Novel cobalt ion high-sensitivity and high-selectivity color developing agent and application thereof

Abstract

The invention discloses a novel cobalt ion high-sensitivity and high-selectivity color developing agent and application thereof.The structural formula of the novel cobalt ion color developing agent is shown in the specification, the azo color developing agent shows specific detection on Co < 2 + > in 17 metal recognition detection, a buffer solution and a surface active agent are added into a solution to be detected, and the cobalt ion high-sensitivity and high-selectivity color developing agent is obtained. Co2 + in the solution and the color developing agent generate a stable orange complex in an acid environment, the maximum absorption wavelength of the cobalt complex is 426 nm, the detection limit of cobalt is 5 * 10 <-3 > mg / L, the detection limit is 1 * 10 <-2 > mg / L, the detection limit is low, and the sensitivity is high. According to the method, the cobalt ions are detected by adopting a spectrophotometric method, the color developing agent compound belongs to an environment-friendly material, environmental pollution cannot be caused in the detection process, large instruments and equipment do not need to be relied on, and the method is simple to operate, efficient and convenient. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the field of heavy metal ion detection, and in particular relates to a novel cobalt ion highly sensitive and highly selective color developer and application thereof. Background Art

[0002] With the progress of society and the development of industry, the serious damage of heavy metals to the environment on which humans depend for survival has attracted widespread attention. Pollution caused by some heavy metal ions such as cobalt, lead, and cadmium has posed a serious threat to human health in some areas. Cobalt is a toxic metal that is easily accumulated in organisms. When the heavy metal content absorbed and accumulated by the human body through water, air, food, etc. reaches a certain amount, it will cause anemia, neurological disorders, kidney damage and other diseases. Therefore, it is of great significance to monitor trace cobalt in environmental samples.

[0003] At present, the methods for heavy metal detection include atomic absorption spectroscopy, polarography, inductive coupling, ion mass spectrometry, etc. These methods involve large instruments, are costly, complex to operate, and difficult to popularize. The methods for determining cobalt in national standards include 5-chloro-2-(pyridylazo)-1,3-diaminobenzene spectrophotometry, graphite furnace atomic absorption spectrophotometry, and flame atomic absorption spectrophotometry. Among them, spectrophotometry has the advantages of simplicity, rapidity, high sensitivity, low cost, and easy promotion, and is widely used. However, the measurement results may be affected by many factors such as instrument status, operating environment, and sample preparation. Therefore, it is necessary to strictly control the experimental conditions to ensure the accuracy of the measurement results. Secondly, due to the limitations of sample morphology, spectrophotometry can process liquid samples, but for some solid samples or samples that require special treatment, additional steps or equipment may be required for measurement.

[0004] However, the existing detection methods for trace cobalt ions have strict requirements on test samples, require specific equipment, are cumbersome to operate, have high professional requirements, and the test location and duration are relatively fixed, making it difficult to achieve rapid detection. The test is significantly affected by cross-interference factors, and many Co 2+ The sensitivity and selectivity of the color developer are not high and it is easily interfered by other metal ions, such as Cu 2+ 、Zn 2 + These ions are common in industrial wastewater and the natural environment, and their presence significantly affects the Co 2+ Accuracy of detection. 2+ The detection limit of the color developer is usually not enough to meet the requirements of environmental monitoring, especially when it is necessary to monitor trace cobalt ions in environmental samples. Some color developers have poor stability in the environment and are easily affected by light and temperature changes, resulting in inaccurate and poor reproducibility of test results.

[0005] In order to make up for the shortcomings of the above-mentioned detection, the application scope of the new colorimetric agent for the determination of trace cobalt should be broadened so that the new colorimetric agent can be used in the determination of heavy metal ions in more fields. Summary of the invention

[0006] Purpose of the invention: In order to solve the above technical problems, the present invention aims to provide a new type of cobalt ion developer, containing Co 2+ Highly affinity coordination site, high sensitivity and selectivity, high stability, simple operation, can effectively detect Co in industrial wastewater 2+ content.

[0007] The present invention also provides a novel application of a highly sensitive and highly selective cobalt ion color developer, which has low instrument cost and high detection sensitivity and is a novel method for detecting heavy metal Co in the environment. 2+ The detection provides a new solution.

[0008] Technical solution: In order to achieve the above-mentioned purpose, the novel cobalt ion developer of the present invention has the structural formula as shown below:

[0009]

[0010] Wherein, the R is selected from

[0011] Preferably, the novel cobalt ion developer has the following structural formula:

[0012]

[0013] The preparation method of the novel cobalt ion developer of the present invention comprises the following steps:

[0014] The nitroso red salt and 2-aminothiazole are mixed, benzene is added, and the mixture is dissolved in glacial acetic acid. The reaction is continued by heating. The reaction mixture is cooled to room temperature, and ice water is added to quench the reaction. The generated precipitate is filtered, washed, purified and dried to obtain 2,7-disulfonic acid-3-hydroxy-4-(thiazole-2-diazo)naphthalene solid, which is the cobalt ion color developer.

[0015] The novel cobalt ion color developing agent of the present invention is used in detecting cobalt ions.

[0016] Preferably, the novel cobalt ion color developing agent is used in detecting cobalt ions in the environment.

[0017] Furthermore, the novel cobalt ion color developing agent is used in detecting cobalt ions in wastewater.

[0018] Furthermore, the process of detecting cobalt ions in water by the novel cobalt ion developer comprises the following steps:

[0019] (4) taking a sample to be tested and adding a buffer solution to adjust the pH value of the sample to be tested;

[0020] (5) adding a color developer and a surfactant to the test solution, mixing and then allowing to stand;

[0021] (6) After sufficient reaction, the absorbance is measured by spectrophotometry, and the measured absorbance value is matched to the standard curve to obtain the cobalt ion concentration of the sample to be tested.

[0022] Furthermore, the buffer solution in step (1) is an acetic acid-ammonium acetate-TKPP-KHP solution with a pH of 2 to 5.

[0023] Furthermore, the concentration of the developer in step (2) is 1 to 5 g / L.

[0024] Furthermore, the surfactant in step (2) is any one of Tween-80, CTMAB, OP-100, and OP-CTMAB, with a concentration of no more than 5% and an addition amount of 0.2-1.0 mL.

[0025] Furthermore, the standing time at room temperature in step (2) is 10 to 20 minutes.

[0026] The azo color developer provided by the present invention shows the ability to detect all twelve metals. 2+ Specific detection.

[0027] Optimization of measurement conditions: Optimize pH value, buffer solution type and concentration, microemulsion type and dosage, maximum absorption wavelength, measurement parameter settings and other conditions to obtain the best sensitivity, stability and specific selectivity.

[0028] Investigation of anti-interference ability: investigate the interference of other heavy metal ions besides cobalt on the analyte studied in the present invention, and establish specific and selective conditions for the detection of cobalt.

[0029] Repeatability study: Conduct tests on different batches of the same sample, examine the repeatability of the test results under the same conditions, and examine the stability of the test methods and reagents.

[0030] Method reliability investigation: The detection results of the present invention were compared with those of the standard solution to investigate the accuracy and precision of the present invention.

[0031] Using spectrophotometry, a standard curve is drawn according to the cobalt concentration of each cobalt standard solution and the absorbance value obtained by the corresponding standard solution to be tested as the ordinate and the concentration of cobalt ions as the abscissa;

[0032] Obtain the test solution, add a buffer solution after pretreatment to adjust the pH value of the test standard solution to 2-5;

[0033] Adding a color developer and a homogenizing agent to the test solution, mixing and letting stand for 10 to 20 minutes;

[0034] The liquid to be tested was subjected to a spectrophotometric method to detect the presence of Co 2+ The detection wavelength is 400-450nm;

[0035] After sufficient reaction, the absorbance is measured by spectrophotometry, and the measured absorbance value is matched to the standard curve to obtain the cobalt ion concentration of the sample to be tested.

[0036] Preferably, the preparation method of various reagents in the cobalt ion detection is:

[0037] (1) Preparation of the color developer solution: Weigh 0.1-0.5 g of 2,7-disulfonic acid-3-hydroxy-4-(thiazole-2-diazo)naphthalene, dissolve it in DMF, and prepare 100 mL of solution with a concentration of 1-5 g / L;

[0038] (2) Preparation of acetic acid-ammonium acetate-TKPP-KHP buffer solution: weigh 5-15 g ammonium acetate, 5-20 ml glacial acetic acid, 10-30 g potassium pyrophosphate, 1-5 g potassium hydrogen phthalate, add 100 g distilled water and stir to dissolve;

[0039] (3) Preparation of Tween-80 microemulsion: Tween-80 microemulsion amine mass ratio is prepared as Tween-80: n-heptane: n-butanol: deionized water = 0.1~2: 0.1~2: 0.1~8: 0.1~93.

[0040] Among them, other coexisting ions when determining cobalt ions include: Ag + Cr 2+ , Mn 2+ , Ca 2+ , Ba 2+ , Pb 2+ 、Cd 2+ , Hg 2+ 、Al 3+ , Fe 3+ 、Zn 2+ Mg 2+ , K + 、Ni 2+ 、Na + , Cu 2+ , at concentrations with Co 2+ When appropriate, they do not interfere with the determination.

[0041] Furthermore, the detected cobalt ion concentration is 0.01-1 mg / L.

[0042] The linear equation of the standard curve is y = 0.00038x + 0.64 (R 2 =0.99938), the detection limit of cobalt ion concentration was 0.01 mg / L, and the detection limit of cobalt ion concentration was 0.005 mg / L.

[0043] The invention uses acetic acid-ammonium acetate-TKPP-solution with pH=2-5 as a buffer solution, 2,7-disulfonic acid-3-hydroxy-4-(thiazole-2-diazo)naphthalene solution as a color developer, Tween-80 microemulsion as a surfactant, and adopts spectrophotometry to detect cobalt ions in an aqueous phase, wherein the detection range of cobalt ions is 0.01-1 mg / L, and the apparent molar absorption coefficient is 3.510*10 4 L / (mol·cm), the detection limit is about 5×10 -3 mg / L.

[0044] Design principle: The color developer provided by the present invention contains a plurality of nitrogen atoms in its structure, which is easy to react with the nitrogen-philic element Co 2+ The present invention has a well-designed molecular structure to make the color developer have good chemical stability and light stability, which ensures that the color developer can maintain stable color development characteristics under different environmental conditions (such as different temperatures and light conditions), avoids the influence of environmental factors on the test results, and improves the accuracy and repeatability of the test results.

[0045] The color developer provided by the present invention has a coordination site with a high affinity for cobalt ions and can form a stable complex with cobalt ions. This specific structural design significantly improves the sensitivity of the color developer to cobalt ions. When the concentration of cobalt ions changes, the absorbance changes greatly, thereby achieving high-sensitivity detection of low-concentration cobalt ions. The color developer not only has high sensitivity and high selectivity, but also is easy to operate and has good stability. It can effectively detect the cobalt ion content in water, and provides a new solution for environmental monitoring.

[0046] The current national standard for the determination of cobalt includes 5-chloro-2-(pyridylazo)-1,3-diaminobenzene spectrophotometry, graphite furnace atomic absorption spectrophotometry, and flame atomic absorption spectrophotometry. Among the existing methods, the detection limits of flame atomic absorption spectrophotometry and graphite furnace atomic absorption spectrophotometry are relatively low, but they involve large instruments, are costly, complex to operate, and difficult to popularize; the detection limit of cobalt in the 5-chloro-2-(pyridylazo)-1,3-diaminobenzene spectrophotometry is 0.036 mg / L, and the detection limit is 0.009 mg / L.

[0047] The current first-level cobalt emission standard stipulates that the cobalt content in wastewater shall not exceed 0.5 mg / L. However, some industries and regions now stipulate that the maximum emission limit of cobalt is less than 0.1 mg / L. Therefore, it is a significant task to research and develop a new non-toxic and highly sensitive spectrophotometric detection method for cobalt.

[0048] The developer provided by the present invention has a detection limit of 0.005 mg / L and a detection limit of 0.01 mg / L for cobalt under the best experimental conditions, and an apparent molar absorption coefficient of 3.510*10 4 L / (mol·cm), with low detection limit and high sensitivity, no environmental pollution will be caused during the detection process, no reliance on large-scale instruments and equipment is required, and the operation is simple, efficient and convenient.

[0049] The present invention has a carefully designed molecular structure so that its structure contains application functional groups composed of multiple nitrogen atoms, so that it has coordination sites with high affinity to cobalt ions and can form stable complexes with cobalt ions, thereby achieving high-sensitivity detection of low-concentration cobalt ions. It is also easy to operate, has good stability, and can effectively detect the cobalt ion content in water.

[0050] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0051] 1. The sensitivity of the color developer of the present invention is improved, and the new azo color developer has the same 2+ High affinity coordination site, able to bind Co 2+ The specific structural design significantly improves the color development agent to form a stable complex. 2+ sensitivity.

[0052] 2. The developer of the present invention has enhanced selectivity. By introducing a functional group with specific recognition ability, it can specifically bind to Co 2+ Reaction combination, good selectivity, other metal ions are less disturbed, such as: Na + , K + ,Mg 2+ When this method is used to detect cobalt ions, the interference of other metal ions in the sample can be eliminated, and the result is more reliable.

[0053] 3. The color developer of the present invention is easy to operate, does not need to rely on large-scale equipment and instruments, is easy to operate, takes a short time, is efficient and convenient, and has no strict requirements on the detection environment and time, thereby ensuring rapid determination.

[0054] 4. The detection limit of the color developer of the present invention is low. 2+ It can form stable complexes and cause obvious absorbance changes even at extremely low concentrations, thus achieving a concentration as low as 5×10 -3This feature makes the colorimetric reagent useful for detecting trace amounts of Co in the environment and industrial wastewater. 2+ , which is of great significance for environmental protection and human health monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 The color change diagram of the mixed solution of the developer and the cobalt ion-developer complex in the present invention (left: the developer prepared in the present invention, right: the cobalt ion-developer complex);

[0056] Figure 2 is the ultraviolet absorption spectrum of the developer of the present invention;

[0057] Figure 3 The ultraviolet absorption spectrum of the developer and the cobalt ion complex of the present invention;

[0058] Figure 4 The effects of different pH on NHS-Co 2+ The influence diagram of the complex, the color developer does not complex with the metal ions under alkaline conditions, wherein the buffer is acetic acid-ammonium acetate-TKPP-KHP buffer solution pH = 2, 3, 4, 5, 6, NHS concentration is 1-5g / L, Co 2+ The concentration is 1 mg / L; the concentration of each surfactant is not more than 5%;

[0059] Figure 5 Effect of surfactant and dosage on NHS-Co 2+ The absorbance effect diagram of the complex, in which the control is a solution without surfactant, wherein the buffer is acetic acid-ammonium acetate-TKPP-KHP buffer solution (15-25 mmol / L, pH=2-5), the NHS concentration is 1-5 g / L, and Co 2+ The concentration is 1 mg / L; the concentration of each surfactant is not more than 5%;

[0060] Figure 6 Effect of Tween-80 surfactant and its dosage on NHS-Co 2+ Absorbance influence diagram of the complex;

[0061] Figure 7 To determine the colorimetric agent and Co 2+ Job'plot diagram of combined mode;

[0062] Figure 8 As a color developer for Co 2+ Diagram of possible sensing mechanism;

[0063] Fig. 9 For NHS-Co 2+ Benesi-Hildebrand plot in aqueous solution;

[0064] Fig.10 It is the cobalt ion concentration (0.01-0.1 mg / L)-absorbance standard curve fitting diagram of the present invention;

[0065] Fig.11 It is the cobalt ion concentration (0.1-1 mg / L)-absorbance standard curve fitting diagram of the present invention;

[0066] Fig.12 It is the ultraviolet absorption spectrum diagram of the selectivity of the color developer to metal ions when different metal ions exist;

[0067] Fig.13 It is a bar graph of the selectivity of the color developer to metal ions in the presence of different metal ions at 426 nm;

[0068] Fig.14 This is the fitting diagram of the cobalt ion concentration-absorbance standard curve of the PAN color developer. DETAILED DESCRIPTION

[0069] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0070] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources. Experimental methods without specific conditions specified in the examples are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0071] The specific configuration of each reagent in the embodiment:

[0072] The method for preparing the color developer solution is as follows: weigh 0.2 g of 2,7-disulfonic acid-3-hydroxy-4-(thiazole-2-diazo)naphthalene, dissolve it in DMF, and prepare 100 mL of solution with a concentration of 2 g / L.

[0073] Preparation of acetic acid-ammonium acetate-TKPP-KHP buffer solution: weigh 10g ammonium acetate, 15ml glacial acetic acid, 20g potassium pyrophosphate, 4g potassium hydrogen phthalate, add 100g distilled water and stir to dissolve.

[0074] Preparation of Tween-80 microemulsion: Weigh 4 g of Tween-80, 3 g of n-heptane, 0.8 g of n-butanol, and 92.2 g of deionized water, mix and stir at room temperature for 30 min.

[0075] Preparation of CTMAB microemulsion: weigh 2 g of CTMAB, 1 g of n-heptane, 0.5 g of n-butanol, and 96.5 g of deionized water, mix them, and stir them at room temperature for 30 min.

[0076] Preparation of OP-100 microemulsion: Weigh 4.5 g of OP-100, 3 g of n-heptane, 1 g of n-butanol, and 91.5 g of deionized water, mix them, and stir them at room temperature for 30 minutes.

[0077] Preparation of CTMAB-OP microemulsion: weigh 2.5 g of OP-100, 2 g of CTMAB, 0.5 g of n-heptane, 2 g of n-butanol, and 93 g of deionized water, mix and stir at room temperature for 30 min.

[0078] Cobalt standard solution: Weigh 1.0000g of metallic cobalt (99.99%) and dilute it to 1L. The concentration of the resulting solution is 1 mg / mL. When used, dilute it to a solution of 1-5 mg / L.

[0079] Preparation of other coexisting ion solutions: Take high-grade pure nitrates or hydrochlorides of various metals, dissolve them with acid, and prepare aqueous solutions with a concentration of 10 mg / L.

[0080] Cobalt metal: analytical grade, Shanghai MacLean Biochemical Technology Co., Ltd., C850143

[0081] Tween-80: chemically pure, Shanghai BiDe Pharmaceutical Technology Co., Ltd., BD148605;

[0082] CTMAB: chemically pure, Shanghai BiDe Pharmaceutical Technology Co., Ltd., BD21539;

[0083] OP-100: chemically pure, Shanghai BiDe Pharmaceutical Technology Co., Ltd., BD146108.

[0084] Example 1

[0085] Mix 100 mg of nitroso red salt and 26.5 mg of 2-aminothiazole in a molar ratio of 1:1, add 1 ml of benzene, and dissolve in 30 ml of glacial acetic acid. Heat to 40°C and continue the reaction for 24 hours. After completion, the reaction mixture was cooled to room temperature, ice water was added to quench the reaction, and the generated precipitate was filtered, washed (using cold ethanol), separated and purified by silica gel column, CH3OH / CH2Cl2 (V:V=2:98) was used as eluent, and finally dried to obtain cobalt ion developer 2,7-disulfonic acid-3-hydroxy-4-(thiazole-2-diazolyl)naphthalene solid (NHS). The purity of the obtained product was 85%, the yield was 60%, and the results of nuclear magnetic resonance characterization of the obtained product were: 1H NMR (400MHz, DMSO-d6) δ8.44–8.33 (m, 2H), 8.09 (d, J=4.8Hz, 1H), 7.88 (dd, J=8.0, 2.4Hz, 2H), 7.74 (d, J=3.4Hz, 1H). Chemical Formula: C 13H9N3O7S3, Exact Mass: 414.96, the structure is shown below.

[0086]

[0087] Example 2

[0088] The application of azo colorimetric agents in the detection of cobalt ions includes the following steps:

[0089] (1) The 2,7-disulfonic acid-3-hydroxy-4-(thiazole-2-diazolyl)naphthalene (NHS) prepared in Example 1 is a yellow liquid (eg Figure 1 As shown on the left), Figure 2 As shown in the UV-visible spectrophotometer, there is an absorption peak at 389. 2+ ) has an orange-red complex NHS-Co 2+ Generate (such as Figure 1 As shown on the right) (that is, when 1 ml of 2 g / L color developer solution is added to 5 ml of 5 mg / L cobalt standard solution, an orange-red complex NHS-Co 2+ Generate), such as Figure 3 As shown, an absorption peak occurs at 410-430 nm.

[0090] (2) Determination of buffer solution: Prepare buffer solutions of different pH values, take 2 ml of each buffer solution, add 5 ml of 2 mg / L cobalt standard solution and 1 ml of 2 g / L color developer solution, respectively, dilute to 10 ml with deionized water, stand at room temperature for 15 min, and then measure with a UV spectrophotometer. Figure 4 As shown, in the buffer solution system of pH = 3, NHS-Co 2+ The absorbance value of the complex is the highest, and the buffer solution with pH = 3 is finally selected. Among them, the buffer solution is acetic acid-ammonium acetate-TKPP-KHP buffer solution (pH = 2, 3, 4, 5, 6), the NHS concentration is 2g / L, and the cobalt standard solution concentration is 2mg / L.

[0091] (3) Determination of surfactant: Four different types of microemulsions (surfactants) were prepared, namely Tween-80, CTMAB, OP-100, and CTMAB-OP. 1 ml of each type of surfactant and 1 ml of deionized water were taken. 5 ml of 2 mg / L cobalt standard solution, 2 ml of pH 3 acetic acid-ammonium acetate-TKPP-KHP buffer solution, and 1 ml of 2 g / L color developer solution were added. The volume was adjusted to 10 ml with deionized water. After standing at room temperature for 15 min, the solution was measured using a UV spectrophotometer. 2+ The complex solution was used as the control. Figure 5As shown, NHS-Co containing CTMAB, OP-100, and CTMAB-OP surfactants 2+ The absorbance of the complex was similar to that of the control NHS-Co 2+ The absorbance value of the complex was slightly increased, while the absorbance in 4% Tween-80 increased by 2 times compared with the control. Finally, 4% Tween-80 was selected as the surfactant.

[0092] (4) Take 0.2mL, 0.4mL, 0.6mL, 0.8mL, and 1.0mL of 4% Tween-80, add 5mL of 2mg / L cobalt standard solution, 2mL of pH=3 acetic acid-ammonium acetate-TKPP-KHP buffer solution, and 1mL of 2g / L color developer solution, respectively, dilute to 10mL with deionized water, stand at room temperature for 15min, and measure with a UV spectrophotometer. The results show that: Figure 6 As shown in the figure, when the dosage of 4% Tween-80 is 0.6mL, the absorbance is the maximum and stable. Therefore, the optimal dosage of 4% Tween-80 is 0.6mL.

[0093] Example 3

[0094] The color developer NHS prepared in Example 1 and Co 2+ The stoichiometric ratio was established by using Job's plot experimental analysis. 2+ When the number of moles (1 mol) is constant, the mole fraction of NHS is changed and the absorbance value is plotted. As the molar ratio of NHS increases, the absorbance tends to increase gradually, such as Figure 7 As shown, when the NHS and Co 2+ When the molar ratio of Co is 2:1, the absorbance changes significantly, indicating that 2+ The bonding ratio with NHS is 1:2. Based on the above facts, it is assumed that the azo color developer is effective for Co 2+ Possible sensing mechanisms, such as Figure 8 shown.

[0095] The binding constant measures the effectiveness of the color developer in coordinating with the metal ion. The binding constant Ka of the complexation reaction data was calculated using the Benesi-Hildebrand equation, such as Fig. 9 In aqueous solution, the absorbance value at 410-430nm is similar to that of Co 2+ The newly formed complex (NHS-Co 2+ ) in water was determined to have a binding constant of 6.24×10 7 M -1 , linear correlation coefficient R 2 =0.9989. The value of the binding constant indicates that the coloring agent and Co2+ A stable complex is formed between them.

[0096] Example 4

[0097] Prepare NHS color developer solution (concentration of 2 g / L), acetic acid-ammonium acetate-TKPP-KHP buffer solution (pH=3), 4% Tween-80 solution, and cobalt ion solutions of different concentrations for use. The optimal addition amount of each substance in Example 2 is used.

[0098] The absorbance of the mixed solution of cobalt ions and NHS colorimetric reagent with different concentrations was measured by spectrophotometry, and the NHS solution with the same concentration was measured as a blank control. The absorbance difference between the system solution containing different cobalt ion concentrations and the blank control system solution was used as the ordinate, and the concentration of cobalt ions was used as the abscissa to draw a standard curve; Fig.10 , Fig.11 As shown, the absorbance of the system solution containing different cobalt ion concentrations is used as the ordinate, and the concentration of cobalt ions is used as the abscissa to draw a standard curve; Fig.10 As shown, the standard curve equation for the cobalt ion concentration in the range of 0.01 to 0.1 mg / L is y=0.38x+0.08885(R 2 =0.98796); Fig.11 As shown, the standard curve equation for the cobalt ion concentration in the range of 0.1 to 1.0 mg / L is y=0.64x-0.00038(R 2 =0.99935), apparent molar absorption coefficient ε = 3.510*10 4 L / (mol·cm), the detection limit of cobalt ions is 5×10 -3 mg / L, detection limit is 1×10 -2 mg / L.

[0099] Example 5

[0100] Prepare 17 test solutions, each containing only 5 ml of Co 2+ 、Ag + Cr 2+ , Mn 2+ , Ca 2+ , Ba 2+ , Pb 2+ 、Cd 2+ , Hg 2+ 、Al 3+ , Fe 3+ 、Zn 2+ Mg 2+ , K + 、Ni 2+ 、Na + , Cu2+ , and the concentration of each metal ion is 5mg / L, 1ml 2g / L color developer solution prepared in Example 1, 2ml pH=3 acetic acid-ammonium acetate-TKPP-KHP buffer solution, 0.6ml 4% Tween-80 solution were added, and the volume was fixed to 10ml with deionized water. The color developer solution of equal concentration and without any metal ions was used as a blank solution. After standing at room temperature for 15min, it was measured using an ultraviolet spectrophotometer. The results showed that: Fig.12 As shown, the azo colorimetric reagent showed good performance in all 17 metal ion recognition tests for Co. 2+ Specific tests such as Fig.13 As shown in the figure, when different metal ions of the same concentration are added, NHS-Co 2+ The absorbance value of the ions increased significantly, and the binding effect between other ions and the color developer was significantly smaller. Only Co 2+ It can specifically bind to the color developing agent, which may be due to the fact that the color developing agent contains Co 2+ Highly affinity coordination sites make the color developer show Co 2+ Highly selective.

[0101] Example 6

[0102] Comparative study on the detection of cobalt in water by PAN method and NHS method

[0103] PAN spectrophotometry in the detection method of aluminum in water: Take 5 20.0mL stoppered colorimetric tubes, add 5ml of 0.200mg / L, 0.400mg / L, 0.600mg / L, 0.800mg / L, and 1.00mg / L cobalt standard solutions, respectively, add 0.6ml of 4% Tween-80 solution, 2ml of pH=5 acetic acid-ammonium acetate-TKPP-KHP buffer solution, and 1ml of 2g / L PAN color developer (CAS No.: 85-85-8) solution, respectively, and use a spectrophotometer to measure the absorbance of the standard solution to be detected at a wavelength of 580nm. Draw a standard curve according to the cobalt concentration of each cobalt standard solution and the absorbance obtained by the corresponding standard solution to be detected, as shown in FIG. Fig.14 As shown, the standard curve equation is y = 0.62x + 0.005 (R 2 =0.99258), apparent molar absorption coefficient ε = 3.284*10 4 L / (mol·cm).

[0104] A comparative study on the detection of cobalt ions in water by the PAN method and the NHS method found that the minimum detection limit of cobalt ions in water by the PAN method was 0.08 mg / L, while the minimum detection limit of cobalt ions in water by the NHS method was 0.005 mg / L. In addition, the fit and sensitivity of the NHS method were better than those of the PAN method. Comprehensive comparison showed that the NHS method had better overall effect.

Claims

1. A novel cobalt ion developer, characterized in that: The structural formula of the novel cobalt ion developer is as follows: Wherein, the R is selected from 2. The novel cobalt ion developer according to claim 1, characterized in that: The preferred structural formula of the novel cobalt ion developer is as follows:

3. A method for preparing the novel cobalt ion developer according to claim 1, characterized in that: The steps include: The nitroso red salt and 2-aminothiazole are mixed, benzene is added, and the mixture is dissolved in glacial acetic acid. The reaction is continued by heating. The reaction mixture is cooled to room temperature, and ice water is added to quench the reaction. The generated precipitate is filtered, washed, purified, and dried to obtain a cobalt ion color developer.

4. Use of the novel cobalt ion developer according to claim 1 in detecting cobalt ions.

5. The use according to claim 4, characterized in that: The novel cobalt ion color developing agent is used in detecting cobalt ions in the environment.

6. The use according to claim 4, characterized in that: The process of detecting cobalt ions comprises the following steps: (1) taking a sample to be tested and adding a buffer solution to adjust the pH value of the sample to be tested; (2) adding a color developer and a surfactant to the test solution, mixing and then allowing to stand; (3) After sufficient reaction, the absorbance is measured by spectrophotometry, and the measured absorbance value is matched to the standard curve to obtain the cobalt ion concentration of the sample to be tested.

7. The use according to claim 6, characterized in that: The buffer solution in step (1) is an acetic acid-ammonium acetate-TKPP-KHP solution with a pH of 2 to 6.

8. The use according to claim 6, characterized in that: The concentration of the developer in step (2) is 1 to 5 g / L.

9. The use according to claim 6, characterized in that: The surfactant in step (2) is any one of Tween-80, CTMAB, OP-100, and OP-CTMAB, with a concentration of no more than 5% and an addition amount of 0.2-1.0 mL.

10. The use according to claim 6, characterized in that: The standing time at room temperature in step (2) is 10 to 20 minutes.

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