⁱ D _a purpose element a and interfering ion B, ⁱ D _B: isotopes of a or B in the mass number i a _{a, a B:} sample of This is expressed as a sensitivity coefficient indicating the measured intensity of the total isotope with respect to the element concentration, and by solving this, the correction intensity (I ′) that is a constant multiple of the measured element ionic intensity ( ⁱ I _A ) can be calculated.

That is, I '=ⁱI- (ⁱD_B/^jD_B)^jI, this correction intensity becomes I '=ⁱI- (ⁱD_B/^jD_B)^jI =ⁱD_AA_AC_A+ⁱD_BA_BC_B− (ⁱD_B/^jD_B) (^jD_AA_AC_A+ ^j D_BA_BC_B) = ｛1- (ⁱD_B/^jD_B) (^jD_A/ⁱD_A)｝ⁱD_AA_AC_A …… (2) = ｛1- (ⁱD_B/^jD_B) (^jD_A/ⁱD_A)｝ⁱI_A ... (3), which is compared with the net intensity at the mass number i of the target element A.
It will be the value shown. And using this correction strength
Quantification of the target element by eliminating the effects of interfering ions
It becomes possible.

Further, the above equation (2), the constants in {} of (3), the value obtained as the correction strength indicates the rate at which correction intensity decreases from the original ⁱ I _A. Therefore, by comparing isotope abundance ratios that contribute to this constant, it becomes possible to select a measured mass number that can maximize the effective sensitivity before measurement.

Although not particularly shown, the target element A has 2
When the kinds of interfering elements B and C overlap, that is,
When represented by simultaneous equations,ⁱ I =ⁱI_A+ⁱI_B=ⁱD_AA_AC_A+ⁱD_BA_BC
_B+ⁱD_CA_CC_C ^j I =^jI_A+^jI_B=^jD_AA_AC_A+^jD_BA_BC
_B+^jD_CA_CC_C ^k I =^kI_A+^kI_B=^kD_AA_AC_A+^kD_BA_BC
_B+^kD_CA_CC_C To find the same correction strength for each two equations as follows
Than,ⁱ I '=ⁱI- (ⁱD_C/^kD_C)^kI = ｛1- (ⁱD
_C/^kD_C) (^kD_A/ⁱD_A)｝ⁱD_AA_AC_A+
｛1- (ⁱD_C/^kD_C) (^kD_B/ⁱD_B)｝ⁱD_B
A_BC_B= ｛1- (ⁱD_C/^kD_C) (^kD_A/
ⁱD_A)｝ⁱI_A+ ｛1- (ⁱD_C/^kD_C) (^kD_B
/ⁱD_B)｝ⁱI_B ^j I '=^jI- (^jD_C/^kD_C)^kI = ｛1- (^jD
_C/^kD_C) (^kD_A/^jD_A)｝^jD_AA_AC_A+
｛1- (^jD_C/^kD_C) (^kD_B/^jD_B)｝^jD_B
A_BC_B= ｛1- (^jD_C/^kD_C) (^kD_A/
^jD_A)｝^jI_A+ ｛1- (^jD_C/^kD_C) (^kD_B
/^jD_B)｝^jI_B  Thus, the contribution of the interference component C can be eliminated. This
Correction strengthⁱI ',^jI ′ and the intensity reduction rate due to the correction
Multiplied isotope contrast (｛1- (ⁱD_C/^kD_C) (^kD_A/
ⁱD_A)｝ⁱD_AEtc.) and make the same correction and
That is, I "=ⁱI '-[｛1- (ⁱD_C/^kD_C) (^kD_B/ⁱ
D_B)｝ⁱD_B/ ｛1- (^jD_C/^kD_C) (^kD_B/
^jD_B)｝^jD_B]^jBy correcting I ′, the net intensity of target element A can be reduced.
An exemplary correction intensity I ″ can be determined.
In addition, the same correction is repeated even when the number of interfering elements varies.
It is possible to calculate the correction strength for the target element
Wear.

According to the inductively coupled plasma mass spectrometry method of the present invention, a standard solution group (calibration) containing no coexisting substances is used for a large number of unknown samples containing coexisting substances causing interference at an arbitrary concentration. Quantitative analysis of the target element in the unknown sample by the calibration curve method using the calibration curve and the internal standard method.

For an unknown sample containing a coexisting substance causing interference, a standard solution group (calibration curve) not containing the coexisting substance is used, and the correction is performed by the calibration curve method together with the correction by the internal standard method. By quantifying the target element, the target element in the unknown sample can be quantified efficiently and with high accuracy. The internal standard method means that a certain concentration of the internal standard element is present in the measurement sample and standard solution in advance, and the ratio between the measured element intensity and the internal standard element intensity is used as the intensity of the measured element (relative intensity). This is a concept meaning a method of correcting the fluctuation of the detection sensitivity.

According to the inductively coupled plasma mass spectrometry method of the present invention, the effective intensity at the time of correction is calculated from the isotope ratio of the target element and the interfering ion, and the mass number giving the maximum effective intensity is selected for measurement. It is characterized by performing.

By calculating the effective intensity at the time of correction from the isotope ratio of the target element and the interfering ion, and selecting the mass number that gives the maximum effective intensity and performing the measurement, the trace substance can be more accurately quantified. Will be possible.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described, and features thereof will be described in more detail.

[0018] [Embodiment 1] In Embodiment 1, by using the interference correction formula I ^'= i of the invention described above _{^{I- (i D B / j D}} B) j I ...... (1), inductive coupling Plasma mass spectrometry (ICP-M
The case where W in Er ₂ O ₃ is measured (quantified) by S) will be described as an example. Er ₂ by this ICP-MS
In the measurement of W in O ₃ , W is a coexisting E in the sample.
r and a molecular ion E in which oxygen originating from the atmosphere or the like is bonded
Receives spectral interference of rO ⁺ . The oxygen isotope is 9
9.8% has a mass number of 16, and molecular ions due to other isotopes of oxygen can be neglected in the measurement accuracy of the apparatus. Therefore, the molecular ion is Er ¹⁶ O, and the isotope abundance ⁱ D
_ErO can be considered as ^i- _{16D Er} .

In this embodiment, Er ₂ O ₃ is used as a sample.
A solution obtained by adding a known amount of W to a nitric acid solution was used. The measured mass numbers were 183, 186 and 175 (internal standard element (L
u)), and the mass number 178 was measured for comparison with the conventional method (see the above-mentioned conventional technology). However, mass number 1
In the case of No. 78, since the intensity was very low, the integration time was set to another ten times.

The measurement is performed on a sample group in which the concentrations of Er ₂ O ₃ and W are changed, and the ¹⁸⁶ I intensity when no correction is made (in the case of no correction) The correction formula of the conventional method: I ′ = ¹⁸⁶ I− ( 14.9 / 0.
14) Correction intensity I ′ by ¹⁷⁸ I Correction formula of the present invention: I ′ = ¹⁸⁶ I− (14.9 / 2)
3.0) The corrected intensity I ′ by ¹⁸³ I was plotted against the W added concentration for each Er ₂ O ₃ concentration. FIG. 2 shows the correction strength (relative strength) in the case of no correction as described above, and FIG. 3 shows the correction strength (relative strength) in the case where the correction strength is corrected by the above-described conventional correction formula. FIG. 4 shows the corrected intensities (relative intensities) obtained in this case. The correction coefficient was determined from the isotope contrast measurement of each element using the same apparatus as the correction measurement.

[0021] From FIG. 2, in the case without the above correction, the molecular ion interferences ErO ^+, approximately Er
₂ O ₃ is ¹⁸⁶ I in proportion to the concentration increases, the intensity at the _Er 2 _{O 3} presence is seen may not match with not coexist _Er 2 _{O 3.}

FIG. 3 also shows that the intensity in the coexistence of Er ₂ O ₃ is Er even when the correction by the above-mentioned conventional method is performed.
_It can be seen that this does not sufficiently coincide with the case where ₂ O ₃ does not coexist. This is a very weak peak of ^{175 in the} conventional method.
It is considered that I must be measured, and correction errors are likely to occur due to the influence of variations in measurement counts and spectral interference of other trace components.

On the other hand, correction by the method of the present invention is performed.
In this case, as shown in FIG. ₂O₃Strength under coexistence
The degree is Er₂O₃Is consistent with the intensity when no
rO ⁺Eliminates the effects of molecular ion interference and focuses only on W concentration
It can be seen that the proportional correction ideal intensity is obtained.

As described above, according to the method of the present invention, it is possible to perform an appropriate correction even when the conventional method cannot perform a sufficient correction, and it is possible to obtain a correct correction intensity. it can.

The effect of molecular ion interference when Er ₂ O ₃ coexists at a rate of 100 μg / ml is as follows:
When converted with the W density indicating the same intensity, when no correction is made,
When the correction is performed by the conventional method and when the correction is performed by the method of the present invention, the results are as follows. Uncorrected 30 ng / ml Corrected by the conventional method 2 ng / ml Corrected by the method of the present invention 0.2 ng / ml

The influence of molecular ion interference is one of the quantitative values.
Assuming that the range of less than 0% is the quantification limit, the mass ratio at this time is as follows (however, the average value of 9 samples for each quantification method). No correction W / Er ₂ O ₃ = 3000 wtppm (3000 μg / g) Conventional method correction W / Er ₂ O ₃ = 200 wtppm (200 μg / g) Correction of the present invention W / Er ₂ O ₃ = 20 wtppm (20 μg / g)

From the above results, it can be seen that by performing the correction according to the method of the present invention, the measurement limit can be improved about 150 times as much as the case without correction and 10 times as much as the conventional method. However, the normal measurement limit tends to be slightly worse than the upper limit in any of the quantitative methods due to measurement variations.

Further, the present invention is not limited to the case of the above-described embodiment, but can be applied to the case where there are other various molecular ion interferences. Can be improved.

As described above, the use of the interference correction formula of the present invention makes it possible to accurately quantify a trace substance in a sample, excluding the influence of molecular ion interference. Further, according to the method of the present invention, since the correction can be performed only from the intensity at which the molecular ion and the target element are mixed, it is possible to use the correction formula according to the conventional method when both the isotope mass numbers completely match. The present invention can be applied to a case where it cannot be performed (for example, a case where Hf in Dy ₂ O ₃ is quantified) and is significant.

Further, according to the method of the present invention, it is not necessary to measure a peak having a low intensity. Therefore, when a peak measurement having a low intensity is performed (for example, in the conventional method, a measurement of a low mass number is performed in a non-band with an intensity). As compared to the case where W in Er ₂ O ₃ is quantified, which is unavoidable, the measurement accuracy can be improved and the integration time can be shortened.

In addition to the method of the present invention, a method of measuring the monoatomic ion intensity of a coexisting element and correcting the contribution of molecular ion interference based on the molecular ion generation rate can be considered as another correction means. However, the molecular ion generation rate is susceptible to changes in the state of the apparatus and non-spectral interference of coexisting elements, which may cause errors.

On the other hand, the isotope abundance used as the basis for calculating the molecular ionic strength in the present invention is hardly affected by this, but this is because the isotope of the same element or the same molecule shows similar behavior on the apparatus. It is thought to be due to. Therefore, according to the present invention, it is possible to perform more accurate quantification than when performing correction based on the molecular ion generation rate.

Embodiment 2 <Measurement Example 1> A sample was prepared by dissolving Er ₂ O ₃ with nitric acid and adding a known amount of a W standard solution. IC for this sample
Measurement was performed by P-MS, and W10 ng / m ₂ was used in the presence of 100 μg / ml of Er ₂ O ₃ using the corrected intensity of the first embodiment.
l was quantified. The quantification was performed by a calibration curve method using a standard solution group (calibration curve) not containing Er ₂ O ₃ .

In performing the quantification, 10 ng / ml of Lu was added to the sample and the standard solution group (calibration curve) as an internal standard, and the sensitivity fluctuation was corrected by the internal standard addition method. Further, the measurement by the conventional correction formula (measured mass number 186, 178) was also performed in parallel, and compared with the correction method of the present invention. The measurement conditions were the same for both,
The measurement was performed under the conditions shown in Table 1. However, since the mass number 178 required for performing the correction by the conventional method has a very low intensity, the integration time was increased by a factor of 10. The correction intensity was calculated for the calibration curve in the same manner as for the unknown sample, and this was used for the calibration curve method.

[0035]

[Table 1]

Table 2 shows the results of measurement and quantification under the conditions shown in Table 1.

[0037]

[Table 2]

As shown in Table 2, in the case of no correction and the correction by the conventional method, positive errors occurred in the quantitative value and the recovery rate due to molecular ion interference. Quantification could be performed within a concentration recovery rate of 100 ± 10%. When no correction is made, the recovery rate is 1
The ratio of 00 ± 10% is W / Er ₂ O ₃ = 10000
wtppm (10000 μg / g), and even when corrected by the conventional method, 1000 wtppm (1000 μg / g).
g). From these results, it is understood that the measurement limit can be improved by a factor of 10 to 100 according to the method of the present invention.

<Measurement Example 2> The same correction as in the above Measurement Example 1 was performed, and Hf, Dy ₂ O _{3 in the} presence of 100 μg / ml was used.
The Pb concentration was determined in the presence of 100 μg / ml of Er ₂ O ₃ . Tables 3 and 4 show the measurement conditions.

[0040]

[Table 3]

[0041]

[Table 4]

Then, the correction intensity I 'was obtained by using the interference correction formula of the present invention. Hf in Dy ₂ O ₃ : I ′ = ¹⁸⁰ I− (28.3 / 2
4.9) Pb in ¹⁷⁹ I Er ₂ O ₃ : I ′ = ²⁰⁸ I− (26.8 / 3
3.6) Tables 5 and 6 show the results of quantification of ²⁰⁶ I Hf and Pb.

[0043]

[Table 5]

[0044]

[Table 6]

From Tables 5 and 6, it can be seen that any of the elements can be quantified with an addition concentration recovery rate of 100 ± 10%.

<Measurement Example 3> Er₂O₃Different coexistence concentration
W in the solution sample group is the same as in the first embodiment.
Measurement in the same manner as in the first embodiment.
Correction intensity I '= ¹⁸⁶I- (14.9 / 23.0)
¹⁸³The quantification was performed using I. The quantification is E
r₂O₃Was performed using a calibration curve containing no. Measurement results
It is shown in Table 7.

[0047]

[Table 7]

From these results, it is found that W can be quantitatively determined with high accuracy by using a common standard sample group containing no Er ₂ O ₃ with respect to sample groups having different Er ₂ O ₃ contents. It can be seen that efficient and simple measurement can be performed even when the detailed Er ₂ O ₃ concentration is unknown.

Further, the present invention can be applied to various molecular ion interferences, and similar simple measurements can be performed on various samples. Furthermore, the correction intensity can be directly converted into a quantitative value by a normal (not considering molecular ion interference) calibration curve calculation process, and efficient and accurate quantification can be performed.

The influence of coexisting elements can be divided into spectral interference of interfering ions and non-spectral interference (overall intensity changes such as physical interference and ionization interference). Embodiment 1
The correction intensity I ′ corrected by the method described above is not affected by the Er concentration and the ErO ⁺ concentration in the sample, and always gives a constant multiple of the net target element intensity. This constant depends only on the isotope abundance ratio, and can be regarded as a constant as long as the isotope abundance ratio of the sample does not deviate from the natural isotope ratio. This is because Er in the sample
The same applies to the case where is not included. Then, as in Embodiment 2, the non-spectral interference can be corrected without using the standard addition method by using the internal standard addition method using an appropriate internal standard element.

As described above, according to the method of the second embodiment,
Any Er₂O₃Concentration sample and Er ₂O₃Inspection does not include
Simple calculation by finding a common correction strength for the dose line
Quantification of the target element with high accuracy by a simple calibration curve method.
And become possible. In addition, both calibration curves and unknown
To obtain a correction intensity that is a constant multiple of the net measured element intensity.
The correction intensity can be calculated using the standard calibration curve calculation.
It can be used for processing as it is.

[Embodiment 3] Here, a method of determining (selecting) the measured mass number will be described. That is, when quantifying W in Er ₂ O ₃ by the methods of Embodiments 1 and 2, the measured mass number was determined based on the following criteria. Since the intensity of each mass number is due to two components of ErO ⁺ and W, the number of mass numbers to be measured is 2. The mass numbers i and j according to the following a) and b) are determined. However, as to which of i and j is larger, the one in which the coefficient of a) is positive is adopted as larger. a) Coefficient ｛1- () that determines effective sensitivity of correction intensity
^{_{i-16 D Er / j-}} 16 D Er) (j D W /
ⁱ D _W )｝ is large (close to 1). b) The measured intensity (total intensity) of each mass number is large. As an example, considering the quantification of W in Er ₂ O ₃ , Er,
Table 8 and Table 9 show the mass numbers and the isotope abundance ratios of and W.

[0053]

[Table 8]

[0054]

[Table 9]

Of these, the mass numbers 178 and 180 have a small abundance ratio and a low strength (mass numbers 182 to 184, 18
6 or less) and the coefficient ｛1- ( ^i- _16DEr / ^j- _16D ) in other combinations of mass numbers.
Considering _{^{Er) (j D W / i}} D W)}, so that the table 10.

[0056]

[Table 10]

From the results, the mass numbers 183 and 186 giving the maximum coefficient are selected as the measured mass numbers. For other elements, the measured mass number can be similarly selected. In other words, when the type of interfering ion interference that has an influence is known (usually, it can be determined from the qualitative measurement spectrum, and in the raw material analysis, the influence of oxides, hydrides, argon compounds, etc., from the main components of the raw material) If the number of components that contribute to the intensity is 2, the intensity of 2 mass numbers (binary simultaneous equations), and if it is 3, the correction intensity of each component is calculated with the intensity of 3 mass numbers. Can be.

The correction intensity according to the present invention is, for example,
Er₂O₃In the case of quantification of W inside, I '= {1- (^i-16D_Er/^j-16D_Er) (^j
D_W/ⁱD_W)｝ⁱI _W, Represented by the net target element strengthⁱI_WIs a constant coefficient
｛1- (^i-16D_Er/ ^j-16D_Er) (^jD_W/
ⁱD_W) I understand that it is decreasing due to｝
You. Therefore, the isotope that makes the coefficient close to 1
If a mass number with a ratio is selected, accuracy due to a decrease in effective sensitivity
Deterioration can be avoided.

Also, depending on the isotope abundance ratio, this coefficient may be negative in calculation, and in this case, the absolute value may exceed 1. However, in this case, the intensity of ⁱ I _W is low,
^Since the intensity of ^{j- 16} I _Er is low (that is, the intensity of ^j I _W is high), improvement in accuracy cannot be expected in the correction intensity that is the result of subtraction of the measured value. In this case, it is considered that this is the same as the case where i and j are exchanged and the coefficient is made positive. Therefore, in the present invention, the combination of i and j is limited to the case where a positive coefficient is given.

Note that the present invention is not limited to the first to third embodiments, and within the scope of the invention,
Various applications and modifications can be made.

[0061]

According to the present invention as described above, inductively coupled plasma mass spectrometry method of the present invention (claim 1), from the two intensity peaks with overlapping arbitrarily ^{selected, I '= i I- (i} D _B /
by ^{j D} B) _j I ^(Formula (1)), since such a quantitative objective elements seeking correction intensity, the peak of the coexisting substance, gas components and their bound molecular ion in the sample at least Even when one of them overlaps the peak of the mass spectrum of the target element, the target element can be accurately quantified. That is, according to the first aspect of the present invention, the influence of interference is eliminated in the determination of elements affected by molecular ion interference by coexisting elements, and the measurement limit is set to 1
It can be improved by 0 to 100 times. In addition, since the limitation of the measured mass number is relaxed, it can be applied to almost all elements, and the measurement of low intensity mass number can be avoided, and the integration time can be reduced to about 1/10. become.

Further, as in the inductively coupled plasma mass spectrometry method according to claim 2, for a large number of unknown samples containing a coexisting substance causing interference at an arbitrary concentration, a standard solution group containing no coexisting substance. (Calibration curve) and the correction by the internal standard method together with the quantification of the target element in the unknown sample by the calibration curve method, the target element in the unknown sample can be efficiently and accurately determined. Quantitation becomes possible. That is, according to the invention of claim 2, in the quantification of an element that undergoes molecular ion interference of a coexisting element, a standard liquid group containing no coexisting element is compared with a sample group having a different coexisting element concentration or a sample group having an unknown coexisting element concentration. Quantification by the calibration curve method using (calibration curve) becomes possible, and the complexity of pretreatment by the standard addition method and the influence of impurities in reagents when performing matrix matching of coexisting elements on the calibration curve can be avoided. . Further, the correction intensity can be handled in the same way as the normal measurement intensity, and the same calculation processing as when there is no interference can be performed. For this reason, at the time of introduction, the present invention can be efficiently implemented only by adding a simple calculation to the existing analysis processing.

Further, as in the inductively coupled plasma mass spectrometry method according to the third aspect, the effective intensity at the time of correction is calculated from the isotope ratio of the target element and the interfering ion, and the mass number giving the maximum effective intensity is selected. When the measurement is performed, it is possible to quantify the trace substance with higher accuracy. That is,
According to the third aspect of the invention, it is possible to easily determine the measured mass number for molecular ion interference correction, and it is possible to perform measurement with the minimum necessary mass number. Therefore, it is possible to shorten the integration time at the time of measurement, in addition to the fact that a mass number having a large strength can be used. Also,
Shortening the integration time not only directly reduces the measurement time, but also shortens the time for one mass scan in measuring the time-dependent intensity by using ETV, laser ablation, flow injection, ion chromatography, etc. Also leads. Moreover, the accuracy can be improved by reducing the influence of the intensity change during scanning.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a case where a peak of an interfering ion (interfering element) overlaps a peak of a target element in the inductively coupled plasma mass spectrometry.

FIG. 2 is a graph showing the relationship between the intensity (relative intensity) and the W concentration in the case of uncorrected W measurement in Er ₂ O ₃ .

FIG. 3 is a graph showing the relationship between the intensity (relative intensity) and the W concentration when correction is performed by a conventional method in W measurement in Er ₂ O ₃ .

FIG. 4 is a graph showing the relationship between the intensity (relative intensity) and the W concentration in the measurement of W in Er ₂ O ₃ when the correction according to the method of the present invention (claim 1) is performed.

FIG. 5 is a diagram conceptually showing a correction method in a conventional inductively coupled plasma mass spectrometry method.

FIG. 6 is a diagram conceptually showing a state of interference of ArCl with respect to As measurement by the inductively coupled plasma mass spectrometry.

Continuation of front page (72) Inventor Takahiro Takase 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto F-term in Murata Manufacturing Co., Ltd. (reference) 5C038 HH28

Claims (3)

[Claims] (1) Coexisting substances and gas components in a sample (atmosphere,
Plasma gas), and at least one of the peaks of the mass spectrum of the combined molecular ions causes spectral interference overlapping with the peak of the mass spectrum of the element to be measured, and at the peak of the mass spectrum of the target element, If there is no peak that does not overlap with the peak of the interfering ion mass spectrum,
Or (b) at least one of the peaks of the mass spectrum of the coexisting substance, the gas component (atmosphere, plasma gas) and the combined molecular ion in the sample causes spectral interference overlapping with the peak of the mass spectrum of the element to be measured. And the intensity of the peak that does not overlap the peak of the interfering ion mass spectrum among the peaks of the mass spectrum of the target element is 10 minutes of the intensity of the peak that overlaps the peak of the interfering ion mass spectrum. In the case of any of the following cases, it is determined from the intensity of two arbitrarily selected overlapping peaks that the corrected intensity is obtained by the equation (1), thereby quantifying the target element. Inductively coupled plasma mass spectrometry. _{^{I '= i I- (i D}} B / j D B) j I ...... (1) I': correction intensity ⁱ I: measured intensity of mass number i ⁱ D _B: isotope ratio mass number i of interfering ions 2. For a large number of unknown samples containing a coexisting substance causing interference at an arbitrary concentration, a standard solution group (calibration curve) not containing the coexisting substance is used, and correction by an internal standard method is performed. 2. The inductively coupled plasma mass spectrometry method according to claim 1, wherein the target element in the unknown sample is quantified by the calibration curve method in combination. 3. The method according to claim 1, wherein the effective intensity at the time of correction is calculated from the isotope ratio of the target element and the interfering ion, and the mass number giving the maximum effective intensity is selected for measurement.
The inductively coupled plasma mass spectrometry method according to the above.