JPS63313036A - Transitional absorption spectral method - Google Patents

Abstract

PURPOSE:To enable in-line measurement even in multicomponent mixed liquid by irradiating sample liquid with exciting light, further irradiating sample with exciting light having wavelength absorbed by the object material of measurement in an excited state, and measuring the quantity of the absorption of the exciting light. CONSTITUTION:The exciting light 21 from a pulse laser light source 1 shoe pulse intervals are controlled 7 is branched 9, and one is guided to a light source intensity detector 5 and the other is guided to a sample cell 3 to project on the sample 11. The exciting light 22 from a CW laser light source 2 is also guided to a light source intensity detector 6 and the sample 11 similarly. Then materials which do not transit an excited state from a base state with the exciting light 21 are excluded from a detection range, and materials which do not transit the excited state of further upper level with the exciting light 22 are also excluded from the detection range. Consequently, the concentration of a desired object material can be measured. Further, when there is a coexistent material which can not separated, variation in the absorption of the exciting light 22 with lapse of time is measured to find the light absorption quantity in a time area wherein the influence of the coexistent material is little, and the absorption intensity based upon only the contribution of the material to be measured is measured to determine the concentration of the object material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spectroscopic analysis method, and particularly to a spectroscopic analysis method suitable for measuring the concentration of a specific substance in a multi-component mixed solution.

[Conventional technology]

Conventionally, the method of measuring the concentration of a substance in a solution by spectrophotometry generally measures light absorption during the transition from the ground state to the excited state of the substance to be measured.

Among them, the method for measuring the substance concentration of 1 polyacid mixed solution A is described in "Spectral Measurement and Spectrophotometer" by Kazuo Shibata.
Discussed in Kodansha, (1974), pp. 143-145.

[Problem that the invention seeks to solve]

The above conventional technology is effective when the number of mixed components is small, such as 2 to 3 types, but when the number of mixed components increases further, there is a problem that overlapping absorption bands become complicated and analysis becomes impossible. There was. In other words, in various solution systems such as environmental analysis, pollution analysis, process solution analysis of chemical plants, food analysis, and drug analysis, many components often coexist, and in such cases, conventional absorption Since it is not possible to analyze the components from the spectrum using the above-mentioned conventional techniques, a method is usually used in which some kind of component separation is performed in advance and then the analysis is performed.

An object of the present invention is to enable non-contact and in-line measurement of the concentration of a substance to be measured, even in a multi-component mixed solution, without separating the components in advance.

[Means for solving the problem] The above purpose is to irradiate the sample liquid with excitation light (first excitation light) having a wavelength that excites the substance to be measured, to excite the substance to be measured, and to further excite the substance to be measured. In other cases, the sample liquid is irradiated with excitation light (second excitation light) at a wavelength that is absorbed by the substance to be measured, and the amount of optical absorption (transient absorption) of the second excitation light is measured. In some cases, this is accomplished by measuring changes in the amount of light absorption over time.

[Effect]

Conventional normal absorption analysis looks at the absorption from the ground state of the substance to be measured, so when multiple components are mixed, the absorption of each component overlaps, and if the mixture exceeds this level, it becomes impossible to quantify the concentration. However, in the present invention, first, substances that are not transitioned from the ground state to the excited state by the first excitation light are excluded from the detection range, and then, among the substances that are transitioned to the excited state by the first excitation light, the substances are excluded from the detection range. Substances that are not transitioned to a higher excited state by the second excitation light are excluded from the detection range. In this way, only the degree of # of the desired substance to be measured can be measured. If there is a coexisting substance that cannot be separated from the detection range even after these two processes, measure the change over time in the amount of light absorption of the second excitation light and find the amount of light absorption in a time domain where there is no influence of the coexisting substance. By measuring the absorption intensity contributed only by the substance to be measured, the concentration of the substance to be measured can be quantified.

〔Example〕

FIG. 1 shows an apparatus used to carry out the method of the present invention, and this apparatus includes a first light source 1 that emits a first excitation light 21 having a wavelength that causes the substance to be measured to transition from a ground state to an excited state; 21, a mirror 10 that reflects the first excitation light 21, and a second excitation light 22 having a wavelength that causes the substance to be measured to transition from an excited state to an even higher excited state.
a second light source 2 that emits light, a beam splitter 9' that branches the second excitation light 22, a sample cell 3 containing a measurement sample 11,
A detector 4 detects the intensity of the transmitted light 23 that the second excitation light 22 passes through the sample cell 3, a first light source intensity detector 5 monitors the intensity of the first excitation light 21, and a first light source intensity detector 5 monitors the intensity of the second excitation light 22. A second light source strong anti-reflection detector 6 that monitors, a control device 7 that controls the first light source 1 and issues a control signal, and a data processing device 8 that calculates the concentration of the substance to be measured from the detected nine light sources and the control signal.
Consists of.

Next, the characteristics and operations of individual components will be explained.

First, as the light source used for the first light source IK, a pulsed light source with good monochromaticity and variable wavelength is suitable. As such a light source, it is possible to use a Frudge Island lamp separated by a spectroscope, but a pulsed laser with good monochromaticity and high light intensity is desirable. To make the wavelength variable, a dye laser, a nonlinear crystal, etc. may be used in combination. The pulse interval of this pulsed light source constituting the first light source 1 is controlled by a control signal (trigger signal) from the control device 7. The first excitation light 21 from the first light source 1 is split by a beam splitter 9,
One side is directed toward the sample cell 3 and the other toward the first light source intensity detector 5, but the branching ratio at this time may be large toward the sample cell 3 side and small toward the first light source intensity detector 5 side. This branching ratio is measured in advance, and based on this, the intensity of the light irradiated onto the sample cell 3 is determined by the data processing device based on the measured value of the first light source intensity detector 5. Here, as the first light source intensity detector 5, in order to measure the intensity of the monochromatic first excitation light 21, a detector with clear wavelength dependence (for example, a photodiode, etc.) is used.

Next, various light sources can be used as the second light source 2. A pulsed light source similar to the first light source 1 can be used, or a continuous light source can be used. However, when using a pulsed light source, it is necessary to synchronize with the first light source 1, so the pulse generation must be controlled by the control device 7. Continuous light sources do not require such control, but the light source must be highly stable. Continuous light sources include CW lasers, tungsten lamps, deuterium lamps, and the like. Since the CW laser has good monochromaticity and strong intensity, it is suitable for selective excitation of the substance to be measured, and the use of a wavelength tunable laser increases the versatility. on the other hand,
When using a tungsten lamp, a deuterium lamp, etc., it is necessary to perform spectroscopy using a spectrometer. The beam splitter 9' that branches the second excitation light 22 and the second light source intensity detector 6 that measures the intensity of the second excitation light 22 are similar to the beam splitter 9 and the first light source enhanced detector 5 described above. can be used. The branching ratio of the beam sinter 9' is measured in advance, and the intensity of the second excitation light irradiated onto the sample cell 3 is determined by the data processing device based on the measured value of the second light source intensity detector 6.

The sample cell 3 is a glass cell made of quartz glass that has good transmission characteristics for short wavelength light.

The detector 4 uses a photomultiplier tube or a photodiode. When measuring changes over time in the transmitted light 23, it is preferable to combine a photomultiplier tube with an oscilloscope or use a gateable photodiode. A broadband light source such as a tungsten lamp or a deuterium lamp is used as the second light source 2, and after irradiating the sample cell 3 without spectroscopy, the transmitted light is spectrally separated, and a multi-channel photodiode array detector is used. is also possible.

The data processing device 8 analyzes the signals from the first light source intensity detector 5, the second strong light source detector 6, the detector 4, and the control device 7 according to the principle described later, and calculates the concentration of the substance to be measured. do.

Next, the present invention will be explained in detail.

First of all, Figure 2 shows the electron ugliness of a substance.For simplicity, this diagram shows the ground state (So)% first excited state (S
l) and the second excited state (S, ), where σ is the excitation cross section (corresponding to the extinction coefficient), ■ is the excitation light intensity, λ is the relaxation rate, and the subscript ij is Si From S
This indicates that it is related to the transition to j. The present invention is a method for determining the concentration of a substance to be measured by focusing on the excitation from Sl to S.%N6,81,S@
Atoms of the substance to be measured per unit volume existing in the state (
-! Assuming that the number of molecules) is No. It is a figure showing a spectrum (transient absorption spectrum). As can be seen from this figure, the peak of transient absorption usually exists on the longer wavelength side of the absorption peak from the ground state.

Figure 4 shows the normal absorption spectrum and transient absorption spectrum of benzene solution particles when there are multiple coexisting substances other than anthracene.The solid line shows the observed normal absorption spectrum, and the observed The transient absorption spectrum is shown by the dotted line.

In a normal absorption spectrum, the absorption spectra of multiple components overlap and the absorption spectrum from the ground state of anthracene (dotted chain line) becomes indistinguishable, whereas the transient absorption spectrum is further added to the normal absorption spectrum. Since they can be observed in an overlapping manner (hatched area in the figure), by taking the difference from the normal absorption spectrum, it is possible to obtain a spectrum of only transient absorption. Thus, in the present invention, the amount of normal absorption is subtracted as a background and only the amount of transient absorption is measured. In other words, the present invention can be said to be a kind of internal standard method.

Next, we will analyze the method of concentration setting based on transient absorption spectroscopy.

First, as one of the pre-quantitative methods, the first light source
Consider a case where a pulsed light source (wavelength ω,) is used for the second light source 2, and a continuous light source (wavelength 0x) is used for the second light source 2.

The intensity of the first excitation light incident on the sample cell 3 from the first light source 1 is calculated as follows: Let Ilm be the intensity of the second excitation light incident on the sample cell 3 from the second light source 2. At this time, using the electron level model of the triple-level system shown in Figure 1, the pulse generation time of the first light source is i. = Q, the number of atoms (or molecules) of the substance to be measured at each level is N0°N1. The initial condition for N is as follows, where N is the total number of atoms (or molecules) of the substance to be measured. And, N,, N1. The change over time of N can be expressed by the following simultaneous differential equations.

Equation (2) can be solved analytically under the initial conditions of Equation (1), and can be expressed as the following equation.

e'''''(p-q)''),,,,1.),-<p-q>
t) , , , , , 5) Here 1 , Now, here Nt (t) Focusing on K, Nt (t)
Taking the logarithm of , we get K as follows.

1nNt(t)=-(PQ)t+A! n(((1+r
)e-2qt+((1-r))qt-co to e-2qt
→0, and after a certain time znNt(), it decreases according to a linear equation related to time t, and its slope -
It is our principle that (p-q) indicates a value specific to the substance when the intensity 1** of the second excitation light 22 is constant.

Therefore, the absorption within the observed wavelength &A (t)
is A(t)−σ□zNt(t)l −・・−(8
1, that is, the at of the target substance to be measured can be determined by the following. A(ri) is determined from the incident light intensity I1m of the second light source 20 and the transmitted light intensity IS* (j).

The above is based on the first excitation light 21 and the second excitation light 22)
There are only Hitotsubashi substances that cause transient absorption.'L 4J
I Alr /% I−+F−罎−a”L
1* −−1−ful −−+−, +−−+,
, .

The measurement of the concentration of a substance to be measured in a case where a plurality of substances that cause transient absorption by the second excitation light and the second excitation light are mixed will be explained with reference to FIG.

Assume that there are three types of substances x, y, and z that cause transient absorption by the first excitation light 21 and the second excitation light 22. Since the excitation cross sections and relaxation speeds of these substances differ, the 8
The change over time in the number N1 of 8 states is shown in FIG.

Now, the absorbance f A (t) measured at this time is the absorbance of transient absorption of each substance Ax (t), Ay (t
), Az (t), the second excitation light 22 (wavelength ω, )
It is the sum of the absorbance ABC when absorption occurs from the ground state of the coexisting substances. That is, A (t)
= Ax (t) + Ay (t) + Az (t
) + ABG −...−・α1 Here, ABC can be measured when the first excitation light 21 is not irradiated. In other words, since an internal standard can be obtained, it does not matter if the coexisting substances vary.

Here, when the substance to be measured (measurement target substance) is 2, as can be seen from FIG. 5, the attenuation of N1 is slower in 2 than in x and y, so the time t1 to 1. Between, the contribution is only 2, so the absorbance at that point is A (t)≠Az
(t) + ABG...-αQ' and the concentration of z can be easily found.

On the other hand, if the substances to be measured are x or y, the above method is not possible, so the time t=Q~1. It is possible to use a method of breaking down the absorbance change between the two components into three components by function fitting and measuring the concentration of each component.

Another embodiment of the present invention will be described with reference to FIG.

In this embodiment, a signal for detecting the amount of transient absorption and a photoacoustic signal from an acoustic sensor 12 attached to the sample cell 3 are measured. In this case, non-radiative relaxation from the second excited state S to the first excited state S8 is detected. Therefore, if the nonradiative relaxation rate is 24 times, the photoacoustic signal p (t) is p(t) - λ12□Nz(t)
. . . It can be expressed as α force, and from this the concentration 11N of the substance to be measured can be determined.

As a photoacoustic signal detector, an acoustic sensor 12 such as a microphone or a piezoelectric vibrator is used in close contact with the sample cell 3, and the obtained signal is amplified by a preamplifier 13 and sent to the data processing device 8.

In this embodiment, by detecting a photoacoustic signal, detection sensitivity can be improved compared to the transmitted light intensity measurement method.

Yet another embodiment of the invention is shown in FIG. In this embodiment, by combining two beam splitters 9, the first excitation light 21 and the second excitation light 22 are coaxial with respect to the sample cell 3, and the optical path length t of the sample cell 3 is As for the transmitted light from the sample cell 3, the first excitation light 21 is absorbed by the light absorption filter 14, and only the transmitted light 23 of the second excitation light 22 is sent to the detector 4. It is also possible to install a spectrometer in place of this light absorption filter 14 and detect only the transmitted light 23. By adopting the method of this embodiment, the excitation efficiency 4 of the first excitation light 21 and the second excitation light 23 can be improved, and the detection sensitivity can be improved.

In the apparatus described above, very small light sources such as semiconductor lasers are used as the first light source 1 and the second lights #2,
On the other hand, by using a small detector such as a photodiode as the detector 4, the device can be made smaller.
- Can be made large enough to be carried freely by a person. By doing this, it is possible to easily conduct an investigation of the pollution situation of a river on the spot.

〔Effect of the invention〕

According to the present invention, it is possible to extract a signal due only to the contribution of a substance to be measured in a solution in the presence of a multi-component substance and measure the a degree of the substance to be measured. Another advantageous effect is that the a-type quantification of the substance to be measured can be performed non-contact and in-line.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of the apparatus used to carry out the present invention, Figure 2 is an electronic level model diagram of the measured substance, Figure 3 is an illustration of the absorption and transient absorption spectrum of anthracene in the absence of coexisting substances, and Figure 4 The figure shows the absorption and transient absorption spectrum of anthracene in the presence of coexisting substances, Figure 5 shows the measurement principle of another embodiment of the present invention, and Figure 6 shows the configuration of the apparatus used in another embodiment of the present invention. 7 are configuration diagrams of an apparatus used in yet another embodiment of the present invention. 1... First light source 2... Second light source 3... Sample cell 4... Detector 5... First light source rigidity detector 6... Second light source intensity detector 7... Control device
8...Data processing device 9.9'...Beam splitter 10...Mirror 11...Measurement sample
12...Acoustic sensor 13...Preamplifier 14.
...Light absorption filter 31.32.33...Signal transmission cable. Wavelength (1 liter)

Claims (1)

[Claims] 1. Excitation light of a wavelength that excites the substance to be measured (first
The sample liquid is irradiated with excitation light to excite the substance to be measured, and the sample liquid is further irradiated with excitation light (second excitation light) having a wavelength that is absorbed by the substance to be measured in the excited state. A transient absorption spectroscopy method characterized in that the concentration of a substance to be measured in the sample liquid is determined by measuring the amount of light absorption of excitation light. 2. Measure the change over time in the light absorption amount of the second excitation light, remove the influence of the contribution of coexisting substances other than the measurement target substance included in the light absorption amount by using a difference in decay time or function fitting, and The transient absorption spectroscopy method according to claim 1, characterized in that the concentration of a substance to be measured in a liquid is determined. 3. The light absorption amount of the second excitation light is measured by using a photodetector to measure the transmitted light intensity after the second excitation light passes through the sample liquid. 2. The transient absorption spectroscopy method according to item 2. 4. The light absorption amount of the second excitation light is measured by using an acoustic sensor to detect a photoacoustic signal generated when the sample liquid is irradiated with the second excitation light. The transient absorption spectroscopy method according to item 1 or 2.