Method for detecting lead, mercury and cadmium elements in steel sample

Abstract

A method for detecting lead, mercury and cadmium elements in a steel sample belongs to the technical field of steel raw and auxiliary material detection, and comprises the following steps: S1, taking a sample, and then weighing high-purity iron for a blank test; s2, preparing a measuring solution, namely putting the weighed sample into a beaker, adding water and nitric acid, covering a meter, heating until bubbling is stopped, adding hydrochloric acid, continuously heating until complete decomposition, cooling to room temperature, quantitatively transferring the solution into a 100mL volumetric flask, diluting with water to a scale, and uniformly mixing; s3, preparing a standard curve solution; s4, measuring the calibration solution; and S5, measuring the sample solution. According to the method, the contents of lead, mercury and cadmium are detected by drawing the standard curve, making the standard solution and utilizing the inductively coupled plasma atomic emission spectrometry, so that toxic and harmful elements with very little content can be detected, and a test detection standard can be compiled to be popularized and used as a standard for executing detection in the industry.

Description

Technical Field

[0001] This invention relates to a method for detecting lead, mercury, and cadmium elements in steel samples, belonging to the field of steel raw material testing technology. Background Technology

[0002] Lead is a heavy metal and a highly toxic pollutant. It can damage the blood, break down red blood cells, and diffuse through the bloodstream to all organs and tissues, entering the bones and causing radial nerve paralysis and finger tremors. In severe cases, it can lead to lead encephalopathy and death. Mercury is a highly toxic substance. Ingestion through contact or inhalation can damage the central nervous system, causing neurological disorders, restlessness, and extreme pain. Cadmium poisoning can cause muscle atrophy, joint deformities, excruciating bone pain, insomnia, pathological fractures, and even death. Cadmium is primarily found in cadmium-containing wastewater discharged from factories into riverbeds and used to irrigate rice paddies. It is absorbed by plants and accumulates in rice. Long-term consumption of cadmium-contaminated rice or drinking cadmium-contaminated water can easily lead to osteomyelitis. Therefore, ensuring that products manufactured meet standards for lead, mercury, and cadmium levels is fundamental to protecting public health.

[0003] With the development of the times and the advancement of technology, steel products are becoming increasingly refined. Theoretically, the content of toxic and harmful elements is gradually decreasing and even disappearing. At the same time, people pay far more attention to toxic and harmful elements in food than to steel products. Therefore, there is still no standardized standard or method for testing lead, mercury, and cadmium in steel.

[0004] Therefore, we propose a method for detecting lead, mercury, and cadmium in steel samples. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for detecting lead, mercury and cadmium in steel samples, aiming to standardize and solve the problem of detecting toxic and harmful elements in steel samples.

[0006] The technical solution to the above technical problem is: A method for detecting lead, mercury, and cadmium in a steel sample includes the following steps: S1. Take a sample, and then weigh high-purity iron to perform a blank test; S2. Preparation of the measurement solution: Place the weighed sample in a beaker, add water and nitric acid, cover with a watch glass, heat until bubbling stops, add hydrochloric acid, continue heating until completely decomposed, cool to room temperature, quantitatively transfer the solution to a 100mL volumetric flask, dilute with water to the mark, and mix well. S3. Preparation of standard curve solution; S4. Measurement of calibration solution; S5. Measurement of the sample solution.

[0007] Preferably, in S1, 6 parts of high-purity iron are weighed, each part accurate to 0.0001g, the purity of the high-purity iron is greater than 99.99%, and the mass of each part of high-purity iron is the same as the mass of the sample.

[0008] Preferably, the concentration of nitric acid in S2 is 1.42 g / mL; and the concentration of hydrochloric acid is 1.19 g / mL. The volume ratio of water to nitric acid to hydrochloric acid is 2:1:1. The ratio of sample to water is 1 mL of nitric acid per 0.1000 g. The heating and further heating temperatures in S2 are both 245-255℃.

[0009] Preferably, if there are insoluble carbides in the sample after it has been dissolved in the beaker and cooled to room temperature in air, add perchloric acid, heat at 295-305°C until perchloric acid fumes are emitted for 3-5 minutes, remove, cool to room temperature, add water and nitric acid, shake well, then add hydrochloric acid, and heat at 295-305°C to dissolve the salts.

[0010] Preferably, the perchloric acid concentration (ρ) is 1.67 g / mL, the nitric acid concentration (ρ) is 1.42 g / mL, and the hydrochloric acid concentration (ρ) is 1.19 g / mL. The volume ratio of perchloric acid, water, nitric acid, and hydrochloric acid added when heating to dissolve salts is 1:2:1:1.

[0011] Preferably, the preparation method of the standard curve solution in S3 is as follows: place the high-purity iron weighed in S1 into beakers, dissolve it according to step S2, cool it to room temperature, transfer the solution to a 100mL volumetric flask, add the standard solution of the element to be measured according to Table 1, dilute with water to the mark, and mix well.

[0012] Preferably, the volumes of lead, mercury, and cadmium added to the standard solution are the same: 1.00 mL, 2.50 mL, 5.00 mL, and 10.00 mL, respectively, corresponding to element contents in the equivalent sample of 0.0020%, 0.0050%, 0.010%, and 0.020%, respectively; the content of lead, mercury, and cadmium in the standard solution is 0.01 mg / mL.

[0013] Table 1

[0014] Preferably, the specific method for measuring the calibration solution in S4 is as follows: first use the blank solution of the calibration curve, and then aspirate the calibration curve solution in order of increasing concentration, and aspirate deionized water between each aspiration of the solution; repeat the measurement at least twice, and take the average of the two readings; plot the linear correlation coefficient of the calibration curve which is greater than 0.999.

[0015] Preferably, the specific steps for measuring the sample solution in S5 are as follows: after aspirating the calibration solution, immediately proceed with the sample solution operation, followed by the certification standard sample solution, then aspirate the sample solution and certification standard sample solution again, aspirate deionized water between each measurement, and the sample solution and certification standard sample solution should be measured at least twice.

[0016] Preferably, the room temperature is 5-40℃. The temperature of the sample dissolution chamber is 5-40℃. The room temperature does not affect the dissolution effect, but the temperature of the ICP instrument analysis chamber is required to be 15-25℃.

[0017] A method for detecting lead, mercury, and cadmium in steel samples, the principle of which is: The sample to be tested is dissolved in nitric acid and hydrochloric acid and diluted to a certain volume. The nebulized solution is introduced into an inductively coupled plasma atomic emission spectrometer. At the recommended wavelength, the emission spectral intensity of each analyte in the solution or its relative intensity to the internal standard element is measured. The mass fraction of each analyte is calculated based on the calibration curve prepared from the standard solution.

[0018] The beneficial effects of this invention are: This invention utilizes inductively coupled plasma atomic emission spectrometry (ICP-AES) to detect the content of lead, mercury, and cadmium by plotting standard curves and preparing standard solutions, enabling the detection of trace amounts of these toxic and harmful elements. Furthermore, it allows for the development of testing standards for widespread application within the industry. Detailed Implementation

[0019] The reagents, experimental instruments, and experimental equipment used in this invention include: 1. Nitric acid (ρ approx. 1.42 g / mL), 2. Hydrochloric acid (ρ approx. 1.19 g / mL), 3. Perchloric acid (ρ approx. 1.67 g / mL), 4. Lead standard solution (0.01 mg / mL), 5. Mercury standard solution (0.01 mg / mL), 6. Cadmium standard solution (0.01 mg / mL), 7. High-purity iron (purity greater than 99.99%), several 200 mL beakers, several 100 mL volumetric flasks, heating instruments, electronic analytical balance (model ME4002E, Mettler AG, Switzerland), inductively coupled plasma atomic emission spectrometer (model Optima 8300, PE Corporation, USA).

[0020] Implementation process of the present invention: A method for detecting lead, mercury, and cadmium in steel samples: S1. Prepare the sample according to the appropriate national standard. Weigh 0.5000g of the sample, accurate to 0.0001g.

[0021] Blank test. Weigh 0.5000g of high-purity iron (high-purity iron, purity greater than 99.99%) and perform 6 reagent blank tests along with the sample. (Because the sample is not separated after dissolution, a blank must be added for each point of the curve.) One of them is used as the calibration curve blank solution. (The other 4 are performed at 4 points).

[0022] S2. Preparation of the measurement solution. Place the weighed sample in a 200mL beaker, add 10mL of water and 5mL of nitric acid (nitric acid, ρ approx. 1.42g / mL), cover with a watch glass, and slowly heat to 250℃ until bubbling stops. Add 5mL of hydrochloric acid (hydrochloric acid, ρ approx. 1.19g / mL), and continue heating at 250℃ until complete decomposition. If insoluble carbides are present, add 5mL of perchloric acid (perchloric acid, ρ approx. 1.67g / mL), heat to 300℃ until perchloric acid fumes are emitted for 4 minutes, remove from heat, cool to 25℃, add 10mL of water and 5mL of nitric acid (nitric acid, ρ approx. 1.42g / mL), shake well, then add 5mL of hydrochloric acid (hydrochloric acid, ρ approx. 1.19g / mL), and heat to 300℃ to dissolve the salts. Cool to 25℃, quantitatively transfer the solution to a 100mL volumetric flask, dilute to the mark with water, and mix well.

[0023] S3. Preparation of standard curve solution. Weigh 0.5000g of high-purity iron (high-purity iron, purity greater than 99.99%) into 6 portions and place them into 200mL beakers respectively. Dissolve them according to step S2 (preparation of measurement solution). Cool to room temperature, transfer the solution to a 100mL volumetric flask, add the standard solution of the element to be measured according to Table 1, dilute with water to the mark, and mix well.

[0024] S4. Measurement of calibration solutions. First, use the blank solution for the calibration curve, and then aspirate the calibration curve solutions in order of increasing concentration, aspirating deionized water between each aspiration. Repeat the measurement at least twice and take the average of the two readings. Note: The linear correlation coefficient for plotting the calibration curve must be greater than 0.999.

[0025] S5. Measurement of the sample solution. Immediately after aspirating the calibration solution, proceed with the sample solution measurement, followed by the certification standard sample solution. Then aspirate both the sample solution and the certification standard sample solution again. Aspirate deionized water between each measurement. The sample solution and the certification standard sample solution should be measured at least twice.

[0026] Based on the recommended spectral lines for each element (see Table 2), two independent analyses should be performed. The difference between the results of the two independent analyses should not exceed the allowable difference shown in Table 3 below.

[0027] Table 2 Element Recommended Spectral Lines

[0028] Table 3. Allowable difference in analysis results

[0029] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for detecting lead, mercury and cadmium in a steel sample, characterized in that: The following steps are involved: S1. Take a sample, and then weigh high-purity iron for a blank test; S2. Preparation of measurement solution: Place the weighed sample in a beaker, add water and nitric acid, cover with a watch glass, heat until bubbling stops, add hydrochloric acid, continue heating until completely decomposed, cool to room temperature, quantitatively transfer the solution to a 100 mL volumetric flask, dilute to scale with water, and mix well; S3, preparation of standard curve solution; S4, measurement of calibration solution; S5. Measurement of sample solution.

2. The method for detecting lead, mercury and cadmium in a steel sample according to claim 1, characterized in that: In S1, 6 portions of high-purity iron are weighed, each portion is accurate to 0.0001g, the purity of the high-purity iron is greater than 99.99%, and the mass of each portion of high-purity iron is the same as the mass of the sample.

3. The method for detecting lead, mercury and cadmium in a steel sample according to claim 1, characterized in that: The ρ of nitric acid in S2 is 1.42 g / mL; the ρ of hydrochloric acid is 1.19 g / mL; The volume ratio of water: nitric acid: hydrochloric acid is 2:1:1; The ratio of sample to water is 1 mL of nitric acid for every 0.1000 g; The temperatures for heating and continued heating in S2 are both 245-255°C.

4. The method for detecting lead, mercury and cadmium in a steel sample according to claim 1, characterized in that: If there is insoluble carbide in the sample after it is dissolved in the beaker and before it cools to room temperature in the air, add perchloric acid and heat at 295-305℃ until perchloric acid smoke appears for 3-5 minutes, remove it, cool it to room temperature, add water and nitric acid, shake well, then add hydrochloric acid and heat at 295-305℃ to dissolve the salts.

5. The method for detecting lead, mercury and cadmium in a steel sample according to claim 4, characterized in that: Perchloric acid ρ is 1.67 g / mL, nitric acid ρ is 1.42 g / mL, and hydrochloric acid ρ is 1.19 g / mL; The volume ratio of perchloric acid: water: nitric acid: hydrochloric acid added to dissolve the salts is 1:2:1:

1.

6. The method for detecting lead, mercury and cadmium in a steel sample according to claim 1, characterized in that: The preparation method of the standard curve solution in S3 is as follows: place the high-purity iron weighed in S1 in a beaker, dissolve it according to step S2, cool it to room temperature, transfer the solution to a 100mL volumetric flask, add the standard solution of the element to be measured, dilute to the scale with water, and mix well.

7. A method for detecting lead, mercury and cadmium in a steel sample according to claim 6, characterized in that: The volumes of lead, mercury and cadmium elements added to the standard solution are the same, namely 1.00mL, 2.50mL, 5.00mL and 10.00mL, and the corresponding element contents in the equivalent samples are 0.0020%, 0.0050%, 0.010% and 0.020%, respectively; the content of lead, mercury and cadmium elements in the standard solution are all 0.01mg / mL.

8. The method for detecting lead, mercury and cadmium in a steel sample according to claim 1, characterized in that: The specific method for measuring the calibration solution in S4 is: first use the calibration curve blank solution, and aspirate the calibration curve solution in the order of increasing concentration, and aspirate deionized water between each aspiration of the solution; repeat the measurement at least twice, and take the average of the two readings; The linear correlation coefficient of the calibration curve was greater than 0.

999.

9. The method for detecting lead, mercury and cadmium in a steel sample according to claim 1, characterized in that: The specific steps for measuring the sample solution in S5 are: after aspirating the calibration solution, immediately perform the sample solution operation, then the certified standard sample solution, aspirate the sample solution and the certified standard sample solution again, aspirate deionized water between each measurement, and the sample solution and the certified standard sample solution should be measured at least twice.

10. The method for detecting lead, mercury and cadmium in a steel sample according to claim 1, characterized in that: The room temperature is 5-40°C.

Images