Method for quantitatively detecting polycarbonate microplastics in soil

Abstract

The invention belongs to the field of micro-plastic detection, and discloses a method for quantitatively detecting polycarbonate micro-plastics in soil, which comprises the following steps: sorting the micro-plastics to obtain a sample to be detected, establishing a standard curve, and determining the content of the micro-plastics by substituting the standard curve. The invention discloses a high-sensitivity and high-precision polycarbonate micro-plastic detection technology based on a thermal cracking-gas chromatography-mass spectrometry (Py-GC-MS) detection means, and provides an effective analysis method for environment tracking and monitoring of micro-plastic pollution.

Description

Technical Field

[0001] The invention belongs to the technical field of polycarbonate microplastic detection, and particularly relates to a method for quantitatively detecting polycarbonate microplastics in soil. Background Art

[0002] Plastics are polymer materials formed by the polymerization of monomer molecules and are widely used in all aspects of human production and life. Plastics in the natural environment are transformed into microplastics and nanoplastics of varying sizes through the combined effects of abiotic factors such as natural light and biotic factors, which enter the environment. Compared with macroplastics, microplastics are too small to be analyzed and identified. At the same time, microplastics have a more obvious ability to accumulate pollutants due to their larger specific surface area. Therefore, the harm of microplastics entering the environment is far greater than that of macroplastics, and therefore they have attracted more attention.

[0003] According to the type of plastic skeleton, it can be divided into carbon-carbon skeleton plastic and polyester skeleton plastic. Different types of plastics have completely different material properties and environmental degradation performance. Polycarbonate (PC) is a widely used polyester plastic. It is a linear macromolecule polymerized from the monomer bisphenol A (BPA). It is used to make various engineering materials due to its excellent material properties.

[0004] Polycarbonate plastics that enter the environment will disintegrate into microplastics, which may become the matrix of environmental pollutants, resistance genes, and pathogenic bacteria on the one hand, and may also become the release source of endocrine disruptors BPA on the other hand. At the same time, due to the complex composition and characteristics of the soil, the separation, impurity removal and identification of soil microplastics face major challenges. Therefore, it is necessary to accurately separate polycarbonate microplastics from the soil and establish a highly sensitive, accurate qualitative and quantitative detection method for polycarbonate microplastics, which can provide accurate scientific data for environmental tracking and monitoring of polycarbonate microplastic pollution, and provide new perspectives and guidance for its restoration and management. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a method for quantitatively detecting polycarbonate microplastics in soil. Based on the pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) detection method, a highly sensitive and high-precision polycarbonate microplastic detection technology is disclosed, which provides an effective analytical method for environmental tracking and monitoring of microplastic pollution.

[0006] The technical solution of the present invention is as follows:

[0007] A method for quantitatively detecting polycarbonate microplastics in soil of the present invention comprises the following steps:

[0008] (1) Obtaining a sample to be tested: dissolving the separated polycarbonate microplastics in dichloromethane;

[0009] (2) Establishing a standard curve: Prepare dichloromethane solutions of polycarbonate standards with different concentration gradients, and use thermal cracking-gas chromatography-mass spectrometry for detection. The gasification products after thermal cracking enter the gas chromatography-mass spectrometer, with the mass of the polycarbonate standard as the X-axis and the peak area of ​​bisphenol A as the Y-axis to obtain a standard curve; wherein, the thermal cracking conditions are: thermal cracking at 500-800°C; the gas chromatography-mass spectrometry detection conditions are: DB-5MS chromatographic column (30m*250μm, 0.25μm), the column oven starting temperature is 40°C, maintained for 2min, heated to 200°C at 5°C / min, then heated to 300°C at 20°C / min, and maintained for 11min. The carrier gas is helium (99.999%), the flow rate is 1mL / min, the split ratio is set to 100:1, and the transmission line temperature is 300°C. The ionization mode is EI + , 70 eV, full scan mode and selected ion scan mode were performed simultaneously, the scan range was 20-500 m / z, the ion source temperature was 230 °C, and the quadrupole temperature was 150 °C;

[0010] (3) The sample to be tested adopts the same pyrolysis-gas chromatography-mass spectrometry detection conditions as step (2) to obtain the peak area of ​​bisphenol A in the sample to be tested, and substitutes it into the standard curve to obtain the mass of polycarbonate microplastics in the sample to be tested.

[0011] In one embodiment of the invention, step (1) includes adding a dry soil sample to a saturated ZnCl2 solution, collecting the overflowed liquid by an overflow method after mixing and dispersing, filtering with a glass cellulose membrane, washing with methanol, and then dissolving the glass cellulose membrane with dichloromethane to obtain a sample to be tested.

[0012] In one embodiment of the invention, in step (2), the temperature of thermal cracking is 550°C or 700°C.

[0013] In one embodiment of the invention, in steps (2) to (3), 1 μL of deuterated anthracene is added as an internal standard to the polycarbonate standards and the samples to be tested at different concentration gradients.

[0014] In one embodiment of the invention, in step (2), a standard curve for detecting the mass of the sample to be tested in the range of 0.001-0.5 μg is established using 0.001 μg, 0.01 μg, 0.1 μg, 0.2 μg and 0.5 μg of polycarbonate standards.

[0015] In one embodiment of the invention, in step (2), 0.5 μg, 1 μg, 2 μg, 5 μg and 10 μg of polycarbonate standards are used to establish a standard curve for detecting the mass of the sample to be tested in the range of 0.5-10 μg.

[0016] In one embodiment of the invention, in step (2), the retention time of bisphenol A is 37.475 min.

[0017] In one embodiment of the invention, in steps (2) to (3), a methanol solution containing 25% tetramethylammonium hydroxide is added to the polycarbonate standard and the sample to be tested for derivatization treatment.

[0018] In one embodiment of the invention, the retention time of 2,2-bis(4'-methoxyphenyl)propane is 36.508 min. In one embodiment of the invention, in step (2), the pyrolysis-gas chromatography-mass spectrometry instrument is Frontier Labs EGA / Py-3030D Curie point pyrolyzer and Agilent 7890A-5975.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The present invention provides a method for quantitatively detecting polycarbonate microplastics in soil, which is a sensitive and accurate qualitative and quantitative detection method for polycarbonate microplastics by monitoring the polycarbonate thermal cracking product bisphenol A through thermal cracking and gas mass spectrometry-chromatography.

[0021] (2) The present invention further derivatizes polycarbonate and adds deuterated anthracene as an internal standard, thereby making the detection method of polycarbonate microplastics more sensitive and accurate. It can be used for the accurate quantification of polycarbonate microplastics from different environmental sources, thereby analyzing the concentration of polycarbonate microplastics in different environments and their degree of pollution.

[0022] (3) The present invention provides a method for accurately separating soil polycarbonate microplastics from soil. Due to the complex composition and characteristics of soil, the separation, impurity removal and identification of soil microplastics face major challenges. The present invention provides a pure single microplastic as a substance to be detected for environmental tracking and monitoring of polycarbonate microplastic pollution.

[0023] (4) The qualitative and quantitative detection method of polycarbonate microplastics of the present invention is rapid, requires only trace amounts of substrate, is stable in nature, and can be used to detect microplastics of different concentrations after a standard curve is established once, providing a convenient and fast method for environmental tracking and monitoring of pollution from different polycarbonate microplastics. The establishment of this detection method can provide scientific data for environmental tracking and monitoring of microplastic pollution, and provide a new perspective and guidance for the restoration and management of environmental pollution caused by polycarbonate plastic waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1GC-MS spectra of the polycarbonate standard product of Example 1 of the present invention at thermal cracking temperatures of 550°C and 700°C, wherein (a) is at a thermal cracking temperature of 550°C, and (b) is at a thermal cracking temperature of 700°C;

[0025] Figure 2 This is a schematic diagram of the characteristic compound bisphenol A (m / z is 228) with a retention time of 37.475 min in the thermal cracking product of Example 1 of the present invention, wherein (a) is a thermal cracking temperature of 550°C, and (b) is a thermal cracking temperature of 700°C.

[0026] Figure 3 This is the GC-MS total ion chromatogram of the polycarbonate standard product of Example 2 of the present invention at a thermal cracking temperature of 550° C. with and without tetramethylammonium hydroxide added. The red curve is with tetramethylammonium hydroxide added, and the black curve is without tetramethylammonium hydroxide added.

[0027] Figure 4 This is a chromatogram of deuterated anthracene (internal standard; m / z is 188) and 2,2-bis(4'-methoxyphenyl)propane (quantitative molecule; m / z is 256,241) in selected ion monitoring (SIM) mode at a thermal cracking temperature of 550° C. for the polycarbonate standard of Example 3 of the present invention.

[0028] Figure 5 This is a schematic diagram of the analysis of quantitative detection of polycarbonate microplastics in different soils according to Example 4 of the present invention. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0030] Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention, so the present invention is not limited to the specific implementation disclosed below.

[0031] Example 1

[0032] Take 1μg of polycarbonate standard and dissolve it in 1mL of dichloromethane. Use thermal cracking-gas chromatography-mass spectrometry for detection. The gasification product after thermal cracking enters the gas chromatography-mass spectrometer. The conditions of thermal cracking are: thermal cracking at 550℃ or 700℃ respectively, and the effect of temperature on detection is investigated; the gas chromatography-mass spectrometry detection conditions are: DB-5MS chromatographic column (30m*250μm, 0.25μm), the column oven starting temperature is 40℃, keep it for 2min, increase the temperature to 200℃ at 5℃ / min, and then increase it to 300℃ at 20℃ / min, and keep it for 11min. The carrier gas is helium (99.999%), the flow rate is 1mL / min, the split ratio is set to 100:1, and the transmission line temperature is 300℃. The ionization mode is EI + , 70 eV, full scan mode and selected ion scan mode were performed simultaneously, the scan range was 20-500 m / z, the ion source temperature was 230 °C, and the quadrupole temperature was 150 °C.

[0033] The obtained mass spectrum was compared with the NIST14 standard spectrum library, and the generated pyrolysis products were analyzed, such as Figure 1 As shown in Table 1. It was found that when the thermal cracking temperature was 550°C, the mass spectrum of the polycarbonate standard was characterized by 22 thermal cracking products; when the thermal cracking temperature was 700°C, the mass spectrum of the polycarbonate standard was characterized by 29 thermal cracking products, indicating that polycarbonate had more thermal cracking products at a thermal cracking temperature of 700°C than at 550°C, including single benzene ring aromatic compounds such as benzene, toluene, 1,3-dimethylbenzene, (1-methylethyl)-benzene, styrene, and ethylphenol.

[0034] When the retention time is 37.475min, no matter at 550℃ or 700℃, there is a characteristic compound with a large peak area in the thermal cracking products, which is determined to be bisphenol-A (BPA). Figure 2 As shown. When the pyrolysis temperature is 550℃ and 700℃, the peak area of ​​the characteristic ion m / z 228 of the pyrolysis product bisphenol A is extracted and calculated, which are 18148809.49 and 9844783.78 respectively, as shown in Table 2. Therefore, for the detection of polycarbonate microplastics, bisphenol A can be selected as a characteristic compound to quantitatively detect polycarbonate microplastics. At the same time, when the pyrolysis temperature is 550℃ and 700℃, the peak area ratio of bisphenol A is 1.84, indicating that the same mass of polycarbonate microplastics will form more stable bisphenol A after pyrolysis at 550℃ than at 700℃, which is more conducive to the accuracy of detection and can also reduce energy consumption.

[0035] Table 1

[0036]

[0037] Table 2

[0038]

[0039] Example 2

[0040] Derivatization treatment: In order to further improve the sensitivity of quantitative detection of polycarbonate microplastics, 5 μL of methanol solution containing 25% tetramethylammonium hydroxide was added to the polycarbonate standard for derivatization treatment, and then thermal cracking was carried out. The thermal cracking temperature was 550°C, and the rest was the same as Example 1. The derivatization reagent can derivatize bisphenol A (m / z is 228) generated by thermal cracking of polycarbonate into 2,2-bis(4'-methoxyphenyl)propane (m / z is 256,241), and the derivative is used as a quantitative molecule. The retention time of bisphenol A is 37.475 min, and the retention time of 2-bis(4'-methoxyphenyl)propane is 36.508 min. The difference in mass spectrometry signal intensity between the derivatization treatment group and the non-derivatization treatment group is compared, as shown in FIG. Figure 3 As shown, the results showed that the detection sensitivity was significantly improved after derivatization treatment.

[0041] Example 3

[0042] The standard curve without internal standard (IS) was established by dissolving different masses of polycarbonate standard (0.001 μg, 0.01 μg, 0.1 μg, 0.2 μg, 0.5 μg, 1 μg, 2 μg, 5 μg, 10 μg) in 1 mL of dichloromethane, preparing standard solutions of different concentrations, adding 5 μL of methanol solution containing 25% tetramethylammonium hydroxide for derivatization treatment, and then using pyrolysis-gas chromatography-mass spectrometry for detection, the pyrolysis temperature was 550°C, and Py-GC-MS qualitative and quantitative detection was performed, and the rest was the same as Example 2. According to the test results of polycarbonate standards (0.001 μg, 0.01 μg, 0.1 μg, 0.2 μg, 0.5 μg) and polycarbonate standards (0.5 μg, 1 μg, 2 μg, 5 μg, 10 μg), the mass of the polycarbonate standard was used as the X-axis and the peak area of ​​2,2-bis(4'-methoxyphenyl)propane was used as the Y-axis to draw standard curves, as shown in Table 3.

[0043] The standard curve with the addition of internal standard (IS) was established: 1 μL of deuterated anthracene (m / z 188) was added as the internal standard (IS) to the above polycarbonate standard solution with different concentrations without internal standard, and the thermal cracking temperature was 550°C. The qualitative and quantitative detection of Py-GC-MS was performed. The other procedures were the same as those in Example 2. Figure 4As shown, it shows that the internal standard has good stability in this detection system. According to the detection results of polycarbonate standards (0.001μg, 0.01μg, 0.1μg, 0.2μg, 0.5μg) containing internal standards and polycarbonate standards (0.5μg, 1μg, 2μg, 5μg, 10μg), the mass of polycarbonate standards is taken as the X-axis and the peak area of ​​2,2-bis(4'-methoxyphenyl)propane is taken as the Y-axis, and standard curves are drawn respectively, as shown in Table 3.

[0044] The quality of the two sets of standard curves with different mass concentration ranges was evaluated. In the linear range of 0.001-0.5 μg polycarbonate, after adding the internal standard (IS), the fit of the m / z 256 and 241 signals reached the best, that is, R 2 The RSE is 0.9934 and 4.06%. In the linear range of 0.5-10 μg polycarbonate, after adding the internal standard (IS), the fitting degree of the m / z 256 and 241 signals reached the best, that is, R 2 The value of the standard curve with internal standard (IS) was 0.9996 and the RSE was 0.95%.

[0045] Table 3

[0046]

[0047] Example 4

[0048] A saturated ZnCl2 solution with a concentration of 1.68 g / mL was used to sort polycarbonate microplastics in soil samples. The soil samples were dried in an oven at 60-80°C for 24 hours and then transferred to a clean glass beaker. 1 g of soil was weighed from the experimental sample, added to 20 mL of saturated ZnCl2 solution and mixed thoroughly, and then the sample was dispersed by ultrasound (5 min). The mixture was stirred for 10 min to float the suspended matter including microplastics, and the overflowing liquid was collected by overflow method; then, the overflowing supernatant was filtered with a 0.22 μm glass cellulose membrane; the glass cellulose membrane was rinsed with 50 mL of methanol to fully remove small molecular impurities on the membrane surface; finally, the glass cellulose membrane containing microplastics was dissolved with 1 mL of dichloromethane to obtain the sample to be analyzed.

[0049] The sample to be analyzed was added to the pyrolysis cup, and then 1 μL of deuterated anthracene (internal standard) and 5 μL of methanol solution containing 25% tetramethylammonium hydroxide (derivatization reagent) were added, which was recorded as the experimental group. Only 1 μL of internal standard deuterated anthracene and 5 μL of methanol solution containing 25% tetramethylammonium hydroxide were added to the pyrolysis cup containing dichloromethane, which was recorded as the negative control (PC-control). The same detection conditions as in Example 3 were adopted, and the ion monitoring (SIM) mode was selected to detect the ion peaks of 2,2-bis(4'-methoxyphenyl)propane (m / z was 256, 241). The peak areas of the characteristic ion m / z of 2,2-bis(4'-methoxyphenyl)propane of 256 were extracted and calculated (as the y value), and the standard curve formula y=0.0027+0.6982x or y=0.05504+0.61957x was substituted according to different mass concentration ranges to calculate the content of polycarbonate microplastics in the soil (x value).

[0050] The contents of PC microplastics in four different soil groups (NA-PC-Sterilize, UNA-PC-Sterilize, NA-PC-Soil, and UNA-PC-Soil) were as follows: the concentration of PC microplastics in NA-PC-Sterilize soil was 5.52 ± 5.03 μg / g, the concentration of PC microplastics in UNA-PC-Sterilize soil was 1.88 ± 1.34 μg / g, the concentration of PC microplastics in NA-PC-Soil soil was 13.95 ± 1.85 μg / g, and the concentration of PC microplastics in UNA-PC-Soil soil was 142.93 ± 31.54 μg / g, as shown in Figure 2 . Figure 5 shown.

[0051] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for quantitatively detecting polycarbonate microplastics in soil, characterized in that: The following steps are involved: (1) Obtaining the sample to be tested: adding the dry soil sample to a saturated ZnCl2 solution, collecting the overflowed liquid by the overflow method after mixing and dispersing, filtering it with a glass cellulose membrane, washing it with methanol, and then dissolving the glass cellulose membrane with dichloromethane to obtain the sample to be tested; (2) Establishment of standard curve: Prepare dichloromethane solution of polycarbonate standard with different concentration gradients, and use thermal cracking-gas chromatography-mass spectrometry for detection. The gasification product after thermal cracking enters the gas chromatography-mass spectrometer, with the mass of polycarbonate standard as the X-axis and the peak area of ​​bisphenol A as the Y-axis to obtain the standard curve; wherein, the thermal cracking conditions are: thermal cracking at 500-800℃; gas chromatography-mass spectrometry detection conditions are: DB-5MS chromatographic column (30m*250μm, 0.25μm), the column oven starting temperature is 40℃, maintained for 2min, heated to 200℃ at 5℃ / min, then heated to 300℃ at 20℃ / min, and maintained for 11min. The carrier gas is helium, the flow rate is 1mL / min, the split ratio is set to 100:1, and the transmission line temperature is 300℃. The ionization mode is EI + , 70 eV, full scan mode and selected ion scan mode were performed simultaneously, the scan range was 20-500 m / z, the ion source temperature was 230 °C, and the quadrupole temperature was 150 °C; (3) The sample to be tested adopts the same pyrolysis-gas chromatography-mass spectrometry detection conditions as step (2) to obtain the peak area of ​​bisphenol A in the sample to be tested, and substitutes it into the standard curve to obtain the mass of polycarbonate microplastics in the sample to be tested.

2. The method for quantitatively detecting polycarbonate microplastics in soil according to claim 1, characterized in that: In step (2), the temperature of thermal cracking is 550°C or 700°C.

3. The method for quantitatively detecting polycarbonate microplastics in soil according to claim 2, characterized in that: In steps (2) to (3), 1 μL of deuterated anthracene was added as an internal standard to the polycarbonate standards and samples at different concentration gradients.

4. The method for quantitatively detecting polycarbonate microplastics in soil according to claim 3, characterized in that: In step (2), a standard curve for detecting the mass of the sample to be tested ranging from 0.001 μg to 0.5 μg is established using 0.001 μg, 0.01 μg, 0.1 μg, 0.2 μg and 0.5 μg of polycarbonate standards.

5. The method for quantitatively detecting polycarbonate microplastics in soil according to claim 3, characterized in that: In step (2), 0.5 μg, 1 μg, 2 μg, 5 μg and 10 μg of polycarbonate standards are used to establish a standard curve for detecting the mass of the sample to be tested in the range of 0.5-10 μg.

6. The method for quantitatively detecting polycarbonate microplastics in soil according to claim 3, characterized in that: In step (2), the retention time of bisphenol A is 37.475 min.

7. The method for quantitatively detecting polycarbonate microplastics in soil according to claim 3, characterized in that: In steps (2) to (3), tetramethylammonium hydroxide is added to the polycarbonate standard and the sample to be tested for derivatization treatment.

8. The method for quantitatively detecting polycarbonate microplastics in soil according to claim 7, characterized in that: The retention time of 2,2-bis(4'-methoxyphenyl)propane is 36.508 min.

9. The method for quantitatively detecting polycarbonate microplastics in soil according to claim 1, characterized in that: In step (2), the pyrolysis-gas chromatography-mass spectrometry instrument is selected from Frontier Labs EGA / Py-3030D Curie point pyrolyzer and Agilent 7890A-5975C.

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