A method of distinguishing between metal ions Cu 2+ and Mn 2+ ​

Abstract

A method for distinguishing metal ions Cu 2+ and Mn 2+ This method utilizes a pH clock reaction system of "urease-CO(NH2)2-H2SO4" as the distinguishing solution, based on the Cu of the sample to be distinguished. 2+ and Mn 2+ The reactions between Cu and the products of urea hydrolysis catalyzed by urease differ, resulting in different patterns produced by the pH clock system, thus enabling the determination of Cu... 2+ and Mn 2+ Qualitative analysis of Cu involved in this invention. 2+ and Mn 2+ The qualitative analysis method is characterized by high accuracy, ease of operation, and convenience.

Description

TECHNICAL FIELD

[0001] The present application relates to a distinguishing method, in particular, a "urease-CO(NH2)2-H2SO4" pH clock system is established, and the reaction between Cu 2+ and Mn 2+ and the hydrolysis product of urea catalyzed by urease is different, so that they are different in the pattern generated by the pH clock system, thereby realizing the qualitative analysis of Cu 2+ and Mn 2+ . It belongs to the field of analytical chemistry. BACKGROUND

[0002] Copper sulfate is an inorganic compound with the chemical formula CuSO4, and anhydrous copper sulfate is white or off-white powder. Copper sulfate is both a fertilizer and a widely used fungicide. Bordeaux liquid, copper soap liquid and copper ammonium preparation are prepared by mixing copper sulfate with lime milk, soap and ammonium bicarbonate. Manganese sulfate is an inorganic compound with the chemical formula MnSO4, and is commonly used as a trace analysis reagent, a mordant and a paint drying agent. The detection methods for copper sulfate and manganese sulfate currently include colorimetric method, immersion method, fumigation method and improved EDTA method. However, most of these detection methods require large equipment and are expensive, and are not suitable for on-site determination. Therefore, it is necessary to find a detection and analysis method that has good detection effect and is simple and fast to operate.

[0003] The present application aims to provide a novel and convenient and fast distinguishing method for metal ions Cu 2+ and Mn 2+ , that is, a method for qualitative detection of sample solution to be distinguished by using "urease-CO(NH2)2-H2SO4" pH clock system as distinguishing solution, which is based on the different sensitive responses of the pH clock system to different metal ions. Specifically, the "urease-CO(NH2)2-H2SO4" pH clock reaction system is used as the distinguishing solution, and the pattern of pH change with time is recorded; when the pH of the pH clock reaction jumps and reaches a stable pH (t=225s), equal volumes of sample solution to be distinguished containing metal ions Cu 2+ or Mn 2+ (CuSO4 or MnSO4) with the same concentration are added into two groups of pH clock systems, because the reactions between Cu 2+ and Mn 2+ and the hydrolysis product of urea catalyzed by urease are different (Cu 2+ and OH - dissociated from the ammonia water of the urea hydrolysis product combine to form Cu(OH)2 precipitate; while Mn 2+ and CO32- The combination of MnCO3 precipitate formation results in different patterns produced by the pH clock system, thus enabling the determination of Cu... 2+ and Mn 2+ Qualitative analysis.

[0004] The difference between this qualitative differentiation method and existing technologies lies in the fact that this invention uses a "urease-CO(NH2)2-H2SO4" pH clock system as the differentiation solution, because the sample to be differentiated, Cu... 2+ and Mn 2+ The reaction between urea and the products of urease-catalyzed hydrolysis (Cu) is different. 2+ OH- ions released from ammonia, a product of urea hydrolysis - The combination forms Cu(OH)2 precipitate; while Mn 2+ CO3 formed from CO2, a product of urea hydrolysis 2- The combination of MnCO3 precipitate formation results in different patterns produced by the pH clock system, thus enabling the determination of Cu... 2+ and Mn 2+ Qualitative analysis. If, after adding the solution to be distinguished, the pH of the pH clock system drops rapidly and then stabilizes, forming a plateau, then the added sample to be distinguished contains Cu metal ions. 2+ If, after adding the solution to be distinguished, the pH of the pH clock system shows a rapid decrease followed by a slow rise, forming a downward spike, then the added sample to be distinguished contains the metal ion Mn. 2+ sample.

[0005] When the sample solution to be distinguished is detected in the distinguishing solution (pH clock system), the temperature of the pH clock system is controlled at any specific temperature within the range of 15-25℃.

[0006] Metal ion Cu 2+ and Mn 2+ The distinguishable concentration range in the distinguishing solution (pH clock system) is 8.89 × 10⁻⁶. -3 -1.78×10 -2 mol / L.

[0007] The concentration range that the above-mentioned solutions can distinguish is the optimal concentration range determined experimentally. Within this concentration range, the metal ion Cu... 2+ and Mn 2+ The effects of the differentiating solution on the pH clock system are very significant, easy to observe and analyze, and easy to differentiate. Furthermore, the concentration ranges of each component in the differentiating solution (pH clock system) are shown in Table 1, and the optimal solution for the differentiating solution (pH clock system) obtained through multiple experiments is shown in Table 2.

[0008] Table 1: Concentration of each component in pH clock system

[0009] Urease (U / mL) CO(NH2)2(mol / L) H2SO 4 (mol / L)] 5-25 1.46 x 10 -3 -4.15 x 10 -3 ]]> 1.125 x 10 -5 -3.75 x 10 -5 ]]>

[0010] Table 2: Optimum concentration of each component in pH clock system

[0011] Urease (U / mL) CO(NH2) 2 (mol / L) H2SO 4 (mol / L)] 10.08 1.62 x 10 -3 ]]> 1.27 x 10 -5 ]]>

[0012] The specific experimental steps are as follows:

[0013] 1. Prepare 45 mL of a distinguishing solution (pH clock system) according to the concentration range specified in Table 1, and control the temperature to be constant at a specific temperature value between 15-25°C; insert the prepared working electrode (pH composite electrode, Leiming, E-331) into the solution, and connect the other end of the working electrode to a computer through a potential / temperature / pH comprehensive tester (Ji Xing Dingsheng Electronic Technology Co., Ltd., ZHFX-595); after setting the collection time and sampling speed in the chemical signal collection and analysis program on the computer, quickly click the start key to monitor the pH of the solution. The computer records the pH-time curve, i.e., the pH clock spectrum. When the substance to be detected is needed, after the pH jump of the pH clock reaction appears, and reaches a stable pH (t=225s), record the pH-time pH clock spectrum in the same way.

[0014] The basic parameters of the pH clock spectrum include:

[0015] pH jump range: the pH corresponding to the beginning of the pH jump to the pH corresponding to the end of the pH jump. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is the pH-time curve of the distinguishing solution (pH clock system) in Example 1 without adding the sample to be distinguished.

[0017] Figure 2 is the pH-time curve of the distinguishing solution (pH clock system) in Example 1 after adding 8.89×10 -3 mol / L CuSO4.

[0018] Figure 3 is the pH-time curve of the distinguishing solution (pH clock system) in Example 1 after adding 8.89×10 -3 mol / L MnSO4.

[0019] Figure 4 is the XRD spectrum of the precipitate produced by the distinguishing solution after adding CuSO4 in Example 1, and the precipitate is detected to be Cu4(OH)6SO4.

[0020] Figure 5 Figure 2 is an XRD pattern of the precipitate produced by the discrimination solution in Example 1 after the addition of MnSO4. The precipitate was determined to be MnCO3.

[0021] Figure 6 Figure 4 is a plot of the change in pH of the discrimination solution (pH clock system) over time in Example 2 without the addition of a sample to be discriminated.

[0022] Figure 7 Figure 5 is a plot of the change in pH of the discrimination solution (pH clock system) over time in Example 2 after the addition of 1.33 x 10 -2 mol / L CuSO4.

[0023] Figure 8 Figure 6 is a plot of the change in pH of the discrimination solution (pH clock system) over time in Example 2 after the addition of 1.33 x 10 -2 mol / L MnSO4.

[0024] Figure 9 Figure 8 is a plot of the change in pH of the discrimination solution (pH clock system) over time in Example 3 without the addition of a sample to be discriminated.

[0025] Figure 10 Figure 9 is a plot of the change in pH of the discrimination solution (pH clock system) over time in Example 3 after the addition of 1.78 x 10 -2 mol / L CuSO4.

[0026] Figure 11 Figure 10 is a plot of the change in pH of the discrimination solution (pH clock system) over time in Example 3 after the addition of 1.78 x 10 -2 mol / L MnSO4. Embodiment

[0027] Example

[0028] This example demonstrates the feasibility of the method of the present application for discriminating between metal ions Cu 2+ and Mn 2+ as follows:

[0029] (1) Preparation of discrimination solution

[0030] First, a 0.005 mol / L solution of CO(NH2)2, a 1.1 x 10 -4 mol / L solution of H2SO4 and a 18 U / mL solution of urease were prepared using distilled water. To a 50 mL beaker, 5.7 mL of the 1.1 x 10 -4mol / L H2SO4 solution, 15.5 mL of 0.005 mol / L CO(NH2)2 solution, 23.8 mL of 20 U / mL urease solution, so as to ensure that the concentrations of H2SO4, CO(NH2)2 and urease in the "urease-CO(NH2)2-H2SO4" pH clock system are 1.25 x 10 -5 mol / L, CO(NH2)2 1.72 x 10 -3 mol / L and urease 10.578 U / mL respectively, and the total volume is 45 mL, and the temperature is controlled at 18°C.

[0031] Meanwhile, a series of sample solutions containing metal ions Cu 2+ or Mn 2+ at different concentrations are prepared in distilled water (CuSO4 solution or MnSO4 solution).

[0032] (2) Obtain the pH clock spectrum

[0033] The spectrum of the pH value of the prepared discrimination solution (pH clock system) changing with time is recorded by a computer equipped with a chemical signal collection and analysis program (without adding the sample to be detected), as shown in Figure 1 . Another two groups of discrimination solutions with the same concentrations of components as the above discrimination solution are prepared. For one of the groups, after the pH jump of the pH clock reaction occurs and a stable pH is reached (t = 225 s), 400 μL of 1 mol / L CuSO4 sample solution is added to the 45 mL pH clock system, so that the concentration of CuSO4 in the discrimination solution is 8.89 x 10 -3 mol / L. After the rapid decrease of pH caused by the addition of CuSO4, the pH remains stable and forms a platform, as shown in Figure 2 . For the other group, after the pH jump of the pH clock reaction occurs and a stable pH is reached (t = 225 s), 400 μL of 1 mol / L MnSO4 sample solution is added to the 45 mL pH clock system, so that the concentration of MnSO4 in the discrimination solution is 8.89 x 10 -3 mol / L. After the rapid decrease of pH caused by the addition of MnSO4, the pH slowly rises and forms a downward sharp peak, as shown in Figure 3 .

[0034] (3) Discrimination

[0035] Because CuSO4 and MnSO4 contain different metal ions, and the reactions between different metal ions and the hydrolysis products of urea catalyzed by urease are different, they produce different spectra in the pH clock system. Comparing Figure 1 , Figure 2 , Figure 3It can be seen that, after the addition of CuSO4, the pH clock compared with the sample without the addition of the sample to be detected, the pH appears a rapid decline and then remains stable, forming a platform; after the addition of MnSO4, the pH clock compared with the sample without the addition of the sample to be detected, the pH appears a rapid decline and then slowly rises, forming a downward peak. From the above experiment, it can be seen that by comparing the patterns of the pH clock system, the metal ions Cu 2+ and Mn 2+ can be distinguished.

[0036] In order to explore the reaction mechanism between metal ions and the pH clock system in the above distinguishing process (the reaction mechanism between metal ions and the hydrolysis products of urea catalyzed by urease), the precipitate produced in each distinguishing experiment was enriched, centrifuged and washed three times, dried in an oven at 60°C for 24 hours, and finally the obtained precipitate was subjected to XRD detection. The experimental results show that: when CuSO4 solution is added to the pH clock system, a blue precipitate is generated, and the XRD pattern of the precipitate after the above treatment is shown in Figure 4 . Diffraction peaks appear at 2θ of 12.632 ◦ , 16.916 ◦ , 18.205 ◦ , 25.442 ◦ , 33.165 ◦ , 34.249 ◦ , 37.025 ◦ , 38.524 ◦ , 39.818 ◦ , 44.622 ◦ , 46.408 ◦ . After comparison with the standard PDF card, it is confirmed that the obtained blue precipitate is Cu4(OH)6SO4 (PDF #43-0670). When MnSO4 solution is added to the pH clock system, a white precipitate is generated, and the XRD pattern of the precipitate after the above treatment is shown in Figure 5 . Diffraction peaks appear at 2θ of 24.251 ◦ , 31.361 ◦ , 37.522 ◦ , 41.423 ◦ , 45.186 ◦ , 49.678 ◦ , 51.688 ◦ , 59.181 ◦ , 60.132 ◦ . After comparison with the standard PDF card, it is confirmed that the obtained white precipitate is MnCO3 (PDF #44-1472).

[0037] The determination of the composition of the precipitate can infer the reaction mechanism. The main reaction of the pH clock system itself is the hydrolysis of urea catalyzed by urease:

[0038] CO(NH2)2 + H2O →2NH3 + CO2

[0039] Cu 2+ After adding the pH clock system, Cu 2+ combined with OH - dissociated from the ammonia water produced by the hydrolysis of urea, to form Cu(OH)2precipitate, causing the pH to drop rapidly. Because the pH system contains Cu 2+ , SO4 2- , the final precipitate formed is Cu4(OH)6SO4 (considered as CuSO4•3Cu(OH)2), which does not affect the urea hydrolysis reaction of the pH clock system, so after the rapid drop in pH, a platform is formed. Mn 2+ After adding the pH clock system, Mn 2+ combined with CO3 2- to form MnCO3precipitate, which involves the consumption of CO2, the urea hydrolysis product of the pH clock system. The reaction of CO2 in water is:

[0040] CO2+ H2O⇌ H + + HCO3 -

[0041] HCO3 - ⇌ CO3 2- + H +

[0042] When Mn 2+ combined with CO3 2- , an equivalent amount of H - is generated. H + , causing the pH to drop rapidly. The CO3 2+ combined by Mn 2- comes from the CO2, the urea hydrolysis product of the pH clock system, causing the CO2concentration to decrease, resulting in the equilibrium of the urea hydrolysis reaction gradually moving to the right to produce more NH3, causing the pH to slowly rise. Therefore, the pH clock system after adding Mn 2+ shows a slow rise after a rapid drop in pH, forming a downward spike.

[0043] ​​Take two 1 mol / L solutions of the samples to be distinguished (one is a CuSO4 solution and the other is a MnSO4 solution, but they have not been distinguished yet), mark one as sample 1 and the other as sample 2; prepare two groups of distinguishing solutions with the same concentrations of components as above, add 400 μL of 1 mol / L sample 1 and sample 2 respectively, so that their concentrations in the distinguishing solution are 8.89×10 -3 mol / L.

[0044] Analysis and comparison show that: the addition of sample 1 causes the pH clock system to have a rapid pH drop followed by a stable plateau (the graph corresponds to Figure 2 and does not correspond to Figure 3 ); and the addition of sample 2 causes the pH clock system to have a rapid pH drop followed by a slow rise, forming a downward peak (the graph corresponds to Figure 3 and does not correspond to Figure 2 ). Therefore, sample 1 is the CuSO4 solution and sample 2 is the MnSO4 solution, thereby achieving the distinction between metal ions Cu 2+ and Mn 2+ . Example

[0045] This example verifies the feasibility of the method for distinguishing between metal ions Cu 2+ and Mn 2+ of the present application according to the following steps:

[0046] (1) Preparation of distinguishing solution

[0047] First, prepare 0.005 mol / L CO(NH2)2 solution, 1.1×10 -4 mol / L H2SO4 solution and 18 U / mL urease solution with distilled water. Add 5.2 mL of 1.1×10 -4 mol / L H2SO4 solution, 14.6 mL of 0.005 mol / L CO(NH2)2 solution and 25.2 mL of 20 U / mL urease solution into a 50 mL beaker in sequence to ensure that the concentrations of the components in the "urease-CO(NH2)2-H2SO4" pH clock system are H2SO4 1.27×10 -5 mol / L, CO(NH2)2 1.62×10 -3 mol / L and urease 10.08 U / mL, and the total volume is 45 mL, with the temperature controlled at 18°C.

[0048] Meanwhile, prepare a series of solutions containing metal ions Cu 2+ or Mn 2+The sample solution to be distinguished (CuSO4 solution or MnSO4 solution).

[0049] (2) Obtain the pH clock profile

[0050] The profile of the pH value of the prepared distinguishing solution (pH clock system) changing with time is recorded by a computer equipped with a chemical signal collection and analysis program (without adding the sample to be detected), as shown in Figure 6 . Two groups of distinguishing solutions with the same concentrations of components as the above distinguishing solution are prepared. For one group, after the pH jump of the pH clock reaction, when a stable pH is reached (t = 225 s), 400 μL of 1.5 mol / L CuSO4 sample solution is added to 45 mL of the pH clock system, so that the concentration of CuSO4 in the distinguishing solution is 1.33 x 10 -2 mol / L. The pH rapidly decreases and then remains stable, forming a platform, as shown in Figure 7 . For the other group, after the pH jump of the pH clock reaction, when a stable pH is reached (t = 225 s), 400 μL of 1.5 mol / L MnSO4 sample solution is added to 45 mL of the pH clock system, so that the concentration of MnSO4 in the distinguishing solution is 1.33 x 10 -2 mol / L. The pH rapidly decreases and then slowly rises, forming a downward peak, as shown in Figure 8 .

[0051] (3) Distinguish

[0052] As CuSO4 and MnSO4 contain different metal ions, and the reactions between different metal ions and the hydrolysis products of urea catalyzed by urease are different (Cu 2+ and the OH - released by the dissociation of the ammonia water of the urea hydrolysis product combine to form Cu(OH)2 precipitate; while Mn 2+ and the CO3 2- formed by the combination of the CO2 of the urea hydrolysis product combine to form MnCO3 precipitate), they produce different profiles for the pH clock system. As can be seen from Figure 6 , Figure 7 , Figure 8 , the addition of CuSO4 makes the pH clock rapidly decrease and then remain stable, forming a platform compared with the pH clock without adding the sample to be detected; the addition of MnSO4 makes the pH clock rapidly decrease and then slowly rise, forming a downward peak compared with the pH clock without adding the sample to be detected. As can be seen from the above experiment, by comparing the profiles of the pH clock system, the metal ions Cu 2+ and Mn 2+ can be distinguished.

[0053] Take two 1.5 mol / L of the solution of the sample to be distinguished (one of them is CuSO4 solution, the other is MnSO4 solution, but both have not been distinguished), one of them is labeled as sample 1, the other is labeled as sample 2; prepare two groups of each component concentration is the same as the above concentration of the distinguishing solution, respectively, add 400 μL 1.5 mol / L of sample 1 and sample 2, so that their concentration in the distinguishing solution is 1.33 × 10 -2 mol / L.

[0054] Analysis and comparison can be seen: the addition of sample 1, the pH clock system appears a rapid decline in pH after keeping stable, forming a platform, (the degree of decline and Figure 7 corresponding, and Figure 8 not corresponding), while the addition of sample 2 makes the pH clock system appear a rapid decline in pH after slowly rising, forming a downward peak (the degree of decline and Figure 8 corresponding, and Figure 7 not corresponding). Therefore, sample 1 is CuSO4 solution, sample 2 is MnSO4 solution, thereby realizing the distinction of metal ions Cu 2+ and Mn 2+ . Example

[0055] This example verifies the feasibility of the method for distinguishing metal ions Cu 2+ and Mn 2+ of the present application as follows:

[0056] (1) Preparation of distinguishing solution

[0057] First, prepare 0.005 mol / L of CO(NH2)2 solution, 1.1 × 10 -4 mol / L of H2SO4 solution and 18 U / mL of urease solution with distilled water. Add 4.8 mL of 1.1 × 10 -4 mol / L H2SO4 solution, 15.3 mL of 0.005 mol / L CO(NH2)2 solution, 24.9 mL of 20 U / mL urease solution into a 50 mL beaker in turn, to ensure that the concentration of each component in the "urease-CO(NH2)2-H2SO4" pH clock system is H2SO4 1.17 × 10 -5 mol / L, CO(NH2)2 1.70 × 10 -3 mol / L, urease 11.067 U / mL, and the total volume is 45 mL, the temperature is controlled at 18℃.

[0058] At the same time, prepare a series of different concentrations of metal ion Cu2+ or Mn 2+ The sample solution to be distinguished (CuSO4 solution or MnSO4 solution).

[0059] (2) Obtain the pH clock profile

[0060] The profile of the pH value of the prepared distinguishing solution (pH clock system) changing with time is recorded by a computer equipped with a chemical signal collection and analysis program (without adding the sample to be detected), as shown in Figure 9 Two groups of distinguishing solutions with the same concentrations of components as the above distinguishing solution are prepared. For one group, after the pH jump of the pH clock reaction, when a stable pH is reached (t = 225 s), 400 μL of 2 mol / L CuSO4 sample solution is added to 45 mL of the pH clock system, so that the concentration of CuSO4 in the distinguishing solution is 1.78 × 10 -2 mol / L. The CuSO4 added makes the pH rapidly decrease and then remain stable, forming a platform, as shown in Figure 10 For the other group, after the pH jump of the pH clock reaction, when a stable pH is reached (t = 225 s), 400 μL of 2 mol / L MnSO4 sample solution is added to 45 mL of the pH clock system, so that the concentration of MnSO4 in the distinguishing solution is 1.78 × 10 -2 mol / L. The MnSO4 added makes the pH rapidly decrease and then slowly increase, forming a downward peak, as shown in Figure 11

[0061] (3) Distinguish

[0062] As CuSO4 and MnSO4 contain different metal ions, and the reactions between different metal ions and the hydrolysis products of urea catalyzed by urease are different (Cu 2+ and the OH - released by the dissociation of the ammonia water of the urea hydrolysis product combine to form Cu(OH)2 precipitate; while Mn 2+ and the CO3 2- formed by the combination of the CO2 of the urea hydrolysis product combine to form MnCO3 precipitate), so that they produce different profiles for the pH clock system. As can be seen from Figure 9 , Figure 10 , and Figure 11 , the addition of CuSO4 makes the pH clock rapidly decrease and then remain stable, forming a platform, compared with the pH clock without adding the sample to be detected; the addition of MnSO4 makes the pH clock rapidly decrease and then slowly increase, forming a downward peak, compared with the pH clock without adding the sample to be detected. As can be seen from the above experiment, by comparing the profiles of the pH clock system, the metal ions Cu 2+ and Mn​2+ The distinction.

[0063] Take two pre-prepared 2 mol / L solutions of the samples to be distinguished (one is a CuSO4 solution, and the other is a MnSO4 solution, but they have not yet been distinguished). Label one as Sample 1 and the other as Sample 2. Prepare two sets of distinguishing solutions with the same concentrations of each component as described above. Add 400 μL of 1 mol / L Sample 1 and Sample 2 to each solution, so that their concentrations in the distinguishing solutions are 1.78 × 10⁻⁶. -2 mol / L.

[0064] Analysis and comparison show that the addition of sample 1 caused the pH clock system to drop rapidly and then stabilize, forming a plateau (the degree of drop is related to...). Figure 10 Corresponding to, and Figure 11 (Not corresponding), while the addition of sample 2 caused the pH clock system to show a rapid decrease in pH followed by a slow increase, forming a downward spike (the degree of decrease is similar to...). Figure 11 Corresponding to, and Figure 10 (Not corresponding). Therefore, sample 1 is a CuSO4 solution and sample 2 is a MnSO4 solution, thus achieving the desired effect on the metal ion Cu. 2+ and Mn 2+ The distinction.

[0065] As can be seen from the above examples, the concentration is 8.89 × 10⁻⁶. -3 -1.78×10 -2 Cu in the range of mol / L 2+ and Mn 2+ All of them can be distinguished using the method of this invention.

Claims

1. A method of distinguishing between metal ions Cu 2+ and Mn 2+ characterized in that: A sample solution to be distinguished was prepared with distilled water as a solvent, and metal ions of Cu 2+ and Mn 2+ were added thereto. The pH value of the pH clock system was recorded as a function of time using the "urease-CO(NH2)2-H2SO4" pH clock system as a distinguishing solution. The pH clock system temperature is controlled at any one specific temperature within the range of 15-25℃; when the pH jump occurs in the pH clock system reaction, a stable pH is reached, and then equal volume of the same concentration of the metal ion Cu 2+ or Mn 2+ containing sample solution to be distinguished is added into the two groups of pH clock systems. Since Cu 2+ binds with the OH - dissociated from the urea hydrolysis product ammonia water to form Cu(OH)2 precipitate, and Mn 2+ binds with the CO3 2- formed from the urea hydrolysis product CO2 to form MnCO3 precipitate, they produce different graphs for the pH clock system, thus realizing the qualitative analysis of Cu 2+ and Mn 2+ : if the pH of the pH clock system rapidly decreases and then remains stable to form a platform after the sample solution to be distinguished is added, then the sample solution to be distinguished contains metal ion Cu 2+ ​ If after adding the sample solution to be distinguished, the pH of the pH clock system appears a rapid decrease and then a slow increase, forming a downward sharp peak, then the sample solution to be distinguished added contains metal ions Mn 2+ sample solution; The range of molar concentrations of the components in the solution is: urease 5-25 U / mL, CO(NH2)2 1.46 x 10 -3 -4.15 x 10 - 3 mol / L, H2SO4 1.125 x 10 -5 -3.75 x 10 -5 mol / L; The distinguishable concentration range of the sample solution to be distinguished in the distinguishing solution is 8.89 x 10 -3 -1.78 x 10 -2 mol / L.

2. The method of claim 1, wherein: The molar concentration of each component in the solution was urease 10.08 U / mL, CO(NH2)2 1.62 x 10 -3 mol / L, H2SO4 1.27 x 10 -5 mol / L.

3. The method of claim 1, wherein: The clock system was temperature controlled at 18°C.

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