JPH04148830A - Multiple-component determining method in spectrochemical analysis - Google Patents

Abstract

PURPOSE:To suppress the interference between noises and components by individually performing analysis for every component based on the sum of the relative absorbances which are the differences between the local peak values and the local base values in a region wherein frequency spectrums are determined beforehand. CONSTITUTION:An infrared beam is emitted from a light source 4 on a cell 9. The interferogram of a comparing sample and a measured sample is measured, and the frequency spectrum is obtained. The interferogram undergoes Fourier transformation, and the power spectrum is obtained. Then, the ratio of the power spectrum of a background to the power spectrum of the measured sample is obtained. The ratio is converted into the absorbance scale, and the frequency spectrum is obtained. The frequency points of the local peak and the local base are determined in the frequency spectrum beforehand. The concentration of each component is obtained based on the component spectrum obtained by using the sum of the relative absorbances. The absorbance is obtained based on the difference between the absorbances at the peak and the base.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention irradiates a sample with, for example, infrared light from a light source, and detects the amount of polycarbonate contained in the sample based on the frequency spectrum obtained at that time. Concerning a method for quantifying components.

C. Prior Art] In general, quantitative analysis using an infrared absorption spectrum (frequency spectrum) is performed using Langhart-Hehr's law, which states that absorbance is proportional to the concentration of an absorber. This relationship can be expressed as follows for a certain absorber.

A(ν>=Cα(ν) ・・・・・・(1
) Here, A(ν) is the frequency spectrum of a certain concentration, C
is its concentration, α(ν) is the frequency spectrum of unit concentration, and a schematic example of such a relationship is shown in FIG. In this figure, the curve I represents the spectrum I-le α(ν) of a unit concentration, and the curve If +j represents the frequency spectrum A of a certain concentration.
(ν) (=Cα(ν))].

If the absorption of multiple components is superimposed,
-Equation (1) above is A(ν)-Σr Ciα, (ν)...(
2) is expressed as a simple linear combination. Here, C8 is 19. 1 degree, α, (+I) that is λJ to its component is the frequency spectrum of the intermediate concentration for each component.

-・In the boat fishing multi-component quantitative method, each t+,
Obtain in advance the reference same-wavenumber vector I·le α, (ν) for the component of , and convert the frequency spectrum of the unknown mixture to be measured from (ν) to 0. It is estimated that

Usually, △(ν) is expressed as 2 (() as a series of values at wavenumber points in the mid-infrared region, so the above (2) is A(ν
,)-Σi Ci o' i (IJ)...
・(3) A system of the form ・) is expressed by the following equation.

9th line 1 shows a schematic superposition of two component frequency scales, and in this figure, curves 1. II is the frequency spectrum α1(IJ) of the unit concentration of each gas,
α2(νj) and the curve I'llLJ are linear combinations of their spectra.Equation (3) is shown.

[Problem to be solved by the invention] Then, in formula (3) Is, if j>1, the observed A(IJ) is larger than the known α, (IJ). 01 by method 6 such as least multiplication method or factor IJi′.
(11). These methods are widely used and are readily available as commercially available soft 1" barriers, or the wavenumber points ν used in the analysis can be
, Continuous N4> Surrounding 4II Near JL, there are two drawbacks, 1, 1.

In other words, when dealing with a spectrum with a resolution of 0.016),
”, the amount of data used in calculations becomes enormous, ■
There is a drawback that the estimation error is large compared to the baseline change +) + 11-type disturbance (1).

The present invention has been made with the above-mentioned problems in mind, and its purpose is to perform analysis at 1E61'N without being affected by noise and interference effects between components. Can you do it? ) The object of the present invention is to provide a method for quantifying multiple components that can be applied to spectroscopy.

[Means for solving the problem] In order to achieve the above-mentioned object, the spectral spectral power ζ according to the present invention
The multi-component quantification method in
The frequency points of the local peak and the local Heath for each absorption of the above-mentioned number components are determined, and each is obtained by using the sum of the relative absorbance obtained from the difference in the absorbance of the beam and the base. From the component subscale 1-rule, 1); for the multiple components -C reference 1 (obtained from the frequency spectrum 11). In order to obtain the concentration of each of the above components separately (there is a characteristic in this point).

[Operation] In the method of the present invention having the characteristic configuration described in L, the relative absorbance is determined by the difference between the local peak value and the local . What are the component sums obtained by calculating the sum of each component (<71) and the ignition component spectrum for each component? At E-J, each component is analyzed individually.
l, (under the influence of 1-interference of LN and substitution 1-, i1' is quantified to 11'?l xZ6 is C cut.

(Example) 1'2F, - Refer to Drawing 5-1 for an example of the invention 1 bar.
Explanation from ic.
An example is schematically shown in Figure 8, 2 (L through), 1 is de'll R (furino', conversion red (line analyzer),
It consists of a data processing section 3 that processes the analysis fjlj2 and the outputs of the analysis section 2, i.e., +11g).

At that point, the analysis unit 2 emits parallel red light 1,) (with the two light sources 4,) f-1,
7ri! i solid) J-(miu-(j, from the movable Mi'y-7, etc., l?jI-machine +M +:+, which accommodates the measurement sample, etc., and receives the red light from the light source 4 via the interference mechanism 8. ri4.)-
--M ill: (!i = 1, cell 9, ゛t',
The detector 110 is composed of a conductor detector or the like.

Further, the data processing section 3 calculates, for example, isotar=)dou-logura J, addition average A, addition average processing section +1. :: A high-speed Foury 1 transform processing section 12 that performs Sory transformation on the output data from the addition q' equalization processing section 11 at high speed. This high speed
'-Lini 1' The output data from the conversion processing unit I2 is (
Regarding the components to be measured,
Line 17・) -人BE・'ノ[・! [/Ii! , i I
J-GoB13) Bao 1 and 2〉Kyu-J\re-112-iro.

1. Although not shown in the figure, - the above-mentioned FT-II IC
is provided with a drive mechanism for driving the movable mirror 5 in the X-V direction, for example, and a drive mechanism for driving the moving mirror 5 in the X-V direction, and also for driving the drive mechanism and the processing units 11 to 11 of the data processing unit 3. 1
A controller is provided to control 3).

Therefore, F l”-I RI composed of
According to the method, the cell 9 accommodates a comparative Ω'·1 or a measurement sample, respectively, and light l! , 4 is irradiated onto the cell 9, and the interfacial loghum of the comparison sample and the measurement sample are measured. Then, after Fourier transforming each of these interferograms to obtain a power spectrum, find the ratio of the power spectrum of the measurement sample to the Hank Graun power spectrum, and convert this into an absorbance scale. The frequency spectrum can be obtained by

Here, to explain the sum of relative absorbance in the basket,
The frequency spectrum output from a spectrometer generally contains noise due to various causes, and therefore, the above equation (1) i'', AC+・, )−Cα (ν,)−
g ε , ... ... (4
). -C5ε is the noise included in the spectrum.

Then, the difference between any two points in the spectrum is 7''l]
Then, the above equation (4) becomes A(νi)−A(νb)−=C(α(ν1.) α(
ν, ) ] ] 162−ε, ...(5) It is shown that the relative absorbance between two points like 1:1 also obeys Langhart-Heer's law. . Here, p, l)L; l are subscripts indicating the peak and base wavenumber points, respectively.

Usually, the frequency spectrum of substances, especially the spectrum of gases [
It is possible to select many pairs of peaks 1 and bases ν that are specific to a certain substance, including many peaks.

Figure 6 shows a schematic spectrum of dregs and its relative absorbance.1. ,．． 2. An example of 1=1 is shown.

The relative absorbance of each of the above...! -2,1,,,
, 3 correspond to the value of equation (5) above.

(taking the direct sum, Σ□(A(νp)-A(ν4,))]3 CΣk[α(shiba-α(νJlb"+-Σ3(C2-C
1,)k...(6) This formula (6) also complies with Ranhart-Heer's law. Therefore, from this (6) 2, the second right side
The term averages the noise that is latent in the spectrum L2, and the 1 of - Snow In.
” IJ -) Cancel the disturbance of l, I, Una (
,7.

) - Expression (6) below, calculate the value of Jl, MAS
(Mu 1Tiple Absorption 5
LIIN) (Defined as direct.

Zuna Sai) ζ), MAS knee Σ, [A(ν i) A(v,,
)] 5 ... ... (7).

Zoshi” (Kitsunetoku (, ko, condolence - the reference source of known concentration of ingredients (
ri[-ruby, for r: search/reda M, AS hani as -, component 1 (1 kochi/earth) t4, to S.

Next 1. 2. For each component, specify the wavenumber point of 1-°- and the wavenumber point of -s, peak, \-=-s pair). ν11) 4, prepared Jl
Figure 7 shows an example of specifying wavenumbers for three gas species Q. In this figure, curve 1. Il, TRI are The reference values for gases X, Y, and Z are shown respectively.

Then, the set Φy for gas X: (X,, X
b) + = set (1) for gas Y, ・(”i', ,
Y, ), the set Φ, for the gas Z, ! :(Zp, Z,,
), is specified.

Specify these peaks -\-s) 1'□! In this case, it is preferable to use C□2 so as to obtain as large a relative absorbance as possible and not be influenced by each other's absorption.

Ordinance, supra. 1', U4I: Set of wave number point specified values as I'
For n components C02, +11. (i = I-m)
Then, for the absorption spectrum A of -2, the i7- combination of the component lonopi, ri -, -s pair is expressed as Defined as −1ru4, >:, [A(t〆 1,)−Δ(ν 1,):l
,=,toQ fl) i...(8),'25. 'te, ◎ is nail-biting 1iii'c'', i' is (
8) Equation 1: , U M A S (ll''Iter IJ get.

Therefore, MAS, =-, to (!◇(I),
...(9), and °ζm MΔS1 are calculated for m Φ. If the set MAS of m numbers is denoted by I, then this can be thought of as a spectrum having n elements.

IP=(MΔS, : i=1~m)
-...(l[]) In this new spectral region (component spectral region), the horizontal axis is the gas species i, and the vertical axis is the sum of relative absorbances MAS. Therefore, the above equation (9) can be thought of as converting the +7il wave number spectrum A into a component spectrum ψ using the set Φ.

To explain this using a specific example, Figure 3 shows the frequency spectrum resulting from a mixture of the three gases schematically shown in Figure 7 at arbitrary concentrations. 1. Apply the peak base vs. wavenumber point specification values for each of the three gases specified in FIG. 7, and find the sum of their respective relative absorbances represented by X, Y, and Z. and,
The sum of these relative absorbances is plotted in a region where the horizontal axis represents the gas species and the vertical axis represents the sum of the relative absorbances, as shown in FIG.

The component SBEK[*LE obtained in this way has the influence of noise largely removed like the J double series, and interference shadows between SBEK*LEs are suppressed. As shown in Figures 2 and 3 above, if conversion without interference between components is possible, the sum of the relative absorbances of each component in the component spectral region is proportional to the concentration of each component.
Although it is possible to directly obtain the concentration of each component, it is rare to be able to specify wavenumber points without interference as shown in Figures 2 and 3 for the actual gas frequency spectrum.
As shown in FIG. 2, it is normal that some interference remains even in the component spectrum region after conversion.

Therefore, in the quantitative analysis in the component spectral domain, G,,I,
It is necessary to correct the above-mentioned interference, and the actual quantitative analysis using the method of the present invention consists of the calibration stage of creating a matrix (calibration matrix) used for interference correction, that is, the stage of preparing data for interference correction, and the stage of preparing data for interference correction. and an estimation stage in which the unknown concentration is calculated using the method.

In the calibration stage, a calibration matrix is obtained as follows.

Now, it is assumed that there is a reference frequency spectrum α+(i=I−m) of m components G and unit density.

Then, the set Φ of wave number point specified values mentioned above is added to these.

By applying (i=1=m) and performing the transformation shown in equation (9) above, the component spectrum ψ for α8,
(i-1 to m) can be obtained.

More specifically, it can be obtained by calculating the sum of relative absorbances when multiple gases are used as samples individually. Reference component spectra for gas species X, Y, and Z are shown, and the calibration matrix in this case is as follows.

On the other hand, it is assumed that there is a mixed gas of the same m gas components (i-1 to m), and each unknown concentration is C, (i-1 to m). The frequency spectrum of this gas mixture can be obtained in a similar manner, an example of which is shown in FIG. 5, in which case the component spectrum ψ. becomes .

And, ψ,1 is expressed as a linear combination of,.

In other words, ψu = CI・medium, 102・medium, −t・・・・−−
1-c m 'ψ1... (11) always holds true, and when this is rewritten using a matrix, ψ.

-CΩ...G2).

Here, C is a matrix whose rows are hectors consisting of unknown concentrations, and Ω is ψ, and this is called a calibration matrix in the component spectrum domain.

Therefore, the concentrations of gas species X, Y, and Z are CX and C.

Assuming C2, ...03) becomes.

In the calibration step, it is necessary to accurately determine Ω. Furthermore, as already mentioned, ψ is a vector with high linear independence, that is, with little interference, so Ω is a matrix for which a stable inverse matrix is found.

Next, in the estimation stage, by solving the equation θ2) for C, that is, C−ψ. Ω-1...04) The unknown concentration can be estimated.

Then, by using 03) above, CX, CV, and C2 can be obtained, respectively.

Here, the calculated inverse matrix has high linear independence of Ω, so
A stable solution can be obtained, and therefore the error caused by the numerical calculation of the estimated concentration is extremely small.

[Effects of the Invention] Since the present invention is configured as described above, it is possible to accurately quantify multiple components at the same time without being influenced by noise or interference between components. Can be well quantified. In addition, from a practical point of view, it can be implemented as a computer program using a very in-the-box and high-speed method, so even if a sample contains many components, the concentration of each component can be determined with high precision. , it can be obtained much more easily and quickly than before.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing an example of an apparatus for carrying out the method of the present invention, FIG. 2 is a diagram showing an example of a component spectrum used in the method of the present invention, and FIG. 3 is a diagram showing a frequency spectrum. Figures 4 (A), (B), and (C) are diagrams showing reference component spectra, Figure 5 is a diagram showing a component spectrum of a mixed gas, and Figure 6 is a schematic gas spectrum and its relative absorbance. FIG. 7 is a diagram showing an example of specifying wave numbers for gas types. Figures 8 and 9 are diagrams for explaining the problems of the prior art. Figure 8 shows a frequency spectrum of a unit concentration, and Figure 9 shows a schematic superposition of two component spectra. It is a diagram.

Claims (1)

[Claims] In a method of irradiating a sample with light from a light source and analyzing the concentration of a plurality of components contained in the sample based on the frequency spectrum obtained at that time, in the frequency spectrum, there are The frequency points of local peaks and local bases are determined in advance, and from the reference frequency spectra for the plurality of components, the component spectrum is obtained by using the sum of relative absorbances obtained from the difference in the absorbances of these peaks and bases. A multi-component quantitative method in spectroscopic analysis, characterized in that the concentration of each component is obtained separately based on the respective component spectra obtained.