JPH1068692A - Near-infrared analyzer - Google Patents

Abstract

(57) [Summary] [PROBLEMS] It is necessary to perform quantitative analysis with high accuracy without being influenced by the fluctuation factor of the absorbance of the temperature of a sample. An absorbance measuring means for irradiating a sample with near-infrared rays to measure absorbance, and for a known sample, a reference absorbance for preparing a calibration curve and an absorbance at a predetermined sample temperature, the absorbance measurement means By measuring in advance, a shift amount calculating means for obtaining the shift amount of the absorbance of both, storage means for storing the calculated shift amount, a temperature fluctuation characteristic value measuring means for measuring the temperature of the unknown sample,
For an unknown sample, when the absorbance is measured by the absorbance measurement means, the measurement absorbance correction means corrects the measured absorbance to the reference absorbance by a shift amount stored in the storage means according to the temperature fluctuation characteristic value measurement means. When,
A near-infrared spectrometer comprising: analysis means for analyzing a sample component based on the corrected absorbance based on the calibration curve.

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, as means utilizing near infrared rays, Japanese Patent Application Laid-Open Nos. 62-299743 and 63-1775
No. 47, Japanese Patent Application Laid-Open No. 64-49937 and the like.

[0003]

Problems to be Solved by the Invention
No. 9743, the means disclosed in JP-A-63-175747, for example, the seventh means of JP-A-62-299743.
As shown in the figure, the correction value of the measurement target value is uniquely determined with respect to the detected temperature value, and a typical example thereof is as follows.

Analysis value = K0 + K1 * {OD1 + K2 *}
OD2 + K3 * T, where K: coefficient ΔOD: (only two items are described, but there are actually many) T: detected temperature In this case, the detected temperature value is constant even if the analysis value is a high or low sample , The correction amount is also constant, but in the near-infrared analysis, there are a plurality of explanatory variables used for the calibration curve, and the temperature characteristics differ depending on the selected wavelength. For this reason, when the detected temperature is higher or lower than usual, there is a case where the gradient of the actual analysis value is significantly different from that of the sample whose actual analysis value is high or low. In particular, in agricultural products and foods containing water, the hydrogen bond of water molecules greatly changes depending on the temperature, which is remarkable. The temperature characteristics of the light absorption band and the non-absorption band of water are different. The tendency is remarkable.

Further, Japanese Patent Application Laid-Open No. Sho 64-49937 discloses that
Information about the light emission amount and peak wavelength of the light emitting diode as an optical element and the temperature characteristics of the light receiving output of the light receiving element are measured in advance and stored in the storage means, and the actual light amount measured value is measured for the hardware. Since the density measurement value is obtained by calibrating from the information stored based on the temperature, it is only related to the temperature correction of the optical densitometer hard for the purpose of measuring without error caused by the temperature change of the hard. The sample moisture,
It cannot be corrected in consideration of fluctuations due to temperature, particle size, and the like.

Accordingly, an object of the present invention is to provide an apparatus which can accurately perform quantitative analysis using near-infrared rays without being affected by a change in absorbance due to the temperature of a sample. .

[0007]

In order to achieve the above object, the present invention takes the following technical measures. That is, the absorbance measuring means for measuring the absorbance by irradiating the sample with near-infrared rays, and, for a known sample, the reference absorbance for preparing a calibration curve and the absorbance at a predetermined sample temperature are previously determined by the absorbance measuring means. Measured, a shift amount calculating means for obtaining the shift amount of the absorbance of both,
Storage means for storing the calculated shift amount; temperature fluctuation characteristic value measuring means for measuring the temperature of the unknown sample; and temperature fluctuation characteristic value measuring means for the unknown sample when the absorbance is measured by the absorbance measurement means. According to the measurement absorbance correction means for correcting the measured absorbance to the reference absorbance by the amount of shift stored in the storage means, and an analysis means for analyzing a sample component by the calibration curve based on the corrected absorbance A near-infrared analyzer

[0008]

The absorbance measurement means measures the absorbance of a known sample in advance as a reference absorbance for preparing a calibration curve and an absorbance at a temperature fluctuation characteristic value of a predetermined sample temperature. The shift amount calculating means calculates the shift amount between the two absorbances, and the storage means stores the calculated shift amount.

Next, when the component measurement is performed on the unknown sample, the temperature, which is the external fluctuation characteristic value of the sample, is measured by the temperature 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 by the amount of shift stored in the storage means. The analysis means analyzes the sample components based on the corrected absorbance using a calibration curve obtained from the reference absorbance.

[0010]

According to the present invention, the measured absorbance is corrected to the reference absorbance for preparing the calibration curve and applied to the calibration curve based on the deviation amount of the absorbance of the sample according to the external fluctuation characteristic value. Quantitative analysis can be performed accurately without being influenced by the fluctuation factor of the absorbance of the sample.

[0011]

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 spectroscopy device 1 and a control processing device 2 for controlling each part of the near-infrared spectroscopy device 1 and processing data obtained from the near-infrared spectroscopy device 1 It consists of.

The near-infrared spectrometer 1 irradiates near-infrared rays to a sample (sample) such as an agricultural product while continuously changing the wavelength, and detects transmitted light or reflected light of the sample. That is, the near-infrared spectrometer 1 includes the light source 3 and
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 detector 8 for detecting transmitted light of the sample.
And a reflected light detector 9 for detecting reflected light from the sample are arranged as shown in the figure.

When the sample cell is set at a predetermined position at the time of measurement, the sample holder 7 is transferred to the measurement position by a sample cell transfer motor (not shown in FIG. 1). Configure to go back. Next, a block diagram of the control processing system of the embodiment having such a configuration is shown in FIG.
This will be described below. Reference numeral 20 denotes a one-chip type CPU (central processing unit), which performs control processing as described later. The light source 3, the diffraction grating driving motor 5, the sample cell transport motor 22, the transmitted light detector 8, and the reflected light detector 9 are connected to the CPU 20 via an input / output interface 21. The CPU 20 has an input interface.
The input key 24 is connected via the interface 23 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 configured as described above (hereinafter, the temperature will be described in this embodiment) will be described. In this embodiment, the sample has a reference temperature To.
A calibration curve at (around 20 degrees Celsius) is obtained as follows. First, when the reference plate is set at the measurement position of the near-infrared spectrometer 1 and the near-infrared spectrometer 1 is operated, near-infrared rays emitted from the light source 3 reach the diffraction grating 6 via the reflecting mirror 4, After being split here, the light 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 as the diffraction grating 6 rotates, the reflected light detector 9 continuously detects a signal corresponding to the wavelength.
Then, after performing the operation of reading the detection signal (measurement of the reference spectrum) a predetermined number of times, the average of the spectrum is obtained.

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

Then, the absorbance is determined for a plurality of standard samples having different concentrations as described above, and a calibration curve at a reference temperature To (around 20 degrees Celsius) is determined in advance based on the measured absorbance and the known concentration. Further, for a standard sample whose measurement component is known, for example, the temperature is 3 degrees Celsius.
Calculate the absorbance spectra in the vicinity of 20 degrees Celsius, 20 degrees Celsius, and 34 degrees Celsius. Then, based on the absorbance spectrum when the temperature is 20 degrees Celsius, the deviation from the absorbance spectrum when the temperature is 3 degrees Celsius Is calculated, and the amount of deviation between the absorbance spectrum when the temperature is 34 degrees Celsius and the above reference spectrum is calculated in advance. Then, the calculated shift amounts are stored in the storage device 2.
7 is stored in advance.

Next, an example in which a component is measured by using the calibration curve and the shift 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 spectroscopy device 1 is operated, the reference spectrum Ro is measured a predetermined number of times, and the average of the reference spectrum Ro is obtained (S1 to S2).

Next, when the sample cell containing the measurement sample is set at the measurement position, the near-infrared spectrometer 1 operates again, and after measuring the spectrum R of the sample 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 measured spectrum R obtained as described above according to the following equation (1) (S9).

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

Subsequently, a temperature difference ΔT between the estimated sample temperature Ts and the reference temperature To at the time of preparing the calibration curve is calculated by the following equation (2) (S12). ΔT = Ts−To (2) Then, based on the obtained temperature difference ΔT, the measured spectrum and the spectrum at the reference temperature To when the calibration curve is prepared and the spectrum at the predetermined temperature in consideration of the external fluctuation characteristics are obtained. The shift amount is stored in the storage device 27 as described above. Therefore, the above-mentioned deviation amount △ ODt is calculated from the temperature difference ΔT as an interpolation approximation using the stored deviation amount. Next, an operation for correcting the spectrum under the reference temperature To using the obtained shift amount △ ODt 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 obtained in step S9. Subsequently, after the corrected absorbance OD 'is secondarily differentiated (S15), a calculation for estimating a predetermined moisture concentration of the sample from the second derivative absorbance using a calibration curve is performed (S16). Then, the result is displayed on the display device 26 (S17).

Next, in order to confirm the accuracy of the near-infrared analysis according to the embodiment of the present invention, the following experiment was conducted. In this test, unmilled brown rice was used as a sample, and a calibration curve for measuring the protein content of the brown rice was prepared beforehand at a sample temperature of around 20 degrees Celsius.

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

Therefore, comparing these experimental results,
If the component concentration of the sample is estimated according to the embodiment of the present invention, it is understood that the accuracy is practically sufficient. Next, an example of a quality evaluation device that displays the component concentrations of the sample obtained as described above on the display device 26 and evaluates the quality of the sample will be described.
This will be described below. In this apparatus, the sample is unmilled brown rice, and the protein content and fatty acid content in the brown rice component are measured by the above-described 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 FIG. Thereby, the protein and the fatty acid can be displayed in relation to each other on the XY coordinates, so that the display becomes very easy to understand the quality of the rice, thereby making 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 FIG.
When a measured value enters the set area, a warning sound, a warning display, or a control output is issued. As a result, quality control can be performed independently for each area set arbitrarily. 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 embodiment of the quality evaluation apparatus will be described. In this apparatus, the sample is unmilled brown rice,
Five kinds of evaluation indices such as the protein content in the brown rice component and the fatty acid content are measured by the above-described procedure. Then, as shown in FIG. 7, data relating to two evaluation indices out of the measurement results is two-dimensionally displayed on the display screen of the display device 26. Since there are five types of evaluation indices, the combinations to be displayed are shown. Is 10 ways. Therefore, as shown in FIG. 9, five types of indices “A” to “E” are displayed on the display screen of the display device, and when the operator selects two indices from these, the selected indices are displayed. The data is displayed on the XY coordinates (map), and the display can be enlarged or reduced. Further, a configuration is made such that a plurality of maps can be selected and displayed on the same screen. With such a configuration, the operability when displaying the evaluation indices in combination is improved.

FIG. 10 shows a display example in which the predetermined index is selected. As shown in FIG. 10, the fatty acid content and the like are, for example, 0 to 1 mg rather than being divided on an absolute axis of 0 to 50 mg.
Unequal divisions such as 5mg, 15-25mg,
It is preferable in terms of functionality and operability that the display section can be arbitrarily set by the operator, such as by equally dividing a section of 5 to 25 mg. Therefore, for example, when a display section is set as shown by a hatched portion in FIG.
It is configured to be converted into a display as shown in FIG.

[Brief description of the drawings]

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

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

FIG. 3 is a block diagram showing an overall configuration showing an operation example of the 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 the protein content of brown rice according to a conventional method.

FIG. 5 is a view showing another example of the relationship between the actually measured value and the estimated value of the protein content of brown rice according to the conventional method.

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

FIG. 7 is a diagram showing an example of a two-dimensional display of a result of measurement of components of a sample.

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

FIG. 9 shows a case where a sample has a plurality of evaluation indices;
FIG. 4 is an explanatory diagram for selecting two-dimensional display from one index.

FIG. 10 is a view showing a display example after a desired evaluation index is selected.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Near-infrared spectroscopy device 2 Control processing device 20 CPU 27 Storage device

Claims (1)

[Claims] An absorbance measuring means for irradiating a sample with near-infrared rays to measure the absorbance, and for a known sample, a reference absorbance for preparing a calibration curve and an absorbance at a predetermined sample temperature are measured by the absorbance measurement. Means for measuring in advance the amount of deviation between the two absorbances, a storage means for storing the calculated amount of deviation, a temperature fluctuation characteristic value measuring means for measuring the temperature of the unknown sample, and an unknown sample. About, when the absorbance is measured by the absorbance measurement means, according to the temperature fluctuation characteristic value measurement means, the measurement absorbance correction means for correcting the measured absorbance to the reference absorbance by the amount of shift stored in the storage means, correction A near-infrared spectrometer comprising: analysis means for analyzing a sample component based on the measured absorbance based on the calibration curve.