JP3128163U - Spectrophotometer - Google Patents

Abstract

In a spectrophotometer, when a specific wavelength is selected and a measured value at that wavelength is used for evaluation, the measured value includes an error due to a shift in wavelength. When selecting a wavelength, it is easy to take into account variations in measured values resulting from such a shift in wavelength.
[Solution]
It has a function to determine the ambiguity of the measurement value derived from the wavelength shift. Based on the spectrum used for evaluation and the wavelength shift, the degree of ambiguity derived from the wavelength shift in the measured value is calculated depending on the selected wavelength. Displays the ambiguity for each wavelength. Further, when a wavelength with a large ambiguity is selected, a warning may be issued.
[Selection] Figure 1

Description

The present invention relates to a spectrophotometer used as a general-purpose spectrophotometer or a detector of a high-performance liquid chromatograph, and in particular, measures an absorption spectrum of a sample, or absorbs or transmits a sample at a certain wavelength. It is related with the spectrophotometer which can obtain | require a rate.

The spectrophotometer performs wavelength separation of light of various wavelengths from a light source, such as ultraviolet, visible, and near-infrared light, using a spectroscopic means, and irradiates the sample to be measured for each wavelength of light that reaches the detector. It is a device that measures the intensity, measures the absorption spectrum peculiar to the sample, and measures the transmittance / reflectance and absorbance of each absorbed wavelength, and is used for qualitative and quantitative analysis of sample components. Such a spectrophotometer can measure a wide variety of samples such as liquids and solids, and the eluate from the liquid chromatograph is also measured by the spectrophotometer.

In the spectrophotometer, for example, as shown in FIG. 2 of Patent Document 1, the light from the light source is divided into two light beams, and the two beams of the sample side light beam and the reference side light beam are passed through. There are a photometer and a single beam type spectrophotometer in which a light beam from a light source is introduced into a detector through a measuring unit as shown in FIG. In addition, as a spectroscopic unit that splits light from a light source, a single monochromator having a spectroscope (such as a diffraction grating) or two spectroscopes as shown in FIG. There is a double monochromator.

In a spectrophotometer, the sample can be qualitatively and quantitatively measured by irradiating the sample with light from a light source and measuring the transmittance and reflectance. At that time, one or a plurality of specific wavelengths may be selected, and qualitative or quantitative may be performed based on a measurement value for the specific wavelength. Specifically, for quality control of glass, film, plastic, etc. and product confirmation, judge whether the quality is good or bad depending on whether the measured value at a specific wavelength is in a predetermined range. There is.

JP 2002-156282 A JP 2005-24403 A

When a spectrophotometer measures a sample with light of a specific wavelength and uses the measured value for evaluation, the error included in the measured value may increase depending on the type of sample to be measured and how the wavelength is selected. . There are various causes for the error in the measurement value. One of the causes is that the set wavelength and the actually measured wavelength are deviated. For example, in a general UV-visible spectrophotometer, the wavelength deviation includes about ± 0.3 nm as the wavelength accuracy and about ± 0.3 nm as the repeatability. If there is, it is said that there is a variation in wavelength of ± 0.5 nm. Therefore, when a specific wavelength is selected and the measurement value at that wavelength is used for evaluation, the measurement value includes an error due to a wavelength shift. Variations in measured values due to wavelength shift were not considered.

The error due to wavelength shift included in the measurement value at a specific wavelength varies depending on the combination of the sample type and the selected wavelength. Depending on the sample spectrum and the selected wavelength, the measurement value may vary. May grow. In particular, when the sample is evaluated using the measured value at the selected wavelength, the selection of the wavelength greatly affects the content of the evaluation.

Therefore, the present invention solves the above-mentioned problems, and can easily grasp how much the measured value varies depending on the selected wavelength before selecting the wavelength. An object of the present invention is to provide a spectrophotometer that can increase the accuracy of evaluation by selecting a wavelength.

A spectrophotometer according to a first device for solving the above problems is a spectrophotometer for evaluating a measurement sample based on a measurement value at a selected wavelength, and includes a spectrum of the measurement sample and A control unit is provided that obtains and stores the ambiguity of the measurement value derived from the wavelength shift at each wavelength from the value of the wavelength shift. According to the present invention, it is possible to quantitatively grasp the ambiguity included in the measurement value at the selected wavelength. Further, when selecting a wavelength, it is possible to grasp the risk of erroneous evaluation due to the ambiguity of the measurement value derived from the wavelength shift.

The spectrophotometer according to the second device, which has been made in order to solve the above-mentioned problems, is characterized by further comprising a display unit for displaying the ambiguity of the measurement value derived from the wavelength shift at each wavelength. . According to the present invention, it is possible to visually grasp the ambiguity of the measurement value.

In the spectrophotometer according to the third aspect of the invention for solving the above-mentioned problem, the control unit further issues a warning when the ambiguity of the measured value exceeds the threshold at the selected wavelength. It is characterized by being. Further, according to the present invention, it is possible to easily know that an unfavorable wavelength is selected as a measurement wavelength because the measurement value is vague.

According to the present invention, when a certain sample is evaluated based on a measurement value at a specific wavelength, it is possible to easily grasp how much variation in the measurement value can be caused by the selected wavelength. Furthermore, the accuracy of evaluation can be improved by selecting a wavelength with small variation.

The spectrophotometer according to the present invention will be schematically described with reference to FIG. The present embodiment is an example applied to a double beam type spectrophotometer.

In the photometry unit 1, the light emitted from the light source 2 enters the spectroscope 3, where monochromatic light having a desired wavelength is extracted. This monochromatic light is sent to the sector mirror 5 by the reflecting mirror 4 and is divided by the sector mirror 5 into two light beams of the sample side light beam S and the reference side light beam R. Further, the sector mirror 5 is provided with a light shielding portion so that a light shielding period occurs alternately with the generation period of the sample side light beam S and the reference side light beam R. The sample-side light beam S is irradiated onto the measurement sample 8 through the reflecting mirror 6, and the light that has passed through the measurement sample 8 is sent to the light receiving surface of the photodetector 13 through the reflecting mirrors 10 and 12. On the other hand, the control side light beam R is irradiated to the control sample 9 through the reflecting mirror 7, and the light that has passed through the control sample 9 is sent to the light receiving surface of the photodetector 13 through the reflecting mirror 11.

The output signal of the photodetector 13 is amplified by an amplifier 14 and then sampled by a sample-and-hold (S / H) circuit 15 at a constant time interval, and the held voltage is converted by an analog-digital (A / D) converter 16. Converted to a digital voltage value. The control unit 17 controls the operation of the photometric unit 1 and has a function of performing various calculations for calculating, for example, absorbance and transmittance from the photometric value data, and includes a memory 18. An operation unit 19 connected to the control unit 17 is used for setting various parameters related to measurement, and instructing various measurements and processes. Furthermore, the display unit 20 displays auxiliary information for operation, measurement results, and the like on a screen, and includes a display unit 21 and a warning unit 21 based on a table. Note that the control unit 17 can realize its function by, for example, a personal computer.

A characteristic function of the spectrophotometer of the present invention will be described with reference to the flowchart of FIG.

First, a wavelength shift is input (S1). Next, a wavelength range is selected, and the spectrum of the sample is measured within that range (S2). Next, the control unit 18 obtains the ambiguity of the measurement value derived from the wavelength shift for each wavelength from the wavelength shift input in S1 and the spectrum measured in S2 based on an algorithm described later (S3). . Next, the ambiguity obtained in S3 is displayed as a table (S4).

The wavelength shift selection method in S1 may be performed by the user selecting a wavelength shift and inputting it from the operation unit 19, or by referring to the device standard or the like, a value determined in advance by the device as a fixed value. 17 may be stored and used. Further, for example, different wavelength shifts may be set depending on the wavelength range.

An example of the spectrum measured in S2 is shown in FIG. This is an example in which measurement is performed by the photometry unit 1 over a wavelength range of 200 nm to 900 nm, and is displayed on the display unit 20, for example. The selection of this wavelength range needs to be set to a range including a specific wavelength used for evaluation.

In S3, for example, the control unit 17 calculates the ambiguity using the following algorithm. At each measurement point, a straight line L is obtained by the least square method using data in an appropriate range, an ambiguity is obtained from the shift in wavelength input by the straight lines L and S1, and stored in the memory 18. As a method of obtaining the straight line L, for example, a differential value at the measurement wavelength may be obtained, and the differential value may be obtained as a slope and obtained as a straight line passing through the measurement point.

An example of obtaining the ambiguity using the straight line L will be described with reference to FIG. For example, the measurement wavelength is 400 nm, and the value of the wavelength shift set in S1 is ± 0.4 nm. The wavelength wave maximum value Wmax (400.4 nm) and the wavelength minimum value Wmin (399.6 nm) are obtained from the measurement wavelength and the wavelength shift. Next, from the values of Wmax and Wmin and the straight line L, the maximum transmittance value Tmax and the minimum transmittance value Tmin that can be taken on the straight line L are obtained. At this time, the difference between Tmax and Tmin is obtained, and the value is defined as ambiguity at the measurement wavelength.

In S4, as shown in FIG. 4, the ambiguity at each wavelength is displayed in the form of a table and displayed on the display unit 21 according to the table of the display unit 20. In the display unit 21, it may be displayed in a graph format. This makes it easier to consider the ambiguity for each wavelength when the measurer selects the wavelength to be measured. Further, when a threshold value is provided for ambiguity and a wavelength exceeding the threshold value is selected as a wavelength to be measured, a warning may be displayed by the warning unit 22 or a warning sound may be sounded.

It is a flowchart figure which shows the characteristic control action in this invention. It is an example of the spectrum measured with the spectrophotometer which concerns on this invention. It is an example of how to obtain ambiguity due to wavelength shift in the present invention. It is an example which displays the ambiguity in this invention in a tabular form. It is an example of the spectrophotometer which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Photometry part 2 ... Light source 3 ... Spectrometer 8 ... Sample cell 9 ... Control cell 13 ... Photodetector 17 ... Control part 18 ... Memory 19 .. Operation unit 20 ... Display unit 21 ... Display unit 22 according to table ... Warning unit R ... Control side beam S ... Sample side beam

Claims (3)

A spectrophotometer for evaluating a measurement sample based on a measurement value at a selected wavelength, and obtaining the ambiguity of the measurement value derived from the wavelength shift at each wavelength from the spectrum of the measurement sample and the value of the wavelength shift. A spectrophotometer comprising a control unit and a memory for storing the ambiguity. 2. The spectrophotometer according to claim 1, further comprising a display unit for displaying ambiguity of a measurement value derived from a wavelength shift at each wavelength. 3. The spectrophotometer according to claim 1, wherein the control unit further includes a warning unit that issues a warning when the ambiguity of the measurement value at the selected wavelength exceeds a threshold value. Spectrophotometer.

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