CN113281337B - A kind of extraction method of complex compound Raman spectrum - Google Patents

Abstract

An extraction method of a complex compound Raman spectrum relates to the fields of analytical chemistry and pharmaceutical ingredients. The method is an extraction method of the complex compound high-quality Raman spectrum based on the combination of the optical microscopic imaging technology with high spatial resolution and the Raman spectrum technology. The method is simple to operate, is non-contact and harmless, can be used for products, only needs trace substances to be carried out under the irradiation of light waves, can be applied to analysis of complex compounds, and does not change the physical and chemical properties of the complex compounds to be detected.

Description

A kind of extraction method of complex compound Raman spectrum

technical field

The invention relates to the field of analytical chemistry and the field of pharmaceutical ingredients, in particular to a method for extracting high-quality Raman spectra of complex compounds based on optical microscopic imaging combined with Raman spectra.

Background technique

High-molecular-weight complex compounds produced by cross-linking and polymerization reactions are widely used in the beverage and pharmaceutical industries. However, the composition of this compound is complex, including simple initial substances, intermediate products, and final products, and the intermediate products generated by crosslinking and polymerization reactions are crosslinked products with a molecular weight in a certain range, so it is difficult to analyze single crystals of this substance , especially without changing its physical and chemical properties, such as being insoluble in water, not heating and cooling, and not using color-changing reactions, then optical detection is a technical means.

In view of the important role of cross-linked compounds in the beverage and pharmaceutical industries, it is urgent to establish a rapid, non-contact detection method that retains the chemical and physical properties of complex compounds. The existing detection methods use thermal melting point method and high-resolution mass spectrometry Destruction of physical properties; indistinguishable by nuclear magnetic resonance techniques. In recent years, high-spatial-resolution optical microscopy imaging technology has developed rapidly, providing feasibility for spatially resolving single crystals in complex compounds; at the same time, Raman spectroscopy has the role of molecular labels, making it possible to identify the components of complex compounds. However, the identification of complex compound components by Raman spectroscopy requires high-quality Raman spectroscopy. In view of this, the present invention establishes a non-contact, non-damaging high-quality Raman spectrum extraction method for complex compounds based on the combination of optical microscopic imaging technology with high spatial resolution and Raman spectroscopy technology.

Contents of the invention

The purpose of the present invention is to provide a method for extracting high-quality Raman spectra of complex compounds based on the combination of optical microscopic imaging technology with high spatial resolution and Raman spectroscopy technology. The method is simple, non-contact, non-destructive, and can be carried out on products. It only needs a small amount of substances to be carried out under the irradiation of light waves, and can be applied to the analysis of complex compounds without changing the physical and chemical properties of the complex compounds to be tested.

In order to achieve the above object, the present invention provides a method for extracting a high-quality Raman spectrum of a compound based on the combination of high spatial resolution optical microscopic imaging technology and Raman spectrum technology, comprising the following steps:

(1) Take 1-5mg of the powder sample to be tested, place it on a glass slide, expose a diameter of 3-5mm, or a 3-5mm rectangle, or compact a 3-5mm rectangle surface into a thin layer, and make it to be tested sample;

(2) Observe the sample to be tested under an optical microscope, look for a dispersed particle with a clear image and a wide range of morphological characteristics, perform bright-field imaging on the dispersed particle, and select the highest gray level on the particle in the imaging image that represents the brightness One point proceeds as a point of interest;

(3) Perform light irradiation of a specific wavelength on the corresponding position of the point of interest in step (2) on the particle, and measure the Raman spectrum of the excitation wavelength at the corresponding position on the particle. The Raman spectrum contains two parameters k and I, k is the Raman shift wavenumber in the Raman spectrum, and I is the spectral intensity corresponding to the wavenumber k in the Raman spectrum;

(4) Repeat step (3) multiple times to obtain the Raman spectrum of the excitation wavelength on multiple corresponding positions, and then average the spectral intensity I corresponding to the same wave number k in multiple Raman spectra to obtain the average Raman spectrum ;

(5) In the average Raman spectrum calculated in step (4), find the Raman spectrum characteristic peak with high peak and sharp peak shape as the Raman spectrum characteristic peak of the analyte, and record the wave number corresponding to the Raman spectrum characteristic peak k ₀ ;

(6) Observe the sample to be tested again under the optical microscope to find a dispersed particle with clear imaging and extensive morphology features, or directly use the particle found in step (2) to perform bright field imaging on the particle, which will contain A rectangular area of the whole or part of the particle is used as the area of interest;

(7) Carry out confocal scanning to step (6) region of interest corresponding to the area on the sample to obtain a Raman spectrum data set, the Raman spectrum data set contains four parameters, are respectively x, y, k and I, wherein x and y corresponds to the plane coordinates of a point in the region of interest, k is the Raman shift wavenumber of the Raman spectrum measured at a point, and I is the spectral intensity corresponding to a wavenumber k in the Raman spectrum of a point;

(8) each point Raman spectrum of the Raman spectrum data set obtained in step (7) is processed to remove cosmic noise and eliminate background noise, and obtain the processed Raman spectrum data set;

(9) In the Raman spectrum data set after step (8) processing, the Raman image of the Raman characteristic peak is generated as the gray value of the point in the plane image at the wavenumber _k of each point of the Raman spectrum corresponding to the spectral intensity I ;

(10) in the Raman image that step (9) obtains, select the highest point of the gray value as the point of interest;

(11) According to the position of the point of interest obtained in step (10) in the sample, perform region-specific extraction of a high-quality Raman spectrum at the corresponding position in the Raman spectrum data set processed in step (8).

The powder sample to be tested in the present invention is a single compound or a polymer with multiple components.

In the first implementation of the present invention, the powder sample to be tested is a polyvinylpyrrolidone (PVP) K25 powder sample purchased from the German company BASF, batch number 61861347G0.

In the first implementation of the present invention, a confocal Raman spectroscopy microscope WITec Alpha300-RAMAN is used for optical microscope observation of sample particles, bright field image acquisition, Raman spectroscopy measurement and confocal scanning. Use WITecProject FIVE software to display bright field images, Raman spectra, Raman images, regions of interest, and points of interest, and perform data processing on Raman spectra and Raman spectral datasets, and extract data from Raman spectral datasets High quality Raman spectroscopy.

In Embodiment 1 of the present invention, in step (1), take 2-5 mg of PVP powder sample and place it on a glass slide, shake it slightly to disperse the sample powder particles as much as possible, cover the cover glass and then slightly roll the cover glass , to further disperse the sample powder particles.

In the first embodiment of the present invention, in step (2), a 50 times objective lens is used to observe the sample with a bright-field microscope to select sample particles for Raman scanning.

In the first embodiment of the present invention, in step (2), it was observed that the shape of the particles in the PVP sample was irregular. According to the observation results, an irregularly shaped particle was selected in the PVP sample for imaging, and the imaging image was selected by visual observation. The point with the highest gray level on the middle particle is taken as the point of interest.

In Embodiment 1 of the present invention, in step (3), a confocal Raman spectrum microscope WITec Alpha300-RAMAN is used for Raman spectrum measurement, and the measurement uses an excitation wavelength of 532nm, a laser power of 10mw, and a grating of 1200g/mm. The objective lens is 50 times, the numerical aperture is 0.75, and the wavenumber range is 0-1900cm ^-1 .

In Embodiment 1 of the present invention, in step (4), the Raman spectrum is measured 10 times on the position on the PVP sample particle using a confocal Raman spectrum microscope, and the average Raman spectrum is calculated to obtain the average Raman spectrum.

In the first embodiment of the present invention, in step (5), the recorded characteristic peak of the Raman spectrum corresponds to a wave number k of 934.2 cm ⁻¹ .

In the first embodiment of the present invention, in step (6), the region of interest obtained is a square region of 20 μm*20 μm including the local PVP particles found in step (2).

In the first embodiment of the present invention, in step (7), a confocal Raman spectrum microscope WITec Alpha300-RAMAN is used for confocal scanning, the scanning adopts an excitation wavelength of 532nm, a laser power of 10mw, a grating of 1200g/mm, and an objective lens The multiple is 50, the numerical aperture is 0.75 and the wave number is 0-1900 cm ^-1 .

In the second embodiment of the present invention, the powder sample to be tested is cross-linked polyvinylpyrrolidone (PVPP) powder purchased from the German company BASF as the sample, batch number 92441577L0.

In the second embodiment of the present invention, a confocal Raman spectroscopy microscope WITec Alpha300-RAMAN is used for optical microscope observation of sample particles, bright field image acquisition, Raman spectroscopy measurement and confocal scanning. Use WITecProject FIVE software to display bright field images, Raman spectra, Raman images, regions of interest, and points of interest, and perform data processing on Raman spectra and Raman spectral datasets, and extract data from Raman spectral datasets High quality Raman spectroscopy.

In the second embodiment of the present invention, in step (1), take 2-5 mg of the PVPP powder sample and place it on a glass slide, shake it slightly to disperse the sample powder particles as much as possible, cover the cover glass and then slightly roll the cover glass , to further disperse the sample powder particles.

In the second embodiment of the present invention, in step (2), a bright field microscope with a 50 times objective lens is used to observe the sample and select sample particles for Raman scanning.

In the second embodiment of the present invention, in step (2), it is observed that most of the particles in the PVPP sample are spherical particles, and a very small part is a very small irregular particle. According to the observation results, one of the PVPP samples is selected. Spherical particles are imaged, and the point with the highest gray level on the particle in the imaging image is selected as the point of interest by visual observation.

In the second embodiment of the present invention, in step (3), a confocal Raman spectrum microscope WITec Alpha300-RAMAN is used for Raman spectrum measurement, and the measurement adopts an excitation wavelength of 532nm, a laser power of 10mw, and a grating of 1200g/mm. The objective lens is 50 times, the numerical aperture is 0.75, and the wavenumber range is 0-1900cm ^-1 .

In the second embodiment of the present invention, in step (4), a confocal Raman spectrum microscope is used to perform 10 Raman spectrum measurements on the position on the PVPP sample particle and perform average calculation to obtain an average Raman spectrum.

In the second embodiment of the present invention, in step (5), the recorded characteristic peak of the Raman spectrum corresponds to a wave number k of 934.2 cm ⁻¹ .

In the second embodiment of the present invention, in step (6), the region of interest obtained is a square region of 10 μm*10 μm including the part of another PVPP sample particle found.

In the second embodiment of the present invention, in step (7), a confocal Raman spectrum microscope WITec Alpha300-RAMAN is used for confocal scanning, the scanning adopts an excitation wavelength of 532nm, a laser power of 10mw, a grating of 1200g/mm, and an objective lens The magnification is 50, the numerical aperture is 0.75, and the wave number is 0 to 1900 cm ⁻¹ .

Compared with prior art, the beneficial effect of the present invention is:

The method provided by the present invention establishes a high-quality Raman spectrum extraction method for chemical and pharmaceutical components with an analysis method based on optical microscopic imaging combined with Raman spectrum for complex compounds. Optical microscopic imaging of compound particles, identifying the particles in the image according to the obtained image; irradiating the image particle area with light of a specific wavelength to obtain a Raman spectrum; analyzing the Raman characteristic peaks and making a Raman image of the Raman characteristic peaks; Based on the Raman image, perform region-specific extraction of high-quality Raman spectra. The method is accurate, non-contact, non-damaging, fast, and does not change the physical and chemical properties of the substance to be measured, and can be used for Raman spectroscopic analysis of the components of different chemical substances.

The method of the invention directly combines the high-resolution imaging of the compound with Raman spectroscopy, without contact and without changing the physical and chemical properties of the compound.

Description of drawings

Figure 1 PVP K25 powder sample temporary loading;

Among Fig. 2 (a) is the bright-field image of the PVP sample particle, and the crosshair mark position is the point of interest; (b) is the Raman spectrum of the PVP sample after the average calculation;

Among Fig. 3 (a) is the bright-field image of the irregular particle in the PVP sample, (b) is the Raman image of the Raman characteristic peak of the irregular particle in the PVP sample;

In Fig. 4 (a) Raman image of Raman characteristic peaks of irregular particles in PVP samples, where points of interest are marked with crosshairs; (b) high-quality Raman spectra extracted from the Raman spectrum dataset of PVP sample particles.

Figure 5 Temporary loading of powder samples;

Among Fig. 6 (a) is the bright-field image of PVPP particles, and the position marked by the crosshair is the point of interest; (b) is the Raman spectrum of the PVPP sample after average calculation;

Among Fig. 7 (a) is the bright-field image of the spherical particle in the PVPP sample, wherein the region in the solid line frame is the region of interest that contains the local particle; (b) is the Raman image of the Raman characteristic peak of the spherical particle in the PVPP sample;

Figure 8 (a) is the Raman image of the Raman characteristic peaks of the particles in the PVPP sample, where the points of interest are marked with cross lines; (b) is the high-quality Raman spectrum extracted from the Raman spectrum data set of the PVPP sample particles.

Detailed ways

The present invention will be further described below in conjunction with the examples, but the present invention is not limited to the following examples.

Example 1:

A PVP K25 powder sample purchased from the German company BASF, lot number 61861347G0 was used. Confocal Raman spectroscopy microscope WITec Alpha300-RAMAN was used for optical microscope observation of sample particles, bright field image acquisition, Raman spectroscopy measurement and confocal scanning. Use WITec Project FIVE software to display bright field images, Raman spectra, Raman images, regions of interest, and points of interest, and perform data processing on Raman spectra and Raman spectral datasets, and in Raman spectral datasets Extract high-quality Raman spectra.

The PVP powder sample was made into a temporary loading sheet, as shown in Figure 1.

The prepared temporary mount was placed on the sample stage of a confocal Raman microscope for imaging, and the particles in the PVP sample were observed through a 50x objective lens. It was observed that the particle shapes in the PVP samples were all irregular particles. According to the observation results, an irregular-shaped particle was selected in the PVP sample for bright-field imaging, and the point with the highest gray level on the particle in the bright-field imaging image was selected as the point of interest through visual observation. The bright-field imaging images of PVP sample particles are shown in (a) in Figure 2, and the points of interest in the images are marked by cross lines. Light irradiation of a specific excitation wavelength is carried out on the position corresponding to the obtained point of interest on the particle, and the Raman spectrum of the single crystal at this excitation wavelength is measured. The measurement adopts an excitation wavelength of 532nm, a laser power of 10mw, and a grating of 1200g/mm, objective lens 50 times, numerical aperture 0.75 and wave number range 0-1900cm ^-1 . After performing 10 Raman spectrum measurements on the positions of the particles corresponding to the points of interest in the bright field image of the PVP sample particles, the average Raman spectrum of the obtained 10 Raman spectra was calculated to obtain the average Raman spectrum as the Raman spectrum of the PVP sample. , the Raman spectrum of the PVP sample is shown in Figure 2 (b). Observe that the Raman spectrum signal of the PVP sample in (b) in Figure 2 has a sharp Raman characteristic peak at the position k=934.2cm ^-1 (this is denoted as k ₀ ).

Subsequently, the irregular particles found in step (2) of the PVP sample were again subjected to bright-field imaging. The bright-field image is shown in Figure 3 (a), and the area in the solid line frame in Figure 3 (a) contains particles Local ROI, the ROI size is 20μm*20μm. Confocal scanning was performed on the area corresponding to the sample in the region of interest, and the Raman spectrum data sets of the PVP sample particles were obtained respectively. For scanning, the excitation wavelength is 532nm, the laser power is 10mw, the grating is 1200g/mm, the objective lens multiple is 50, the numerical aperture is 0.75, and the wave number is 0-1900cm ^-1 . The Raman spectrum of each point of the obtained Raman spectrum data set is processed to remove cosmic noise and background noise, and the processed Raman spectrum data set of PVP sample particles is obtained. Subsequently, in the processed Raman spectrum data set, the spectral intensity I of each point of the Raman spectrum at the wave number k ₀ =934.2 cm ^-1 is used as the gray value of the point in the plane image to generate a Raman image of the Raman characteristic peak, The Raman image of the Raman characteristic peaks of the PVP sample particles is shown in Figure 3 (b).

In the obtained Raman image of the Raman characteristic peak of the PVP sample particles, select the point with the highest gray value as the point of interest, as shown in (a) in Figure 4, and the point of interest is marked with a cross. According to the position in the sample corresponding to the point of interest, a high-quality Raman spectrum is extracted in the processed PVP sample particle Raman spectrum data set, and the extracted high-quality Raman spectrum is shown in Figure 4 (b) .

Example 2:

As a sample, PVPP powder purchased from the German company BASF, lot number 92441577L0 was used. The scheme uses confocal Raman spectroscopy microscope WITec Alpha300-RAMAN for optical microscope observation of sample particles, bright field image acquisition, Raman spectroscopy measurement and confocal scanning. Use WITec Project FIVE software to display bright field images, Raman spectra, Raman images, regions of interest, and points of interest, and perform data processing on Raman spectra and Raman spectral datasets, and in Raman spectral datasets Extract high-quality Raman spectra.

The PVPP powder samples were made into temporary mounts, as shown in Figure 5.

The prepared temporary mount was placed on the sample stage of a confocal Raman microscope for imaging, and the particles in the PVPP sample were observed through a 50x objective lens. It was observed that most of the particles in the PVPP sample were spherical particles, and a very small part was small irregular particles. According to the observation results, select an irregular particle in the PVP sample for bright field imaging, select a spherical particle in the PVPP sample for bright field imaging, and select the particle with the highest gray level in the bright field imaging image by visual observation A point of is performed as a point of interest. The bright-field imaging image of PVPP sample particles is shown in Fig. 6(a), and the point of interest in the image is the position marked by the crosshair. Light irradiation of a specific excitation wavelength is carried out on the position corresponding to the obtained point of interest on the particle, and the Raman spectrum of the single crystal at this excitation wavelength is measured. The measurement adopts an excitation wavelength of 532nm, a laser power of 10mw, and a grating of 1200g/mm, objective lens 50 times, numerical aperture 0.75 and wave number range 0-1900cm ^-1 . After performing 10 Raman spectrum measurements on the positions of the particles corresponding to the points of interest in the bright field image of the PVPP sample particles, the average Raman spectrum of the obtained 10 Raman spectra was calculated to obtain the average Raman spectrum as the Raman spectrum of the PVPP sample. , Raman spectrum of the PVPP sample is shown in Figure 6(b). Observe that there is a sharp Raman characteristic peak near the position of k=934.2cm ^-1 (denoted as k ₀ ) in the Raman spectrum signal of the PVPP sample in (b).

Subsequently, use a bright-field microscope to observe the dispersed particles in the PVPP sample. Find a spherical particle in the PVPP sample and perform bright-field imaging. The bright-field image is shown in Figure 7 (a), and the solid line in Figure 7 (a) The area in the frame is the region of interest including the local particles, and the size of the region of interest in the bright field image is 10 μm*10 μm. Confocal scanning is performed on the area corresponding to the sample area of interest to obtain the Raman spectrum data set of PVPP sample particles. Among them, the scanning adopts an excitation wavelength of 532nm, a laser power of 10mw, a grating of 1200g/mm, an objective lens multiple of 50, a numerical aperture of 0.75, and a wavenumber of 0-1900cm ^-1 . The Raman spectrum of each point of the obtained Raman spectrum data set is processed to remove cosmic noise and background noise, and the processed Raman spectrum data set of PVPP sample particles is obtained. Subsequently, in the processed Raman spectrum data set, the spectral intensity I of each point of the Raman spectrum at the wave number k ₀ =934.2 cm ^-1 is used as the gray value of the point in the plane image to generate a Raman image of the Raman characteristic peak, The Raman images of the Raman characteristic peaks of the PVPP sample particles are shown in (b) in Figure 7, respectively.

In the obtained Raman image of the Raman characteristic peak of the PVPP sample particle, select the point with the highest gray value as the point of interest, as shown in (a) in Figure 8, where the point of interest is marked with a cross. According to the position in the sample corresponding to the point of interest, high-quality Raman spectra are extracted in the processed PVPP sample particle Raman spectrum data set, and the extracted high-quality Raman spectra are shown in (b) in Figure 8. Show.

Claims (3)

1. A method for extracting Raman spectra of complex compounds, characterized in that it is a method for extracting high-quality Raman spectra of compounds based on high spatial resolution optical microscopic imaging technology and Raman spectroscopy technology , including the following steps: (1) Take 1-5mg of the powder sample to be tested, place it on a glass slide, expose a diameter of 3-5mm, or a 3-5mm rectangle, or compact a 3-5mm rectangle surface into a thin layer, and make it to be tested sample; (2) Observe the sample to be tested under an optical microscope, look for a dispersed particle with a clear image and a wide range of morphological characteristics, perform bright field imaging on the dispersed particle, and select the point with the highest gray level on the particle in the imaging image as the sensor Points of Interest; (3) Light irradiation with a specific excitation wavelength is performed on the corresponding position of the point of interest in step (2) on the particle, and the Raman spectrum of the excitation wavelength at the corresponding position on the particle is measured. The Raman spectrum includes two Parameters k and I, k is the Raman shift wavenumber in the Raman spectrum, and I is the spectral intensity corresponding to the wavenumber k in the Raman spectrum; (4) Repeat step (3) multiple times to obtain the Raman spectrum of the excitation wavelength on multiple corresponding positions, and then average the spectral intensity I corresponding to the same wave number k in multiple Raman spectra to obtain the average Raman spectrum ; (5) In the average Raman spectrum calculated in step (4), find the Raman spectrum characteristic peak with high peak and sharp peak shape as the Raman spectrum characteristic peak of the analyte, and record the wave number corresponding to the Raman spectrum characteristic peak k ₀ ; (6) Observe the sample to be tested again under the optical microscope to find a dispersed particle with clear imaging and extensive morphology features, or directly use the particle found in step (2) to perform bright field imaging on the particle, which will contain A rectangular area of the whole or part of the particle is used as the area of interest; (7) Carry out confocal scanning to step (6) region of interest corresponding to the area on the sample to obtain a Raman spectrum data set, the Raman spectrum data set contains four parameters, are respectively x, y, k and I, wherein x and y corresponds to the plane coordinates of a point in the region of interest, k is the Raman shift wavenumber of the Raman spectrum measured at a point, and I is the spectral intensity corresponding to a wavenumber k in the Raman spectrum of a point; (8) each point Raman spectrum of the Raman spectrum data set obtained in step (7) is processed to remove cosmic noise and eliminate background noise, and obtain the processed Raman spectrum data set; (9) In the Raman spectrum data set after step (8) processing, the Raman image of the Raman characteristic peak is generated as the gray value of the point in the plane image at the wavenumber _k of each point of the Raman spectrum corresponding to the spectral intensity I ; (10) in the Raman image that step (9) obtains, select the highest point of the gray value as the point of interest; (11) According to the position of the point of interest obtained in step (10) in the sample, perform regional localization in the Raman spectrum data set processed in step (8) to extract the high-quality Raman spectrum of the corresponding position; The powder sample to be tested is a high-molecular-weight complex compound generated by cross-linking and polymerization reactions, including simple initial materials, intermediate products, and final products, and the products generated by cross-linking and polymerization reactions are cross-linked bodies with molecular weights in a certain range. 2. according to the extraction method of a kind of complex compound Raman spectrum according to claim 1, it is characterized in that, the powder sample to be detected is polyvinylpyrrolidone (PVP); The confocal Raman spectrum microscope WITec Alpha300-RAMAN was used for the optical microscope observation of sample particles, bright field image acquisition, Raman spectrum measurement and confocal scanning; the bright field image, Raman spectrum, Raman image and Display the region of interest and the point of interest, and perform data processing on the Raman spectrum and the Raman spectrum dataset, and extract high-quality Raman spectra from the Raman spectrum dataset; In step (1), take 2-5 mg of the PVP powder sample and place it on a glass slide, shake it slightly to disperse the sample powder particles as much as possible, cover the cover glass and then slightly roll the cover glass to further disperse the sample powder particles; In step (2), use a 50 times objective lens bright field microscope to observe the sample particles selected for Raman scanning; observations find that the particle shapes in the PVP sample are irregular, and according to the observation results, select an irregular shape particle in the PVP sample for Imaging, and select the point with the highest gray level on the particle in the imaging image as the point of interest through visual observation; In step (3), use the confocal Raman spectrum microscope WITec Alpha300-RAMAN to perform Raman spectrum measurement. The measurement uses an excitation wavelength of 532nm, a laser power of 10mw, a grating of 1200g/mm, an objective lens of 50 times, and a numerical aperture of 0.75, And the range of wave number is 0～1900cm ^-1 ; In step (4), use a confocal Raman spectrum microscope to perform 10 Raman spectrum measurements on the position on the PVP sample particle and perform an average calculation to obtain an average Raman spectrum; In step (5), the corresponding wavenumber k ₀ of the recorded Raman spectrum characteristic peak is 934.2cm ⁻¹ ; In step (6), the obtained region of interest is a square area of 20 μm*20 μm including the local PVP particles found in step (2); In step (7), use the confocal Raman spectroscopy microscope WITec Alpha300-RAMAN to perform confocal scanning. The scanning adopts an excitation wavelength of 532nm, a laser power of 10mw, a grating of 1200g/mm, an objective lens multiple of 50, and a numerical aperture of 0.75. And the wave number is 0 to 1900 cm ^-1 . 3. according to the extraction method of a kind of complex compound Raman spectrum according to claim 1, it is characterized in that, the powder sample to be detected is cross-linked polyvinylpyrrolidone (PVPP) powder; The confocal Raman spectrum microscope WITec Alpha300-RAMAN was used for the optical microscope observation of sample particles, bright field image acquisition, Raman spectrum measurement and confocal scanning; the bright field image, Raman spectrum, Raman image and Display the region of interest and the point of interest, and perform data processing on the Raman spectrum and the Raman spectrum dataset, and extract high-quality Raman spectra from the Raman spectrum dataset; In step (1), take 2-5 mg of the PVPP powder sample and place it on a glass slide, shake slightly to disperse the sample powder particles as much as possible, cover the cover glass and then slightly roll the cover glass to further disperse the sample powder particles; In step (2), use a 50 times objective lens bright-field microscope to observe the sample particles selected for Raman scanning; observe that most of the particles in the PVPP sample are spherical particles, and a very small part is very small irregular particles, according to Observe the results, select a spherical particle in the PVPP sample for imaging, and select the point with the highest gray level on the particle in the imaging image as the point of interest through visual observation; In step (3), use the confocal Raman spectrum microscope WITec Alpha300-RAMAN to perform Raman spectrum measurement. The measurement uses an excitation wavelength of 532nm, a laser power of 10mw, a grating of 1200g/mm, an objective lens of 50 times, and a numerical aperture of 0.75 and The range of wave number is 0～1900cm ^-1 ; In step (4), use a confocal Raman spectrum microscope to perform 10 Raman spectrum measurements on the PVPP sample particles and perform an average calculation to obtain an average Raman spectrum; In step (5), the corresponding wavenumber k ₀ of the recorded Raman spectrum characteristic peak is 934.2cm ⁻¹ ; In step (6), the obtained region of interest is a square region of 10 μm*10 μm that contains another PVPP sample particle that is found; In step (7), use the confocal Raman spectroscopy microscope WITec Alpha300-RAMAN to perform confocal scanning. The scanning adopts an excitation wavelength of 532nm, a laser power of 10mw, a grating of 1200g/mm, an objective lens multiple of 50, and a numerical aperture of 0.75. And the wave number is 0 to 1900 cm ^-1 .