Application of salicylaldehyde Schiff base chiral polymer in detection of iron and copper ions

Abstract

The invention belongs to the technical field of high polymer chemistry and material science, and particularly relates to application of a salicylaldehyde Schiff base chiral polymer in iron and copper ion detection, and the structural formula of the salicylaldehyde Schiff base chiral polymer is one of the following structures shown in the specification. . The salicylaldehyde Schiff base chiral polymer has high selectivity to copper ions and iron ions, and qualitative detection of the copper ions and the iron ions can be achieved according to changes of ultraviolet absorption spectrums, digital circular dichroism spectrums and fluorescence spectrums before and after coordination of the salicylaldehyde Schiff base chiral polymer with the copper ions and the iron ions.

Description

Technical Field

[0001] This invention belongs to the field of polymer chemistry and materials science, specifically relating to the application of salicylaldehyde Schiff base chiral polymers in the detection of copper and iron ions. Background Technology

[0002] Research on the properties of novel luminescent chiral polymers has always been an important strategy for expanding and enriching the functional fields of polymers. Luminescent polymers possess advantages such as high efficiency in luminescence, film-forming ability, good stability, and ease of functional integration; chiral polymers exhibit a significant chiral amplification effect, thus chiral luminescent polymers possessing both chiral and luminescent properties have attracted widespread attention from researchers. Furthermore, traditional luminescent polymers often exhibit good fluorescence properties in solution, but due to strong π-π stacking interactions, their aggregated state essentially does not emit fluorescence or emits weak fluorescence. However, the practical application of most polymer materials requires their fabrication into solid films or other aggregated forms, which greatly limits their application range. AIE chiral polymers are increasingly attracting attention due to their unique chiral amplification effect and the advantages of aggregated-state luminescence. Salen-like compounds containing two C=N and two OH groups exhibit significant AIE properties, and the nitrogen atom in salon-like compounds possesses a lone pair of electrons, while the metal ion provides an empty orbital, making it easy for the two to form complexes. Therefore, salon-containing chiral polymers can achieve multiple signal responses to a single metal ion stimulus. Current research on AIE chiral polymers mainly focuses on small molecule systems, while research on polymer systems remains scarce. Therefore, developing novel AIE chiral polymers and exploring their important roles in fields such as ion detection, stimulus response, 3D display, information encryption, optoelectronic devices, and intelligent detection is crucial. Summary of the Invention

[0003] The purpose of this invention is to address the aforementioned problems in the prior art by providing an application of salicylaldehyde Schiff base chiral polymers in the detection of copper and iron ions. This invention achieves the detection of copper and iron ions through the triple response characteristics of ultraviolet absorption spectroscopy, digital circular dichroism spectroscopy, and fluorescence spectroscopy.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] In a first aspect, the present invention provides an application of a salicylaldehyde Schiff base chiral polymer in the detection of copper and iron ions; the structural formula of the salicylaldehyde Schiff base chiral polymer is one of the following structures:

[0006] ;

[0007] ;

[0008] Where n is an integer between 2 and 50.

[0009] The application includes: preparing a salicylaldehyde Schiff base chiral polymer solution, adding the sample solution to be tested dropwise to the salicylaldehyde Schiff base chiral polymer solution, and achieving qualitative detection of copper ions and iron ions based on ultraviolet absorption spectroscopy, digital circular dichroism spectroscopy and fluorescence spectroscopy.

[0010] The presence of iron ions in the sample solution is determined if the following conditions are met simultaneously:

[0011] The ultraviolet absorption spectrum shows characteristic ultraviolet absorption peaks at 316 nm and 363 nm.

[0012] The digital circular dichroism spectrum exhibits a negative Cotton effect at 343 nm and a positive Cotton effect at 387 nm.

[0013] The fluorescence spectrum shows a decrease in fluorescence intensity;

[0014] The presence of copper ions in the test sample solution is determined if the following conditions are met simultaneously:

[0015] The ultraviolet absorption spectrum shows characteristic ultraviolet absorption peaks at 290 nm and 378 nm.

[0016] The digital circular dichroism spectrum exhibits a positive Cotton effect at 343 nm and 413 nm, and a negative Cotton effect at 378 nm.

[0017] The fluorescence spectrum shows a decrease in fluorescence intensity.

[0018] Secondly, the present invention provides a method for preparing a salicylaldehyde Schiff base chiral polymer, the method comprising: mixing a salicylaldehyde basic reactive monomer, a dichiral amine and an organic solvent, stirring the reaction until a transparent yellow solution is obtained and then stopping the reaction, and then purifying the obtained reaction product to obtain the salicylaldehyde Schiff base chiral polymer, wherein the salicylaldehyde basic reactive monomer is a di- or poly-2-hydroxybenzaldehyde compound, and the feed ratio of the monomer to the dichiral amine is 2 / m:1, where m is the number of salicylaldehyde units in the salicylaldehyde basic reactive monomer.

[0019] The dichiral amine is (1R,2R) / (1S,2S)-(+)-1,2-diphenylethylenediamine, and the di-2-hydroxybenzaldehyde compound is 4,4'-(9,9-dodecyl-9H-fluorene-2,7-diyl)bis(2-hydroxybenzaldehyde).

[0020] The organic solvent is at least one of dichloromethane, ethyl acetate, tetrahydrofuran, and N,N-dimethylformamide, and the amount of organic solvent used is 1-5 mL of organic solvent for every 0.5 mmol of dichiral amine.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. The salicylaldehyde Schiff base chiral polymer prepared in this invention exhibits high selectivity for copper and iron ions.

[0023] 2. The salicylaldehyde Schiff base chiral polymer prepared in this invention can detect copper ions and iron ions based on the changes in ultraviolet absorption spectrum, digital circular dichroism spectrum, and fluorescence spectrum before and after coordination with copper ions and iron ions, respectively. Attached Figure Description

[0024] Figure 1 This is a schematic diagram illustrating the reaction principle for preparing salicylaldehyde Schiff base chiral polymers in Example 1 of the present invention.

[0025] Figure 2 This is a schematic diagram illustrating the reaction principle for preparing salicylaldehyde Schiff base-type chiral model compounds in Example 2 of the present invention.

[0026] Figure 3 Comparison of the proton NMR spectra of the salicylaldehyde Schiff base chiral polymer prepared in Example 1 and the model compound prepared in Example 2.

[0027] Figure 4 Comparison of the carbon NMR spectra of the salicylaldehyde Schiff base chiral polymer prepared in Example 1 and the model compound prepared in Example 2.

[0028] Figure 5 The graph shows the change in mass of SS-P1 prepared in Example 1 of this invention as a function of temperature.

[0029] Figure 6 The graph shows the relative fluorescence intensity of SS-P1 prepared in Example 1 of this invention as a function of water content.

[0030] Figure 7 The image shows the UV absorption spectra of SS-P1 prepared in Example 1 of this invention before and after coordination with different metal ions.

[0031] Figure 8 The digital circular dichroism chromatograms of SS-P1 prepared in Example 1 of this invention before and after coordination with different metal ions are shown.

[0032] Figure 9 SS-P1 and Fe prepared in Example 1 of this invention 3+ Ions, Cu 2+ Fluorescence spectra of ions before and after coordination.

[0033] Figure 10 The image shows the UV absorption spectra of SS-1 prepared in Example 2 of this invention before and after coordination with different metal ions.

[0034] Figure 11The digital circular dichroism chromatograms are of SS-1 prepared in Example 2 of this invention before and after coordination with different metal ions.

[0035] Figure 12 SS-1 and Fe prepared in Example 2 of this invention 3+ Ions, Cu 2+ Fluorescence spectra of ions before and after coordination.

[0036] Figure 13 SS-1 and Fe prepared in Example 2 of this invention 3+ Ions, Cu 2+ Chemical structural formulas of metal complexes before and after ion coordination, and corresponding single-crystal structure diagrams. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0038] Example 1:

[0039] A method for preparing a salicylaldehyde Schiff base chiral polymer, specifically comprising:

[0040] (1R,2R) / (1S,2S)-(+)-1,2-diphenylethylenediamine (28.6 mg, 0.135 mmol) and 4,4'-(9,9-dodecyl-9H-fluorene-2,7-diyl)bis(2-hydroxybenzaldehyde) (100 mg, 0.135 mmol) were added to a 10 mL polymerization tube and dissolved in 3 mL of N,N-dimethylformamide. The reaction was carried out at 80 °C for 1 h until the reaction solution gradually changed from turbid to a transparent yellow solution, at which point the reaction was stopped. After cooling the resulting reaction solution to room temperature, another 3 mL of N,N-dimethylformamide was added and dissolved completely. The resulting transparent yellow solution was slowly added dropwise to 100 mL of methanol. After standing, yellow flocculent matter appeared. The yellow flocculent matter was separated, filtered, and dried to obtain yellow solid powders RR-P1 (110 mg) and SS-P1 (115 mg).

[0041] The salicylaldehyde Schiff base chiral polymer is obtained by reacting salicylaldehyde basic reactive monomers with dichiral amines, and the reaction equation is as follows: Figure 1 As shown, Figure 1 middle , , , All are H or alkyl groups. The aryl group is substituted with an aryl or alkyl group; the structural formula of SS-P1 is:

[0042] ;

[0043] The structural formula of RR-P1 is:

[0044] ;

[0045] In this embodiment, 4,4'-(9,9-dodecyl-9H-fluorene-2,7-diyl)bis(2-hydroxybenzaldehyde) was prepared according to reference (Tetrahedron: Asymmetry 2012, 23, 570-576). Compared with the monomer 4,4'-(9,9-dihexyl-9H-fluorene-2,7-diyl)bis(2-hydroxybenzaldehyde) used in patent number ZL202010135837.2, the alkyl chain is longer, the synthesized polymer has better solubility, and it is more conducive to the occurrence of chemical reactions. (1R,2R) / (1S,2S)-(+)-1,2-diphenylethylenediamine was purchased from Amex Pharmaceuticals, and N,N-dimethylformamide was purchased from Sigma.

[0046] Example 2:

[0047] A method for preparing a chiral model compound of salicylaldehyde Schiff base, specifically comprising:

[0048] Add (1R,2R) / (1S,2S)-(+)-1,2-diphenylethylenediamine (1.1 g, 5.0 mmol) and 4-bromo-2-hydroxybenzaldehyde (2.0 g, 10 mmol) to a 100 mL two-necked flask and dissolve in 30 mL. N,N-Dimethylformamide was reacted at 80℃ for 1 h. After the reaction solution cooled to room temperature, it was repeatedly extracted three times with 300 mL of dichloromethane and 100 mL of deionized water. The organic phases were combined and dried with anhydrous sodium sulfate. The combined organic phases were filtered and evaporated to obtain a mixed crude product. Then, petroleum ether / dichloromethane (1:2) was used as the developing solvent, and silica gel column chromatography was used for further separation and purification to obtain a yellow solid crude product. The crude product was dissolved with a small amount of DCM, heated to 50℃ until reflux, and then anhydrous ethanol was gradually added for recrystallization. The product was then filtered and placed in a vacuum drying oven at 40℃ for 6 h to obtain dried yellow solid powders RR-1 and SS-1 with yields of 87% and 85%, respectively.

[0049] The salicylaldehyde Schiff base chiral model compound is obtained by reacting 4-bromo-2-hydroxybenzaldehyde with a dichiral amine, and the reaction equation is as follows: Figure 2 As shown; the structural formula of SS-1 is:

[0050] ;

[0051] The structural formula of RR-1 is:

[0052] ;

[0053] In this embodiment, 4-bromo-2-hydroxybenzaldehyde was purchased from Anaiji Pharmaceutical Company.

[0054] Analysis revealed that the yield of the salicylaldehyde Schiff base chiral polymer SS-P1 was as high as 88%, with an average molecular weight of 16100 g / mol and a molecular weight distribution of 1.48; the yield of the salicylaldehyde Schiff base chiral polymer RR-P1 was 87%, with an average molecular weight of 14400 g / mol and a molecular weight distribution of 1.27; the yield of the salicylaldehyde Schiff base chiral model compound SS-1 was as high as 87%; and the yield of the salicylaldehyde Schiff base chiral model compound RR-1 was 85%.

[0055] Comparison of 1H NMR spectra of salicylaldehyde Schiff base chiral polymers and model compounds (* represents solvent peaks) as shown below. Figure 3 As shown, its carbon NMR spectrum comparison diagram is as follows: Figure 4 As shown. From Figure 3 As can be seen, the characteristic peak of the hydrogen atom in the polymer -OH group is located at a chemical shift of 13.48 ppm, the characteristic peak of the hydrogen atom in -HC=N- group is located at a chemical shift of 8.37 ppm, and the characteristic peak of the hydrogen atom on the chiral carbon is located at a chemical shift of 4.79 ppm. This confirms that the polymer is a chiral polymer of salicylaldehyde Schiff base type. Similarly, the characteristic peak of the hydrogen atom in the model compound -OH group is located at a chemical shift of 13.70 ppm, the characteristic peak of the hydrogen atom in the model compound -HC=N- group is located at a chemical shift of 8.51 ppm, and the characteristic peak of the hydrogen atom on the chiral carbon is located at a chemical shift of 5.10 ppm. This confirms that the polymer is a chiral model compound of salicylaldehyde Schiff base type. Figure 4 As can be seen, the characteristic peak of the carbon atom bonded to the -OH group in the polymer is located at 165.72 ppm, the characteristic peak of the C=N carbon atom is located at a chemical shift of 161.24 ppm, and the characteristic peak of the chiral carbon atom is located at a chemical shift of 80.35 ppm, confirming that this polymer is a chiral polymer of salicylaldehyde Schiff base type. Similarly, the characteristic peak of the carbon atom bonded to the -OH group in the model compound is located at 165.49 ppm, the characteristic peak of the C=N carbon atom in the model compound is located at a chemical shift of 161.62 ppm, and the characteristic peak of the chiral carbon atom is located at a chemical shift of 80.04 ppm, confirming that this polymer is a chiral model compound of salicylaldehyde Schiff base type. The chemical shifts of the three hydrogen atom characteristic peaks of the polymer are all higher than those of the model compound, which may be due to the more rigid structure of the polymer compared to the model compound.

[0056] Figure 5 The graph shows the mass change of salicylaldehyde Schiff base chiral polymers as a function of temperature. Figure 5 As can be seen, the temperatures of SS-P1 and RR-P1 when losing 5% of their mass are as high as 297℃ and 292℃, respectively, which verifies that the polymer has high thermal stability.

[0057] First, dissolve SS-P1 (2.2 mg, 0.003 mmol) in 3 mL of tetrahydrofuran (THF) as the stock solution (1.0 × 10⁻⁶). -3 M) Reserved; 30 μL of the stock solution was quantitatively extracted using a pipette and added to 3 mL of THF / water mixture to obtain SS-P1 mixture. The water content of the THF / water mixture was 0 vol%, 10 vol%, 20 vol%, 30 vol%, 40 vol%, 50 vol%, 60 vol%, 70 vol%, 80 vol%, 90 vol%, and 99 vol%. The fluorescence intensity of the 11 different water contents of the SS-P1 mixture was then measured using 360 nm as the excitation wavelength. The fluorescence intensity of each of the 11 different water contents of the SS-P1 mixture was compared with the fluorescence intensity of the pure THF solution to obtain the relative fluorescence intensity. A curve showing the change in relative fluorescence intensity with water content was plotted as follows. Figure 6 As shown. From Figure 6 As can be seen, the relative fluorescence intensity gradually increases with the increase of water content, exhibiting a significant AIE effect.

[0058] Example 3:

[0059] Place salicylaldehyde Schiff base chiral polymers or model compounds and tetrahydrofuran into a 3mL cuvette (10... - 5 mol / L), and then prepare an aqueous solution of metal ions (10 mol / L). -5 (mol / L), then add the metal ion aqueous solution dropwise to the cuvette at 5 equivalents, mix thoroughly, and then test the UV absorption spectrum, digital circular dichroism spectrum, and fluorescence spectrum of the polymer after metal ion coordination at the same test wavelength (360 nm); the metal ions include Fe 3+ Cu 2+ Al 3+ Cs + Cd 2+ Co 2+ 、Sm 3+ Ce 3 + 、Tb 3+ Eu 3+ .

[0060] Fe 3+ After ion coordination, SS-P1 (abbreviated as SS-P1-Fe) 3+ The structural formula of ) is:

[0061] ;

[0062] Cu 2+After ion coordination, SS-P1 (abbreviated as SS-P1-Cu) 2+ The structural formula of ) is:

[0063] ;

[0064] Fe 3+ After ion coordination, RR-P1 (abbreviated as RR-P1-Fe) 3+ The structural formula of ) is:

[0065] ;

[0066] Cu 2+ After ion coordination, RR-P1 (abbreviated as RR-P1-Cu) 2+ The structural formula of ) is:

[0067] ;

[0068] Fe 3+ After ion coordination, SS-1 (abbreviated as SS-1-Fe) 3+ The structural formula of ) is:

[0069] ;

[0070] Cu 2+ After ion coordination, SS-1 (abbreviated as SS-1-Cu) 2+ The structural formula of ) is:

[0071] ;

[0072] Fe 3+ After ion coordination, RR-1 (abbreviated as RR-1-Fe) 3+ The structural formula of ) is:

[0073] ;

[0074] Cu 2+ After ion coordination, RR-1 (abbreviated as RR-1-Cu) 2+ The structural formula of ) is:

[0075] .

[0076] Figure 7 The images show the UV absorption spectra of the salicylaldehyde Schiff base-based chiral polymer SS-P1 prepared in Example 1 of this invention before and after coordination with different metal ions. Figure 7 As shown, SS-P1 exhibits a distinct ultraviolet absorption characteristic peak at 356 nm. SS-P1 and Fe 3+ After ion coordination, obvious UV absorption characteristic peaks appear at 316 nm and 363 nm, indicating that SS-P1 and Cu...2+ After coordination with other metal ions, obvious ultraviolet absorption characteristic peaks appear at 290 nm and 378 nm; after coordination with other metal ions, the peak shape and intensity of the ultraviolet absorption spectrum do not change much.

[0077] Figure 8 The images show digital circular dichroism chromatograms of the salicylaldehyde Schiff base chiral polymer SS-P1 prepared in Example 1 of this invention before and after coordination with different metal ions. Figure 8 As shown, SS-P1 exhibits a negative Cotton effect at 338 nm and a positive Cotton effect at 375 nm; SS-P1 and Fe 3+ After ion coordination, the digital circular dichroism chromatogram changed significantly, exhibiting a negative Cotton effect at 343 nm and a positive Cotton effect at 387 nm; SS-P1 and Cu 2+ After ion coordination, the digital circular dichroism chromatogram also changed significantly, exhibiting a positive Cotton effect at 343 nm and 413 nm, and a negative Cotton effect at 378 nm; it is evident that Fe... 3+ Ions and Cu 2+ The absolute configuration of the polymer was changed after the ions coordinated with SS-P1; however, the digital circular dichroism chromatogram remained basically unchanged before and after SS-P1 coordinated with other metal ions.

[0078] Figure 9 The salicylaldehyde Schiff base chiral polymer SS-P1 prepared in Example 1 of this invention and Fe 3+ Ions, Cu 2+ Fluorescence spectra of ions before and after coordination. (Example:) Figure 9 As shown, SS-P1 exhibits yellow-green fluorescence in tetrahydrofuran solution, with the spectral center located at 512 nm. With the increase of Fe... 3+ Ions, Cu 2+ The addition of ions individually significantly weakened the fluorescence.

[0079] Figure 10 The image shows the UV absorption spectra of the salicylaldehyde Schiff base-type chiral model compound SS-1 prepared in Example 2 of this invention before and after coordination with different metal ions. Figure 10 As shown, compared with SS-P1, the UV absorption characteristic peak of SS-1 shows a significant blue shift, with a distinct UV absorption characteristic peak appearing at 317 nm. This indicates that the polymer has a stronger degree of conjugation compared to the model compound; SS-1 and Fe 3+ After ion coordination, obvious UV absorption characteristic peaks appear at 319 nm and 361 nm; SS-1 and Cu 2+ After coordination with other metal ions, a distinct ultraviolet absorption peak appears at 369 nm. The shape and intensity of the ultraviolet absorption peak of SS-1 after coordination with other metal ions are basically unchanged.

[0080] Figure 11 The digital circular dichroism chromatograms are shown for the salicylaldehyde Schiff base chiral model compound SS-1 prepared in Example 2 of this invention before and after coordination with different metal ions. Figure 11 As shown, SS-1 exhibits a positive Cotton effect at 329 nm; SS-1 and Fe 3+ After coordination of the ions, the digital circular dichroism chromatogram changed significantly, exhibiting a positive Cotton effect at 331 nm; SS-1 and Cu 2+ After coordination of the ions, the digital circular dichroism chromatogram also changed significantly, exhibiting a negative Cotton effect at 360 nm and 405 nm, indicating that Fe... 3+ Ions and Cu 2+ The coordination of ions altered the absolute configuration of the model compounds; however, the digital circular dichroism chromatograms remained largely unchanged before and after coordination of other metal ions with SS-1.

[0081] Figure 12 The salicylaldehyde Schiff base chiral model compound SS-1 and Fe prepared in Example 2 of this invention 3+ Ions, Cu 2+ Fluorescence spectra of ions before and after coordination. (Example:) Figure 12 As shown, SS-1 exhibits weak yellow-green fluorescence in tetrahydrofuran solution, with the spectral center located at 479 nm. With the increase of Fe... 3+ Ions, Cu 2+ Ions are added separately to quench the fluorescence.

[0082] Figure 13 The salicylaldehyde Schiff base chiral model compound SS-1 and Fe prepared in Example 2 of this invention 3+ Ions, Cu 2+ Chemical structural formulas and corresponding single-crystal structures of ion-coordinated metal complexes. For example... Figure 13 As shown in Figure B, the single-crystal structure of the metal complex verifies that the two metal ions can coordinate with the Salen motif and that the coordination mode is tetracoordinate, which reveals that Fe 3+ Ions, Cu 2+ Coordination mechanisms between ions and polymers.

[0083] Figures 7 to 10 It showed that only Fe among the 10 metal ions was present. 3+ Ions, Cu 2+ After coordination of ions with polymers, the UV absorption wavelength and peak shape changed significantly, the Cotton effect in the digital circular dichroism chromatogram changed, and Fe... 3+ Ions, Cu 2+The fluorescence intensity of polymeric ions decreased significantly after coordination with the polymer, but the UV absorption spectra, digital circular dichroism chromatograms, and fluorescence spectra of the other eight common metal ions remained largely unchanged after coordination with the polymer. Due to the high complexity of the structures of polymer metal complexes, it is difficult to study their coordination mechanisms, optical properties, and chiral properties. Therefore, the relevant properties and mechanisms of polymer metal complexes can be indirectly explored by referencing the coordination modes, optical properties, and chiral properties of metal complexes of model compounds. Figures 10 to 12 The changes in the UV absorption spectrum, digital circular dichroism chromatogram, and fluorescence spectrum of the model compound after coordination with different metal ions are shown to be basically similar to those of the polymer. Figure 13 The model compound and Fe were demonstrated 3+ Ions, Cu 2+ The single-crystal structure of the metal complex of the ions revealed that the metal ions are bound to the polymer in a four-coordinate manner.

[0084] Referring to patent number ZL202010135837.2, the salicylaldehyde Schiff base chiral polymers SS-P1 and RR-P1 prepared in this invention have mirror-symmetric structures, their fluorescence spectra and ultraviolet absorption spectra are almost similar, and their digital circular dichroism chromatograms show the opposite Cotton effect.

Claims

1. The application of salicylaldehyde Schiff base chiral polymers in the detection of copper and iron ions, characterized by: The salicylaldehyde Schiff base chiral polymer has one of the following structural formulas: ； ； Where n is an integer between 2 and 50.

2. The application of the salicylaldehyde Schiff base chiral polymer according to claim 1 in the detection of copper and iron ions, characterized in that: The application includes: preparing a salicylaldehyde Schiff base chiral polymer solution, adding the sample solution to be tested dropwise to the salicylaldehyde Schiff base chiral polymer solution, and achieving qualitative detection of copper ions and iron ions based on ultraviolet absorption spectroscopy, digital circular dichroism spectroscopy and fluorescence spectroscopy. The presence of iron ions in the sample solution is determined if the following conditions are met simultaneously: The ultraviolet absorption spectrum shows characteristic ultraviolet absorption peaks at 316 nm and 363 nm. The digital circular dichroism spectrum exhibits a negative Cotton effect at 343 nm and a positive Cotton effect at 387 nm. The fluorescence spectrum shows a decrease in fluorescence intensity; The presence of copper ions in the test sample solution is determined if the following conditions are met simultaneously: The ultraviolet absorption spectrum shows characteristic ultraviolet absorption peaks at 290 nm and 378 nm. The digital circular dichroism spectrum exhibits a positive Cotton effect at 343 nm and 413 nm, and a negative Cotton effect at 378 nm. The fluorescence spectrum shows a decrease in fluorescence intensity.

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