Method for measuring arsenic content in wires, cables and materials by X-ray fluorescence spectrometry

Abstract

The invention belongs to the technical field of chemical element detection, and provides a method for measuring arsenic content in wires, cables and materials by X-ray fluorescence spectrometry. The method comprises the following steps: S1, performing pretreatment on a wire and cable sheath or an insulating layer to obtain a to-be-tested sample; s2, respectively obtaining a plurality of standard samples and corresponding arsenic element contents; s3, respectively carrying out X-ray fluorescence spectrum testing on the plurality of standard samples under set testing conditions to obtain fluorescence intensity of the plurality of standard samples; s4, obtaining a calibration curve according to the fluorescence intensity and the arsenic element content of the plurality of standard samples; s5, performing X-ray fluorescence spectrum testing on the to-be-tested sample under set testing conditions to obtain the fluorescence intensity of the to-be-tested sample; and S6, obtaining the arsenic element content in the to-be-tested sample according to the fluorescence intensity and the calibration curve of the to-be-tested sample. Therefore, the arsenic element content in wires, cables and materials can be accurately and quickly measured.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical element detection, and in particular relates to a method for determining the arsenic content in wires, cables and materials using an X-ray fluorescence spectrometry method. Background Art

[0002] As an important industrial product, wires and cables are widely used in industry, construction, transportation, energy and other fields. The rapid development of the industry has put forward new requirements for the improvement of the testing system of flame-retardant wire and cable products. Antimony trioxide (Sb2O3) is a very efficient flame retardant in wires and cables and materials such as flame-retardant polyvinyl chloride (PVC) and flame-retardant polyethylene (PE). Antimony trioxide is prepared from stibnite (Sb2O3) through multiple steps such as calcination oxidation, purification, reduction and reoxidation. Since antimony (Sb) and arsenic (As) are associated minerals, special care is required to remove arsenic impurities during the purification process. In order to reduce costs, some unscrupulous raw material manufacturers may omit or simplify the purification steps, resulting in a high arsenic content in the produced antimony trioxide. These arsenic-containing antimony trioxides are then added to wires and cables as flame retardants, resulting in arsenic in wires and cables. As a toxic element, arsenic may cause harm to human health and the environment if it exists in excessive amounts in wires and cables. When arsenic is contained in wires and cables, it may be gradually released into the environment during use, posing a potential threat to people's health. In addition, wires and cables containing arsenic will also produce toxic gases and smoke when burned, further exacerbating the harm to the environment and human body.

[0003] At present, there is no systematic method and relevant standards for determining the arsenic content in wires, cables and materials in China, so the establishment of corresponding test methods is of great significance for the formulation of relevant standards; the traditional methods for determining arsenic usually use atomic absorption spectrometry, chemical analysis, inductively coupled plasma atomic emission spectrometry (ICP-AES), etc. The traditional method of analyzing the arsenic content is complicated, the determination cycle is long, and a large amount of chemical reagents are consumed, resulting in high determination costs and easy environmental pollution risks, poor data repeatability, and poor precision; atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry (ICP-AES) have the disadvantages of long chemical pretreatment operation process, cumbersome analysis procedures, complex operations, and large human factors, which are difficult to meet the requirements of batch rapid analysis. Although X-ray fluorescence spectrometry is a relatively fast analysis method, the sample preparation process may still be complicated. For wire and cable samples, cutting, crushing, tableting, splicing and other processes are required to ensure the uniformity and surface flatness of the samples. If the sample is not prepared properly, it may lead to deviations in the analysis results.

[0004] At the same time, the quantitative analysis of X-ray fluorescence spectrometry usually requires the establishment of a calibration curve, but in practical applications, due to the diversity and complexity of wires and cables and materials, it may be difficult to establish an accurate calibration curve. At present, the method of determining the arsenic content in wires and cables by X-ray fluorescence spectrometry has not yet formed a unified standard and specification. Different researchers and laboratories may use different experimental test conditions, sample preparation methods and data processing methods in the determination process, resulting in inconsistency and poor comparability of the determination results; for example, Chinese patent CN 103808698 A discloses a method for determining the arsenic content in propylene, but the determination process is cumbersome; Chinese patent CN 115791856 A discloses a method for determining the uranium content in natural uranium products by X-ray fluorescence spectrometry, and Chinese patent CN 111896569 A discloses a method for determining the magnesium and sulfur content in magnesium sulfate and its hydrates by X-ray fluorescence spectrometry, but because the composition and properties of wires and cables and materials are completely different from natural uranium products and magnesium sulfate and its hydrates, and the determination of the arsenic content of wires and cables and materials requires different pretreatment steps and instrument conditions, the above two methods are not suitable for determining the arsenic content in wires and cables and materials. Therefore, it is of great significance to accurately and quickly determine the arsenic content in wires, cables and materials. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to accurately and quickly determine the arsenic content in wires, cables and materials.

[0006] The present invention is achieved through the following technical solutions: A method for determining the arsenic content in wires, cables and materials by X-ray fluorescence spectrometry, the method comprising the following steps: S1. Pre-treat the sheath or insulation layer of wires, cables and materials to obtain the sample to be tested; S2. Obtain a plurality of standard samples and their corresponding arsenic content respectively; S3, performing X-ray fluorescence spectrum tests on the multiple standard samples under set test conditions to obtain the fluorescence intensities of the multiple standard samples; S4, obtaining a calibration curve according to the fluorescence intensity and arsenic content of the plurality of standard samples; S5, performing an X-ray fluorescence spectrum test on the sample to be tested under the set test conditions to obtain the fluorescence intensity of the sample to be tested; S6. Obtaining the arsenic content in the sample to be tested according to the fluorescence intensity of the sample to be tested and the calibration curve.

[0007] The present invention reduces the measurement error caused by irregular samples by establishing a reasonable sample preparation method, and at the same time reduces the error caused by the matrix effect; the instrument measurement conditions are optimized and studied according to the sample properties and the structure and characteristics of the X-ray system of the arsenic element, thereby improving the test accuracy; The present invention establishes internal standard correction, improves quantitative results, increases the quantitative accuracy of irregular samples, establishes a calibration curve after internal standard correction, and improves the accuracy and precision of the calibration curve; further establishes a scattered line internal standard method, and significantly improves test accuracy and data reliability by selecting a Rayleigh scattering internal standard line.

[0008] Furthermore, the set test conditions include the following conditions: the atmosphere is air, the collimator is 10 mm, the analysis line is AsKβ, the primary filter is 4#, the voltage is 50 kV, the current is AUTO, and the measurement time is 100 s.

[0009] The reasons for selecting the analysis spectral lines of the present invention are as follows: a high-energy X-ray system and a spectrum line without interference are selected as the analysis line. In the actual test process, it is found that wires, cables and materials often contain Pb, and the energy position of PbLα is 10.55KeV, and AsKα is 10.53 KeV. Therefore, in order to avoid the overlapping interference of PbLα on AsKα, the AsKβ (11.73) line can be selected as the analysis line.

[0010] The reasons for selecting the primary filter of the present invention are as follows: the primary X-ray filter is located between the X-ray tube and the sample, and is a metal film that can selectively absorb a certain wavelength or waveband. The material used is a metal film that can strongly absorb X-ray radiation interference with a wavelength shorter than its absorption limit. The filter can absorb both the target line and the scattered line of the continuous spectrum, so it can be used to eliminate or weaken the interference caused by the characteristic spectrum line of the target material, the impurity line, the scattered background of the continuous spectrum, etc. that interfere with the analysis line. A metal sheet is inserted between the X-ray and the sample, and the metal sheet is used to selectively absorb the X-ray to reduce the characteristic target line, impurity line and background; improve the signal-to-noise ratio of the spectrum peak of the element to be measured and improve the analysis sensitivity. Filters of different materials have different effective ranges and corresponding elements. After inserting a suitable metal filter between the X-ray tube and the sample, the scattered X-rays that are useless for analysis can be reduced. This filter is called a primary filter. Taking EDX-GP as an example, a combination of 5 filters is configured. When the target element is arsenic As, the 4# (Cu) filter is selected according to the energy position of the arsenic element to reduce the continuous X-ray background.

[0011] Furthermore, the number of the plurality of standard samples is ≥5.

[0012] Furthermore, the arsenic contents of the plurality of standard samples are arranged in a gradient.

[0013] Furthermore, the calibration curve uses a Rayleigh scattering line internal standard method to correct the shape or reduce matrix effects and analytical errors.

[0014] The matrix effect includes absorption and enhancement effect between elements, and also includes the physical state of the sample such as particle size, surface effect, etc. The internal standard method of the present invention is to select the characteristic spectrum of a certain element or other spectrum lines very close to the analysis line as the internal standard line, and make a calibration curve with the intensity ratio of the analysis line and the internal standard line and the content of the analyzed element. The calibration curve expression is: W i = aR i +b In the formula, R i =I i / within, I i is the analytical line intensity, and I is the internal standard line intensity.

[0015] The internal standard method of the present invention has the following advantages: 1. It corrects the measurement error of the shape and thickness on the result, and at the same time reduces the analysis error caused by the matrix effect. 2. It can reduce the error caused by density for powder tablets and loose powder samples. 3. Since the analysis line and the internal standard line are very close and the background is roughly the same, the peak intensity ratio can be used directly without deducting the background.

[0016] The internal standard method of the present invention particularly relates to a scattered ray internal standard method: it refers to selecting the scattered rays generated by the primary X-ray emitted by the X-ray tube and scattered by the sample as the internal standard line. The generated scattered rays include: coherent scattered rays (Rayleigh scattered rays), incoherent scattered rays (Compton scattered rays) and scattered rays of continuous spectral lines of the characteristic spectrum of the target element.

[0017] Advantages: Since it uses existing spectral lines, it does not need to add internal standard elements. The operation procedure of adding internal standards is relatively cumbersome. The internal standard and the sample must be accurately measured each time the analysis is performed. Sometimes it is difficult to find a suitable internal standard. This method is applicable to samples in various states, including solids, and is easy to operate and time-saving. It can compensate for the surface state of the sample, particle size effect, and changes in pipe flow and pressure to a certain extent.

[0018] The internal standard method of the present invention is a scattered line internal standard method, which uses existing spectrum lines without adding additional internal standard elements, is suitable for wires and cables and material samples, and is convenient and time-saving to operate. In particular, it relates to a Rayleigh scattering internal standard line (coherent scattered line of the characteristic spectrum line of the target element), which improves the test accuracy by selecting the Rayleigh scattering internal standard line to correct the absorption effect of the matrix.

[0019] Furthermore, the calibration curve is: Y=1358.2186X-3.74387, and the linear correlation coefficient R2=0.9999.

[0020] When drawing the calibration curve of arsenic in the standard sample, the least square method is used to draw the calibration curve of arsenic in the standard sample, and its linear equation expression is y=ax+b, where a and b are linear equation coefficients. The calibration curve is drawn with the content of arsenic in the standard sample as the horizontal coordinate and the corresponding fluorescence intensity as the vertical coordinate.

[0021] Furthermore, the thickness of the plurality of standard samples and the samples to be tested are all 3-5 mm.

[0022] Furthermore, the sizes of the plurality of standard samples and the samples to be tested all cover the size range of the collimator used.

[0023] Furthermore, the pre-treatment includes the following methods: sheeting, bundling, stacking, wrapping and splicing.

[0024] Furthermore, the splicing method uses dichloromethane and / or epoxy resin.

[0025] Preparation process of multiple standard samples and test samples of the present invention: In fluorescent X-ray analysis, as the shape and thickness of the sample change, the intensity of the fluorescent X-ray obtained also changes. At this time, the results in the working curve of the proportional relationship between the content and the measured intensity are different. Therefore, in principle, it is generally necessary to process the unknown samples and standard samples in the working curve into the same thickness and shape in advance. That is, keep the shape, size, thickness and matrix consistency with the standard sample. However, if all are processed into the same thickness and shape as the standard sample, it will take a lot of time and cost.

[0026] Therefore, in order to achieve the requirements of rapid batch and accurate testing, the present invention proposes a special sample pre-treatment method for special samples such as wires and cables: wires and cables are composite samples, and the sample splitting principle refers to the IEC62321 standard to split them into homogeneous materials, and meet the thickness requirements of 3-5mm, as flat as possible, and the samples cover the size range of the collimator used as much as possible. The finished cable samples are split into three sub-samples: insulation layer, sheath, and conductor. When splitting, pay attention to avoid printed marks such as ink and paint on the samples to ensure that each sub-sample is a single homogeneous split unit. Prevent sweat contamination and other contamination during the splitting process to ensure the cleanliness of the samples. The cable sheath is cut into blocks according to its shape and size. When the sheath is thin, multiple samples can be cut and stacked to make it thicker than the test requirement of 3-5mm, and then both ends are fixed and pressed with a stapler or other means. The cable insulation samples are divided into tubes of uniform length, which are compacted and fixed with adhesive tape in a side-by-side manner to ensure that the test window is fully covered. For soft wires, when the above sample preparation method cannot be used, they can be rolled and wrapped, rolled / tightened to a diameter greater than 10mm, and wrapped with adhesive tape. Plastic particles and tiny samples are placed in special sample cups to 2 / 3 of the height of the sample cup. Be sure to avoid small samples falling into the test hole. Chemical reagents can be used for splicing. Dichloromethane has a good dissolving and bonding effect on polyvinyl chloride (PVC) and polyethylene (PE) plastics. It is used to dissolve the surface of the sample to be bonded and fit tightly under the action of external force. After the solvent evaporates, the solute fills the gap in the joint; epoxy resin is used for harder wire and cable samples. Epoxy resin has high bonding strength and good stability; these reagents are safer when used correctly and can effectively bond plastic materials. When selecting chemical reagents for sample splicing, factors such as sample structure, splicing requirements, and safety need to be considered. The present invention does not impose mandatory requirements on specific parameters such as the amount of chemical reagents, pressure, and dissolution time during the splicing process. The operator can make appropriate adjustments according to the sample effect, as long as the analysis requirements of the X-ray fluorescence instrument can be met and the operation steps are simple and quick. Due to the irregularity of wires, cables and material products, if direct measurement is performed, it is easy to generate scattered X-rays, which will lead to changes in the intensity of X-ray fluorescence. The interference of scattered rays and the error caused by the surface effect of the sample are reduced through a reasonable sample preparation method, thereby increasing the reliability of the test data.

[0027] The beneficial effects of the present invention are: BRIEF DESCRIPTION OF THE DRAWINGS In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 A calibration curve diagram of multiple standard samples provided in the embodiments of the present application; Figure 2 for Figure 1 A partial enlarged view of . DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0030] This embodiment provides a method for determining the arsenic content in wires, cables and materials using X-ray fluorescence spectrometry, the method comprising the following steps: Step 1: The energy dispersive X-ray fluorescence analyzer used in this embodiment is EDX-GP, manufactured by Shimadzu Corporation. Determine the measurement conditions of the instrument, wires, cables and materials for arsenic, including spectral lines, primary filters, voltage, current and measurement time, as shown in Table 1: Table 1 X-ray fluorescence spectrometry conditions

[0031] Step 2: Select 5 PVC standard blocks with different known contents (chemical determination) as calibration samples and number them 1#, 2#…5# in sequence. Use ED-XRF method to measure the intensity of standard samples in sequence. Use the content of arsenic in the standard substance as the horizontal coordinate and the corresponding fluorescence intensity as the vertical coordinate to draw a standard curve and find the function of content and X-ray intensity. At this time, the internal standard method is used in the working curve to correct the influence of shape and thickness on the quantitative results. The working curve of the method is Y=1358.2186X-3.74387, and the linear correlation coefficient R 2 =0.9999, the intensity ratio and content form a good linear relationship, which meets the measurement requirements of the sample to be tested for the calibration curve.

[0032] Step 3: The sample wire and cable model 60227 IEC 01 (BV) is made into a tubular sample according to the specified sample preparation requirements, and is pressed and fixed with adhesive tape by side-by-side splicing. The sample is made of PVC material, and dichloromethane is used for splicing to dissolve the plastic surface to be bonded, and tightly fit under the action of external force. After the solvent evaporates, the solute fills the gap in the joint, and the sample completely covers the test window and is tested. The content of the sample to be tested is calculated using the working curve established by this method.

[0033] In order to verify the precision and accuracy of the analytical method established by the present invention, a precision and accuracy test was performed.

[0034] 1.1 Precision test 1: Take a wire and cable and its material sample, ensure that the sample is uniform, use the same sample preparation method to prepare 7 samples from different positions, and use X-ray fluorescence spectrometry to determine the arsenic content in the samples. The results are shown in Table 2 and Table 3: Table 2 Arsenic content of 7 samples in precision test 1

[0035] Table 3 Precision results of 7 samples in precision test 1

[0036] 1.2 Precision test 2: Take a sample of wire and cable and its materials, ensure that the sample is uniform, prepare a sample, and use X-ray fluorescence spectrometry to parallel measure the arsenic content in the sample 7 times. The measurement results are shown in Table 4: Table 4 Results of arsenic content in 7 parallel determinations of samples

[0037] It can be seen from Table 3 and Table 4 that the standard deviation and relative standard deviation obtained from the two precision tests are both low and within a reasonable range, and the analytical method established by the present invention has high precision.

[0038] 2. Accuracy test: The present invention selects 6 samples to be tested of the same material, which are numbered JS1, JS2...JS6 in sequence, and uses this method and the chemical method to measure the arsenic content in the samples respectively. The comparison of the results of the two methods for measuring the arsenic content is shown in Table 5.

[0039] Table 5 Determination results of arsenic content in samples of the same material

[0040] It can be seen that the present invention reduces the measurement error caused by irregular samples by establishing a reasonable sample preparation method; optimizes the instrument measurement conditions according to the sample properties and the structure and characteristics of the X-ray system of arsenic elements, thereby improving the test accuracy; at the same time, establishes an internal standard correction, improves the quantitative result, and improves the quantitative accuracy of irregular samples, and establishes a calibration curve after the internal standard correction, thereby improving the accuracy and precision of the calibration curve; further establishes a scattered line internal standard method, and significantly improves the test accuracy and data reliability by selecting the Rayleigh scattering internal standard line.

[0041] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. 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 arsenic content in wires, cables and materials by X-ray fluorescence spectrometry, characterized in that: The method comprises the following steps: S1. Pre-treat the sheath or insulation layer of wires, cables and materials to obtain the sample to be tested; S2. Obtain a plurality of standard samples and their corresponding arsenic content respectively; S3, performing X-ray fluorescence spectrum tests on the multiple standard samples under set test conditions to obtain the fluorescence intensities of the multiple standard samples; S4, obtaining a calibration curve according to the fluorescence intensity and arsenic content of the plurality of standard samples; S5, performing an X-ray fluorescence spectrum test on the sample to be tested under the set test conditions to obtain the fluorescence intensity of the sample to be tested; S6. Obtaining the arsenic content in the sample to be tested according to the fluorescence intensity of the sample to be tested and the calibration curve.

2. The method for determining the arsenic content in wires, cables and materials by X-ray fluorescence spectrometry according to claim 1, characterized in that: The set test conditions include the following conditions: the atmosphere is air, the collimator is 10 mm, the analysis line is AsKβ, the primary filter is 4#, the voltage is 50 kV, the current is AUTO, and the measurement time is 100 s.

3. The method for determining the arsenic content in wires, cables and materials by X-ray fluorescence spectrometry according to claim 1, characterized in that: The number of the plurality of standard samples is ≥5.

4. The method for determining the arsenic content in wires, cables and materials by X-ray fluorescence spectrometry according to claim 3, characterized in that: The arsenic content of the plurality of standard samples is arranged in a gradient.

5. The method for determining the arsenic content in wires, cables and materials by X-ray fluorescence spectrometry according to claim 1, characterized in that: The calibration curve uses the Rayleigh scattering line internal standard method to correct the shape or reduce the matrix effect and analytical error.

6. The method for determining the arsenic content in wires, cables and materials by X-ray fluorescence spectrometry according to claim 5, characterized in that: The calibration curve is: Y=1358.2186X-3.74387, linear correlation coefficient R 2 =0.9999.

7. The method for determining the arsenic content in wires, cables and materials by X-ray fluorescence spectrometry according to claim 1, characterized in that: The thickness of the plurality of standard samples and the samples to be tested are all 3-5 mm.

8. The method for determining the arsenic content in wires, cables and materials by X-ray fluorescence spectrometry according to claim 7, characterized in that: The sizes of the plurality of standard samples and the samples to be tested all cover the size range of the collimator used.

9. The method for determining the arsenic content in wires, cables and materials by X-ray fluorescence spectrometry according to claim 1, characterized in that: The pre-treatment includes the following methods: sheeting, bundling, stacking, rolling and splicing.

10. The method for determining the arsenic content in wires, cables and materials by X-ray fluorescence spectrometry according to claim 9, characterized in that: The splicing method uses dichloromethane and / or epoxy resin.

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