GB/T 34500.7-2026Chemical analysis methods for rare earth residues and waste water - Part 7: Determination of thorium and uranium contents - Inductively coupled plasma mass spectrometry (English PDF)

5.8 Extraction agent. Transfer

0.46 mL of sulfuric acid and nitric acid mixture (5.7) into 2 L of water, stir well, and the pH of the solution is 3.20 ± 0.05.

5.9 Thorium standard solution (rho=1000µg/mL), certified standard solution.

5.10 Uranium standard solution (rho=1000µg/mL), certified standard solution.

5.11 Rhodium Standard Stock Solution. Accurately weigh 0.3593 g of ammonium chlororhodium (w>=) that has been dried at 110 °C and cooled to room temperature in a desiccator. 99.99%), placed in a 100mL beaker, added 20mL hydrochloric acid (5.6), covered with a watch glass, dissolved at low temperature, cooled to room temperature, and transferred to a 100mL... Dilute to the mark with water in a volumetric flask and mix well. 1 mL of this solution contains 1 mg of rhodium.

5.12 Cesium Standard Stock Solution. Accurately weigh 0.1267 g of cesium chloride, dried at 110 °C and cooled to room temperature in a desiccator, and place it in a container... Add 10 mL of nitric acid (5.2) to a 100 mL beaker, cover with a watch glass, heat at a low temperature until completely dissolved, cool to room temperature, and transfer to a 100 mL container. Dilute to the mark with water in a volumetric flask and mix well. 1 mL of this solution contains 1 mg of cesium.

5.13 Rhenium Standard Stock Solution. Weigh 0.1000 g of metallic rhenium (w >= 99.99%), place it in a 100 mL beaker, and add 3 mL of hydrochloric acid. (5.6) 1 mL of nitric acid (5.2), cover with a watch glass, heat at low temperature until completely dissolved, cool to room temperature, transfer to a 100 mL volumetric flask, add 10 mL of nitric acid. Hydrochloric acid (5.6), diluted with water to the mark, and mixed well. 1 mL of this solution contains 1 mg of rhenium.

5.14 Bismuth Standard Stock Solution. Weigh 0.1000 g of metallic bismuth (w >= 99.99%), place it in a 250 mL beaker, and add 50 mL of nitric acid. (5.2) Cover with a watch glass, heat at low temperature until completely dissolved, boil to remove nitrogen oxides, and cool to room temperature. Transfer to a 100 mL volumetric flask with nitric acid (5.3). Dilute the solution in a volumetric flask to the mark with water and mix well. 1 mL of this solution contains 1 mg of bismuth.

5.15 Indium Standard Stock Solution. Accurately weigh 0.1000 g of metallic indium (w >= 99.99%), place it in a 100 mL beaker, and add 10 mL of salt. The acid (5.6) was heated at low temperature until completely dissolved, cooled to room temperature, transferred to a 100 mL volumetric flask, diluted to the mark with water, and mixed well. 1m contains 1mg of indium.

5.16 Mixed Standard Solution A. Transfer

1.00 mL each of the thorium standard solution (5.9) and the uranium standard solution (5.10) into a 100 mL volumetric flask. Add 5 mL of nitric acid (5.1) to the solution, dilute to the mark with water, and mix well. Transfer

10.00 mL of this solution to a 100 mL volumetric flask and add... Dilute 5 mL of nitric acid (5.1) to the mark with water and mix well. 1 mL of this solution contains 1 µg of thorium and uranium, respectively.

5.17 Mixed Standard Solution B. Transfer

10.00 mL of mixed standard solution A (5.16) into a 100 mL volumetric flask, add 5 mL of nitric acid. (5.1) Dilute with water to the mark and mix well. 1 mL of this solution contains 100 ng of thorium and uranium respectively.

5.18 Mixed internal standard solution. Transfer rhodium standard stock solution (5.11), cesium standard stock solution (5.12), and rhenium standard stock solution separately. (5.13)

1.00 mL each of bismuth standard stock solution (5.14) and indium standard stock solution (5.15) are placed in a 100 mL volumetric flask, and 5 mL of nitrate is added. Acid (5.1), diluted to the mark with water and mixed well. 1 mL of this solution contains 10 µg each of rhodium, cesium, rhenium, bismuth, and indium.

8.1 Samples Accurately transfer

5.00 mL of rare earth wastewater (7.1) or rare earth waste residue leachate (7.2) into a 150 mL beaker.

8.2 Parallel Tests Perform two parallel experiments.

8.3 Blank Test A blank test was performed along with the sample.

8.4 Preparation of a series of standard solutions Transfer the corresponding mixed standard solutions (5.16, 5.17) from Table 2 into eight 100 mL volumetric flasks, and add 1 mL of the mixed internal standard solution (5.18). Dilute to the mark with nitric acid (5.4), mix well, and proceed with the test. The mass concentrations of this standard series of solutions are shown in Table

2.If using a solution with online internal standard addition capability... The instrumentation of the device should be adjusted according to the addition ratio of the device to control the mass concentration of the mixed internal standard solution of the online determination solution to be 100 µg/L.

8.5 Preparation of analytical solutions Add

2.5 mL of nitric acid (5.4) to the beaker containing the sample (8.1), cover with a watch glass, and place on a temperature-controlled hot plate at a low temperature (180°C~). Heat to 220°C and digest until no obvious reaction is observed (no large amount of bubbles are produced). After cooling, transfer to a 50mL volumetric flask and add 0.5mL of the mixture. Mix the internal standard solution (5.18) with water to the mark, mix well, and prepare for testing. If the test result exceeds the working curve, refer to the test solution in Table 3. The content of the target element should be appropriately diluted and tested again; if an instrument with an online internal standard solution addition device is used, the addition method should be adjusted according to the device's requirements. The ratio was adjusted so that the mass concentration of the mixed internal standard solution for online determination was 100 µg/L.

8.6 Measurement

8.6.1 Drawing the working curve After the inductively coupled plasma mass spectrometer has stabilized, under the selected instrument operating conditions, the mass numbers of the analyte and internal standard elements are measured. At the same location, the ion current signal intensity of the analyte and internal standard element in a series of standard solutions (8.4) was measured sequentially. The ion current signal intensity of the analyte in the standard solution was then used as the ion current signal intensity. The mass concentration is plotted on the x-axis, and the ratio of the ion current signal intensity of the analyte to that of the internal standard is plotted on the y-axis to create a working curve. Working curves for each element are shown below. The correlation coefficient of the curve should be greater than 0.9995; otherwise, the operation should be repeated or a new series of standard solutions should be prepared for the operation.

8.6.2 Determination of analytical solutions and blank solutions After the working curve (8.6.1) meets the requirements for determination, the ion current signal intensity of the element to be determined in the blank solution and the analytical solution is measured. The instrument automatically processes data based on the working curve (8.6.1), calculates and outputs the content of each element.

9.Experimental Data Processing The content of the element to be tested is expressed as mass concentration (rhox), in milligrams per liter (mg/L), and is calculated according to formula (1).