Extraction principle-based ultra-trace analysis method for copper element in rare earth material

Abstract

The invention belongs to the technical field of rare earth material analysis, and particularly relates to an ultra-trace analysis method for a copper element in a rare earth material based on an extraction principle, and the analysis method comprises the following steps: dissolving a rare earth oxide sample with 1: 1 hydrochloric acid, and drying by distillation to obtain a sample solution; sequentially adding an ammonium citrate solution, a hydroxylamine hydrochloride solution and a copper reagent solution into the sample solution, stirring for 1-2 minutes at the rotating speed of 150-200rpm, dropwise adding ammonia water with the ratio of 1: 5 to adjust the pH value to be 9-10, and forming a complex by Cu < 2 + > and a copper reagent to obtain a complex solution; adding an extracting agent into the complex solution, oscillating and extracting for 1-2 minutes, standing and layering for 10-15 minutes, and taking a lower layer organic phase; when ultra-trace analysis is carried out on the copper in the rare earth element, through specific chemical treatment, other elements or compounds which may interfere with determination are reduced, and through collaborative optimization of chemical extraction and spectrophotometry, the lower detection limit of the copper in the rare earth element is reduced to 0.1 ppm from traditional 2ppm.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth material analysis, and particularly relates to an ultra-trace analysis method of copper elements in rare earth materials based on the extraction principle. Background Art

[0002] In the process of high-end application of rare earth materials, the importance of element purity control and impurity detection technology has become increasingly prominent. As a key strategic resource in the modern industrial system, the precise analysis of trace impurity elements in rare earth materials directly affects their performance in cutting-edge fields such as semiconductors, new energy, and aerospace. Among them, copper, as a typical non-rare earth impurity, can significantly change the electrical, optical, and mechanical properties of the material even at trace levels. Although existing detection technologies can achieve conventional elemental analysis, the detection of ultra-trace levels of copper still faces methodological bottlenecks. There is an urgent need to develop new analytical methods with both high selectivity and high sensitivity.

[0003] Currently, the detection of copper in rare earth materials primarily relies on instrumental analytical techniques such as inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectroscopy (AAS). However, these methods generally suffer from three technical limitations when dealing with ultratrace detection: First, the chemical similarity between the rare earth matrix and copper leads to severe matrix effects, significantly reducing detection accuracy; second, the detection limits of existing instruments are typically at the nanogram level, making it difficult to meet the requirements of some high-end applications for picogram or even femtogram-level detection; and third, complex sample pretreatment processes easily introduce contamination risks and are costly to operate. Furthermore, traditional methods lack the ability to specifically enrich trace copper, making it impossible to effectively reduce the error caused by coexisting interfering ions, further limiting the reliability of detection results.

[0004] Based on the above problems, the present application proposes an ultra-trace analysis method for copper elements in rare earth materials based on the extraction principle to improve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide an ultra-trace analysis method for copper in rare earth materials based on the extraction principle. When performing ultra-trace analysis on copper in rare earth elements, the present invention reduces other elements or compounds that may interfere with the determination through specific chemical treatment. Through the coordinated optimization of chemical extraction and spectrophotometry, the detection limit of copper in rare earth elements is reduced from the traditional 2ppm to 0.1ppm, thereby improving the sensitivity and accuracy of the analysis and having the advantages of low cost and high efficiency.

[0006] The technical solutions adopted by the present invention are as follows: An ultra-trace analysis method for copper in rare earth materials based on the extraction principle comprises the following steps: St1: Sample pretreatment: dissolve the rare earth oxide sample in 1:1 hydrochloric acid and evaporate to dryness to obtain a sample solution, which is then cooled at room temperature. St2: Complex formation, add ammonium citrate solution, hydroxylamine hydrochloride solution and copper reagent solution to the sample solution in sequence, stir at 150-200 rpm for 1-2 minutes, add 1:5 ammonia water dropwise to adjust the pH value to pH 9-10, and remove high-valent copper (such as Cu 3+ ) is reduced to Cu 2+ , Cu 2+ forming a complex with a copper reagent to obtain a complex solution; St3: Extraction and separation: add the extractant to the complex solution, shake and extract for 1 to 2 minutes, let it stand for 10 to 15 minutes and then remove the lower organic phase; St4: Spectrophotometric detection: transfer the organic phase to a cuvette, measure the absorbance of the organic phase at a wavelength of 430 nm, and calculate the copper content using the linear regression equation of the standard curve.

[0007] In a preferred embodiment, in St2, the concentration of the ammonium citrate solution is 50%, the concentration of the hydroxylamine hydrochloride solution is 40%, and the concentration of the copper reagent solution is 2%.

[0008] In a preferred embodiment, in St3, the extractant is any one of the following substances: ethyl acetate, toluene, chloroform, and carbon tetrachloride.

[0009] In a preferred embodiment, in St3, the volume ratio of the complex solution to the extractant is 1:1.5.

[0010] In a preferred embodiment, in St4, the standard curve is established based on a 0-2 μg / ml copper standard solution and includes six concentration points: 0, 0.1, 0.2, 0.5, 1.0, and 2.0 μg / ml.

[0011] In a preferred embodiment, the linear regression equation of the standard curve is y=29.794x-1.2387, and the correlation coefficient R 2 ≥0.999, where y represents the copper content and x represents the absorbance.

[0012] The technical effects achieved by the present invention are: When conducting ultra-trace analysis of copper in rare earth elements, the present invention successfully extracts and enriches the copper element in the rare earth sample through a series of specific chemical pretreatment steps, while significantly reducing other elements or compounds that may interfere with the determination. The pretreated sample is detected using a spectrophotometer. By carefully selecting the wavelength and optimizing the conditions for complex formation, the present invention overcomes the limitations of traditional spectrophotometers in analyzing ultra-trace copper. Through the coordinated optimization of chemical extraction and spectrophotometry, the detection limit of copper in rare earth elements is reduced from the traditional 2ppm to 0.1ppm, greatly improving the sensitivity and accuracy of the analysis. The present invention effectively solves the problems of insufficient sensitivity and interference in the prior art, is particularly suitable for ultra-trace quality control of copper in rare earth materials, and has the advantages of low cost and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a standard curve diagram of the rare earth copper content in Test Example 1 of the present invention. DETAILED DESCRIPTION

[0014] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0015] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0016] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in a preferred embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it constitute a separate or selective embodiment that is mutually exclusive of other embodiments.

[0017] Example Example 1 Weigh 1g of rare earth oxide, add it to 20ml of 1:1 hydrochloric acid, heat to dissolve, and evaporate to near dryness to obtain a sample solution. Cool the sample solution at room temperature, add 5ml of 50% (w / v) ammonium citrate solution, 3ml of 40% (w / v) hydroxylamine hydrochloride solution, and 2ml of 2% (w / v) copper reagent solution to the sample solution in sequence, stir at 180rpm for 1 minute, add 1:5 ammonia water dropwise to adjust the pH value to pH 9.5, and continue stirring for 30 seconds (avoid local over-alkalinity or over-acidity to ensure the stability of the system pH value). Cu 2+A complex is formed with the copper reagent to obtain a complex solution, 15 ml of chloroform is added, and the solution is extracted by shaking for 1 minute. After standing for 15 minutes, the organic phase is separated and transferred to a cuvette. The absorbance of the organic phase is measured at a wavelength of 430 nm. The absorbance is measured to be 0.068. The copper content is calculated to be 0.8 ppm by substituting it into the linear regression equation of the standard curve.

[0018] It should be noted that the linear regression equation of the standard curve is obtained through Test Example 1. For the specific method of obtaining it, please refer to Test Example 1.

[0019] Here, when ultra-trace analysis of copper in rare earth elements is performed, copper ions are enriched by chemical pretreatment, and then iron, manganese, cobalt, nickel, zinc, bismuth and other ions are masked by a masking agent (ammonium citrate) to prevent the above ions from reacting with DDTC. - Competitive coordination, at the same time, the high-valent copper (such as Cu 3+ ) is reduced to Cu 2+ , to ensure that all copper participates in the reaction in an effective form, and finally the copper reagent (sodium diethyldithiocarbamate) and Cu 2+ Under alkaline conditions, a stable Cu(DDTC)2 hydrophobic complex is formed. During the complexation process, the pH value is controlled to be stable at 9-10, which can effectively promote the - Dissociation of NaDDTC→Na + +DDTC - ), increase the ligand concentration to avoid DDTC caused by too low pH - Protonation (NaDDTC+H + →HDDTC), reducing the complexation efficiency, and also avoiding Cu(OH)2 precipitation caused by excessively high pH. Finally, ultratrace analysis is achieved by taking advantage of the linear relationship between absorbance and Cu(DDTC)2 concentration (which conforms to Beer's law).

[0020] It should be noted that trace amounts of copper ions mean their concentration in the system is very low. From a reaction kinetics perspective, although low reactant concentrations reduce the probability of effective interparticle collisions per unit time and may slow the reaction rate, as long as the Gibbs free energy change ΔG is less than 0, the reaction can proceed spontaneously and gradually complete over time. Moreover, in a trace copper ion system, there are relatively few interfering factors such as impurity ions, which, to a certain extent, facilitates the smooth progress of the redox reaction between hydroxylamine hydrochloride and copper ions, reducing competition and interference from other side reactions on the target reaction.

[0021] Furthermore, the factors that affect the reaction are as follows: Solution acidity: The acidity of the solution significantly affects the reduction reaction of copper ions by hydroxylamine hydrochloride. A suitable acidic environment can maintain the stability and reducing activity of hydroxylamine hydrochloride, promoting the existence of copper ions in an ionic state and facilitating the reduction reaction. Generally, it is more appropriate to control the solution pH value between 2 and 4. Within this acidity range, hydroxylamine hydrochloride can better exert its reducing effect while also inhibiting side reactions such as the hydrolysis of copper ions. Reaction temperature: Temperature affects the reaction rate. Properly increasing the temperature can increase the kinetic energy of the reactant molecules, increase the effective collision frequency, and accelerate the reduction rate of trace copper ions by hydroxylamine hydrochloride. However, too high a temperature may cause hydroxylamine hydrochloride to decompose and reduce its effective concentration. The reaction temperature needs to be controlled at 30-60°C; Reaction time: Due to the low concentration of trace copper ions, the reaction rate is relatively slow. Sufficient reaction time is required to allow hydroxylamine hydrochloride to fully contact and react with copper ions so that the copper ions can be reduced to cuprous ions as much as possible.

[0022] In actual operation, to successfully achieve the reduction of trace copper ions by hydroxylamine hydrochloride, it is necessary to accurately control the above-mentioned influencing factors and ensure that the reaction is carried out under suitable conditions so that trace copper ions can be reduced to cuprous ions. In this application, trace copper is measured, and regarding the reaction time, by immediately adjusting the pH to the alkaline range after adding the reagent, the reaction time is insufficient for the formation of cuprous ions, thereby ensuring the accuracy of the copper content determination.

[0023] Example 2 Weigh 1g of rare earth oxide, add it to 20ml of 1:1 hydrochloric acid, heat to dissolve, and evaporate to dryness to obtain a sample solution. Cool the sample solution at room temperature, add 10ml of 50% (w / v) ammonium citrate solution, 5ml of 40% (w / v) hydroxylamine hydrochloride solution, and 3ml of 2% (w / v) copper reagent solution to the sample solution in sequence, stir at 150rpm for 2 minutes, add 1:5 ammonia water dropwise to adjust the pH value to pH 10, continue stirring for 30 seconds, and Cu 2+ A complex is formed with the copper reagent to obtain a complex solution, 15 ml of chloroform is added, and the solution is extracted by shaking for 1 minute. After standing for 15 minutes, the organic phase is separated and transferred to a cuvette. The absorbance of the organic phase is measured at a wavelength of 430 nm. The absorbance is measured to be 0.065. The copper content is calculated to be 0.7 ppm by substituting it into the linear regression equation of the standard curve.

[0024] Comparative Example Comparative Example 1 This comparative example 1 adopts the traditional spectrophotometric method, specifically: Weigh 1 g of rare earth oxide and add it to 20 ml of 1:1 hydrochloric acid. Heat to dissolve and evaporate to near dryness to obtain a sample solution. Cool the sample solution at room temperature and add 2 ml of 2% (w / v) copper reagent solution to the sample solution. Stir at 150 rpm for 2 minutes. Add 1:5 ammonia water dropwise to adjust the pH to pH 9.5 and make the volume to 50 ml. Measure the absorbance of the organic phase at a wavelength of 430 nm. The absorbance is measured to be 0.119 and the copper content is calculated to be 2.3 ppm.

[0025] It should be noted that the method of calculating the copper content by traditional spectrophotometry is an existing mature application. The specific calculation method is referred to the existing technology and will not be further elaborated here.

[0026] Comparative Example 2 The operation steps of this comparative example are the same as those of Example 1, except that the addition of hydroxylamine hydrochloride solution is omitted. Specifically: Weigh 1 g of rare earth oxide, add it to 20 ml of 1:1 hydrochloric acid, heat to dissolve, and evaporate to near dryness to obtain a sample solution. Cool the sample solution at room temperature, and add 5 ml of 50% (w / v) ammonium citrate solution and 2 ml of 2% (w / v) copper reagent solution to the sample solution in sequence. Stir at 180 rpm for 1 minute, add 1:5 ammonia water dropwise to adjust the pH to pH 9.5, continue stirring for 30 seconds, add 15 ml of chloroform, shake and extract for 1 minute, let stand for 15 minutes, separate the organic phase, transfer the organic phase to a cuvette, and measure the absorbance of the organic phase at a wavelength of 430 nm. The absorbance was measured to be 0.113, and the copper content was calculated to be 2.1 ppm.

[0027] Comparative Example 3 The operation steps of this comparative example are the same as those of Example 1, except that the addition of ammonium citrate solution is omitted. Specifically: Weigh 1g of rare earth oxide and add it to 20ml of 1:1 hydrochloric acid. Heat to dissolve and evaporate to dryness to obtain a sample solution. Cool the sample solution at room temperature. Add 3ml of 40% (w / v) hydroxylamine hydrochloride solution and 2ml of 2% (w / v) copper reagent solution to the sample solution in sequence. Stir at 180rpm for 1 minute. Add 1:5 ammonia water dropwise to adjust the pH to pH 9.5. Continue stirring for 30 seconds. 2+ A complex was formed with the copper reagent to obtain a complex solution, 15 ml of chloroform was added, and the solution was extracted by shaking for 1 minute. After standing for 15 minutes, the organic phase was separated and transferred to a cuvette. The absorbance of the organic phase was measured at a wavelength of 430 nm. The absorbance was measured to be 0.168, and the copper content was calculated to be 3.8 ppm.

[0028] Test Case Test Example 1: Standard Curve Verification Six copper standard solutions with contents of 0, 0.1, 0.2, 0.5, 1.0, and 2.0 μg were prepared in sequence and processed according to the steps in Example 1. The absorbances of the six copper standard solutions were obtained respectively. The results are shown in Table 1.

[0029] Table 1:

[0030] According to the data in Table 1, curve fitting is performed (such as Figure 1 As shown), the linear regression equation of the standard curve was obtained: y = 29.794x - 1.2387 (R 2 =0.9992), where y represents the copper content and x represents the absorbance.

[0031] In a specific embodiment, a scatter plot is drawn in a document processing software (e.g., Excel, WPS) according to the test data in Table 1, and a trend line (linear) is added to the scatter plot to obtain the linear regression equation of the standard curve. Of course, the linear regression equation of the standard curve can also be obtained by manual calculation or by substituting the data in Table 1 into the linear regression equation based on the principle of linear regression. In this embodiment, the linear regression equation of the standard curve is obtained by drawing a scatter plot in the document processing software and adding a trend line. Of course, the method of obtaining the linear regression equation of the standard curve in this embodiment is only an example and does not constitute a specific limitation.

[0032] Test Example 2: Influence of Interfering Ions Add 1000 times Fe to a solution containing 0.30 ppm copper 3+ 、Mn 2+ The copper content was determined to be 0.31 ppm (deviation + 3.3%).

[0033] By analyzing the data in Examples 1 and 2, we can observe that, in the ultra-trace analysis of copper in rare earth elements, these two Examples successfully raised the detection limit to 0.1 ppm by combining chemical extraction conditions with the full utilization of the advantages of the spectrophotometer, which is 10 times higher than the traditional spectrophotometric method (detection limit 2 ppm). In addition, the precision (RSD) of Examples 1 and 2 is significantly better than that of the comparative example. At the same time, combining the data of Examples 1, 2, and 3, we can see that the ammonium citrate masking makes Fe 3+ The interference is reduced by more than 90%, significantly improving the accuracy and range of analysis.

[0034] In the present application, it can be seen from Comparative Examples 1 to 3 that in the traditional determination method, the detection limit cannot exceed the lower limit of 2ppm. In the present application, the copper content is calculated by substituting the linear regression equation of the standard curve into the test steps in Test Example 1, and the copper content in Example 1 and Example 2 is calculated by substituting the linear regression equation of the standard curve. The detection limit can be effectively reduced to 0.1ppm, which greatly improves the sensitivity and accuracy of the analysis. At the same time, it can be seen from Test Example 2 that when performing ultra-trace analysis of copper in rare earth elements, the problems of insufficient sensitivity and interference in the prior art are effectively solved.

[0035] In summary, the present invention significantly improves detection sensitivity through the synergistic optimization of chemical extraction and spectrophotometry while ensuring low cost, filling the technical gap between traditional spectrophotometry and mass spectrometry, and effectively solving the problems of insufficient sensitivity and severe interference in the existing technology. It is suitable for ultra-trace quality control of copper elements in rare earth materials, demonstrates significant technological progress and innovative value, and can provide strong support for scientific research and technological applications in related fields.

[0036] The foregoing is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained herein shall, unless otherwise specified or limited, be implemented in accordance with conventional means in the art.

Claims

1. An ultra-trace analysis method for copper in rare earth materials based on the extraction principle, characterized by: The following steps are involved: St1: Dissolve the rare earth oxide sample in 1:1 hydrochloric acid and evaporate to dryness to obtain a sample solution; St2: Add ammonium citrate solution, hydroxylamine hydrochloride solution and copper reagent solution to the sample solution in sequence, stir at 150-200 rpm for 1-2 minutes, add 1:5 ammonia water dropwise to adjust the pH value to pH 9-10, Cu 2+ forming a complex with a copper reagent to obtain a complex solution; St3: Add the extractant to the complex solution, shake and extract for 1-2 minutes, let it stand for 10-15 minutes and then remove the lower organic phase; St4: Transfer the organic phase to a cuvette, measure the absorbance of the organic phase at a wavelength of 430 nm, and calculate the copper content using the linear regression equation of the standard curve.

2. The method for ultra-trace analysis of copper in rare earth materials based on the extraction principle according to claim 1, characterized in that: In St2, the concentration of the ammonium citrate solution is 50%, the concentration of the hydroxylamine hydrochloride solution is 40%, and the concentration of the copper reagent solution is 2%.

3. The method for ultra-trace analysis of copper in rare earth materials based on the extraction principle according to claim 1, characterized in that: In St3, the extractant is any one of the following substances: ethyl acetate, toluene, chloroform, and carbon tetrachloride.

4. The method for ultra-trace analysis of copper in rare earth materials based on the extraction principle according to claim 1, wherein: In St3, the volume ratio of the complex solution to the extractant is 1:1.

5.

5. The method for ultra-trace analysis of copper in rare earth materials based on the extraction principle according to claim 1, characterized in that: In St4, the standard curve is established based on a 0-2 μg / ml copper standard solution and includes six concentration points: 0, 0.1, 0.2, 0.5, 1.0, and 2.0 μg / ml.

6. The method for ultra-trace analysis of copper in rare earth materials based on the extraction principle according to claim 1, characterized in that: The linear regression equation of the standard curve is y=29.794x-1.2387, and the correlation coefficient R 2 ≥0.999, where y represents the copper content and x represents the absorbance.

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