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

Abstract

This invention discloses a novel cobalt ion highly sensitive and selective colorimetric reagent and its applications. The structural formula of the novel cobalt ion colorimetric reagent is shown below. The azo colorimetric reagent of this invention showed high sensitivity to Co in the detection of seventeen metals. 2+ For specific detection, a buffer solution and surfactant are added to the test solution, followed by the addition of a colorimetric reagent. The Co content in the solution... 2+ It forms a stable orange-red complex with the colorimetric reagent in an acidic environment. The maximum absorption wavelength of the cobalt complex is 426 nm, and the detection limit of cobalt is 5 × 10⁻⁶. ‑3 mg / L, detection limit is 1×10 ‑2 The detection limit is low and the sensitivity is high (mg / L). This invention uses spectrophotometry for cobalt ion detection, where the chromogenic compound is an environmentally friendly material that does not cause environmental pollution during the detection process. It does not require large instruments and equipment, and is simple, efficient, and convenient to operate.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal ion detection, and in particular relates to a novel cobalt ion highly sensitive and selective colorimetric reagent and its application. Background Technology

[0002] With social progress and industrial development, environmental pollution has become increasingly serious. The severe damage to the environment upon which humanity depends for survival caused by heavy metals has attracted widespread attention. Pollution caused by some heavy metal ions, such as cobalt, lead, and cadmium, has already posed a serious threat to human health in some areas. Cobalt is a toxic metal that easily accumulates in living organisms. When the amount of heavy metals absorbed and accumulated by the human body through water, air, and food reaches a certain level, it can cause diseases such as anemia, neurological dysfunction, and kidney damage. Therefore, monitoring trace amounts of cobalt in environmental samples is of great significance.

[0003] Currently, methods for detecting heavy metals include atomic absorption spectrometry, polarography, inductively coupled plasma mass spectrometry, and inductively coupled plasma mass spectrometry. These methods involve large instruments, are costly, complex to operate, and difficult to popularize. National standards specify methods for cobalt determination including 5-chloro-2-(pyridiniazo)-1,3-diaminobenzene spectrophotometry, graphite furnace atomic absorption spectrophotometry, and flame atomic absorption spectrophotometry. Spectrophotometry is widely used due to its simplicity, speed, high sensitivity, low cost, and ease of implementation. However, measurement results can be affected by various factors such as instrument condition, operating environment, and sample preparation. Therefore, strict control of experimental conditions is necessary to ensure the accuracy of measurement results. Furthermore, spectrophotometry is limited by sample form; while it can handle liquid samples, certain solid samples or samples requiring special treatment may require additional steps or equipment for measurement.

[0004] However, existing methods for detecting trace cobalt ions have stringent requirements for test samples, necessitating specific equipment, complex operations, and high levels of expertise. The testing locations and durations are relatively fixed, making rapid detection difficult. Furthermore, the tests are significantly affected by cross-interference factors, and many Co... 2+ The colorimetric reagent has low sensitivity and selectivity and is easily interfered with by other metal ions, such as Cu. 2+ Zn 2 + These ions are commonly found in industrial wastewater and the natural environment, and their presence significantly affects the levels of Co. 2+ The accuracy of the detection. Existing Co... 2+ The detection limits of chromogenic reagents are often insufficient to meet the requirements of environmental monitoring, especially when monitoring trace amounts of cobalt ions in environmental samples. Some chromogenic reagents are not very stable in the environment and are easily affected by changes in light and temperature, leading to inaccurate and poor reproducibility of detection results.

[0005] To address the shortcomings of the aforementioned detection methods and broaden the application scope of the new colorimetric reagent for the determination of trace cobalt, enabling the new colorimetric reagent to be used in the determination of heavy metal ions in more fields. Summary of the Invention

[0006] Purpose of the invention: To solve the above-mentioned technical problems, the present invention aims to provide a novel cobalt ion colorimetric agent containing a compound with Co. 2+ It possesses highly compatible coordination sites, exhibiting high sensitivity and selectivity, as well as high stability and simple operation, enabling effective detection of Co in industrial wastewater. 2+ content.

[0007] This invention also provides an application of a novel cobalt ion highly sensitive and selective colorimetric reagent, which features low instrument cost and high detection sensitivity, making it suitable for detecting heavy metals Co in the environment. 2+ The detection provides a new solution.

[0008] Technical solution: To achieve the above objectives, the present invention provides a novel cobalt ion colorimetric agent, the structural formula of which is shown below:

[0009]

[0010] Wherein, R is selected from or .

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

[0012] .

[0013] The preparation method of the novel cobalt ion colorimetric agent of the present invention includes the following steps:

[0014] Nitrosamine red salt and 2-aminothiazole were mixed, added to benzene, dissolved in glacial acetic acid, and heated to continue the reaction. The reaction mixture was cooled to room temperature and the reaction was quenched with ice water. The resulting precipitate was filtered, washed, purified and dried to obtain 2,7-disulfonic-3-hydroxy-4-(thiazole-2-diazyl)naphthalene solid, which is the cobalt ion colorimetric agent.

[0015] The novel cobalt ion colorimetric reagent described in this invention is used in the detection of cobalt ions.

[0016] Preferably, the novel cobalt ion colorimetric reagent is used in the detection of cobalt ions in the environment.

[0017] Furthermore, the novel cobalt ion colorimetric reagent is applied in the detection of cobalt ions in wastewater.

[0018] Furthermore, the novel cobalt ion colorimetric reagent includes the following steps in detecting cobalt ions in water:

[0019] (1) Take the sample to be tested and add buffer solution to adjust the pH value of the sample to be tested;

[0020] (2) Add colorimetric reagent and surfactant to the test solution, mix and let stand;

[0021] (3) After the reaction is complete, the absorbance is measured by spectrophotometry. The measured absorbance value is then mapped to the standard curve to obtain the cobalt ion concentration of the sample to be tested.

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

[0023] Further, the concentration of the colorimetric reagent in step (2) is 1~5 g / L.

[0024] Further, the surfactant mentioned 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 room temperature standing time in step (2) is 10~20 min.

[0026] The azo colorimetric reagent provided by this invention showed positive effects on Co in the detection of all twelve metals. 2+ Specific detection.

[0027] Measurement condition optimization: The pH value, buffer solution type and concentration, microemulsion type and amount, maximum absorption wavelength, and measurement parameter settings are optimized to obtain the best sensitivity, stability and specificity.

[0028] Anti-interference capability assessment: This study investigates the interference of other heavy metal ions besides cobalt on the analytes and establishes specific and selective conditions for the detection of cobalt.

[0029] Repeatability study: This involves testing different batches of the same sample under the same conditions to examine the repeatability of the test results and the stability of the testing methods and reagents.

[0030] Method reliability assessment: The detection results of this invention are compared with those of standard solutions to assess the accuracy and precision of this invention.

[0031] A standard curve was plotted using spectrophotometry, with the cobalt concentration of each cobalt standard solution and the absorbance value of the corresponding standard solution to be tested as the ordinate and the cobalt ion concentration as the abscissa.

[0032] Obtain the test solution, pretreat it, and then add a buffer solution to adjust the pH of the test standard solution to 2-5;

[0033] Add a colorimetric reagent and a homogenizing agent to the test solution, mix, and let stand for 10-20 minutes;

[0034] The test solution containing Co was analyzed by spectrophotometry. 2+ The detection wavelength is 400~450nm;

[0035] After the reaction is complete, the absorbance is measured by spectrophotometry. The measured absorbance value is then mapped to a standard curve to obtain the cobalt ion concentration of the sample.

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

[0037] (1) Preparation method of colorimetric reagent solution: Weigh 0.1~0.5g of 2,7-disulfonic-3-hydroxy-4-(thiazolyl-2-diazolium)naphthalene, dissolve it in DMF, and prepare a 100mL solution with a concentration of 1~5 g / L;

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

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

[0040] Other coexisting ions included in the determination of 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 concentration and Co 2+ When the conditions are similar, they do not interfere with the measurement.

[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 (R²). 2 =0.99938), the detection limit for cobalt ion concentration is 0.01 mg / L, and the detection limit for cobalt ion concentration is 0.005 mg / L.

[0043] This invention uses an acetic acid-ammonium acetate-TKPP solution with pH=2~5 as a buffer solution, a 2,7-disulfonic-3-hydroxy-4-(thiazolyl-2-diazolyl)naphthalene solution as a colorimetric reagent, and Tween-80 microemulsion as a surfactant. A spectrophotometric method is employed to detect cobalt ions in the aqueous phase, with a detection range of 0.01~1 mg / L and an apparent molar absorptivity of 3.510 × 10⁻⁶. 4 L / (mol·cm), detection limit is approximately 5×10 -3 mg / L.

[0044] Design Principle: The colorimetric agent provided by this invention contains multiple nitrogen atoms forming an application functional group, which readily reacts with the nitrogen-loving element Co. 2+ The reaction forms a stable complex. This invention, through a carefully designed molecular structure, endows the chromogenic agent with excellent chemical and photostability. This ensures that the chromogenic agent maintains stable colorimetric properties under different environmental conditions (such as different temperatures and light conditions), avoiding the influence of environmental factors on the detection results and improving the accuracy and repeatability of the detection results.

[0045] The colorimetric reagent provided by this invention has coordination sites with high affinity for cobalt ions, enabling it to form stable complexes with cobalt ions. This specific structural design significantly improves the sensitivity of the colorimetric reagent to cobalt ions.

[0046] When the cobalt ion concentration changes, the absorbance changes significantly, thus enabling high-sensitivity detection of low concentrations of cobalt ions. This method not only has high sensitivity and selectivity, but is also simple to operate and has good stability, effectively detecting the cobalt ion content in water and providing a new solution for environmental monitoring.

[0047] The current national standards for cobalt determination include the 5-chloro-2-(pyridiniazo)-1,3-diaminobenzene spectrophotometric method, graphite furnace atomic absorption spectrophotometry, and flame atomic absorption spectrophotometry. Among the existing methods, flame atomic absorption spectrophotometry and graphite furnace atomic absorption spectrophotometry have low detection limits, but they involve large instruments, are costly, complex to operate, and difficult to popularize. The detection limit for cobalt in the 5-chloro-2-(pyridiniazo)-1,3-diaminobenzene spectrophotometric method is 0.036 mg / L, and the detection limit is 0.009 mg / L.

[0048] The current Class I emission standard for cobalt 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 for cobalt is less than 0.1 mg / L. Therefore, researching and developing a new non-toxic and highly sensitive spectrophotometric detection method for cobalt is a work of great significance.

[0049] The colorimetric reagent provided by this invention, under optimal experimental conditions, has a detection limit of 0.005 mg / L for cobalt, a detection limit of 0.01 mg / L, and an apparent molar absorptivity of 3.510 × 10⁻⁶. 4 With a detection limit of L / (mol·cm), low detection limit, and high sensitivity, the detection process does not cause environmental pollution, does not require large instruments and equipment, and is simple, efficient, and convenient to operate.

[0050] This invention utilizes a carefully designed molecular structure containing multiple nitrogen atoms as functional groups, thus providing coordination sites with high affinity for cobalt ions. This allows for the formation of stable complexes with cobalt ions, enabling highly sensitive detection of low concentrations of cobalt ions. Furthermore, the invention is simple to operate, has good stability, and can effectively detect the cobalt ion content in water.

[0051] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0052] 1. The colorimetric reagent of this invention has improved sensitivity, and the novel azo colorimetric reagent exhibits similarity to Co. 2+ Highly compatible coordination sites are able to bind with Co. 2+ This specific structural design, which forms a stable complex, significantly improves the chromogenic agent's response to Co. 2+ Sensitivity.

[0053] 2. The colorimetric reagent of this invention exhibits enhanced selectivity by introducing functional groups with specific recognition capabilities, enabling it to specifically bind to Co. 2+ The reaction combines well with good selectivity, and other metal ions are minimally affected, such as Na. + K + Mg 2+ When using this method to detect cobalt ions, interference from other metal ions in the sample can be eliminated, resulting in more reliable results.

[0054] 3. The colorimetric reagent of this invention is simple to operate, does not rely on large equipment and instruments, is simple to operate, takes little time, is efficient and convenient, and has no strict requirements on the detection environment and time, thus ensuring rapid determination.

[0055] 4. The colorimetric reagent of this invention has a low detection limit. This invention is due to the colorimetric reagent reacting with Co. 2+ It can form stable complexes and cause significant absorbance changes even at extremely low concentrations, thus achieving absorbance as low as 5 × 10⁻⁶.-3 The detection limit is mg / L. This characteristic allows the colorimetric reagent to be used to detect trace amounts of Co in environmental and industrial wastewater. 2+ This is of great significance for environmental protection and human health monitoring. Attached Figure Description

[0056] Figure 1 The color change diagrams of the mixed solution of the color developer and the cobalt ion-color developer complex in this invention are shown (left: the color developer prepared in this invention, right: the cobalt ion-color developer complex).

[0057] Figure 2 This is the ultraviolet absorption spectrum of the colorimetric reagent of this invention;

[0058] Figure 3 The image shows the ultraviolet absorption spectrum of the colorimetric reagent and cobalt ion complex of this invention.

[0059] Figure 4 For different pH values ​​of NHS-Co 2+ The effect of complexation is shown in the diagram. The chromogenic agent does not complex with metal ions under alkaline conditions. The buffer solution is an acetate-ammonium acetate-TKPP-KHP buffer solution with pH values ​​of 2, 3, 4, 5, and 6. The NHS concentration is 1–5 g / L. Co… 2+ The concentration was 1 mg / L; the concentration of each surfactant was no greater than 5%.

[0060] Figure 5 The effect of microemulsion surfactants and their dosage on NHS-Co 2+ The absorbance effect of the complex is shown in the figure. The control in the figure is a solution without surfactant. The buffer solution is an acetate-ammonium acetate-TKPP-KHP buffer solution (15~25 mmol / L, pH= 2~5), the NHS concentration is 1~5 g / L, and the Co concentration is... 2+ The concentration was 1 mg / L; the concentration of each surfactant was no greater than 5%.

[0061] Figure 6 The effect of Tween-80 surfactant and its dosage on NHS-Co 2+ The effect of the complex on absorbance;

[0062] Figure 7 To determine the colorimetric reagent and Co 2+ Combine the job's plot with the pattern;

[0063] Figure 8 For colorimetric reagents to Co 2+ Possible sensing mechanism diagram;

[0064] Figure 9 For NHS-Co 2+Benesi-Hildebrand diagram in aqueous solution;

[0065] Figure 10 This is a fitting graph of the standard curve of cobalt ion concentration (0.01-0.1 mg / L)-absorbance in this invention;

[0066] Figure 11 This is a fitting graph of the standard curve of cobalt ion concentration (0.1-1 mg / L)-absorbance in this invention;

[0067] Figure 12 The UV absorption spectra of the colorimetric reagents selectively reacting with metal ions in the presence of different metal ions.

[0068] Figure 13 The bar chart shows the selectivity of the chromogenic agent to metal ions in the presence of different metal ions at 426 nm.

[0069] Figure 14 This is a fitting graph of the cobalt ion concentration-absorbance standard curve for the PAN colorimetric reagent. Detailed Implementation

[0070] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0071] Unless otherwise specified, all materials and reagents used in the following examples are commercially available. Experimental methods not specifically described in the examples are generally performed under standard conditions or as recommended by the manufacturer.

[0072] The specific configurations of each reagent in the examples are as follows:

[0073] Preparation method of colorimetric reagent solution: Weigh 0.2g of 2,7-disulfonic-3-hydroxy-4-(thiazolyl-2-diazolium)naphthalene, dissolve it in DMF, and prepare a 100mL solution with a concentration of 2g / L.

[0074] Preparation of acetic acid-ammonium acetate-TKPP-KHP buffer solution: Weigh 10g ammonium acetate, 15ml glacial acetic acid, 20g potassium pyrophosphate, and 4g potassium hydrogen phthalate, add 100g distilled water and stir to dissolve.

[0075] Preparation of Tween-80 microemulsion: Weigh 4g of Tween-80, 3g of n-heptane, 0.8g of n-butanol, and 92.2g of deionized water, mix them, and stir at room temperature for 30 minutes.

[0076] Preparation of CTMAB microemulsion: Weigh 2g of CTMAB, 1g of n-heptane, 0.5g of n-butanol, and 96.5g of deionized water, mix them, and stir at room temperature for 30 minutes.

[0077] 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 at room temperature for 30 min.

[0078] 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 them, and stir at room temperature for 30 min.

[0079] Cobalt standard solution: Weigh 1.0000g of metallic cobalt (99.99%) and dilute it to 1L. The resulting solution concentration is 1mg / mL. Dilute to 1~5mg / L before use.

[0080] Preparation of solutions for other coexisting ions: Take the nitrates or hydrochlorides of various metals of superior purity, dissolve them in acid, and prepare an aqueous solution with a concentration of 10 mg / L.

[0081] Cobalt metal: analytical grade, Shanghai Maclean Biochemical Technology Co., Ltd., C850143

[0082] Tween -80: Chemically pure, Shanghai Bid Pharmaceutical Technology Co., Ltd., BD148605;

[0083] CTMAB: Chemically pure, Shanghai Bid Pharmaceutical Technology Co., Ltd., BD21539;

[0084] OP-100: Chemically pure, Shanghai Bid Pharmaceutical Technology Co., Ltd., BD146108.

[0085] Example 1

[0086] Mix 100 mg of nitrosored 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, and the reaction was quenched with ice water. The resulting precipitate was filtered, washed (using cold ethanol), purified by silica gel column chromatography using CH3OH / CH2Cl2 (V:V = 2:98) as the eluent, and finally dried to obtain the cobalt ion colorimetric reagent 2,7-disulfonic-3-hydroxy-4-(thiazolyl-2-diazonyl)naphthalene solid (NHS). The purity of the product was 85%, and the yield was 60%. The NMR characterization results of the product were as follows: 1H NMR (400 MHz, DMSO-d6) δ 8.44 – 8.33 (m, 2H), 8.09 (d, J = 4.8 Hz, 1H), 7.88 (dd, J = 8.0, 2.4 Hz, 2H), 7.74 (d, J = 3.4 Hz, 1H). Chemical Formula: C 13 H9N3O7S3, Exact Mass: 414.96, has the following structure.

[0087]

[0088] Example 2

[0089] The application of azo colorimetric reagents in the detection of cobalt ions includes the following steps:

[0090] (1) The 2,7-disulfonic-3-hydroxy-4-(thiazolyl-2-diazo)naphthalene (NHS) prepared in Example 1 is itself a yellow liquid (e.g. Figure 1 (As shown on the left), as Figure 2 As shown, an absorption peak is observed at 389 nm under UV-Vis spectrophotometry. This peak is observed when cobalt ions (Co) are added. 2+ Occasionally, an orange-red complex NHS-Co is present. 2+ Generate (e.g.) Figure 1 (As shown on the right) (that is, when 1 ml of 2 g / L colorimetric reagent solution is added to 5 ml of 5 mg / L cobalt standard solution, an orange-red complex NHS-Co is formed.) 2+ (Generated), such as Figure 3 As shown, an absorption peak is generated at 410~430 nm.

[0091] (2) Determination of buffer solutions: Prepare buffer solutions with different pH values. Take 2 ml of each buffer solution and add 5 ml of 2 mg / L cobalt standard solution and 1 ml of 2 g / L colorimetric reagent solution to each. Dilute to 10 ml with deionized water, let stand at room temperature for 15 min, and then measure using a UV spectrophotometer. Figure 4As shown, in a buffer solution system with pH=3, NHS-Co 2+ The complex exhibited the highest absorbance, and a buffer solution with pH=3 was ultimately selected. The buffer solutions were acetate-ammonium acetate-TKPP-KHP buffer solutions (pH=2, 3, 4, 5, 6), with an NHS concentration of 2 g / L and a cobalt standard solution concentration of 2 mg / L.

[0092] (3) Determination of surfactants: Four different types of microemulsions (surfactants) were prepared: Tween-80, CTMAB, OP-100, and CTMAB-OP. 1 ml of each type of surfactant and 1 ml of deionized water were added to each microemulsion. 5 ml of 2 mg / L cobalt standard solution, 2 ml of pH 3 acetate-ammonium acetate-TKPP-KHP buffer solution, and 1 ml of 2 g / L colorimetric reagent solution were added to each solution. The solution was then diluted to 10 ml with deionized water. After standing at room temperature for 15 min, the solution was measured using a UV spectrophotometer. The surfactant-free NHS-Co... 2+ The complex solution served as a control, such as... Figure 5 As shown, NHS-Co contains surfactants CTMAB, OP-100, and CTMAB-OP. 2+ The absorbance of the complex was similar to that of the control NHS-Co. 2+ The absorbance of the complex was slightly higher than that of the control, while the absorbance of 4% Tween-80 was twice that of the control. Therefore, 4% Tween-80 was finally selected as the surfactant.

[0093] (4) Take 0.2 mL, 0.4 mL, 0.6 mL, 0.8 mL, and 1.0 mL of 4% Tween-80 respectively, and add 5 mL of 2 mg / L cobalt standard solution, 2 mL of pH 3 acetate-ammonium acetate-TKPP-KHP buffer solution, and 1 mL of 2 g / L colorimetric reagent solution to each. Dilute to 10 mL with deionized water, let stand at room temperature for 15 min, and then measure using a UV spectrophotometer. The results show that: Figure 6 As shown, the absorbance is highest and most stable when the dosage of 4% Tween-80 is 0.6 mL. Therefore, the optimal dosage of 4% Tween-80 is 0.6 mL.

[0094] Example 3

[0095] The colorimetric reagents NHS and Co prepared in Example 1 2+ The stoichiometric ratio was established using Job's plot experimental analysis, in which Co in solution... 2+ With a constant molar number (1 mol), the mole fraction of NHS was varied, and the absorbance values ​​were plotted based on these changes. As the molar ratio of NHS increases, the absorbance gradually increases, as shown below. Figure 7 As shown, when NHS and Co 2+ When the molar ratio of Co to Co is 2:1, the absorbance changes significantly, indicating that Co 2+ The bonding stoichiometry with NHS is 1:2. Based on the above facts, it is hypothesized that azo dyes affect Co. 2+ Possible sensing mechanisms, such as Figure 8 As shown.

[0096] The binding constant measures the effectiveness of the complexation between the chromogenic agent and the metal ion. The binding constant Ka of the complexation reaction data was calculated using the Benesi-Hildebrand equation, such as... Figure 9 As shown. In aqueous solution, the absorbance values ​​at 410–430 nm are related to Co. 2+ The relationship is linear, and the newly formed complex (NHS-Co) 2+ The binding constant in water was determined to be 6.24 × 10⁻⁶. 7 M -1 Linear correlation coefficient R 2 =0.9989. The numerical value of the combined constant clearly shows the relationship between the colorant and Co. 2+ They form stable complexes.

[0097] Example 4

[0098] Prepare NHS colorimetric reagent solution (concentration of 2 g / L), acetic acid-ammonium acetate-TKPP-KHP buffer solution (pH=3), 4% Tween-80 solution, and prepare cobalt ion solutions of different concentrations for later use. Each substance is added in the optimal amount in Example 2.

[0099] The absorbance of mixed solutions of cobalt ions and NHS colorimetric reagent at different concentrations was determined using spectrophotometry, with an NHS solution of equal concentration used as a blank control. A standard curve was plotted by plotting the absorbance differences between the systems containing different cobalt ion concentrations and the blank control system as the ordinate and the cobalt ion concentration as the abscissa. Figure 10 , Figure 11 As shown, a standard curve was plotted with the absorbance of solutions containing different cobalt ion concentrations as the ordinate and the cobalt ion concentration as the abscissa; Figure 10 As shown, the standard curve equation for cobalt ion concentrations in the range of 0.01–0.1 mg / L is y = 0.38x + 0.08885 (R0). 2 =0.98796); such as Figure 11 As shown, the standard curve equation for cobalt ion concentrations in the range of 0.1–1.0 mg / L is y = 0.64x - 0.00038(R). 2 =0.99935), apparent molar absorptivity ε=3.510×10 4L / (mol·cm), the detection limit for cobalt ions is 5×10 L / (mol·cm). -3 mg / L, detection limit is 1×10 -2 mg / L.

[0100] Example 5

[0101] Seventeen test solutions were prepared, 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 + Cu 2+ The concentrations of all metal ions were 5 mg / L. 1 ml of the 2 g / L colorimetric reagent solution prepared in Example 1, 2 ml of a pH 3 acetate-ammonium acetate-TKPP-KHP buffer solution, and 0.6 ml of 4% Tween-80 solution were added. The solution was then diluted to 10 ml with deionized water. A colorimetric reagent solution of equal concentration without any metal ions was used as a blank solution. After standing at room temperature for 15 min, the solutions were measured using a UV spectrophotometer. The results showed that... Figure 12 As shown, the azo colorimetric reagent exhibited activity against Co in all seventeen metal ion recognition tests. 2+ Specific detection, such as Figure 13 As shown, when different metal ions of the same concentration are added, NHS-Co at 426 nm... 2+ The absorbance value increased significantly, while the binding effect of other ions with the colorimetric reagent was significantly smaller, only Co... 2+ The ability to specifically bind to the colorimetric reagent may be due to the colorimetric reagent containing substances that bind to Co. 2+ The highly affinity coordination sites enable the chromogenic agent to exhibit a high affinity for Co. 2+ High selectivity.

[0102] Example 6

[0103] Comparative Study of PAN Method and NHS Method for Cobalt Detection in Water

[0104] The PAN spectrophotometric method for aluminum detection in water: Take five 20.0 mL stoppered colorimetric tubes and add 5 mL of cobalt standard solutions of 0.200 mg / L, 0.400 mg / L, 0.600 mg / L, 0.800 mg / L, and 1.00 mg / L, respectively. Add 0.6 mL of 4% Tween-80 solution, 2 mL of pH 5 acetate-ammonium acetate-TKPP-KHP buffer solution, and 1 mL of 2 g / L PAN colorimetric reagent (CAS No.: 85-85-8) solution to each solution. Measure the absorbance of each standard solution at 580 nm using a spectrophotometer. Plot a standard curve based on the cobalt concentration of each cobalt standard solution and the corresponding absorbance of the standard solution. Figure 14 As shown, the equation of the standard curve is y = 0.62x + 0.005(R). 2 =0.99258), apparent molar absorptivity ε=3.284×10 4 L / (mol·cm).

[0105] A comparative study of the PAN method and the NHS method for detecting cobalt ions in water found that the limit of detection (LOD) for cobalt ions in water by the PAN method was 0.08 mg / L, while that by the NHS method was 0.005 mg / L. Furthermore, the NHS method showed better fitting and sensitivity than the PAN method. Overall, the NHS method performed better.

Claims

1. A Co 2+ Colorimetric reagent in the detection of Co 2+ Applications; detection of Co 2+ The process includes the following steps: (1) Take the sample to be tested and add buffer solution to adjust the pH value of the sample to be tested; (2) Add colorimetric reagent and surfactant to the sample to be tested, mix and let stand; (3) After the reaction is complete, the absorbance is measured by spectrophotometry. The measured absorbance value is then mapped to the standard curve to obtain the Co of the sample to be tested. 2+ concentration; The buffer solution is an acetic acid-ammonium acetate-TKPP-KHP buffer solution with pH=3; The surfactant is 4% Tween-80, and the amount used is 0.6 mL; The concentration of the colorimetric reagent is 2 g / L, and the structure of the colorimetric reagent is shown below: 。 2. The Co according to claim 1 2+ Colorimetric reagent in the detection of Co 2+ The application, characterized in that, The Co 2+ Colorimetric reagent in the detection environment Co 2+ Applications.

3. The Co according to claim 1 2+ Colorimetric reagent in the detection of Co 2+ The application, characterized in that, The settling time in step (2) is 10~20 minutes.

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