JPH10281998A - Emission spectroscopic analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a more precise analytical result in a trace element analysis to which a time resolution light measurement method is applied when the element analysis is performed by spark-discharging a sample to emit a light, spectrally diffracting it by a diffraction grating, and detecting the spectrally diffracted light of each wavelength by a light detector. SOLUTION: This device is constituted so that an element analysis is performed by spark-discharging a sample to emit a light, spectrally diffracting the light by a diffracting grating, and detecting the spectrally diffracted light of each wavelength by a light detector. The light detector is formed of a one- dimensional, image sensor 11 . On the other hand, a timing control means 61 is provided so that an information reading transfer pulse ϕ is outputted to the one-dimensional image sensor 11 at a prescribed divided time from the spark discharge starting point to the spark discharge middle and at a prescribed time after the spark discharge is ended.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emission spectrometer for causing a sample to emit light by spark discharge and spectrally analyzing the sample for elemental analysis.

[0002]

2. Description of the Related Art As a conventional emission spectrometer of this type, there is one having a configuration for performing simultaneous multi-element analysis as shown in FIG.

In FIG. 1, a is a light source for spark discharge of a sample, b is a condenser lens, c is a vacuum chamber, d is an entrance slit, e is a diffraction grating, f is an exit slit, and g is a photomultiplier tube. , H are evacuation systems.

Then, the sample is caused to emit light by spark discharge in the light source a, and this light is condensed by the condenser lens b. Then, the light is separated into light having a wavelength corresponding to each element by the diffraction grating e through the entrance slit d. Then, each of the separated spectral lights is detected by each photomultiplier tube g through the exit slit f.

Here, when performing a trace analysis of a specific element,
It is necessary to improve detection sensitivity, and for that purpose, time-resolved photometry may be applied. In this time-resolved photometry, as a spark discharge condition, as shown in FIG.
The discharge areas S and A are changed by changing the discharge current so as to trail.
Measure the light intensity separately.

That is, for samples containing trace amounts of elements such as Al, P, C, etc., the lower limit of detection in the elemental analysis for the spark region S or the arc region A, respectively.
(Hereinafter referred to as BEC). For example, Al,
For each of the elements P and C, the BEC is better in the arc region A than in the spark region S. In this case, the arc region A is discharged after a predetermined time has elapsed from the discharge start point.
These trace elements are analyzed by measuring the light intensity at the time of.

[0007]

The conventional apparatus shown in FIG. 6 is a discrete measurement in which each photomultiplier tube g only receives spectral light of a specific wavelength after spectral separation.

On the other hand, a spectroscope using an image sensor as a detector can continuously and simultaneously measure all the wavelengths in a measurement area, so that simultaneous analysis of multiple elements and multiple wavelengths is possible.

It is an object of the present invention to provide a spectroscope having the above-described features, by applying time-resolved photometry, to obtain accurate analysis results in simultaneous multi-element, multi-wavelength analysis.

[0010]

According to the present invention, in order to solve the above-mentioned problems, a sample is caused to emit light by spark discharge, which is separated by a diffraction grating, and the separated light of each wavelength is detected by a photodetector. The following configuration is adopted in an emission spectrometer that performs elemental analysis by detecting in (1).

That is, in the invention according to claim 1,
The photodetector consists of a one-dimensional image sensor,
Timing control means for outputting a transfer pulse for reading information to the one-dimensional image sensor at a predetermined division time during the spark discharge from the spark discharge start point and at a predetermined time after the end of the spark discharge. I have.

Further, in the invention according to claim 2, the photodetector is constituted by a two-dimensional image sensor, and the two-dimensional image sensor is provided with a two-dimensional image sensor on the front surface or on the sensor. While an exit slit or mask having a window through which the light split into light is passed only to a part of the light receiving unit is arranged, within the time from the start of the spark discharge to the end of the spark discharge, for the two-dimensional image sensor, There is provided timing control means for outputting a transfer pulse having a constant period.

[0013]

Embodiment 1 FIG. 1 is a block diagram showing a main part of an emission spectrometer according to Embodiment 1 of the present invention.

In FIG. 1, reference numeral ₁₁ denotes a one-dimensional image sensor as a photodetector for detecting spectral light of each element separated by a diffraction grating (not shown).

That is, the one-dimensional image sensor ₁₁
It includes a light receiving portion 2 ₁ of the photoelectric conversion, consisting of the storage unit 4 ₁ Tokyo temporarily accumulates charges obtained by photoelectric conversion in the light receiving section 2 _1. Then, the light receiving unit 2 _1, the solid-state imaging device (hereinafter, C
CD) are arranged linearly, and have a length L sufficient to cover the entire wavelength range of the spectrum light of various elements required for measurement. The storage unit 4
₁ is constructed by arranging the same length fraction number of CCD with the light receiving portion 2 ₁ linearly.

[0016] 6 _1, predetermined division time of spark discharge way from spark discharge start point, and a predetermined time after the spark discharge end, with respect to one-dimensional image sensor 1 _1, respectively, the transfer pulse for reading information This is a timing control means for outputting.

[0017] 8 of the one-dimensional image sensor 1 ₁ storage unit 4 ₁
, An amplifier for amplifying the signal of the accumulated charges sequentially read out from the A / D
It is a converter.

[0018] 12 each time determining the output timing of the transfer pulse φ to the timing control means 6 ₁ T
f, Tl data is given in advance, and the A / D converter 1
A signal processing unit for processing a signal output of 0, for example, a microcomputer.

Next, the operation of the emission spectrometer according to the first embodiment for measuring the spectrum light of a trace element by applying the time-resolved photometry will be described with reference to the time chart of FIG.

[0020] First, the timing control circuit ₆₁ outputs a transfer pulse phi ₀ at a predetermined time t ₀ prior to initiation of the spark discharge in the one-dimensional image sensor 1 _1. This is because examining the accumulated charges based on unwanted dark current or the like existing in the previous state for receiving the spectral light of each element in the light receiving unit 2 _1, in order to eliminate the influence of the background.

Next, when a first spark discharge is started for the sample by a light emitting unit (not shown), the light emitted by the spark discharge is converted into a spectrum light having a wavelength corresponding to each element by a diffraction grating (not shown). The one-dimensional image sensor 1 separates the spectral light of each of the separated elements.
It is received by the _first light receiving portion 2 _1.

Further, the light of the igniter caused by the spark discharge is detected by the light receiving element such as a photodiode, the light detection signal is input to the timing control circuit 6 _1.

[0023] Depending on the input of the light detection signal, the timing control circuit _61, the predetermined middle spark discharge has elapsed predetermined time Tf by the signal processing section 12 from the discharge start point (time t ₁₎ When the division time t ₂ of
Outputs a transfer pulse φ _1. This transfer pulse φ _1,
Is dispersed during the period Tf from the discharge start point t ₁ to reach the split time t ₂ by a diffraction grating, not shown in the CC of the light receiving portion 2 ₁
Accumulated charge based on the spectral light of each element that is received by D is transferred to the storage unit 4 _1.

[0024] Incidentally, in the predetermined time period T ₀ to reach the split time t _2, the previously stored charge signal based on the dark current or the like before the spark discharge accumulated in the accumulating portion 4 ₁ is read out serially The signal is sent to the signal processing unit 12.

[0025] Then, the timing control circuit 6 _1,
When the split time t preset time by _second signal processing section 12 from Tl has elapsed reaches a predetermined time t ₃ after the spark discharge ends, again, it outputs a transfer pulse phi _2. The transfer pulse phi _2, received at the CCD light receiving portion 2 ₁ is dispersed by the unshown diffraction grating during Tl from dividing the time t ₂ until a predetermined time t ₃ after the spark discharge end accumulated charge based on the spectral light of each element is transferred to the storage unit 4 _1.

[0026] Note that the predetermined period T ₁ of the to reach the time t _3, sent already signal accumulation unit 4 accumulates electric charges stored in ₁ is read out serially toward the signal processing section 12 You.

Next, a predetermined time t ₃ after the end of the spark discharge
There after a lapse of the signals stored accumulated charges in the storage portion 4 ₁ is sent toward being serially read out to the signal processing unit 12 within a predetermined time period T _2.

The above operation is for the first spark discharge of the sample, but the same operation is repeated for the subsequent spark discharges.

The signal processing unit 12 calculates, for example, the data obtained in each period T _{0 to} T ₂ of each spark discharge, for example,
The following processing is performed.

First, the data obtained in the period T ₀ is subtracted from the data obtained in each of the periods T ₁ and T ₂ , based on the dark current and the like existing in the state before receiving the spectral light of each element. Excludes background effects.

Next, in consideration of the BEC of each element analysis, data obtained in a region Tf (period T ₁ ) or Tl (period T ₂ ) suitable for each element analysis is selected. Then, the light intensity of each spectrum light of each element at that time is measured, and these trace elements are analyzed.

[0032] At this time, the light receiving unit 2 _1, since a sequential measurements have a length L which can cover the entire wavelength range of the spectrum light of the various elements required for the measurement are shown in FIG. 7 In this way, the situation before and after the spectrum light (wavelength λ ₁ ) of a certain analysis target element can be grasped.
Therefore, even when there is spectral light (wavelength λ ₂ ) of another non-detection target element in the vicinity of the spectral light (wavelength λ ₁ ), it is possible to investigate the effect and correct the background. .

In the first embodiment, the transfer pulse φ ₀ is output each time before the start of each spark discharge, and the dark current and the like existing in the state before the spectral light of each element is received. However, the transfer pulse φ ₀ is output only during the first spark discharge, and for the subsequent spark discharge, the transfer pulse φ ₀ is omitted and other transfer is performed. Only the pulses φ ₁ and φ ₂ may be output.

Embodiment 2 FIG. 3 is a block diagram showing a main part of an emission spectroscopy analyzer according to Embodiment 2 of the present invention, in which parts corresponding to those of Embodiment 1 shown in FIG. .

In FIG. 3, reference numeral ₁₂ denotes a two-dimensional image sensor as a photodetector for detecting spectral light of each element separated by a diffraction grating (not shown).

That is, the two-dimensional image sensor 1 ₂
It includes a light receiving unit 2 _{and second} photoelectric conversion, a storage portion 4 ₂ that temporarily accumulates charges obtained by photoelectric conversion in the light receiving unit 2 _2,
A signal based on the accumulated charge of the storage portion 4 ₂ line by line consisting horizontal shift register 5 for outputting serially. Then, the light receiving unit 2 _2, a solid-state imaging device (hereinafter, CC
D) are arranged two-dimensionally, and have a width L sufficient to cover the entire wavelength range of the spectrum light of various elements required for measurement. The storage unit 4
_2, which are arranged the same number of CCD as the light receiving unit 2 ₂ two-dimensionally.

[0037] 3 is arranged an outlet slit in front of the two-dimensional image sensor 1 _2, the exit slit 3,
In Embodiment 2, as spectral spectrum light is irradiated only in a region corresponding to one line of the CCD in closest proximity to the two-dimensional image sensor 1 ₂ of the light receiving portion 2 _second accumulation unit 4 _2, the The width L ′ (≧ L) and the height H of the window hole 3a are set and arranged. Note that the spectrum light is received by the light receiving unit 2.
It is also possible to set the height H of the window hole 3a so as to irradiate an area corresponding to a plurality of lines of the _two CCDs.

Further, 6 ₂ in time from the spark discharge start until spark discharge end, the two-dimensional image sensor 1 ₂
Against a timing control means for outputting a plurality of times by time division transfer pulses from the light receiving portion 2 ₂ to the storage section 4 _2.

Reference numeral 8 denotes an amplifier, reference numeral 10 denotes an A / D converter, and reference numeral 12 denotes a signal processing unit. The basic configuration thereof is the same as that of the first embodiment shown in FIG. I do.

Next, the operation in the case where the spectral light of a trace element is measured by applying the time-resolved photometry in the emission spectrometer of the second embodiment will be described with reference to the time chart of FIG.

When the first spark discharge is started for the sample by the light emitting unit (not shown), the light emitted by the spark discharge is separated into spectral light having a wavelength corresponding to each element by the diffraction grating (not shown). , spectral light of each element is the spectral is received by the CCD of one line of the two-dimensional image sensor 1 ₂ of the light receiving section 2 ₂ through the window hole 3a of the exit slit 3. Further, the light of the igniter caused by the spark discharge is detected by the light receiving element such as a photodiode, the light detection signal is input to the timing control circuit 6 _2.

In response, the timing control circuit 6
_2, until it is time t ₅ the spark discharge is terminated after the lapse of a preset predetermined time Tr by the signal processing section 12 from the discharge start time t _4, a transfer pulse φ at a predetermined period ΔT And output them sequentially. Here, ΔT ≧ Tr
/ N (N is CCD number of lines constituting the light receiving section 2 _2).

[0043] Each time this transfer pulse phi are input to the two-dimensional image sensor 1 _2, during each period ΔT of the transfer pulse phi, received at the CCD for one line of the light receiving portion 2 ₂ accumulated charge based on the spectral light of each element is transferred to the storage section 4 _2.

[0044] Then, a first time the spark discharge is terminated, all charges to N lines of the storage portion 4 ₂ is accumulated, then, when a predetermined time t ₆ after the end of the spark discharge, accumulation signal parts 4 accumulated charge to ₁ is sent toward the sequentially read and the signal processing section 12 from the horizontal shift register 5 by one line within a predetermined time period Tt.

The above operation is for the first spark discharge of the sample, but the same operation is repeated for the subsequent spark discharges.

The signal processing unit 12 obtains information on the light intensity of the spectral light of each element by the number of times obtained by dividing the time period Tr of each spark discharge by the period ΔT of the transfer pulse φ, and analyzes each element. In consideration of B.E.C. of the case, as shown in FIG. 7, the data obtained in the region Tf (period T ₁ ) or Tl (period T ₂ ) suitable for the analysis of each element is selected. Then, the light intensity of each spectrum light of each element at that time can be measured.

[0047] Also in this embodiment 2, the light receiving unit 2 ₂ has a sequential measurements have a length L which can cover the entire wavelength range of the spectrum light of the various elements required for measurement since, as in the embodiment 1, even if the analysis subject to spectral light in proximity to (wavelength lambda ₁₎ other detected outside the elements of spectral light (wavelength lambda ₂₎ is present, its effect It is possible to examine and correct the background.

In the second embodiment, the transfer pulse φ is output at a predetermined period ΔT after the start point t ₄ of each spark discharge. However, similar to the first embodiment, the transfer pulse φ is output. It is also possible to output a transfer pulse once before the start of the discharge so as to eliminate the influence of the background based on the dark current or the like existing in the state before receiving the spectrum light of each element.

The two-dimensional image sensor 1 ₂ of FIG. 3 is corresponding to a frame transfer type CCD image sensor, instead of this, full-frame transfer type CCD
FIG. 5 is a block diagram when an image sensor is used.

The horizontal output the two-dimensional image sensor 1 _3, and the light receiver 2 ₃ for photoelectric conversion, a signal based on the accumulated stored charge after photoelectric conversion by the light receiving unit 2 ₃ serially line by line And a shift register 5.

What is different from the case of FIG.
Of the position of the window holes 3a, radiation only in a region where the spectral spectrum light corresponds to one line of the CCD farthest from the horizontal shift register 5 of the light receiving portion 2 ₃ of the two-dimensional image sensor 1 ₃ The width L 'of the window hole 3a.
(≧ L) and the height H are set and arranged.

[0052] Incidentally, CCD light-receiving section 2 ₃ spectrum light
It is also possible to set the height H of the window hole 3a so as to irradiate an area corresponding to a plurality of lines.

In FIG. 5, time-resolved photometry can be performed by performing measurement in the same procedure as in FIG.

[0054]

According to the present invention, the following effects can be obtained.

(1) In the invention according to the first aspect, when performing trace element analysis using time-resolved photometry, it is possible to effectively eliminate the influence of the background due to the presence of spectral light of unnecessary elements that are not analyzed. As a result, analysis results with higher accuracy than before can be obtained.

(2) In the invention according to the second aspect, in addition to the effect according to the first aspect, the division time can be arbitrarily changed for each element even after the measurement, so that the B when analyzing each element can be changed. It is possible to select data obtained in an optimal division time in consideration of the EC, and to further improve the analysis accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a main part of an emission spectrometer according to a first embodiment of the present invention.

FIG. 2 is a time chart for explaining the operation when measuring the spectral light of a trace element by applying the time-resolved photometry in the apparatus of Embodiment 1 of FIG. 1;

FIG. 3 is a block diagram showing a main part of an emission spectrometer according to Embodiment 2 of the present invention.

FIG. 4 is a time chart for explaining the operation when measuring the spectral light of a trace element by applying the time-resolved photometry in the apparatus according to the second embodiment in FIG. 3;

FIG. 5 is a block diagram showing a modification of the present invention.

FIG. 6 is a diagram showing a configuration of a conventional emission spectrometer.

FIG. 7 is an explanatory diagram showing spark discharge conditions when applying time-resolved photometry.

[Explanation of symbols]

1 ₁ : one-dimensional image sensor, 1 ₂ ... two-dimensional image sensor, 2 ₁ , 2 ₂ ... light receiving section, 4 ₁ , 4 ₂ ... storage section, 3 ... exit slit, 3a ... window hole, 5 ... horizontal shift register, 6 ₁ , 6
₂ ... timing control circuit, 12 ... signal processing unit.

Claims (2)

[Claims] 1. An emission spectrometer for performing spark discharge on a sample to emit light, separating the light by a diffraction grating, detecting the separated light of each wavelength with a photodetector, and performing elemental analysis. While the device is constituted by a one-dimensional image sensor, at a predetermined division time during the spark discharge from the spark discharge start point, and at a predetermined time after the end of the spark discharge,
An emission spectrometer comprising: a timing control unit that outputs a transfer pulse for reading information to each of the one-dimensional image sensors. 2. An emission spectroscopy apparatus for emitting light by spark discharge of a sample, separating the light by a diffraction grating, and detecting the separated light of each wavelength by a photodetector to perform elemental analysis. The two-dimensional image sensor is constituted by a two-dimensional image sensor, and for this two-dimensional image sensor, a window hole for transmitting light dispersed only to a part of a light receiving portion of the two-dimensional image sensor on the front surface or on the sensor. While the outlet slit or mask having the above is arranged, the apparatus further comprises timing control means for outputting a transfer pulse having a constant cycle to the two-dimensional image sensor within a time period from the start of the spark discharge to the end of the spark discharge. Emission spectrometer.