JPH0643095A - Near-infrared analyzer - Google Patents

Abstract

PURPOSE:To provide a device for quantitatively analyzing accurately by utilizing near-infrared rays, without being influenced by fluctuation factors of the temperature and moisture of a sample, etc., in absorvance. CONSTITUTION:The measurement of a reference spectrum is made fixed times by a reference plate, and then the average thereof is found (S1 to S4). Similarly, the measurement of a spectrum is made fixed times about an unknown sample, and then the average thereof is found (S5 to S8). After the absorvance is found from both spectra, the differential processing thereof is made (S9, 10), and the temperature of the sample is operated on the basis of the measured spectrum data (S11). The difference between the found sample temperature and the reference temperature in the time when the analytical curve is generated is found (S12), and the shift quantity between the measured spectrum and the spectrum in the time when the analytical curve is generated is found from the temperature difference (S13). The operation for correcting it to the spectrum under the reference temperature is made by using the shift quantity (S14). After the corrected absorvance is secondarily differentiated (S15), the computation for estimating the concentration of a fixed component of the sample is made from the secondarily differentiated absorvance by using the analytical curve, to be displayed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a near-infrared analyzer for performing quantitative analysis using near-infrared rays.

[0002]

2. Description of the Related Art Conventionally, a calibration curve necessary for performing quantitative analysis using near infrared rays is that a standard sample whose concentration of a measurement component is known is irradiated with near infrared rays and the absorbance is measured. It was created based on known concentrations.

[0003]

However, the absorbance is
Since it fluctuates due to external fluctuation characteristics such as sample temperature, water content, crushed particle size, etc., estimating the component concentration of an unknown sample with a calibration curve created as in the past will make the estimated value unstable and put it to practical use. However, there were problems such as the need to control the temperature of unknown samples.

Therefore, the present invention is to provide an apparatus capable of performing a quantitative analysis accurately by utilizing near infrared rays without being influenced by factors such as the temperature of the sample and the fluctuation of the absorbance such as moisture. To aim.

[0005]

In order to achieve the above object, the present invention has the following constitution. That is, the present invention, the absorbance measurement means for irradiating the sample with near-infrared light to measure the absorbance, and known samples, the reference absorbance for creating a calibration curve and the absorbance at the time of a predetermined external variation characteristic value. , A deviation amount calculating means for preliminarily measuring by the absorbance measuring means and obtaining a deviation amount of both absorbances, a storage means for storing the calculated deviation amount, and an external fluctuation for measuring an external fluctuation characteristic value of an unknown sample Characteristic value measuring means and unknown sample, when the absorbance is measured by the absorbance measuring means, according to the measurement value of the external fluctuation characteristic value measuring means, the measured absorbance by the deviation amount stored in the storage means It is provided with a measurement absorbance correction unit that corrects to the reference absorbance and an analysis unit that analyzes the sample component by the calibration curve based on the corrected absorbance.

[0006]

In the present invention having such a configuration, the absorbance of the known sample is determined by the absorbance measuring means when the reference absorbance for creating the calibration curve and the predetermined external variation characteristic value such as temperature or water content are obtained. Measure in advance. The shift amount calculating means calculates the shift amount of the absorbance of the both, and the calculated shift amount is stored in the storage means in advance.

Next, when the components of an unknown sample are measured, the absorbance of the sample is measured by the absorbance measuring means and the external fluctuation characteristic value of the sample is measured by the external fluctuation characteristic value measuring means. The measured absorbance correction means corrects the measured absorbance to the reference absorbance according to the measured external fluctuation characteristic value by the shift amount stored in the storage means. The analyzing means analyzes the sample components based on the corrected absorbance by a calibration curve obtained from the reference absorbance.

As described above, according to the present invention, the measured absorbance is corrected to the reference absorbance for preparing the calibration curve by the deviation amount of the absorbance of the sample according to the external variation characteristic value, and the calibration curve is applied to the calibration curve. In some cases, quantitative analysis can be performed accurately without being affected by factors such as the temperature and water content of the sample that change in absorbance.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

In this embodiment, as shown in FIG. 1, a near-infrared spectroscopic device 1 and a control processing device 2 for controlling each part of the near-infrared spectroscopic device 1 and processing data obtained from the device 1. ,,.

The near-infrared spectroscopic device 1 is for irradiating near-infrared rays on a sample (sample) such as an agricultural product by continuously changing the wavelength and detecting transmitted light or reflected light of the sample. That is, the near-infrared spectroscopic device 1 includes a light source 3, a reflecting mirror 4, a diffraction grating 6 driven by a diffraction grating driving motor 5, a sample cell holder 7 for mounting a sample cell filled with a sample, and a transmitted light of the sample. A transmitted light detector 8 for detecting,
A reflected light detector 9 for detecting reflected light from the sample is arranged as shown.

The sample cell holder 7 is moved to a measurement position by a sample cell transfer motor (not shown in FIG. 1) when the sample cell is set to a predetermined position during measurement, and the sample cell is returned to the predetermined position after the measurement is completed. To configure.

Next, a block diagram of the control processing system of the embodiment having such a configuration is shown in FIG. 2 and will be described.

In FIG. 2, reference numeral 20 denotes a one-chip type C.
It is a central processing unit (PU) and performs control processing as described below. The light source 3, the diffraction grating drive motor 5, the sample cell transfer motor 22, the transmitted light detector 8, and the reflected light detector 9 are connected to the CPU 20 via the input / output interface 21. In addition, the CPU 20 has an input interface 23.
The input key 24 is connected via the, and the display device 26 is connected via the output interface 25. Further, the CPU 20 is connected to a storage device 27 including a ROM for storing a processing procedure described later and a RAM for temporarily storing data.

Next, an example of the operation of the embodiment thus constructed will be described in detail below.

In this embodiment, the calibration curve of the sample at the reference temperature To (near 20 degrees Celsius) is determined as follows.

First, when the reference plate is set at the measurement position of the near-infrared spectroscope 1 and the near-infrared spectroscope 1 is operated, the near-infrared rays emitted from the light source 3 reach the diffraction grating 6 via the reflecting mirror 4. Then, after being dispersed here, it is reflected by the reference plate, and the reflected light is detected by the reflected light detector 9. Since the wavelength of the reflected light changes with the rotation of the diffraction grating 6, the reflected light detector 9 continuously detects a signal corresponding to the wavelength.
Therefore, the operation of reading the detection signal (measurement of the reference spectrum) is performed a predetermined number of times, and then the average of the spectrum is obtained.

Next, the sample cell containing the standard sample (the temperature is around 20 degrees Celsius) in which the concentration of the measurement component is known is set at the measurement position by driving the sample cell transfer motor 22. Then, when the near-infrared spectroscopic device 1 operates again, the reflected light detector 9 detects the reflected light from the standard sample. Therefore, after the spectrum of the standard sample is measured a predetermined number of times, the average of the measured spectra is obtained, and the absorbance is calculated from the control spectrum and the measured spectrum.

Then, the absorbance is obtained as described above for a plurality of standard samples having different concentrations, and the calibration curve at the reference temperature To (near 20 degrees Celsius) is obtained in advance based on the measured absorbance and the known concentration.

Further, with respect to a standard sample whose measured components are known, for example, respective absorbance spectra at temperatures near 3 degrees Celsius, near 20 degrees Celsius, and around 34 degrees Celsius are obtained. Using the spectrum as a reference, calculate the amount of deviation between it and the absorbance spectrum when the temperature is 3 degrees Celsius, and in advance calculate the amount of deviation between the absorbance spectrum when the temperature is 34 degrees Celsius and the above-mentioned reference spectrum. . Then, the calculated shift amounts are stored in the storage device 27 in advance.

Next, an example of the case where the component is measured by the calibration curve and the deviation amount obtained as described above for an unknown sample will be described with reference to the flowchart of FIG.

First, the reference plate is set at the measurement position, the near-infrared spectroscopic device 1 is operated to measure the reference spectrum Ro a predetermined number of times, and then the average of the reference spectrum Ro is obtained (S1 to S4).

Next, when the sample cell containing the sample to be measured is set at the measuring position, the near-infrared spectroscopic device 1 operates again,
After the spectrum R of the sample is measured a predetermined number of times, the average of the measured spectrum R is obtained (S5 to S8).

Subsequently, the absorbance OD is calculated from the control spectrum Ro and the measurement spectrum R obtained as described above by the following equation (1) (S9).

OD = logRo / R (1) Next, the obtained absorbance is differentiated (S1
0), the temperature Ts of the sample based on the measured spectrum data
Is calculated (S11). This calculation is to estimate the temperature Ts of the sample by utilizing the fact that there is a shift in the absorbance of near-infrared light with respect to the temperature change of the sample and there is a correlation between the two. The sample temperature Ts may be measured by a sensor.

Subsequently, the temperature difference ΔT between the estimated sample temperature Ts and the reference temperature To when the calibration curve is created is calculated by the following equation (2) (S12).

ΔT = Ts−To (2) Then, a deviation amount ΔODt between the measured spectrum and the spectrum at the time of creating the calibration curve is calculated from the calculated temperature difference ΔT (S13). By the way, the reference temperature To when the calibration curve is created
The shift amount between the spectrum below and the spectrum under a predetermined temperature in consideration of the external variation characteristic is stored in the storage device 27 as described above. Therefore, the above deviation amount ΔODt
Is calculated from the temperature difference ΔT as interpolation approximation by the stored deviation amount. Next, the calculated amount of deviation ΔOD
The calculation for correcting the spectrum under the reference temperature To using t is performed by the following equation (3) (S14).

OD '= OD-ΔODt (3) In equation (3), OD' is the corrected absorbance and OD is the absorbance determined in step S9.

Subsequently, the corrected absorbance OD 'is second-derivatively differentiated (S15), and then the concentration of a predetermined component of the sample is estimated using a calibration curve based on the second-order derivative absorbance (S16). Then, the result is displayed on the display device 26 (S17).

Next, the following experiment was conducted in order to confirm the accuracy of the near infrared analysis according to the example of the present invention.

In this test, unmilled brown rice was used as a sample, and a calibration curve for measuring the protein content of this brown rice was prepared in advance at a sample temperature of about 20 degrees Celsius.

Next, when the protein content of the sample was estimated using the above calibration curve for the sample at a temperature near 34 degrees Celsius, the results shown in FIG. 4 were obtained. Furthermore, when the protein content of the sample was estimated using the above calibration curve for the sample at a temperature near 3 degrees Celsius, the results shown in FIG. 5 were obtained. On the other hand, when the protein content of a sample of unknown temperature was estimated according to the example of the present invention, the results shown in FIG. 6 were obtained.

Therefore, comparing these experimental results,
If the component concentrations of the sample are estimated by the examples of the present invention, it can be seen that the accuracy is practically sufficient.

Next, an example of a quality evaluation device for displaying the component concentration of the sample obtained as described above on the display device 26 and evaluating the quality of the sample will be described below.

In this apparatus, the sample is unmilled brown rice,
The protein content and fatty acid content in the brown rice component are measured by the above-mentioned procedure. Then, the measurement result is displayed as dots at corresponding positions on the XY coordinates on the display screen of the display device 26 as shown in FIG. 7 or 8. This makes it possible to display the protein and the fatty acid in association with each other on the XY coordinates, which makes it very easy to understand the quality of the rice, which makes it easy to intuitively judge the quality of the rice. .

Further, an area can be arbitrarily set on the coordinates of the display screen of the display device 26 by operating the input key 24, as shown by the hatched portion in FIG. 7 or 8.
When a measured value is entered in the setting area, a warning sound, a warning display, or a control output is generated. As a result, quality control can be performed independently for each arbitrarily set area. Further, the warning sound and the warning display can prevent the sample in the setting area from being overlooked. Further, by issuing the control output, it becomes possible to select a desired sample, display quality, or perform secondary processing.

Next, another example of the quality evaluation device will be described below.

In this apparatus, the sample is unmilled brown rice,
Five kinds of evaluation indexes such as protein content and fatty acid content in the brown rice component are measured by the above-mentioned procedure. Then, the data relating to the two evaluation indexes of the measurement results are two-dimensionally displayed on the display screen of the display device 26 as shown in FIG. 7. However, since there are five kinds of evaluation indexes, there are 10 combinations to be displayed. Get on the street. Therefore, as shown in FIG. 9, five types of indexes “A” to “E” are displayed on the display screen of the display device, and when the operator selects two indexes from these, the selected indexes are selected. The data is displayed on the XY coordinates (map) and the display can be enlarged or reduced. Furthermore, it is configured so that a plurality of maps can be selected and displayed on the same screen. With such a configuration, operability in displaying combined evaluation indexes is improved.

A display example in which the predetermined index is selected in this way is shown in FIG. 10. As shown in the figure, the degree of fatty acid is 0 to 15 rather than equally divided on the absolute axis of 0 to 50 mg.
mg, 15-25 mg, etc.
From the viewpoint of functionality and operability, it is preferable that the display section can be arbitrarily set by the operator's setting, for example, by equally dividing the section of 25 mg. Therefore, for example, if the display section is set as shown by the shaded area in FIG.
It is configured to be converted into the display as shown in FIG.

[0040]

As described above, according to the present invention, the measured absorbance is corrected to the reference absorbance for preparing the calibration curve according to the deviation amount of the absorbance of the sample according to the external variation characteristic value, and the calibration curve is applied. Therefore, at the time of measurement, the quantitative analysis can be performed accurately without being affected by the fluctuation factors of the absorbance of the sample such as temperature and moisture.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of an embodiment of the present invention.

FIG. 2 is a block diagram of a control processing system thereof.

FIG. 3 is a block diagram showing an operation example of an embodiment of the present invention.

FIG. 4 is a diagram showing an example of a relationship between an actually measured value and an estimated value of a protein content of brown rice by a conventional method.

FIG. 5 is a diagram showing another example of the relationship between the measured value and the estimated value of the protein content of brown rice by the conventional method.

FIG. 6 is a diagram showing an example of a relationship between an actually measured value and an estimated value of a protein content of brown rice according to an example of the present invention.

FIG. 7 is a diagram showing an example of a two-dimensional display of the results of component measurement of a sample.

FIG. 8 is a diagram showing an example of a two-dimensional display of the results of component measurement of a sample.

FIG. 9 shows two of the cases where the evaluation index of the sample is plural.
It is an explanatory view for selecting two-dimensional display from one index.

FIG. 10 is a diagram showing a display example after selecting a desired evaluation index.

FIG. 11 is a diagram showing a display example after display section conversion.

[Explanation of symbols]

 1 near-infrared spectroscopic device 2 control processing device 20 CPU 27 storage device

Claims (1)

[Claims] 1. An absorbance measuring means for irradiating a sample with near-infrared rays to measure an absorbance, and a known sample, a reference absorbance for preparing a calibration curve and an absorbance at a predetermined external variation characteristic value, Displacement amount calculation means for obtaining the deviation amount between the two absorbances measured in advance by the absorbance measurement means, storage means for storing the calculated deviation amount, and external variation characteristic for measuring the external variation characteristic value of an unknown sample Value measuring means and unknown sample, when the absorbance is measured by the absorbance measuring means, the measured absorbance is stored in the storage means according to the measured value of the external fluctuation characteristic value measuring means, and Near-infrared light comprising: a measurement absorbance correction unit that corrects to a reference absorbance; and an analysis unit that analyzes a sample component by the calibration curve based on the corrected absorbance. Analysis apparatus.