A way to distinguish Co 2+ and Fe 2+ Method

Abstract

The present invention is a method for distinguishing Co 2+ and Fe 2+ The method uses the "urease-CO(NH2)2-H2SO4" pH clock reaction system as a distinguishing solution, using Co 2+ 、Fe 2+ The activity of the urease-catalyzed clock reaction is reduced to different levels, so that the induction time of the pH clock system produced by the samples to be differentiated is different, thereby achieving the differentiation of the samples to be differentiated. The pH spectrum provided by the differentiation method involved in the present invention is intuitive and can easily and quickly distinguish Co 2+ and Fe 2+ , and the equipment is simple, accurate, easy to operate and observe.

Description

Technical Field

[0001] The present invention relates to a differentiation method, specifically, establishing a "urease-CO(NH2)2-H2SO4" pH clock system, using Co 2+ 、Fe 2+ The method of reducing the activity of the urease-catalyzed clock reaction to different levels makes the induction time of the pH clock system of the samples to be differentiated different, thereby achieving differentiation of the samples to be differentiated, which belongs to the field of analytical chemistry. Background Art

[0002] Cobalt sulfate, with the molecular formula CoSO4, is an analytical reagent in chemical analysis. It is used in the manufacture of barometers, hydrometers, and wet / dry indicators in applied instrumentation. It is used as a colorant in the ceramics industry, a paint drier in the coatings industry, and as a foam stabilizer in beer in the brewing industry. It is used in the defense industry to manufacture gas masks and as a catalyst in chemical reactions. It is also used in the manufacture of invisible inks, cobalt chloride test paper, and color-changing silica gel.

[0003] Ferrous sulfate, with the molecular formula FeSO₄, is an analytical reagent used in chemical analysis. It can adjust the pH of alkaline water, organically bind to suspended solids in water, and accelerate precipitation. It is primarily used in water purification and industrial wastewater treatment, and also has a bactericidal effect.

[0004] Current methods for distinguishing cobalt and ferrous ions include liquid chromatography, spectrophotometry, and electrochemical methods. However, these methods often require large equipment and are expensive, making them unsuitable for on-site testing. Therefore, it is imperative to find a detection and analysis method that is both effective and simple to operate and rapid. Summary of the Invention

[0005] The present invention aims to 2+ and Fe 2+ A novel and convenient differentiation method is provided, which uses the "urease-CO(NH2)2-H2SO4" pH clock system as the differentiation solution, using Co 2+ 、Fe 2+ The activity of the urease-catalyzed clock reaction is reduced to different levels, so that the induction time of the samples to be differentiated on the pH clock system is different, thereby achieving the differentiation of the samples to be differentiated. Specifically, the "urease-CO(NH2)2-H2SO4" pH clock reaction system is used as the differentiation solution, and the pH value of the clock system is recorded over time; when the pH clock reaction starts, equal volumes of the same concentration of Co-containing solution are added to the two groups of pH clock systems. 2+ or Fe 2+ The sample solution to be differentiated is used to 2+ 、Fe 2+The activity of the urease-catalyzed clock reaction is reduced to different levels, so that the samples to be distinguished have different induction times on the pH clock system, thereby achieving the purpose of Co 2+ 、Fe 2+ Differentiation of samples to be differentiated: If the induction time of the pH clock is slightly extended after adding the solution to be differentiated, the sample to be differentiated contains Fe 2+ If the induction time of the pH clock is greatly extended after adding the solution to be differentiated, the sample to be differentiated is Co 2+ The present invention has a short sample processing time, simple and easy-to-control measurement conditions, and is easy to promote and apply.

[0006] The difference between this method and the prior art is that the present invention uses the "urease-CO(NH2)2-H2SO4" pH clock system as the differentiation solution, using Co 2+ 、Fe 2+ The activity of the urease-catalyzed clock reaction is reduced differently, so that the induction time of the pH clock system produced by the samples to be differentiated is different, thereby achieving differentiation of the samples to be differentiated.

[0007] Co 2+ 、Fe 2+ The concentration range of the differentiated solution (pH clock system) is 1.5×10 -5 mol / L -1×10 -4 mol / L.

[0008] Co 2+ 、Fe 2+ When detected and differentiated in the pH clock system, the temperature of the pH clock system is controlled at any specific temperature within the range of 20-30°C.

[0009] Using the above pH clock system, Co 2+ 、Fe 2+ The concentration range that can be distinguished is the optimal concentration range determined by experiment. In this concentration range, the induction time has an effect on the Co 2+ 、Fe 2+ In addition, the concentration range of each component in the pH clock system is shown in Table 1, and the optimal concentration of the pH clock system obtained after multiple experiments is shown in Table 2:

[0010] Table 1: Concentration range of components in the pH clock system

[0011] Urease (U / mL) <![CDATA[CO(NH2)2(mol / L)]]> <![CDATA[H2SO 4 (mol / L)]]> 4-20 U / mL <![CDATA[1×10 -3 -2.5×10 -3 ]]> <![CDATA[1.2×10 -5 -3×10 -5 ]]>

[0012] Table 2: Optimal concentrations of components in the pH clock system

[0013] Urease (U / mL) <![CDATA[CO(NH2) 2 (mol / L)]]> <![CDATA[H2SO 4 (mol / L)]]> 8 <![CDATA[1.875×10 -3 ]]> <![CDATA[1.375×10 -5 ]]>

[0014] The specific experimental steps are as follows:

[0015] 40 mL of a differentiating solution (pH clock system) was prepared according to the concentration range specified in Table 1. The temperature was maintained constant at a specific value between 20 and 30°C. A working electrode (pH combination electrode, Leici, E-331) was inserted into the solution. The other end of the working electrode was connected to a computer via a potential / temperature / pH integrated tester (Jiaxing Disheng Electronic Technology Co., Ltd., ZHFX-595). The chemical signal acquisition and analysis program was launched, the acquisition time and sampling rate were set, and the pH of the solution was monitored by clicking the start button. The computer recorded the pH change curve over time (i.e., pH clock spectrum) (at this point, the test sample had not yet been added) to serve as a blank control. To the differentiating solutions with the same component concentrations as in the blank control experiment, an equal volume of the sample to be differentiated was quickly added (at the same time as the pH clock system reaction began). The pH clock spectrum of the pH change over time was recorded in the same manner. Qualitative analysis of the samples to be differentiated was achieved based on their different responses to the pH clock system, i.e., different induction times. The details are as follows: If the induction time of the pH clock is slightly extended after adding the solution to be differentiated, then the sample to be differentiated contains Fe 2+ If the induction time of the pH clock is greatly extended after adding the solution to be differentiated, the sample to be differentiated is Co 2+ sample;

[0016] The basic parameters of the pH clock spectrum include:

[0017] Induction time: the time required from the start of the pH clock system reaction to the pH jump.

[0018] pH jump range: pH corresponding to the start of pH jump to pH corresponding to the end of pH jump. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the pH spectrum of the differentiation solution (pH clock system) in Example 1 when no sample to be differentiated is added.

[0020] Figure 2 In Example 1, 5.0×10 -5 mol / LCoSO4, the pH spectrum obtained by the pH clock system.

[0021] Figure 3 In Example 1, 5.0×10 -5 mol / L FeSO4, and the pH spectrum obtained by the pH clock system.

[0022] Figure 4This is the pH spectrum of the differentiation solution (pH clock system) in Example 2 when no sample to be differentiated is added.

[0023] Figure 5 In Example 2, 7.5×10 -5 mol / LCoSO4, the pH spectrum obtained by the pH clock system.

[0024] Figure 6 In Example 2, 7.5×10 -5 mol / L FeSO4, and the pH spectrum obtained by the pH clock system.

[0025] Figure 7 This is the pH spectrum of the differentiation solution (pH clock system) in Example 3 when no sample to be differentiated is added.

[0026] Figure 8 In Example 3, 1.0×10 -4 mol / LCoSO4, the pH spectrum obtained by the pH clock system.

[0027] Figure 9 In Example 3, 1.0×10 -4 mol / L FeSO4, and the pH spectrum obtained by the pH clock system. Implementation Method

[0028] Example

[0029] This example verifies the Co 2+ and Fe 2+ Feasibility of the differentiation method:

[0030] (1) Preparation of differentiation solution

[0031] First, distilled water was used to prepare 0.005 mol / L CO(NH2)2 solution, 1.1×10 -4 mol / L H2SO4 solution and 16U / mL urease solution. 5.0mL 1.1×10 -4 mol / L H2SO4 solution, 15mL 0.005mol / L CO(NH2)2 solution, and 20mL 16U / mL urease solution to ensure that the concentration of each component in the "urease-CO(NH2)2-H2SO4" pH clock system is H2SO4 1.375×10 -5 mol / L, CO(NH2)21.875×10 -3 mol / L, urease 8U / mL, the total volume was 40mL, and the temperature was controlled at 25℃.

[0032] At the same time, 0.01 mol / L CoSO4 solution and FeSO4 solution were prepared using distilled water as solvent.

[0033] (2) Obtaining pH clock map

[0034] The potential oscillation spectrum of the pH clock system is recorded by a computer equipped with the logger lite program. Figure 1 The pH profile of the above-mentioned differentiating solution without adding the test sample at a typical concentration, and the pH induction time was 104s as a blank control. For one group, at the beginning of the reaction, 200μL of 0.01mol / L CoSO4 sample solution was added to the 40mL pH clock system, so that the concentration of CoSO4 in the differentiating solution was 5×10 -5 mol / L, the addition of CoSO4 prolonged the induction time to 133s. Figure 2 For the other group, at the beginning of the reaction, 200 μL of 0.01 mol / L FeSO4 sample solution was added to the 40 mL pH clock system, so that the concentration of FeSO4 in the differentiation solution was 5×10 -5 mol / L, added FeSO4

[0035] The induction time becomes 129s. Figure 3 shown.

[0036] (3) Distinction

[0037] Sample Co to be distinguished 2+ 、Fe 2+ Different properties reduce the activity of urease-catalyzed clock reaction differently, so that the induction time of the pH clock system produced by the samples to be distinguished is different. 2+ and Fe 2+ Different responses to the pH clock system, i.e. different induction times, enable qualitative analysis of samples to be differentiated. Figure 1 、 Figure 2 、 Figure 3 It can be seen that the addition of CoSO4 makes the induction time of the pH clock significantly longer than that without the addition of the test sample; the addition of FeSO4 makes the induction time of the pH clock slightly longer than that without the addition of the test sample. 2+ and Fe 2+ distinction.

[0038] Take two pre-prepared 0.01 mol / L solutions of the samples to be differentiated (one is CoSO4 and the other is FeSO4, but the two have not yet been differentiated), mark one as sample 1 and the other as sample 2;

[0039] Prepare two groups of pH clock system solutions with the same concentration of each component as above. At the start of the reaction, add 200 μL of 0.01 mol / L sample 1 and sample 2 to the two groups of differentiating solutions with the same concentration of each component as above, respectively, so that their concentrations in the differentiating solutions are 5.0×10 -5 mol / L.

[0040] Analysis and comparison show that: the addition of sample 1 greatly prolongs the induction time of the system (pH clock spectrum and Figure 2 Corresponding to Figure 3 The addition of sample 2 slightly prolonged the induction time of the system (pH clock spectrum and Figure 3 Corresponding to Figure 2 Therefore, sample 1 is a CoSO4 solution and sample 2 is a FeSO4 solution, thereby achieving the distinction between CoSO4 solution and FeSO4 solution.

[0041] Example

[0042] This example verifies the Co 2+ and Fe 2+ Feasibility of the differentiation method:

[0043] (1) Preparation of differentiation solution

[0044] First, distilled water was used to prepare 0.005 mol / L CO(NH2)2 solution, 1.1×10 -4 mol / L H2SO4 solution and 16U / mL urease solution. 5.6mL 1.1×10 -4 mol / L H2SO4 solution, 14.4mL 0.005mol / L CO(NH2)2 solution, and 20mL 16U / mL urease solution to ensure that the concentration of each component in the "urease-CO(NH2)2-H2SO4" pH clock system is H2SO4 1.54×10 -5 mol / L, CO(NH2)21.8×10 -3 mol / L, urease 8U / mL, the total volume was 40mL, and the temperature was controlled at 25℃.

[0045] At the same time, 0.01 mol / L CoSO4 solution and FeSO4 solution were prepared using water as solvent.

[0046] Obtaining pH clock patterns

[0047] The potential oscillation spectrum of the pH clock system is recorded by a computer equipped with the logger lite program. Figure 4 The pH profile of the above-mentioned differentiating solution without adding the test sample at a typical concentration, and the pH induction time was 103s as a blank control. For one group, at the beginning of the reaction, 300μL of 0.01mol / L CoSO4 sample solution was added to the 40mL pH clock system, so that the concentration of CoSO4 in the differentiating solution was 7.0×10 -5 mol / L, the addition of CoSO4 prolonged the induction time to 147s. Figure 5 For the other group, at the beginning of the reaction, 300 μL of 0.01 mol / L FeSO4 sample solution was added to 40 mL of the pH clock system, so that the concentration of FeSO4 in the differentiation solution was 7.0×10 -5 mol / Lmol / L, the addition of FeSO4 makes the induction time become 135s. Figure 6 shown.

[0048] (3) Distinction

[0049] Sample Co to be distinguished 2+ 、Fe 2+ Different properties reduce the activity of urease-catalyzed clock reaction differently, so that the induction time of the pH clock system produced by the samples to be distinguished is different. 2+ and Fe 2+ Different responses to the pH clock system, i.e. different induction times, enable qualitative analysis of samples to be differentiated. Figure 4 、 Figure 5 、 Figure 6 It can be seen that the addition of CoSO4 makes the induction time of the pH clock significantly longer than that without the addition of the test sample; the addition of FeSO4 makes the induction time of the pH clock slightly longer than that without the addition of the test sample. 2+ and Fe 2+ distinction.

[0050] Take two pre-prepared 0.01 mol / L solutions of the samples to be differentiated (one is CoSO4 and the other is FeSO4, but the two have not yet been differentiated), mark one as sample 1 and the other as sample 2;

[0051] Prepare two groups of pH clock system solutions with the same concentration of each component as above. At the start of the reaction, add 300 μL of 0.01 mol / L sample 1 and sample 2 to the two groups of differentiating solutions with the same concentration of each component as above, respectively, so that their concentrations in the differentiating solutions are 7.5×10 -5 mol / L.

[0052] Analysis and comparison show that: the addition of sample 1 greatly prolongs the induction time of the system (pH clock spectrum and Figure 5 Corresponding to Figure 6 The addition of sample 2 slightly prolonged the induction time of the system (pH clock spectrum and Figure 6 Corresponding to Figure 5 Therefore, sample 1 is a CoSO4 solution and sample 2 is a FeSO4 solution, thereby achieving the distinction between CoSO4 solution and FeSO4 solution.

[0053] Example

[0054] This example verifies the Co 2+ and Fe 2+ Feasibility of the differentiation method:

[0055] (1) Preparation of differentiation solution

[0056] First, distilled water was used to prepare 0.005 mol / L CO(NH2)2 solution, 1.1×10 -4 mol / L H2SO4 solution and 16U / mL urease solution. 5.7mL 1.1×10 -4 mol / L H2SO4 solution, 15mL 0.005mol / L CO(NH2)2 solution, and 19.3mL 16U / mL urease solution to ensure that the concentration of each component in the "urease-CO(NH2)2-H2SO4" pH clock system is H2SO4 1.5675×10 -5 mol / L, CO(NH2)21.875×10 -3 mol / L, urease 7.72U / mL, the total volume was 40mL, and the temperature was controlled at 25℃.

[0057] At the same time, 0.01 mol / L CoSO4 solution and FeSO4 solution were prepared using water as solvent.

[0058] (2) Obtaining pH clock map

[0059] The potential oscillation spectrum of the pH clock system is recorded by a computer equipped with the logger lite program. Figure 7The pH profile of the above-mentioned differentiating solution without adding the test sample at a typical concentration, and the pH induction time was 101s as a blank control. For one group, at the beginning of the reaction, 400 μL of 0.01 mol / L CoSO4 sample solution was added to the 40 mL pH clock system, so that the concentration of CoSO4 in the differentiating solution was 1.0×10 -4 mol / L, the addition of CoSO4 extended the induction time to 160s. Figure 8 For the other group, at the beginning of the reaction, 400 μL of 0.01 mol / L FeSO4 sample solution was added to 40 mL of the pH clock system, so that the concentration of FeSO4 in the distinguishing solution was 1.0×10 -4 mol / L, the addition of FeSO4 makes the induction time become 152s. Figure 9 shown.

[0060] (3) Distinction

[0061] Sample Co to be distinguished 2+ 、Fe 2+ Different properties reduce the activity of urease-catalyzed clock reaction differently, so that the induction time of the pH clock system produced by the samples to be distinguished is different. 2+ and Fe 2+ Different responses to the pH clock system, i.e. different induction times, enable qualitative analysis of samples to be differentiated. Figure 7 、 Figure 8 、 Figure 9 It can be seen that the addition of CoSO4 makes the induction time of the pH clock significantly longer than that without the addition of the test sample; the addition of FeSO4 makes the induction time of the pH clock slightly longer than that without the addition of the test sample. 2+ and Fe 2+ distinction.

[0062] Take two pre-prepared 0.01 mol / L solutions of the samples to be differentiated (one is CoSO4 and the other is FeSO4, but the two have not yet been differentiated), mark one as sample 1 and the other as sample 2;

[0063] Prepare two groups of pH clock system solutions with the same concentration of each component as above. At the start of the reaction, add 400 μL of 0.01 mol / L sample 1 and sample 2 to the two groups of differentiating solutions with the same concentration of each component as above, respectively, so that their concentrations in the differentiating solutions are 1.0×10 -4 mol / L.

[0064] Analysis and comparison show that: the addition of sample 1 prolongs the induction time of the system to a small extent (pH clock spectrum and Figure 9 Corresponding to Figure 8 The addition of sample 2 significantly prolonged the induction time of the system (pH clock spectrum and Figure 8 Corresponding to Figure 9 Therefore, sample 1 is a FeSO4 solution and sample 2 is a CoSO4 solution, thereby achieving the distinction between CoSO4 solution and FeSO4 solution.

[0065] It can be seen from the above examples that the concentration is 1.5×10 -5 mol / L - 1×10 -4 Fe in the mol / L range 2 + and Co 2+ All of them can be distinguished by the method of the present invention.

Claims

1. A method to distinguish Co 2+ and Fe 2+ The method is characterized in that: Using distilled water as solvent, prepare CoSO4 solution and FeSO4 solution as sample solutions to be differentiated; The "urease-CO(NH2)2-H2SO4" pH clock system was used as the distinguishing solution, and the pH value of the clock system was recorded as it changed over time. The temperature of the pH clock system is controlled in the range of 20-30℃; when the pH clock reaction starts, equal volumes of the above-mentioned sample solutions of the same concentration are added to the two groups of pH clock systems respectively, and the Co 2+ 、Fe 2+ The activity of the urease-catalyzed clock reaction is reduced differently, so that the induction time of the sample to be differentiated on the pH clock system is different, thereby achieving the differentiation of CoSO4 and FeSO4 samples to be differentiated: if the induction time of the pH clock is slightly extended after the solution to be differentiated is added, then the added sample to be differentiated is FeSO4 solution; if the induction time of the pH clock is significantly extended after the solution to be differentiated is added, then the added sample to be differentiated is CoSO4 solution; the induction time is the time required from the start of the pH clock system reaction to the pH jump; The molar concentration ranges of the components in the solution were as follows: urease 4-20 U / mL, CO(NH2)2 1×10 -3 -2.5×10 - 3 mol / L, H2SO4 1.2×10 -5 -3×10 -5 mol / L.

2. The method according to claim 1, wherein: The molar concentrations of the components in the solution were urease 8U / mL, CO(NH2)2 1.875×10 -3 mol / L, H2SO4 1.375×10 -5 mol / L.

3. The method according to claim 1, wherein: The concentration range of the sample to be differentiated in the differentiation solution is 1.5×10 -5 mol / L-1×10 -4 mol / L.

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