JP2011232106A - Icp optical emission spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ICP optical emission spectrometer which is capable of easily and quickly performing high-precision quantitative analysis.SOLUTION: The ICP optical emission spectrometer performs measurement and data processing in accordance with a predetermined analysis sequence. According to the analysis sequence, a qualification step (S100) of preliminarily measuring a spectral line at a wavelength position corresponding to each of a plurality of elements with respect to an unknown sample, and a determination step (S200) of specifying a main constituent element in the unknown sample on the basis of the measurement result, referring to a database to calculate the amount of interference of the main constituent element with a spectral line of a target element, and determining whether a predetermined quantification precision can be obtained at a measuring wavelength position of the target element or not on the basis of the amount of interference are sequentially executed, and when it is determined that the predetermined quantification precision can be obtained, a quantification step (S300) of measuring a spectral line at the wavelength position to calculate a quantitative value of the target element with respect to the unknown sample and a standard sample is executed.

Description

  The present invention relates to an inductively coupled plasma (ICP) emission spectroscopic analyzer.

  The ICP emission spectroscopic analyzer is an apparatus that excites a sample with high-temperature plasma and analyzes components contained in the sample from the obtained spectral lines. Such an ICP emission spectroscopic analysis apparatus includes a light emitting unit, a spectroscopic unit, a detection unit, a data processing unit, and the like. A plasma flame is generated by high-frequency induction in the light emitting unit, and the sample is atomized in the plasma flame. Is introduced. Atoms contained in the sample are excited by the thermal energy of the plasma to emit light, and the light is introduced into the spectroscopic unit and separated. The split light is detected by the detection unit, and the detection signal is sent to the data processing unit. The data processor performs a predetermined calculation based on the detection signal, and performs quantitative / qualitative analysis of elements contained in the sample from the wavelength and intensity of the obtained atomic spectrum.

  In an ICP emission spectroscopic analyzer, a sequential type spectrometer having an optical path configuration called a Zerni-Turna type may be used as the spectroscopic unit. FIG. 7 shows an example of the configuration of an optical system using a conventional Zellni-Turner spectrometer. Light emitted from a light source (that is, an ICP torch) provided in the light emitting unit 10 is collected by the lens 31 and applied to the entrance slit 32. The light that passes through the entrance slit 32 and is introduced into the spectroscopic unit 30 is reflected by the first concave mirror 33 and sent to the planar diffraction grating 34. The light wavelength-dispersed by the planar diffraction grating 34 is reflected by the second concave mirror 35 and projected onto the exit slit 36. Of the dispersed light, only light having a specific wavelength that has passed through the slit opening of the exit slit 36 is extracted to the outside of the spectroscopic unit 30. When the diffraction grating 34 is rotated around an axis passing through the surface center of the planar diffraction grating 34 (arrow M in FIG. 7), the wavelength of light passing through the exit slit 36 and reaching the detector 41 changes. Thereby, wavelength scanning can be performed and the wavelength intensity distribution of the light produced | generated by the light emission part can be measured.

  When the exit slit 36 is reciprocated in the wavelength dispersion direction (arrow S in FIG. 7), the wavelength passing through the slit opening of the exit slit 36 changes in the same manner as when the planar diffraction grating 34 is rotated. Thus, wavelength scanning can also be performed. In general, when both are used for wavelength scanning, scanning in a wide wavelength range is performed relatively roughly by rotating the planar diffraction grating 34, and scanning in the vicinity of a specific wavelength is performed finely by reciprocating movement of the exit slit 36. I have to.

  By the way, in the ICP emission spectroscopic analyzer, since the number of emission spectrum lines of the element is very large, a coexisting element having a wavelength close to that of the spectrum line of the target element (that is, an element other than the target element contained in the sample). Spectral lines may overlap (that is, under the influence of spectral interference), and the spectral intensity of the target element may appear to be larger than actual. However, since there are usually many spectral lines of one kind of element, there are many overlapping lines of coexisting elements even if there is a problem of overlapping of the spectral lines of coexisting elements in a certain spectral line. In some cases, the above problem can be avoided by selecting a spectral line having a different wavelength that does not affect the above.

  Therefore, when the target element in a sample is to be quantified using a sequential ICP emission spectroscopic analyzer, qualitative analysis is performed prior to quantitative analysis, and it is suitable for quantitative analysis with little influence of spectral interference. Determining the wavelength is performed.

  FIG. 8 shows a procedure for such qualitative analysis and quantitative analysis for studying conditions. In the figure, the portion surrounded by a dotted line (that is, steps S801, S803, and S805) indicates steps executed on the apparatus side, and the other portion (that is, steps S802 and S804) indicates steps executed by the analyst. (The same applies below).

  Specifically, spectrum lines are first measured for all measurable elements, and the approximate concentration of each element in the sample to be analyzed (referred to as a semi-quantitative value) is calculated (step S801, hereinafter this). Is called qualitative analysis of all elements). In addition, the measurement of the said spectral line is performed about one wavelength position previously designated for every element, and the semiquantitative value of each element is calculated | required from the height (namely, light emission intensity). Subsequently, the person in charge of the analysis refers to the semi-quantitative value and identifies the main component element in the sample to be analyzed (step S802). Thereafter, the target element is measured at a plurality of wavelength positions (step S803, hereinafter referred to as a multiple wavelength qualitative analysis). The analyst refers to the result of the multi-wavelength qualitative analysis, and selects the wavelength position of the spectral line that is less affected by the spectral interference due to the main component element as the wavelength for quantifying the target element (step S804). Then, quantitative analysis at the selected wavelength position is executed, and the concentration (namely, quantitative value) of the target element in the analysis target sample is calculated (step S805).

  In addition, the spectral line with low signal intensity has a problem that the S / N ratio with respect to the background noise is bad and the quantitative accuracy is lowered. In some cases, there are no other suitable spectral lines. In such cases, inter-element correction processing (coexisting elements) is conventionally used to reduce the effect of coexisting element spectral lines even if they overlap, and to increase the accuracy and quantitative sensitivity (detection limit) of the target element. (Referred to as Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 5-45287 JP 2006-275892 A

  When performing qualitative analysis for examination of conditions prior to quantitative analysis as described above, three measurements with different analysis conditions for the same sample, that is, measurement for all element qualitative analysis, measurement for multiple wavelength qualitative analysis In addition, it is necessary to perform measurement for quantitative analysis, and there is a problem that it takes time and effort.

  In addition, the quantitative analysis may be performed by omitting the qualitative analysis for the condition examination as described above. In this case, as shown in FIG. 9, the measurement for quantitative analysis is performed at a plurality of wavelength positions at which the emission spectrum of the target element is obtained (step S901), and then the person in charge of analysis refers to the measurement result and the plurality of the plurality of wavelengths are obtained. The person in charge of analysis selects what seems to be optimal for quantification from the wavelength positions (step S902). Then, the concentration of the target element in the analysis sample is calculated from the height of the spectral line at the selected wavelength position (step S903).

  However, in quantitative analysis, in order to ensure sufficient analysis accuracy, it is necessary to lengthen the measurement time at one wavelength position (about 10 to 100 times that in the case of qualitative analysis), so measurement is performed only for the target element. Therefore, in the above method, information cannot be obtained for elements other than the target element among the various elements contained in the sample to be analyzed. For this reason, considerable knowledge and experience are required to select the optimum wavelength from the plurality of wavelength positions at which the measurement for quantitative analysis has been performed, and it is difficult for a skilled analyst to do this. there were. In addition, when measurement for quantitative determination is performed at a plurality of wavelength positions as described above, there is a problem that the time required for measurement increases.

  The present invention has been made in view of the above-described problems, and the object of the present invention is to perform highly accurate quantitative analysis in a short time, and easily perform accurate quantitative analysis even without a skilled analyst. An object of the present invention is to provide an ICP emission spectroscopic analyzer capable of obtaining a result.

An ICP emission spectroscopic analysis apparatus according to the first aspect of the present invention, which has been made to solve the above problems,
Excitation means for exciting a sample to emit light having a wavelength unique to the element contained in the sample, spectroscopic means for wavelength-dispersing the light, and a photodetector for detecting wavelength-dispersed light that has passed through the spectroscopic means, In an ICP emission spectroscopic analysis apparatus comprising:
a) wavelength scanning means for changing the wavelength of the chromatic dispersion light reaching the light receiving surface of the photodetector;
b) data processing means for generating emission spectrum data from the detection signal acquired by the photodetector and performing predetermined data processing based on the emission spectrum data;
c) a database that records information on the spectral interference that each element has on other elements for each element;
d) control means for controlling the wavelength scanning means and the data processing means based on the analysis sequence;
And the analysis sequence is
A qualitative step of measuring spectral lines at each wavelength position corresponding to each of a plurality of elements in advance for the sample to be analyzed;
Based on the measurement result in the qualitative step, the main component element in the sample to be analyzed is specified, and the interference amount of the main component element with respect to the spectral line of the target element from the measurement result in the qualitative step with reference to the database A determination step of determining whether a predetermined quantitative accuracy is obtained at the measurement wavelength position of the target element in the qualitative step based on the amount of interference;
Are sequentially executed, and when it is determined in the determination step that a predetermined quantitative accuracy is obtained,
For a standard sample containing the sample to be analyzed and the target element at a known concentration, a spectral line at a wavelength position determined to obtain a predetermined quantitative accuracy in the determination step is measured, and a calibration curve is obtained from the measurement result of the standard sample. A quantitative step for calculating a quantitative value of the target element from the measurement result of the sample to be analyzed with reference to the calibration curve,
It is characterized in that it is executed.

  According to the ICP emission spectroscopic analysis apparatus according to the first aspect of the present invention having the above-described configuration, the above-mentioned all-element qualitative analysis is performed by the qualitative step, and the main component elements in the analysis target sample are identified from the result. The Then, whether or not the measurement wavelength of the target element in the qualitative determination for all elements is suitable for quantitative analysis by the determination step, that is, whether or not a predetermined quantitative accuracy can be achieved when quantitative analysis is performed at the measurement wavelength. Is automatically determined. And when it determines with it being suitable, the quantitative analysis in this measurement wavelength is performed by a fixed_quantity | quantitative_assay step. For this reason, after setting the analysis target sample and the standard sample in the apparatus and setting the analysis conditions, the quantitative value of the target element can be obtained without examination or operation by the analyst. In addition, since the quantitative wavelength is determined based on the result of the total element qualitative analysis without performing the conventional multiple wavelength qualitative analysis, highly accurate quantitative analysis can be performed in a short time.

An ICP emission spectroscopic analyzer according to the second aspect of the present invention, which has been made to solve the above problems,
Excitation means for exciting a sample to emit light having a wavelength unique to the element contained in the sample, spectroscopic means for wavelength-dispersing the light, and a photodetector for detecting wavelength-dispersed light that has passed through the spectroscopic means, In an ICP emission spectroscopic analysis apparatus comprising:
a) wavelength scanning means for changing the wavelength of the chromatic dispersion light reaching the light receiving surface of the photodetector;
b) control means for controlling the wavelength scanning means based on the analysis sequence;
And the analysis sequence is
A qualitative step of measuring spectral lines at each wavelength position corresponding to each of a plurality of elements in advance for the sample to be analyzed;
A quantification step of measuring spectral lines at a plurality of measurement wavelength positions corresponding to the target element for a standard sample containing the analysis target sample and the target element at a known concentration;
It is characterized in that it is executed.

  Here, the quantitative step may be performed after or before the qualitative step. According to the ICP emission spectroscopic analyzer according to the second aspect of the present invention having the above-described configuration, the measurement for all element qualitative analysis is performed by the qualitative step, and the measurement for quantitative analysis at a plurality of wavelengths is performed by the quantification step. After setting and setting the analysis conditions, measurement data for both qualitative analysis for examination and quantitative analysis at a plurality of wavelengths can be acquired without bothering the analyst. Therefore, as compared with the case where the measurement operation is performed three times as in the conventional analysis procedure shown in FIG. 8, significant labor saving is possible. Further, unlike the conventional analysis procedure shown in FIG. 9, information necessary for selecting the optimum wavelength can be obtained, so that the optimum wavelength for quantitative analysis can be easily determined even by a skilled analyst.

  In general, in an ICP emission spectroscopic analyzer, there are many types of elements to be measured, and the wavelength range is very wide (for example, 160 nm to 850 nm). In the full wavelength qualitative analysis, it is necessary to rotate the diffraction grating so as to scan the entire range of this wide wavelength range. For example, an enormous measurement time is required to achieve an S / N ratio equivalent to that of the quantitative analysis. Become. On the other hand, if the diffraction grating is driven at a high speed and the sampling time at each wavelength position is shortened, the measurement time can be shortened. However, since the S / N ratio and the analysis accuracy are extremely lowered, it is not an effective means. .

Therefore, the ICP emission spectroscopic analysis apparatus according to the first aspect or the second aspect of the present invention is as follows.
The spectroscopic means is a sequential type spectroscope including an entrance slit, a wavelength dispersion element that wavelength-disperses light incident through the entrance slit, and an exit slit that extracts light of a specific wavelength out of the dispersed light to the outside. And
a) A first slit opening having an opening width with a wavelength resolution of 0.1 nm to 1.0 nm and a second slit opening having an opening width smaller than the first slit opening are provided apart from each other in the wavelength dispersion direction. An exit slit formed,
b) slit driving means for moving the exit slit in the wavelength dispersion direction;
Have
In the qualitative step, measurement is performed in a state where the first slit opening is disposed on the optical axis of light from the wavelength dispersive element to the photodetector, and in the quantification step, the second slit opening is disposed on the optical axis. It is desirable to perform measurement in a state where the is placed.

The wavelength resolution Δλ in the spectroscopic part of the ICP emission spectroscopic analyzer is obtained by the following equation (1).
Δλ = D × w (1)
Here, D is the inverse dispersion, and w is the opening width of the exit slit. The inverse dispersion D is a wavelength difference per unit length on the exit slit surface, and is obtained by the following equation (2).
D = cosβ / (N × m × f) (2)
Where β is the diffraction angle, N is the number of engraving lines of the diffraction grating, m is the diffraction order, and f is the focal length of the spectrometer.

  Conventionally, the opening width of the exit slit is generally set so that the wavelength resolution Δλ represented by the above formula (1) is about 0.01 nm, and even if the opening width is large, the wavelength resolution is at most 0. It was set to be about 0.05 nm or less. The ICP emission spectroscopic analysis apparatus of the present invention having the above-described configuration includes a first slit opening having a width of 10 times or more of the conventional general slit opening, and a second slit opening having a smaller opening width than that, It can be used by switching between the two. The second slit opening has a conventional general opening width. For example, it is desirable that the second slit opening has an opening width with a wavelength resolution of 0.05 nm or less. According to the first slit opening described above, the amount of light and the wavelength range that can be captured at one time are greatly expanded as compared with the conventional slit opening. Qualitative analysis can be performed quickly. In the analysis using the first slit opening, the wavelength resolution is lowered by widening the slit width than before, but the measurement in the qualitative step is performed in order to examine the conditions of the quantitative analysis. Since the required wavelength resolution is lower than the measurement in the quantification step (measurement for quantitative analysis), there is no particular problem.

  As described above, according to the ICP emission spectroscopic analysis apparatus according to the present invention, highly accurate quantitative analysis can be performed in a short time, and accurate quantitative results can be easily obtained without being a skilled analyst. It becomes possible.

1 is a schematic configuration diagram of an ICP emission spectroscopic analyzer according to an embodiment of the present invention. It is a top view of the exit slit vicinity in the ICP emission-spectral-analysis apparatus of the embodiment, (a) shows the state at the time of all element qualitative analysis, (b) shows the state at the time of quantitative analysis. It is a front view of the said exit slit, (a) shows the state at the time of all element qualitative analysis, (b) shows the state at the time of quantitative analysis. The flowchart which shows the analysis sequence in the embodiment. The flowchart which shows the determination procedure of the measurement wavelength in the said analysis sequence. The flowchart which shows the outline | summary of the other analysis procedure using the ICP emission-spectral-analysis apparatus based on the embodiment. The top view which shows schematic structure of the light emission part and spectroscopic part in the conventional ICP emission-spectral-analysis apparatus. The flowchart which shows an example of the analysis procedure by the conventional ICP emission-spectral-analysis apparatus. The flowchart which shows the other example of the analysis procedure by the conventional ICP emission-spectral-analysis apparatus.

  Hereinafter, an embodiment of an ICP emission spectroscopic analyzer according to the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing a schematic configuration of the ICP emission spectroscopic analyzer of the present embodiment. 7 that are the same as or correspond to those in the configuration shown in FIG.

  The ICP emission spectroscopic analyzer of the present embodiment includes a light emitting unit 10, an autosampler 20, a spectroscopic unit 30, a detection unit 40, a data processing unit 50, and a control unit 60, and a sample supplied from the autosampler 20. The solution is atomized by a nebulizer (not shown) and then introduced into the light emitting unit 10 and excited by a plasma flame. The light generated at this time is condensed by the condensing lens 31 and enters the spectroscopic unit 30 and is irradiated to the entrance slit 32. The light split in the spectroscopic unit 30, passes through the exit slit 38, and is introduced into the detection unit 40 is detected by a detector 41 including a photomultiplier tube and the detection signal is sent to the data processing unit 50. Sent.

  The data processing unit 50 converts the detection signal into digital data (emission spectrum data), stores it in the spectrum data storage unit 72, and performs arithmetic processing according to a predetermined algorithm, thereby executing qualitative analysis and quantitative analysis of the sample. Therefore, the data processing unit 50 includes a qualitative analysis processing unit 51, a quantitative analysis processing unit 52, a qualitative database 53, a calibration curve storage unit 54, and a determination unit 55 as functions. Operations of the data processing unit 50 and other units are controlled by the control unit 60 in an integrated manner. The control unit 60 controls the respective units according to the analysis sequence stored in the analysis sequence storage unit 71 to execute predetermined measurement and data processing. Many of the functions of the control unit 60 and the data processing unit 50 are achieved by executing predetermined computer programs on a general-purpose personal computer 80. The personal computer 80 is connected to an input unit 81 including a keyboard for an operator to input analysis conditions and the like, and a display unit 82 including a display for displaying measurement results and the like.

  In the ICP emission spectroscopic analysis apparatus according to the present embodiment, the second slit opening 38b having a conventional general opening width (for example, 30 μm) and the opening width (for example, 10 times or more) on the outlet slit 38 of the spectroscopic unit 30 (for example). 500 μm) are arranged side by side in the wavelength dispersion direction (FIGS. 2 and 3), and these can be used by switching appropriately.

  A mask 37 is provided in front of the exit slit 38. As shown in FIGS. 2 and 3, when the first slit opening 38a is used, the mask 37 blocks light from entering the second slit opening 38b (that is, the second slit opening 38b is invalidated), and the second slit opening 38a is used. When the slit opening 38b is used, the mask 37 blocks light from entering the first slit opening 38a (that is, the first slit opening 38a is invalidated).

  The spectroscopic unit 30 includes a diffraction grating drive motor (not shown) for rotationally driving the planar diffraction grating 34 and an exit slit drive motor (not shown) for reciprocatingly driving the exit slit 38. The operation is controlled by the control unit 60. In this embodiment, the moving direction of the exit slit 38 at the time of wavelength scanning coincides with the moving direction of the exit slit 38 at the time of slit switching (the direction of arrow S in FIG. 1). Both are performed using an exit slit drive motor.

  The diffraction grating drive motor and the exit slit drive motor are stepping motors, and rotate by an angle corresponding to the number of drive pulse signals given from the control unit 60, respectively. A reduction mechanism using a sine bar mechanism or the like is provided between the diffraction grating drive motor and the planar diffraction grating 34, and the planar diffraction grating 34 is rotated by an angle corresponding to the rotation angle of the motor. The drive mechanism of the exit slit 38 includes a rotation-linear motion conversion mechanism and the like, and moves the exit slit 38 by a distance corresponding to the rotation angle of the motor.

  Next, a characteristic analysis operation in the ICP emission spectroscopic analysis apparatus of the present embodiment will be described.

  First, an analyst attaches to the autosampler 20 a sample to be analyzed and a standard sample for creating a calibration curve containing a target element (element to be quantified) at a known concentration. Subsequently, the input unit 81 is operated to designate an analysis sequence as shown in FIG. 4 from among various analysis sequences stored in advance in the analysis sequence storage unit 71. FIG. 4 shows an outline of an analysis sequence used in the quantitative analysis in the present embodiment. As shown in the figure, this analysis sequence sequentially executes total element qualitative analysis (step S100), measurement wavelength determination (step S200), and quantitative analysis (step S300).

  Furthermore, the person in charge of analysis operates the input unit 81 to specify the type of the target element, the desired measurement accuracy (lower limit of quantification), and the measurement wavelength of each element in the all-element qualitative analysis. The measurement wavelength of each element may be stored in advance on the apparatus side. Further, although it is common to specify one measurement wavelength for each element in the qualitative analysis for all elements, a plurality of wavelengths may be specified for one element here.

  When the setting of analysis conditions is completed as described above and the analyst instructs the start of analysis from the input unit 81, analysis according to the above analysis sequence is started. First, a total element qualitative analysis is performed under the control of the control unit 60 (step S100). Specifically, the control unit 60 controls the exit slit drive motor (not shown) to move the exit slit 38 and arrange the first slit opening 38a on the optical path. In synchronization with the slit switching, the sample to be analyzed is introduced from the autosampler 20 into the plasma torch of the light emitting unit 10, and the emitted light from the sample to be analyzed excited is emitted to the spectroscopic unit 30.

  In the spectroscopic unit 30, the excitation light is wavelength-dispersed by the plane diffraction grating 34 and sent to the exit slit 38. A mask 37 is installed immediately before the exit slit 38. At this time, as shown in FIGS. 2A and 3A, the window (opening) of the mask 37 and the first slit opening 38a are arranged on the optical axis 90 in the front-rear direction. Only the light projected onto the detector 41 can reach the detector 41. On the other hand, at this time, the second slit opening 38b is hidden behind the mask 37 and becomes invalid.

  Then, the control unit 60 controls the diffraction grating drive motor, and rotates the planar diffraction grating 34 to perform wavelength scanning. Here, the position of the exit slit 38 is fixed, and only wavelength scanning by the planar diffraction grating 34 is performed.

  As described above, the first slit opening 38a has an opening width of 10 times or more compared with a slit opening having a general width such as the second slit opening 38b. 10 times or more. For this reason, the time required for the wavelength scanning is 1/10 or less. Furthermore, since the amount of light taken in at a time in the first slit opening 38a is 10 times or more that of the prior art, a high S / N ratio can be achieved. Further, even if the sampling time is set to 1/10, an S / N ratio almost equal to the conventional one can be obtained, so that the wavelength scanning time is reduced to about 1/100 of the conventional one while maintaining the conventional S / N ratio. It is also possible to shorten it.

  The spectrum data obtained by the above wavelength scanning is stored in the spectrum data storage unit 72. The qualitative analysis processing unit 51 reads spectrum data (luminescence intensity) at the wavelength position corresponding to each element, and calculates an approximate concentration, that is, a semi-quantitative value with reference to calibration curve information stored in the qualitative database. The calibration curve information is calibration curve data created by measuring a solution containing a single element at a predetermined concentration in advance under standard analysis conditions, and is registered in the qualitative database 53 at the time of factory shipment. . Further, calibration curve information created by an analyst using a standard sample having an arbitrary concentration may be registered in the qualitative database 53.

  Subsequently, the control unit 60 causes the determination unit 55 to determine the measurement wavelength (step S200). This is to determine whether or not a predetermined measurement accuracy can be achieved when quantitative analysis of the target element is performed at the measurement wavelength position of the target element in step S100. For the evaluation of the measurement accuracy, a method as already proposed by the present applicant in Japanese Patent Application Laid-Open No. 2006-275892 can be used. Hereinafter, this measurement accuracy determination method will be described in detail with reference to FIG.

  Now, an all-element qualitative analysis is performed on the sample to be analyzed. As a result, the spectral data storage unit 72 of the data processing unit 50 stores spectral line data at the measurement wavelength position corresponding to each element. As described above, in this apparatus, such a spectrum can be acquired in a much shorter time than a conventional apparatus having a slit having a general opening width.

  The qualitative database 53 includes, for each of various elements, a measurement wavelength position for measuring a spectrum line by the element, an interference correction coefficient indicating the type of interference element at each measurement wavelength position and the degree of spectral interference, Are stored in a database for easy retrieval. Since this qualitative database 53 is unique to each model, it is created based on data measured using this ICP emission spectroscopic analyzer.

  First, the control unit 60 instructs the determination unit 55 to start evaluation. Upon receiving this instruction, the data processing unit 50 satisfies a predetermined number of elements satisfying a predetermined standard for the semi-quantitative value obtained in step S100, for example, a predetermined number of elements in order from the highest concentration in the sample to be analyzed, and a target element. An element or the like whose concentration ratio to or above is a predetermined value or more is specified as a main component element of the sample to be analyzed (step S201).

  Subsequently, the determination unit 55 refers to the qualitative database 53 and reads the interference correction coefficient of the main component B at the measurement wavelength position λa of the target element A (step S202). When there are a plurality of measurement wavelength positions corresponding to the target element A (that is, when measurement is performed by specifying a plurality of wavelengths for the target element in step S100), for example, in descending order of intensity, or detection lower limit May be selected one by one in a predetermined order, such as in ascending order.

  Thereafter, the spectrum intensity Is at the measurement wavelength position λa is acquired from the data stored in the spectrum data storage unit 72 (step S203), and background correction is performed on the spectrum intensity Is to remove the background noise. Is ′ is calculated (step S204). For example, when the spectrum of the intensity Is exists at the wavelength measurement position λa, the intensity value Is ′ = Is−Ib obtained by subtracting the background intensity Ib is obtained by performing the background correction.

  Note that when performing background correction, it is necessary to determine the background position, and it is necessary to set the same wavelength position as the background position for all elements measured in one analysis. In general, such a position is often manually set by an expert, but here, it is preferable to use a method already proposed by the present applicant in Japanese Patent Laid-Open No. 2006-258633. According to this method, since the background position common to all elements is automatically determined, it is suitable for the automatic determination as in the present embodiment without bothering the analyst in the middle.

  Next, the spectrum intensity Isj at the measurement wavelength position λb of the main component element B is acquired from the data stored in the spectrum data storage unit 72 (step S205), and the same method as in the above step S204 is obtained. In step S206, the background value is corrected to calculate the intensity value Isj ′ from which the background noise has been subtracted. For example, when the spectrum of the intensity Isj exists at the wavelength position λb, the intensity value Isj ′ = Isj−Ibj obtained by subtracting the background intensity Ibj is obtained by performing the background correction.

  Thereafter, by multiplying the intensity value Isj ′ of the main component B after background correction by the interference correction coefficient, the amount of interference included in the intensity value Is ′ of the target element A after background correction at the measurement wavelength λa is calculated. (Step S207). Then, the obtained interference amount is multiplied by a predetermined coefficient P1, and the measurement accuracy when the inter-element correction is not performed is obtained from the value and the intensity value Is' of the target element A after the background correction (step S208). Then, it is determined whether or not the necessary measurement accuracy is obtained (step S209). If it is determined that the required measurement accuracy is obtained, inter-element correction and searching for another spectrum of the target element A are not necessary, and the process proceeds to step S300 to perform quantitative analysis.

  When performing quantitative analysis, first, the control unit 60 controls the exit slit drive motor to move the exit slit 38 and arrange the second slit opening 38b on the optical path. In synchronization with the slit switching, the standard sample is introduced from the autosampler 20 into the plasma torch of the light emitting unit 10, and the emitted light from the excited standard sample is introduced into the spectroscopic unit 30.

  In the spectroscopic unit 30, the excitation light is wavelength-dispersed by the plane diffraction grating 34 and sent to the exit slit 38. At this time, as shown in FIG. 2B and FIG. 3B, the window (opening) of the mask 37 and the second slit opening 38b are lined up and down on the optical axis 90. Only the light projected onto the detector 41 can reach the detector 41. On the other hand, at this time, the first slit opening 38a is hidden behind the mask 37 and becomes invalid.

  Then, the planar diffraction grating 34 is rotated so that the light having the measurement wavelength λa of the target element is irradiated to the second slit opening 38b, and then the second slit is formed as shown in FIG. By moving the opening 38b within the window of the mask 37, wavelength scanning before and after the measurement wavelength λa is performed.

  The spectrum data obtained by the above wavelength scanning is stored in the spectrum data storage unit 72. Then, the quantitative analysis processing unit 52 extracts the emission intensity at the measurement wavelength λa from the spectrum data, creates a calibration curve indicating the relationship between the emission intensity and the concentration of the target element, and stores it in the calibration curve storage unit 54. .

  Next, the autosampler 20 selects a sample to be analyzed and introduces it into the light emitting unit 10, and performs wavelength scanning before and after the measurement wavelength λa in the same manner as described above. The spectrum data thus obtained is stored in the spectrum data storage unit 72. Then, the quantitative analysis processing unit 52 extracts the emission intensity at the measurement wavelength λa from the spectrum data, refers to the calibration curve stored in the calibration curve storage unit 54, the concentration of the target element A in the analysis target sample, That is, a quantitative value is calculated. And the control part 60 receives the calculation result of the said quantitative value, outputs it to the display part 82 so that this may be displayed, and complete | finishes a process.

  On the other hand, if it is determined in step S209 that the required measurement accuracy is not obtained, it is next determined whether or not the target element A has a measurement wavelength position other than the previous measurement wavelength position λa (step S210). ). If there are measurement wavelength positions other than those that have already been evaluated, there is a possibility that a measurement wavelength position where the influence of spectral interference due to interfering elements is small compared to performing inter-element correction may be found. The measurement wavelength position is changed, the process returns to step S203, and the processes of steps S203 to S210 are repeated.

  If it is determined in step S210 that there is no other measurement wavelength position, inter-element correction must be performed. Therefore, the obtained interference amount is usually multiplied by a predetermined coefficient P2 different from the previous coefficient P1, The measurement accuracy when inter-element correction is performed from the value and the intensity value Is ′ of the target element A after background correction is obtained (step S211). Then, it is determined whether or not the necessary measurement accuracy is obtained (step S212). If the required measurement accuracy is obtained, the concentration of the main component element B, which is the correction target element, and the calibration standard sample necessary to create the calibration curve are calculated as inter-element correction information. Is displayed on the display unit 82 (step S213), and the process is terminated. On the other hand, if the required accuracy cannot be obtained in step S212, the desired measurement accuracy cannot be obtained by either the selection of the measurement wavelength or the inter-element correction process. Step S214) The process ends.

  Here, the evaluation of the measurement accuracy in steps S209 and S212 will be described. For the analyst, measurement accuracy is the lower limit of quantification. The error factors that deteriorate the measurement accuracy in this apparatus are roughly divided into a variation error (reproducibility) that changes from measurement to measurement and a deviation from the true value that occurs almost constantly regardless of measurement. The influence of the spectral interference due to the main component element as described above is the latter. Ideally, the deviation is eliminated by executing inter-element correction, but a variation error remains.

In order to accurately evaluate the measurement accuracy due to the variation error after correction of the target element and the effectiveness of the correction, it is preferable to perform evaluation at each stage of correction. That is, the intensity Is ′ after background correction of the target element, the background intensity Ib during background correction of the target element, the intensity Isj ′ after background correction of the main element, and the background after background correction of the main element The five elements of the ground intensity Ibj and the interference correction coefficient Lj may be mutually evaluated as follows, for example.
(1) In order to evaluate the measurement accuracy of the target element, Is ′ / Ib is calculated, an evaluation coefficient K (K> 1) is set for this, and Is ′ / Ib> K, K ≧ Is ′ / It is determined whether the range is Ib> 1, 1 ≧ Is ′ / Ib> 1 / K, or 1 / K ≧ Is ′ / Ib.
(2) In order to evaluate the measurement accuracy of the main component element, Isj ′ / Ibj is calculated, and using the evaluation coefficient K, Isj ′ / Ibj> K, K ≧ Isj ′ / Ibj> 1, 1 ≧ Isj It is determined which of the ranges '/ Ibj> 1 / K and 1 / K ≧ Isj' / Ibj.
The above (1) and (2) are for evaluating the influence of errors caused by the background intensity on the intensity of the target element and the main element.
(3) Further, in order to evaluate the correction amount, Is ′ / Lj · Isj ′ is calculated, and an evaluation coefficient M (M> 1) is set for this, Is ′ / Lj · Isj ′> M, It is determined whether M ≧ Is ′ / Lj · Isj ′> 1, 1 ≧ Is ′ / Lj · Isj ′> 1 / M, or 1 / M ≧ Is ′ / Lj · Isj ′.

  Moreover, since the deviation from the true value is dominant in the measurement accuracy when correction is not performed, this cannot be compared with the variation error after correction as it is, so the former is replaced with the latter. That is, Ib ′ = Lj · Isj × N (N is a predetermined coefficient) that gives a variation error with a width equivalent to the deviation from the true value. Then, by Is / (Ib + Ib ′), it is possible to evaluate the influence of the error caused by (Ib + Ib ′) on Is ′. For such evaluation, an evaluation criterion may be determined based on a required value of measurement accuracy input in advance by an analyst, and it may be determined whether or not the evaluation criterion is exceeded.

  As described above, according to the ICP emission spectroscopic analysis apparatus according to the present embodiment, whether or not the measurement wavelength of the target element in the total element qualitative analysis is suitable for quantitative analysis following the execution of the total element qualitative analysis, That is, when quantitative analysis is performed at the measurement wavelength, it is automatically determined whether or not a predetermined quantitative accuracy can be achieved. And when it determines with it being suitable, this measurement wavelength is automatically set as a measurement wavelength at the time of quantitative analysis, and quantitative analysis is performed. In addition, when the target element is measured at a plurality of measurement wavelengths for all element qualities, a measurement wavelength that provides sufficient measurement accuracy is automatically selected as the measurement wavelength at the time of quantitative analysis. For this reason, after setting a sample and setting an analysis condition, a quantitative value can be obtained without any examination or operation by an analyst. In addition, it is not necessary to perform a multi-wavelength qualitative analysis as in the prior art, and wavelength scanning for the qualitative analysis of all elements can be performed in a short time by using a slit having a larger opening width. Therefore, highly accurate quantitative analysis can be performed in a short time. Furthermore, if it is determined that sufficient measurement accuracy cannot be obtained at the measurement wavelength at the time of all element qualitative analysis, the measurement accuracy when inter-element correction is performed is calculated, and sufficient measurement accuracy is achieved by the correction. If possible, the analyst is notified accordingly. When performing inter-element correction processing, it is necessary to measure a standard sample for calibration in order to perform high-precision correction. Since the device instructs whether a standard sample should be prepared, the work of the analyst is simplified and even an unskilled person can handle it.

  In the above description, the example in which the analysis is performed according to the procedure as shown in FIG. 4 when determining the concentration of the target element in the sample to be analyzed has been described. Instead, the analysis is performed according to the procedure as shown in FIG. May be. A portion indicated by a dotted line in FIG. 6 (that is, steps S400 and S500) is a step that is automatically executed on the apparatus side (that is, without an analyst's operation) according to the analysis sequence. As shown in the figure, this analysis sequence sequentially performs measurement for all element qualitative analysis (step S400) and measurement for quantitative analysis at a plurality of wavelengths (step S500).

In this case as well, as in the above example, the analyst sets the sample to be analyzed and the standard sample in the autosampler 20, and operates the input unit 81 to set analysis conditions. However, here, as analysis conditions, in addition to the measurement wavelength position of each element in the qualitative analysis of all elements and the type of target element, a plurality of wavelength positions (for example, λa ₁ , λa ₂ , λa ₃ Specify). Note that the measurement wavelength position of the target element in the qualitative analysis for all elements may be the same as or different from any of the measurement wavelength positions for quantitative analysis.

  Thereafter, when the analyst instructs the start of analysis, the outlet slit 38 of the spectroscopic unit 30 is switched to the first slit opening 38a and the sample to be analyzed is introduced into the light emitting unit 10 as described above. Then, wavelength scanning and measurement for all element qualitative analysis are performed, and the obtained spectrum data is stored in the spectrum data storage unit 72.

When the measurement for all element qualitative analysis is completed as described above, the exit slit 38 of the spectroscopic unit 30 is switched to the second slit opening 38b, and the standard sample is introduced into the light emitting unit 10. Then, by the rotation of the plane diffraction grating 34, the on the light measurement wavelength [lambda] a ₁ object element is to be irradiated to the second slit opening 38b, the range of the second slit opening 38b of the window of the mask 37 The wavelength scan before and after the measurement wavelength λa ₁ is performed. Similarly, wavelength scanning before and after λa ₂ and λa ₃ is also performed, and the obtained spectrum data is stored in the spectrum data storage unit 72.

Subsequently, the sample to be analyzed is introduced into the light emitting unit 10, and wavelength scanning before and after λa ₁ , λa ₂ , and λa ₃ is executed in the same manner. Then, the obtained spectrum data is stored in the spectrum data storage unit 72, and the process is completed. Here, the measurement for quantitative analysis is performed after the measurement for qualitative analysis of all elements, but the measurement for quantitative analysis may be performed first.

  According to such an analysis sequence, measurement for all element qualitative analysis and measurement for quantitative analysis at a plurality of wavelengths are continuously performed. Therefore, after setting a sample and setting analysis conditions, Measurement data for both the qualitative analysis for examination and the quantitative analysis at a plurality of wavelengths can be acquired without trouble. Therefore, as compared with the case where the measurement operation is performed three times as in the conventional analysis procedure shown in FIG. 8, significant labor saving is possible. Further, unlike the conventional analysis procedure shown in FIG. 9, information necessary for selecting the optimum wavelength can be obtained, so that the optimum wavelength for quantitative analysis can be easily determined even by a skilled analyst. Compared with the procedure shown in FIG. 9, the time required for measurement becomes longer by the total element qualitative analysis. However, as described above, this apparatus uses a conventional apparatus having a slit having a general opening width. Compared to the above, it is possible to perform the measurement for the total element qualitative analysis in a short time in each stage.

  When a series of processes according to the above analysis sequence is completed, the analyst operates the input unit 81 to instruct the calculation of the semi-quantitative value. Thereby, the spectrum data acquired in step S400 is read from the spectrum data storage unit 72 to the qualitative analysis processing unit 51. The qualitative analysis processing unit 51 extracts the emission intensity at the measurement wavelength position of each element from the spectrum data, and calculates the approximate concentration (semi-quantitative value) of each element in the analysis target sample with reference to the qualitative database 53. . The calculated semi-quantitative value is displayed on the display unit 82.

Subsequently, the analyst specifies the main component element in the analysis target sample with reference to the semi-quantitative value. Further, the analyst gives a predetermined instruction at the input unit 81 to display the spectrum data in the step S500, and the spectral interference caused by the main component element from the measurement wavelengths λa ₁ , λa ₂ , λa ₃ for the quantitative analysis. A wavelength (for example, λa ₁ ) that seems to have the least influence is selected (step S600). Thereafter, when the analyst designates the wavelength λa ₁ using the input unit 81 and instructs the calculation of the quantitative value, the emission intensity of the standard sample at the wavelength λa ₁ is extracted from the spectrum data acquired in step S500. A calibration curve showing the relationship between the emission intensity and the concentration of the target element is created. Subsequently, the emission intensity of the sample to be analyzed at the wavelength λa ₁ is extracted from the spectrum data acquired in step S500, and the concentration, that is, the quantitative value is calculated with reference to the calibration curve (step S700) and displayed. Displayed on the part 82.

  The semi-quantitative value calculation, the main component element identification, the optimum wavelength selection, and the quantitative value calculation as described above may be included in the analysis sequence. In this case, the method shown in the flowchart of FIG. 5 is applied to select the optimum wavelength. Thereby, after instructing the start of analysis, it is possible to obtain a quantitative value without bothering the analyst, and further labor saving can be achieved.

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to said embodiment, A change is accept | permitted suitably in the range of the meaning of this invention. For example, the ICP emission spectroscopic analysis apparatus according to the present invention may have a configuration in which a detector including a linear image sensor is provided instead of the exit slit 38, the mask 37, and the detector 41. According to such a configuration, the wavelength range that can be captured at once can be made wider than that of the conventional one. Therefore, as in the case of using the exit slit having a large opening width as described above, all element qualities can be obtained in a short time. Analysis becomes possible.

  In the above example, the sample is automatically replaced by the autosampler. However, the present invention is not limited to this, and when the sample needs to be replaced, the device displays a message to that effect on the display. The sampler may be manually exchanged by the analyzer.

DESCRIPTION OF SYMBOLS 10 ... Light emission part 20 ... Autosampler 30 ... Spectroscopic part 31 ... Condensing lens 32 ... Entrance slit 33 ... 1st concave mirror 34 ... Planar diffraction grating 35 ... 2nd concave mirrors 36, 38 ... Exit slit 37 ... Mask 38a ... 1st slit Opening 38b 2nd slit opening 40 Detection unit 41 Detector 50 Data processing unit 51 Qualitative analysis processing unit 52 Quantitative analysis processing unit 53 Qualitative database 54 Calibration curve storage unit 55 Determination unit 60 Control unit 71 ... Analysis sequence storage unit 72 ... Spectral data storage unit 80 ... Personal computer 81 ... Input unit 82 ... Display unit 90 ... Optical axis

Claims (3)

Excitation means for exciting a sample to emit light having a wavelength unique to the element contained in the sample, spectroscopic means for wavelength-dispersing the light, and a photodetector for detecting wavelength-dispersed light that has passed through the spectroscopic means, In an ICP emission spectroscopic analysis apparatus comprising:
a) wavelength scanning means for changing the wavelength of the chromatic dispersion light reaching the light receiving surface of the photodetector;
b) data processing means for generating emission spectrum data from the detection signal acquired by the photodetector and performing predetermined data processing based on the emission spectrum data;
c) a database that records information on the spectral interference that each element has on other elements for each element;
d) control means for controlling the wavelength scanning means and the data processing means based on the analysis sequence;
And the analysis sequence is
A qualitative step of measuring spectral lines at each wavelength position corresponding to each of a plurality of elements in advance for the sample to be analyzed;
Based on the measurement result in the qualitative step, the main component element in the sample to be analyzed is specified, and the interference amount of the main component element with respect to the spectral line of the target element from the measurement result in the qualitative step with reference to the database A determination step of determining whether a predetermined quantitative accuracy is obtained at the measurement wavelength position of the target element in the qualitative step based on the amount of interference;
Are sequentially executed, and when it is determined in the determination step that a predetermined quantitative accuracy is obtained,
For a standard sample containing the sample to be analyzed and the target element at a known concentration, a spectral line at a wavelength position determined to obtain a predetermined quantitative accuracy in the determination step is measured, and a calibration curve is obtained from the measurement result of the standard sample. A quantitative step for calculating a quantitative value of the target element from the measurement result of the sample to be analyzed with reference to the calibration curve,
An ICP emission spectroscopic analyzer characterized in that Excitation means for exciting a sample to emit light having a wavelength unique to the element contained in the sample, spectroscopic means for wavelength-dispersing the light, and a photodetector for detecting wavelength-dispersed light that has passed through the spectroscopic means, In an ICP emission spectroscopic analysis apparatus comprising:
a) wavelength scanning means for changing the wavelength of the chromatic dispersion light reaching the light receiving surface of the photodetector;
b) control means for controlling the wavelength scanning means based on the analysis sequence;
And the analysis sequence is
A qualitative step of measuring spectral lines at each wavelength position corresponding to each of a plurality of elements in advance for the sample to be analyzed;
A quantification step of measuring spectral lines at a plurality of measurement wavelength positions corresponding to the target element for a standard sample containing the analysis target sample and the target element at a known concentration;
An ICP emission spectroscopic analyzer characterized in that The spectroscopic means is a sequential type spectroscope including an entrance slit, a wavelength dispersion element that wavelength-disperses light incident through the entrance slit, and an exit slit that extracts light of a specific wavelength out of the dispersed light to the outside. And
a) A first slit opening having an opening width with a wavelength resolution of 0.1 nm to 1.0 nm and a second slit opening having an opening width smaller than the first slit opening are provided apart from each other in the wavelength dispersion direction. An exit slit formed,
b) slit driving means for moving the exit slit in the wavelength dispersion direction;
Have
In the qualitative step, measurement is performed in a state where the first slit opening is disposed on the optical axis of light from the wavelength dispersive element to the photodetector, and in the quantification step, the second slit opening is disposed on the optical axis. The ICP emission spectroscopic analysis apparatus according to claim 1, wherein the measurement is performed in a state in which the ICP is disposed.

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