A method for detecting sodium nitrite in an aqueous solution using Cu 72 Pt 28 Method for detecting concentration of sodium nitrite in aqueous solution by alloy nanocrystals
By modifying the electrode with Cu72Pt28 alloy nanocrystals and combining linear voltammetric scanning and chronoamperometric current density dual testing, the problems of small detection range, complex pretreatment and large error in electrochemical catalytic detection of nitrite concentration were solved, and high accuracy and anti-interference sodium nitrite detection were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HARBIN UNIV OF SCI & TECH
- Filing Date
- 2023-09-27
- Publication Date
- 2026-05-19
AI Technical Summary
Existing electrochemical catalytic methods for detecting nitrite concentration have problems such as limited detection range, need for pretreatment, inability to directly acquire electrical signals, and inability to eliminate random errors.
An electrode modified with Cu72Pt28 alloy nanocrystals was used to calculate the sodium nitrite concentration by dual testing of linear voltammetric scanning curves and chronometric response current density. The good conductivity and catalytic activity of the electrode were utilized to directly measure the concentration in aqueous solution, and random errors were eliminated by combining a two-equation mutual correction method.
It enables the detection of sodium nitrite over a wide range (0-175 mmol/L), requires no pretreatment, has strong anti-interference capabilities, and provides highly accurate and small-error detection results.
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Figure CN117269272B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of nanomaterial sensing technology, specifically to a method utilizing Cu 72 Pt 28 A method for detecting sodium nitrite concentration in aqueous solution using alloy nanocrystals. Background Technology
[0002] In recent years, with changes in people's dietary habits, unhealthy diets and the overuse of additives have led to a series of diseases, making food safety a topic of concern once again. Sodium nitrite is a common additive that inhibits meat spoilage and maintains its color. However, excessive intake of sodium nitrite can lead to health problems. This is because sodium nitrite reacts with amines in the human body to form N-nitrosamines, which can cause stomach ailments. When the concentration of sodium nitrite ingested exceeds 1 mg / L, it can harm one's health. Therefore, the ability to efficiently, quickly, and accurately monitor the concentration of sodium nitrite in water systems or food is of great significance for protecting human health.
[0003] Compared to other detection methods, enzyme-free sensors based on electrochemical catalysis have attracted widespread attention due to their advantages such as short detection time, temperature independence, and strong anti-interference ability. However, research on the detection of nitrite concentration using this method has been limited for a long time. This is mainly because this method generally suffers from the following problems:
[0004] 1. The detection range is small, and it cannot accurately detect high concentrations of nitrite solutions.
[0005] Because existing materials have limited activity in catalyzing the oxidation of sodium nitrite, a large number of difficult-to-desorb intermediate substances are easily generated at the interface during the catalytic oxidation process of high-concentration nitrite. These intermediate substances are adsorbed on the electrode surface, hindering further oxidation between the working electrode and the sample under test, resulting in increased error when testing high-concentration samples.
[0006] 2. Pretreatment of the test solution is required; electrical signals cannot be directly acquired.
[0007] Because aqueous solutions have poor conductivity, most test liquids cannot be directly detected. In actual testing, phosphates need to be added to the test solution for pretreatment. This pretreatment not only renders the test sample unusable but also increases the complexity of the test.
[0008] 3. Failure to establish a results verification system makes it impossible to eliminate random errors.
[0009] Currently, most detection methods based on electrocatalytic reactions can be divided into two steps. The first step is to determine the function relating the fitted electrical signal to the concentration. The second step is to calculate the concentration of the sample based on the detected electrical signal. However, this method cannot eliminate random signal errors during the testing process. If there is a dispute over the test results, multiple tests must be conducted, and the errors must be eliminated according to the Laida criterion. Establishing a dual-test result verification system can effectively eliminate random errors in signal acquisition and avoid multiple sampling. Summary of the Invention
[0010] The present invention addresses the problem of nitrite concentration detection mentioned in the background section, and provides a method utilizing Cu 72 Pt 28 A method for detecting sodium nitrite concentration in aqueous solution using alloy nanocrystals.
[0011] Compared to traditional single-signal testing methods, this invention employs a dual testing approach, using both linear voltammetric scanning curves and chronodynamic response current density, to calculate the concentration of sodium nitrite in the test solution. The two results mutually correct each other, effectively eliminating random errors in signal acquisition. Because Cu 72 Pt 28 It has good conductivity and high catalytic activity, and can be directly measured in aqueous solution. The test method provided by this invention does not require pretreatment of the test sample, and the test sample can be used for other tests after use.
[0012] Using Cu 72 Pt 28 The method for detecting sodium nitrite concentration in aqueous solution using alloy nanocrystals is as follows:
[0013] (1) Using the three-electrode method, the prepared Cu 72 Pt 28 The working electrode is an alloy nanocrystal-modified glassy carbon electrode, the reference electrode is Ag / AgCl, and the counter electrode is a commercial Pt wire.
[0014] (2) Prepare sodium nitrite solutions of different concentrations using pure water as electrolyte, connect the three electrodes to the electrochemical workstation, and measure the linear voltammetric scan curves at different sodium nitrite concentrations;
[0015] (3) Based on the linear voltammetric scan test results, the functional relationship between the current density of the anode peak and the sodium nitrite concentration was fitted, which is Equation 1;
[0016] (4) Set the test potential, test the chronocurrent density of sodium nitrite solutions of different concentrations, and fit the function of response current and sodium nitrite concentration to form Equation 2;
[0017] (5) Test the linear voltammetric scan curve of the solution to be tested, and substitute the measured anode peak current density value into Equation 1 to calculate the sodium nitrite concentration C1 in the solution to be tested.
[0018] (6) Set the working potential, test the timing response current density of the solution to be tested, and substitute the test current density value into equation 2 to calculate the sodium nitrite concentration value C2 in the solution to be tested.
[0019] (7) Compare C1 and C2. If the concentration difference is greater than 3%, there is random error in the test and the test needs to be repeated. If the concentration difference is less than 3%, take the average of the two concentrations as the final measured value of sodium nitrite concentration in the aqueous solution.
[0020] Accordingly, the present invention also discloses Cu 72 Pt 28 The specific steps for preparing alloy nanocrystals are as follows:
[0021] (1) Using deionized water as a solvent, prepare 15 mmol / L copper chloride solution, 1 mol / L ascorbic acid solution, 10 mmol / L sodium chloroplatinate solution and 100 mmol / L hydrochloric acid solution respectively.
[0022] (2) Add potassium chloride powder to the prepared copper chloride solution and stir at room temperature for 10 minutes to obtain mixed solution 1, wherein the mass of potassium chloride added per milliliter of copper chloride solution is 8 mg;
[0023] (3) Add chloroplatinic acid solution to mixed solution 1 and stir at room temperature for 10 minutes to obtain mixed solution 2, wherein the volume ratio of chloroplatinic acid to mixed solution 1 is 2:15;
[0024] (4) Add ascorbic acid and hydrochloric acid solution to mixed solution 2 in sequence to obtain mixed solution 2. Stir at 25 degrees Celsius for 6 hours. The volume ratio of added ascorbic acid to hydrochloric acid is 2:1, and the volume ratio of added ascorbic acid to mixed solution 2 is 12:85.
[0025] (5) The obtained product was separated by centrifugation. First, it was dispersed in deionized water, sonicated, and then centrifuged twice. Next, it was dispersed in ethanol, sonicated, and centrifuged again. This process was repeated twice. Finally, it was dried in a forced-air drying oven. The resulting powder was Cu. 72 Pt 28 Alloy nanocrystals.
[0026] Implementing this invention has the following beneficial effects:
[0027] 1. Wide detection range; applicable to the detection of various aqueous solutions containing sodium nitrite.
[0028] The detection scheme provided by this invention can detect sodium nitrite solutions with concentrations of 0-175 mmol / L, with a wide detection range, and can be used for the detection of high-concentration sodium nitrite aqueous solutions.
[0029] 2. It can directly acquire electrical signals from aqueous solutions without requiring sample pretreatment.
[0030] The Cu provided by this invention 72 Pt 28 The alloy nanocrystals exhibit good electrical conductivity, enabling direct electrocatalytic oxidation of sodium nitrite in neutral solutions. Direct signal acquisition is simple and easy to operate, and the sample can be reused.
[0031] 3. Strong anti-interference ability and high accuracy
[0032] Because the Cu used in this invention 72 Pt 28 Alloy nanocrystals exhibit good selectivity for the electrocatalytic oxidation of sodium nitrite. Studies have shown that the presence of other soluble ions in the aqueous solution does not affect the test results.
[0033] 4. The two results correct each other, resulting in more accurate results.
[0034] This invention provides a method for mutual calibration of concentrations in two-equation tests, which can effectively eliminate random errors in signal acquisition and obtain more accurate results. Attached Figure Description
[0035] Figure 1 The Cu obtained in Example 1 of this invention 72 Pt 28 Field emission scanning electron microscope image of alloy nanocrystals.
[0036] Figure 2 This is the Cu used in Embodiment 2 of the present invention. 72 Pt 28 Linear voltammetric scan curves of alloy nanocrystal-modified electrodes in aqueous solutions of sodium nitrite at different concentrations.
[0037] Figure 3 It is a functional equation relating the oxidation current density of the anodic peak measured in Example 2 of this invention to the concentration of sodium nitrite solution.
[0038] Figure 4 These are the timing response current density curves of sodium nitrite aqueous solutions of different concentrations measured in Example 2 of this invention.
[0039] Figure 5 It is the functional equation of the response current density and sodium nitrite concentration measured in Example 2 of this invention.
[0040] Figure 6 This is the anti-interference test result of Embodiment 2 of the present invention.
[0041] Figure 7 This is the linear voltammetric scan curve of the test solution measured in Example 2 of the present invention.
[0042] Figure 8 This is the linear voltammetric scan curve of sodium nitrite aqueous solution of different concentrations measured using a bare electrode in Comparative Example 1 of this invention. Detailed Implementation
[0043] To make the technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.
[0044] Example 1: Cu 72 Pt 28 Preparation of alloy nanocrystals
[0045] (1) Using deionized water as solvent, prepare copper chloride solution with a concentration of 15 mmol / L, ascorbic acid solution with a concentration of 1 mol / L, sodium chloroplatinate solution with a concentration of 10 mmol / L and hydrochloric acid solution with a concentration of 100 mmol / L respectively.
[0046] (2) Take 75 mL of prepared copper chloride solution, add 0.6 g of potassium chloride, stir at room temperature for 10 minutes to obtain mixed solution 1;
[0047] (3) Add 10 mL of chloroplatinic acid solution to mixed solution 1 and stir at room temperature for 10 minutes to obtain mixed solution 2;
[0048] (4) Add 12 mL of ascorbic acid and 6 mL of hydrochloric acid solution to mixed solution 2 in sequence to obtain mixed solution 2, and stir at 25 degrees Celsius for 6 hours;
[0049] (5) The obtained product was separated by centrifugation. First, it was dispersed in deionized water, sonicated, and then centrifuged twice. Then, it was dispersed in ethanol, sonicated, and centrifuged again. This process was repeated twice. Finally, it was dried in a forced-air drying oven at 60-80 degrees Celsius. The resulting powder is Cu. 72 Pt 28 Alloy nanocrystals.
[0050] To investigate the composition of the obtained product, we performed X-ray diffraction tests on the sample. The results showed that the diffraction peaks of the sample were located in the diffraction peak range between pure Cu and pure Pt crystals, proving that the product was a CuPt alloy. From the position of the diffraction peaks on the (111) crystal plane, the atomic percentage of Cu to Pt can be calculated to be 72:28, that is, the obtained sample is Cu. 72 Pt 28 Alloy nanocrystals.
[0051] To investigate the obtained Cu 72 Pt 28 The morphology of the alloy powder was examined using scanning electron microscopy, and the results are shown in the attached instructions. Figure 1 As shown. From Figure 1 The obtained Cu can be seen from 72 Pt 28The alloy powder is granular with a size of about 40-60 nm and has good monodispersity, which is beneficial to improving its electrocatalytic performance.
[0052] Example 2: Using Cu 72 Pt 28 Alloy nanocrystal modified electrode for detecting sodium nitrite concentration in aqueous solution
[0053] (1) Using anhydrous ethanol, the prepared Cu 72 Pt 28 Alloy nanocrystals were prepared into a suspension with a concentration of 4 mg / mL. A volume of 3 μL of the suspension was taken with a pipette and dropped onto the surface of a glassy carbon electrode with a diameter of 3 mm. After the ethanol evaporated, a volume of 3 μL of a 0.1% perfluorosulfonic acid polymer solution was added as a protective film. After the solution evaporated, the resulting electrode was the working electrode modified with nanocrystals.
[0054] (2) Using the three-electrode method, the prepared Cu... 72 Pt 28 The alloy nanocrystal modified electrode is used as the working electrode, Ag / AgCl is used as the reference electrode, and commercial Pt wire is used as the counter electrode.
[0055] (3) Using Wahaha purified water as electrolyte, prepare sodium nitrite solutions of different concentrations, connect the three electrodes to the electrochemical workstation, measure the linear voltammetric scan curves of sodium nitrite solutions of different concentrations, and set the scan rate to 10mV / s;
[0056] (4) Based on the linear voltammetric scan test results, the equation between the current density of the anode peak and the sodium nitrite concentration is fitted, which is Equation 1;
[0057] (5) Set 1.5V vsAg / AgCl as a constant potential, test the chronocurrent density of sodium nitrite at different concentrations, and fit the function of response current and sodium nitrite concentration, which is Equation 2.
[0058] (6) Test the linear voltammetric scan curve of the solution to be tested (scan rate is 10mV / s), and calculate the sodium nitrite concentration C1 in the solution to be tested by substituting the measured anode peak current density value into Equation 1.
[0059] (7) Test the chronocurrent density of the solution under oxidation potential, and calculate the sodium nitrite concentration C2 in the solution by substituting the test current density value into equation 2.
[0060] (8) Compare C1 and C2. If the concentration difference is greater than 3%, there is random error in the test and the test needs to be repeated. If the concentration difference is less than 3%, take the average of the two concentrations as the final measured value of sodium nitrite concentration in the aqueous solution.
[0061] Figure 2 This invention utilizes Cu 72 Pt 28 Linear voltammetric scan curves of alloy nanocrystal-modified electrodes in aqueous solutions of sodium nitrite at different concentrations. For example... Figure 2 It can be seen that when sodium nitrite is added to the aqueous solution, a distinct anodic oxidation peak appears at the 1.5 V vs Ag / AgCl position in the linear voltammetry curve. The appearance of the anodic peak is due to the electrocatalytic oxidation by sodium nitrite. As the concentration of sodium nitrite in the aqueous solution increases from 0 mmol / L to 175 mmol / L, the current density of the anodic oxidation peak gradually increases. Based on the linear voltammetry scan results, equation 1 (as shown in the appendix) is fitted to the relationship between the current density of the anodic peak and the sodium nitrite concentration. Figure 3 The equation is: Y(μA / cm) 2 The equation is: C1 = 198.23X (mmol / L) + 203.91, where X represents the concentration of the sodium nitrite aqueous solution and Y represents the current density. When we test the anodic current density (i.e., the Y value) of the sample, we can calculate the corresponding concentration, which is C1 (the X value in Equation 1).
[0062] in accordance with Figure 3 At the anode peak position, we set the potential for timing response current testing to 1.5V vs Ag / AgCl. Figure 4 This is Example 2 of the present invention, which utilizes Cu 72 Pt 28 Chrono-response current curves of the alloy nanocrystal-modified electrode in aqueous solutions of sodium nitrite at different concentrations. At this potential, sodium nitrite undergoes oxidation; as the concentration of sodium nitrite in the solution increases, the number of charges participating in the reaction increases, and the response current density increases linearly. Cu on the surface of the working electrode... 72 Pt 28 The alloy acts as a catalyst, accelerating the oxidation reaction. For example... Figure 5 The response current density exhibits a piecewise linear relationship with the sodium nitrite concentration (i.e., Equation 2). In the function, X represents the concentration of sodium nitrite, and Y represents the response current density. For a concentration range of 50-250 mmol / L, the fitted equation 2 is: 137.14X (mmol / L) + 10605.24 = Y (μA / cm²). 2 The linear fitting coefficient was 0.988. For the concentration range of 0-50 mmol / L, the fitting equation 2 was: 314.21X (mmol / L) + 28.25 = Y (μA / cm³). 2 The segmentation of the function is due to the increased oxidation potential of high-concentration sodium nitrite. When we test the response current density of the test solution at 1.5V vsAg / AgCl, we can calculate the corresponding concentration, C2, using Equation 2.
[0063] To verify the anti-interference capability of the detection method provided by this invention, we added interfering substances (interfering substance concentration 5 mmol / L) sequentially to a prepared sodium nitrite solution and measured the change in the response current density to the interfering substances. (See attached diagram) Figure 6 As shown, the addition of interfering substances has almost no significant effect on the response current density. This proves that the method for detecting sodium nitrite provided by this invention has excellent anti-interference properties. Even when the sodium nitrite sample contains other soluble substances, it does not significantly affect the test results.
[0064] To verify the detection method of this invention for detecting sodium nitrite in actual aqueous solutions, we calculated the concentration of the test solution (C2 value) using the chronodynamic response current density and Equation 2, which was 125.1 mmol / L. Simultaneously, we measured the linear voltammetric scan curve of the test solution, and the results are as follows: Figure 7 As shown.
[0065] like Figure 7 The anodic peak current density of the test solution is 28053.78 μA / cm². 2 Substituting into Equation 1: 137.14X (mmol / L) + 10605.24 = Y (μA / cm²) 2 From this, we can calculate C1 to be 127.3 mmol / L. The error between C1 and C2 is 1.7%, which is less than the set standard of 3%, so there is no need to repeat the test. Therefore, the actual concentration of the test solution is the average of C1 and C2, which is 126.2 mmol / L.
[0066] Comparative Example 1: Linear Voltammetric Scan Tests of Sodium Nitrite Solutions at Different Concentrations Using Bare Electrodes
[0067] (1) Use a pipette to take 3 μL of a 0.1% perfluorosulfonic acid polymer solution and drop it onto the surface of a glassy carbon electrode with a diameter of 3 mm. After the solution evaporates, it can be used as the working electrode (bare electrode).
[0068] (2) The three-electrode method is adopted, using the bare electrode from step 1 as the working electrode, Ag / AgCl as the reference electrode, and commercial Pt wire as the counter electrode.
[0069] (3) Using Wahaha purified water as electrolyte, prepare sodium nitrite aqueous solutions of different concentrations, connect the three electrodes to the electrochemical workstation, set the scan rate to 10mV / s, and measure the linear voltammetric scan curves of sodium nitrite solutions of different concentrations.
[0070] The key technology of this invention lies in the use of Cu 72 Pt 28 Alloy nanocrystals modify the surface of the working electrode, Cu 72 Pt 28Alloy nanocrystals can catalyze the electrochemical oxidation of sodium nitrite in solution, thereby achieving linear changes in electrical signals under different sodium nitrite concentrations. Based on two sets of linear equations relating sodium nitrite concentration and electrical signals, the accuracy of the test results is corrected, and the concentration value of the test solution is determined.
[0071] To prove that the bare electrode (not coated with Cu) 72 Pt 28 Since the working electrode modified with alloy nanocrystals cannot achieve the technical effect of the present invention, we conducted a comparative example 1 experiment.
[0072] like Figure 8 To measure the linear voltammetric scan curves of sodium nitrite at different concentrations using a bare electrode, the anodic peak potential in Comparative Example 1 was significantly higher than 1.5V in a 50 mmol / L sodium nitrite solution compared to the linear voltammetric curve in Example 1. As the sodium nitrite solution concentration increased to 100 mmol / L, this potential shifted to a higher potential. Due to this shift in the current peak, the anodic peak current density did not exhibit a linear relationship with the sodium nitrite concentration, making it impossible to establish linear equation 1 (test C1). Furthermore, due to the significant shift in the anodic peak potential with increasing concentration, this electrode was unsuitable for acquiring timing response current signals at a specified potential, making it impossible to establish linear equation 2 (response current as a function of sodium nitrite concentration). Therefore, it can be confirmed that the technical effect of this invention cannot be achieved when using an unmodified working electrode for the same electrical signal acquisition.
[0073] In summary, this paper provides a method for utilizing Cu 72 Pt 28 A method for detecting sodium nitrite concentration in aqueous solution using alloy nanocrystals. It should be noted that the above description is a preferred embodiment of the invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the invention, and these improvements and modifications are also considered within the scope of protection of the invention.
Claims
1. A method utilizing Cu 72 Pt 28 A method for detecting sodium nitrite concentration in aqueous solution using alloy nanocrystals, characterized in that... The specific method for detecting the concentration of sodium nitrite in an aqueous solution is as follows: (1) A three-electrode method was adopted, using Ag / AgCl as the reference electrode and commercial Pt wire as the counter electrode, and the prepared Cu 72 Pt 28 Alloy nanocrystals are used to modify the surface of a glassy carbon electrode, which is then used as a working electrode. (2) Using pure water as electrolyte, prepare sodium nitrite solutions of different concentrations, connect the three electrodes to the electrochemical workstation, set the scan rate, and measure the linear voltammetric scan curves of sodium nitrite solutions of different concentrations; (3) The functional relationship between the current density of the anode peak and the sodium nitrite concentration was fitted, which is Equation 1; (4) Based on the position of the anodic peak of the scan, set the potential, test the timing response current density under different sodium nitrite concentrations, fit the functional relationship between the response current density and the sodium nitrite concentration, which is Equation 2; (5) Test the linear voltammetric scan curve of the solution to be tested, and calculate the sodium nitrite concentration C1 in the solution to be tested based on the measured anodic peak current density and Equation 1. (6) Test the chronocurrent density of the solution to be tested, and calculate the sodium nitrite concentration C2 in the solution to be tested based on the response current density value and equation 2. (7) Compare C1 and C2. If the concentration difference is less than 3%, the test result is correct. Take the average of the two concentrations as the final concentration of sodium nitrite in the aqueous solution. Wherein, the Cu in step (1) 72 Pt 28 The preparation method of alloy nanocrystals is as follows: (1) Using deionized water as solvent, prepare copper chloride solution with a concentration of 15 mmol / L, ascorbic acid solution with a concentration of 1 mol / L, sodium chloroplatinate solution with a concentration of 10 mmol / L and hydrochloric acid solution with a concentration of 100 mmol / L respectively. (2) Take 75 mL of the above copper chloride solution, add 0.6 g of potassium chloride to it, and stir for 10 minutes at room temperature to obtain mixed solution 1; (3) Add 10 mL of the above sodium chloroplatinate solution to mixed solution 1 and stir for 10 minutes at room temperature to obtain mixed solution 2; (4) Add 12 mL of the above ascorbic acid solution and 6 mL of the above hydrochloric acid solution to the mixed solution 2 in sequence, and stir at 25 degrees Celsius for 6 hours; (5) The obtained product was separated by centrifugation. First, it was dispersed in deionized water, sonicated, and then centrifuged twice. Then, it was dispersed in ethanol, sonicated, and centrifuged again. This process was repeated twice. Finally, it was dried in a forced-air drying oven at 60-80 degrees Celsius. The resulting powder is Cu. 72 Pt 28 Alloy nanocrystals.