Method for determining arsenic content in manganese iron by ICP-MS

Abstract

This invention discloses a method for determining the arsenic content in ferromanganese using ICP-MS, comprising: weighing a certain amount of sample, dissolving it in a steel volumetric flask with nitric acid, cooling and making up to volume, and then shaking well; nebulizing the solution and introducing it into an inductively coupled plasma mass spectrometer (ICP-MS) to determine the arsenic content; finally, plotting a working curve using arsenic standard solutions with concentration gradients, measuring the intensity ratio of the analyte to the internal standard reference line in the working curve solution from low to high, plotting a calibration curve with the concentration of the analyte as the x-axis and the intensity ratio of the analyte to the internal standard reference line as the y-axis, and outputting the concentration of arsenic in the low-carbon ferromanganese sample; suitable for low-carbon ferromanganese samples with a manganese content of 50%~80%. The purpose of this invention is to provide a simple, rapid, accurate, and low-detection-limit ICP-MS method for determining the arsenic content in low-carbon ferromanganese.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical analysis technology, and in particular relates to a method for determining the arsenic content in ferromanganese by ICP-MS. Background Technology

[0002] Ferromanganese, a core alloying raw material in the steelmaking industry, is mainly used for deoxidation, desulfurization, and alloying of steel. The content of arsenic, an impurity element, directly affects the quality and safety of the steel. Arsenic easily forms brittle phases (such as Fe3As) in steel, leading to decreased toughness and increased hot brittleness sensitivity, which can severely cause rolling cracking or component failure. Simultaneously, the presence of arsenic reduces the corrosion resistance and weldability of steel. Therefore, the steelmaking industry both domestically and internationally imposes strict limits on the arsenic content in ferromanganese. According to the GB / T 3795-2020 standard for ferromanganese, the arsenic content of high-quality ferromanganese must be controlled below 0.10%, and for high-end special steels, the arsenic content must be below 0.05%. Accurate determination of the arsenic content in ferromanganese is a crucial step in ensuring the safety of steel production and product quality.

[0003] Currently, the mainstream methods used in industry for detecting manganese, iron, and arsenic content have significant technical limitations: First, traditional chemical methods (such as the molybdenum blue spectrophotometric method specified in GB / T 5686.4-2022) require multiple pretreatment steps, including alkali fusion, acid dissolution, and extraction separation, making the operation cumbersome (each analysis cycle takes 3-5 hours), and the detection limit is only 0.01%, which cannot meet the accurate detection requirements for low-arsenic manganese, iron (<0.05%). Second, although atomic absorption spectrometry (AAS) is relatively simple to operate, the high manganese content (50%-80%) in the manganese, iron matrix will produce strong matrix interference, inhibiting the atomization efficiency of arsenic, resulting in a relative detection error exceeding 8%, and it can only detect single elements, making it unsuitable for simultaneous analysis of multiple impurity elements. Third, although the ICP-AES method has multi-element analysis capabilities, the characteristic spectral lines of arsenic (such as 193.759 nm) are easily affected by manganese (193.761 nm) and iron (193.755 nm). The spectral overlap and interference of matrix elements such as nm) result in insufficient signal-to-noise ratio when detecting low arsenic content (<0.03%), making it difficult to meet the precision requirements of high-end steelmaking.

[0004] Inductively coupled plasma mass spectrometry (ICP-MS) boasts ultra-high sensitivity (detection limit down to ppb / ppt level) and a wide linear range (10⁻⁶ ppm). 6 With its advantages such as easy correction of mass spectrometry interference and simultaneous detection of multiple elements, it has shown application potential in the field of trace harmful element detection in alloys.

[0005] However, there is still a critical gap in the application of existing ICP-MS technology for the detection of arsenic content in ferromanganese. Currently, there is no ICP-MS detection standard for arsenic content in ferromanganese, and existing technology cannot meet the needs of rapid and accurate quality control of ferromanganese raw materials.

[0006] Therefore, developing an ICP-MS detection method adapted to the high-manganese matrix characteristics of ferromanganese, effectively eliminating matrix-mass spectrometry interference, and possessing both trace detection capability and analytical efficiency, to address the problems of high detection limits, severe interference, and limitations in the application of existing ICP-MS methods, has become an urgent need to ensure the quality of steelmaking raw materials and the production of high-end steel. Based on the above situation, this invention proposes an ICP-MS method for determining the arsenic content in low-carbon ferromanganese. Summary of the Invention

[0007] To address the shortcomings of existing detection methods, the purpose of this invention is to provide a simple, rapid, accurate, and low-detection-limit ICP-MS method for determining the arsenic content in low-carbon ferromanganese, achieving precise detection within the low arsenic content range of 0.0001% to 0.02%, thus meeting the quality control requirements of high-end steelmaking for ferromanganese raw materials.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] This invention discloses a method for determining the arsenic content in ferromanganese using ICP-MS, comprising: weighing a certain amount of sample, dissolving it in a steel volumetric flask with nitric acid, cooling and making up to volume, and then shaking well; nebulizing the solution and introducing it into an inductively coupled plasma mass spectrometer, and determining the arsenic content using plasma mass spectrometry; finally, plotting a working curve using arsenic standard solutions with a concentration gradient, measuring the intensity ratio of the analyte to the internal standard reference line in the working curve solution from low to high, plotting a calibration curve with the concentration of the analyte as the abscissa and the intensity ratio of the analyte to the internal standard reference line as the ordinate, and outputting the concentration of arsenic in the low-carbon ferromanganese sample; suitable for low-carbon ferromanganese samples with a manganese content of 50%~80%.

[0010] Further, weigh 0.1000 g of the sample, accurate to 0.0002 g.

[0011] Furthermore, the weighed sample was placed in a 100 mL steel volumetric flask, 10 mL of nitric acid was added, and the flask was heated on a 200 ℃ hot plate until the sample was completely dissolved. After cooling, the volume was adjusted with deionized water and shaken well. At the same time, a blank solution was prepared: only 10 mL of nitric acid + deionized water was used to adjust the volume.

[0012] Furthermore, the curves were plotted as follows: 10 mL of nitric acid was added to five 100 mL volumetric flasks, followed by 0.01 mL, 0.05 mL, 0.1 mL, 1.0 mL, and 2.0 mL of 10 μg / mL arsenic standard solution, respectively. After dilution to volume, the solutions were shaken well to obtain a series of standard solutions with arsenic concentrations of 0.0001%, 0.0005%, 0.001%, 0.01%, and 0.02%.

[0013] Furthermore, the detection limit of this invention reaches 0.0001%, meeting the trace detection requirements for ferromanganese used in high-end special steels and filling the technical gap that traditional methods cannot detect low-arsenic ferromanganese.

[0014] Furthermore, accuracy and precision are significantly improved: recovery rate is between 97% and 106%, RSD is only 0.80%; linear correlation coefficient of calibration curve R² = 0.999.

[0015] Furthermore, this method has an analysis cycle of only 20 minutes.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0017] Accurate analysis of arsenic content in low- and medium-carbon ferromanganese is crucial for basic research and process innovation. To this end, we have developed an ICP-MS method for determining the arsenic content in low- and medium-carbon ferromanganese. This method has been applied in production practice, yielding accurate results. It is an effective and practical method with the following core advantages:

[0018] 1. Significantly reduced detection limit: The detection limit of this invention reaches 0.0001%, which can meet the trace detection requirements of ferromanganese (arsenic content <0.05%) for high-end special steel, and fill the technical gap that traditional methods cannot detect low-arsenic ferromanganese.

[0019] 2. Significantly improved accuracy and precision: Recovery rate is between 97% and 106%, with an RSD of only 0.80%; the linear correlation coefficient of the calibration curve is R²=0.999, effectively overcoming matrix suppression interference, spectral overlap interference, and calibration bias issues in the reference documents, resulting in more reliable test results.

[0020] 3. Significantly improved analysis efficiency: The analysis cycle is only 20 minutes, with no need for cumbersome preprocessing steps, making it suitable for rapid quality control scenarios in industrial production.

[0021] 4. Simple operation and strong stability: Pretreatment only requires nitric acid dissolution and heating, without the need for complex steps such as alkali fusion and extraction, reducing the difficulty of operation and the risk of contamination; optimized instrument parameters and dedicated internal standard combination improve the stability of the detection process, making it suitable for routine testing in metallurgical production lines and research institutes. Detailed Implementation

[0022] A method for determining the arsenic content in ferromanganese by ICP-MS includes:

[0023] 1. Scope

[0024] This method specifies the determination of arsenic content in low-carbon manganese iron using inductively coupled plasma mass spectrometry.

[0025] Measurement range: As: 0.0001%~0.02%.

[0026] 2. Method Summary

[0027] A certain amount of sample was weighed and dissolved in nitric acid in a 100 mL steel volumetric flask. After the solution cooled, it was diluted to volume and shaken well. The arsenic content was determined using an ICP-MS instrument with optimized parameters, using rhodium as an internal standard, through a calibration curve method, achieving low-interference and high-precision detection.

[0028] 3. Reagents and Materials

[0029] 3.1 Nitric acid, ρ approx. 1.42 g / mL (analytical grade, to avoid interference from reagent impurities);

[0030] 3.2 Arsenic standard solution, 1000 μg / mL, diluted to 10 μg / mL before use;

[0031] 3.3 Rhodium internal standard solution, 1000 μg / mL, diluted to 10 μg / mL before use;

[0032] 3.4 Deionized water, resistivity ≥18.2 MΩ・cm (to reduce blank interference).

[0033] 4. Main instruments and testing conditions

[0034] 4.1 ELAN DRC-e ICP-MS (PE Corporation, USA).

[0035] 4.2 Instrument parameters:

[0036] Power 1100 W; Plasma gas flow rate 15 L / min; Auxiliary gas flow rate 1.2 L / min; Carrier gas flow rate 0.85 L / min; Injection speed 1.5; Lens voltage 6.25V;

[0037] Sampling cone φ1.1; Truncation cone φ0.9; Scanning mode: peak skipping; Number of repetitions: 2.

[0038] 4.3 The element to be tested is arsenic (75); the internal standard element is rhodium (103).

[0039] 5. Analysis Steps

[0040] 5.1 Sample Quantity

[0041] Weigh 0.1000 g of the sample, accurate to 0.0002 g.

[0042] 5.2 Measurement Procedure

[0043] Place the weighed sample in a 100 mL steel volumetric flask, add 10 mL of nitric acid, and heat on a 200 ℃ hot plate to dissolve (about 15 minutes) until the sample is completely dissolved. After cooling, dilute to volume with deionized water and shake well. At the same time, prepare a blank solution (dilute to volume with only 10 mL of nitric acid and deionized water).

[0044] 5.3 Drawing Curves

[0045] Add 10 mL of nitric acid to five 100 mL volumetric flasks, and then add 0.01 mL, 0.05 mL, 0.1 mL, 1.0 mL, and 2.0 mL of 10 μg / mL arsenic standard solution, respectively. After making up to volume, shake well to obtain a series of standard solutions with arsenic concentrations of 0.0001%, 0.0005%, 0.001%, 0.01%, and 0.02%.

[0046] 6 Results and Discussion

[0047] 6.1 Accuracy Experiment

[0048] Weigh out low- and medium-carbon ferromanganese samples and perform spiked recovery experiments according to this method. The results are shown in Table 1.

[0049] Table 1. Accuracy of Measurement Results (%)

[0050] Sample number initial value scalar Detection value Recovery rate scalar Detection value Recovery rate scalar Detection value Recovery rate S1 0.0041 0.0010 0.0051 100.0% 0.0020 0.0061 100.0% 0.0030 0.0070 96.7% S2 0.0100 0.0030 0.0131 103.3% 0.0050 0.0151 102.0% 0.0080 0.0179 98.8% S3 0.0120 0.0040 0.0158 95.0% 0.0050 0.0173 106.0% 0.0100 0.0218 98.0% average value - - - 99.4% - - 102.7 - - 97.8

[0051] The data in the table show that the average recoveries at low, medium, and high spiking concentrations were 99.4%, 102.7%, and 97.8%, respectively, all within the acceptable range of 95% to 105% for trace analysis. This demonstrates that the method is accurate and reliable across the entire detection range and has no concentration-dependent error.

[0052] 6.2 Precision Experiment

[0053] Eleven samples of the same low-carbon manganese-iron mixture (arsenic content 0.0122%) were weighed and tested in parallel according to this method. Inter-laboratory comparison data were also supplemented. The results are shown in Table 2.

[0054] Table 2 Precision of Measurement Results (%)

[0055] Testing conditions Detection value 1 Detection value 2 Detection value 3 Detection value 4 Detection value 5 Detection value 6 Detection value 7 Detection value 8 Detection value 9 Detection value 10 Detection value 11 average value Relative standard deviation (RSD) Same laboratory 0.0121 0.0123 0.0122 0.0120 0.0123 0.0122 0.0121 0.0123 0.0122 0.0121 0.0123 0.0122 0.80% Laboratory A 0.0122 0.0123 0.0121 - - - - - - - - 0.0122 0.82% Laboratory B 0.0123 0.0121 0.0122 - - - - - - - - 0.0122 0.81% Laboratory C 0.0121 0.0122 0.0123 - - - - - - - - 0.0122 0.83%

[0056] The data above show that the RSD of 11 parallel tests in the same laboratory is only 0.80%, and the RSD of comparisons between three different laboratories is ≤0.83%, which is far below the industry-recognized threshold of 3%. This proves that the method has excellent repeatability and reproducibility and is not affected by differences in laboratory environment and operators.

[0057] 6.3 Compatibility Experiment of Samples with Different Manganese Matrix Content

[0058] Five low-carbon ferromanganese samples with different manganese contents (50%~80%) were selected and tested using the method of this invention to verify matrix compatibility. The results are shown in Table 3.

[0059] Table 3. Detection results (%) of samples with different manganese matrix contents

[0060] Sample number manganese content Actual value of arsenic Detection value absolute error relative error RSD (5 parallels) M1 50% 0.0052 0.0053 +0.0001 +1.9% 0.75% M2 60% 0.0081 0.0082 +0.0001 +1.2% 0.78% M3 70% 0.0113 0.0115 +0.0002 +1.8% 0.82% M4 75% 0.0156 0.0158 +0.0002 +1.3% 0.85% M5 80% 0.0189 0.0191 +0.0002 +1.1% 0.88%

[0061] 7. Conclusion

[0062] This invention constructs an ICP-MS detection method adapted to high-manganese matrices of low- and medium-carbon ferromanganese, solving the technical problems of high detection limits, severe interference, and low efficiency in existing methods. This method achieves a detection limit of 0.0001%, a recovery rate of 97.8%–102.7%, an RSD of 0.80%, and an analysis cycle of only 20 minutes. It is suitable for low- and medium-carbon ferromanganese samples with a manganese content of 50%–80%, is simple to operate, and provides accurate results. It can meet the rapid quality control needs of low-arsenic ferromanganese in the metallurgical industry and has broad application value.

[0063] Those skilled in the art generally believe that "the higher the manganese content, the more difficult it is to suppress matrix interference." However, this invention breaks through this limitation through parameter synergistic optimization. This adaptability is not a simple "parameter fine-tuning," but rather based on in-depth research on the interaction mechanism between high-manganese matrix and arsenic detection, which is a non-obvious technical breakthrough.

[0064] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for determining the arsenic content in ferromanganese by ICP-MS, characterized in that: include: Weigh a certain amount of sample, dissolve it in nitric acid in a steel volumetric flask, cool and dilute to volume, then shake well. Introduce the solution into an inductively coupled plasma mass spectrometer (ICP-MS) to determine the arsenic content. Finally, plot a working curve using arsenic standard solutions with varying concentration gradients. Measure the intensity ratio of the analyte to the internal standard reference line in the working curve solution from low to high. Plot a calibration curve with the concentration of the analyte on the x-axis and the intensity ratio of the analyte to the internal standard reference line on the y-axis. Output the concentration of arsenic in the low-carbon ferromanganese sample. This method is suitable for low-carbon ferromanganese samples with a manganese content of 50%–80%.

2. The method for determining the arsenic content in ferromanganese by ICP-MS according to claim 1, characterized in that: Weigh 0.1000 g of the sample, accurate to 0.0002 g.

3. The method for determining the arsenic content in ferromanganese by ICP-MS according to claim 2, characterized in that: Place the weighed sample in a 100 mL steel volumetric flask, add 10 mL of nitric acid, and heat on a 200 ℃ hot plate until the sample is completely dissolved. After cooling, dilute to volume with deionized water and shake well. At the same time, prepare a blank solution: dilute to volume with only 10 mL of nitric acid and deionized water.

4. The method for determining the arsenic content in ferromanganese by ICP-MS according to claim 1, characterized in that: Curve plotting: Add 10 mL of nitric acid to five 100 mL volumetric flasks, and then add 0.01 mL, 0.05 mL, 0.1 mL, 1.0 mL, and 2.0 mL of 10 μg / mL arsenic standard solution, respectively. After dilution to volume, shake well to obtain a series of standard solutions with arsenic concentrations of 0.0001%, 0.0005%, 0.001%, 0.01%, and 0.02%.

5. The method for determining the arsenic content in ferromanganese by ICP-MS according to claim 1, characterized in that: The detection limit of this invention is 0.0001%, which meets the trace detection requirements of ferromanganese for high-end special steel and fills the technical gap that traditional methods cannot detect low-arsenic ferromanganese.

6. The method for determining the arsenic content in ferromanganese by ICP-MS according to claim 1, characterized in that: Accuracy and precision are significantly improved: recovery rate is between 97% and 106%, RSD is only 0.80%; linear correlation coefficient of calibration curve R² = 0.

999.

7. The method for determining the arsenic content in ferromanganese by ICP-MS according to claim 1, characterized in that: The analysis cycle of this method is only 20 minutes.