A method for determining heavy metal elements in polymers and its application

Abstract

The present invention provides a method for determining heavy metal elements in polymers and its application, which relates to the field of heavy metal detection. Specifically, ultraviolet light is first used to decompose the polymer sample, and then a microwave digestion instrument is used to completely digest the polymer sample. HNO 3 +H 2 O 2 +HClO 4 +HF acid digestion system is used to detect heavy metal elements lead, cadmium and mercury in plastics or polymer materials in electronic and electrical products and materials, further improving the rapid detection method of heavy metal element content in plastics and other polymers. The present invention solves the problem of incomplete digestion of many plastics, and at the same time solves the problem that some fillers in plastics cannot be digested, reduces the subsequent processing process, achieves the purpose of rapid and efficient, and further improves the method of rapid analysis of heavy metal content in plastics.

Description

Technical Field

[0001] The present application relates to the field of heavy metal detection, and more specifically, to a method for determining heavy metal elements in a polymer and its application. Background Art

[0002] Polymers may be contaminated by heavy metals in the environment during production, use or disposal. Determining the content of heavy metal elements in polymers helps to take appropriate measures to reduce their content and ensure the quality and safety of polymers. This is essential for protecting human health and the environment.

[0003] Microwave sealed digestion is a sample pretreatment technology used to dissolve and decompose organic and inorganic substances in solid samples. It uses microwave radiation energy to heat samples and digestion reagents in a sealed container to speed up the reaction and facilitate subsequent chemical analysis and monitoring. Microwave sealed digestion is also a common technique for pretreatment of polymers for the determination of heavy metal elements in polymers.

[0004] Microwave closed digestion Since the sample digestion process is carried out in a closed environment, only one pretreatment is needed to simultaneously determine the content of Pb, Cd and Hg, which is highly efficient. For some plastics containing Si, Zr, etc., the content analysis of Pb, Cd and Hg can also be achieved by adding HF acid, and there is no need to worry about the volatilization loss of the elements to be measured. However, there are still a small number of samples that cannot be completely digested by microwave closed digestion, resulting in low measurement results.

[0005] Conventional acid digestion system HNO3+H2O2 can obtain better measurement results for plastics such as PE and PP by using digestion pretreatment method. However, it is difficult to achieve for some plastics such as ABS and PBT. For example, the existing technology uses HNO3+H2O2+HClO4 to dissolve samples, which can better process ABS samples, but this method has certain problems in processing some plastics containing fillers such as silicates and TiO2; using HNO3+H2SO4, most plastic samples can be digested, including ABS and other plastic samples, but this method produces PbSO4 precipitation, resulting in low results, and does not solve the digestion problem of fillers in plastics.

[0006] In summary, it is necessary to propose a new microwave digestion method for the determination of heavy metal elements in polymer plastics. Summary of the invention

[0007] In order to provide a universal method for rapid microwave digestion of polymer samples, the present application provides a method for determining heavy metal elements in polymers and its application.

[0008] The present application provides a method for determining heavy metal elements in polymers using the following technical solution:

[0009] A method for determining heavy metal elements in a polymer, characterized in that it comprises the following steps: pre-treating a polymer sample, then placing the pre-treated polymer sample in a microwave digestion tank, adding an acidic digestion mixture, performing microwave digestion treatment according to a microwave digestion procedure, then transferring the sample to a fixed volume, and detecting the sample using an inductively coupled plasma atomic emission spectrometer;

[0010] The pre-processing comprises the following steps:

[0011] (1) crushing the polymer sample, wherein the average particle size of the crushed polymer sample is 20-80 μm;

[0012] (2) The crushed polymer sample is exposed to short-wave ultraviolet light for 2-15 hours at a UV dose of 10000-22000 mJ / cm 2 .

[0013] The method of the present application increases the surface area of ​​the sample by crushing the polymer sample to a fineness of 20-80 μm, allowing the digestion reagent to more easily contact the interior of the sample, thereby improving the efficiency and uniformity of the digestion. High-energy, high-frequency irradiation with short-wave ultraviolet light can help break the chemical bonds of the polymer and promote the digestion of the sample. In addition, ultraviolet light irradiation may also help decompose some organic substances that may interfere with the determination of heavy metals. By optimizing the irradiation time (2-15h) and ultraviolet light dose (10000-22000mJ / cm 2 ), which can effectively digest the sample while minimizing possible damage or changes to the sample. The pretreatment method helps to digest the polymer sample more quickly and completely, allowing the heavy metal elements to be released more fully, improving the sensitivity and accuracy of the detection. Through the pretreatment step, the content of organic matter and other interfering substances in the sample may be reduced, reducing the interference with the heavy metal determination and improving the reliability of the analysis results. The pretreated sample is easier to digest and analyze, which helps to improve the detection ability of the inductively coupled plasma atomic emission spectrometer for heavy metal elements and can more accurately determine the heavy metal content in the sample.

[0014] Optionally, the acidic digestion mixture specifically consists of HNO3, H2O2, HClO4 and HF.

[0015] Optionally, the sample mass is 0.19-0.21 g; the volume ratio of HNO3, H2O2, HClO4 and HF in the acidic digestion mixture is 7:0.2:1:0.5.

[0016] By adopting the above technical scheme, most plastics can be digested by the HNO3+H2O2 system, but some plastics such as PBT still cannot be digested, and the digestion problem of plastic fillers (such as glass fiber or TiO2) cannot be solved. The acid digestion method of HNO3+HBF4+H2O2 can partially solve the digestion problem of fillers in plastics. However, the introduction of HClO4 can help the digestion of plastics, and the introduction of HF can better solve the digestion problem of fillers. However, the further introduction of HCl is not obvious in most cases for the improvement of the final digestion effect, but it is easy to cause the pressure relief of the digestion tank. Therefore, the present invention selects the acid digestion system of HNO3+H2O2+HClO4+HF.

[0017] The amount of acid in the whole system is generally required to be no less than 6mL but no more than 10mL, otherwise the sample will not be digested clearly or pressure will be released during the microwave digestion process. The boiling point of 65% HNO3 is higher than that of water, and the higher boiling point is conducive to the digestion of plastic samples. Therefore, HNO3 should be used instead of water in the acid digestion system as much as possible.

[0018] Under the same conditions, 0.5mL, 1.0mL, and 1.5mL HClO4 were added to digest ABS. The experiment found that as the amount of HClO4 increased, the residue left after ABS digestion became less and less until it was completely digested. However, too high an amount of HClO4 can easily lead to excessive pressure in the digestion tank. Therefore, for safety reasons, the amount of HClO4 should not exceed 20% of the total acid digestion volume.

[0019] The amount of H2O2 used is not very helpful for ABS, which is difficult to digest. However, for PE, the addition of H2O2 helps digestion, but the effect is not much different. Excessive H2O2 dosage can easily lead to excessive pressure in the digestion tank.

[0020] Since glass fiber is often added to plastics as filler, HBF4 or HF is often added. Under the same conditions, HF digestion effect is better than HBF4. The less HBF4 or HF is used, the less damage to the instrument, but too little can not meet the requirements of complete digestion.

[0021] Optionally, the microwave digestion procedure specifically comprises the following steps:

[0022] S1, set the initial temperature to room temperature, gradually increase the temperature to 165℃, and the heating time is 10min;

[0023] S2, the initial temperature is 165℃, and the constant temperature is maintained for 5 minutes;

[0024] S3, the initial temperature is 165℃, gradually increase the temperature to 205℃, and the heating time is 9min;

[0025] S4, the initial temperature is 205℃, and the constant temperature is maintained for 40 minutes.

[0026] Temperature is the most important factor affecting the digestion effect. 205℃ is significantly better than 190℃. Higher temperature will be more conducive to the digestion of samples, but it is also easy to cause the digestion tank to release pressure and lead to sample loss. The pressure release phenomenon is more likely to occur under the condition of 210℃. Therefore, the digestion temperature is selected as 205℃.

[0027] The constant temperature time is also one of the factors that affect the digestion effect. When the ABS samples were digested at 205°C, the samples were digested more completely as the time went by, and the ABS samples generally required more than 40 minutes.

[0028] Optionally, the detection parameter settings are specifically as follows: RF power 1250W, cooling gas flow 15L / min, auxiliary gas flow 2.25L / min, carrier gas flow 0.7L / min.

[0029] Another object of the present invention is to provide an application of a method for determining heavy metal elements in polymers, which can be specifically used to detect heavy metal elements lead, cadmium and mercury in plastics or polymer materials in electronic and electrical products and materials.

[0030] The analytical spectral lines of heavy metal elements in the above method are set as: Pb 220nm or 182nm; Cd 214nm; Hg 194nm.

[0031] By adopting the above technical scheme and selecting specific analytical spectral lines, such as 220nm or 182nm for Pb, 214nm for Cd and 194nm for Hg, heavy metal elements such as lead, cadmium and mercury in plastic or polymer materials in electronic and electrical products and materials can be detected in a targeted manner. This specific detection helps to improve the accuracy and reliability of the analysis. The method can be applied to the detection of plastic or polymer materials in electronic and electrical products and materials, covering a wide range of application areas. This makes the method of great significance in ensuring product quality safety, environmental monitoring and compliance. In summary, the advantages of the above scheme include specificity, wide applicability, high sensitivity, accuracy and reliability, and high efficiency. These advantages make the method of practical application value and significance in the detection of heavy metal elements in electronic and electrical products and materials.

[0032] In summary, this application has the following beneficial effects:

[0033] 1. The method of the present application increases the surface area of ​​the sample by crushing the polymer sample to a fineness of 20-80 μm, allowing the digestion reagent to more easily contact the interior of the sample, thereby improving the efficiency and uniformity of the digestion. High-energy, high-frequency irradiation with short-wave ultraviolet light can help break the chemical bonds of the polymer and promote the digestion of the sample. In addition, ultraviolet light irradiation may also help decompose some organic substances that may interfere with the determination of heavy metals. By optimizing the irradiation time (2-15h) and ultraviolet light dose (10000-22000mJ / cm 2 ), which can effectively digest the sample while minimizing possible damage or changes to the sample. The pretreatment method helps to digest the polymer sample more quickly and completely, allowing the heavy metal elements to be released more fully, improving the sensitivity and accuracy of the detection. Through the pretreatment step, the content of organic matter and other interfering substances in the sample may be reduced, reducing the interference with the heavy metal determination and improving the reliability of the analysis results. The pretreated sample is easier to digest and analyze, which helps to improve the detection ability of the inductively coupled plasma atomic emission spectrometer for heavy metal elements and can more accurately determine the heavy metal content in the sample.

[0034] 2. The present invention adopts a microwave digestion instrument to completely digest the polymer sample, and proposes an acid digestion system of HNO3+H2O2+HClO4+HF, which is used to detect heavy metal elements lead, cadmium and mercury in plastics or polymer materials in electronic and electrical products and materials, further improving the rapid detection method of heavy metal element content in plastics and other polymers.

[0035] 3. The method of the present application solves the problem of incomplete digestion of many plastics, and at the same time solves the problem that some fillers in plastics cannot be digested, reduces the subsequent processing process, achieves the purpose of rapid and efficient, and further improves the method of rapid analysis of heavy metal content in plastics. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The invention is further described using the accompanying drawings, but the embodiments in the accompanying drawings do not constitute any limitation to the invention. A person skilled in the art can obtain other drawings based on the following drawings without creative work.

[0037] Figure 1 This is the spectral interference of Pb at 220nm.

[0038] Figure 2 This is the spectral interference of Pb at 182nm. DETAILED DESCRIPTION

[0039] The present application is further described in detail below with reference to the embodiments.

[0040] Example

[0041] Example 1

[0042] The method for determining heavy metal elements in polymers specifically comprises the following steps:

[0043] First, pre-treat the PVC sample as follows:

[0044] (1) crushing the polymer sample, wherein the average particle size of the crushed polymer sample is 20 μm;

[0045] (2) The crushed polymer sample was exposed to short-wave ultraviolet light for 2 h at a UV dose of 10,000 mJ / cm 2 .

[0046] Then weigh 0.20 g of the pretreated PVC sample, place it in a microwave digestion tank, add 7.0 mL of concentrated HNO3, 0.2 mL of H2O2, 1.0 mL of HClO4 and 0.5 mL of HF, perform microwave digestion according to the microwave digestion procedure, and then transfer it to a fixed volume of 25 mL.

[0047] The microwave digestion procedure is as follows:

[0048] program Initial temperature / ℃ End point temperature / ℃ Time / min 1 Room temperature 165 10 2 165 165 5 3 165 205 9 4 205 205 40

[0049] Next, an inductively coupled plasma atomic emission spectrometer, a cyclonic nebulizer, and a Meinhand type concentric nebulizer were used for detection, and the instrument parameters were set as follows: RF power 1250 W, cooling gas flow rate 15 L / min, auxiliary gas flow rate 2.25 L / min, and carrier gas flow rate 0.7 L / min.

[0050] Example 2

[0051] The method for determining heavy metal elements in polymers specifically comprises the following steps:

[0052] First, pre-treat the PC sample as follows:

[0053] (1) crushing the polymer sample, wherein the average particle size of the crushed polymer sample is 50 μm;

[0054] (2) The crushed polymer sample was exposed to short-wave ultraviolet light for 8 h at a UV dose of 18000 mJ / cm 2 .

[0055] Then weigh 0.19 g of the pretreated PC sample, place it in a microwave digestion tank, add 7.0 mL of concentrated HNO3, 0.2 mL of H2O2, 1.0 mL of HClO4 and 0.5 mL of HF, perform microwave digestion according to the microwave digestion procedure, and then transfer it to a fixed volume of 25 mL.

[0056] The microwave digestion procedure is as follows:

[0057] program Initial temperature / ℃ End point temperature / ℃ Time / min 1 Room temperature 165 10 2 165 165 5 3 165 205 9 4 205 205 40

[0058] Next, an inductively coupled plasma atomic emission spectrometer, a cyclonic nebulizer, and a Meinhand type concentric nebulizer were used for detection, and the instrument parameters were set as follows: RF power 1250 W, cooling gas flow rate 15 L / min, auxiliary gas flow rate 2.25 L / min, and carrier gas flow rate 0.7 L / min.

[0059] Example 3

[0060] The method for determining heavy metal elements in polymers specifically comprises the following steps:

[0061] First, pre-treat the PE sample as follows:

[0062] (1) crushing the polymer sample, wherein the average particle size of the crushed polymer sample is 80 μm;

[0063] (2) The crushed polymer sample was exposed to short-wave ultraviolet light for 15 h at a UV dose of 22000 mJ / cm 2 .

[0064] Then weigh 0.21 g of the pretreated PE sample, place it in a microwave digestion tank, add 7.0 mL of concentrated HNO3, 0.2 mL of H2O2, 1.0 mL of HClO4 and 0.5 mL of HF, perform microwave digestion according to the microwave digestion procedure, and then transfer it to a fixed volume of 25 mL.

[0065] The microwave digestion procedure is as follows:

[0066] program Initial temperature / ℃ End point temperature / ℃ Time / min 1 Room temperature 165 10 2 165 165 5 3 165 205 9 4 205 205 40

[0067] Next, an inductively coupled plasma atomic emission spectrometer, a cyclonic nebulizer, and a Meinhand type concentric nebulizer were used for detection, and the instrument parameters were set as follows: RF power 1250 W, cooling gas flow rate 15 L / min, auxiliary gas flow rate 2.25 L / min, and carrier gas flow rate 0.7 L / min.

[0068] Example 4

[0069] The method for determining heavy metal elements in polymers specifically comprises the following steps:

[0070] First, pre-treat the PP sample as follows:

[0071] (1) crushing the polymer sample, wherein the average particle size of the crushed polymer sample is 20 μm;

[0072] (2) The crushed polymer sample was exposed to short-wave ultraviolet light for 2 h at a UV dose of 10,000 mJ / cm 2 .

[0073] Then weigh 0.20 g of the pretreated PP sample, place it in a microwave digestion tank, add 7.0 mL of concentrated HNO3, 0.2 mL of H2O2, 1.0 mL of HClO4 and 0.5 mL of HF, perform microwave digestion according to the microwave digestion procedure, and then transfer it to a fixed volume of 25 mL.

[0074] The microwave digestion procedure is as follows:

[0075]

[0076]

[0077] Next, an inductively coupled plasma atomic emission spectrometer, a cyclonic nebulizer, and a Meinhand type concentric nebulizer were used for detection, and the instrument parameters were set as follows: RF power 1250 W, cooling gas flow rate 15 L / min, auxiliary gas flow rate 2.25 L / min, and carrier gas flow rate 0.7 L / min.

[0078] Example 5

[0079] The method for determining heavy metal elements in polymers specifically comprises the following steps:

[0080] First, pre-treat the ABS sample in the following steps:

[0081] (1) crushing the polymer sample, wherein the average particle size of the crushed polymer sample is 20 μm;

[0082] (2) The crushed polymer sample was exposed to short-wave ultraviolet light for 2 h at a UV dose of 10,000 mJ / cm 2 .

[0083] Then weigh 0.20 g of the pretreated ABS sample, place it in a microwave digestion tank, add 7.0 mL of concentrated HNO3, 0.2 mL of H2O2, 1.0 mL of HClO4 and 0.5 mL of HF, perform microwave digestion according to the microwave digestion procedure, and then transfer it to a fixed volume of 25 mL.

[0084] The microwave digestion procedure is as follows:

[0085] program Initial temperature / ℃ End point temperature / ℃ Time / min 1 Room temperature 165 10 2 165 165 5 3 165 205 9 4 205 205 40

[0086] Next, an inductively coupled plasma atomic emission spectrometer, a cyclonic nebulizer, and a Meinhand type concentric nebulizer were used for detection, and the instrument parameters were set as follows: RF power 1250 W, cooling gas flow rate 15 L / min, auxiliary gas flow rate 2.25 L / min, and carrier gas flow rate 0.7 L / min.

[0087] Example 6

[0088] The method for determining heavy metal elements in polymers specifically comprises the following steps:

[0089] First, pre-treat the silica gel sample as follows:

[0090] (1) crushing the polymer sample, wherein the average particle size of the crushed polymer sample is 20 μm;

[0091] (2) The crushed polymer sample was exposed to short-wave ultraviolet light for 2 h at a UV dose of 10,000 mJ / cm 2 .

[0092] Then weigh 0.20 g of the pretreated silica gel sample, place it in a microwave digestion tank, add 7.0 mL of concentrated HNO3, 0.2 mL of H2O2, 1.0 mL of HClO4 and 0.5 mL of HF, perform microwave digestion according to the microwave digestion procedure, and then transfer it to a fixed volume of 25 mL.

[0093] The microwave digestion procedure is as follows:

[0094] program Initial temperature / ℃ End point temperature / ℃ Time / min 1 Room temperature 165 10 2 165 165 5 3 165 205 9 4 205 205 40

[0095] Next, an inductively coupled plasma atomic emission spectrometer, a cyclonic nebulizer, and a Meinhand type concentric nebulizer were used for detection, and the instrument parameters were set as follows: RF power 1250 W, cooling gas flow rate 15 L / min, auxiliary gas flow rate 2.25 L / min, and carrier gas flow rate 0.7 L / min.

[0096] Example 7

[0097] The method for determining heavy metal elements in polymers specifically comprises the following steps:

[0098] First, pre-treat the phenolic plastic sample as follows:

[0099] (1) crushing the polymer sample, wherein the average particle size of the crushed polymer sample is 20 μm;

[0100] (2) The crushed polymer sample was exposed to short-wave ultraviolet light for 2 h at a UV dose of 10,000 mJ / cm 2 .

[0101] Then weigh 0.20 g of the pretreated phenolic plastic sample, place it in a microwave digestion tank, add 7.0 mL of concentrated HNO3, 0.2 mL of H2O2, 1.0 mL of HClO4 and 0.5 mL of HF, perform microwave digestion according to the microwave digestion procedure, and then transfer it to a fixed volume of 25 mL.

[0102] The microwave digestion procedure is as follows:

[0103] program Initial temperature / ℃ End point temperature / ℃ Time / min 1 Room temperature 165 10 2 165 165 5 3 165 205 9 4 205 205 40

[0104] Next, an inductively coupled plasma atomic emission spectrometer, a cyclonic nebulizer, and a Meinhand type concentric nebulizer were used for detection, and the instrument parameters were set as follows: RF power 1250 W, cooling gas flow rate 15 L / min, auxiliary gas flow rate 2.25 L / min, and carrier gas flow rate 0.7 L / min.

[0105] Example 8

[0106] The method for determining heavy metal elements in polymers specifically comprises the following steps:

[0107] First, the PA samples were pretreated as follows:

[0108] (1) crushing the polymer sample, wherein the average particle size of the crushed polymer sample is 20 μm;

[0109] (2) The crushed polymer sample was exposed to short-wave ultraviolet light for 2 h at a UV dose of 10,000 mJ / cm 2 .

[0110] Then weigh 0.20 g of the pretreated PA sample, place it in a microwave digestion tank, add 7.0 mL of concentrated HNO3, 0.2 mL of H2O2, 1.0 mL of HClO4 and 0.5 mL of HF, perform microwave digestion according to the microwave digestion procedure, and then transfer it to a fixed volume of 25 mL.

[0111] The microwave digestion procedure is as follows:

[0112] program Initial temperature / ℃ End point temperature / ℃ Time / min 1 Room temperature 165 10 2 165 165 5 3 165 205 9 4 205 205 40

[0113] Next, an inductively coupled plasma atomic emission spectrometer, a cyclonic nebulizer, and a Meinhand type concentric nebulizer were used for detection, and the instrument parameters were set as follows: RF power 1250 W, cooling gas flow rate 15 L / min, auxiliary gas flow rate 2.25 L / min, and carrier gas flow rate 0.7 L / min.

[0114] Example 9

[0115] The method for determining heavy metal elements in polymers specifically comprises the following steps:

[0116] First, pre-treat the PC+ABS sample as follows:

[0117] (1) crushing the polymer sample, wherein the average particle size of the crushed polymer sample is 20 μm;

[0118] (2) The crushed polymer sample was exposed to short-wave ultraviolet light for 2 h at a UV dose of 10,000 mJ / cm 2 .

[0119] Then weigh 0.20 g of the pretreated PC+ABS sample, place it in a microwave digestion tank, add 7.0 mL of concentrated HNO3, 0.2 mL of H2O2, 1.0 mL of HClO4 and 0.5 mL of HF, perform microwave digestion according to the microwave digestion procedure, and then transfer it to a fixed volume of 25 mL.

[0120] Example 10

[0121] The method for determining heavy metal elements in polymers specifically comprises the following steps:

[0122] First, pre-treat the PBT sample as follows:

[0123] (1) crushing the polymer sample, wherein the average particle size of the crushed polymer sample is 20 μm;

[0124] (2) The crushed polymer sample was exposed to short-wave ultraviolet light for 2 h at a UV dose of 10,000 mJ / cm 2 .

[0125] Then weigh 0.20 g of the pretreated PBT sample, place it in a microwave digestion tank, add 7.0 mL of concentrated HNO3, 0.2 mL of H2O2, 1.0 mL of HClO4 and 0.5 mL of HF, perform microwave digestion according to the microwave digestion procedure, and then transfer it to a fixed volume of 25 mL.

[0126] The microwave digestion procedure is as follows:

[0127] program Initial temperature / ℃ End point temperature / ℃ Time / min 1 Room temperature 165 10 2 165 165 5 3 165 205 9 4 205 205 40

[0128] Next, an inductively coupled plasma atomic emission spectrometer, a cyclonic nebulizer, and a Meinhand type concentric nebulizer were used for detection, and the instrument parameters were set as follows: RF power 1250 W, cooling gas flow rate 15 L / min, auxiliary gas flow rate 2.25 L / min, and carrier gas flow rate 0.7 L / min.

[0129] Embodiment 11

[0130] The method for determining heavy metal elements in polymers specifically comprises the following steps:

[0131] First, pre-treat the Nylon+GF sample as follows:

[0132] (1) crushing the polymer sample, wherein the average particle size of the crushed polymer sample is 20 μm;

[0133] (2) The crushed polymer sample was exposed to short-wave ultraviolet light for 2 h at a UV dose of 10,000 mJ / cm 2 .

[0134] Then weigh 0.20 g of the pretreated Nylon+GF sample, place it in a microwave digestion tank, add 7.0 mL of concentrated HNO3, 0.2 mL of H2O2, 1.0 mL of HClO4 and 0.5 mL of HF, perform microwave digestion according to the microwave digestion procedure, and then transfer it to a fixed volume of 25 mL.

[0135] Example 12

[0136] The method for determining heavy metal elements in polymers specifically comprises the following steps:

[0137] First, the PET samples were pretreated as follows:

[0138] (1) crushing the polymer sample, wherein the average particle size of the crushed polymer sample is 20 μm;

[0139] (2) The crushed polymer sample was exposed to short-wave ultraviolet light for 2 h at a UV dose of 10,000 mJ / cm 2 .

[0140] Then weigh 0.20 g of the pretreated PET sample, place it in a microwave digestion tank, add 7.0 mL of concentrated HNO3, 0.2 mL of H2O2, 1.0 mL of HClO4 and 0.5 mL of HF, perform microwave digestion according to the microwave digestion procedure, and then transfer it to a fixed volume of 25 mL.

[0141] Performance testing

[0142] Recovery and precision test:

[0143] Referring to the method described in Examples 1 to 4, 0.5 mg / L of lead ion standard solution was added to the test sample, and the analysis spectrum of heavy metal elements was set as follows: Pb 220nm or 182nm; Cd 214nm or 229nm; Hg 194nm or 185nm. Four parallel tests were performed under the same conditions, and the results were as follows:

[0144]

[0145]

[0146] The test results show that the recoveries of the heavy metal elements Pb, Cd and Hg are between 92.5% and 103.0%, and the test precision is less than 3%, which meets the relevant requirements of general trace test methods.

[0147] Detection limit test:

[0148] Referring to the method of Example 5, 11 blank test samples were measured under the same conditions, and the detection limit of the method can be calculated based on 3 times the standard deviation (3 times SD) of the measurement results. The measurement results are shown in the following table:

[0149]

[0150]

[0151] The test results show that the detection limits of heavy metal elements Pb, Cd and Hg are all less than 2.0 mg / kg, indicating that the detection limit of this method can fully meet the environmental protection requirements and testing needs of various countries and enterprises for electronic and electrical products.

[0152] Accuracy test:

[0153] Using a certified reference material (CRM), PE plastic pellets codenamed CRM680, the analysis was performed according to the method described in Example 6, and the test results were compared with the indicated values ​​of CRM680. The results are shown in the following table:

[0154]

[0155] The test results show that the error of heavy metal elements Pb, Cd and Hg is less than 14%, which can meet the requirements of general trace testing.

[0156] Material digestion test:

[0157] The test results of Examples 1 to 12 are summarized, and the results of digestion of plastic materials using the method described in the embodiments of the present invention are statistically shown in the following table:

[0158] Sample materials Final digestion results Sample materials Final digestion results PVC clear Bakelite clear PC clear PA clear PE clear PC+ABS clear PP clear PBT clear ABS clear Nylon+GF clear Silicone clear PET turbidity

[0159] The above results show that, except for a few polymer materials such as PET, the method of the present invention can decompose plastic or polymer materials in most electronic and electrical products and materials.

[0160] Comparative Example

[0161] Comparative Example 1

[0162] Referring to the methods described in Examples 1, 3 to 5 and 10, the acid digestion system HNO3 + H2O2 + HClO4 + HF in the examples was changed to HNO3 + H2O2 and HNO3 + HBF4 + H2O2, and material digestion tests were performed respectively. The results are shown in the following table:

[0163] <![CDATA[HNO3+H2O2]]> <![CDATA[HNO3+HBF4+H2O2]]> <![CDATA[HNO3+H2O2+HClO4+HF]]> PVC turbidity clear clear PE clear clear clear PP clear clear clear ABS turbidity turbidity clear PBT turbidity turbidity clear

[0164] The above results show that after combining the pretreatment means for plastic samples provided by the present application, most plastics can be digested by the HNO3+H2O2 system, while some plastics such as PBT still cannot be digested, and the digestion problem of plastic fillers (such as glass fiber or TiO2) cannot be solved. The acid digestion method of HNO3+HBF4+H2O2 can partially solve the digestion problem of fillers in plastics. However, the introduction of HClO4 helps the digestion of plastics, and the introduction of HF can better solve the digestion problem of fillers. The introduction of HCl does not significantly improve the final digestion effect in most cases, but easily leads to the decompression of the digestion tank. Therefore, the acid digestion system selected by the present invention is composed of: HNO3+H2O2+HClO4+HF, which effectively solves the problem that the existing acid digestion system cannot be used universally, and solves the problem that some materials cannot be digested, achieving the purpose of rapid and efficient digestion.

[0165] Comparative Example 2

[0166] This comparative example refers to the detection method of Examples 1 to 12. Before the measurement, the polymer sample is not crushed and irradiated with short-wave ultraviolet light, and then directly digested by microwave sealing. The results are as follows:

[0167] Sample materials Final digestion results Sample materials Final digestion results PVC clear Bakelite turbidity PC turbidity PA turbidity PE clear PC+ABS turbidity PP turbidity PBT turbidity ABS turbidity Nylon+GF turbidity Silicone turbidity PET turbidity

[0168] The above results show that if the polymer samples are not pretreated by crushing + short-wave ultraviolet light irradiation, it is difficult to achieve a good digestion effect on most plastic polymers by simply preparing a digestion mixture with appropriate ingredients and proportions. It can only achieve a good digestion effect on PVC polymers and PE polymers.

[0169] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0170] In addition, it should be understood that although this specification is described in accordance with the implementation methods, not every implementation method contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should take the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art. The technical details not described in detail in the present invention can be implemented by any prior art in the art. In particular, all technical features not described in detail in the present invention can be implemented by any prior art.

Claims

1. A method for determining heavy metal elements in polymers, characterized in that: The following steps are involved: The polymer sample is pretreated, and then the pretreated polymer sample is placed in a microwave digestion tank, an acidic digestion mixture is added, and microwave digestion treatment is performed according to a microwave digestion procedure, and then the sample is transferred to a fixed volume, and an inductively coupled plasma atomic emission spectrometer is used for detection; the acidic digestion mixture specifically comprises HNO3, H2O2, HClO4 and HF; the volume ratio of HNO3, H2O2, HClO4 and HF in the acidic digestion mixture is 7:0.2:1:0.5; The pre-processing comprises the following steps: (1) crushing the polymer sample, wherein the average particle size of the crushed polymer sample is 20-80 μm; (2) The crushed polymer sample is exposed to short-wave ultraviolet light for 2-15 hours at a UV dose of 10000-22000 mJ / cm 2 ; The microwave digestion procedure specifically comprises the following steps: S1, set the initial temperature to room temperature, gradually increase the temperature to 165℃, and the heating time is 10min; S2, the initial temperature is 165℃, and the constant temperature is maintained for 5 minutes; S3, the initial temperature is 165℃, gradually increase the temperature to 205℃, and the heating time is 9min; S4, the initial temperature is 205℃, and the constant temperature is maintained for 40 minutes.

2. The method for determining heavy metal elements in polymers according to claim 1, characterized in that: The spectrometer detection parameter settings are specifically as follows: RF power 1250 W, cooling gas flow 15 L / min, auxiliary gas flow 2.25 L / min, carrier gas flow 0.7 L / min.

3. An application of the method for determining heavy metal elements in polymers according to claim 1, characterized in that: The method can be used to detect heavy metal elements in plastic or polymer materials in electronic and electrical products and materials.

4. The use of the method for determining heavy metal elements in polymers according to claim 3, characterized in that: The heavy metal elements include lead, cadmium and mercury.

5. The use of the method for determining heavy metal elements in polymers according to claim 4, characterized in that: The analysis spectrum of the heavy metal elements is set as: Pb 220nm or 182nm; Cd 214nm; Hg 194nm.

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