CN109991304B - Method for measuring lead contents of different thicknesses of surface layer of high-voltage electronic optical foil - Google Patents
Method for measuring lead contents of different thicknesses of surface layer of high-voltage electronic optical foil Download PDFInfo
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Abstract
The invention relates to the field of material testing, in particular to a method for measuring lead contents of different thicknesses of a surface layer of a high-voltage electronic optical foil. The method comprises the steps of removing different thicknesses of the surface layer of the high-voltage electronic optical foil by an electrolytic method, measuring the content of lead of the optical foil after removing different thicknesses by ICP-MS respectively, and calculating to obtain the content of lead between the removed different thicknesses of the optical foil. Compared with the existing test methods of the secondary ion mass spectrometer and the glow discharge mass spectrometer, the method can accurately test the lead content of different thicknesses of the surface layer, and has the advantages of simple operation and low test cost.
Description
Technical Field
The invention relates to the field of material testing, in particular to a method for measuring lead contents of different thicknesses of a surface layer of a high-voltage electronic optical foil.
Background
The high-voltage electronic optical foil is an aluminum foil prepared from high-purity aluminum through the processes of fusion casting, rolling, annealing and the like, and is formed into a foil through the processes of electrochemical corrosion and formation, wherein the formed foil is an important element of an aluminum electrolytic capacitor. Generally, the surface layer of the high-voltage electronic optical foil contains a certain amount of lead, and when electrochemical corrosion is carried out, a large amount of dislocation and galvanic cell effect exist near lead particles on the surface layer of the optical foil, so that the lead particles are easy to become the starting points of pores, and the corrosion of the optical foil is caused. The content and distribution of lead in the foil surface layer can influence the density and uniformity of pores during corrosion, and further influence the specific volume of the formed foil obtained after corrosion formation. Therefore, it is very important to measure and control the lead content of different thicknesses of the surface layer of the high-voltage electronic optical foil.
The prior art generally uses a secondary ion mass spectrometer or a glow discharge mass spectrometer to analyze the lead content of the surface layer of the optical foil. However, the secondary ion mass spectrometer and the glow discharge mass spectrometer can only carry out qualitative analysis, and the obtained trend of the lead content along with the thickness is the variation trend, so that the real data of the lead content cannot be obtained. And the two instruments are expensive, and the common laboratory does not have the measuring condition.
Chinese patent CN103364482 uses a microwave digestion inductively coupled plasma mass spectrometer to measure the lead content in the medicinal aluminum foil, and the obtained lead content is the whole lead content of the aluminum foil, and the lead content of different thicknesses of the surface layer of the aluminum foil cannot be obtained, so the lead content of the surface layer of the high-voltage electronic optical foil cannot be measured by directly using the method. Because of the limitation of an inductively coupled plasma mass spectrometer (ICP-MS) on the dilution factor of a sample, the lead content of a test sample solution prepared at the polished part of the high-voltage electronic optical foil is only 0.002-0.05ppb, and the detection limit of lead element of the method is 0.09ppb and is lower than the detection limit, so that the method cannot be used for measuring the lead content of different thicknesses of the surface layer of the high-voltage electronic optical foil.
The method for detecting the lead content on the surface layer of the high-voltage electronic optical foil in the prior art is high in cost and cannot be used for quantification, so that a method for simply and conveniently measuring the lead content of different thicknesses on the surface layer of the high-voltage electronic optical foil in a quantified, low-cost manner is needed.
Disclosure of Invention
The invention aims to provide a method for measuring the content of lead with different thicknesses on the surface layer of a high-voltage electronic optical foil. The method can accurately measure the lead content of different thicknesses of the surface layer, and has simple operation and low measurement cost.
In order to achieve the purpose, the technical scheme is as follows: a method for measuring the content of lead with different thicknesses on the surface layer of a high-voltage electronic optical foil comprises the following steps:
1) and polishing the sample: cutting the high-voltage electronic optical foil to be measured into n strips with the same shape, performing electrolytic polishing after decontamination and annealing, keeping the polishing current and the polishing area unchanged, and sequentially increasing the polishing time to obtain the optical foil strips with different thicknesses removed; wherein the thickness A of the first optical foil strip is removed10, the thickness of the n-th optical foil strip is An，n≥2；
2) And preparing a standard solution: weighing 0.1g of low-lead aluminum foil with lead content less than 10ppb, dissolving the low-lead aluminum foil with aqua regia, and diluting the low-lead aluminum foil with ultrapure water to obtain 500g of solution; then, diluting the 100ppb lead standard solution into standard solutions with lead contents of 0, 0.1, 0.2, 0.5 and 1ppb respectively by using the obtained solution;
3) and preparing a test solution: cutting the polished part D of the nth optical foil strip in the step 1)ng, dissolving with aqua regia, and diluting with ultrapure water to obtain Eng, a test solution;
4) respectively measuring the standard solution prepared in the step 2) and the test solution prepared in the step 3) by ICP-MS, quantifying by adopting a standard curve method, and introducing an internal standard for correction on line to obtain the content of lead in the test solution;
5) calculating the thickness A of the nth optical foil strip according to the formula 1n；
An＝10000*TnI M/(ρ F S2) formula 1
In formula 1:
rho-density of aluminum, 2.7g/cm3；
Tn-polishing time of the nth optical foil strip, wherein the unit is s;
i-polishing current, in units of A;
m-the molar mass of aluminum, 27 g/mol;
s-polished area in cm2；
F-Faraday constant, 96485C/mol;
calculating the thickness A of the nth optical foil strip according to the formula 2nThickness A polished away from the (n-1) th optical foil stripn-1Lead content between omegan；
ωn＝[(A-An-1*2)*En-1*Cn-1/Dn-1-(A-An*2)*En*Cn/Dn]/[(An-1-An)*2]Formula 2
In formula 2:
a-original thickness of the optical foil, with unit of μm;
An-1-the thickness of the (n-1) th optical foil strip, in μm, removed;
An-the thickness of the nth optical foil strip, in μm, removed;
Dn-1-the sample mass of the polished part of the (n-1) th optical foil strip, in g;
En-1the mass of a sample solution prepared by sampling the polished part of the (n-1) th optical foil strip is g;
Dn-the sample mass of the polished section of the nth optical foil strip in g;
Enthe mass of the sample solution prepared by sampling the polished part of the nth optical foil strip is g;
Cn-1the lead content of a test solution prepared by sampling the polished part of the (n-1) th optical foil strip is g/g;
Cnand the lead content of the sample solution prepared by sampling the polished part of the nth optical foil strip is g/g.
The high-voltage electronic optical foil strip is polished on five surfaces (a left side surface, a right side surface, a bottom surface, a front surface and a back surface) of the high-voltage electronic optical foil strip at the same time, and because the thickness of the optical foil is in a micron level, the areas of the left side surface, the right side surface and the bottom surface of the optical foil strip are too small relative to the front surface and the back surface, the result is not greatly influenced, and therefore the parts of the optical foil strip which are polished off are approximately considered to be positioned on the front surface and the back surface during calculation.
Preferably, in the method for measuring the lead content of the surface layer of the high-voltage electronic optical foil with different thicknesses, the polishing current in the step 1) is 0.1-10A, and the polishing time is 1-60 s.
Preferably, in the method for measuring the lead content of the surface layer of the high-voltage electronic optical foil with different thicknesses, the polishing solution in the step 1) is a mixed solution of perchloric acid and ethanol.
Preferably, in the method for measuring the lead content of the surface layers of the high-voltage electronic optical foil with different thicknesses, the polishing solution in the step 1) is a mixed solution of absolute ethyl alcohol and azeotropic perchloric acid according to a volume ratio of 9: l.
Preferably, the method for measuring the content of lead with different thicknesses on the surface layer of the high-voltage electronic optical foil is characterized in that Dn in the step 3) is 0.018 to 0.022g, aqua regia is 2mL, and the mass En of the test solution is 90 to 110 g.
Preferably, in the method for measuring the lead content of the surface layer of the high-voltage electro-optic foil with different thicknesses, the operating conditions of the ICP-MS measurement in the step 4) are as follows:
analysis mode: collision free reaction gas mode
Radio frequency power: 1500w plasma gas flow rate: 15L/min
Flow rate of carrier gas: 0.76L/min make-up gas flow rate: 0.36L/min
Temperature of the atomization chamber: 2 ℃ peristaltic pump speed: 0.1rp s
The stabilizing time is as follows: 20s sample lifting time: 15s
An acquisition mode: sampling depth of a mass spectrogram: 6.0mm
Integration time: 1.2s number of points taken to determine peak pattern: 3
The repeated sampling times are as follows: 3 scan/repeat times: 10.
preferably, the content of lead with different thicknesses on the surface layer of the high-voltage electronic optical foil is measuredThe ICP-MS determination in the step 4), sucking the standard solution with the lead content of 1ppb in the step 2) before the test, tuning the instrument, and changing the tuning monitoring quality into the quality208Pb, and will208The sensitivity for Pb is tuned to a maximum.
Preferably, in the method for measuring the lead content of the high-voltage electronic optical foil with different thicknesses on the surface layer, when the sample solution is fed in the step 4), the sample injection needle is taken out 20s before the reading is finished, and the washing solution is put in.
Preferably, the method for measuring the lead content of the high-voltage electronic optical foil with different thicknesses on the surface layer further comprises the following steps: dissolving a low-lead aluminum foil with the lead content of less than 10ppb by using aqua regia, and diluting by using ultrapure water to obtain 500g of solution; respectively diluting 100ppb lead standard solution into solutions with lead contents of 0.001, 0.002, 0.005 and 0.01ppb by using the obtained solution, measuring the lead content by using ICP-MS, and calculating the standard recovery rate of the lead; the recovery rate is between 70 and 130 percent and is regarded as accurate quantification, and the lowest content which can be accurately quantified is taken as the final quantification limit to obtain the quantification limit of the determination method. Further preferably, this step is performed before step 4).
Preferably, the method for measuring the lead content of the high-voltage electronic optical foil with different thicknesses on the surface layer further comprises the following steps: and (3) measuring the lead content of the standard solution prepared in the step 2) by using ICP-MS (inductively coupled plasma-mass spectrometry), and calculating the relative standard deviation of the measurement result by repeating the step three times. Further preferably, this step is performed before step 4).
Preferably, the method for measuring the lead content of the high-voltage electronic optical foil with different thicknesses on the surface layer further comprises the following steps: 6 parallel samples were prepared as in step 3) and measured by ICP-MS to calculate the mean and relative standard deviation of lead content. Further preferably, this step is performed before step 4).
Preferably, the method for measuring the lead content of the high-voltage electronic optical foil with different thicknesses on the surface layer further comprises the following steps: cutting 0.02g of polished part of any one of the optical foil strips in the step 1), dissolving with 2mL of aqua regia, diluting with ultrapure water to 100g, preparing 9 parts of parallel sample solutions, respectively adding 0.1, 0.2, 0.3 and 0.3g of 100ppb lead standard solution, measuring the lead content by using an ICP-MS instrument, and calculating to obtain the average standard recovery rate of the detection method. Further preferably, this step is performed before step 4).
Preferably, the method for measuring the lead content of the high-voltage electronic optical foil with different thicknesses on the surface layer further comprises the following steps: taking any one of the optical foil strips in the step 1), weighing 0.02g of polished part of the optical foil strip, preparing 9 parts in parallel, adding 100ppb lead standard solutions of 0.1, 0.2, 0.3 and 0.3g respectively, adding 2mL aqua regia, heating until the sample is completely dissolved, cooling, diluting with ultrapure water until the total mass of the solution is 100g, measuring the lead content of the solution by ICP-MS respectively, and calculating to obtain the average additive recovery rate of the pretreatment method. Further preferably, this step is performed after the average spiking recovery of the detection method.
The invention has the beneficial effects that:
1) and polishing the optical foils with different thicknesses on the surface layer of the high-voltage electronic optical foil by adopting electrolytic polishing, measuring the lead content of the optical foil after polishing with different thicknesses by using ICP-MS, and subtracting to obtain the lead content between different thicknesses, thereby overcoming the defect that the lead content on the surface layer of the optical foil can not be measured by using ICP-MS.
2) And aqua regia is adopted to dissolve the optical foil, so that pollution caused by a large amount of acid used for conventional microwave digestion and multiple transfer is avoided.
3) Tuning to lead element will208The sensitivity of Pb is adjusted to the maximum value, and the limit of quantification is as low as 0.002ppb, so that the detection requirement of the lead content of the surface layer of the electronic optical foil can be met.
4) And evaluating the detection capability of the detection method on the low-lead-content sample by calculating the lead standard recovery rate, so that the obtained quantitative limit is more rigorous and reliable.
Definition of terms
The invention is intended to cover alternatives, modifications and equivalents, which may be included within the scope of the invention as defined by the appended claims. Those skilled in the art will recognize that many methods and materials similar or equivalent to those described herein can be used in the practice of the present invention. The present invention is in no way limited to the methods and materials described herein. In the event that one or more of the incorporated documents, patents, and similar materials differ from or contradict this application (including but not limited to defined terminology, terminology application, described techniques, and so on), this application controls.
It will be further appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All patents and publications referred to herein are incorporated by reference in their entirety.
Detailed Description
The following are preferred embodiments of the present invention, and the present invention is not limited to the following preferred embodiments. It should be noted that various changes and modifications based on the inventive concept herein by those skilled in the art are intended to be included within the scope of the invention. The starting materials used in the examples are all commercially available.
Example 1
The instruments and reagents used in the embodiments of the present invention:
agilent 8800s inductively coupled plasma mass spectrometer, ten-thousandth electronic balance, electric hot plate, ultra-pure water machine, DC power supply, electropolishing apparatus, muffle furnace, 100mL PFA beaker, 50mL FEP bottle, 500mL FEP bottle (FEP bottle and PFA beaker have been nitric acid reflux treatment).
Aqua regia, merck 100ppb lead standard solution, absolute ethanol (analytical grade), azeotropic perchloric acid (analytical grade), 100ppb209Bi mixed internal standard solution, low-lead aluminum foil (Pb content is less than 10ppb), and high-voltage electronic optical foil to be measured.
Wherein the aqua regia is prepared on site by concentrated nitric acid and concentrated hydrochloric acid according to the volume ratio of 1:3, wherein the aqua regia is subjected to secondary sub-boiling purification and the Pb content is less than 0.01 ppb; the 100ppb lead standard solution is prepared by diluting 100ppm lead element standard solution mother liquor produced by Merck company; the mixed internal standard solution is prepared by diluting 10ppm mixed internal standard solution mother liquor produced by Agilent company.
TABLE 1 Instrument parameter settings
The following are specific embodiments of the present invention.
1. Polishing treatment of the sample: cutting a high-voltage electronic optical foil to be measured with the thickness of 125 mu m into 9 strips with the length of 10 x 3cm, removing oil stains, annealing for 3 hours at 500 ℃, flattening by using flat glass, and then putting into a muffle furnace for annealing for 6 hours at 500 ℃; absolute ethyl alcohol and azeotropic perchloric acid are added according to a volume ratio of 9: and (l) taking the mixed solution as electrolytic polishing solution, taking the annealed optical foil as an anode, taking a stainless steel plate as a cathode, carrying out electrolytic polishing on 2 x 3cm of the lower half part of the optical foil, wherein the polishing current is 2.32A, the polishing time is 0 (namely not polished), 1, 2, 5, 10, 15, 20, 25 and 30s respectively, cleaning and airing after polishing, obtaining optical foil strips with different thicknesses, and the polishing thickness results are shown in a table 4.
2. Preparation of a standard solution: 0.1g of low-lead aluminum foil was dissolved in 10mL of aqua regia, and the resulting solution was diluted with ultrapure water to obtain 500g of a solution. Taking a proper amount of 100ppb lead standard solution into a 50mLFEP bottle, and diluting the lead standard solution into standard solutions with lead contents of 0, 0.1, 0.2, 0.5 and 1ppb by using the low-lead aluminum foil solution.
The memory effect generated by the high-content standard solution can remain in the sample injection system of the instrument for a long time, so that the interference on the detection of a subsequent test sample is caused, and the lead content in the test sample is extremely low, so that the lead content range of the standard solution is correspondingly selected to be 0.1-1ppb with lower concentration.
3. Preparation of a test solution: cutting 0.02g of each polished part of the 9 optical foil strips in the step 1, placing the polished parts in a 100mL PFA beaker, adding 2mL of aqua regia, heating the mixture on an electric hot plate until the mixture is completely dissolved, cooling the mixture, and diluting the mixture to 100g by using ultrapure water to obtain a test solution prepared by polishing the optical foil strips with different thicknesses.
The main solute in the sample solution is aluminum trichloride converted from aluminum, and in order to meet the requirement of an instrument for the content of soluble substances in the sample solution (< 0.2%), 0.02g of sample is taken and diluted by 5000 times, so that the content of the soluble substances in the sample solution is 0.1%.
Because the aluminum foil is in a sheet shape, 0.02g of aluminum foil is too small in mass and inconvenient to sample, and a certain error exists in the actual sampling and weighing operation process, the sampling mass range is set to be 0.02 +/-10% g, and the mass range of a test sample solution obtained by diluting with ultrapure water is 100 +/-10% g. Actual sampling mass DnAnd quality of test solution EnSee table 4.
Experiments show that the effect of dissolving the aluminum foil by the aqua regia is best, a high-purity reagent (the content of Pb in nitric acid and hydrochloric acid used for preparing the aqua regia is lower than 0.01ppb) can be obtained, the blank of the reagent diluted according to the experimental scheme is less than 0.0002ppb and is lower than the detection limit of an instrument, and elements such as chlorine, nitrogen and the like introduced into the aqua regia cannot cause mass spectrum interference on the detection of the lead element due to the large mass number of the lead element. When the aqua regia is 2mL, the sample can be completely dissolved, and when the aqua regia is less, the sample cannot be dissolved, and in order to reduce the reagent blank, the acid is required to be used as little as possible, so that the acid adding amount is selected to be 2 mL. The purity of the electronic optical foil is more than 99.99%, and no insoluble substances exist when the electronic optical foil is dissolved by aqua regia. And the conventional microwave digestion needs a large amount of acid and multiple times of sample transfer, so that pollution is easily introduced.
The volumetric flask is not resistant to acid corrosion, and the sample is transferred for many times, so that pollution is easily caused, a PFA beaker is selected for quantification, and one-step dilution is adopted.
4. Igniting the instrument, after preheating, setting the instrument parameters as shown in table 1, sucking the standard solution with lead content of 1ppb in step 2, tuning the instrument without using recommended global sensitivity optimization, and manually changing the tuning monitoring quality into the standard solution208Pb and then208The sensitivity of Pb is adjusted to the maximum value, and the sensitivity of other elements is ignored; an internal standard sample tube is placed into the mixed internal standard solution and maintained throughout the testing process to correct system errors and monitor instrument status.
5. Standard solution linearity: absorbing the lead standard solutions with different contents in the step 2, and measuring by using ICP-MS to obtain a standard working curve of lead; the correlation coefficient is 0.9998, which shows that the linear relation of the standard curve is good.
Because the sample introduction pipeline is longer, the sample solution in the pipeline can reach the plasma only in 25s when the pump speed is normal, and the sampling pipe is cut to the shortest in order to shorten the sample introduction time and relieve the blockage of the sampling cone and the intercepting cone hole. In the test process, when the sample lifting time is 14s, the sample just reaches the plasma, so that the sample lifting time is 15s, the stable time is 20s, and the sample injection needle is taken out 20s before the reading is finished and put into the flushing solution.
6. The system applicability is as follows: and (3) measuring the sample solution prepared from the optical foil strip with the polishing time of 0 in the step (3) by using ICP-MS (inductively coupled plasma-mass spectrometry), wherein the recovery rate of the obtained internal standard is 98.2%, the system applicability is good, after 50 needles of sample solution are continuously fed, the recovery rate of the internal standard is 82.6%, the instrument state is stable, and the phenomenon of sensitivity reduction caused by sampling cone and intercepting cone blockage does not occur.
7. And (4) quantitative limit: 0.1g of low-lead aluminum foil was placed in a 500mLFEP bottle, 10mL of aqua regia was added to dissolve the foil, the solution was diluted with ultrapure water to 500g, an appropriate amount of 100ppb of a lead standard solution was placed in a 50mLFEP bottle, the lead standard solution was diluted with the above low-lead aluminum foil solution to solutions having lead contents of 0.001, 0.002, 0.005 and 0.01ppb, respectively, the lead contents thereof were measured by ICP-MS, and the normalized recovery rate of lead was calculated, and the results are shown in Table 2. Keeping the content of the recovery rate between 70 and 130 percent, and after removing abnormal values, selecting the lowest content which can be accurately quantified by the quantitative limit, wherein the quantitative limit of the obtained detection method is 0.002 ppb.
8. And (3) precision experiment: and (3) sampling the standard solution with the lead content of 0.1, 0.2 and 0.5ppb in the step (2) for three times, measuring the lead content by using ICP-MS, and calculating the relative standard deviation of the detection result to be 1.5%, 1.6% and 1.2% respectively, thereby indicating that the precision of the method is good.
9. And (3) repeatability experiment: taking the optical foil strip with the polishing time of 0, preparing 6 parts of parallel samples according to the step 3, measuring the lead content by ICP-MS, and calculating that the average value of the lead content is 0.241ppb, the relative standard deviation is 1.9%, thus the repeatability of the method is good.
10. The detection method comprises the following steps: taking 0.02g of optical foil strip with polishing time of 0, placing the optical foil strip in a 100mL PFA beaker, adding 2mL of aqua regia to prepare 9 parts of parallel samples, heating the samples on an electric hot plate until the samples are completely dissolved, cooling the samples, diluting the samples to 100g by using ultrapure water, measuring the lead content by using ICP-MS, and calculating an average recovery rate value, wherein the results are shown in Table 3 and are respectively 100.3%, 99.2% and 98.7%, which shows that the recovery rate of the detection method is good, and the detection result obtained by using the detection method is accurate.
11. The pretreatment method comprises the following steps: taking 9 parts of each 0.02g of optical foil strips with the polishing time of 0, placing the optical foil strips in a 100mL PFA beaker, respectively adding 100ppb of lead standard solutions of 0.1, 0.2, 0.3 and 0.3g, then adding 2mL of aqua regia, heating until the sample is completely dissolved, cooling, diluting with ultrapure water until the total mass of the solution is 100g, measuring the lead content by ICP-MS, and calculating the average recovery rate, wherein the results are shown in Table 3, are respectively 97.4%, 98.7% and 98.3%, and are consistent with the standard recovery rate of the detection method, which indicates that the recovery rate of the pretreatment mode of the determination method is good, and lead element loss is hardly caused in the pretreatment process.
12. Calculating the thickness A of the n-th optical foil strip after being polished according to the formula 1nThe results are shown in Table 4;
An＝10000*Tni M/(ρ F S2) formula 1
In formula 1:
rho-density of aluminum, unit 2.7g/cm3；
Tn-polishing time of the nth optical foil strip in units of s;
i-polishing current, in units of A;
m-the molar mass of aluminum, 27 g/mol;
s-polished area in cm2；
F-Faraday constant, 96485C/mol;
calculating the thickness A of the nth optical foil strip after being thrown according to the formula 2nThickness A polished away from the (n-1) th optical foil stripn-1Lead content omega betweennLead contents of different thicknesses are obtained, and the results are shown in a table 4;
ωn＝[(A-An-1*2)*En-1*Cn-1/Dn-1-(A-An*2)*En*Cn/Dn]/[(An-1-An)*2]formula 2
In the formula:
a-original thickness of the optical foil, with unit of μm;
An-1-the thickness of the (n-1) th optical foil strip, in μm, removed;
An-the thickness of the nth optical foil strip, in μm, removed;
Dn-1-the sample mass of the polished part of the (n-1) th optical foil strip, in g;
En-1the mass of a sample solution prepared by sampling the polished part of the (n-1) th optical foil strip is g;
Dn-the sample mass of the polished section of the nth optical foil strip in g;
Enthe mass of a sample solution prepared by sampling the polishing part of the nth optical foil strip is g;
Cn-1the lead content of a test solution prepared by sampling the polished part of the (n-1) th optical foil strip is g/g;
Cnthe lead content of a test solution prepared by sampling the polished part of the nth optical foil strip is g/g;
the high-voltage electronic optical foil strip is polished on five surfaces (a left side surface, a right side surface, a bottom surface, a front surface and a back surface) of the high-voltage electronic optical foil strip at the same time, and because the thickness of the optical foil is in a micron level, the areas of the left side surface, the right side surface and the bottom surface of the optical foil strip are too small relative to the front surface and the back surface, the result is not greatly influenced, and therefore the parts of the optical foil strip which are polished off are approximately considered to be positioned on the front surface and the back surface during calculation.
TABLE 2 quantitative limit experimental data
| Numbering | Normalized content (ppb) | Measured content (ppb) | Content of matrix (ppb) | Recovery rate | Whether or not to pass |
| 1 | 0.0010 | 0.0026 | 0.0020 | 63.2％ | Failed through |
| 2 | 0.0020 | 0.0037 | 0.0020 | 83.4％ | By passing |
| 3 | 0.0050 | 0.0073 | 0.0020 | 106.2％ | By passing |
| 4 | 0.0100 | 0.0116 | 0.0020 | 96.2％ | By passing |
TABLE 3 Experimental data for recovery with addition of standard
TABLE 4 calculation results of different thickness of Pb content in high-voltage electronic aluminum foil
| Numbering | Tn(s) | An(um) | Dn(g) | En(g) | Cn(ppb) | ωn(ppb) |
| 1 | 0 | 0 | 0.0215 | 100.0524 | 0.2611 | N/A |
| 2 | 1 | 0.2 | 0.0182 | 100.2912 | 0.1388 | 141230 |
| 3 | 2 | 0.4 | 0.0201 | 100.2321 | 0.1133 | 62794 |
| 4 | 5 | 1 | 0.0198 | 100.2989 | 0.0622 | 26160 |
| 5 | 10 | 2 | 0.0206 | 100.0234 | 0.0210 | 13186 |
| 6 | 15 | 3 | 0.0189 | 100.0142 | 0.0098 | 3073 |
| 7 | 20 | 4 | 0.0211 | 100.0561 | 0.0063 | 1337 |
| 8 | 25 | 5 | 0.0203 | 100.1237 | 0.0057 | 145 |
| 9 | 30 | 6 | 0.0196 | 100.1023 | 0.0049 | 141 |
As can be seen from the data in tables 2-4, the method for measuring the lead content of the high-voltage electronic optical foil with different thicknesses in the surface layer has the advantages of low quantitative limit, high precision, high repeatability and accurate result.
Claims (10)
1. A method for measuring the content of lead with different thicknesses on the surface layer of a high-voltage electronic optical foil is characterized by comprising the following steps:
1) and polishing the sample: cutting the high-voltage electronic optical foil to be measured into n strips with the same shape, performing electrolytic polishing after decontamination and annealing, keeping the polishing current and the polishing area unchanged, and sequentially increasing the polishing time to obtain the optical foil strips with different thicknesses removed; wherein the thickness A of the first optical foil strip is removed10, the thickness of the n-th optical foil strip is An，n≥2；
2) And preparing a standard solution: weighing 0.1g of low-lead aluminum foil with lead content less than 10ppb, dissolving the low-lead aluminum foil with aqua regia, and diluting the low-lead aluminum foil with ultrapure water to obtain 500g of solution; then, diluting 100ppb lead standard solution into standard solutions with lead contents of 0.1, 0.2, 0.5 and 1ppb respectively;
3) and preparing a test solution: cutting polished part D of the nth smooth foil strip in the step 1)ng, dissolving with aqua regia, and diluting with ultrapure water to obtain Eng, a test solution;
4) respectively taking the standard solution prepared in the step 2) and the test solution prepared in the step 3) for ICP-MS determination, quantifying by adopting a standard curve method, and introducing an internal standard for correction on line to obtain the content of lead in the test solution;
5) calculating the thickness A of the nth optical foil strip according to the formula 1n；
An=10000*TnI M/(ρ F S2) formula 1
In formula 1:
rho-density of aluminum, 2.7g/cm3；
Tn-polishing time of the nth optical foil strip in units of s;
i-polishing current, in units of A;
m-the molar mass of aluminum, 27 g/mol;
s-polished area in cm2；
F-Faraday constant, 96485C/mol;
calculating the thickness A of the nth optical foil strip according to the formula 2nThickness A polished away from the (n-1) th optical foil stripn-1Lead content omega betweenn；
ωn=[ (A-An-1*2)*En-1 *Cn-1/Dn-1 -(A-An*2) *En*Cn/ Dn]/[ (An-1-An)*2]Formula 2
In formula 2:
a-original thickness of the optical foil, with unit of μm;
An-1-the thickness of the (n-1) th optical foil strip, in μm, removed;
An-the thickness of the nth optical foil strip, in μm, removed;
Dn-1-the sample mass of the polished part of the (n-1) th optical foil strip, in g;
En-1the mass of a sample solution prepared by sampling the polished part of the (n-1) th optical foil strip is g;
Dn-the sample mass of the polished section of the nth optical foil strip in g;
Enthe mass of a sample solution prepared by sampling the polishing part of the nth optical foil strip is g;
Cn-1the lead content of a test solution prepared by sampling the polished part of the (n-1) th optical foil strip is g/g;
Cnand the lead content of the sample solution prepared by sampling the polished part of the nth optical foil strip is g/g.
2. The method for determining the lead content of different thicknesses of the surface layer of the high voltage electro-optical foil as claimed in claim 1, wherein the polishing current in step 1) is 0.1-10A and the polishing time is 1-60 s.
3. The method for determining the lead content of different thicknesses of the surface layer of the high-voltage electronic optical foil as claimed in claim 1, wherein D) in the step 3)n0.018-0.022g of aqua regia, 2mL of aqua regia and the mass E of the sample solutionnIs 90-110 g.
4. The method for measuring the lead content of different thicknesses of the surface layer of the high voltage electro-optical foil according to any one of claims 1 to 3, wherein the operating conditions of the ICP-MS measurement in the step 4) are as follows:
analysis mode: collision free reaction gas mode
Radio frequency power: 1500w plasma gas flow rate: 15L/min
Flow rate of carrier gas: 0.76L/min make-up gas flow rate: 0.36L/min
Temperature of the atomization chamber: 2 ℃ peristaltic pump speed: 0.1 rps
The stabilizing time is as follows: 20s sample lifting time: 15s
An acquisition mode: sampling depth of mass spectrogram: 6.0mm
Integration time: 1.2s number of points taken to determine peak pattern: 3
The repeated sampling times are as follows: 3 scan/repeat times: 10.
5. the method for measuring lead content of different thicknesses on the surface layer of a high voltage electro-optical foil as claimed in claim 4, wherein the ICP-MS measurement in the step 4) is carried out by sucking the standard solution with lead content of 1ppb in the step 2) before the test, tuning the instrument, and changing the quality of the tuning monitoring into the quality of the tuning monitoring208Pb, and will208The sensitivity for Pb is tuned to a maximum.
6. The method for determining the lead content of different thicknesses of the surface layer of the high voltage electro-optical foil as claimed in claim 1, wherein the method further comprises the steps of: dissolving a low-lead aluminum foil with the lead content of less than 10ppb by using aqua regia, and diluting by using ultrapure water to obtain 500g of solution; diluting 100ppb lead standard solution into solutions with lead content of 0.001, 0.002, 0.005 and 0.01ppb respectively by using the obtained solution, measuring the lead content by ICP-MS, and calculating the recovery rate of the added standard; and (4) determining that the recovery rate of the added standard is between 70 and 130 percent as the accurate quantification, and taking the lowest content which can be accurately quantified as the final quantification limit to obtain the quantification limit of the determination method.
7. The method for determining the lead content of different thicknesses of the surface layer of the high voltage electro-optical foil as claimed in claim 1, wherein the method further comprises the steps of: and (3) measuring the content of the lead in the standard solution prepared in the step 2) by ICP-MS, and repeating the measurement for three times to calculate the relative standard deviation of the measurement result.
8. The method for determining the lead content of different thicknesses of the surface layer of the high voltage electro-optical foil according to claim 1, further comprising the steps of: preparing 6 parts of parallel sample solution according to the preparation of the sample solution in the step 3), measuring the lead content of the sample solution by ICP-MS, and calculating the average value and the relative standard deviation of the lead content.
9. The method for determining the lead content of different thicknesses of the surface layer of the high voltage electro-optical foil as claimed in claim 3, wherein the method further comprises the steps of: cutting 0.02g of polished part of any one of the optical foil strips in the step 1), dissolving with 2mL of aqua regia, diluting to 100g with ultrapure water, preparing 9 parts of parallel sample solutions, respectively adding 0.1, 0.2, 0.3 and 0.3g of lead standard solution with the content of 100ppb, measuring the lead content by ICP-MS, and calculating to obtain the average additive recovery rate of the detection method.
10. The method for determining the lead content of different thicknesses of the surface layer of the high voltage electro-optical foil as claimed in claim 9, wherein the method further comprises the steps of: cutting 0.02g of polished part of any one of the optical foil strips in the step 1), preparing 9 parts in parallel, respectively adding 0.1, 0.2, 0.3 and 0.3g of lead standard solution with the content of 100ppb, dissolving the lead standard solution with 2mL of aqua regia, diluting the solution with ultrapure water until the mass of the solution is 100g, respectively measuring the lead content of the solution by ICP-MS, and calculating the average adding standard recovery rate of the pretreatment method.
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