Ferrous ion detection liquid as well as detection method and application thereof

Abstract

The invention belongs to the technical field of analytical chemistry, and relates to ferrous ion detection liquid as well as a detection method and application thereof. The technical problems that in the prior art, ferrous ions are detected by changing surface modifiers of silver nanoparticles, selectivity is insufficient, sensitivity is limited, steps are tedious, detection instruments are complex, and cost is high are solved. The invention provides a ferrous ion detection liquid which comprises tetramethyl benzidine, thiohydracrylic acid and silver nanoparticles, and the ratio of the tetramethyl benzidine to the thiohydracrylic acid to the silver nanoparticles is (1200-6000): (0.005-0.5): 99 according to the mass concentration. The pH value of the detection liquid is 4-6. The detection liquid is high in selectivity and high in sensitivity. The invention provides a preparation method of the ferrous ion detection liquid, and also provides a ferrous ion detection method, which is simple and convenient, is easy to detect, and can rapidly detect micromole-level metal ferrous ions. Meanwhile, the invention further provides application of the ferrous ion detection method in the sensing field and environment monitoring.

Description

Technical Field

[0001] This invention belongs to the field of analytical chemistry technology, specifically relating to a ferrous ion detection solution, its detection method, and its application. Background Technology

[0002] Iron ions are one of the essential trace elements for the human body and the most abundant transition metal element, widely distributed in various organs. Among these, ferrous ions are not only a key element in energy metabolism but also crucial for oxygen transport and storage in humans and other higher animals. Ferrous ion deficiency can lead to conditions such as diabetes, heart disease, and damage to organs like the liver and kidneys. On the other hand, excessive iron ions can also be harmful to human health due to increased free radicals. The Chinese government has set clear limits for metallic iron in water quality; the national standard GB 5749-2022 stipulates that the limit for metallic iron ions in drinking water shall not exceed 0.3 mg / L.

[0003] Currently, the main methods for determining ferrous ions include high-performance capillary electrophoresis, ion chromatography, X-ray fluorescence, electrothermal atomic absorption spectrometry, flame atomic absorption spectrometry, inductively coupled plasma mass spectrometry, anodic stripping voltammetry, reverse voltammetry, chemiluminescence, direct potentiometry, and fluorescence analysis. Although these methods have low detection limits and wide linear ranges, most require expensive and complex equipment, meaning they require specialized personnel to operate. Therefore, visual colorimetry has received widespread attention in recent years due to its low cost, ease of operation, intuitiveness, and lack of need for specialized personnel.

[0004] Colorimetric sensors based on metal nanoparticles have been widely used to monitor various analytes. These sensors rely on color changes resulting from the different dispersion and aggregation states of the metal nanoparticles. Among these, silver nanoparticles have attracted widespread attention due to their high molar extinction coefficient, significant color changes, and low fabrication cost. Current reports indicate that by altering the surface modifiers of silver nanoparticles, different metal ions, including Hg, can be measured. 2+ Cu 2+ Cr 3+ Co 2+ Ag + Pb 2+ ion.

[0005] Existing technologies detect ferrous ions (Fe) by modifying the surface modifiers of silver nanoparticles (AgNPs). 2 +) has the following shortcomings: (1) Insufficient selectivity, silver nanoparticle modifiers are susceptible to cross-contamination with other metal ions (such as Cu). 2 +、Hg 2 +, Fe 3(1) The combination of Fe and Fe can lead to false positive or false negative results; (2) The sensitivity is limited, and the detection limit (LOD) of some modified silver nanoparticles is still high, which is difficult to meet the requirements for trace Fe. 2 + detection requirements; (3) The modification steps are complicated, and some modification methods require multiple steps, which increases the detection cost and time.

[0006] Therefore, there is an urgent need to develop a method for detecting ferrous ions that does not require complex instruments, increases selectivity and sensitivity, and simplifies the operation steps. Summary of the Invention

[0007] 1. The problem to be solved

[0008] To address the shortcomings of existing ferrous ion detection technologies, which rely on modifying the surface modifiers of silver nanoparticles, the results are limited selectivity, sensitivity, and involve cumbersome modification steps, complex detection instruments, and high costs. This application provides a ferrous ion detection solution with high selectivity and sensitivity. It also provides a method for preparing the ferrous ion detection solution. Furthermore, this application provides a method for detecting ferrous ions. Moreover, it also provides an application of the ferrous ion detection method in environmental monitoring.

[0009] 2. Technical Solution

[0010] To achieve the above objectives, the provided technical solution is as follows:

[0011] A ferrous ion detection solution comprises tetramethylbenzidine, mercaptopropionic acid, and silver nanoparticles, wherein the ratio of tetramethylbenzidine, mercaptopropionic acid, and silver nanoparticles, calculated by mass concentration, is (1200–6000):(0.005–0.5):99; the pH value of the detection solution is 4–6.

[0012] Further, the concentration of the tetramethylbenzidine is 24 mg / mL to 120 mg / mL; and the concentration of the mercaptopropionic acid is 0.1 μg / mL to 10 μg / mL.

[0013] A method for preparing a ferrous ion detection solution includes the following steps:

[0014] Tetramethylbenzidine, mercaptopropionic acid, and silver nanoparticles were mixed to obtain a mixed solution. The pH of the mixed solution was adjusted to 4-6 to obtain a detection solution.

[0015] Preferably, the silver nanoparticles are prepared by mixing water, silver nitrate solution and sodium borohydride.

[0016] Preferably, the concentration of the hydrochloric acid solution is 0.05 mol / L to 0.5 mol / L.

[0017] A method for detecting ferrous ions, using the aforementioned ferrous ion detection solution, includes the following steps:

[0018] Add the ferrous ion sample solution to the detection solution, let it stand, and obtain the test solution;

[0019] The test solution was observed by visual colorimetry, and the absorbance ratio of the test solution was detected by dual-wavelength ultraviolet spectrophotometry to calculate the content of ferrous ions.

[0020] Preferably, the volume ratio of the detection solution to the ferrous ion sample solution is 1:1.

[0021] Furthermore, the settling time is 1 min to 10 min.

[0022] Furthermore, the two wavelengths are 525nm and 404nm, respectively, and the ratio of the absorbance is A. 525 / A 404 .

[0023] Furthermore, the volume of the ferrous ion sample solution to be tested is 5 μL to 500 μL.

[0024] Preferably, the concentration of the ferrous ion to be tested in the test solution is in the range of 0.1 μmol / L to 10 μmol / L.

[0025] Furthermore, the calculation steps include plotting a standard curve, adding ferrous ion standard solutions of different concentrations to the detection solution, allowing it to stand to obtain a standard series of sample solutions, measuring the absorbance ratio, and plotting a standard curve with the concentration of ferrous ions as the abscissa and the absorbance ratio as the ordinate.

[0026] Furthermore, the concentration range of ferrous ions in the standard series sample solutions is 0.1 μmol / L to 10 μmol / L.

[0027] An application of a ferrous ion detection method is disclosed, which is then applied to the fields of sensing and environmental monitoring.

[0028] 3. Beneficial effects

[0029] Compared with existing known technologies, the technical solution provided by this invention has the following beneficial effects:

[0030] (1) A ferrous ion detection solution of the present invention comprises tetramethylbenzidine, mercaptopropionic acid, and silver nanoparticles. The ratio of tetramethylbenzidine, mercaptopropionic acid, and silver nanoparticles, calculated by mass concentration, is (1200–6000):(0.005–0.5):99; the pH value of the detection solution is 4–6. By modifying the surface of silver nanoparticles with 3,3',5,5'-tetramethylbenzidine and 3-mercaptopropionic acid, coordination with ferrous ions is achieved, leading to aggregation of the silver nanoparticles and a color change. This solution is used to detect ferrous ions without the need for complex instruments, is simple and convenient, and can rapidly detect micromolar levels of metallic ferrous ions, achieving rapid and accurate detection of metallic ferrous ions. It has high selectivity and no response to non-target ions, such as ferric ions (Fe). 3+ ), zinc ions (Zn) 2+ ), manganese ions (Mn) 2+ Nickel ions (Ni) 2+ ), magnesium ions (Mg 2+ ), cobalt ions (Co) 2+ ), aluminum ions (Al) 3+ ) and copper ions (Cu 2+ It has high sensitivity, enabling the sensitive detection of 0.5 μM ferrous ions without any instruments.

[0031] (2) A method for preparing a ferrous ion detection solution according to the present invention involves mixing tetramethylbenzidine, mercaptopropionic acid, and silver nanoparticles to obtain a mixed solution, adjusting the pH of the mixed solution to 4-6, and obtaining a detection solution. The preparation method of this detection solution is simple, and the silver nanoparticle modification step is also simple.

[0032] (3) A method for detecting ferrous ions according to the present invention involves adding a sample solution of ferrous ions to be tested to the detection solution, allowing it to stand, and obtaining a test solution. The test solution is observed by visual colorimetry, and the absorbance ratio of the test solution is detected by dual-wavelength ultraviolet spectrophotometry to calculate the content of ferrous ions to be tested. The detection solution forms coordination with ferrous ions, causing silver nanoparticles to aggregate and undergo color change. The color change is positively correlated with the concentration of metallic ferrous ions. Visual colorimetry can semi-quantitatively detect ferrous ions. Combined with ultraviolet spectrophotometry, the absorbance ratio of the mixed solution at dual wavelengths is measured. Substituting this ratio into the ferrous ion concentration-absorbance ratio standard curve, the content of ferrous ions in the sample solution of ferrous ions to be tested can be quantitatively calculated. The detection method of this invention is based on aggregation reaction and can be applied to the naked-eye detection of ferrous ions. It requires no complex instruments, is simple and convenient, and can rapidly detect micromolar levels of ferrous ions, achieving rapid and accurate detection. It can sensitively detect 0.5 μM ferrous ions without any instruments. The detection method of this invention has the advantages of low cost, rapid detection, and good stability. It can be widely used in fields such as sensing and water treatment.

[0033] (4) Application of the ferrous ion detection method of the present invention: The ferrous ion detection method is applied to the fields of sensing and environmental monitoring. In the field of sensing, the detection of ferrous ions usually involves the development of sensors with high sensitivity and high selectivity. These sensors can be based on various principles, such as electrochemical sensors, optical sensors, fluorescence sensors, etc. These sensors can monitor changes in ferrous ion concentration in real time, providing important data support for environmental management and water quality control. In environmental monitoring, the concentration of ferrous ions can indicate whether water bodies are polluted. Attached Figure Description

[0034] Figure 1 This is a graph showing the color changes of the control group solution and the sample group solution in Example 1;

[0035] Figure 2 This is a graph showing the color changes of the control group solution and the sample group solution in Example 2;

[0036] Figure 3 This is a graph showing the color changes of the control group solution and the sample group solution in Example 3;

[0037] Figure 4 The image shows the color changes of the control group solution and the standard series sample solutions (mixtures of ferrous ions at different concentrations) in Example 4.

[0038] Figure 5 This is the standard curve of ferrous ion concentration-absorbance ratio in Example 4;

[0039] Figure 6 This is a color change graph of different metal ions in the detection solution in Example 5;

[0040] Figure 7 This is a graph showing the color changes of the control group solution and the sample group solution in Comparative Example 1;

[0041] Figure 8 The diagram shows the color changes of the sample solutions in Comparative Example 2, Comparative Example 3, and Example 1. Detailed Implementation

[0042] To further understand the content of this invention, the invention will be described in detail with reference to the embodiments.

[0043] The present application will be further described below with reference to specific embodiments.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0045] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0046] As used herein, the term “about” is used to provide for the flexibility and imprecision associated with a given term, measure, or value. Those skilled in the art can readily determine the degree of flexibility for a particular variable.

[0047] As used herein, the term “at least one of…” is intended to be synonymous with “one or more of…”. For example, “at least one of A, B, and C” explicitly includes only A, only B, only C, and combinations thereof.

[0048] Concentration, amount, and other numerical data may be presented in range format herein. It should be understood that such range format is used solely for convenience and brevity and should be flexibly interpreted to include not only the values ​​explicitly stated as the limits of the range, but also all individual values ​​or subranges encompassed within the range, as if each value and subrange were explicitly stated. For example, a range of values ​​from about 1 to about 4.5 should be interpreted to include not only the explicitly stated limits of 1 to 4.5, but also individual numbers (such as 2, 3, 4) and subranges (such as 1 to 3, 2 to 4, etc.). The same principle applies to ranges that describe only a single value, such as “less than about 4.5,” which should be interpreted to include all the aforementioned values ​​and ranges. Furthermore, this interpretation should apply regardless of the breadth of the range or characteristic described.

[0049] Example 1

[0050] This embodiment of a method for detecting ferrous ions includes the following steps:

[0051] S1. Preparation of silver nanoparticles: Add 1 mL of 0.02 mol / L silver nitrate solution to 199 mL of water and stir for 5 minutes. Then, add 10 mg of sodium borohydride to the solution to obtain silver nanoparticles (AgNPs) with a concentration of 0.01 mg / mL.

[0052] S2. Preparation of ferrous ion detection solution: 1 mL of 60 mg / mL 3,3',5,5'-tetramethylbenzidine (purchased from Aladdin Reagent Company), 1 mL of 1 μg / mL 3-mercaptopropionic acid (purchased from Aladdin Reagent Company) and 198 mL of 0.01 mg / mL silver nanoparticles were reacted for 1 hour to obtain a mixed solution;

[0053] The pH of the mixture was adjusted to 6 with 0.1 mol / L hydrochloric acid to obtain the detection solution;

[0054] S3. Preparation of sample solution: Pipette 500 μL of the above test solution into a 1.5 mL centrifuge tube, add 500 μL of 10 μmol / L ferrous metal ions to the test solution, shake well and let stand for 5 min to obtain the test solution, i.e., the sample solution. The concentration of ferrous metal ions in the sample solution is 5 μmol / L.

[0055] Preparation of control group solution: Pipette 500 μL of the above test solution into a 1.5 mL centrifuge tube, add 500 μL of ferrous ion-free deionized water to the test solution, shake well and let stand for 5 min to obtain the control group solution;

[0056] S4. Observe the color change of the solution using visual colorimetry. The color changes of the control group solution and the sample group solution are as follows: Figure 1 As shown, by direct visual observation, the solution of the sample group containing ferrous ions is darker in color than that of the control group.

[0057] Example 2

[0058] This embodiment of a method for detecting ferrous ions includes the following steps:

[0059] S1. Preparation of silver nanoparticles: Add 1 mL of 0.02 mol / L silver nitrate solution to 199 mL of water and stir for 5 minutes. Then, add 10 mg of sodium borohydride to the solution to obtain silver nanoparticles (AgNPs) with a concentration of 0.01 mg / mL.

[0060] S2. Preparation of ferrous ion detection solution: 1 mL of 24 mg / mL 3,3',5,5'-tetramethylbenzidine (purchased from Aladdin Reagent Company), 1 mL of 0.1 μg / mL 3-mercaptopropionic acid (purchased from Aladdin Reagent Company) and 198 mL of 0.01 mg / mL silver nanoparticles were reacted for 1 hour to obtain a mixed solution;

[0061] The pH of the mixture was adjusted to 4 with 0.1 mol / L hydrochloric acid to obtain the detection solution;

[0062] S3. Preparation of sample solution: Pipette 500 μL of the above test solution into a 1.5 mL centrifuge tube, add 500 μL of 10 μmol / L ferrous metal ions to the test solution, shake well and let stand for 5 min to obtain the test solution, i.e., the sample solution. The concentration of ferrous metal ions in the sample solution is 5 μmol / L.

[0063] Preparation of control group solution: Pipette 500 μL of the above test solution into a 1.5 mL centrifuge tube, add 500 μL of ferrous ion-free deionized water to the test solution, shake well and let stand for 5 min to obtain the control group solution;

[0064] S4. Observe the color change of the solution using visual colorimetry. The color changes of the control group solution and the sample group solution are as follows: Figure 2 As shown, by direct visual observation, the solution of the sample group containing ferrous ions is darker in color than that of the control group.

[0065] Example 3

[0066] This embodiment of a method for detecting ferrous ions includes the following steps:

[0067] S1. Preparation of silver nanoparticles: Add 1 mL of 0.02 mol / L silver nitrate solution to 199 mL of water and stir for 5 minutes. Then, add 10 mg of sodium borohydride to the solution to obtain silver nanoparticles (AgNPs) with a concentration of 0.01 mg / mL.

[0068] S2. Preparation of ferrous ion detection solution: 1 mL of 120 mg / mL 3,3',5,5'-tetramethylbenzidine (purchased from Aladdin Reagent Company), 1 mL of 10 μg / mL 3-mercaptopropionic acid (purchased from Aladdin Reagent Company) and 198 mL of 0.01 mg / mL silver nanoparticles were reacted for 1 hour to obtain a mixed solution;

[0069] The pH of the mixture was adjusted to 5 with 0.1 mol / L hydrochloric acid to obtain the detection solution;

[0070] S3. Preparation of sample solution: Pipette 500 μL of the above test solution into a 1.5 mL centrifuge tube, add 500 μL of 10 μmol / L ferrous metal ions to the test solution, shake well and let stand for 5 min to obtain the test solution, i.e., the sample solution. The concentration of ferrous metal ions in the sample solution is 5 μmol / L.

[0071] Preparation of control group solution: Pipette 500 μL of the above test solution into a 1.5 mL centrifuge tube, add 500 μL of ferrous ion-free deionized water to the test solution, shake well and let stand for 5 min to obtain the control group solution;

[0072] S4. Observe the color change of the solution using visual colorimetry. The color changes of the control group solution and the sample group solution are as follows: Figure 3 As shown, by direct visual observation, the solution of the sample group containing ferrous ions is darker in color than that of the control group.

[0073] From Examples 1 to 3, and Figures 1-3It is known that the concentration of the added 3,3',5,5'-tetramethylbenzidine is 24 mg / mL to 120 mg / mL, the concentration of 3-mercaptopropionic acid is 0.1 μg / mL to 10 μg / mL, and the concentration of silver nanoparticles is 0.01 mg / mL. The final detection solution can react with ferrous metal ions to produce a color change, which can be used to detect ferrous ions.

[0074] Example 4

[0075] This embodiment of the ferrous ion detection method includes the following steps for standard curve plotting:

[0076] The preparation of silver nanoparticles and detection solution is the same as steps S1 and S2 in Example 1;

[0077] Plotting the standard curve:

[0078] Preparation of standard series sample solutions: Pipette 500 μL of the test solution into a 1.5 mL centrifuge tube, add 500 μL of ferrous ion standard solutions of different concentrations to the test solution, shake well and let stand for 5 min to obtain test solutions of different concentrations, i.e., standard series sample solutions. The ferrous ion concentrations in the standard series sample solutions are 0.1 μmol / L, 0.2 μmol / L, 0.5 μmol / L, 0.8 μmol / L, 1.0 μmol / L, 2.0 μmol / L, 5.0 μmol / L and 10.0 μmol / L, respectively.

[0079] The absorbance ratio of a series of standard sample solutions was determined using dual-wavelength ultraviolet spectrophotometry, with wavelengths of 525 nm and 404 nm. The absorbance ratio was calculated as A. 525 / A 404 A 525 A represents the absorbance value of the standard series sample solutions at a wavelength of 525 nm. 404 This indicates the absorbance value of the standard series sample solutions at a wavelength of 404 nm;

[0080] A standard curve of ferrous ion concentration versus absorbance ratio was plotted with the concentration of ferrous ions in the standard series sample solutions as the x-axis and the absorbance ratio as the y-axis, yielding the linear equation Y = 0.0832X + 0.0522. Figure 5 As shown, the concentration of ferrous ions is linearly related to the absorbance ratio;

[0081] Preparation of control group solution: Pipette 500 μL of the above test solution into a 1.5 mL centrifuge tube, add 500 μL of ferrous ion-free deionized water to the test solution, shake well and let stand for 5 min to obtain the control group solution;

[0082] Visual colorimetry: The color change of the solution is observed visually. The color changes of the control group solution and the standard series of sample solutions are as follows: Figure 4 As shown, as the concentration of ferrous ions in the standard series sample solutions increases, the color of the standard series sample solutions deepens, eventually reaching the level that can be directly observed with the naked eye.

[0083] In summary, by Figure 4 It is known that when the concentration of ferrous ions in the test solution is greater than 0.5 μmol / L, the color of the test solution changes from yellow to brownish-red, which can be directly observed with the naked eye. Therefore, when the concentration of ferrous ions in the test solution is in the range of 0.1 μmol / L to 10 μmol / L, the ratio of ferrous ion concentration to absorbance shows a linear relationship. This linear relationship can be used to quantitatively detect the specific concentration of ferrous ions in the sample solution.

[0084] Example 5

[0085] This embodiment of a method for detecting ferrous ions includes the following steps:

[0086] Using the detection solution prepared in Example 1, the sample group solution was prepared as follows: 500 μL of the detection solution was pipetted into a 1.5 mL centrifuge tube, and ferrous ions (Fe2+) at a concentration of 5 μmol / L were added sequentially to the detection solution. 2+ ), iron ions (Fe) 3+ ), zinc ions (Zn) 2+ ), manganese ions (Mn) 2+ Nickel ions (Ni) 2+ ), magnesium ions (Mg 2+ ), cobalt ions (Co) 2+ ), aluminum ions (Al) 3+ ) and copper ions (Cu 2+ After shaking and mixing, let stand for 5 minutes to obtain test solutions of different metal ions, i.e., sample group solutions of different metal ions.

[0087] Preparation of control group solution: Pipette 500 μL of the above test solution into a 1.5 mL centrifuge tube, add 500 μL of ferrous ion-free deionized water to the test solution, shake well and let stand for 5 min to obtain the control group solution;

[0088] Visual colorimetry: Color changes are observed visually. The color changes of the control group solution and the sample group solutions with different metal ions are shown below. Figure 6 As shown, among different metal ions, only ferrous ions can cause a color change in the detection solution of this experiment; other metals do not cause a color change. This indicates that the detection solution of this application has no response to non-target ions and exhibits high selectivity.

[0089] Example 6

[0090] This embodiment of a ferrous ion detection method, including a spiked recovery experiment, comprises the following steps:

[0091] The detection solution prepared in Example 1 was used;

[0092] Preparation of spiked recovery solution: Ferrous ions were added to tap water and lake water respectively, so that the final concentrations in the solution were 1 μmol / L, 2 μmol / L, and 10 μmol / L;

[0093] Sample solution preparation: Pipette 500 μL of the test solution into a 1.5 mL centrifuge tube, add 500 μL of the above spiked recovery solution to the test solution, shake well and let stand for 5 min;

[0094] The ratio of the absorbance of the sample solution at 525 nm and 404 nm was measured by dual-wavelength ultraviolet spectrophotometry, i.e., the absorbance ratio = A. 525 / A 404 Substituting the ratio of absorbance into the linear equation of Example 4, the spike recovery rates of different solutions were calculated, as shown in Table 1.

[0095] Table 1 Spiked Recovery Test Data

[0096]

[0097] For spiked recovery tests on trace or low-concentration samples, the recovery rate needs to be 70%–130% and the precision (RSD) ≤15%. As shown in Table 1, the recovery rate and precision both meet the requirements, and the detection method of this application is accurate and reliable.

[0098] Comparative Example 1

[0099] This comparative example illustrates a method for detecting ferrous ions, comprising the following steps:

[0100] Step 1, Preparation of silver nanoparticles: Add 1 mL of 0.02 mol / L silver nitrate solution to 199 mL of water and stir for 5 minutes. Then, add 10 mg of sodium borohydride to the solution to obtain silver nanoparticles (AgNPs) with a concentration of 0.01 mg / mL.

[0101] Step 2, Preparation of ferrous ion detection solution: 1 mL of 0.24 mg / mL 3,3',5,5'-tetramethylbenzidine (purchased from Aladdin Reagent Company), 1 mL of 0.1 μg / mL 3-mercaptopropionic acid (purchased from Aladdin Reagent Company) and 198 mL of 0.01 mg / mL silver nanoparticles were reacted for 1 hour to obtain a mixed solution;

[0102] The pH of the mixture was adjusted to 5 with 0.1 mol / L hydrochloric acid to obtain the detection solution;

[0103] Step 3, Sample group solution preparation: Use a pipette to pipette 500 μL of the above test solution into a 1.5 mL centrifuge tube, add 500 μL of ferrous metal ions with a concentration of 10 μmol / L to the test solution, shake well and let stand for 5 min to obtain the test solution, i.e., the sample group solution, in which the concentration of ferrous metal ions is 5 μmol / L.

[0104] Preparation of control group solution: Pipette 500 μL of the above test solution into a 1.5 mL centrifuge tube, add 500 μL of ferrous ion-free deionized water to the test solution, shake well and let stand for 5 min to obtain the control group solution;

[0105] Step 4: Observe the color change of the solution using visual colorimetry. The color changes of the control group solution and the sample group solution are as follows: Figure 7 As shown, by direct visual observation, the color of the solution containing ferrous ions was not significantly different from that of the control group.

[0106] As shown in Comparative Example 1, when the content of 3,3',5,5'-tetramethylbenzidine is too low, 3,3',5,5'-tetramethylbenzidine cannot modify the surface of silver nanoparticles, resulting in insufficient sensitivity of the detection solution and inability to produce a visible reaction to ferrous ions.

[0107] Comparative Example 2

[0108] This comparative example illustrates a method for detecting ferrous ions, comprising the following steps:

[0109] Step 1, Preparation of silver nanoparticles: Add 1 mL of 0.02 mol / L silver nitrate solution to 199 mL of water and stir for 5 minutes. Then, add 10 mg of sodium borohydride to the solution to obtain silver nanoparticles (AgNPs) with a concentration of 0.01 mg / mL.

[0110] Step 2, Preparation of ferrous ion detection solution: 1 mL of 60 mg / mL 3,3',5,5'-tetramethylbenzidine (purchased from Aladdin Reagent Company) was reacted with 198 mL of 0.01 mg / mL silver nanoparticles for 1 hour, and the pH was adjusted to 5 with 0.1 mol / L hydrochloric acid to obtain control solution 1;

[0111] Step 3, Preparation of sample solution: Use a pipette to transfer 500 μL of control solution 1 into a 1.5 mL centrifuge tube, add 500 μL of ferrous metal ions with a concentration of 10 μmol / L to control solution 1, shake well and let stand for 5 min to obtain the test solution, i.e., the sample solution. The concentration of ferrous metal ions in the sample solution is 5 μmol / L.

[0112] Step 4: Observe the color change of the solution using visual colorimetry, such as... Figure 8 As shown.

[0113] Comparative Example 3

[0114] This comparative example illustrates a method for detecting ferrous ions, comprising the following steps:

[0115] Step 1, Preparation of silver nanoparticles: Add 1 mL of 0.02 mol / L silver nitrate solution to 199 mL of water and stir for 5 minutes. Then, add 10 mg of sodium borohydride to the solution to obtain silver nanoparticles (AgNPs) with a concentration of 0.01 mg / mL.

[0116] Step 2, Preparation of ferrous ion detection solution: 1 mL of 10 μg / mL 3-mercaptopropionic acid (purchased from Aladdin Reagent Company) was reacted with 198 mL of 0.01 mg / mL silver nanoparticles for 1 hour, and the pH was adjusted to 5 with 0.1 mol / L hydrochloric acid to obtain control solution 2.

[0117] Step 3, Preparation of sample solution: Use a pipette to transfer 500 μL of control solution 2 into a 1.5 mL centrifuge tube, add 500 μL of 10 μmol / L ferrous metal ions to control solution 2, shake well and let stand for 5 min to obtain the test solution, i.e., the sample solution. The concentration of ferrous metal ions in the sample solution is 5 μmol / L.

[0118] Step 4: Observe the color change of the solution using visual colorimetry, such as... Figure 8 As shown.

[0119] Comparative Examples 2 and 3, Example 1 and Figure 8 It can be seen that the detection solution prepared in Example 1 turns brownish-red after the addition of ferrous ions; while control solutions 1 and 2 do not change color after the addition of ferrous ions, and neither can achieve the desired effect on Fe. 2+ The detection was negative because control solution 1, obtained by mixing silver nanoparticles with 3,3',5,5'-tetramethylbenzidine, and control solution 2, obtained by mixing silver nanoparticles with 3-mercaptopropionic acid, could not form coordination with ferrous ions and thus did not change color.

[0120] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications, improvements, and substitutions without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A ferrous ion detection solution, characterized by: The detection solution comprises tetramethylbenzidine, mercaptopropionic acid and silver nanoparticles, and the mass concentration ratio of tetramethylbenzidine, mercaptopropionic acid and silver nanoparticles is (1200-6000):(0.005-0.5):99; the pH value of the detection solution is 4-6.

2. The ferrous ion detection solution according to claim 1, characterized in that: The concentration of tetramethylbenzidine is 24 mg / mL-120 mg / mL; and the concentration of mercaptopropionic acid is 0.1 μg / mL-10 μg / mL.

3. A method for the preparation of a ferrous ion detection solution according to any one of claims 1 or 2, characterized in that: The method comprises the following steps: tetramethylbenzidine, mercaptopropionic acid and silver nanoparticles are mixed to obtain a mixed solution, and the pH value of the mixed solution is adjusted to 4-6 to obtain a detection solution.

4. A method for detecting ferrous ions, characterized by: The method for detecting ferrous ions using the detection solution of any one of claims 1 or 2 comprises the following steps: A sample solution of the ferrous ions to be detected is added to the detection solution, and the mixture is allowed to stand to obtain a sample solution to be detected; The sample solution to be detected is observed by visual colorimetry, and the absorbance ratio of the sample solution to be detected is detected by dual-wavelength ultraviolet spectrophotometry to calculate the content of the ferrous ions to be detected.

5. The method for detecting ferrous ions according to claim 4, characterized in that: The standing time is 1 min-10 min.

6. The method of claim 4, wherein: The dual wavelengths are 525 nm and 404 nm, respectively, and the ratio of the absorbances is A 525 / A 404 .

7. The method of claim 4, wherein the method is used for detecting ferrous ions. The volume of the sample solution of the ferrous ions to be detected is 5 μL-500 μL.

8. A method for detecting ferrous ions according to any one of claims 4-7, characterized in that: The calculation step comprises drawing a standard curve, adding standard solutions of ferrous ions with different concentrations to the detection solution, allowing the mixture to stand to obtain a series of standard sample solutions, measuring the absorbance ratio, taking the concentration of the ferrous ions as the abscissa and the absorbance ratio as the ordinate to draw a standard curve.

9. The method of claim 8, wherein: The concentration of the ferrous ions in the series of standard sample solutions ranges from 0.1 μmol / L to 10 μmol / L.

10. Use of a method for detecting ferrous ions, characterized in that, The method of any one of claims 4-9 is applied to the fields of sensing and environmental monitoring.

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