JP3142018U - Spectroscopic analyzer - Google Patents

Abstract

Disclosed is a spectroscopic analysis apparatus including a data processing unit that performs spectral spectrum peak detection with processing software that is not easily affected by noise, is easy to operate, and has a short processing time.
Since a smoothed spectrum C2 is used to detect a peak, it is difficult to be affected by noise when detecting the peak. In the spectrum subjected to strong smoothing, the absorbance at the peak or base position may be different from that of the original spectrum C1, but in the present invention, the absorbance is obtained from the spectrum C1, so no problem occurs. Smoothing and maximum / minimum detection are simple algorithms that are easier to operate and shorter in computation time than curve fitting.
[Selection] Figure 1

Description

  The present invention relates to an infrared spectrophotometer, an ultraviolet / visible spectrophotometer, and the like, and more particularly to a peak detection algorithm for quantitative calculation in a spectral spectrum.

  Conventionally, for example, a maximum wavelength in which a spectral spectrum of a specific wavelength region measured shows a maximum value and a minimum wavelength that shows a minimum value are detected, and the difference between the detected maximum wavelength and the spectral spectrum value at the minimum wavelength becomes a threshold value. If it exceeds, it is considered a peak. In the case of this example, the wavelength showing the maximum value or the minimum value tends to deviate from the true value due to noise included in the spectrum, and the wavelength accuracy of the maximum wavelength and the minimum wavelength is deteriorated.

  Alternatively, a curve that detects the peak position by approximating the shape of the spectral spectrum with a Gaussian curve or other curve, and determining the one that reproduces the original spectral spectrum while gradually changing the shape and position, and determining the peak position There is a fitting method. In this case, it is difficult to be affected by noise, but it is difficult to operate by setting an approximate curve or the like, and the processing time is long.

On the other hand, in the chromatogram, although the horizontal axis is the time unlike the wavelength of the spectral spectrum, many methods for detecting the peak are provided. For example, a point of interest is set on the chromatogram data, and after that point, the data in a certain interval is calculated as to whether it is rising or falling with respect to the point of interest. If the point of interest is moved, and if it is descending, the peak point is extracted by capturing the inflection point of the peak by moving the point of interest to the minimum value in the section (see, for example, Patent Document 1).
JP-A-6-201673

  Provided is a spectroscopic analysis apparatus including a data processing unit that performs spectral spectrum peak detection and base detection with processing software that is not easily affected by noise, is easy to operate, and has a short processing time.

  The present invention provides a spectroscopic analysis apparatus having a mechanism for measuring a spectroscopic spectrum of a sample and a data processing unit that detects a peak and a base of the spectroscopic spectrum and measures a concentration of a substance in the sample. A smoothing means for smoothing (hereinafter referred to as smoothing), a peak base wavelength detecting means for detecting a peak wavelength at which the smoothed spectral spectrum shows a peak and a base wavelength at which the base is shown, and a spectral spectrum before being smoothed. The data processing unit measures the concentration of the substance in the sample from the value at the peak wavelength and the value at the base wavelength.

  Alternatively, smoothing means for smoothing the measured spectral spectrum, and base wavelength detection means for detecting two base wavelengths indicating bases on both sides of the peak of the smoothed spectral spectrum, and smoothing at the two base wavelengths. A data processing unit that measures the concentration of the substance in the sample from the area of the spectral spectrum above the straight line connecting the two coordinates indicated by the spectral spectrum values before the measurement. Therefore, the influence of noise is small in the detection and quantitative calculation of the peak wavelength and the base wavelength.

  It is possible to provide a spectroscopic analyzer including a data processing unit that performs peak calculation and base detection of a spectroscopic spectrum with processing software that is easy to operate, has a short processing time, and is not easily affected by noise.

  The spectrum spectrum is smoothed by applying the Savitzky-Golay method that can estimate the peak position and height even when the peak is sampled at only a few points, or when the maximum value falls between two peaks. .

  An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing an outline of the operation of a spectroscopic analyzer according to an embodiment of the present invention. FIG. 2 is an example of the smoothing of the spectrum C1 according to the embodiment of the present invention. FIG. 3 is a diagram showing a schematic structure of a spectroscopic analyzer according to an embodiment of the present invention.

  As shown in FIG. 3, a spectroscopic analyzer according to an embodiment of the present invention includes a light source unit 4 that emits light, a spectroscope 5 that splits the light, and a photoelectric that converts the split light into a photocurrent after passing through the sample. A converter 6; an amplifier 7 for converting the photocurrent into a voltage signal; a data processing unit 1 for data processing of the voltage signal; a controller 3 for controlling the light source unit 4 and the spectroscope 5; The display unit 2 has a structure that displays data, alarms, operation screens, and the like in accordance with signals from the control unit 3.

  The light source unit 4 has a structure including a WI lamp, a D2 lamp, and a lamp switching mirror. The controller 3 drives the lamp switching mirror and controls the light source unit 4 so that the light of the WI lamp is incident on the spectroscope 5 when measuring in the visible light region and the light of the D2 lamp is incident on the ultraviolet light region. Control.

  The spectral spectrum C1 shown in FIG. 2 is obtained by measuring the wavelength of the light emitted from the spectroscope 5 by placing the sample between the spectroscope 5 and the photoelectric converter 6 shown in FIG. Where the horizontal axis represents wavelength and the vertical axis represents absorbance in the examples. The absorbance at a specific wavelength determined by the substance is proportional to the concentration of the substance in the sample.

  The function of the spectral analyzer according to the embodiment of the present invention for detecting a spectrum peak will be described with reference to the flowchart shown in FIG. First, the original spectral spectrum C1 measured in the first step S (hereinafter referred to as “S”) 1 is read onto the processing software stored in the data processing unit 1 (FIG. 3) (S1). Next, the spectral spectrum C1 is subjected to a smoothing process using the Savitzky-Golay method. For example, about several tens of smoothing points are selected and calculated. The obtained smoothed spectrum is the spectrum C2 (S2). The spectrum C2 is stored in the data processing unit 1 (FIG. 3) (S3).

  The maximum / minimum of the spectral spectrum C2 that has been smoothed in the designated wavelength range used for quantitative calculation is detected. In the embodiment, there are two local maximums and local minimums as shown in FIG. 2 (S4). The maximum and minimum wavelengths are recorded (S5). The maximum closest to the designated wavelength used for quantitative calculation is regarded as a peak, and the wavelength is recorded as the peak wavelength W2 (S6). The adjacent minimum is regarded as the base, and the wavelengths are recorded as base wavelengths W1 and W3 (S7). Absorbances corresponding to the obtained peak wavelength W2 and base wavelengths W1 and W3 are read on the original spectral spectrum C1. The obtained absorbances are defined as peak absorbance A2, base absorbance A1, and A3, respectively (S8).

  Quantitative calculation is executed based on the obtained peak wavelength W2, base wavelengths W1 and W3, peak absorbance A2, and base absorbance A1 and A3. There are many types of quantitative calculations. For example, a method using only the peak absorbance A2, or a method using the peak absorbance A2 minus the base absorbance A1 or the base absorbance A3, two coordinates (base wavelength W1, base absorbance A1), (base wavelength W3 There is a method of calculating and using the upper peak area from the base line connecting the base absorbance A3). In any method, the concentration is converted into a concentration by a calibration curve obtained by measuring a sample having a known concentration (S9).

  Since the present invention has the above-described structure, the spectral spectrum C2 that has been smoothed is used to detect the peak. Therefore, the peak is not easily affected by noise. In the spectrum subjected to strong smoothing, the absorbance at the peak or base position may be different from that of the original spectrum C1, but in the present invention, the absorbance is obtained from the spectrum C1, so no problem occurs. Smoothing and maximum / minimum detection are simple algorithms that are easier to operate and shorter in computation time than curve fitting.

  In the illustrated example, the spectroscopic analyzer according to the embodiment has a structure of, for example, an ultraviolet / visible spectrophotometer, but instead has a structure of, for example, a Fourier transform infrared spectrophotometer or a spectrofluorophotometer. However, the present invention is applicable. Moreover, although the vertical axis | shaft of the spectral spectra C1 and C2 is shown by the light absorbency, this invention is applicable also when it shows by the intensity | strength of light instead. Thus, the present invention is not limited to the illustrated examples, but includes various modifications.

  The present invention relates to an infrared spectrophotometer, an ultraviolet / visible spectrophotometer, and the like, and more particularly to a peak detection algorithm for quantitative calculation in a spectral spectrum.

It is a figure which shows the outline | summary of operation | movement of the spectroscopic analyzer by the Example of this invention. It is an example of the smoothing of the spectrum by the Example of this invention. It is a figure which shows schematic structure of the spectroscopic analyzer by the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Data processing part 2 Display 3 Controller 4 Light source part 5 Spectrometer 6 Photoelectric converter 7 Amplifier A1 Base absorbance A2 Peak absorbance A3 Base absorbance C1 Spectrum C2 Spectrum spectrum W1 Base wavelength W2 Peak wavelength W3 Base wavelength

Claims (2)

  In a spectroscopic analyzer equipped with a mechanism for measuring a spectroscopic spectrum of a sample and a data processing unit for detecting the peak and base of the spectroscopic spectrum and measuring the concentration of a substance in the sample, the measured spectroscopic spectrum is smoothed. A value at the peak wavelength of the spectrum before smoothing, comprising: a smoothing means; and a peak-base wavelength detection means for detecting a peak wavelength at which the smoothed spectral spectrum shows a peak and a base wavelength at which the base is shown. And a data processing unit for measuring the concentration of the substance in the sample from the value at the base wavelength. In a spectroscopic analyzer equipped with a mechanism for measuring a spectroscopic spectrum of a sample and a data processing unit for detecting the peak and base of the spectroscopic spectrum and measuring the concentration of a substance in the sample, the measured spectroscopic spectrum is smoothed. Smoothing means and base wavelength detecting means for detecting two base wavelengths indicating bases on both sides of the peak of the smoothed spectrum spectrum, and the spectrum spectrum before smoothing at the two base wavelengths. A spectroscopic analyzer comprising a data processing unit for measuring a concentration of a substance in a sample from an area of the spectroscopic spectrum above a straight line connecting two coordinates indicated by values.

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