A method for distinguishing between metal ions fe2+ and ni2+

Abstract

A method for distinguishing metal ions Fe 2+ and Ni 2+ , the method applies a "urease-CO(NH2)2-H2SO4" pH clock reaction system as a distinguishing solution, according to the different induction time generated by metal ions Fe 2+ and Ni 2+ in the pH clock system, so as to realize the qualitative analysis of Fe 2+ and Ni 2+ . The qualitative analysis method of Fe 2+ and Ni 2+ involved in the present application has the characteristics of high accuracy, easy operation and convenience.

Description

Technical Field

[0001] This invention relates to a method for differentiation, specifically, the establishment of a "urease-CO(NH2)2-H2SO4" pH clock system, which differentiates the samples based on the different induction times of the pH clock system produced by the samples to be differentiated, and belongs to the field of analytical chemistry. Background Technology

[0002] Ferrous sulfate, with the molecular formula FeSO4, is an analytical reagent used in chemical analysis. It can adjust the pH of alkaline water, organically combine with suspended solids in water, and accelerate precipitation. It is mainly used in water purification and industrial wastewater treatment, and also has bactericidal properties. Nickel sulfate, with the molecular formula NiSO4, is also an analytical reagent used in chemical analysis. It is mainly used in the electroplating industry, as it is the main nickel salt for electroplating nickel and electroless nickel plating, and also a source of metallic nickel ions. During electroplating, it can dissociate nickel ions and sulfate ions. In the production of hardened oils, it is a catalyst for the hydrogenation of oils and fats. In the pharmaceutical industry, it is used as a catalyst in the oxidation reaction of vitamin C production. In the inorganic industry, it is used as a main raw material for the production of other nickel salts such as nickel ammonium sulfate, nickel oxide, and nickel carbonate. In the printing and dyeing industry, it is used to produce phthalocyanine brilliant blue complexing agents and as a dyeing agent for vat dyes. Additionally, it can be used in the production of nickel-cadmium batteries.

[0003] Currently, methods for detecting ferrous sulfate and nickel sulfate include liquid chromatography, spectrophotometry, and electrochemical methods. However, most of these methods require large equipment and are expensive, making them unsuitable for on-site testing. Therefore, finding a detection and analysis method that is effective, easy to operate, and rapid is essential. Summary of the Invention

[0004] This invention aims to provide Fe metal ions 2+ and Ni 2+ A novel and convenient method for distinguishing different metal ions is provided, namely, a qualitative detection method using a "urease-CO(NH2)2-H2SO4" pH clock system as the distinguishing solution. This method is based on the different sensitivity responses of this 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 pH change over time is recorded. When the pH clock reaction begins, equal volumes of samples containing the same concentration of Fe metal ions are added... 2+ or Ni 2+ The sample solution (FeSO4 or NiSO4) to be distinguished is added to two sets of pH clock systems. Based on the different induction times of the sample to be distinguished to the pH clock system, the qualitative distinction of the sample to be distinguished is achieved.

[0005] The difference between this qualitative differentiation method and existing technologies lies in the application of a "urease-CO(NH2)2-H2SO4" pH clock system as the differentiating solution. The differentiation of samples is achieved based on the different induction times of the pH clock system produced by the samples to be differentiated. If the induction time of the pH clock is slightly prolonged after adding the differentiating solution, then the added sample contains Fe metal ions. 2+ If the induction time of the pH clock is significantly prolonged after adding the solution to be distinguished, then the added sample contains Ni metal ions. 2+ sample;

[0006] 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 20-30℃.

[0007] Metal ion Fe 2+ and Ni 2+ The distinguishable concentration range in the distinguishing solution (pH clock system) is 2.5 × 10⁻⁶. -5 -3.0×10 -5 mol / L.

[0008] The concentration range that the above-mentioned solutions can distinguish is the optimal concentration range determined experimentally. Within this concentration range, the metal ion Fe... 2+ and Ni 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.

[0009] Table 1: Concentration of each component in the pH clock system

[0010] Urease (U / mL) <![CDATA[CO(NH2)2(mol / L)]]> <![CDATA[H2SO 4 (mol / L)]]> 4-20 U / mL <![CDATA[1.5×10 -3 -4.0×10 -3 ]]> <![CDATA[1.0×10 -5 -3.5×10 -5 ]]>

[0011] Table 2: Optimal concentrations of each component in the pH clock system

[0012] Urease (U / mL) <![CDATA[CO(NH2) 2 (mol / L)]]> <![CDATA[H2SO 4 (mol / L)]]> 9.95 <![CDATA[1.86×10 -3 ]]> <![CDATA[1.43×10 -5 ]]>

[0013] The specific experimental steps are as follows:

[0014] 1. Prepare 40 mL of differentiating solution (pH clock system) according to the concentration range specified in Table 1, maintaining its temperature at a specific value between 20-30℃. Insert the prepared working electrode (pH composite electrode, Leici, E-331) into the solution. Connect the other end of the working electrode to a computer via a potential / temperature / pH integrated tester (Jiaxing Disheng Electronic Technology Co., Ltd., ZHFX-595). Open the chemical signal acquisition and analysis program on the computer, set the acquisition time and sampling speed, and quickly click the start button to monitor the pH of the solution. The computer records the collected pH change curve over time, i.e., the pH clock spectrum. When a substance needs to be detected, add the analyte immediately after the pH clock system reaction begins, and record the pH change over time in the same manner.

[0015] The basic parameters of a pH clock spectrum include:

[0016] Induction time: The time required from the start of the reaction in the pH clock system to the pH jump.

[0017] pH jump range: from the pH at which the pH jump begins to the pH at which the pH jump ends. Attached Figure Description

[0018] Figure 1 This is a graph showing the change in pH value of the distinguishing solution (pH clock system) over time when no sample to be distinguished was added, as shown in Example 1.

[0019] Figure 2 In Example 1, 2.5 × 10⁻⁶ was added. -5 After using mol / L FeSO4, a graph showing the change in pH value of the solution (pH clock system) over time was obtained.

[0020] Figure 3 In Example 1, 2.5 × 10⁻⁶ was added. -5 After using mol / L NiSO4, a graph showing the change in pH value of the solution (pH clock system) over time was obtained.

[0021] Figure 4 This is a graph showing the change in pH value of the distinguishing solution (pH clock system) over time when no sample to be distinguished was added, as shown in Example 2.

[0022] Figure 5 In Example 2, 2.75 × 10⁻⁶ was added. -5 After using mol / L FeSO4, a graph showing the change in pH value of the solution (pH clock system) over time was obtained.

[0023] Figure 6 In Example 2, 2.75 × 10⁻⁶ was added. -5After using mol / L NiSO4, a graph showing the change in pH value of the solution (pH clock system) over time was obtained.

[0024] Figure 7 This is a graph showing the change in pH value of the distinguishing solution (pH clock system) over time when no sample to be distinguished was added, as shown in Example 3.

[0025] Figure 8 In Example 3, 3.0 × 10 -5 After using mol / L FeSO4, a graph showing the change in pH value of the solution (pH clock system) over time was obtained.

[0026] Figure 9 In Example 3, 3.0 × 10 -5 After using mol / L NiSO4, a graph showing the change in pH value of the solution (pH clock system) over time was obtained. Implementation Example 1

[0027] This embodiment verifies the invention regarding the metal ion Fe according to the following steps. 2+ and Ni 2+ Feasibility of the differentiation method:

[0028] (1) Preparation of differentiating solutions

[0029] First, prepare 0.005 mol / L CO(NH2)2 solutions and 1.1 × 10⁻⁶ solutions using distilled water. -4 A solution of 1.1 × 10⁻⁶ mol / L H₂SO₄ and a solution of 20 U / mL urease were added sequentially to a 50 mL beaker. -4 14.7 mL of 0.005 mol / L H2SO4 solution, 19.8 mL of 20 U / mL urease solution were used to ensure that the concentration of each component in the "urease-CO(NH2)2-H2SO4" pH clock system was 1.51 × 10⁻⁶ H2SO4. -5 mol / L, CO(NH2)2 1.84×10 -3 The concentration of the reagent was mol / L, the urease concentration was 9.9 U / mL, the total volume was 40 mL, and the temperature was controlled at 23℃.

[0030] Simultaneously, using distilled water as a solvent, a series of solutions containing Fe metal ions of different concentrations were prepared. 2+ or Ni 2+ The sample solution to be distinguished (FeSO4 solution or NiSO4 solution).

[0031] (2) Obtain pH clock spectrum

[0032] The pH value of the prepared differentiating solution (pH clock system) over time was plotted by a computer equipped with a chemical signal acquisition and analysis program (without the sample to be tested added). For example... Figure 1 As shown, the pH induction time was 100 s as a blank control. Two additional groups of differentiating solutions were prepared with the same concentrations of each component as the aforementioned differentiating solutions. For one group, at the start of the reaction, 40 μL of 0.025 mol / L FeSO4 sample solution was added to a 40 mL pH clock system, making its concentration in the differentiating solution 2.5 × 10⁻⁶. -5 The addition of mol / L FeSO4 extended the induction time to 119 s. Figure 2 As shown; for the other group, at the start of the reaction, 40 μL of 0.025 mol / L NiSO4 sample solution was added to a 40 mL pH clock system, so that the concentration of NiSO4 in the distinguishing solution was 2.5 × 10⁻⁶. -5 The addition of NiSO4 at a concentration of mol / L changed the induction time to 163 s. Figure 3 As shown.

[0033] (3) Distinguish

[0034] Because FeSO4 and NiSO4 contain different metal ions, their effects on the induction time of the pH clock system also differ. (Comparison) Figure 1 , Figure 2 , Figure 3 It can be seen that the addition of FeSO4 slightly prolongs the induction time of the pH clock compared to the induction time without the sample; the addition of NiSO4 significantly prolongs the induction time of the pH clock compared to the induction time without the sample. From the above experiments, it can be concluded that by comparing the changes in the induction time of the pH clock system, the induction time of the metal ion Fe can be determined. 2+ and Ni 2+ The distinction.

[0035] Take two pre-prepared 0.025 mol / L solutions of the samples to be distinguished (one is FeSO4 solution, and the other is NiSO4 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 40 μL of 0.025 mol / L Sample 1 and Sample 2 to each solution, so that their concentrations in the distinguishing solutions are 2.5 × 10⁻⁶. -5 mol / L.

[0036] Analysis and comparison show that the addition of sample 1 slightly prolongs the induction time of the pH clock system (induction time and...). Figure 2 Corresponding to, and Figure 3(Not corresponding), while the addition of sample 2 significantly prolonged the induction time of the pH clock system (induction time and...). Figure 3 Corresponding to, and Figure 2 (Not corresponding). Therefore, sample 1 is a FeSO4 solution and sample 2 is a NiSO4 solution, thus achieving the desired effect on the metal ions Fe. 2+ and Ni 2+ The distinction. Example 2

[0037] This embodiment verifies the invention regarding the metal ion Fe according to the following steps. 2+ and Ni 2+ Feasibility of the differentiation method:

[0038] (1) Preparation of differentiating solutions

[0039] First, prepare 0.005 mol / L CO(NH2)2 solutions and 1.1 × 10⁻⁶ solutions using distilled water. -4 A solution of 1.1 × 10⁻⁶ mol / L H₂SO₄ and a solution of 20 U / mL urease were added sequentially to a 50 mL beaker. -4 14.9 mL of 0.005 mol / L H2SO4 solution, 19.3 mL of 20 U / mL urease solution were used to ensure that the concentration of each component in the "urease-CO(NH2)2-H2SO4" pH clock system was 1.60 × 10⁻⁶ H2SO4. -5 mol / L, CO(NH2)2 1.86×10 -3 The concentration of the reagent was mol / L, the urease concentration was 9.65 U / mL, the total volume was 40 mL, and the temperature was controlled at 23℃.

[0040] Simultaneously, using distilled water as a solvent, a series of solutions containing Fe metal ions of different concentrations were prepared. 2+ or Ni 2+ The sample solution to be distinguished (FeSO4 solution or NiSO4 solution).

[0041] (2) Obtain pH clock spectrum

[0042] The pH value of the prepared differentiating solution (pH clock system) over time was plotted by a computer equipped with a chemical signal acquisition and analysis program (without the sample to be tested added). For example... Figure 4 As shown. The pH induction time was 101 s as a blank control. Two additional groups of differentiating solutions were prepared with the same concentrations of each component as the above-mentioned differentiating solutions. For one group, at the start of the reaction, 40 μL of 0.0275 mol / L FeSO4 sample solution was added to a 40 mL pH clock system, so that its concentration in the differentiating solution was 2.75 × 10⁻⁶.-5 The addition of FeSO4 at a concentration of mol / L extended the induction time to 123 s. Figure 5 As shown; for the other group, at the start of the reaction, 40 μL of 0.0275 mol / L NiSO4 sample solution was added to a 40 mL pH clock system, so that the concentration of NiSO4 in the distinguishing solution was 2.75 × 10⁻⁶. -5 The addition of NiSO4 at a concentration of mol / L changed the induction time to 178 s. Figure 6 As shown.

[0043] (3) Distinguish

[0044] Because FeSO4 and NiSO4 contain different metal ions, their effects on the induction time of the pH clock system also differ. (Comparison) Figure 4 , Figure 5 , Figure 6 It can be seen that the addition of FeSO4 slightly prolongs the induction time of the pH clock compared to the time without the analyte; while the addition of NiSO4 significantly prolongs the induction time of the pH clock compared to the time without the analyte. From the above experiments, it can be concluded that by comparing the changes in the induction time of the pH clock system, the induction time of the metal ion Fe can be determined. 2+ and Ni 2+ The distinction.

[0045] Take two pre-prepared 0.0275 mol / L solutions of the samples to be distinguished (one is FeSO4 solution, and the other is NiSO4 solution, but they have not yet been distinguished). Label one as Sample 1 and the other as Sample 2. Prepare two sets of detection solutions with the same concentrations of each component as described above, and add 40 μL of 0.0275 mol / L Sample 1 and Sample 2 to each solution, so that their concentrations in the distinguishing solutions are 2.75 × 10⁻⁶. -5 mol / L.

[0046] Analysis and comparison show that the addition of sample 1 slightly prolongs the induction time of the pH clock system (induction time and...). Figure 5 Corresponding to, and Figure 6 (Not corresponding), while the addition of sample 2 significantly prolonged the induction time of the pH clock system (induction time and...). Figure 6 Corresponding to, and Figure 5 (Not corresponding). Therefore, sample 1 is a FeSO4 solution and sample 2 is a NiSO4 solution, thus achieving the desired effect on the metal ions Fe. 2+ and Ni 2+ The distinction. Example 3

[0047] This embodiment verifies the invention regarding the metal ion Fe according to the following steps. 2+ and Ni 2+ Feasibility of the differentiation method:

[0048] (1) Preparation of differentiating solutions

[0049] First, prepare 0.005 mol / L CO(NH2)2 solutions and 1.1 × 10⁻⁶ solutions using distilled water. -4 A solution of 1.1 × 10⁻⁶ mol / L H₂SO₄ and a solution of 20 U / mL urease were added sequentially to a 50 mL beaker. -4 14.9 mL of 0.005 mol / L H2SO4 solution, 19.9 mL of 20 U / mL urease solution were used to ensure that the concentration of each component in the "urease-CO(NH2)2-H2SO4" pH clock system was 1.43 × 10⁻⁶ H2SO4. -5 mol / L, CO(NH2)2 1.86×10 -3 The concentration of the reagent was mol / L, the urease concentration was 9.95 U / mL, the total volume was 40 mL, and the temperature was controlled at 23℃.

[0050] Simultaneously, using distilled water as a solvent, a series of solutions containing Fe metal ions of different concentrations were prepared. 2+ or Ni 2+ The sample solution to be distinguished (FeSO4 solution or NiSO4 solution).

[0051] (2) Obtain pH clock spectrum

[0052] The pH value of the prepared differentiating solution (pH clock system) over time was plotted by a computer equipped with a chemical signal acquisition and analysis program (without the sample to be tested added). For example... Figure 7 As shown. The pH induction time was 104 s as a blank control. Two additional groups of differentiating solutions were prepared with the same concentrations of each component as the above-mentioned differentiating solutions. For one group, at the start of the reaction, 40 μL of 0.030 mol / L FeSO4 sample solution was added to a 40 mL pH clock system, so that its concentration in the differentiating solution was 3.0 × 10⁻⁶. -5 The addition of mol / L FeSO4 extended the induction time to 127 s. Figure 8 As shown; for the other group, at the start of the reaction, 40 μL of 0.030 mol / L NiSO4 sample solution was added to a 40 mL pH clock system, so that the concentration of NiSO4 in the distinguishing solution was 3.0 × 10⁻⁶. -5 The addition of NiSO4 at a concentration of mol / L changed the induction time to 197 s. Figure 9 As shown.

[0053] (3) Distinguish

[0054] Because FeSO4 and NiSO4 contain different metal ions, their effects on the induction time of the pH clock system also differ. (Comparison) Figure 7 , Figure 8 , Figure 9 It can be seen that the addition of FeSO4 slightly prolongs the induction time of the pH clock compared to the induction time without the analyte; while the addition of NiSO4 significantly prolongs the induction time of the pH clock compared to the induction time without the analyte. From the above experiments, it can be concluded that by comparing the changes in the induction time of the pH clock system, the induction time of the metal ion Fe can be determined. 2+ and Ni 2+ The distinction.

[0055] Take two pre-prepared 0.030 mol / L solutions of the samples to be distinguished (one is FeSO4 solution, and the other is NiSO4 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, and add 40 μL of 0.030 mol / L Sample 1 and Sample 2 to each solution, so that their concentrations in the distinguishing solutions are 3.0 × 10⁻⁶. -5 mol / L.

[0056] Analysis and comparison show that the addition of sample 1 slightly prolongs the induction time of the pH clock system (induction time and...). Figure 8 Corresponding to, and Figure 9 (Not corresponding), while the addition of sample 2 significantly prolonged the induction time of the pH clock system (induction time and...). Figure 9 Corresponding to, and Figure 8 (Not corresponding). Therefore, sample 1 is a FeSO4 solution and sample 2 is a NiSO4 solution, thus achieving the desired effect on the metal ions Fe. 2+ and Ni 2+ The distinction.

[0057] As can be seen from the above examples, the concentration is 2.5 × 10⁻⁶. -5 -3.0×10 -5 Fe in the range of mol / L 2+ and Ni 2+ All of them can be distinguished using the method of this invention.

Claims

1. A method for distinguishing metal ions Fe 2+ and Ni 2+ The method is characterized by: Using distilled water as a solvent, prepare Fe metal ions 2+ and Ni 2+ The sample solutions to be distinguished; A pH clock reaction system of "urease-CO(NH2)2-H2SO4" was used as the differentiating solution, and the pH value of the pH clock reaction system was recorded as a graph over time. The temperature of the pH clock reaction system was controlled at any specific temperature within the range of 20-30℃. When the pH clock reaction system started, equal volumes of Fe metal ions of the same concentration were added. 2+ or Ni 2+ The sample solutions to be distinguished were added to two pH clock systems. The differentiation of the sample solutions was based on the different induction times of the pH clock reaction caused by the sample solutions: if the induction time of the pH clock was slightly prolonged after adding the sample solution, then the added sample solution contained Fe ions. 2+ Sample solution; if the induction time of the pH clock is significantly prolonged after adding the sample solution to be distinguished, then the added sample solution contains Ni metal ions. 2+ Sample solution; the induction time is the time required from the start of the reaction in the pH clock reaction system to the pH jump; The molar concentration ranges for different components in the solution are: urease 4-20 U / mL, CO(NH2)2 1.5 × 10⁻⁶. -3 -4.0×10 - 3 mol / L, H2SO4 1.0×10 -5 -3.5×10 -5 mol / L; The distinguishable concentration range of the sample solution to be distinguished in the distinguishing solution is 2.5 × 10⁻⁶. -5 -3.0×10 -5 mol / L.

2. The method according to claim 1, characterized in that: The molar concentrations of the components in the solution were distinguished as follows: urease 9.95 U / mL, CO(NH2)2 1.86 × 10⁻⁶. -3 mol / L, H2SO4 1.43×10 -5 mol / L.

3. The method according to claim 1, characterized in that: The clock system temperature is controlled at 23℃.

Images