Electrospray ionization mass spectrometry imaging detection method for plastic additive on plastic surface

Abstract

The invention discloses an electrospray ionization mass spectrometry imaging detection method for a plastic additive on a plastic surface, and belongs to the technical field of plastic additive detection.The method comprises the following steps of obtaining a standard substance map, processing a sample, collecting data, and processing the collected data, converting mass spectrum information of the target plastic additive distributed on the surface of the pretreated sample into image information according to the mass spectrum, and analyzing the extracted image information; the method focuses on migration visual analysis of the plastic additive, complex sample pretreatment is not needed, detection can be carried out only through simple steps, the sensitivity is high, and trace additives in plastic can be detected; the DESI-MSI also has the advantage of high throughput, can visualize the migration process of the plastic additive into the surface, is very clear and visual, helps to obtain the migration process information of the plastic additive at different stages of the life cycle of a plastic product, and provides a new method for high-throughput analysis, rapid detection and distribution visualization of the plastic additive on the plastic surface.

Description

Technical Field

[0001] This application belongs to the field of plastic additive detection technology, and in particular relates to an electrospray ionization mass spectrometry imaging method for detecting plastic additives on plastic surfaces. Background Technology

[0002] To maintain the stability of plastics and improve their performance, various additives are added to them. Since, except for a few reactive additives, plastic additives do not bind to macromolecular polymers in the form of covalent bonds, they are prone to migrate into the contact medium during use. The released plastic additives enter the human body through ingestion, inhalation, skin contact, etc., either with microplastics or directly in the form of plastic additives, and participate in chemically mediated biotoxicity. Detecting plastic additives on the surface of plastics is of great significance for clarifying their migration path from plastics into the environment and for further exploring the environmental toxicity of plastic products.

[0003] Patent CN112229936B discloses a high-throughput analytical method for the simultaneous detection of 33 plastic additives in food contact materials based on liquid chromatography-tandem mass spectrometry. This method can detect and analyze 33 plastic additives within 12 minutes, and has the advantages of high sensitivity, good separation, short detection time, and high detection efficiency, which can meet the high-throughput detection needs of multiple plastic additives in food contact materials. However, its detection method is complicated, requiring the preparation of standard solutions and extraction of samples with methanol to prepare sample solutions. Traditional methods for detecting plastic additives, such as GC-MS and HPLC, often require homogenization of plastic samples followed by solvent extraction of plastic additives, which requires lengthy sample pretreatment and chromatographic separation steps. Infrared spectroscopy is difficult to detect low concentrations of plastic additives due to spatial resolution limitations. Summary of the Invention

[0004] The purpose of this application is to provide an electrospray ionization mass spectrometry imaging method for detecting plastic additives on plastic surfaces, in order to solve the technical problems in the prior art where sample pretreatment for detecting plastic additives on plastic surfaces is complicated and the migration process of surface plastic additives cannot be visualized.

[0005] To achieve the above objectives, the technical solution adopted in this application is: to provide an electrospray ionization mass spectrometry imaging detection method for plastic additives on plastic surfaces, specifically including the following steps: (i) Obtaining standard substance spectra: Mass spectrometry is used to detect plastic additives and obtain primary and secondary mass spectra. (ii) Sample preparation: Rinse the plastic sample to be tested, air dry, and obtain a pretreated sample for later use; (III) Data Acquisition: Electrospray ionization of the pretreated sample was performed, and data was collected to obtain electrospray ionization data; (iv) Data processing and analysis: The electrospray ionization data are processed, and the mass spectrometry information of the target plastic additive on the surface of the pretreated sample is converted into image information based on the first-level mass spectrometry and the second-level mass spectrometry. The extracted image information is then analyzed.

[0006] In one embodiment, Step (I) The plastic additives are triethyl phosphate, 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol, pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid), diethyl phthalate, dioctyl phthalate, octyl methoxycinnamate, dimethyl phthalate, triethyl phosphate, tributyl acetylacetonate, or triisobutyl phosphate.

[0007] In one embodiment, Step (2) The plastic sample to be tested is rinsed with ultrapure water.

[0008] In one embodiment, Rinse three times.

[0009] In one embodiment, Electrospray ionization was performed using a mass spectrometer, with the solvent being a mixture of acetonitrile, water, and ammonia.

[0010] In one embodiment, The volume ratio of acetonitrile, water, and ammonia is 5:4:1.

[0011] In one embodiment, The solvent flow rate was 5 μl / min.

[0012] In one embodiment, Step (3) The specific parameters of the mass spectrometer are as follows: Scan mode: Negative; Mass-to-charge ratio: 50-1300 m / z; Electrospray voltage: 4.5 kV; Nitrogen pressure: 0.4 MPa.

[0013] In one embodiment, The specific steps for processing the data in step (iv) are as follows: import the data collected in step (iii) into the imzMLConvert software and convert the data into imzML format.

[0014] In one embodiment, In step (iv), the mass spectrometry information is converted into image information using the MSiReader program.

[0015] This application provides an electrospray ionization mass spectrometry imaging method for detecting plastic additives on plastic surfaces, which has the following advantages compared with the prior art: Unlike most qualitative analysis studies, this application focuses on the visualization analysis of plastic additive migration. Compared to detection methods that require homogenized samples, solvent extraction, chromatographic separation, and purification, the DESI-MSI method requires no complex sample pretreatment, only a simple pretreatment step. Compared to infrared spectroscopy, mass spectrometry imaging has a sensitivity ranging from ppm to ppb, enabling the detection of trace additives in plastics. DESI-MSI also has the advantage of high throughput, allowing for the simultaneous analysis of multiple additives and their degradation products in a single experiment, providing multidimensional chemical information. Furthermore, it can visualize the migration process of plastic additives to the surface, providing a very clear and intuitive view. This helps to obtain information on the migration process of plastic additives at different stages of the plastic product lifecycle, providing a new method for high-throughput analysis, rapid detection, and distribution visualization of plastic additives on plastic surfaces, which can be used in scientific research in fields such as environmental science and food safety. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 The image on the left shows the distribution of triethyl phosphate on the plastic surface. Figure 1 The middle image shows the distribution of 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol on a plastic surface. Figure 1 The third image from the left shows the distribution of pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid) on a plastic surface. Figure 2 The image on the left shows the distribution of acetylated tributyl citrate (m / z 401.23) on the surface of PP (polypropylene) before high-temperature aging. Figure 2 The second image from the left shows the distribution of acetylated tributyl citrate (m / z 401.23) on the surface of PP (polypropylene) after high-temperature aging. Figure 3 The distribution of octyl methoxycinnamate detected in LDPE plastic on the plastic surface, from left to right: before aging, simulated gastric juice aging, seawater aging, and ultraviolet aging; Figure 4The distribution of dimethyl phthalate detected in HDPE plastic on the plastic surface, from left to right: before aging, simulated gastric juice aging, seawater aging, and ultraviolet aging; Figure 5 The distribution of triethyl phosphate detected in PS plastic on the plastic surface, from left to right: before aging, simulated gastric juice aging, seawater aging, and ultraviolet aging. Detailed Implementation

[0018] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, this application will be further described in detail. It should be understood that the specific embodiments described herein are only for explaining this application and are not intended to limit this application.

[0019] In one embodiment, an electrospray ionization mass spectrometry imaging detection method for plastic additives on a plastic surface specifically includes the following steps: (i) Obtaining standard material spectra: Mass spectrometry is performed on plastic additives to obtain a primary mass spectrum. The precise mass-to-charge ratio is determined by the primary mass spectrum. The mass-to-charge ratio is used for secondary mass spectrometry imaging to obtain a secondary mass spectrum. The structure of the secondary mass spectrum can be determined again by comparing ion fragments. Specifically, primary mass spectrometry is used to determine the relative molecular mass and molecular formula of plastic additive molecules, as well as to conduct preliminary screening of compounds in samples; secondary mass spectrometry is used to determine the mass-to-charge ratio of target plastic additives, analyze the molecular structure of substances, and infer information such as functional groups, chemical bond connections, and amino acid sequences in molecules by analyzing the type, mass, and relative intensity of fragment ions, thereby enabling the structural identification of complex molecules. Common plastic additives include, but are not limited to, triethyl phosphate, 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol, pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid), diethyl phthalate, dioctyl phthalate, octyl methoxycinnamate, dimethyl phthalate, triethyl phosphate, tributyl acetylacetonate, or triisobutyl phosphate; (II) Sample preparation: The plastic sample to be tested is rinsed three times with ultrapure water and dried to obtain a pretreated sample for later use; (III) Data Acquisition: The pretreated sample is placed on a mobile platform that moves according to a set program. A constant flow syringe pump is used to push the desorption solution in the syringe to impact the surface of the pretreated sample, and then the solution is sputtered into the mass spectrometer. The mass spectrometer parameters are set, the sample is electrosprayed and ionized, and the data is collected to obtain the electrospray ionization data. The desorption solution was a mixture of acetonitrile, water, and ammonia in a volume ratio of 5:4:1; the solvent used in the mass spectrometer was a mixture of acetonitrile, water, and ammonia in a volume ratio of 5:4:1, and the solvent flow rate was 5 μl / min. The specific parameters of the mass spectrometer are as follows: Scan mode: Negative; Mass-to-charge ratio: 50-1300 m / z; Electrospray voltage: 4.5 kV; Nitrogen pressure: 0.4 MPa; (iv) Data Processing and Analysis: The obtained electrospray ionization data were imported into imzMLConvert software to convert the data into imzML format. Based on the primary and secondary mass spectra, the mass spectrometry information of the target plastic additive distribution on the surface of the pretreated sample was converted into image information using the MSiReader program. The extracted image information was then analyzed; the details are as follows: S1. Convert the raw format file obtained from the mass spectrometry scan to imzML format using imzMLConvert software; S2. Import the file obtained in the previous step into the MSiReader program, input the standard mass-to-charge ratio of the plastic additive, set the normalization method to Median normalization, and obtain the distribution information of the plastic additive on the plastic surface. Figure 1 The figures show the distribution of three plastic surface additives on the plastic surface: triethyl phosphate, 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol, and pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid). Figure 1 It can be seen that plastic additives are relatively evenly distributed on the surface of the plastic; before PP plastic was aged at 40 ℃ for 10 days, such as Figure 2 As shown in the left image, the acetyltributyl citrate additive on the PP plastic surface is poorly distributed and exhibits low fluorescence intensity; after aging at 40 ℃ for 10 days, as shown in the left image... Figure 2 As shown in the second image from the left, the distribution of acetylated tributyl citrate on the plastic surface is significantly increased, and the fluorescence intensity is also increased, indicating that the content of acetylated tributyl citrate on the surface of aged PP is significantly increased.

[0020] Example 2 This embodiment differs from Embodiment 1 in that the plastic sample to be tested is replaced with low-density polyethylene (LDPE) plastic, and the LDPE plastic is subjected to simulated gastric juice aging, seawater aging, and ultraviolet aging. The distribution of surface additives is detected according to the method of Embodiment 1, and the results are as follows. Figure 3 As shown.

[0021] Example 3 The difference between this embodiment and Embodiment 2 is that the plastic sample to be tested is replaced with high-density polyethylene (HDPE) plastic. All other operations are the same, and the distribution of surface additives is detected. The results are as follows: Figure 4 As shown.

[0022] Example 4 The difference between this embodiment and Embodiment 2 is that the plastic sample to be tested is replaced with polystyrene (PS) plastic. All other operations are the same, and the distribution of surface additives is detected. The results are as follows: Figure 5 As shown.

[0023] In Example 2, octyl methoxycinnamate, widely used as an ultraviolet absorber in plastic manufacturing, was detected in LDPE plastic. Its local ionic strength increased significantly after aging in simulated gastric juice, but showed no significant change after aging in seawater. However, its average ionic response intensity increased significantly under ultraviolet aging. In Example 3, dimethyl phthalate, a common plasticizer in plastics, was detected in HDPE. Its ionic response intensity increased slightly after aging in simulated gastric juice, but decreased significantly after aging in seawater and under ultraviolet light. In Example 4, triethyl phosphate, a plasticizer, was detected in PS plastic. Its distribution on the plastic surface also increased significantly after aging in simulated gastric juice, but tended to be uneven after aging in seawater and under ultraviolet light.

[0024] The results of Examples 1-4 show that the method provided in this application can clearly demonstrate the process changes of various plastic additives migrating to the plastic surface during environmental aging.

[0025] This application provides an electrospray ionization mass spectrometry imaging detection method for plastic additives on plastic surfaces, comprising the following steps: performing mass spectrometry detection on the plastic additives to obtain corresponding primary and secondary mass spectra; rinsing the plastic sample to be tested, drying it to obtain a pretreated sample for later use; performing electrospray ionization on the pretreated sample and collecting data to obtain electrospray ionization data; processing the electrospray ionization data, and converting the mass spectrometry information of the target plastic additives distributed on the surface of the pretreated sample into image information based on the primary and secondary mass spectra, and analyzing the extracted image information; compared with detection methods that require sample homogenization, solvent extraction, chromatographic separation, and purification, DESI-M... The SI method requires no complex sample pretreatment, only a simple pretreatment step for detection. Compared with infrared spectroscopy, mass spectrometry imaging has a sensitivity of ppm to ppb, which can detect trace additives in plastics. DESI-MSI also has the advantage of high throughput, and can analyze multiple additives and their degradation products in a single experiment, providing multidimensional chemical information. It can also visualize the migration process of plastic additives into the surface, which is very clear and intuitive. It helps to obtain information on the migration process of plastic additives at different stages of the plastic product life cycle, and provides a new method for high-throughput analysis, rapid detection and distribution visualization of plastic additives on plastic surfaces. It can be used for scientific research in fields such as environmental science and food safety.

[0026] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for detecting plastic additives on plastic surfaces using electrospray ionization mass spectrometry imaging, characterized in that, Specifically, the following steps are included: (i) Obtaining standard substance spectra: Mass spectrometry is used to detect plastic additives and obtain primary and secondary mass spectra. (ii) Sample preparation: Rinse the plastic sample to be tested, air dry, and obtain a pretreated sample for later use; (III) Data Acquisition: Electrospray ionization is performed on the pretreated sample, and data is collected to obtain electrospray ionization data; (iv) Data processing and analysis: The electrospray ionization data is processed, and the mass spectrometry information of the target plastic additive on the surface of the pretreated sample is converted into image information based on the first-level mass spectrometry spectrum and the second-level mass spectrometry spectrum. The extracted image information is then analyzed.

2. The method for detecting plastic additives on plastic surfaces by electrospray ionization mass spectrometry imaging according to claim 1, characterized in that, The plastic additives mentioned in step (I) are triethyl phosphate, 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol, pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid), diethyl phthalate, dioctyl phthalate, octyl methoxycinnamate, dimethyl phthalate, triethyl phosphate, tributyl acetylacetonate, or triisobutyl phosphate.

3. The method for detecting plastic additives on plastic surfaces by electrospray ionization mass spectrometry imaging according to claim 1, characterized in that, In step (ii), the plastic sample to be tested is rinsed with ultrapure water.

4. The method for detecting plastic additives on plastic surfaces by electrospray ionization mass spectrometry imaging according to claim 3, characterized in that, The rinsing is performed three times.

5. The method for detecting plastic additives on plastic surfaces by electrospray ionization mass spectrometry imaging according to claim 1, characterized in that, In step (iii), electrospray ionization is performed using a mass spectrometer, and the solvent used in the mass spectrometer is a mixture of acetonitrile, water and ammonia.

6. The method for detecting plastic additives on plastic surfaces by electrospray ionization mass spectrometry imaging according to claim 5, characterized in that, The volume ratio of acetonitrile, water, and ammonia is 5:4:

1.

7. The method for detecting plastic additives on plastic surfaces by electrospray ionization mass spectrometry imaging according to claim 5, characterized in that, The solvent flow rate is 5 μl / min.

8. The method for detecting plastic additives on plastic surfaces by electrospray ionization mass spectrometry imaging according to claim 5, characterized in that, The specific parameters of the mass spectrometer mentioned in step (iii) are as follows: Scan mode: Negative; Mass-to-charge ratio: 50-1300 m / z; Electrospray voltage: 4.5 kV; Nitrogen pressure: 0.4 MPa.

9. The method for detecting plastic additives on plastic surfaces by electrospray ionization mass spectrometry imaging according to claim 1, characterized in that, The specific steps for processing the data in step (iv) are as follows: import the data collected in step (iii) into the imzMLConvert software and convert the data into imzML format.

10. The method for detecting plastic additives on plastic surfaces by electrospray ionization mass spectrometry imaging according to claim 1, characterized in that, In step (iv), the mass spectrometry information is converted into image information using the MSiReader program.

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