JP4749901B2 - Absorbance measuring device, absorbance measuring method - Google Patents

Description

  The present invention relates to an absorbance measuring apparatus and method for measuring the absorbance of a sample.

Generally, when measuring the absorbance of a sample, a transmission type absorbance measuring apparatus is used.
A transmission-type absorbance measurement apparatus measures absorbance by transmitting measurement light to be measured through a sample and detecting the intensity of observation light transmitted without being absorbed in the sample. Here, if the intensity of the measurement light before entering the sample is I ₀ , and the intensity of the measurement light after passing through the sample is I, the absorbance is A = −log ₁₀ (I / I ₀ ).
Patent Document 1 discloses a transmission-type absorbance measuring apparatus that can measure absorbance of a sample with high absorbance without problems such as the volume of a suspension.
On the other hand, Patent Document 2 discloses a sample analysis method that utilizes the characteristics that when a sample is irradiated with excitation light, the sample generates heat due to the photothermal effect and the refractive index of the sample changes due to the thermal lens effect. Has been.
The principle of the sample analysis method disclosed in Patent Document 2 is as follows.
First, the measurement site | part of a sample is irradiated with 1st light (henceforth investigation light), and also 2nd light (henceforth excitation light) is irradiated to the measurement site | part. Then, the investigation light that has passed through the measurement region of the sample is condensed by the condenser lens and then passed through the pinhole, and the intensity of the investigation light after passing through the pinhole is detected by the photodetector. Then, the refractive index of the sample changes due to the irradiation of the excitation light, the optical path of the inspection light changes due to the change in the refractive index, and the intensity of the inspection light after passing through the pinhole changes according to the change amount of the optical path. . Therefore, based on the intensity change of the investigation light after passing through the pinhole, the heat generation characteristic of the sample due to the absorption of the excitation light can be measured, and the physical property of the sample can be measured from the heat generation characteristic.
JP-A-6-160280 Japanese Patent Laid-Open No. 10-232210

However, in the transmission-type absorbance measurement, the intensity of the measurement light after passing through the sample decreases as the absorbance of the sample increases. For this reason, in the transmission type absorbance measurement, the intensity of the measurement light after passing through the sample is extremely close to 0 for a sample with very high absorbance, and the intensity of the measurement light cannot be measured with a photodetector, or There was a problem that it was impossible to measure with sufficient accuracy. For example, when the measurement light to be measured is light in the infrared region, the problem becomes particularly noticeable because many samples exhibit extremely high absorbance.
Further, although the range of absorbance that can be measured can be expanded if the thickness of the sample is made sufficiently thin, there is a problem that it is difficult to manage the thickness of the sample that is directly linked to the measurement accuracy with high accuracy. In addition, when the sample is a liquid sample, there has been a problem that the work of enclosing and taking out the sample in a prefabricated container (cell) that forms a very thin sample container is very complicated. In addition, when measuring a sample having a low viscosity and a low surface tension, such as a liquid sample using an organic solvent, there also arises a disadvantage that the sample leaks from the gap between the joints of the assembly-type container. Further, as in the problem shown in Patent Document 1, in the case of a suspension sample, problems such as accumulation of a suspension in a liquid sample container may occur.
There are also reflection-type absorbance measuring devices that measure the absorption of light that penetrates the interface of the liquid sample with the container (cell), but the work of sealing the liquid sample into the container and attaching it to the measuring device is complicated. There is a problem that it is.
On the other hand, when the sample is irradiated with excitation light, the higher the absorbance of the sample with respect to the excitation light, the greater the amount of heat generated by the sample due to the photothermal effect, and the greater the change in the survey light. For this reason, if the photothermal effect is utilized, the change in the investigation light can be accurately measured even for a sample having a high absorbance.
Therefore, the present invention has been made in view of the above circumstances, and the object of the present invention is to easily measure the absorbance of a very high absorbance sample with high accuracy by measuring the absorbance using the photothermal effect of the sample. An object of the present invention is to provide a device and method for measuring absorbance.

In order to achieve the above object, the present invention is configured as an absorbance measuring apparatus for measuring the absorbance of a sample, and is characterized by including the components shown in the following (1) to (4).
(1) Survey light irradiation means for irradiating the sample with predetermined survey light.
(2) Measurement light irradiation means for irradiating the sample with measurement light to be measured for absorbance so as to intersect the inspection light within the sample.
(3) Survey light change measuring means for measuring the phase of the search light by crossing the measurement light in the sample.
(4) Absorbance calculation means for calculating the absorbance of the sample for the measurement light based on the measurement result of the survey light change measurement means.
When the measurement light is captured as excitation light, the amount of change in the amount of heat generated by the sample and the change in refractive index due to the photothermal effect are highly correlated with the height of the sample absorbance for the measurement light. The size of the change in the refractive index of the sample due to irradiation of measurement light, the size and high correlation of changes in I that position phase to intersect the measurement light in the sample (excitation light). For this reason, if the degree of change in the phase of the survey light irradiated on the sample by crossing the measurement light in the sample is measured by the survey light change measurement unit, the absorbance calculation unit can determine the measurement light. The absorbance of the sample can be calculated (measured) with high accuracy. Also, in this absorbance measurement device, only the intersection between the measurement light and the survey light in the sample is the measurement site, and the measurement site (light intersection) is set to the desired position and size by adjusting the optical equipment. It's easy to do. For this reason, unlike the conventional transmission type absorbance measurement in which the entire thickness direction of the sample is a measurement site, it is not necessary to reduce the thickness of the sample even when measuring a sample having a high absorbance.

Further, in the case where the measurement light is a light in the infrared region, for example, when measurement is performed on a combination of the measurement light and the sample with high absorbance, the intersection of the measurement light and the investigation light in the sample is the above-mentioned in the sample. It is preferable to set so as to be positioned in the vicinity of the inside with respect to the interface of the measurement light incident portion.
Thereby, the characteristic change of the part excited by the measurement light before being largely attenuated in the sample can be measured by the investigation light.
Further, in that case, it is preferable that the direction of the optical axis of the investigation light in the sample is set so as to be parallel or substantially parallel to the interface of the measurement light on the sample.
As a result, when the investigation light passes near the incident part interface of the measurement light in the sample, there is a waste that a part of the investigation light protrudes to a portion outside the sample (a portion other than the measurement site in the sample). Can be prevented.

Further, an absorbance measuring apparatus further comprising a sample container that is filled with the fluid sample and has a wall formed to transmit the measurement light and the investigation light from the outside to the filling portion of the sample. It is done.
Thereby, the light absorbency of a fluid-like sample can be measured.
Here, in order to adjust the width (cross-sectional size) of the investigation light at the intersection with the measurement light, that is, the dimension of the measurement site of the sample in the measurement light direction, the investigation light is collected by a condenser lens or the like. In this case, the width of the investigation light in the sample gradually becomes narrower toward the intersection with the measurement light.
Therefore, it is preferable that the inner surface of the wall through which the measurement light is transmitted in the sample container is formed so as to protrude from the filling portion of the sample.
As a result, when the intersection of the survey light and the measurement light is positioned near the interface of the measurement light incident portion in the sample (that is, the inner wall of the sample container), one of the survey lights up to the intersection is obtained. It can be prevented that the portion is wasted from protruding into the wall of the sample container (portion other than the measurement site in the sample).
Furthermore, in that case, it is preferable that a mask for limiting the transmission region of the measurement light is provided on a wall of the sample container that transmits the measurement light.
With this mask, it is possible to adjust the width of the measurement light (cross-sectional size) at the intersection with the investigation light, that is, the size of the measurement site of the sample in the investigation light direction.
Further, it is conceivable that the investigation light change measuring means measures a change in phase of the investigation light caused by crossing the measurement light in the sample with an optical interferometer.
Thereby, the change of the investigation light can be measured optically with high accuracy.

In addition, the present invention can also be understood as a method of measuring the concentration of light having the same principle as that of the absorbance measurement using the absorbance measuring apparatus described above.
That is, an absorbance measurement method for measuring the absorbance of a sample, characterized in that the following steps (1) to (4) are performed.
(1) A measurement light irradiation procedure for irradiating the sample with light emitted from a light source that emits measurement light to be measured for absorbance.
(2) A survey light irradiation procedure for irradiating the sample with light emitted from a light source that emits predetermined survey light so as to intersect the measurement light within the sample.
(3) An investigation light change measurement procedure for measuring the phase of the investigation light caused by crossing the measurement light in the sample through a predetermined light measurement means.
(4) An absorbance calculation procedure for calculating the absorbance of the sample with respect to the measurement light by a predetermined computer based on the measurement result of the survey light change measurement procedure.
The operation and effect of the implementation of the absorbance measurement method are the same as the operation and effect of the absorbance measurement apparatus described above.
Here, when the measurement light and the inspection light in the sample are set so that the intersection of the measurement light and the measurement light incident portion interface in the sample is located in the vicinity of the inside, it is preferable that the following condition is satisfied. .
One of the conditions is that when the absorbance per unit length of the sample with respect to the measurement light (unit absorbance) is 30 [cm ⁻¹ ] or less, the measurement light and the investigation light in the sample It is a condition that the intersecting portion is set to be located within 150 μm on the inner side with respect to the interface of the measurement light incident portion in the sample.
The second condition is that when the absorbance per unit length of the sample with respect to the measurement light (unit absorbance) is 40 [cm ⁻¹ ] or less, the measurement light and the investigation light in the sample are measured. Is set so that the crossing portion is positioned within 100 μm on the inner side with respect to the incident portion interface of the measurement light in the sample.
By satisfying these conditions, the characteristic change of the portion excited by the measurement light before being greatly attenuated in the sample can be measured by the investigation light.

According to the present invention, the sample is excited by the measurement light, and the change in the refractive index of the sample caused by the photothermal effect is measured as the change in the phase of the investigation light irradiated on the sample. Can be measured with high sensitivity and high accuracy. In addition, it is easy to set the measurement site in the sample (intersection of the measurement light and the survey light) to a desired position and size by adjusting the optical equipment. For this reason, unlike the conventional transmission type absorbance measurement in which the entire thickness direction of the sample is a measurement site, it is not necessary to reduce the thickness of the sample even when measuring a sample having a high absorbance. As a result, it is difficult to manage the dimension of a very thin sample with high accuracy, and the conventional work such as enclosing and taking out a liquid sample in an assembly-type container having a very thin sample container. The problem is solved.
Furthermore, when the measurement light is in the infrared region, for example, when measurement is performed on a combination of the measurement light and the sample with high absorbance, the intersection of the measurement light and the investigation light in the sample is It is even more preferable that the measurement light is set so as to be positioned in the vicinity of the inner side with respect to the incident portion interface.
Thereby, the characteristic change of the part excited by the measurement light before being largely attenuated in the sample can be measured by the investigation light. As a result, a sample having a high absorbance can be measured with high accuracy without using a particularly strong measurement light.

Further, in the measurement, if a sample container in which a fluid sample is filled and a wall is formed through which the measurement light and the survey light are transmitted from the outside to the filling portion of the sample is used, The absorbance of these samples can also be measured.
In this sample container, the inner surface of the wall that transmits the measurement light protrudes from the filling portion of the sample, or a mask that restricts the transmission region of the measurement light to the wall that transmits the measurement light. Those provided with are desirable.
As a result, when the intersection of the survey light and the measurement light is positioned near the interface of the measurement light incident portion in the sample (that is, the inner wall of the sample container), one of the survey lights up to the intersection is obtained. It can be prevented that the portion is wasted from protruding into the wall of the sample container (portion other than the measurement site in the sample). The mask can adjust the width of the measurement light (the size of the cross section) at the intersection with the survey light, that is, the size of the measurement site of the sample in the survey light direction.
Further, if the investigation light change measuring means measures the change in phase of the investigation light caused by crossing the measurement light in the sample with an optical interferometer, the change in the investigation light is optically increased. It can be measured with accuracy.

Embodiments of the present invention will be described below with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: It is not the thing of the character which limits the technical scope of this invention.
Here, FIG. 1 is a schematic configuration diagram of an absorbance measuring device X according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a first example of a liquid sample measured by the absorbance measuring device X and a cell containing it. FIG. 3 is a cross-sectional view showing a second example of a liquid sample measured by the absorbance measurement apparatus X and a cell containing the liquid sample, and FIG. 4 is a case where a plurality of liquid samples are measured by the absorbance measurement apparatus X under predetermined experimental conditions. FIG. 5 is a graph showing the amount of change in interference light intensity detected by the photodetector, FIG. 5 is a graph showing the results of measuring the absorbance of a predetermined liquid sample with a conventional transmission type absorbance measurement device, and FIGS. It is graph (1)-(3) showing the result of having simulated the relationship between the unit light absorbency of a sample, and the light absorbency in the measurement part of a sample by theoretical calculation.

Hereinafter, the absorbance measuring apparatus X according to the embodiment of the present invention will be described with reference to FIG. This absorbance measurement apparatus X is used to measure the absorbance of the sample 5, irradiates the sample 5 with the measurement light P3, measures the characteristic change (refractive index change) caused by the photothermal effect of the sample 5, and measures the measurement. This is an apparatus for calculating (measuring) the absorbance of the sample 5 based on the result. Although the embodiment described below shows an example in which the sample 5 is a liquid sample (an example of a fluid sample), the embodiment can be similarly performed even when the sample 5 is a solid.
As shown in FIG. 1, the absorbance measurement apparatus X includes a measurement light source 1, a chopper 2, optical devices 3, 4, 6, 8 to 19 such as a lens, a laser light source 7, a photodetector 20, a signal processing device 21, and the like. I have.
Further, the absorbance measurement apparatus X includes a cell S that is a sample container in which the liquid sample 5 is filled, and the liquid sample 5 is measured in a state of being filled (accommodated) in the cell S.
The measurement light P3 output from a predetermined measurement light source 1 (for example, a laser having a wavelength of 533 nm and an output of 100 mW (YAG harmonic)) that emits measurement light that is to be measured for absorbance is measured by the bandpass optical filter 1a in its frequency band. (Wavelength) is adjusted, and the measurement light P3 after adjusting the frequency band is converted into intermittent light (intermittent frequency: f) by the chopper 2 (that is, intensity modulated periodically). The measurement light P <b> 3 converted into intermittent light by the chopper 2 passes through the lens 3 and is irradiated onto the liquid sample 5. Thereby, the liquid sample 5 absorbs the measurement light P3 and generates heat (photothermal effect), and the refractive index of the liquid sample 5 changes due to the temperature change (rise).
On the other hand, the investigation light output from a laser light source 7 (for example, a He-Ne laser having an output of 1 mW) that emits investigation light (probe light) for measuring the refractive index change of the liquid sample 5 is a half-wave plate. The polarization plane is adjusted by 8 and further split into two polarized waves (P 1, P 2) orthogonal to each other by a polarization beam splitter (PBS) 9.
The polarizations P1 and P2 are shifted in frequency (frequency conversion) by the acousto-optic modulators (AOM) 10 and 11, reflected by the mirrors 12 and 13, and then synthesized by the polarization beam splitter 14. . Frequency difference f _b of 2 to these orthogonal polarization P1, P2, for example, a 30MHz or the like.
One polarization P2 of the combined investigation light passes through (transmits) the polarization beam splitter 15 and is reflected by the mirror 18, thereby returning to the polarization beam splitter 15 again. Here, the polarization P2 that has returned to the polarization beam splitter 15 reciprocally passes through the quarter-wave plate 16 disposed between the polarization beam splitter 15 and the mirror 18, so that the polarization plane is 90 °. Since it is rotating, it is reflected by the polarization beam splitter 15 and is directed toward the photodetector 20.

On the other hand, the other polarization P1 of the synthesized investigation light is reflected by the polarization beam splitter 15, passes through the quarter-wave plate 17 and the lens 4, and enters the liquid sample 5. Further, the measurement light P3 is also irradiated onto the liquid sample 5, and the measurement light P3 and the polarized light P1 (survey light) intersect in the liquid sample 5 filled in the cell S. That is, the investigation light (polarized light) P1 that is the measurement target light output from the laser light source 7 (an example of the investigation light irradiation means) is irradiated to the liquid sample 5 along one axial direction, and from a different direction, The measurement light P3 output from the measurement light source 1 (an example of measurement light irradiation means) is applied to the liquid sample 5. Hereinafter, a predetermined axial direction determined in advance for the cell S is referred to as a reference axis direction, and a portion where the measurement light P3 and the polarization P1 intersect (intersection) is referred to as a measurement unit 5a. In the embodiment described below, an example is shown in which the reference axis direction is the optical axis direction (irradiation direction) of the survey light (polarized light) P1.
Further, the polarized light P1 (survey light) incident on the liquid sample 5 passes through the measurement unit 5a of the liquid sample 5, and is on the back surface side of the liquid sample 5 (opposite surface opposite to the irradiation surface of the survey light (polarized light P1)). ) Is reflected by the reflecting mirror 6 provided on the liquid sample 5, passes through the measurement unit 5 a of the liquid sample 5 again (that is, reciprocates), passes through the lens 4 and the quarter-wave plate 17, and passes through the polarizing beam splitter. Return to 15. Here, since the polarization plane of the polarized light P1 (survey light) is rotated 90 ° by reciprocating through the quarter-wave plate 17, this time, it passes through the polarization beam splitter 15 and the polarized light. It merges with the wave P <b> 2 and travels toward the photodetector 20.
A polarizing plate 19 is disposed between the polarizing beam splitter 15 and the photodetector 20, and in the polarizing plate 19, the polarization P1 and the polarization P2 having an optical frequency different from that of the polarization P1 are: Each of them interferes as observation light (survey light) and reference light, and the light intensity of the interference light is converted into an electric signal (hereinafter, the signal value of the electric signal is referred to as interference light intensity) by the photodetector 20 (photoelectric conversion means). Converted. This electric signal (that is, the interference light intensity) is input and stored in a signal processing device 21 composed of a computer or the like, and the signal processing device 21 calculates (calculates) a phase change of the polarization P1 (survey light) ( That is, phase change is measured by optical interferometry.
Here, an optical system device that guides the polarizations P1 and P2 in a predetermined direction, the polarizing plate 19 that forms interference light of the polarizations P1 and P2 (survey light and reference light), and the photodetector 20 respectively. The signal processing device 21 constitutes an optical interferometer, which is an example of a survey light change measuring means.

Here, the interference light intensity Sv is expressed by the following equation (1).

Sv = C1 + C2 · cos (2π · f _b · t + φ) (1)

In this equation (1), C1 and C2 are constants determined by the transmittance of an optical system such as a polarizing beam splitter and the liquid sample 5, φ is a phase difference due to the optical path length difference between the polarizations P1 and P2, and f _b is bipolar. This is the frequency difference between the waves P1 and P2.
From equation (1), the change Δφ in the phase difference φ can be obtained from the change in the interference light intensity Sv (the difference between when the measurement light is not irradiated or when the light intensity is low and when the light intensity is high). I understand. The signal processing device 21 calculates the change Δφ of the phase difference φ based on the equation (1).
Further, in the measurement unit 5a of the liquid sample 5, the endothermic amount (heat generation amount) changes according to the amount of the predetermined contained substance that absorbs the measurement light P3, and the refractive index of the measurement unit 5a changes according to the heat generation amount, The phase difference φ (the optical path length of the polarization P1 in the liquid sample 5) changes according to the refractive index. That is, the greater the amount of the substance that absorbs the measurement light P3, the greater the change Δφ of the phase difference φ relative to the change of the measurement light P3 (that is, the phase change of the survey wave P1). Therefore, if the phase difference φ is measured, the change in the refractive index caused by the temperature change of the liquid sample 5 can be obtained, and as a result, the absorbance of the liquid sample 5 having a high correlation with the change in the refractive index of the liquid sample 5 can be obtained. It becomes.
For example, the absorbance measurement apparatus X is used to measure (calculate) the phase difference change Δφ for a plurality of types of sample samples whose absorbances are known in advance, and to signal the correspondence between the result and the absorbance of the sample sample. The data is stored in the processing device 21 as a conversion data table or a conversion formula.
Then, the measurement result (calculation result) of the phase difference change Δφ for the liquid sample 5 to be measured is subjected to interpolation processing based on the conversion data table, conversion processing based on the conversion formula, etc. 5 may be executed by the signal processing device 21 (an example of absorbance calculating means).
In this way, the absorbance measurement apparatus X firstly investigates light (the polarization P1) obtained by passing (transmitting) the refractive index change of the liquid sample 5 caused by irradiation with the measurement light P3 through the measurement unit 5a of the liquid sample 5. Phase change (phase change due to irradiation of the measurement light P3). In addition, the phase change is measured by using a light interferometer (light interferometry) to make a relative evaluation (phase difference) between the phase of the reference light (the polarization P2) and the phase of the investigation light (the polarization P1). To detect (measure). Thereby, for example, even if the position of the photodetector 20, the intensity of the investigation light P1 and the intensity distribution thereof are different for each apparatus, the optical apparatus can be stably and optically independent without depending on these as long as it does not change during measurement. Therefore, it is possible to measure the refractive index change of the sample with high accuracy.

Further, in the present absorbance measurement apparatus X, the investigation light (polarized wave P1) is reciprocally passed through the liquid sample 5 by reflecting the investigation light (polarized light P1) on the reflection mirror 6 on the back side, and after the reciprocating passage. Therefore, the phase difference change Δφ can be measured with twice the sensitivity of one-way passage. In addition, there is no increase in the output of the measurement light and no decrease in the S / N ratio.
Further, since the measurement light is intensity-modulated at the frequency f, the refractive index of the liquid sample 5 also changes at the frequency f, and the optical path length of the polarization P1 also changes at the frequency f (the optical path length of the polarization P2 is constant). ), The phase difference φ also varies with the frequency f. Therefore, if the change Δφ of the phase difference φ is measured (calculated) with respect to the frequency f component (the same period component as the intensity modulation period of the excitation signal), the influence of noise having no frequency f component is removed. Only the refractive index change of the liquid sample 5 can be measured.
Thereby, the S / N ratio in the measurement of the phase difference φ is improved.

As described above, the measurement light P3 and the polarized light P1 (survey light) are applied to the liquid sample 5 so as to intersect within the accommodating portion Sa of the cell S. At this time, the survey light P1 and the measurement light P3 are The liquid sample 5 is irradiated through the wall of the cell S (transmitted). Here, the cell S (wall) is made of a material such as quartz that transmits the investigation light P1 and the measurement light P3. However, the material of the wall of the cell S is desirably a material that does not absorb light (at least in the observation wavelength band) with respect to the measurement light P3.
In the present embodiment, the inner surface of the wall of the cell S is formed in a substantially rectangular parallelepiped shape, and the reference axis direction is substantially perpendicular to the wall surface of the cell S (incident surface of the investigation light P1). It is configured (arranged) to be in the direction.
FIG. 1 shows an example in which the reference axis direction and the irradiation direction of the measurement light P3 are substantially orthogonal to each other. However, the present invention is not limited to this, and it is conceivable to cross each other diagonally.
1 shows a configuration in which the investigation light P1 is reflected by the reflection mirror 6 and turned back (reciprocates through the liquid sample 5). However, the configuration is not limited to this. For example, the reference light P2 is directed downward in FIG. A configuration is also conceivable in which the investigation light P1 is allowed to pass through the liquid sample 5 only in one direction, for example, by guiding it. Alternatively, a configuration in which the investigation light P1 is subjected to multiple reflections on both sides of the liquid sample 5 and allowed to interfere with the reference light P2 after passing through the liquid sample 5 three times or more is also conceivable.

Next, an example of a state in which the investigation light P1 and the measurement light P3 are irradiated on the cell S and the liquid sample 5 filled in the cell S will be described with reference to FIG.
Here, FIG. 2 is a cross-sectional view showing a first example of the liquid sample 5 and the cell S that accommodates it.
The cell S is a container in which the liquid sample 5 is filled, and a wall in which the measurement light P3 and the survey light P1 are transmitted through the filling portion of the liquid sample 5 from the outside is formed. The wall is, for example, a quartz member. FIG. 2 shows an example in which the reflection mirror 6 shown in FIG. 1 is omitted and the investigation light P1 is passed through the liquid sample 5 only in one direction for measurement.
The cell S shown in FIG. 2 has a cubic column shape whose inner shape (the shape of the filling portion of the liquid sample 5) has a rectangular cross section with dimensions Rx × Ry.
The intersection (measuring part 5a) of the measuring light P3 and the investigation light P1 in the liquid sample 5 is on the interface of the measuring light P3 in the liquid sample 5 (that is, the inner wall surface Sif of the cell S on the measuring light P3 incident side). On the other hand, the optical paths of the measurement light P3 and the investigation light P1 are set so as to be positioned in the vicinity of the inside. This is preset by selection and arrangement of each optical system.
As a result, the portion excited by the measurement light P3 before being largely attenuated in the liquid sample 5 is used as the measurement unit 5a, and the characteristic change (refractive index change) of the measurement unit 5a can be measured by the investigation light P1.
Further, the optical axis direction (the reference direction) of the investigation light P1 in the liquid sample 5 is set to be parallel to the incident portion interface (inner wall surface Sif of the cell S) of the measurement light P1 in the liquid sample 5. ing.
Thereby, even if the optical path of the investigation light P1 is brought close to the incident portion interface (inner wall surface Sif of the cell S) of the measurement light P1 in the liquid sample 5, a part of the investigation light P1 is a portion outside the liquid sample 5 ( Here, it is possible to prevent the waste from protruding to the wall of the cell S.

Hereinafter, conditions and results of some experiments in which the absorbance of the liquid sample 5 was measured using the absorbance measurement apparatus X will be described.
The conditions of this experiment are as follows.
(1) Cell S
The inner shape of the cell S (the shape of the filling portion of the liquid sample 5) is a cubic column having a cross section of 3.0 mm × 3.0 mm (Rx × Ry in FIG. 2). The wall of the cell S is quartz having a thickness of 1.0 mm.
(2) Measurement light P3 (excitation light)
The measurement light source 1 was a xenon lamp (power consumption: 250 mW), and the wavelength band of the measurement light P3 was set in the range of 480 ± 5 nm by the bandpass optical filter 1a. The bandpass optical filter 1a has a wavelength band of 480 ± 5 nm for light having a transmittance of 45% or more.
Further, the lens 3 focused the measurement light P3 so that the diameter of the measurement light P3 was 2 mm at the intersection (measurement part) with the investigation light.
The measurement light P3 was converted by the chopper 2 into a pulse shape having a frequency of 100 Hz and a pulse width of 50%.
(3) Survey light P1
The laser light source 7 is a He—Ne laser (output: 1 mW), and the wavelength of the survey light P1 output thereby is 633 nm. The diameter of the survey light P1 at the intersection (measurement portion) with the measurement light P1 was 50 μm (intensity half-value width).
The optical axis direction (reference direction) of the investigation light P1 in the liquid sample 5 is parallel to the incident part interface of the measurement light P3 in the liquid sample 5 (that is, the inner wall surface Sif of the cell S on the incident side of the measurement light P3). The liquid sample 5 was irradiated with the survey light P1 so that
(4) Liquid sample 5
A liquid sample 5 which is a high concentration aqueous solution of a dye was used as a model sample to be measured for absorbance. The dye was “SunsetYellowFCF”, and the absorbance of the liquid sample 5 was adjusted by changing its concentration. That is, the measurement was performed for each of the plurality of liquid samples 5 having different dye concentrations. The solvent is pure water.
(5) Others The intersection angle between the investigation light P1 and the measurement light P3 was set to 90 °.
The entire intersection (measuring part 5a) of the measuring light P3 and the investigation light P1 in the liquid sample 5 is the incident part interface of the measuring light P3 in the liquid sample 5 (that is, the inner wall surface Sif of the cell S on the incident side of the measuring light P3). ) To be located within 50 μm inside.

FIG. 4 shows the amount of change in interference light intensity detected through the photodetector 20 when each of the seven types of liquid samples 5 having different dye concentrations is measured with the absorbance measurement device X under the experimental conditions described above. It is a graph. The horizontal axis of the graph represents the calculated value of the absorbance per unit length (optical path length 1 cm) of each liquid sample 5 (hereinafter referred to as unit absorbance [cm ⁻¹ ]), and the vertical axis is excited. An index value indicating the magnitude of the phase change (phase difference φ due to the optical path length difference between the polarizations P1 and P2) caused by passing through the measurement unit 5b (hereinafter, change measurement of the investigation light P1) Referred to as value). The horizontal axis is a logarithmic axis.
The unit absorbance of the liquid sample 5 when the wavelength band of the measurement light P3 is 480 ± 5 nm is 9.25 × 10 ⁰ [cm ⁻¹ ], 2.31 × 10 ¹ [cm ⁻¹ ], 4.62 respectively. × 10 ¹ [cm ⁻¹ ], 9.25 × 10 ¹ [cm ⁻¹ ], 1.38 × 10 ² [cm ⁻¹ ], 1.85 × 10 ² [cm ⁻¹ ], 2.31 × 10 ² [cm ⁻¹ ]. The unit absorbance of these liquid samples 5 is a theoretical value obtained based on the concentration of the pigment since the unit absorbance of the pigment and pure water (solvent) is known.
As shown in the graph of FIG. 4, the unit absorbance and the measured change value of the investigation light P1 show a high correlation.
In addition, it can be seen that the absorbance can be measured with high sensitivity and high accuracy even in the case of the liquid sample 5 having a high light absorption rate of unit absorbance of 46.2 [cm ⁻¹ ] to 231 [cm ⁻¹ ].
That is, based on the graph of FIG. 4, a conversion formula or conversion table for converting the change amount ΔSv of the interference light intensity into unit absorbance is stored in the storage unit of the signal processing device 21 in advance. Then, the signal processing device 21 (computer) executes a predetermined program to convert the change amount ΔSv of the interference light intensity obtained through the photodetector 20 into unit absorbance, and convert the unit absorbance into absorbance. do it. Here, since the thickness of the measurement site of the liquid sample 5 (the intersection of the measurement light P3 and the survey light P1) in the direction of the measurement light P3 is known, the thickness and the thickness of the liquid sample 5 for which the absorbance is to be obtained are calculated. If the unit absorbance [cm ⁻¹ ] is converted according to the ratio, the absorbance (generally referred to as Abs (no unit)) can be obtained. Of course, the conversion equation or the conversion table itself may be converted into one that converts the change amount ΔSv of the interference light intensity into the absorbance.

Incidentally, FIG. 5 is a graph showing the result of measuring the absorbance of the same liquid sample 5 as in the above-described experiment using a conventional transmission type absorbance measurement apparatus.
Here, FIG. 5A shows the measurement result of the liquid sample 5 having a unit absorbance of 23.1 [cm ⁻¹ ] with respect to the measurement light P3 having a wavelength band of 480 ± 5 nm, and FIG. The measurement result of the liquid sample 5 whose unit absorbance is 46.2 [cm ⁻¹ ], FIG. 5C shows the measurement result of the liquid sample 5 whose unit absorbance is 92.5 [cm ⁻¹ ]. In any case, the thickness of the liquid sample 5 (the thickness in the optical axis direction of the measurement light P3) is 1 mm. The horizontal axis represents the wavelength [nm] of the measurement light P3, and the vertical axis represents the absorbance (Abs).
Here, when the data of the part (the part indicated by OL in the figure) where the wavelength band of the measurement light P3 in each of the graphs shown in FIG. 5 is 480 ± 5 nm is shown, the graphs (b) and (c) of FIG. When the unit absorbance is 46.2 [cm ⁻¹ ] or more), the measured value vibrates and becomes very unstable. This indicates that since the absorbance of the liquid sample 5 is too high, the intensity of the measurement light after passing through the liquid sample 5 is so weak that measurement is impossible. Thus, in a conventional transmission type absorbance measurement apparatus, the absorbance cannot be measured for a sample having a unit absorbance of 50.0 [cm ⁻¹ ] or more even if the thickness is reduced to 1 mm. Further, as described above, the thinner the sample is, the more problems arise in managing the thickness of the sample and the complexity of handling.
Comparing FIG. 5 with FIG. 4 described above, the absorbance measurement apparatus X according to the embodiment of the present invention can measure the absorbance of a sample whose unit absorbance is too high to be measured by a conventional transmission type absorbance measurement apparatus. It can be seen that it can be measured. Moreover, it is not necessary to reduce the thickness of the sample in particular (the thickness of the liquid sample 5 is 3 mm under the above-described experimental conditions), and the sample is easy to handle.

Next, referring to FIG. 3, in addition to the state in which the investigation light P <b> 1 and the measurement light P <b> 3 are irradiated to the cell S ′, which is another embodiment of the cell S described above, and the liquid sample 5 filled therein. An example will be described.
Here, FIG. 3 is a cross-sectional view showing a second example of the liquid sample 5 and the cell S ′ (sample container) that accommodates it. 3 also shows an example in which the reflection mirror 6 shown in FIG. 1 is omitted, and the investigation light P1 is passed through the liquid sample 5 in only one direction for measurement.
Similarly to the cell S, the cell S ′ is a container in which walls for allowing the measurement light P3 and the investigation light P1 to pass through the filling portion of the liquid sample 5 from the outside are formed. The wall is, for example, a quartz member. As the material of the wall of the cell S, an appropriate material may be adopted according to the wavelength range of the measurement light. For example, when the measurement light is infrared light, it is preferable to use calcium fluoride or the like having good infrared light transmission as the material of the wall of the cell S.
The cell S ′ shown in FIG. 3 has the same configuration as that of the cell S shown in FIG.
The cell S ′ shown in FIG. 3 differs from the cell S described above in the following two points.
One of them is that the inner side surface Sif ′ of the wall through which the measurement light P3 in the cell S ′ is transmitted protrudes from the filling portion of the liquid sample 5.
The second point is that a mask Sk that restricts a transmission region of the measurement light P3 is provided on a wall (here, the outside of the wall) that transmits the measurement light P3 in the cell S ′. This mask Sk is provided with an opening for allowing the measurement light P3 to pass through a part of a member that blocks (not transmits) the measurement light P3.
Also in the example shown in FIG. 3, the optical axis direction (the reference direction) of the investigation light P1 in the liquid sample 5 is on the incident portion interface (the inner wall surface Sif ′ of the cell S ′) of the measurement light P1 in the liquid sample 5. It is set so that it may become parallel to it.
Furthermore, the intersection (measuring part 5a) of the measuring light P3 and the investigation light P1 in the liquid sample 5 is an incident part interface of the measuring light P3 in the liquid sample 5 (that is, the inner wall surface Sif of the cell S on the incident side of the measuring light P3). The optical paths of the measurement light P3 and the investigation light P1 are set so as to be positioned in the vicinity of the inside with respect to ').

As shown in FIG. 3, since the inner side surface Sif ′ of the wall of the cell S ′ is formed so as to protrude, the vicinity of the incident part interface of the measurement light P3 in the liquid sample 5 (the neighborhood of the wall surface Sif ′ inside the cell S ′) ), When the intersecting portion (measurement portion 5b) of the investigation light P1 and the measurement light P3 is positioned, a part of the investigation light P1 up to the intersection is within the cell S ′ wall (in the liquid sample 5). It is possible to prevent the waste from protruding to the portion other than the measuring unit 5b.
In addition, the mask Sk can adjust the width (cross-sectional size) of the measurement light P3 at the intersection (measurement unit 5b) with the investigation light P1, that is, the dimension of the measurement unit 5b in the direction of the investigation light P1.

In the embodiment described above, the signal processing device 21 calculates the phase difference change Δφ (phase change of the survey wave P1) from the interference light intensity Sv detected by the photodetector 20 based on the equation (1). Further, the calculation of the absorbance of the sample 5 from the change Δφ in the phase difference was shown using a conversion data table and a conversion equation based on the measurement result of the sample sample whose absorbance is known in advance.
In addition, the absorbance of the sample 5 can be calculated from the interference light intensity Sv detected by the photodetector 20 based on a theoretical calculation formula. The contents will be described below.
Here, the change amount of the optical path length of the investigation wave P1 due to the investigation wave P1 intersecting with the measurement wave P3 is ΔL, and the temperature change of the measurement part 5b (intersection part) of the liquid sample 5 due to the irradiation of the measurement wave P3 is ΔT, Theoretically, the following equation (2) is established, where d is the length of the measurement unit 5b in the direction of the survey wave P1, and the refractive index temperature coefficient of the solvent of the liquid sample 5 is dn / dT.

ΔL = dn / dT · ΔT · d (2)

In this equation (2), dn / dT and d can be known in advance, so if ΔL is measured, ΔT can be calculated based on equation (2).

Further, when the energy absorbed by the measurement unit 5b of the liquid sample 5 (that is, the amount of heat generated by the measurement unit 5b) is ΔI and the heat capacity of the liquid sample 5 is C, the following equation (3) is established. To do. However, in equation (3), the amount of heat escape due to heat conduction in the liquid sample 5 is ignored.

ΔT = ΔI / C (3)

In this equation (3), C can be known in advance. Therefore, if ΔT is calculated based on equation (2), ΔI can be calculated based on equation (3).
When the energy of the measurement light P3 immediately before entering the measurement part 5b of the liquid sample 5 is I ₀ and the energy of the measurement light P3 immediately after passing through the measurement part 5b is I, the following equation (4) is established.

ΔI = I ₀ −I (4)

Here, attenuation of the measurement light P3 in the optical path until it enters the liquid sample 5 (attenuation in the air and the wall of the cell S) can be assumed in advance according to the type of measurement light to be used. For this reason, if the measurement unit 5b (intersection) is substantially in contact with the incident part interface of the measurement light P3 in the liquid sample 5, I ₀ can be assumed in advance. Therefore, if ΔI is calculated based on equation (3), I can be calculated based on equation (4).

On the other hand, the phase difference change Δφ (phase change of the survey wave P1) can be calculated from the interference light intensity Sv detected by the photodetector 20 based on the above-described equation (1).
If the wavelength of the survey wave P1 is λ1, ΔL can be calculated by the following equation (5).

ΔL = λ1 · Δφ / 2π (5)

As described above, Δφ can be calculated from the interference light intensity Sv detected by the photodetector 20, ΔL can be calculated from Δφ, I can be calculated from ΔL, and the measurement light P3 can be calculated based on the I and the known I _0. The absorbance A (= −log ₁₀ (I / I ₀ )) of the sample at the intersection (measurement unit 5b) with the survey light P1 can be calculated. Therefore, the signal processing device 21 (computer) can calculate the absorbance A by executing such calculation.
In addition, as shown in Patent Document 2, the inspection light P1 after crossing the measurement light P3 is passed through a pinhole, the intensity of the inspection light P1 after passing through the pinhole is detected by a photodetector, A process of calculating ΔL from the detected value may be executed by a computer.

On the other hand, the measurement unit 5b (intersection) is away from the interface of the measurement light P3 incident portion in the liquid sample 5, and the attenuation of the measurement light P3 from the incidence on the liquid sample 5 to the measurement portion 5b cannot be ignored. In this case, I ₀ needs to be obtained by subtracting the attenuation energy from the output energy of the measurement light source 1 to the measurement unit 5b.
In this case, the distance from the incident part interface (inner wall surfaces Sif, Sif ′ of the cells S, S ′) to the measuring part 5b (intersection) in the sample is x, and the absorbance per unit length of the sample (unit: (Absorbance) is B, and the energy (usually the output energy of the measurement light source 1) of the measurement light P3 at the interface (the inner wall surface Sif, Sif ′ of the cells S, S ′) of the measurement light P3 in the sample is I ₀ ( 0), I ₀ can be obtained by the following equation (6) as a function of the distance x.

I ₀ (x) = I ₀ (0) · (1-10 ^−Bx ) (6)

If the above calculation is executed by the signal processing device 21 (computer), the absorbance can be calculated even when the measurement unit 5b (intersection) is away from the incident portion interface of the measurement light P3 in the liquid sample 5. .

Next, referring to the simulation data graphs shown in FIG. 6 to FIG. 8, the measurement unit 5 b (intersection) from the incident part interface (inner wall surface Sif, Sif ′ of the cells S, S ′) of the measurement light P <b> 3 in the sample. The relationship between the distance up to and the light absorption amount (that is, the heat absorption amount) of the measurement unit 5b will be described.
6 to 8 are graphs showing the results of simulation by theoretical calculation of the relationship between the unit absorbance of the sample (absorbance per 1 cm of the optical path length) and the amount of absorbance (endothermic amount) in the measurement unit 5b of the sample. FIG. 6, FIG. 7, and FIG. 8 show graphs when it is assumed that the beam diameter of the investigation light P1 is 10 μm, 50 μm, and 110 μm, respectively. The beam diameter of the investigation light P1 represents the width of the measurement unit 5b (intersection) in the irradiation direction of the measurement light P3.
The horizontal axis in each graph shown in FIGS. 6 to 8 is unit absorbance [cm ⁻¹ ] when a liquid sample 5 is irradiated with a certain measurement light P3, and the vertical axis is a sample measurement unit 5b (intersection). Represents the value obtained by converting the amount of absorption (endothermic amount) of the measurement light P3 into the amount of absorption per unit volume of the sample.
Also, a plurality of graph lines in each graph shown in FIG. 6 to FIG. 8 indicate from the incident part interface (inner wall surfaces Sif, Sif ′ of the cells S, S ′) to the center of the beam axis of the investigation light P1 in the sample. Are graph lines representing the data when the distance x is 0 μm (g100, g200, g300), 10 μm (g101, g201, g301), 20 μm (g102, g202, g302) Yes, it represents the result of simulation under the condition that the distance x is changed by 10 μm.

In any of the graphs shown in FIGS. 6 to 8, the slope is always positive in the range where the unit absorbance is 30 [cm ⁻¹ ] or less (the amount of absorbance increases as the unit absorbance increases). It can be seen that the distance x satisfies the condition of 150 μm or less (graphs g100 to g115, g200 to g215, g300 to g315). In other words, when the distance x exceeds 150 μm, when the unit absorbance is 30 [cm ⁻¹ ] or less, the slope becomes 0 or less (the amount of absorbance does not increase as the unit absorbance increases). I know you get.
Similarly, in any of the graphs shown in FIGS. 6 to 8, the slope is always positive when the unit absorbance is 40 [cm ⁻¹ ] or less when the distance x is 100 μm or less. (Graphs g100 to g110, g200 to g210, g300 to g310). In other words, when the distance x exceeds 100 μm, when the unit absorbance is 40 [cm ⁻¹ ] or less, the slope becomes 0 or less (the absorbance does not increase as the unit absorbance increases). I know you get.
In the absorbance measurement apparatus X, if the relationship that the calorific value of the measurement unit 5b increases as the unit absorbance of the sample increases, the absorbance of the measurement unit 5b can be measured. Conversely, if the relationship does not hold, the absorbance cannot be measured by the absorbance measuring device X.

From the above, when the unit absorbance (absorbance per unit length) of the sample with respect to the measurement light P3 is 30 [cm ⁻¹ ] or less, the intersection of the measurement light P3 and the investigation light P1 in the sample (measurement) If the part 5b) is set to be located within 150 μm inside (x ≦ 150 μm) with respect to the incident part interface (wall surface Sif, Sif ′) of the measurement light P3 in the sample, an effective absorbance measurement can be performed by the absorbance measuring device X. It can be said that it can be done.
Similarly, when the unit absorbance (absorbance per 1 cm of optical path length) of the sample with respect to the measurement light P3 is 40 [cm ⁻¹ ] or less, the intersection (measurement unit 5b) of the measurement light P3 and the investigation light P1 in the sample. ) Is set within 100 μm inside (x ≦ 100 μm) with respect to the incident part interface (wall surface Sif, Sif ′) of the measurement light P3 in the sample, the effective absorbance measurement is performed by the absorbance measuring device X Can be said.

  The present invention can be used for an absorbance measuring apparatus.

1 is a schematic configuration diagram of an absorbance measurement apparatus X according to an embodiment of the present invention. Sectional drawing showing the 1st example of the liquid sample measured with the light absorbency measuring apparatus X, and the cell which accommodates it. Sectional drawing showing the 2nd example of the liquid sample measured with the light absorbency measuring apparatus X, and the cell which accommodates it. 6 is a graph showing the amount of change in interference light intensity detected by a photodetector when a plurality of liquid samples are measured with the absorbance measurement device X under predetermined experimental conditions. The graph showing the result of having measured the light absorbency of the predetermined liquid sample with the conventional transmission type light absorbency measuring apparatus. The graph (1) showing the result of having simulated the relationship between the unit light absorbency of a sample, and the light absorbency in the measurement part of a sample by theoretical calculation. The graph (2) showing the result of having simulated the relationship between the unit light absorbency of a sample, and the light absorbency in the measurement part of a sample by theoretical calculation. The graph (3) showing the result of having simulated the relationship between the unit light absorbency of a sample, and the light absorbency in the measurement part of a sample by theoretical calculation.

X ... Absorbance measuring device 1 ... Measuring light source 1a ... Band pass optical filter 2 ... Chopper 3, 4 ... Lens 5 ... Sample (liquid sample)
5a ... Intersection of the survey light and the survey light (measurement unit)
6 ... Reflection mirror 7 ... Laser light source 10, 11 ... Acousto-optic modulator (AOM)
DESCRIPTION OF SYMBOLS 20 ... Photodetector 21 ... Signal processing apparatus S, S '... Cell (sample container)
Sk ... Mask P1 ... Polarization (Survey light)
P2: Polarization (reference light)
P3 ... Measurement light Sif, Sif '... Inner wall surface of measurement light incident side cell

Claims (11)

An absorbance measurement device for measuring the absorbance of a sample,
Survey light irradiation means for irradiating the sample with predetermined survey light;
A measuring light irradiating means for irradiating the sample with measuring light to be measured for absorbance so as to intersect the investigating light within the sample;
Investigation light change measuring means for measuring a change in phase of the investigation light due to crossing the measurement light in the sample;
Absorbance calculation means for calculating the absorbance of the sample for the measurement light based on the measurement result of the survey light change measurement means;
An absorbance measuring apparatus comprising:   The absorbance measurement apparatus according to claim 1, wherein an intersecting portion of the measurement light and the investigation light in the sample is set to be located in the vicinity of an inner side with respect to an incident portion interface of the measurement light in the sample.   The absorbance measuring apparatus according to claim 2, wherein the optical axis direction of the inspection light in the sample is set so as to be substantially parallel to an interface of the measurement light on the sample.   4. A container filled with the fluid sample, comprising a sample container formed with a wall through which the measuring light and the investigation light are transmitted from the outside to the filling portion of the sample. The absorbance measuring apparatus according to any one of the above.   The absorbance measuring apparatus according to claim 4, wherein an inner side surface of a wall that transmits the measurement light in the sample container is formed to protrude from the filling portion of the sample.   The absorbance measuring apparatus according to claim 4, wherein a mask that restricts a transmission region of the measurement light is provided on a wall of the sample container that transmits the measurement light.   The absorbance measurement according to any one of claims 1 to 6, wherein the investigation light change measuring means measures a change in phase of the investigation light caused by crossing the measurement light in the sample with an optical interferometer. apparatus. An absorbance measurement method for measuring the absorbance of a sample,
Investigation light irradiation procedure for irradiating the sample with the emitted light of a light source that emits predetermined investigation light;
A measurement light irradiation procedure for irradiating the sample with measurement light to be measured for absorbance so as to cross the inspection light within the sample;
Investigation light change measurement procedure for measuring a change in phase of the investigation light caused by crossing the measurement light in the sample through a predetermined light measurement means;
Absorbance calculation procedure for calculating the absorbance of the sample for the measurement light based on the measurement result of the survey light change measurement procedure with a predetermined calculator;
A method for measuring absorbance, comprising:   The absorbance measurement method according to claim 8, wherein an intersection of the measurement light and the investigation light in the sample is set so as to be positioned in the vicinity of an inner side with respect to an incident part interface of the measurement light in the sample. When the absorbance per unit length of the sample with respect to the measurement light (unit absorbance) is 30 [cm ⁻¹ ] or less, the intersection of the measurement light and the investigation light in the sample is The absorbance measurement method according to claim 9, wherein the absorbance measurement method is set so as to be located within 150 μm on the inner side of the measurement light incident part interface. When the absorbance per unit length of the sample with respect to the measurement light (unit absorbance) is 40 [cm ⁻¹ ] or less, the intersection of the measurement light and the investigation light in the sample is The absorbance measurement method according to claim 9, wherein the absorbance measurement method is set so as to be located within 100 μm on the inner side with respect to the incident portion interface of the measurement light.

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