Recognition of Cr(VI) by a 2-amino-5-substituted-1,3,4-oxadiazole

Abstract

A 2-amino-5-substituted-1,3,4-oxadiazole is used to identify Cr(VI). A test solution is prepared using the 2-amino-5-substituted-1,3,4-oxadiazole. An anionic solution is added to the test solution, and Cr(VI) is identified by naked-eye observation and UV-visible absorption spectroscopy. The method demonstrates excellent selectivity for Cr(VI) identification, with no interference from other ions, enabling better detection of Cr(VI) in the environment.

Description

Technical Field

[0001] The invention belongs to the field of chemical synthesis and anion detection, and relates to 2-amino-5-substituted-1,3,4-oxadiazole for identifying Cr(VI). Background Art

[0002] Heterocyclic compounds are a key area of ​​pharmaceutical research. The simultaneous introduction of two or more heterocyclic active centers into a molecule can improve the compound's biological activity, resulting in compounds with enhanced activity and higher application value. 1,3,4-oxadiazole heterocyclic compounds are gaining increasing attention due to their unique and broad range of biological activities, including antibacterial, antifungal, antitumor, and anti-inflammatory properties. Furthermore, the heterocyclic rings are linked by electron-donating elements, which enhance the affinity between receptors and ligands, thereby improving biological activity.

[0003] In recent years, the development of molecular receptors for detecting metal ions has become a growing and attractive research area, as they play a significant role in nearly every field. With the development of human society, industrial water pollution has become increasingly severe, with heavy metals being one of the main sources of water pollution. Chromium, a typical heavy metal found in wastewater, primarily originates from industries such as electroplating, photosensitive materials, and leather. Chromium is one of the most widely distributed heavy metal elements in the Earth's crust, primarily forming chromite, with common valence states of zero, trivalent, and hexavalent. Chromium in natural waters primarily exists in the valence states of chromium (III) and chromium (VI), with chromium (VI) being at least a hundred times more toxic than chromium (III). With the continuous development of industry, large amounts of chromium-containing waste are generated during production processes, directly harming aquatic products and human health. Therefore, research on methods for detecting chromium (VI) in water is of great practical significance. Therefore, its detection is essential in various fields. Summary of the Invention

[0004] In order to overcome the disadvantages of some of the above-mentioned prior arts, such as low sensitivity to adsorbed anions, a chromophore group is introduced to distinguish ions by color change by the naked eye. The object of the present invention is to provide a 2-amino-5-substituted-1,3,4-oxadiazole for the recognition of Cr(VI).

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] Furthermore, a method for detecting iron ions comprises the following steps:

[0007] Step 1) preparing a 2-amino-5-substituted-1,3,4-oxadiazole solution to obtain a test solution;

[0008] Step 2) prepare anion solution:

[0009] Mixing the anion solution and the test solution to obtain a test solution, observing the color change of the test solution, and identifying whether Cr(VI) is present in the anion solution based on the color change of the test solution;

[0010] Furthermore, 2-amino-5-substituted-1,3,4-oxadiazole is as shown in formula (1)

[0011]

[0012] Wherein, R is -H, 4-CH3, 4-OCH3, 4-OH, 4-NO2, 4-Cl, 4-F, 4-Br, 2-CH3, 2-OH, 2-NO2, 3-NO2, 3-Cl, 3-Br

[0013] Furthermore, the Cr(VI) is Cr2O7 2- ions and CrO4 2- ion.

[0014] Further, the anion is C6H5COO - ,HSO3 - ,F - ,CH3COO - ,Br - ,Cr2O7 2- ,CO3 2- ,SO4 2- ,S 2- ,S2O8 2- ,C2O4 2- ,SiO3 2- ,H2PO4 - ,I - ,CrO4 2- ,Cl - ,SCN - .

[0015] Furthermore, when the anion solution and the test solution are mixed, the concentration of the anion solution is 1×10 -2 mol / L; the concentration of the test solution is 1×10 -4 mol / L.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The invention provides a 2-amino-5-substituted-1,3,4-oxadiazole for recognizing Cr(VI), wherein the active -C=N- and -CO- groups in the 2-amino-5-substituted-oxadiazole are combined with different metal ions.

[0018] A 2-amino-5-substituted-1,3,4-oxadiazole was used to identify Cr(VI). An anion solution was added to the test solution, and Cr(VI) was identified by "naked eye" observation and UV-visible absorption spectroscopy. It was found that it had good selectivity for Cr(VI), and the selectivity was not interfered by other ions. In addition, 2-amino-5-substituted-1,3,4-oxadiazole can better detect Cr(VI) in the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Add Cr2O7 to 2-amino-5-phenyl-1,3,4-oxadiazole 2- UV-visible absorption spectrum of ions;

[0020] Figure 2 Add CrO4 to 2-amino-5-phenyl-1,3,4-oxadiazole 2- UV-visible absorption spectrum of ions;

[0021] Figure 3 2-amino-5-phenyl-1,3,4-oxadiazole to Cr2O7 2- Specific recognition of ions;

[0022] Figure 4 2-amino-5-phenyl-1,3,4-oxadiazole to CrO4 2- Specific recognition of ions;

[0023] Figure 5 The effect of pH on the addition of anions to 2-amino-5-phenyl-1,3,4-oxadiazole;

[0024] Figure 6 The effect of time on the addition of anions to 2-amino-5-phenyl-1,3,4-oxadiazole;

[0025] Figure 7 2-amino-5-phenyl-1,3,4-oxadiazole to Cr2O7 2- quantitative testing of

[0026] Figure 8 2-amino-5-phenyl-1,3,4-oxadiazole to CrO4 2- quantitative testing of DETAILED DESCRIPTION

[0027] The present invention is described in further detail below with reference to the accompanying drawings:

[0028] Example 12-amino-5-phenyl-1,3,4-oxadiazole to Cr2O7 2- "Naked eye" recognition

[0029] 2-Amino-5-phenyl-1,3,4-oxadiazole was dissolved in CH3OH:H2O=5:5 and prepared into a concentration of 1×10 - 4 mol / L of the test solution, ultrasonic. C6H5COONa, NaHSO3, NaF, CH3COONa, NaBr, Na2Cr2O7·2H2O, Na2CO3, Na2SO4, Na2S, Na2C2O4, Na2SiO3·9H2O, NaH2PO4·2H2O, NaI, NaCl, KSCN were prepared with ultrapure water to 1×10 -2 mol / L anion solution for later use. Use a pipette to accurately measure 3mL of 2-amino-5-phenyl-1,3,4-oxadiazole test solution into 17 sample tubes, set aside one sample tube as a blank control sample, and use a pipette to add 30μl of the above 16 test anion solutions to the remaining test solution. Ultrasonic oscillate these 17 groups of samples, let them stand to disperse evenly, and then observe the color change of 2-amino-5-phenyl-1,3,4-oxadiazole. When adding Cr2O7 2- After the addition of ions, the solution turns from colorless to yellow, and the color of the solution with other anions is consistent with the color of the test solution of 2-amino-5-phenyl-1,3,4-oxadiazole. 2- ion.

[0030] Example 22-amino-5-phenyl-1,3,4-oxadiazole to CrO4 2- "Naked eye" recognition

[0031] 2-Amino-5-phenyl-1,3,4-oxadiazole was dissolved in CH3OH:H2O=5:5 and prepared into a concentration of 1×10 - 4 mol / L of the test solution, ultrasonic. C6H5COONa, NaHSO3, NaF, CH3COONa, NaBr, Na2CO3, Na2SO4, Na2S, Na2C2O4, Na2SiO3·9H2O, NaH2PO4·2H2O, NaI, NaCl, K2CrO4, KSCN were prepared into 1×10 - 2 mol / L anion solution for later use. Use a pipette to accurately measure 3mL of 2-amino-5-phenyl-1,3,4-oxadiazole test solution into 17 sample tubes, set aside one sample tube as a blank control sample, and use a pipette to add 30μl of the above 16 test anion solutions to the remaining test solution. Ultrasonic oscillate these 17 groups of samples, let them stand to disperse evenly, and then observe the color change of 2-amino-5-phenyl-1,3,4-oxadiazole. When adding CrO4 2-After the addition of ions, the solution turns from colorless to yellow, and the color of the solution with other anions is consistent with the color of the test solution of 2-amino-5-phenyl-1,3,4-oxadiazole. 2- ion.

[0032] Example 32-amino-5-phenyl-1,3,4-oxadiazole to Cr2O7 2- Selective detection

[0033] 2-Amino-5-phenyl-1,3,4-oxadiazole was dissolved in CH3OH:H2O=5:5 and prepared into a concentration of 1×10 - 4 mol / L of the test solution, ultrasonic. C6H5COONa, NaHSO3, NaF, CH3COONa, NaBr, Na2Cr2O7·2H2O, Na2CO3, Na2SO4, Na2S, Na2C2O4, Na2SiO3·9H2O, NaH2PO4·2H2O, NaI, NaCl, KSCN were prepared with ultrapure water to 1×10 -2 mol / L anion solution for later use. Use a pipette to accurately measure 3mL of the test solution of 2-amino-5-phenyl-1,3,4-oxadiazole into 17 sample tubes, set aside one sample tube as a blank control sample, and use a pipette to add 30μl of the above 16 test anion solutions to the remaining 16 test solutions. Ultrasonic oscillate these 17 groups of samples and let them stand to disperse evenly. Then test the UV-visible absorption spectrum of 2-amino-5-phenyl-1,3,4-oxadiazole. Figure 1 It can be seen that adding Cr2O7 2- The absorption intensity at 298 nm was enhanced, and a new absorption peak appeared at 361 nm. The absorption peaks of the raw materials remained consistent with those of the addition of other anions. This shows that 2-amino-5-phenyl-1,3,4-oxadiazole can selectively recognize Cr2O7 2- ions. Example 42-amino-5-phenyl-1,3,4-oxadiazole to CrO4 2- Selective detection

[0034] 2-Amino-5-phenyl-1,3,4-oxadiazole was dissolved in CH3OH:H2O=5:5 and prepared into a concentration of 1×10 - 4 mol / L of the test solution, ultrasonic. C6H5COONa, NaHSO3, NaF, CH3COONa, NaBr, Na2CO3, Na2SO4, Na2S, Na2C2O4, Na2SiO3·9H2O, NaH2PO4·2H2O, NaI, NaCl, K2CrO4, KSCN were prepared into 1×10- 2 mol / L anion solution for later use. Use a pipette to accurately measure 3mL of the test solution of 2-amino-5-phenyl-1,3,4-oxadiazole into 17 sample tubes, set aside one sample tube as a blank control sample, and use a pipette to add 30μl of the above 16 test anion solutions to the remaining 16 test solutions. Ultrasonic oscillate these 17 groups of samples and let them stand to disperse evenly. Then test the UV-visible absorption spectrum of 2-amino-5-phenyl-1,3,4-oxadiazole. Figure 2 It can be seen that adding Cr2O7 2- The absorption intensity at 298 nm was enhanced, and a new absorption peak appeared at 374 nm. The absorption peaks of the raw materials remained consistent with those of the addition of other anions. This shows that 2-amino-5-phenyl-1,3,4-oxadiazole can selectively recognize Cr2O7 2- Example 52-amino-5-phenyl-1,3,4-oxadiazole to Cr2O7 2- Specific recognition of

[0035] 2-Amino-5-phenyl-1,3,4-oxadiazole was dissolved in CH3OH:H2O=5:5 and prepared into a concentration of 1×10 - 4 mol / L of the test solution, ultrasonic. C6H5COONa, NaHSO3, NaF, CH3COONa, NaBr, Na2Cr2O7·2H2O, Na2CO3, Na2SO4, Na2S, Na2C2O4, Na2SiO3·9H2O, NaH2PO4·2H2O, NaI, NaCl, KSCN were prepared with ultrapure water to 1×10 -2 mol / L anion solution for later use. Use a pipette to accurately measure 3 mL of the probe 2-amino-5-phenyl-1,3,4-oxadiazole test solution into 17 sample tubes, set aside one group as a blank control sample, and use a pipette to add 30 μL of the prepared anion solution to the remaining 16 2-amino-5-phenyl-1,3,4-oxadiazole test solutions, and then add 30 μL of the prepared anion solution to the sample tubes. 2- ions, all the solution samples were ultrasonically vibrated, allowed to stand to disperse evenly, and then their UV spectra were measured. Figure 3 It can be seen that when the 16 anion solutions were added dropwise, the absorbance was close to that of the 2-amino-5-phenyl-1,3,4-oxadiazole test solution, and only Cr2O7 2- The absorption intensity of ions increases, which indicates that the 2-amino-5-phenyl-1,3,4-oxadiazole test solution can selectively identify Cr2O7 2-ions; when the anion solution is added to 2-amino-5-phenyl-1,3,4-oxadiazole, Cr2O7 is added again 2- Ionic solution, as can be seen from the figure, the absorption intensity is significantly enhanced. This shows that 2-amino-5-phenyl-1,3,4-oxadiazole has a strong affinity for Cr2O7 2- The ions have specific recognition capabilities, and other anions have no interference and can be used in actual detection.

[0036] Example 62-amino-5-phenyl-1,3,4-oxadiazole to CrO4 2- Specific recognition of

[0037] 2-Amino-5-phenyl-1,3,4-oxadiazole was dissolved in CH3OH:H2O=5:5 and prepared into a concentration of 1×10 - 4 mol / L of the test solution, ultrasonic. C6H5COONa, NaHSO3, NaF, CH3COONa, NaBr, Na2CO3, Na2SO4, Na2S, Na2C2O4, Na2SiO3·9H2O, NaH2PO4·2H2O, NaI, NaCl, K2CrO4, KSCN were prepared into 1×10 - 2 mol / L anion solution for later use. Use a pipette to accurately measure 3 mL of the probe 2-amino-5-phenyl-1,3,4-oxadiazole test solution into 17 sample tubes, set aside one group as a blank control sample, and use a pipette to add 30 μL of the prepared anion solution to the remaining 16 2-amino-5-phenyl-1,3,4-oxadiazole test solutions, and then add 30 μL of the prepared anion solution to the sample tubes. 2- ions, all the solution samples were ultrasonically vibrated, allowed to stand to disperse evenly, and then their UV spectra were measured. Figure 4 It can be seen that when the 16 anion solutions are added dropwise, the absorbance is close to that of the 2-amino-5-phenyl-1,3,4-oxadiazole test solution, and only CrO4 2- The absorption intensity of the ion is enhanced, which shows that the 2-amino-5-phenyl-1,3,4-oxadiazole test solution can selectively identify CrO4 2- ions; when the anion solution is added to 2-amino-5-phenyl-1,3,4-oxadiazole, CrO4 is added again 2- Ionic solution, as can be seen from the figure, the absorption intensity is significantly enhanced. This shows that 2-amino-5-phenyl-1,3,4-oxadiazole has a strong affinity for CrO4 2- The ions have specific recognition capabilities, and other anions have no interference and can be used in actual detection.

[0038] Example 7 Study on the Application of 2-Amino-5-phenyl-1,3,4-oxadiazole at Different pH Values

[0039] In order to verify the practical application ability of 2-amino-5-phenyl-1,3,4-oxadiazole at different pH, the absorption intensity of 2-amino-5-phenyl-1,3,4-oxadiazole at 291nm in different pH environments was investigated. Figure 5 As shown in the figure, in different pH environments, the absorption intensity of 2-amino-5-phenyl-1,3,4-oxadiazole remains basically constant at pH = 2.0-12.0. 2- and CrO4 2- After that, the pH value remains basically constant at pH = 2.0-12.0. 2- and CrO4 2- ions are detected, but under acidic conditions CrO4 2- Transformation of Cr2O7 2- , under alkaline conditions Cr2O7 2- Transformed into CrO4 2- Therefore, the results show that Cr2O7 can be effectively identified at pH=7. 2- and CrO4 2- ion.

[0040] Example 8 Kinetic Study of 2-Amino-5-phenyl-1,3,4-oxadiazole

[0041] In order to verify the practical application ability of 2-amino-5-phenyl-1,3,4-oxadiazole, the change of the absorption intensity of 2-amino-5-phenyl-1,3,4-oxadiazole with time during the detection process was studied at room temperature. Figure 6 As shown, the absorption intensity of 2-amino-5-phenyl-1,3,4-oxadiazole at 291nm weakened within 0-80min. 2- and CrO4 2- After that, the absorption intensity weakens within 0-80min. However, within the range of 0-80min, Cr2O7 2- and CrO4 2- ions are detected.

[0042] Example 92-amino-5-phenyl-1,3,4-oxadiazole to Cr2O7 2- Quantitative testing

[0043] Identification ion Cr2O7 2- The results of the influence of the concentration of the probe on the UV performance are as follows Figure 7 As the concentration of the identified ions increases proportionally, when the Cr2O7 2-When the concentration in the solution is , the absorption intensity of the system at 291nm is weakened. And we can see from the illustration that when Cr2O7 2- When the amount drops to 0.4eq, the absorption intensity drops relatively slowly, which shows that Cr2O7 2- The combination ratio of 2-amino-5-phenyl-1,3,4-oxadiazole is 2:3.

[0044] Example 102-amino-5-phenyl-1,3,4-oxadiazole to CrO4 2- Quantitative testing

[0045] Identification ion CrO4 2- The results of the influence of the concentration of the probe on the UV performance are as follows Figure 8 As the concentration of identified ions increases proportionally, when the CrO4 2- When the concentration in the solution is , the absorption intensity of the system at 370nm is enhanced. And we can see from the illustration that when CrO4 2- When the amount increases to 0.4eq, the absorption intensity increases slowly, which shows that CrO4 2- The combination ratio of 2-amino-5-phenyl-1,3,4-oxadiazole is 2:3.

[0046] The present invention discloses a method for identifying Cr(VI) using a 2-amino-5-substituted-1,3,4-oxadiazole. An anion solution is added to a test liquid, and Cr(VI) is identified by "naked eye" observation and ultraviolet-visible absorption spectroscopy. It is found that the method can identify Cr(VI) with the "naked eye" and has good selectivity. The selectivity is not interfered by other ions, and the method can better detect Cr(VI) in the environment.

Claims

1. A method for identifying Cr(VI) by 2-amino-5-substituted-1,3,4-oxadiazole, characterized in that: The steps include: Step 1) preparing a 2-amino-5-substituted-1,3,4-oxadiazole solution to obtain a test solution; Step 2) prepare anion solution: Mixing the anion solution and the test solution to obtain a test solution, observing the color change of the test solution, and identifying whether Cr(VI) is present in the anion solution based on the color change of the test solution; 2-amino-5-substituted-1,3,4-oxadiazole as formula (1): Among them, R is -H, 4-CH3, 4-OCH3, 4-OH, 4-NO2, 4-Cl, 4-F, 4-Br, 2-CH3, 2-OH, 2-NO2, 3-NO2, 3-Cl, 3-Br.

2. The method for identifying Cr(VI) by 2-amino-5-substituted-1,3,4-oxadiazole according to claim 1, wherein: The Cr(VI) is Cr2O7 2- ions and CrO4 2- ion.

3. The method for identifying Cr(VI) by using 2-amino-5-substituted-1,3,4-oxadiazole according to claim 1, wherein: The anion is C6H5COO - ,HSO3 - ,F - ,CH3COO - ,Br - ,Cr2O7 2- ,CO3 2- ,SO4 2- ,S 2- ,S2O8 2- ,C2O4 2- ,SiO3 2- ,H2PO4 - ,I - ,CrO4 2- ,Cl - ,SCN - .

4. The method for recognizing Cr(VI) by 2-amino-5-substituted-1,3,4-oxadiazole according to claim 1, characterized in that: When the anion solution and the test solution are mixed, the concentration of the anion solution is 1×10 -2 mol / L; the concentration of the test solution is 1×10 -4 mol / L.

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