Method for detecting zinc content in lithium-zinc binary alloy strip based on ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometer)

Abstract

The invention provides a method for detecting the content of zinc in a lithium-zinc binary alloy strip based on ICP-OES, and belongs to the technical field of metal material component analysis. According to the method, the lithium matrix is separated by adopting a nitric acid-perchloric acid digestion system, and the stock solution is diluted by 500 times, so that the concentration of the lithium matrix can be efficiently reduced, meanwhile, the signal inhibition effect is effectively eliminated by combining lithium salt matching, and the detection precision is greatly improved. According to the method, Zn 213.856 nm analysis spectral lines are carefully selected, RF power is optimized, spectral interference of other elements can be avoided, the linear range can be expanded, and the method is suitable for rapid determination of the zinc content of 1%-20%. According to the method, the detection limit can reach 0.01%, the relative standard deviation is smaller than or equal to 1.0%, the recovery rate is 98.5%-101.2%, and high-precision detection is achieved.

Description

Technical Field

[0001] This invention relates to the field of metal material composition analysis technology, and in particular to a method for detecting zinc content in lithium-zinc binary alloy strips based on ICP-OES. Background Technology

[0002] Lithium-zinc alloy strips have broad application prospects in batteries, electronic devices, and other fields, and the precise control of zinc content is crucial to material performance. Currently used detection methods have certain shortcomings. For example, chemical titration is affected by high-concentration lithium matrix interference, and the endpoint determination error is large at low zinc contents; atomic absorption spectrometry suffers from lithium matrix effects, resulting in unsatisfactory detection accuracy; traditional inductively coupled plasma atomic emission spectrometry requires matrix matching or standard addition methods to eliminate interference, but improvements are still needed in sample pretreatment and instrument parameter optimization for alloy strips.

[0003] Several invention patents have been developed to address the problem of accurately detecting zinc content in lithium-zinc alloy strips. For example, patent CN111307788A discloses a method for determining the total zinc content in textiles using microwave digestion-assisted inductively coupled plasma atomic emission spectrometry. This method uses microwave digestion as a pretreatment, which is time-efficient and eliminates the need for perchloric acid during digestion, thus improving measurement sensitivity and precision. However, this method still requires further optimization of digestion conditions, the digestion system, filtration effectiveness, and sensitivity.

[0004] Patent CN117664695A discloses a method for detecting the lanthanum content in aluminum-zinc ingots. This method provides accurate and reliable data, is fast, and has low cost. However, further optimization of the sample preparation method is needed to improve the extraction efficiency and purity of the sample. Summary of the Invention

[0005] The purpose of this invention is to provide a method for detecting zinc content in lithium-zinc binary alloy strips based on ICP-OES, which solves the technical problems in the prior art such as interference from high-concentration lithium matrix, insufficient detection accuracy, and inadequate pretreatment and instrument parameter optimization when detecting zinc content in lithium-zinc alloy strips.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for detecting zinc content in lithium-zinc binary alloy strips based on ICP-OES, comprising the following steps: Step 1) Dissolve the sample in nitric acid solution, then add perchloric acid solution and hydrochloric acid solution in sequence, and make up to volume to obtain the stock solution; Step 2) Dilute the stock solution to obtain a diluted solution, and prepare a series of lithium-containing zinc standard solutions according to the lithium concentration of the diluted solution; Step 3) The emission intensity of zinc in the diluted solution and a series of zinc standard solutions was measured by ICP-OES. Then, a standard curve was plotted with concentration on the x-axis and emission intensity on the y-axis based on the measurement results of the series of standard solutions. Step 4) Calculate the zinc content in the sample based on the standard curve; In step 1), the zinc content of the sample is 1~20 wt%; In step 3), the fluctuation value of lithium concentration in the diluent and the series of zinc standard solutions is <3%.

[0007] Furthermore, in step 1), the dissolution is a low-temperature dissolution, with a dissolution temperature of 50~70℃ and a dissolution time of 5~15min; After adding the perchloric acid solution, heating is performed at a temperature of 150~170℃ for 8~15 minutes. The temperature at which the hydrochloric acid solution is added is 18~30℃.

[0008] Furthermore, in step 1), the mass concentration of the nitric acid solution is 60-70%, the mass concentration of the perchloric acid solution is 65-75%, and the mass concentration of the hydrochloric acid solution is 35-45%. The ratio of the sample, nitric acid solution, perchloric acid solution, and hydrochloric acid solution used is 0.1~0.5g: 3~7mL: 3~7mL: 5~8mL; The volume was adjusted to 100 mL.

[0009] Furthermore, in step 2), the concentration of zinc in the series of zinc standard solutions is independently 0.1~30 mg / L, and the concentration of lithium is independently 50~100 mg / L.

[0010] Furthermore, in step 3), the parameters of the ICP-OES are: RF power of 1150~1300W, carrier gas flow rate of 0.7~0.9L / min, and integration time of 20 seconds; The analytical spectral line is Zn at 213.856 nm, and the background equivalent concentration of the spectral line is ≤0.003 mg / L; ICP-OES uses a vertical observation direction.

[0011] The beneficial effects of this invention are: This invention successfully overcomes the technical challenges faced by existing chemical titration, atomic absorption spectrometry, and traditional ICP-OES methods in determining the zinc content in lithium-zinc alloy strips, such as matrix interference and difficulty in detecting low concentrations.

[0012] This invention uses a nitric acid-perchloric acid digestion system to separate the lithium matrix and dilutes the original solution by 500 times, which can efficiently reduce the lithium matrix concentration. At the same time, combined with lithium salt matching, it can effectively eliminate the signal suppression effect and significantly improve the detection accuracy.

[0013] This invention carefully selects the Zn 213.856nm analytical spectral line and optimizes the RF power to 1150~1300W, which not only avoids spectral interference from other elements but also expands the linear range, making it suitable for rapid determination of zinc content in the range of 1~20%. The method achieves a detection limit of 0.01%, a relative standard deviation of ≤1.0%, and a recovery rate of 98.5%~101.2%, realizing high-precision detection.

[0014] This invention requires no complicated pretreatment steps, takes less than 20 minutes per test, is simple and efficient to operate, and significantly improves testing efficiency and reduces testing costs. Detailed Implementation

[0015] This invention provides a method for detecting zinc content in lithium-zinc binary alloy strips based on ICP-OES, comprising the following steps: Step 1) Dissolve the sample in nitric acid solution, then add perchloric acid solution and hydrochloric acid solution in sequence, and make up to volume to obtain the stock solution; Step 2) Dilute the stock solution to obtain a diluted solution, and prepare a series of lithium-containing zinc standard solutions according to the lithium concentration of the diluted solution; Step 3) The emission intensity of zinc in the diluted solution and a series of zinc standard solutions was measured by ICP-OES. Then, a standard curve was plotted with concentration on the x-axis and emission intensity on the y-axis based on the measurement results of the series of standard solutions. Step 4) Calculate the zinc content in the sample based on the standard curve; In step 1), the zinc content of the sample is 1~20 wt%; In step 3), the fluctuation value of lithium concentration in the diluent and the series of zinc standard solutions is <3%.

[0016] In this invention, in step 1), the dissolution is a low-temperature dissolution, with a dissolution temperature of 50~70℃, preferably 60℃; and a dissolution time of 5~15min, preferably 7~13min. After adding the perchloric acid solution, the mixture is heated to a temperature of 150-170°C, preferably 155-165°C, for a duration of 8-15 minutes, preferably 10-13 minutes. The temperature at which the hydrochloric acid solution is added is 18~30℃, preferably 20~27℃, and more preferably 24~26℃.

[0017] In this invention, in step 1), the mass concentration of the nitric acid solution is 60-70%, preferably 65%; the mass concentration of the perchloric acid solution is 65-75%, preferably 70%; and the mass concentration of the hydrochloric acid solution is 35-45%, preferably 37%. The ratio of the sample, nitric acid solution, perchloric acid solution, and hydrochloric acid solution used is 0.1~0.5g:3~7mL:3~7mL:5~8mL, preferably 0.1~0.5g:5mL:3mL:5mL; The volume was adjusted to 100 mL.

[0018] In this invention, in step 1), as a preferred embodiment, when the zinc content of the lithium-zinc binary alloy strip is 1~5wt%, the mass of the sample taken is 0.5g; when the zinc content of the lithium-zinc binary alloy strip is 5~20wt%, the mass of the sample taken is 0.1g.

[0019] In this invention, in step 2), the concentration of zinc in the series of zinc standard solutions is independently 0.1~30 mg / L, preferably 1~20 mg / L; the concentration of lithium is independently 50~100 mg / L, preferably 60~90 mg / L, and more preferably 80 mg / L.

[0020] In this invention, in step 2), the diluent is preferably a 5wt% hydrochloric acid solution.

[0021] In this invention, in step 3), the parameters of the ICP-OES are: RF power of 1150~1300W, preferably 1200~1250W; carrier gas flow rate of 0.7~0.9L / min, preferably 0.8L / min; and integration time of 20 seconds.

[0022] In this invention, in step 3), as a preferred embodiment, the analytical spectral line is the Zn 213.856nm analytical spectral line, and the background equivalent concentration of the spectral line is ≤0.003mg / L; ICP-OES uses a vertical observation direction.

[0023] In this invention, in step 3), the selection of the Zn 213.856nm analytical spectral line is used to avoid interference from Fe 213.859nm and Co 213.856nm.

[0024] In this invention, in step 3), the interference correction of the ICP-OES adopts background subtraction of spectral interference, specifically two-point background correction to eliminate spectral interference.

[0025] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0026] Example 1

[0027] Weigh 0.5000 g of lithium-zinc alloy strip sample (zinc content approximately 1.0%) and place it in a polytetrafluoroethylene beaker. Then add 5 mL of 65 wt% nitric acid solution and stir magnetically at 50 °C for 10 min. After the reaction stabilizes and no violent bubbles appear, add 3 mL of 70 wt% perchloric acid solution and heat at 150 °C for 10 min to remove the nitric acid. White fumes will be emitted after heating. Continue heating for another 5 min to ensure complete decomposition. Cool to room temperature and add 5 mL of 37 wt% hydrochloric acid solution to the system. After the residue dissolves, transfer to a 100 mL volumetric flask and dilute to volume with deionized water to obtain the stock solution (lithium concentration approximately 70 mg / L). Transfer 2.00 mL of the stock solution to a 100 mL volumetric flask and dilute to volume with 5 wt% hydrochloric acid solution to obtain a 50-fold dilution. Transfer 0.100 mL, 0.200 mL, 0.500 mL, 1.00 mL, and 2.00 mL of zinc standard stock solution (zinc concentration of 1000 mg / L and lithium concentration of 70 mg / L) to five 100 mL volumetric flasks and dilute to volume with 5 wt% hydrochloric acid solution to obtain zinc standard solutions with zinc concentrations of 1.00 mg / L, 2.00 mg / L, 5.00 mg / L, 10.0 mg / L, and 20.0 mg / L, respectively. Select the Zn 213.856nm analysis line and set the ICP-OES instrument parameters as follows: RF power 1200W, carrier gas flow rate 0.8L / min, vertical observation height 10mm, integration time 20s, nebulizer flow rate 0.8L / min, and plasma gas flow rate 15L / min. ICP-OES background correction (two-point background correction) was used to eliminate spectral interference. Then, the emission intensity of zinc in a series of zinc standard solutions was measured. A standard curve (R²) was plotted based on the measurement results of the series of zinc standard solutions, with concentration on the x-axis and emission intensity on the y-axis. 2 (≥0.999), six parallel determinations were performed on six diluted solutions, and the zinc content and relative standard deviation were calculated; Simultaneously perform blank experiments and calculate the detection limit (3 times blank standard deviation / sensitivity). Add 1.00 mL of zinc standard solution (100 mg / L) to the diluent for a spiked recovery test.

[0028] result: Zinc content determination: 0.98%~1.02% (recovery rate 98.0%~102.0%). RSD: 0.6% (≤1.0%) Limit of detection: 0.008% (≤0.01%); The linear range of the standard curve is 1.00~20.0 mg / L (covering the concentration of the diluted sample).

[0029] Example 2

[0030] Weigh 0.1000 g of a lithium-zinc alloy strip sample (zinc content approximately 5.0%) and place it in a polytetrafluoroethylene beaker. Then add 5 mL of 65 wt% nitric acid solution and stir magnetically at 60 °C for 8 min. After the reaction stabilizes and no violent bubbles appear, add 3 mL of 70 wt% perchloric acid solution and heat at 160 °C for 8 min to remove the nitric acid. White fumes will be emitted after heating. Continue heating for another 5 min to ensure complete decomposition. Cool to room temperature and add 5 mL of 37 wt% hydrochloric acid solution to the system. After the residue dissolves, transfer to a 100 mL volumetric flask and dilute to volume with deionized water to obtain the original solution (zinc concentration approximately 50 mg / L, lithium concentration approximately 70 mg / L). Transfer 2.00 mL of the stock solution to a 100 mL volumetric flask and dilute to volume with 5 wt% hydrochloric acid solution to obtain a 50-fold dilution. Transfer 0.100 mL, 0.200 mL, 0.500 mL, 1.00 mL, and 2.00 mL of zinc standard stock solution (zinc concentration of 1000 mg / L and lithium concentration of 70 mg / L) to five 100 mL volumetric flasks and dilute to volume with 5 wt% hydrochloric acid solution to obtain zinc standard solutions with zinc concentrations of 1.00 mg / L, 2.00 mg / L, 5.00 mg / L, 10.0 mg / L, and 20.0 mg / L, respectively. Select the Zn 213.856nm analysis line and set the ICP-OES instrument parameters as follows: RF power 1200W, carrier gas flow rate 0.8L / min, vertical observation height 10mm, integration time 20s, nebulizer flow rate 0.8L / min, and plasma gas flow rate 15L / min. ICP-OES background correction (two-point background correction) was used to eliminate spectral interference. Then, the emission intensity of zinc in a series of zinc standard solutions was measured. A standard curve (R²) was plotted based on the measurement results of the series of zinc standard solutions, with concentration on the x-axis and emission intensity on the y-axis. 2 (≥0.999), six parallel determinations were performed on six diluted solutions, and the zinc content and relative standard deviation were calculated; Simultaneously perform blank experiments and calculate the detection limit (3 times blank standard deviation / sensitivity). Add 1.00 mL of zinc standard solution (100 mg / L) to the diluent for a spiked recovery test.

[0031] result: Zinc content measured: 4.95%~5.05% (recovery rate 99.0%~101.0%). RSD: 0.5% (≤1.0%) Limit of detection: 0.007% (≤0.01%); The standard curve exhibits good linearity in the range of 1.00–20.0 mg / L (R0.0). 2 =0.9995).

[0032] Example 3

[0033] Weigh 0.1000 g of a lithium-zinc alloy strip sample (zinc content approximately 20.0%) and place it in a polytetrafluoroethylene beaker. Then add 5 mL of 65 wt% nitric acid solution and stir magnetically at 70 °C for 5 min. After the reaction stabilizes and no violent bubbles appear, add 3 mL of 70 wt% perchloric acid solution and heat at 170 °C for 5 min to remove the nitric acid. White fumes will be emitted after heating. Continue heating for another 5 min to ensure complete decomposition. Cool to room temperature and add 5 mL of 37 wt% hydrochloric acid solution to the system. After the residue dissolves, transfer to a 100 mL volumetric flask and dilute to volume with deionized water to obtain the stock solution (zinc concentration approximately 200 mg / L, lithium concentration approximately 70 mg / L). Transfer 0.500 mL of the stock solution to a 100 mL volumetric flask and dilute to volume with 5 wt% hydrochloric acid solution to obtain a 200-fold dilution. Transfer 0.100 mL, 0.200 mL, 0.500 mL, 1.00 mL, and 3.00 mL of zinc standard stock solution (zinc concentration of 1000 mg / L and lithium concentration of 70 mg / L) to five 100 mL volumetric flasks and dilute to volume with 5 wt% hydrochloric acid solution to obtain zinc standard solutions with zinc concentrations of 1.00 mg / L, 2.00 mg / L, 5.00 mg / L, 10.0 mg / L, and 30.0 mg / L, respectively. The Zn 213.856nm analytical line was selected, and the ICP-OES instrument parameters were set as follows: RF power 1250W, carrier gas flow rate 0.8L / min, vertical observation height 10mm, integration time 20s, nebulizer flow rate 0.8L / min, and plasma gas flow rate 15L / min. ICP-OES background correction (two-point background correction) was used to eliminate spectral interference. Then, the emission intensity of zinc in a series of zinc standard solutions was measured. A standard curve (R²) was plotted based on the measurement results of the series of zinc standard solutions, with concentration on the x-axis and emission intensity on the y-axis. 2 (≥0.999), six parallel determinations were performed on six diluted solutions, and the zinc content and relative standard deviation were calculated; Simultaneously perform blank experiments and calculate the detection limit (3 times blank standard deviation / sensitivity). Add 0.500 mL of zinc standard solution (1000 mg / L) to the diluent for a spiked recovery test.

[0034] result: Zinc content measured: 19.8%~20.2% (recovery rate 99.0%~101.0%). RSD: 0.7% (≤1.0%) Limit of detection: 0.006%; Linear range of the standard curve: 1.00~30.0 mg / L (R 2 =0.9998).

[0035] As can be seen from the above embodiments, the present invention provides a method for detecting zinc content in lithium-zinc binary alloy strips based on ICP-OES. This method uses a nitric acid-perchloric acid digestion system to separate the lithium matrix. The stock solution is diluted 500 times, and the standard solution and test solution maintain the same lithium concentration and hydrochloric acid medium. Combined with the selection of ICP-OES parameters and spectral lines, efficient dilution and matrix matching are achieved, reducing the lithium matrix concentration and eliminating signal suppression effects. This method has advantages such as a wide linear range, high-precision detection, and simple operation.

[0036] This method is applicable to alloy strips with a zinc content of 1-20 wt%, achieving a detection accuracy of 0.01%, a relative standard deviation of ≤1.0%, and a recovery rate of 98.5-101.2%. It requires no complex pretreatment and the single detection time is less than 20 minutes. This method provides an effective approach for the accurate detection of zinc content in lithium-zinc alloy strips.

[0037] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for detecting zinc content in lithium-zinc binary alloy strips based on ICP-OES, characterized in that, Includes the following steps: Step 1) Dissolve the sample in nitric acid solution, then add perchloric acid solution and hydrochloric acid solution in sequence, and make up to volume to obtain the stock solution; Step 2) Dilute the stock solution to obtain a diluted solution, and prepare a series of lithium-containing zinc standard solutions according to the lithium concentration of the diluted solution; Step 3) The emission intensity of zinc in a series of zinc standard solutions was determined by ICP-OES. Then, a standard curve was plotted with concentration on the x-axis and emission intensity on the y-axis based on the measurement results of the series of standard solutions. Step 4) Under the same conditions, the zinc emission intensity of the diluted solution was measured in parallel, and then the zinc content in the sample was calculated according to the standard curve. In step 1), the zinc content of the sample is 1~20 wt%; The fluctuation in lithium concentration in the diluent and series of zinc standard solutions is <3%.

2. The method for detecting zinc content in lithium-zinc binary alloy strips based on ICP-OES according to claim 1, characterized in that, In step 1), the dissolution is a low-temperature dissolution, with a dissolution temperature of 50~70℃ and a dissolution time of 5~15min; After adding the perchloric acid solution, heating is performed at a temperature of 150~170℃ for 8~15 minutes. The temperature at which the hydrochloric acid solution is added is 18~30℃.

3. A method for detecting zinc content in lithium-zinc binary alloy strips based on ICP-OES according to claim 1 or 2, characterized in that, In step 1), the mass concentration of the nitric acid solution is 60-70%, the mass concentration of the perchloric acid solution is 65-75%, and the mass concentration of the hydrochloric acid solution is 35-45%. The ratio of the sample, nitric acid solution, perchloric acid solution, and hydrochloric acid solution used is 0.1~0.5g: 3~7mL: 3~7mL: 5~8mL; The volume was adjusted to 100 mL.

4. The method for detecting zinc content in lithium-zinc binary alloy strips based on ICP-OES according to claim 3, characterized in that, In step 2), the zinc concentration in the series of zinc standard solutions is independently 0.1~30 mg / L, and the lithium concentration is independently 50~100 mg / L.

5. A method for detecting zinc content in lithium-zinc binary alloy strips based on ICP-OES according to claim 1, 2, or 4, characterized in that, In step 3), the parameters of the ICP-OES are: RF power of 1150~1300W, carrier gas flow rate of 0.7~0.9L / min, and integration time of 20 seconds; The analytical spectral line is Zn at 213.856 nm, and the background equivalent concentration of the spectral line is ≤0.003 mg / L; ICP-OES uses a vertical observation direction.