Method for measuring content of rare earth in galvanized sheet coating

Abstract

The invention discloses a method for measuring the content of rare earth in a galvanized sheet coating, which comprises the following steps: 1) weighing a certain amount of galvanized sheet sample, dissolving in a hexamethylenetetraammonium salt acid solution, and after the reaction is stopped, obtaining a dissolved sample; 2) transferring the dissolved sample obtained in the step 1) into a volumetric flask, and diluting to a constant volume; and (3) measuring the content of the rare earth by using a plasma mass spectrometer. According to the method, accurate data can be provided for the content of lanthanum and cerium in the plating layer of the galvanized sheet.

Description

Technical Field

[0001] The invention belongs to the technical field of steel material analysis, and specifically relates to a method for determining the rare earth content in a galvanized sheet coating, and in particular to a method for determining the lanthanum and cerium contents in a galvanized sheet coating by using a plasma mass spectrometry method. Background Art

[0002] Galvanized sheet products with rare earth added to the coating have excellent corrosion resistance, good processing formability, cut self-repairing properties, and friction resistance. The products are green and environmentally friendly and can be widely used in photovoltaics, animal husbandry, home appliances, automobiles and other fields. For the detection of lanthanum and cerium in the coating of galvanized sheet, plasma spectroscopy and direct reading spectroscopy can be used. The accuracy of plasma spectroscopy in determining trace rare earths is not high, and direct reading spectroscopy is fast in determining each element in the coating, but it is difficult to detect rare earth elements. The low content of rare earth elements is very important for improving material performance, and there is currently a lack of relevant detection methods. Summary of the invention

[0003] In view of one or more problems existing in the prior art, the present invention provides a method for determining the rare earth content in a galvanized sheet coating, which comprises the following steps:

[0004] 1) Weigh a certain amount of galvanized sheet sample, dissolve it in hexamethylenetetraammonium hydrochloric acid solution, and obtain a dissolved sample after the reaction stops;

[0005] 2) transferring the dissolved sample obtained in step 1) into a volumetric flask and diluting to a fixed volume;

[0006] 3) Determine the rare earth content using an inductively coupled plasma mass spectrometer.

[0007] In some embodiments, the rare earth is lanthanum and / or cerium.

[0008] In some embodiments, the galvanized sheet sample is pre-treated by alcohol cleaning to remove oil stains on the surface of the sample.

[0009] In some embodiments, the determination method comprises the following operations:

[0010] 1) Place a galvanized sheet sample with a weight of m1 in a beaker, and add hexamethylenetetraammonium hydrochloric acid solution to dissolve the sample coating. After the coating is completely dissolved, take out the galvanized sheet sample with the coating removed, soak and clean it in an alcohol solution, air-dry or blow-dry it, and weigh it as m2, thereby calculating the weight of the coating;

[0011] 2) transferring the dissolved sample obtained in step 1) into a volumetric flask, diluting to a fixed volume and shaking well to obtain a test solution;

[0012] 3) Using an inductively coupled plasma mass spectrometer to measure the rare earth content in the measurement solution obtained in step 2), recorded as ω1%, and calculating the rare earth content in the coating by the following formula:

[0013]

[0014] Where: m1: weight of the sample, in grams (g);

[0015] m2: the weight of the sample after dissolving the coating, in grams (g);

[0016] ω1%: mass spectrometer test results;

[0017] m0: Theoretical sample weight for preparing the curve.

[0018] The method can provide accurate data for the content of rare earth (such as lanthanum and / or cerium) in the galvanized sheet coating. The results of the spike recovery test show that the method of the present invention has a high determination accuracy and has been used in production practice. It is an effective and practical method. DETAILED DESCRIPTION

[0019] The present invention aims to provide a method for determining the rare earth content in a galvanized sheet coating, so as to accurately determine the content of lanthanum and cerium in the galvanized sheet coating. The method is specifically completed by the following steps:

[0020] After the surface oil stains of the galvanized sheet coating sample were cleaned with alcohol, it was weighed and dissolved in a hexamethylenetetraammonium hydrochloric acid solution. After the reaction stopped and the coating on the surface of the sample was completely dissolved, it was transferred to a volumetric flask, diluted to a fixed volume, shaken well, and the lanthanum and cerium contents were determined using an inductively coupled plasma mass spectrometer.

[0021] 1. Reagents and Materials

[0022] Unless otherwise specified, only approved high-purity reagents were used in the analysis and the analytical water complied with the laboratory water specified in GB / T 6682.

[0023] 1.1 hydrochloric acid, ρ1.19 g / mL.

[0024] 1.2 Alcohol, ρ0.79 g / mL.

[0025] 1.3 Hexamethylenetetraammonium, chemically pure.

[0026] 1.4 Hexamethylenetetraammonium hydrochloride solution: Weigh 3.5 g of hexamethylenetetraammonium, dissolve it in 500 mL of concentrated hydrochloric acid, and dilute to 1000 mL with deionized water.

[0027] 1.5 Mass calibration standard solution, 10 μg / L

[0028] This standard solution contains 10 μg of magnesium, rhodium, indium, cerium, lead and uranium in 1L.

[0029] 1.6 Lanthanum standard stock solution, 1000 μg / mL

[0030] Weigh 1.1727g of lanthanum oxide [w(La2O3)≥99.99%] that has been calcined at 950℃ for 1h and cooled to room temperature in a desiccator, place in a 200mL beaker, add 50mL of hydrochloric acid solution (1+1), heat at low temperature until completely dissolved. Cool to room temperature, transfer to a 1000mL volumetric flask, dilute to scale with water, and mix well.

[0031] This standard stock solution contains 1000 μg of lanthanum in 1 mL.

[0032] 1.7 Cerium standard stock solution, 1000 μg / mL

[0033] Weigh 1.2280g of cerium oxide [w(CeO2)≥99.99%] that has been calcined at 750℃ for 30min and cooled to room temperature in a desiccator, place in a 200mL beaker, add 50mL of nitric acid solution (1+1), heat at low temperature to dissolve, add hydrogen peroxide (30%) dropwise until completely dissolved, boil to decompose excess hydrogen peroxide. Cool to room temperature, transfer to a 1000mL volumetric flask, dilute to scale with water, and mix well.

[0034] This standard stock solution contains 1000 μg of cerium per 1 mL.

[0035] 1.8 Lanthanum and cerium mixed standard solution, 10 μg / mL

[0036] Pipette 10.0 mL of lanthanum standard stock solution (1000 μg / mL) and cerium standard stock solution (1000 μg / mL) into a 1000 mL volumetric flask, add 100 mL of hydrochloric acid, dilute to the mark with water, and mix well.

[0037] This standard solution contains 10 μg of lanthanum and cerium per 1 mL.

[0038] 1.9 Lanthanum and cerium mixed standard solution, 1 μg / mL

[0039] Pipette 10.0 mL of lanthanum and cerium mixed standard solution (10 μg / mL) into a 100 mL volumetric flask, add 10 mL of hydrochloric acid, dilute to the mark with water, and mix well.

[0040] This standard solution contains 1 μg of lanthanum and cerium per 1 mL.

[0041] 1.10 Lanthanum and cerium mixed standard solution, 0.1 μg / mL

[0042] Pipette 10.0 mL of lanthanum and cerium mixed standard solution (1 μg / mL) into a 100 mL volumetric flask, add 10 mL of hydrochloric acid, dilute to the mark with water, and mix well.

[0043] This standard solution contains 0.1 μg of lanthanum and cerium per 1 mL.

[0044] 1.11 Cesium standard stock solution, 1000 μg / mL

[0045] Weigh 1.0000g of metallic cesium (mass fraction not less than 99.99%) into a 250mL beaker, add 50mL of water, add 50mL of hydrochloric acid, heat at low temperature to dissolve. Cool, transfer to a 1000mL volumetric flask, dilute to scale with water, and mix well.

[0046] This standard stock solution contains 1000 μg of cesium per 1 mL.

[0047] 1.12 Cesium standard stock solution, 10 μg / mL

[0048] Pipette 10.0 mL of cesium standard stock solution (1000 μg / mL) into a 1000 mL volumetric flask, add 50 mL of hydrochloric acid, dilute to the mark with water, and mix well.

[0049] This standard solution contains 10 μg of cesium per 1 mL.

[0050] 1.13 Cesium internal standard solution, 0.1 μg / mL

[0051] Pipette 10.0 mL of cesium standard stock solution (10 μg / mL) into a 1000 mL volumetric flask, add 50 mL of hydrochloric acid, dilute to the mark with water, and mix well.

[0052] This standard solution contains 0.1 μg of cesium per 1 mL.

[0053] 2. Instruments

[0054] Inductively coupled plasma mass spectrometer (ICP-MS).

[0055] 3. Experimental Methods

[0056] 3.1 Blank test

[0057] Perform blank test with the sample

[0058] 3.2 Determination

[0059] Place the sample in a 100mL beaker, add alcohol and soak the sample for 3 minutes. After cleaning the surface oil, place it in a well-ventilated place until the surface alcohol evaporates completely or use a hair dryer to blow dry the sample, weigh and record the weight, then place it in a 100mL beaker and add 20mL of hexamethylenetetraammonium hydrochloride solution. Gently shake the sample until the surface zinc coating reacts completely. After the reaction stops, clean the substrate and take it out, soak and wash it in the alcohol solution, air dry or blow dry it, weigh it, transfer the solution to a 100mL volumetric flask, dilute it to the scale with water, and shake it well. Use an inductively coupled plasma mass spectrometer to determine the lanthanum and cerium content, calculate the actual sample weight based on the difference between the two weights, and calculate the actual content of lanthanum and cerium in the sample through the mass relationship.

[0060] 3.3 Drawing of working curve

[0061] Take 8 100mL volumetric flasks, add 20mL of hexamethylenetetraammonium hydrochloride solution, add lanthanum and cerium mixed standard solutions according to Table 1, then add 10mL of cesium internal standard solution (0.1μg / mL), dilute to the scale with water, and mix well.

[0062] Table 1: Calibration curve solutions

[0063]

[0064] 3.4 Instrumental determination

[0065] Optimize the instrument according to the instrument manual. Under the selected instrument working conditions, select the mass number of each element according to the isotopic abundance and interference of each element. Measure the intensity of each element in the calibration curve solution (see Table 1) from low concentration to high concentration, and measure the intensity of the internal standard solution at the same time. The net intensity is the intensity of the standard solution of each element minus the intensity of the zero concentration standard solution. Draw the calibration curve with the mass concentration (ng / mL) of the element to be measured as the horizontal coordinate and the ratio of the net intensity of the element to be measured to the net intensity of the internal standard element as the vertical coordinate. The correlation coefficient of the calibration curve should be no less than 0.999.

[0066] Use quality control samples to confirm the calibration curve. Once the requirements are met, measure the mass spectrum intensity of each element to be measured in the test solution, subtract the mass spectrum intensity of the blank test solution, and obtain the net intensity of each element to be measured in the test solution.

[0067] Note 1: Quality control samples can be standard samples, synthetic samples, or samples that are accurately assigned values ​​by other means.

[0068] 3.5 Calculation of analysis results

[0069]

[0070] Where: m1: weight of the sample (after cleaning the surface), in grams (g);

[0071] m2: the weight of the substrate after dissolving the coating (i.e. the sample after removing the coating), in grams (g);

[0072] ω1%: mass spectrometer test results;

[0073] m0: Theoretical sample weight for preparing the curve; for this method, it is 0.1000g.

[0074] 4. Results and Discussion

[0075] 4.1 Precision of the method

[0076] The same sample was measured 10 times continuously to verify the precision of the method, as shown in Table 2.

[0077] Table 2: Method precision experiment

[0078]

[0079] As can be seen from the above table, the RSDs are all less than 5%, so they have good precision.

[0080] 4.2 Accuracy of the method

[0081] The present invention adopts the accuracy of the spike recovery determination method when there is no suitable standard sample. The corresponding addition amount is shown in Table 3.

[0082] Table 3: Method accuracy experiment

[0083]

[0084] It can be seen from Table 3 that the invention can ensure the accuracy of the test results.

[0085] 5. Conclusion

[0086] A large amount of experimental data shows that the present invention provides a reliable analytical method for determining the lanthanum and cerium content in the galvanized sheet coating. The method has the advantages of simple operation, easy mastery, high accuracy and precision of the measurement results, and can fully meet the requirements of detection and analysis, and can provide accurate data support for daily production detection of galvanized sheet coatings, new material research and development, and performance improvement.

[0087] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for determining the rare earth content in a galvanized sheet coating, comprising the following steps: 1) Weigh a certain amount of galvanized sheet sample, dissolve it in hexamethylenetetraammonium hydrochloric acid solution, and obtain a dissolved sample after the reaction stops; 2) transferring the dissolved sample obtained in step 1) into a volumetric flask and diluting to a fixed volume; 3) Determine the rare earth content using an inductively coupled plasma mass spectrometer.

2. The determination method according to claim 1, wherein the rare earth is lanthanum and / or cerium.

3. The measuring method according to claim 1 or 2, wherein the galvanized sheet sample is pre-treated by alcohol cleaning to remove oil stains on the sample surface.

4. The assay method according to any one of claims 1 to 3, comprising the following operations: 1) Place a galvanized sheet sample with a weight of m1 in a beaker, and add hexamethylenetetraammonium hydrochloric acid solution to dissolve the sample coating. After the coating is completely dissolved, take out the galvanized sheet sample with the coating removed, soak and clean it in an alcohol solution, air-dry or blow-dry it, and weigh it as m2, thereby calculating the weight of the coating; 2) transferring the dissolved sample obtained in step 1) into a volumetric flask, diluting to a fixed volume and shaking well to obtain a test solution; 3) Using an inductively coupled plasma mass spectrometer to measure the rare earth content in the measurement solution obtained in step 2), recorded as ω1%, and calculating the rare earth content in the coating by the following formula: Where: m1: weight of the sample, in grams (g); m2: the weight of the sample after dissolving the coating, in grams (g); ω1%: mass spectrometer test results; m0: Theoretical sample weight for preparing the curve.

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