A method for analyzing chemical concentration in liquids based on surface-enhanced Raman scattering

Abstract

The present invention discloses a method for analyzing the concentration of chemical substances in liquids based on surface-enhanced Raman scattering, comprising the following steps: step 1, preparing a series of standard solutions of the analyte with different concentrations to obtain a standard curve of the analyte; and step 2, using the standard curve to calculate the concentration of the analyte in the solution to be tested. Before performing Raman spectroscopy analysis in the two steps, the standard solution and the solution to be tested are subjected to the same pretreatment, wherein the pretreatment method is to add an adjuvant to each standard solution or the solution to be tested, mix them evenly, let them stand, and then filter to obtain a mixture; add an internal standard to the mixture, mix them evenly, and let them stand; then add nanoparticles, mix them evenly, let them stand, and finally perform Raman spectroscopy analysis. The method of the present invention uses adjuvants to promote the stable adsorption of the analyte on the surface of the nanoparticles, thereby enhancing the repeatability of the analysis. The adjuvants can also purify the sample and enhance the accuracy of the analysis, and has good application prospects in the field of analytical chemistry.

Description

Technical Field

[0001] The present invention relates to the technical field of analytical chemistry, and in particular to an analysis method for the concentration of chemical substances in a liquid based on surface enhanced Raman scattering. Background Art

[0002] There are many methods for measuring trace concentrations of analytes in liquid samples, but these typically require complex laboratory instrumentation and skilled personnel. These methods include ultraviolet spectroscopy, gas chromatography-mass spectrometry, high-performance liquid chromatography-mass spectrometry, and colorimetric titration. For example, mass spectrometry offers high sensitivity, providing precise molecular weight information for analytes, thereby determining their structure and content. However, these methods typically require expensive instrumentation, high-purity gases or liquids, and complex, time-consuming sample analysis.

[0003] Raman spectroscopy can "fingerprint" analytes based on the characteristic spectra of different chemicals. However, conventional Raman spectroscopy signals are weak and cannot identify analytes at the ppm level or below. However, if the analyte can be adsorbed on an active surface, its Raman signal can be significantly enhanced. This technique is called surface-enhanced Raman spectroscopy. Typically, this technique uses a flat substrate and forms nanoscale particles, depressions, or protrusions on the surface through deposition, laser, or electrochemical etching to enhance the Raman spectral intensity of the adsorbed analyte.

[0004] In some surface-enhanced Raman spectroscopy (SERS) techniques, nanoparticles are used to provide a surface for adsorption of analytes. When the wavelength of incident light is greater than the diameter of the nanoparticles, an alternating electromagnetic field is generated on the surface, significantly enhancing the Raman spectral signal. Despite significant progress in SERS technology in recent years, numerous challenges remain, hindering its commercialization. For example, reproducibility of analytical results is problematic, and selective recognition of specific molecules requires modification of the matrix or nanoparticle surface, limiting its universal applicability. Summary of the Invention

[0005] In view of the fact that the existing surface-enhanced Raman spectroscopy technology has poor reproducibility and requires modification of the matrix or nanoparticle surface, the present invention provides a method for analyzing the concentration of chemical substances in liquids based on surface-enhanced Raman scattering.

[0006] The present invention provides a method for analyzing the concentration of chemical substances in liquids based on surface-enhanced Raman scattering, comprising the following steps:

[0007] S1. Obtaining a standard curve for the analyte; including the following sub-steps:

[0008] S11. Prepare a series of standard solutions of the analyte at different concentrations.

[0009] S12. Add auxiliary agents to each standard solution, mix well, let stand for 0-1 hour, and then filter to obtain mixed solution A.

[0010] The adjuvant is selected from an aqueous solution of one or more of the following substances:

[0011] Alkali metal carboxylates, alkali metal carbonates, alkali metal bicarbonates, alkali metal phosphates, alkali metal monohydrogen phosphates, alkali metal dihydrogen phosphates, alkali metal hydroxides, alkali metal sulfates, alkali metal hydrogen sulfates, alkaline earth metal carboxylates, alkaline earth metal carbonates, alkaline earth metal bicarbonates, alkaline earth metal phosphates, alkaline earth metal monohydrogen phosphates, alkaline earth metal dihydrogen phosphates, alkaline earth metal hydroxides, alkaline earth metal sulfates, alkaline earth metal hydrogen sulfates, aldehyde compounds, ketone compounds, hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid.

[0012] Filtration is performed using filter paper, solid phase extraction cartridges, ion exchange cartridges, or filter elements with pore sizes ranging from 0.1 micron to 100 micron.

[0013] S13, adding the internal standard to the mixed solution A, mixing well and letting it stand for 0-1 hour; then adding the nanoparticles, mixing well and letting it stand for 0-1 hour to obtain a mixed solution B;

[0014] S14. Place mixed solution B on a hard substrate or container, perform Raman spectroscopy analysis, and then draw a standard curve using one of the following three methods:

[0015] Method 1: Draw a standard curve based on the ratio of the characteristic peak height or area of the analyte to the characteristic peak height or area of the internal standard. This method is used when the analyte, the excipient, and the internal standard cannot react to form a new substance with a Raman characteristic peak.

[0016] Method 2: Draw a standard curve based on the ratio of the characteristic peak height or area of the reaction product of the analyte and the excipient to the characteristic peak height or area of the internal standard. This method is used when the excipient reacts with the analyte to generate a new substance with a characteristic Raman peak.

[0017] Method 3: Draw a calibration curve based on the ratio of the characteristic peak height or area of the reaction product of the analyte and the internal standard to the characteristic peak height or area of the internal standard. This method is used when the internal standard can react with the analyte to produce a new substance with a characteristic Raman peak.

[0018] S2. Take the test solution containing the analyte and treat the test solution in the same manner as steps S12 and S13; then place the resulting mixed solution on a hard substrate or container and perform Raman spectroscopy analysis. Substitute the obtained characteristic peak height or area ratio with the characteristic peak height or area of the internal standard into the standard curve to calculate the concentration of the analyte in the test solution.

[0019] The method is applicable to analytes including nitro compounds, nitroso compounds, aldehyde compounds, ketone compounds, sulfhydryl compounds, cyanide, thiocyanide, amino compounds, imino compounds, tertiary amino compounds, quaternary ammonium salts, phosphonic acid compounds, and mixtures thereof. It is applicable to analyte concentrations ranging from 0.1 ppm to 1000 ppm.

[0020] The concentration of the adjuvant is 0.1 mol / L to 10 mol / L, and the volume ratio of the adjuvant to the standard solution is 1:99 to 99:1.

[0021] The solvent of the test solution can be water or other water-soluble solvents, or a mixture of water and solvents; water-soluble solvents include methanol, ethanol, ethylene glycol, isopropanol, glycerol, polyethylene glycol, acetone, acetonitrile and mixtures thereof.

[0022] The internal standard is selected from one of nitro compounds, nitroso compounds, sulfhydryl compounds, cyanide, thiocyanide, amino compounds, imino compounds, tertiary amino compounds, quaternary ammonium salts, phosphonic acid compounds, aldehyde compounds, and ketone compounds.

[0023] The nanoparticles are selected from one or more mixtures of gold nanoparticles, silver nanoparticles, copper nanoparticles, titanium oxide nanoparticles, and tungsten oxide nanoparticles.

[0024] The material of the hard substrate or container includes but is not limited to glass, plastic, steel, and aluminum.

[0025] Compared with the prior art, the present invention is beneficial in that:

[0026] (1) In addition to analyzing water-based liquid samples, it can also analyze liquid samples based on organic solvents;

[0027] (2) Use common chemicals instead of isotope-containing chemicals (such as 18 O) Chemicals as internal standards;

[0028] (3) A resting step was added to the analysis process, which enhanced the Raman signal intensity and the repeatability of the results;

[0029] (4) Filtering and purifying the liquid sample after mixing it with the adjuvant (rather than filtering and purifying the non-liquid sample before mixing it with the adjuvant) can better remove impurities and enhance the accuracy of the results;

[0030] (5) Using adjuvants to help the analyte to be stably adsorbed on the surface of nanoparticles, thereby enhancing the repeatability of the analysis; certain types of adjuvants can also react with the analyte to generate new substances with Raman characteristic peaks to selectively identify the analyte;

[0031] (6) The use of internal standards as references also enhances the accuracy and repeatability of the analysis; moreover, some internal standards can react with the analytes to generate new substances with Raman characteristic peaks, thereby selectively identifying the analytes.

[0032] (7) The nanoparticles used in this method do not require special surface modification and can recognize different analytes.

[0033] Other advantages, objectives and features of the present invention will be reflected in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the standard curve of methanolamine obtained in Example 1 of the present invention.

[0035] Figure 2 This is the standard curve of tetrakis(hydroxymethyl)phosphonium sulfate obtained in Example 2 of the present invention.

[0036] Figure 3 This is the standard curve of glutaraldehyde obtained in Example 3 of the present invention.

[0037] Figure 4 This is the standard curve of ethanolamine obtained in Example 4 of the present invention. DETAILED DESCRIPTION

[0038] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0039] Gold nanoparticles were used in the following examples and were prepared as follows:

[0040] Stir and heat 100 ml of a 0.6 mmol / L HAuCl₄ aqueous solution to boiling, then add 4 ml of a 1% sodium citrate solution. Continue stirring for 30 minutes while maintaining the temperature at 95°C to 98°C. Cool to room temperature and concentrate by centrifugation to obtain gold nanoparticles.

[0041] In other embodiments of the present invention, commercially available gold nanoparticles, silver nanoparticles, copper nanoparticles, titanium oxide nanoparticles, tungsten oxide nanoparticles, and mixtures thereof may also be used.

[0042] Example 1: Detecting the concentration of methanolamine in wastewater from a chemical plant.

[0043] In this example, the adjuvant facilitates the stable adsorption of the analyte, methanolamine, on the surface of the gold nanoparticles, thereby enhancing the repeatability of the analysis. The internal standard serves as a reference to enhance the accuracy and repeatability of the analysis. The specific analysis steps are as follows:

[0044] Step 1: Obtain a standard curve for methanolamine

[0045] 1.1. Dissolve methanolamine in deionized water and prepare solutions with concentrations of 1ppm, 5ppm, 10ppm, 50ppm, and 100ppm as standard solutions.

[0046] 1.2. Evenly mix 10 ml of the standard solution with 10 ml of the auxiliary agent, let it stand for 0.1 hour, and filter it through a polypropylene filter with a pore size of 0.45 μm to obtain a mixed solution A; the auxiliary agent is a mixed aqueous solution of sodium bicarbonate and sodium carbonate, with a sodium bicarbonate concentration of 0.0125 mol / L and a sodium carbonate concentration of 0.0875 mol / L.

[0047] 1.3. Dissolve the internal standard (sodium cyanide) in deionized water to prepare a 0.1 mmol / L internal standard solution; mix 1 mL of the internal standard solution with 10 mL of mixed solution A, let it stand for 0.1 hour, then add gold nanoparticles, mix well, and let it stand for 0.1 hour to obtain mixed solution B.

[0048] 1.4. Take 0.1 ml of mixed solution B and place it on a glass plate. Obtain Raman spectrum at an excitation wavelength of 785 nm. Draw a standard curve based on the ratio of the characteristic peak height of methanolamine to the characteristic peak height of cyanide ion. Figure 1 .

[0049] Step 2: Calculate the concentration of methanolamine in the wastewater sample using the standard curve

[0050] 2.1. Take 100 ml of wastewater sample containing methanolamine.

[0051] 2.2. Mix 10 ml of the wastewater sample with 10 ml of the auxiliary agent (0.0125 mol / L sodium bicarbonate + 0.0875 mol / L sodium carbonate aqueous solution), let it stand for 0.1 hour, and filter it using a polypropylene filter with a pore size of 0.45 μm to obtain a mixed solution C.

[0052] 2.3. Dissolve the internal standard (sodium cyanide) in deionized water to prepare a 0.1 mmol / L internal standard solution. Mix 1 mL of the internal standard solution with 10 mL of mixed solution C and let stand for 0.1 hour. Then, add gold nanoparticles, mix thoroughly, and let stand for 0.1 hour to obtain mixed solution D. The adjuvant promotes the stable adsorption of the analyte onto the gold nanoparticle surface, thereby enhancing analytical reproducibility.

[0053] 2.4. Take 0.1 ml of mixed solution D and place it on a glass plate. Obtain Raman spectrum at an excitation wavelength of 785 nm. Substitute the ratio of the characteristic peak height of methanolamine to the characteristic peak height of cyanide ion into Figure 1 The concentration of methanolamine in wastewater samples was calculated using the standard curve shown.

[0054] Steps 2.2 to 2.4 were repeated for the same wastewater sample to verify the accuracy and repeatability of the method. The results are shown in Table 1. In Table 1, sample numbers 1 and 2 represent two different wastewater samples containing methanolamine. Each wastewater sample was tested four times, resulting in four measured values. Tables 2-4 in the subsequent Examples 2-4 have the same meaning.

[0055] Table 1. Determination of methanolamine content in wastewater samples from a factory

[0056]

[0057] Example 2: Detecting the residual concentration of the fungicide tetrakis(hydroxymethyl)phosphonium sulfate (THPS) in an industrial wastewater.

[0058] In this example, the industrial waste liquid is based on the organic solvent methanol (90% methanol and 10% water), so the tetrakis(hydroxymethyl)phosphonium sulfate standard solution is prepared using the same ratio of methanol and water. This also demonstrates that the present invention is suitable for analyzing liquid samples based on organic solvents. In this example, the adjuvant promotes the stable adsorption of the analyte on the surface of the gold nanoparticles, thereby enhancing the repeatability of the analysis. The internal standard serves as a reference to enhance the accuracy and repeatability of the analysis.

[0059] Step 1: Obtain a standard curve for tetrakis(hydroxymethyl)phosphonium sulfate

[0060] 1.1. Dissolve tetrakis (hydroxymethyl) phosphine sulfate in a mixed solvent of 90% methanol and 10% deionized water to prepare standard solutions of 10 ppm, 50 ppm, 100 ppm, 500 ppm, and 1000 ppm, respectively.

[0061] 1.2. Mix 10 ml of the standard solution and 10 ml of the auxiliary agent (0.075 mol / L disodium hydrogen phosphate + 0.025 mol / L sodium dihydrogen phosphate aqueous solution) evenly, let it stand for 0.5 hours, and filter using a C18 solid phase extraction column to obtain mixed solution A.

[0062] 1.3. Dissolve the internal standard (tetrasodium ethylenediaminetetraacetic acid) in deionized water to prepare a 10 mmol / L internal standard solution; mix 1 ml of the internal standard solution with 10 ml of mixed solution A, let it stand for 0.5 hours, then add gold nanoparticles, mix well, and let it stand for 0.5 hours to obtain mixed solution B.

[0063] 1.4. Take 2 ml of mixed solution B and place it in a glass container. Obtain Raman spectrum at an excitation wavelength of 785 nm. Draw a standard curve based on the ratio of the characteristic peak height of tetrakis(hydroxymethyl)phosphonium sulfate to the characteristic peak height of ethylenediaminetetraacetic acid anion, see Figure 2 .

[0064] Step 2: Calculate the concentration of tetrakis(hydroxymethyl)phosphonium sulfate in wastewater samples using the standard curve

[0065] 2.1. Obtain 100 ml of wastewater sample containing tetrakis(hydroxymethyl)phosphine sulfate.

[0066] 2.2. Mix 10 ml of the wastewater sample with 10 ml of an auxiliary agent (0.075 mol / L disodium hydrogen phosphate + 0.025 mol / L sodium dihydrogen phosphate aqueous solution), let it stand for 0.5 hours, and filter using a C18 solid phase extraction column to obtain a mixed solution C.

[0067] 2.3. Dissolve the internal standard (tetrasodium ethylenediaminetetraacetic acid) in deionized water to prepare a 10 mmol / L internal standard solution; mix 1 mL of the internal standard solution with 10 mL of mixed solution C, let it stand for 0.5 hours, add gold nanoparticles, mix well, and let it stand for 0.5 hours to obtain mixed solution D.

[0068] 2.4. Take 2 ml of mixed solution D and place it in a glass container. Obtain Raman spectrum at an excitation wavelength of 785 nm. Substitute the ratio of the characteristic peak height of methanolamine to the characteristic peak height of cyanide ion into Figure 2 The concentration of tetrakis (hydroxymethyl) phosphine sulfate in wastewater samples was calculated using the standard curve shown.

[0069] For the same wastewater sample, steps 2.2 to 2.4 were repeated to verify the accuracy and repeatability of the method. The results are shown in Table 2.

[0070] Table 2. Determination of residual concentration of tetrakis(hydroxymethyl)phosphonium sulfate (THPS) in a certain industrial wastewater

[0071]

[0072]

[0073] Example 3: Detection of the residual concentration of glutaraldehyde in a certain industrial wastewater.

[0074] Glutaraldehyde is weakly adsorbed on nanoparticles, making it difficult to identify using other surface-enhanced Raman spectroscopy methods. In this embodiment, an adjuvant containing ethylamine is used. Ethylamine can react with glutaraldehyde to form imine compounds, which can strongly adsorb on the surface of nanoparticles and produce Raman characteristic peaks, thereby achieving the purpose of identifying glutaraldehyde. The adjuvant not only promotes the stable adsorption of the analyte on the surface of the nanoparticles, thereby enhancing the repeatability of the analysis; the adjuvant also reacts with the analyte to generate a new substance with Raman characteristic peaks to selectively identify the analyte. The specific analysis steps are as follows:

[0075] Step 1: Obtain a standard curve for glutaraldehyde

[0076] 1.1. Dissolve glutaraldehyde in deionized water to prepare 100ppm, 200ppm, 400ppm, and 500ppm standard solutions respectively.

[0077] 1.2. Mix 10 ml of the standard solution with 10 ml of an auxiliary agent (0.01 mol / L ethylamine, 0.0125 mol / L sodium bicarbonate, and 0.0875 mol / L sodium carbonate in water), let the solution stand for 0.1 hour, and filter it through a polypropylene filter with a pore size of 0.45 μm to obtain a mixed solution A.

[0078] 1.3. Dissolve the internal standard (sodium cyanide) in deionized water to prepare a 0.1 mmol / L internal standard solution; mix 1 mL of the internal standard solution with 10 mL of mixed solution A, let it stand for 0.1 hour, add gold nanoparticles, mix well, and let it stand for 0.1 hour to obtain mixed solution B.

[0079] 1.4. Take 0.1 ml of mixed solution B and place it in a glass container. Obtain Raman spectrum at an excitation wavelength of 785 nm. Draw a standard curve based on the ratio of the characteristic peak height of the imine compound generated by the reaction of ethylamine and glutaraldehyde to the characteristic peak height of the cyanide ion. Figure 3 .

[0080] Step 2: Calculate the concentration of glutaraldehyde in wastewater samples using the standard curve

[0081] 2.1. Obtain 100 ml of wastewater sample containing glutaraldehyde.

[0082] 2.2. Mix 10 ml of the wastewater sample with 10 ml of an auxiliary agent (an aqueous solution of 0.01 mol / L ethylamine, 0.0125 mol / L sodium bicarbonate, and 0.0875 mol / L sodium carbonate), let it stand for 0.1 hour, and filter it using a polypropylene filter with a pore size of 0.45 μm to obtain a mixed solution C.

[0083] 2.3. Dissolve the internal standard (sodium cyanide) in deionized water to prepare a 0.1 mmol / L internal standard solution. Mix 1 mL of the internal standard solution with 10 mL of mixed solution C and let stand for 0.1 hour. Then, add gold nanoparticles, mix thoroughly, and let stand for 0.1 hour to obtain mixed solution D.

[0084] 2.4. Take 0.1 ml of mixed solution D and place it in a glass container. Obtain Raman spectrum at an excitation wavelength of 785 nm. Substitute the ratio of the characteristic peak height of the imine compound generated by the reaction of ethylamine and glutaraldehyde to the characteristic peak height of the cyanide ion into Figure 3 The concentration of methanolamine in wastewater samples was calculated using the standard curve shown.

[0085] For the same wastewater sample, steps 2.2 to 2.4 were repeated to verify the accuracy and repeatability of the method. The results are shown in Table 3.

[0086] Table 3. Determination of residual concentration of glutaraldehyde in a certain industrial wastewater

[0087]

[0088] Example 4: Detection of trace ethanolamine concentration in triethanolamine, an industrial raw material

[0089] Both triethanolamine and ethanolamine can be adsorbed on the nanoparticle surface, produce similar Raman spectra, and do not contain water in the sample, and it is more difficult to identify using other surface-enhanced Raman spectroscopy methods. In the present embodiment, acetaldehyde was used as an internal standard. Ethanolamine can react with acetaldehyde to generate imine compounds, which can be strongly adsorbed on the nanoparticle surface and produce Raman characteristic peaks, while triethanolamine cannot react with acetaldehyde, thereby reaching the purpose of distinguishing and identifying ethanolamine. The effect of the adjuvant is to promote the stable adsorption of the analyte on the nanoparticle surface.

[0090] The specific analysis steps are as follows:

[0091] Step 1: Obtain a standard curve for ethanolamine

[0092] 1.1. Dissolve ethanolamine in triethanolamine to prepare 10ppm, 20ppm, 30ppm, and 40ppm standard solutions respectively.

[0093] 1.2. Mix 10 ml of the standard solution with 10 ml of the auxiliary agent (0.0125 mol / L sodium bicarbonate + 0.0875 mol / L sodium carbonate in water), let it stand for 0.1 hour, and filter it through a polypropylene filter with a pore size of 0.45 μm to obtain mixed solution A.

[0094] 1.3. Dissolve the internal standard (acetaldehyde) in deionized water to prepare a 100 mmol / L internal standard solution; mix 1 ml of the internal standard solution with 10 ml of mixed solution A, let it stand for 0.1 hour, add gold nanoparticles, mix well, and let it stand for 0.1 hour to obtain mixed solution B.

[0095] 1.4. Take 0.1 ml of mixed solution B and place it in a glass container. Obtain Raman spectrum at an excitation wavelength of 785 nm. Draw a standard curve based on the ratio of the characteristic peak height of the imine compound generated by the reaction of ethanolamine and acetaldehyde to the characteristic peak height of acetaldehyde. Figure 4 .

[0096] Step 2: Calculate the concentration of ethanolamine in the raw material using the standard curve

[0097] 2.1. Obtain 100 ml of triethanolamine sample, an industrial raw material.

[0098] 2.2. Mix 10 ml of triethanolamine sample with 10 ml of auxiliary agent (0.0125 mol / L sodium bicarbonate + 0.0875 mol / L sodium carbonate aqueous solution), let it stand for 0.1 hour, and filter it through a polypropylene filter with a pore size of 0.45 μm to obtain mixed solution C.

[0099] 2.3. Dissolve the internal standard (acetaldehyde) in deionized water to prepare a 100 mmol / L internal standard solution. Mix 1 mL of the internal standard solution with 10 mL of mixed solution C and let stand for 0.1 hour. Then, add gold nanoparticles, mix thoroughly, and let stand for 0.1 hour to obtain mixed solution D.

[0100] 2.4. Take 0.1 ml of mixed solution D and place it in a glass container. Obtain Raman spectrum at an excitation wavelength of 785 nm. Substitute the ratio of the characteristic peak height of the imine compound generated by the reaction of ethanolamine and acetaldehyde to the characteristic peak height of acetaldehyde into Figure 4 The concentration of ethanolamine in the samples was calculated using the standard curve shown.

[0101] For the same wastewater sample, steps 2.2 to 2.4 were repeated to verify the accuracy and repeatability of the method. The results are shown in Table 4.

[0102] Table 4. Determination of residual concentration of glutaraldehyde in a certain industrial wastewater

[0103]

[0104] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for analyzing the concentration of chemical substances in liquids based on surface-enhanced Raman scattering, characterized in that: Here are the steps: S1. Obtaining a standard curve of the analyte; The following sub-steps are included: S11. Prepare a series of analyte standard solutions of different concentrations; S12, adding auxiliary agents to each standard solution, mixing evenly, letting it stand for 0-1h and then filtering to obtain mixed solution A; The adjuvant is selected from an aqueous solution of one or more of the following substances: Alkali metal carboxylates, alkali metal carbonates, alkali metal hydrogencarbonates, alkali metal phosphates, alkali metal monohydrogenphosphates, alkali metal dihydrogenphosphates, alkali metal hydroxides, alkali metal sulfates, alkali metal hydrogensulfates, alkaline earth metal carboxylates, alkaline earth metal carbonates, alkaline earth metal hydrogencarbonates, alkaline earth metal phosphates, alkaline earth metal monohydrogenphosphates, alkaline earth metal dihydrogenphosphates, alkaline earth metal hydroxides, alkaline earth metal sulfates, alkaline earth metal hydrogensulfates, aldehyde compounds, ketone compounds, hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid; S13, adding an internal standard substance to the mixed solution A, mixing evenly and letting it stand for 0-1 hour; then adding nanoparticles, mixing evenly and letting it stand for 0-1 hour to obtain a mixed solution B; the internal standard substance is selected from one of nitro compounds, nitroso compounds, sulfhydryl compounds, cyanide, thiocyanide, amino compounds, imino compounds, tertiary amino compounds, quaternary ammonium salts, phosphonic acid compounds, aldehyde compounds, and ketone compounds; the nanoparticles are selected from one or more mixtures of gold nanoparticles, silver nanoparticles, copper nanoparticles, titanium oxide nanoparticles, and tungsten oxide nanoparticles; S14. Perform Raman spectroscopy analysis on mixed solution B, and then select one of the following three methods to draw a standard curve: Method 1: Draw a standard curve based on the ratio of the height or area of the characteristic peak of the analyte to the characteristic peak of the internal standard; Method 2: Draw a standard curve based on the ratio of the height or area of the characteristic peak of the reaction product of the analyte and the auxiliary to the characteristic peak of the internal standard; Method 3: Draw a standard curve based on the ratio of the height or area of the characteristic peak of the reaction product of the analyte and the internal standard to the characteristic peak of the internal standard; S2. Take a test solution containing the analyte and treat the test solution in the same manner as steps S12 and S13; then perform Raman spectroscopy analysis on the resulting mixed solution, and substitute the obtained characteristic peak with the height or area ratio of the internal standard characteristic peak into the standard curve to calculate the concentration of the analyte in the test solution.

2. The method for analyzing the concentration of chemical substances in liquids based on surface-enhanced Raman scattering according to claim 1, wherein: The analytes include nitro compounds, nitroso compounds, aldehyde compounds, ketone compounds, mercapto compounds, cyanide, thiocyanide, amino compounds, imino compounds, tertiary amino compounds, quaternary ammonium salts, phosphonic acid compounds and mixtures thereof.

3. The method for analyzing the concentration of chemical substances in liquid based on surface enhanced Raman scattering according to claim 2, wherein: The analyte concentration ranges from 0.1 ppm to 1000 ppm.

4. The method for analyzing the concentration of chemical substances in liquid based on surface enhanced Raman scattering according to claim 3, wherein: The concentration of the adjuvant is 0.1 mol / L to 10 mol / L, and the volume ratio of the adjuvant to the standard solution is 1:99 to 99:

1.

5. The method for analyzing the concentration of chemical substances in liquid based on surface enhanced Raman scattering according to claim 3, wherein: In step S12, filtering is performed using filter paper, a solid phase extraction column, an ion exchange column, or a filter element with a pore size of 0.1 micron to 100 micron.

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