JPS63302346A - Light/heat-converting analysis - Google Patents

Abstract

PURPOSE:To improve the reliability of a measured result by a relatively simple instrument by detecting temperature change based on heat with a quantity peculiar to a specimen that is intermittently generated from the specimen receiving intermittent light. CONSTITUTION:Laser light 3 emitted from a laser light source 4 becomes intermittent light 6 wherein a frequency is modulated through a chopper 5 and is incident upon a measuring cell 2. The cell 2 contains a specimen solution 1 and therefore the intermittent light 6 is incident in the solution 1 to form a light path 7 in it. A pyroelectric type infrared sensor 9 is arranged in the solution 1 in a condition wherein the pyroelectric surface 8 of the sensor 9 is directed toward a light path 7 side. A temperature change generated by the passage of the intermittent light 6 in the solution 1 is detected by the sensor 9 and a detected result is outputted from a source terminal 8 as an electric signal. A resultant output signal is inputted to a recorder 12 via a preamplifier 10 and a lock-in amplifier 11 and a measured value corresponding to the output signal from the sensor 9 is recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides the following features: When a sample to be analyzed is irradiated with light,
This invention relates to a light-to-heat conversion analysis method that utilizes the principle of converting light into heat.

[Prior Art] When energy such as light is applied to a sample to be analyzed, the characteristics of the sample can be analyzed using the emitted light. can do.

On the other hand, in the case of a sample in which only a so-called non-radiative transition that does not involve the emission of light occurs, the above-mentioned analysis method cannot be applied. In this case, for example, the sample can be analyzed by utilizing the fact that the sample absorbs light and generates heat. One such analysis method is, for example, the photoacoustic analysis method described in Japanese Patent Publication No. 59-42822.

In photoacoustic analysis, a sample to be analyzed is placed in a sealed container, and the sample is irradiated with light modulated at a certain frequency. At this time, the sample that absorbs the light generates an amount of heat unique to the material that makes up the sample at a frequency that corresponds to the frequency of the irradiated light, causing fluctuations in the gas in the sealed container, causing the gas to become denser and denser. cause waves. This compressional wave is detected by a sound wave detector such as a microphone in a sealed container, and the amplitude and period of the compressional wave are extracted as an electrical signal.

Analytical methods for analyzing samples in this manner have been known for a relatively long time.

[Problems to be Solved by the Invention] However, the above-mentioned photoacoustic analysis method has a structural problem of the device to which it is applied, which requires the use of a closed container. The disadvantage was that it was large-scale.

Furthermore, since the photoacoustic analysis method described above does not directly detect heat generated from a sample, it could not be expected to have very high reliability in analysis accuracy.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a light-to-heat conversion analysis method that can advantageously solve the problems encountered with the photoacoustic analysis method described above.

[Means for Solving the Problems] The present invention is a light-to-heat conversion analysis method that analyzes the characteristics of a sample by measuring the heat generated when the sample to be analyzed is irradiated with light. In order to solve the above-mentioned problems, the following measures are taken.

That is, the light-to-heat conversion analysis method according to the present invention uses intermittent light as the light, places the sample on the optical path of the intermittent light, and places the sample at a position offset from the optical path where the intermittent light is caused by the sample. In the vicinity of the affected position,
The present invention is characterized in that a pyroelectric infrared sensor detects a temperature change based on heat intermittently emitted from the sample in response to the intermittent light.

In addition, in the analysis method according to the present invention, there are typically the following three types of positions where the optical path of the intermittent light is formed in relation to the sample. The first case is when intermittent light is incident into the sample. In this case, the pyroelectric infrared sensor is placed near the optical path of the intermittent light within the sample. The second case is when intermittent light is incident on the surface of the sample and at least a part of the intermittent light is reflected from the surface of the sample. In this case, the pyroelectric infrared sensor is placed outside the sample near the point of incidence of the intermittent light on the surface of the sample. The third case is that the intermittent light is incident on the back surface of the sample, and at least a part of the intermittent light is reflected on the back surface of the sample. In this case, the pyroelectric infrared sensor is placed near the surface of the sample. The first embodiment described above is only applicable in particular if the sample is light-transparent. Furthermore, the second and third embodiments are advantageously applied when the sample does not have light transmittance, but
This method can be applied even if the sample has optical transparency.

[Function] In the present invention, a sample exposed to intermittent light intermittently emits an amount of heat unique to this sample. Therefore, a sample-specific temperature change occurs in the vicinity of the optical path due to this intermittently emitted heat. This temperature change is detected by a pyroelectric infrared sensor based on the pyroelectric effect, and
Extracted as an electrical signal.

[Effects of the Invention] According to the present invention, when implementing the analysis method, a closed container is not particularly required unlike the conventional photoacoustic analysis method. Therefore, the light-to-heat conversion analysis method according to the present invention does not require a large-scale configuration of an apparatus for applying the method, and can be carried out using a relatively simple apparatus.

Furthermore, according to the present invention, the heat emitted from the sample, and more specifically, the temperature change, can be directly detected by the pyroelectric infrared sensor, which provides highly reliable measurement results in terms of analysis accuracy. You can expect it.

Furthermore, according to the present invention, blank correction during measurement can be performed simultaneously with the measurement.

[Embodiment] FIG. 1 is a block diagram schematically showing an apparatus for carrying out an embodiment of the present invention. This example is directed to a method of measuring the concentration of a solution.

A sample solution 1 is placed in a transparent measurement cell 2 and subjected to analysis. As the excitation light to be irradiated onto such sample solution 1, for example, visible laser light 3 is used, and this is emitted from a laser light source 4. Note that the laser light source 4 may be, for example, a He-Ne laser device or an A
An r+ laser device can be used. The laser beam 3 is
The light passes through the chopper 5 and becomes an intermittent light 6 modulated to a frequency of, for example, about 10 Hz. This intermittent light 6 is incident on the constant cell 2 .

As described above, the measurement cell 2 contains the sample solution 1, and therefore the intermittent light 6 enters the sample solution 1 and forms an optical path 7 within the sample solution 1. A pyroelectric infrared sensor 9 is placed near the optical path 7 of the intermittent light 6 in the sample solution 1 with its pyroelectric surface 8 facing toward the optical path 7 side. Note that the distance between the optical path 7 and the pyroelectric surface 8 is preferably as small as possible, and is selected to be about 200 μm, for example. In addition, the optical path 7 and the pyroelectric surface 8
It is preferable that the interval is set as strictly as possible. Note that the pyroelectric surface 8 may be formed by a conventionally commonly used blackened film, but may also be formed by a vapor-deposited gold film in consideration of solution resistance and thermal conductivity. .

The details of the pyroelectric infrared sensor 9 will be explained later with reference to FIGS. 2 and 3, but this sensor 9
is equipped with a source terminal S1, a drain terminal, and a ground terminal G.

As described above, the temperature change caused by the intermittent light 6 passing through the sample solution 1 is detected by the pyroelectric infrared sensor 9 and output from the source terminal S as an electrical signal. This output signal is amplified by a preamplifier 10, and the output signal of the preamplifier 10 is further input to a lock-in amplifier 11. Lock-in amplifier 11 has
A reference signal taken out from chopper 5 is input, and lock-in amplifier 11 outputs only a signal synchronized with the chopping frequency. This output signal is
2, where the measured values corresponding to the output signals from the sensor 9 are recorded.

For example, the recorder 12 may be replaced with a display, or both may be used. Furthermore, a data processing device using a micro-PU may be used.

FIG. 2 shows an example of an equivalent circuit of the pyroelectric infrared sensor 9. Further, FIG. 3 similarly shows an example of the mechanical structure of the sensor 9 in a cross-sectional view. Note that in FIGS. 2 and 3, "S", "Do", and "G" correspond to "S", "D", and "G'" shown in FIG. 1, respectively.

Referring to FIG. 2, one electrode of the pyroelectric body 13 is an FET
The other electrode is connected to the ground terminal G. A DC voltage is applied to the drain terminal connected to the drain electrode of the FET 14. Further, the source electrode of the FET 14 has a source terminal S
is connected.

Furthermore, a resistor Rg is connected in parallel with the pyroelectric body 13. In addition, a resistor R is connected between the source terminal S and the ground terminal 0.
8 are connected.

Electric charges are generated in the pyroelectric body 13 based on temperature changes, current flows through the resistor Rg due to the electric charges, and a potential difference is generated between both ends of the resistor Rg. This potential difference is the source of FET14.
The impedance is converted by the follower circuit, and a potential difference appears across the resistor R5 between the source terminal S and the ground terminal G. Since this potential difference changes based on temperature changes, the AC output signal on which the DC bias voltage applied to the drain terminal is superimposed is transferred to the source terminal S.
taken out from

An example of the mechanical structure of the pyroelectric infrared sensor 9 will be described with reference to FIG. The sensor 9 includes a metal case 17 consisting of a cap 15 and a bottom plate 16. A window 18 for transmitting infrared rays is formed in the cap 15, and a flat pyroelectric material 19 is attached to the inner surface of the cap 15 with a sealing resin 20 so as to receive the infrared rays incident through the window 18. . The pyroelectric body 19 corresponds to the pyroelectric body 13 shown in FIG. 2, and electrodes (not shown) are formed on both surfaces thereof. The electrode formed on the upper surface of the pyroelectric body 19 in FIG. 3 is electrically connected to the metal case 17.

A substrate 21 made of, for example, alumina is arranged inside the metal case 17 so as to extend substantially parallel to the bottom plate 16 . A FET 22 is arranged on the upper surface of the substrate 21.

This FET 22 corresponds to the FET 14 shown in FIG. A lead wire 23 is shown to connect the FET 22 and an electrode formed on the lower surface of the pyroelectric body 19.

This lead wire 23 connects the pyroelectric body 13 and FE in FIG.
This corresponds to the line connecting the gate electrode of T14.

A ground terminal G5, a source terminal S, and a drain terminal held by the substrate 21 pass through the bottom plate 16 and are led out to the outside of the metal case 17. The ground terminal G is electrically connected to the metal case 17 via the conductive resin 24. As a result, the electrode formed on the upper surface of the pyroelectric body 19 becomes electrically connected to the ground terminal G. The source terminal S and the drain terminal S are each electrically insulated from the metal case 17.

It should be noted that in FIG. 3, only the main components constituting the pyroelectric infrared sensor 9 are shown.

In the sensor 9 shown in FIG. 3, the upper surface of the pyroelectric body 19 is
The measuring cell 2 is arranged so as to constitute the pyroelectric surface 8 in FIG.
and positioned relative to the sample solution 1.

Next, using the apparatus shown in FIG. 1, aqueous solutions in which appropriate light-absorbing species (dyes) are dissolved at various concentrations are used as sample solution 1, and the correlation of the signal intensity obtained from the sensor 9 with respect to the concentration is determined. Let me introduce an example of an experiment that determined the relationship.

First, as the laser light source 4, a 15 mW Ar+ laser device was used. The chopper 5 was controlled to provide intermittent light 6 of 10 Hz. In addition, newcoccin was used as the light-absorbing species (dye) dissolved in sample solution 1. Newcoccin has a molar extinction coefficient of 1.9 according to the Beer-Lambert law at a wavelength of 488°0 nm.
0X10'C "+ yl -1.

FIG. 4 shows the concentration of newcoccin C[10-6
A plot of signal strength P[mV] versus signal strength P[mV] is shown. Each signal intensity is corrected based on the signal intensity of a sample containing no new coccin, ie, a blank.

As shown in FIG. 4, it can be seen that the signal strength P increases in proportion to the concentration in the concentration range up to 1X10-5M. That is, within this concentration range, the concentration C of the aqueous solution can be determined as a linear function of the signal strength P.

Note that when the concentration of sample solution 1 exceeds lXl0-'M,
It was found that the signal strength P gradually increases, reaches a maximum, and then decreases. This is because in the region of low concentration, the absorption of laser light is very small, so the laser light is hardly attenuated and is proportional to the dye concentration, but as the concentration increases, the laser light is strongly absorbed, This is thought to be because the light is attenuated before reaching the area in front of the pyroelectric surface of the sensor.

Similarly, an experiment was conducted using brilliant blue as the light-absorbing species (dye) and a He-Ne laser device as the laser light source 4, but the experimental results were substantially the same as the experimental example described above. Ta.

In addition, brilliant blue has a molar absorption coefficient of 1.27×10′c′′ M˜1 according to the Lambert-e-Beer law for light with a wavelength of 632.8 nm.

Regarding the sensor 9 shown schematically in FIG. A pair of sensors 9 may be provided facing each other.

Further, as a means for receiving more heat generated in connection with the optical path 7 as described above, a pyroelectric infrared sensor 9a having a structure as shown in FIG. 5 may be used. In addition, in FIG. 5, a sensor 9a having the same structure is shown.
However, a state in which two of them are combined is shown. Moreover, since each sensor 9a includes many elements common to the sensor 9 shown in FIG. 3, corresponding elements are given the same reference numerals and redundant explanation will be omitted.

The sensor 9a shown in FIG. 5 is characterized by the use of a semi-cylindrical pyroelectric body 19a.

The electrode on the inner peripheral side of the pyroelectric body 19a is electrically connected to the metal case 17.

More specifically, a part of the cap 15 that defines the peripheral edge of the window 18 in the cap 15 is bent along the electrode on the inner circumferential side of the pyroelectric body 19a, and at this bending point, for example, Electrically connected by conductive resin (not shown).

In FIG. 5, 7 indicates the optical path of the laser beam.

As can be seen from the positional relationship between the optical path 7 and the pyroelectric body 19a, according to the sensor 9a, the pyroelectric body 19a receives the heat generated in connection with the laser beam over a wider area.

Therefore, the intensity of the output signal from the sensor 9a is increased, and as a result, the accuracy of analysis can be improved.

In FIG. 5, two sensors 9a are used, and the optical path 7 is surrounded by a pyroelectric material 19a provided in each sensor 9a.

Therefore, the structure shown in FIG. 5 is an example of a structure in which the heat emitted in connection with the optical path 7 can be detected most efficiently. However, even when only one sensor 9a shown in FIG. 5 is used, heat can be detected more efficiently than the sensor 9 shown in FIG. Only one may be used.

Further embodiments of the invention are shown in FIGS. 6 and 7, respectively.

In the example shown in FIG. 6, a solid and optically transparent sample 2
5 is used. Intermittent laser light 6 generated in the same manner as the method shown in FIG. 1 is incident into the sample 25. Note that the optical path 7 of the intermittent light 6 is formed near one surface 26 of the sample 25.

A sensor 9C having a structure substantially similar to that shown in FIGS. 1-3 is preferably arranged such that its pyroelectric surface 8C is in contact with the surface 26 of the sample 25. However, such contact is not required.

In the state shown in FIG. 6, the sample 2 is exposed to the intermittent light 6.
Temperature changes based on the heat intermittently emitted from the sensor 5 are detected by the sensor 9C.

In FIG. 7, for example, a solid sample 2 with no optical transparency is shown.
7 have been submitted for analysis. On one surface 28 of the sample 27,
Intermittent light 6 generated by the method shown in FIG. 1 is incident. The intermittent light 6 is then reflected on the surface 28 of the sample 27. Note that at least the vicinity of the incident point 29 on the surface 28 of the sample 27 is preferably made of a mirror surface in order to prevent diffuse reflection of light, and has a structure substantially similar to that shown in FIGS. 1 to 3. The pyroelectric infrared sensor 9d having a pyroelectric surface 8d is placed near the incident point 29 and outside the sample 27, with its pyroelectric surface 8d facing the incident point 29.

In the analysis method shown in FIG. 7, when the intermittent light 6 is incident on the surface 28 of the sample 27, heat is intermittently emitted from the sample 27, and a temperature change based on the heat is detected by the sensor 9d.

In addition, in the analysis method shown in FIG. 7, the sample 27 does not need to be a solid that does not have light transmittance, but may have light transmittance or may be a liquid.

In FIG. 8, similar to FIG. 7, for example, a solid sample 30 that does not have light transmittance is subjected to analysis.

Intermittent light 6 generated by the method shown in FIG. 1 is incident on one surface 31 of the sample 30. The intermittent light 6 is then reflected on the surface 31 of the sample 30. Note that, similarly to the example shown in FIG. 7, at least the vicinity of the incident point 32 on the surface 31 of the sample 30 is preferably a mirror surface in order to prevent diffuse reflection of light. A pyroelectric infrared sensor 9e having a structure substantially similar to that shown in FIGS.
is placed outside the sample 30.

In the analysis method shown in FIG. 8, when the intermittent light 6 enters the back surface 31 of the sample 30, heat is intermittently emitted from the sample 30, and a temperature change based on the heat is detected by the sensor 9e.

In addition, in the analysis method shown in FIG. 8, the sample 30 does not need to be a solid that does not have light transmittance, but may have light transmittance or may be a liquid.

The analysis method according to the present invention has a configuration as shown in FIG.
While branching into two optical paths 7a and 7b using By taking the difference between the two measured values using the differential amplifier 37, the blank signal strength can be corrected simultaneously with the measurement operation.

Note that in FIG. 9, elements corresponding to those shown in FIG. 1 described above are given the same reference numerals, and redundant explanations will be omitted.

10 to 13 show still another embodiment of the present invention which is advantageously implemented for the purpose of preventing noise generation due to thermal changes and vibrations in the external atmosphere.

10 and 11 show an example of the shape of the electrode formed on the pyroelectric body 19b, which is advantageously used in this embodiment. As shown in FIG. 10, on the heat sensing surface of the pyroelectric body 19b, a circular sensing electrode 38 is formed at the center, and an external noise compensation electrode 39 is formed around the sensing electrode 38. The sensing electrode 38 and the external noise compensation electrode 39 are electrically connected to each other via a connecting portion 40 . In addition, the sensing electrode 38
and the external noise compensation electrode 39 have the same area. On the other hand, as shown in FIG. 11, on the surface of the pyroelectric body 19b opposite to the heat sensing surface, a center electrode 41 and a peripheral electrode 42 are formed around the center electrode 41. These electrodes 41 and 42 are electrodes 38 and 39 on the heat sensing surface side, respectively.
It is assumed that the dimensions and shape completely overlap with the .

FIG. 12 shows the mechanical structure of a pyroelectric infrared sensor 9r constructed using the above-mentioned pyroelectric material 19b. 1st
The pyroelectric infrared sensor 9r shown in FIG. 2 includes many elements in common with the pyroelectric infrared sensor 9 shown in FIG. 3, so corresponding elements are given the same reference numerals. Only different configurations will be described below.

The aforementioned pyroelectric body 19b is fixed inside the metal case 17 with an insulating sealing resin 20, with only the sensing electrode 38 at the center of its heat sensing surface exposed through the window 18.

The central electrode 41 on the back side of the pyroelectric body 19b is electrically connected to the gate terminal of the FET 22 through a lead wire 43, and the peripheral electrode 42 on the same side is electrically connected to the ground terminal G through a lead wire 44. connected to.

The pyroelectric infrared sensor 9f configured as shown in FIG. 12 has an equivalent circuit as shown in FIG. 13. The pyroelectric body 19b having the electrode shape described above constitutes two pyroelectric elements 45 and 46 electrically connected in series. The polarization directions in these pyroelectric elements 45 and 46 appear in the directions indicated by arrows in FIG. In FIG. 13, other elements perform the same functions as the elements shown in FIG. 2 described above, and corresponding elements are given the same reference numerals and redundant explanations will be omitted.

Although the invention has been described above in connection with the illustrated embodiments, various other modifications are possible within the scope of the invention.

For example, the characteristics of the sample measured by the analysis method according to the present invention are not limited to the concentration of the solution as in the above-mentioned embodiments. For example, thermal constants such as specific heat can also be measured.

Consider a specific heat measurement model as shown in FIG.

In FIG. 14, ml + Q, 2 is measurement cell 2
When the incident part 47 of the intermittent light 6 to the cell 2 is set to "θ"
These are the coordinates indicating the position within. IO,I,,12 is 0.
L, (J, indicates the intensity of light at point z. If β is the absorption coefficient of sample solution 1 and A is the cross-sectional area of intermittent light 6, then Strength■
I+ 12 is expressed as 11-10 e-""12=I6e-"". When the thermal energy contributing to the temperature change sensed by the infrared sensor is ΔI, ΔI is expressed by the following formula (%).

In this analysis method, β and α are very small, so they can be approximated as ΔI = 10 βΔ(. Therefore, the temperature rise ΔT at this time can be expressed as follows. Here, CF is the specific heat of the sample,
, is the density of the sample. Since the pyroelectric output is proportional to the amount of temperature change per hour, 10. β.

When measured with A constant, it can be said that (1/CP ρ,) is proportional to the output of the sensor. Utilizing this relationship, the specific heat of the sample can be determined by comparing the output with, for example, water whose density and specific heat are known. It is also possible to measure the bandgap of a sample. In this case, the light constituting the intermittent light is provided in a state where it is separated into spectra within a specific wavelength range. Then, a unique signal is output from the sensor at a certain specific wavelength. Therefore, by finding this wavelength, the bandgap can be measured.

In addition, in this invention, it is particularly advantageous to use a substance that exhibits non-radiative transition as a sample, but the sample is not limited to such a substance; even substances that cause radiative transition can be used as a sample. can.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an apparatus for carrying out an embodiment of the present invention. FIG. 2 is an equivalent circuit diagram of the pyroelectric infrared sensor 9 shown in FIG. 1. FIG. 3 is a cross-sectional view showing the mechanical structure of the pyroelectric infrared sensor 9. FIG. 4 is a graph showing the results of measuring the signal intensity P from the sensor with respect to the concentration C of the aqueous solution in an experimental example of the present invention. FIG. 5 is a sectional view showing the mechanical structure of a pyroelectric infrared sensor 9a used in implementing another embodiment of the present invention. Figures 6, 7 and 8 are
FIG. 7 is an illustrative view showing a state in which still another embodiment of the present invention is being implemented. FIG. 9 is a block diagram showing an apparatus for implementing yet another embodiment of the invention. 10th
The figure and FIG. 11 are diagrams showing an example of a pyroelectric electrode shape that is advantageously used in still another embodiment of the present invention. FIG. 12 shows a pyroelectric infrared sensor 9 constructed using the pyroelectric body 19b shown in FIGS. 10 and 11.
FIG. 3 is a cross-sectional view showing the mechanical structure of r. FIG. 13 shows the pyroelectric infrared sensor 9 shown in FIG. 12.
FIG. FIG. 14 is a model diagram for explaining that the present invention is applied to specific heat measurement. In the figure, 1 is a sample solution (sample), 3 is a laser beam (light), 6 is an intermittent light, 7, 7a, 7b are optical paths, 9.9a, 9
c, 9d, 9e, 9f' are pyroelectric infrared sensors, 13,
19.19a and 19b are pyroelectric bodies, 25.27.30 is a sample, 29.32 is an incident point, 35 is a measurement sample, and 36 is a reference sample. C/lo'M Figure 7

Claims (5)

[Claims] (1) A light-to-heat conversion analysis method based on the measurement of heat generated when a sample to be analyzed is irradiated with light, using intermittent light as the light and placing the sample on the optical path of the intermittent light. , in the vicinity of a position offset from the optical path and where the intermittent light is affected by the sample, temperature changes due to heat intermittently emitted from the sample in response to the intermittent light are measured using pyroelectric infrared rays. A light-to-heat conversion analysis method characterized by detection using a sensor. (2) the sample is optically transparent, the intermittent light is incident into the sample, and the pyroelectric infrared sensor is disposed near the optical path of the intermittent light within the sample;
A light-to-heat conversion analysis method according to claim 1. (3) the intermittent light is incident on the surface of the sample, and
2. The light-to-heat conversion analysis method according to claim 1, wherein the pyroelectric infrared sensor is placed near the point of incidence of the intermittent light on the surface of the sample and outside the sample. (4) the intermittent light is incident on the back surface of the sample, and
The light-to-heat conversion analysis method according to claim 1, wherein the pyroelectric infrared sensor is placed near the surface of the sample corresponding to the point of incidence of the intermittent light. (5) A reference sample is provided, the intermittent light is irradiated to the measurement sample and the reference sample, and a pyroelectric infrared sensor is provided on the optical path after the intermittent light is influenced by the reference sample. was placed to enable blank correction,
A light-to-heat conversion analysis method according to any one of claims 1 to 4.