Method for screening light stabilizer and kit thereof

Abstract

The invention discloses a method and kit for screening a light stabilizer, and the method for screening the light stabilizer comprises the following steps: carrying out initial dissolution on sample powder to be detected by using a first solvent to obtain an initial dissolution solution; diluting the initial dissolving solution by using a second solvent to obtain a diluted dissolving solution; mixing the initial dissolved solution by using a non-solvent, and carrying out sedimentation treatment to separate out a polymer high-molecular compound so as to obtain a sedimentation solution; carrying out centrifugal treatment on the sedimentation liquid so as to obtain supernate; dropwise adding the diluted solution and the supernatant to a carrier plate of which the surface is covered with an auxiliary ionized surface construction matrix, and carrying out open-type mass spectrometry detection to obtain mass spectrometry information of the sample to be detected; and analyzing and comparing the mass spectrum information of the to-be-detected samples of the diluted dissolving solution and the supernate so as to obtain the type of the light stabilizer. According to the method, rapid screening analysis of multiple light stabilizers in degradable plastics is realized, the accuracy and sensitivity are high, the analysis time is short, and the detection speed is high.

Description

Technical Field

[0001] This invention relates to the field of analytical chemistry, and more specifically, to a method and kit for screening light stabilizers. Background Technology

[0002] The application of biodegradable plastics is expanding across various fields. The variety of additives used to enhance polymer performance is also increasing proportionally. Adding 0.05% w to 3% w of light stabilizer to plastics can prevent degradation caused by light exposure. This helps extend the lifespan of the plastic and maintain its physical properties. The exact amount of light stabilizer added depends on the type of plastic, the intended use environment, and the desired performance characteristics. Information about additive content is typically not indicated on the label of the final plastic product. The degradation process of plastics reduces their mechanical properties and releases additives into the environment, causing pollution and health risks. Detecting light stabilizers in biodegradable plastics is crucial for ensuring the safety and compliance of plastic products.

[0003] Traditional methods for analyzing additives in biodegradable plastics are time-consuming, especially for detecting migratable substances in food packaging materials. These methods typically involve sample extraction, chromatographic separation (e.g., gas chromatography or liquid chromatography), and finally detection using mass spectrometry or UV / Vis spectroscopy. Furthermore, the extraction process is susceptible to interference from environmental contaminants. Pyrolysis-gas chromatography / mass spectrometry (Py-GC / MS) is suitable for the identification and semi-quantitative analysis of organic plastic additives (OPAs), offering advantages such as reduced sample preparation steps and minimized contamination. However, the high-temperature pretreatment process can damage the structure of the analyte, and the analytical equipment is expensive. Commonly used spectroscopic methods such as Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy can rapidly screen additives in plastics within minutes. However, due to strong interference from background signals and subtle spectral differences among additives, spectroscopic methods struggle to reliably identify mixed additives and perform quantitative analysis.

[0004] Therefore, screening methods for unknown light stabilizers in degradable plastics based on on-site analysis still urgently need to be developed. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. Therefore, one object of this invention is to provide a method for screening light stabilizers, which achieves rapid and short-time one-time screening analysis of multiple light stabilizers in biodegradable plastics.

[0006] According to one aspect of the present invention, a method for screening light stabilizers is provided. According to an embodiment of the present invention, the method includes: initially dissolving a sample powder to be tested using a first solvent to obtain an initial solution; diluting the initial solution using a second solvent to obtain a diluted solution; mixing the initial solution with a non-solvent and performing a sedimentation treatment to precipitate a polymer compound to obtain a sediment; centrifuging the sediment to obtain a supernatant; adding the diluted solution and the supernatant dropwise onto a substrate coated with an auxiliary ionization surface constructing matrix, and performing open-type mass spectrometry to obtain mass spectrometry information of the sample to be tested; and analyzing and comparing the mass spectrometry information of the diluted solution and the supernatant of the sample to determine the type of light stabilizer.

[0007] The method for screening light stabilizers according to embodiments of the present invention constructs an auxiliary ionization surface for the sample powder to be tested and uses open direct mass spectrometry for detection, thereby achieving one-time screening of multiple light stabilizers in degradable plastics. The method is simple to operate, has a short analysis time, requires little or no sample pretreatment, and uses a small amount of sample. One-time analysis and detection can simultaneously achieve rapid screening and analysis of degradable plastics and multiple light stabilizers therein, with high accuracy and sensitivity and fast detection speed.

[0008] In addition, the method for screening light stabilizers according to the above embodiments of the present invention may also have the following additional technical features:

[0009] According to an embodiment of the present invention, the particle size of the sample powder to be tested is 20-200 μm.

[0010] According to an embodiment of the present invention, the mass fraction of polylactic acid in the initial solution is 0.5-10%.

[0011] According to embodiments of the present invention, the first solvent and the second solvent are independently selected from acetone, acetonitrile, benzene, chloroform, m-cresol, dimethylformamide, dimethyl sulfoxide, 1-4 dioxane, 1-3 dioxane, ethyl acetate, furan, hexafluoroisopropanol, isoamyl alcohol, dichloromethane, methyl ethyl ketone, n-methyl oxalone, pyridine, tetrahydrofuran, toluene, or xylene, preferably chloroform.

[0012] According to an embodiment of the present invention, the first solvent and the second solvent are the same.

[0013] According to embodiments of the present invention, the non-solvent is selected from isopropyl ether, cyclohexane, hexane, ethanol, methanol, water, and diethyl ether, preferably methanol.

[0014] According to an embodiment of the present invention, the second solution and the non-solvent are mixed in the same proportion with the initial solution.

[0015] According to an embodiment of the present invention, the auxiliary ionization surface construction matrix is ​​a solution containing graphene oxide.

[0016] According to an embodiment of the present invention, the concentration of the graphene oxide solution for constructing the auxiliary ionization surface matrix is ​​4 mg / mL.

[0017] According to an embodiment of the present invention, the operating parameters of the open mass spectrometry detection are: a focused laser with a pulse width of 5-10 ns; the operating parameters of the focused laser are: frequency 950-1050 Hz, laser intensity 18-42.0, laser number 100-1000; minimum laser spot diameter: not greater than 5 μm.

[0018] According to an embodiment of the present invention, the detection conditions for the open-type mass spectrometry detection are as follows: ion mode: positive ion mode; mass range: m / z 200-1000 Da; sample voltage: 3-4 kV; detector voltage: 1.80-2.00 kV.

[0019] According to an embodiment of the present invention, the analysis and comparison includes: calculating the intrinsic proportion parameters of the included compounds based on the intensity information of each mass spectrometry peak of the diluted solution and the supernatant; dividing the intrinsic parameter range of the light stabilizer compounds based on the different intrinsic parameter proportions of different types of compounds; comparing the characteristic peaks belonging to the intrinsic parameter range of the light stabilizer compounds with the light stabilizer compound spectral database to confirm the type of the light stabilizer compound.

[0020] According to an embodiment of the present invention, the method further includes: constructing a standard curve for each of the light stabilizer compounds based on the confirmed types of the light stabilizer compounds; and obtaining the content of each of the light stabilizer compounds based on the standard curves of the light stabilizer compounds.

[0021] According to an embodiment of the present invention, the sample to be tested is a biodegradable plastic.

[0022] According to another aspect of the present invention, a kit for screening light stabilizers is provided. Embodiments of the present invention include reagents, standards, auxiliary materials, or combinations thereof used in the aforementioned methods for screening light stabilizers.

[0023] According to the kit of the present invention, by constructing an auxiliary ionization surface for the sample powder to be tested and using open direct mass spectrometry for detection, multiple light stabilizers in degradable plastics can be screened in one step. The detection process is simple, the analysis time is short, no or very little sample pretreatment is required, and the sample volume is small. It realizes rapid screening and analysis of degradable plastics and multiple light stabilizers therein, with high accuracy and sensitivity and fast detection speed.

[0024] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0025] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0026] Figure 1 A schematic flowchart of a method for constructing an assisted ionization surface according to an embodiment of the present invention is shown;

[0027] Figure 2 This diagram illustrates the optimized results of non-solvent addition volume and type conditions according to an embodiment of the present invention.

[0028] Figure 3 A schematic diagram showing the optimized sample preparation concentration conditions according to an embodiment of the present invention is displayed;

[0029] Figure 4 The auxiliary surface mass spectrum (blank mass spectrum), sedimentation sample spectrum and diluted sample spectrum of PLA with 1% light stabilizer UV234 added according to an embodiment of the present invention are shown.

[0030] Figure 5 The image shows the feature component extraction diagram after algorithm processing according to an embodiment of the present invention (PLA with 1% light stabilizer UV234 added);

[0031] Figure 6 The following are displayed: a database spectrum and a secondary mass spectrum of the light stabilizer UV234 according to an embodiment of the present invention;

[0032] Figure 7 The quantitative curve of the UV234 light stabilizer standard according to an embodiment of the present invention is shown;

[0033] Figure 8 The database spectra of some light stabilizers (71, 326, 327, 328, 329) according to an embodiment of the present invention are shown;

[0034] Figure 9 The database search results are shown in the presence of a mixed light stabilizer according to an embodiment of the present invention.

[0035] Figure 10 The accompanying mass spectra show a comparison of the performance of different matrices (GO, CHCA, DHB) in analyzing UV234 (500 ppm) according to an embodiment of the present invention. Detailed Implementation

[0036] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0037] In the description of this invention, the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and do not require that this invention must be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0038] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0039] According to one aspect of the present invention, a method for screening light stabilizers is provided. The method for screening light stabilizers according to embodiments of the present invention involves constructing an auxiliary ionization surface for the sample powder to be tested, and then using open direct mass spectrometry for detection. This allows for the simultaneous screening of multiple light stabilizers in degradable plastics. The method is simple to operate, has a short analysis time, requires little or no sample pretreatment, and uses a small sample volume. The single-analysis detection can simultaneously achieve rapid screening analysis of degradable plastics and multiple light stabilizers therein, with high accuracy and sensitivity, and fast detection speed.

[0040] To facilitate understanding of the method for screening light stabilizers according to embodiments of the present invention, the method is explained and described according to embodiments of the present invention, which includes:

[0041] S100 initial dissolution

[0042] According to an embodiment of the present invention, the sample powder to be tested is initially dissolved using a first solvent to obtain an initial solution. This initial dissolution facilitates subsequent dilution and sedimentation processes.

[0043] According to embodiments of the present invention, prior to initial dissolution, the sample to be tested is further pulverized. According to embodiments of the present invention, depending on the properties of the sample and the requirements of the grinder, it may be necessary to cut the sample into small pieces or powder. The sample to be tested is pre-cooled in a freezer or liquid nitrogen to lower its temperature; the cooled sample is then placed in a grinding jar; the lid of the grinding jar is ensured to be tightly sealed to prevent sample splashing during grinding. The operating parameters of the grinder are set according to the properties of the sample and the desired grinding effect, and the sample is ground.

[0044] According to an embodiment of the present invention, the cryo-milling conditions are 10-30 Hz for 1-2 min. This results in sample particles of uniform size and suitable uniformity, facilitating further dissolution, and the freezing conditions reduce the thermal decomposition of the light stabilizer during the milling process.

[0045] According to an embodiment of the present invention, the particle size of the sample powder to be tested is 20-200 μm. This results in a high dissolution rate of the pulverized sample, promoting the release of the light stabilizer from the polymer.

[0046] According to an embodiment of the present invention, the mass fraction of polylactic acid in the initial solution is 0.5-10%. This wide mass fraction range effectively prevents dilution of the light stabilizer, improves analytical results, and within this range, the sedimentation effect is visible to the naked eye, facilitating rapid determination of the timing for the next processing step.

[0047] According to an embodiment of the present invention, the sample to be tested is a biodegradable plastic. Biodegradable plastic products are commonly used in disposable lunch boxes, straws, and other tableware. Contact with food may lead to the migration of light stabilizers into the food. Therefore, rapid detection of additives, especially light stabilizers, in biodegradable plastic products is necessary.

[0048] According to an embodiment of the present invention, the light stabilizer is a light-stabilizing functional additive that can be used to degrade plastics.

[0049] According to embodiments of the present invention, the light stabilizer is UV-71, UV-234, UV-326, UV-327, UV-328, or UV-329. Therefore, the method of the present invention can be used for the routine detection of light stabilizers.

[0050] S200 dilution treatment

[0051] According to an embodiment of the present invention, the initial solution is diluted with a second solvent to obtain a diluted solution.

[0052] According to embodiments of the present invention, the first solvent and the second solvent are independently selected from acetone, acetonitrile, benzene, chloroform, m-cresol, dimethylformamide, dimethyl sulfoxide, 1,4-dioxane, 1,3-dioxane, ethyl acetate, furan, hexafluoroisopropanol, isoamyl alcohol, dichloromethane, methyl ethyl ketone, n-methyloxoformone, pyridine, tetrahydrofuran, toluene, or xylene, preferably chloroform. This results in good solubility of the light stabilizer; PLA has higher solubility in chloroform, and the properties of chloroform differ significantly from those of non-solvents, leading to a noticeable sedimentation effect.

[0053] According to an embodiment of the present invention, the first solvent and the second solvent are the same. This avoids introducing interference from other reagents.

[0054] S300 initial dissolution

[0055] According to an embodiment of the present invention, the initial solution is mixed with a non-solvent and subjected to sedimentation treatment to precipitate the polymeric compounds, thereby obtaining a precipitate. Thus, by using a non-solvent to precipitate the polymeric compounds, the supernatant retains small-molecule light stabilizers, eliminating the influence of the polymeric compounds on subsequent detection.

[0056] As used in this invention, the term "polymer" refers to a large molecule composed of a large number of repeating structural units (called "monomers") linked by covalent bonds, typically with a molecular weight exceeding 10. 4 g·mol⁻¹, and even up to millions.

[0057] According to embodiments of the present invention, the non-solvent is selected from isopropyl ether, cyclohexane, hexane, ethanol, methanol, water, and diethyl ether, preferably methanol. This results in good sedimentation, with methanol being particularly effective. Methanol and chloroform have significantly different solubility properties for PLA, leading to a noticeable sedimentation effect, requiring a smaller volume of solvent, significantly reducing the dilution of the tested light stabilizer, and improving detection results.

[0058] According to an embodiment of the present invention, the second solution and the non-solvent are mixed in the same proportion with the initial solution. This facilitates subsequent analysis and calculations.

[0059] S400 centrifugal treatment

[0060] According to an embodiment of the present invention, the sediment is centrifuged to obtain a supernatant. This centrifugation process removes polymer molecules.

[0061] S500 mass spectrometry detection

[0062] refer to Figure 1According to an embodiment of the present invention, the diluted solution and the supernatant are dropped onto a carrier plate with an auxiliary ionization surface construction matrix, and open-type mass spectrometry is performed to obtain the mass spectrometry information of the sample to be tested.

[0063] According to embodiments of the present invention, the auxiliary ionization surface construction matrix is ​​a solution containing graphene oxide. Therefore, using monolayer graphene oxide as the auxiliary ionization matrix can significantly reduce complex background interference peaks. In some embodiments, the ionization signal intensity of the target antioxidant is tens of times higher than that of conventional matrices. According to embodiments of the present invention, the concentration of the graphene oxide solution in the auxiliary ionization surface construction matrix is ​​4 mg / mL. Therefore, at this concentration, the graphene oxide solution has good dispersibility and can form a uniform and smooth auxiliary ionization surface.

[0064] According to an embodiment of the present invention, the operating parameters of the open-type mass spectrometry detection are: a focused laser with a pulse width of 5-10 ns; the operating parameters of the focused laser are: frequency 950-1050 Hz, laser intensity 18-42.0, laser number 100-1000; minimum laser spot diameter: not greater than 5 μm. Therefore, the mass spectrometry detection of light stabilizers has high sensitivity and accuracy.

[0065] According to an embodiment of the present invention, the detection conditions for the open-type mass spectrometry detection are as follows: ion mode: positive ion mode; mass range: m / z 200-1000 Da; sample voltage: 3-4 kV; detector voltage: 1.80-2.00 kV. Therefore, the mass spectrometry detection of light stabilizers exhibits high sensitivity and accuracy.

[0066] S600 Analysis and Comparison

[0067] According to an embodiment of the present invention, the mass spectrometry information of the test sample in the diluted solution and the supernatant is analyzed and compared to obtain the type of light stabilizer.

[0068] According to an embodiment of the present invention, the analysis and comparison includes: calculating the intrinsic proportion parameters of the included compounds based on the intensity information corresponding to each mass spectrometry peak of the diluted solution and the supernatant; classifying the intrinsic parameter range of the light stabilizer compounds based on the different intrinsic parameter proportions of different types of compounds; comparing the characteristic peaks belonging to the intrinsic parameter range of the light stabilizer compounds with the light stabilizer compound spectral database to confirm the type of the light stabilizer compound. In other words, the algorithm compares the two spectra of the diluted solution and the supernatant to extract the characteristic peaks of potential light stabilizers, and the characteristic peaks with similar intrinsic proportion parameters of compounds are assigned to the same type of substance. Specifically, in one embodiment, different types of substances have different intrinsic proportions: the intrinsic proportion parameter of graphene oxide is 0 to 1, the intrinsic proportion parameter of PLA is -3.0 to -1.0, and the intrinsic proportion parameter of UV234 is -1.0 to -0.5. The mass spectrometry peaks with intrinsic proportion parameters of -1.0 to -0.5 are extracted to construct the UV234 characteristic peak spectrum, as shown below. Figure 5 As shown. Therefore, the spectrum of the light stabilizer is obtained through the intrinsic proportioning parameter range, and the type of light stabilizer is identified by comparing the spectrum with a compound database.

[0069] According to an embodiment of the present invention, the method further includes: constructing a standard curve for each of the light stabilizer compounds based on the confirmed types of the light stabilizer compounds; and obtaining the content of each of the light stabilizer compounds based on the standard curves of the light stabilizer compounds.

[0070] According to another aspect of the present invention, a kit for screening light stabilizers is provided. Embodiments of the present invention include reagents, standards, auxiliary materials, or combinations thereof used in the aforementioned methods for screening light stabilizers.

[0071] According to the kit of the present invention, by constructing an auxiliary ionization surface for the sample powder to be tested and using open direct mass spectrometry for detection, multiple light stabilizers in degradable plastics can be screened in one step. The detection process is simple, the analysis time is short, no or very little sample pretreatment is required, and the sample volume is small. It realizes rapid screening and analysis of degradable plastics and multiple light stabilizers therein, with high accuracy and sensitivity and fast detection speed.

[0072] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and should not be construed as limiting the present invention.

[0073] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products, such as those purchased from Sigma.

[0074] The equipment and materials used in the embodiments of this specification are as follows:

[0075] 1. The aforementioned equipment:

[0076] Mass spectrometry microscope (iMScope TRIO, Shimadzu Corporation, Japan);

[0077] Cryomill (Retsch CryoMill, Germany);

[0078] AG-204 electronic analytical balance (Mettler Toledo, Switzerland).

[0079] 2. The materials mentioned:

[0080] Light stabilizers UV-71, CAS No. 2440-22-4, UV-234, CAS No. 70321-86-7, UV-326, CAS No. 3896-11-5, UV-327, CAS No. 3846-99-1, UV-328, CAS No. 25973-55-1, UV-329, CAS No. 3147-75-9 were purchased from Tokyo Chemical Industry (TCI Shanghai, China). Polylactic acid (PLA, Mw~60,000, powder) and graphene oxide aqueous dispersion (4 mg / mL) were purchased from Sigma-Aldrich (MO St. Louis, USA). HPLC-grade chloroform (CHCl3), methanol (MeOH), and acetonitrile (ACN) were purchased from Merck (Darmstadt, Germany). Deionized water was produced by a Millipore water purification system (Millipore Corporation, Billerica, MA). The indium tin oxide (ITO) coating target (75mm × 25mm, surface resistivity 8-12 Ω / sq) was purchased from Sigma-Aldrich (MO St. Louis, USA).

[0081] Example 1: Settlement Condition Optimization

[0082] In this embodiment, the initial PLA (polylactic acid) concentration and the dilution and sedimentation parameters of solvent and non-solvent are optimized as follows:

[0083] 1. Prepare a 5wt% fixed concentration PLA (polylactic acid) solution using chloroform as the solvent and water, methanol, and ethanol as non-solvents. Varying the solvent / non-solvent ratio (from 100:0 to 0:100) to induce precipitation. Each sample should be thoroughly stirred to dissolve and allowed to equilibrate at a constant temperature (e.g., 25°C). Slowly add the non-solvent to the polymer / solvent solution until the first turbidity appears. Record the solvent / non-solvent ratio at this point as the cloud point.

[0084] The three solvent / non-solvent groups were: chloroform / water, chloroform / methanol, and chloroform / ethanol. The results were plotted on [date missing]. Figure 2 As shown in the figure, methanol and chloroform have significantly different solubility properties for PLA, resulting in a noticeable sedimentation effect. Methanol requires the smallest volume of methanol, reducing the dilution of the tested light stabilizer and improving detection efficiency. If ethanol is used, 2.5 times its volume of ethanol is needed as a non-solvent to induce sedimentation, diluting the light stabilizer and increasing the difficulty of detection. While 0.5 times its volume of water can induce sedimentation as a non-solvent, water and chloroform are immiscible, increasing the difficulty of subsequent quantitative analysis. Therefore, 1.5 times its volume of methanol is used as the non-solvent.

[0085] 2. Prepare a series of PLA solutions with fixed concentrations (2–10 wt%). Slowly add 1.5 times the volume of methanol (non-solvent) to the polymer / solvent solution. Each sample must be thoroughly stirred and dissolved, and then allowed to stand at a constant temperature (e.g., 25°C) for equilibration. Sedimentation will occur in all cases. The results are plotted on [Diagram showing results]. Figure 3 As shown in the figure, the viscosity of PLA with an initial volume of 2wt% is moderate, which facilitates quantitative volume transfer and reduces the contamination of the instrument by high PLA content. Therefore, subsequent experiments used PLA with an initial volume of 2wt% as the sample preparation condition.

[0086] Example 2: Auxiliary screening of quality

[0087] The analytical effectiveness of additives in degradable plastics is highly dependent on the choice of auxiliary matrix. A potential matrix compound should meet specific conditions, including high absorption at the laser wavelength, minimum background signal of the matrix peaks and their clusters, ability to form co-crystallization with the analyte, and effective ionization of the target analyte. This example compares the signal intensity of the light stabilizer UV234 (500 ppm) on different matrices to screen suitable open-beam mass spectrometry auxiliary matrices for light stabilizers in degradable plastics, as detailed below:

[0088] 1. Weigh an appropriate amount of CHCA (α-cyano-4-hydroxycinnamic acid) matrix and dissolve it in methanol to prepare a matrix solution with a concentration of 20 mg / mL.

[0089] 2. Weigh an appropriate amount of DHB (2,5-dihydroxybenzoic acid) and dissolve it in acetonitrile to prepare a matrix solution with a concentration of 20 mg / mL.

[0090] 3. Matrix solution 1 and matrix solution 2 are respectively mixed with an equal volume of light stabilizer UV234 (500 ppm) solution;

[0091] 4. Weigh an appropriate amount of graphene oxide (GO) powder and prepare a matrix solution with a concentration of 4 mg / mL using water. Construct an ionized surface using the method described above.

[0092] 5. Using the droplet drying method, drop the prepared CHCA / UV234 and DHB / UV234 mixed solutions (0.5 μL) onto the target plate respectively.

[0093] 6. 0.5 μL of the light stabilizer UV234 was dropped onto an auxiliary ionization surface target plate. Mass spectrometry was performed using an iMScope TRIO microscope in open mode with the following conditions: positive ion mode; mass range: m / z 200-1000 Da; sample voltage: 3.5 kV; detector voltage: 1.90 kV. The mass spectrometry results under positive ionization mode are shown below. Figure 10 As shown. Figure 10 Mass spectra of the light stabilizer UV234 in GO, CHCA, and DHB matrices are presented (from top to bottom). While UV234 was detectable in all three matrices, the GO spectrum was simpler, exhibiting signal intensities approximately tens of times higher than the other two matrices. Furthermore, no characteristic spectra were obtained for the other light stabilizers, DHB and CHCA. These results demonstrate that the GO matrix can provide highly sensitive analysis of light stabilizers and is suitable as an open-type mass spectrometry-assisted ionization surface for light stabilizers in degradable plastics.

[0094] Example 3: Analysis of Test Samples

[0095] In this embodiment, the method for screening light stabilizers according to the present invention is used to detect polylactic acid containing a specified concentration of the light stabilizer UV-234, as follows:

[0096] 1. Prepare polylactic acid (PLA) with a specified concentration of the light stabilizer UV-234 as a standard sample for method validation. Mix 990 mg of PLA powder with 10 mg of the light stabilizer UV-234 to prepare a standard PLA sample with a UV-234 mass fraction of 1%. Dissolve a small amount of the mixed powder in chloroform in a glass vial until a uniform paste is formed. After sonicating for 5 minutes, fill the paste into a 10 mm × 10 mm aluminum foil mold and place it in a fume hood at room temperature until the solvent evaporates. Pulverize the standard sample at low temperature, weigh 10 mg of the standard sample, dissolve it in chloroform, and sonicate to prepare a 2% mass fraction actual sample solution.

[0097] Take 500 μL of UV-234 standard sample solution, slowly add 750 μL of methanol (a non-solvent), let stand until the plastic polymer precipitates, take the supernatant, centrifuge and take the supernatant to obtain the sedimented sample solution (S1), to be tested; take another 500 μL of UV-234 standard sample solution, add 750 μL of chloroform to obtain the diluted sample solution (S2), to be tested.

[0098] 1000 µL of graphene oxide solution (4 mg / mL) was added to the cavity of a manual spray gun (MR. LinearCompressor L7 / PS270 Airbrush, Tokyo, Japan). The distance between the spray gun tip and the ITO target surface was approximately 8 cm. The matrix was sprayed for 5 seconds every 60 seconds, repeated 10-15 times. The ITO target was then placed in a fume hood for 5 minutes to allow the solvent to evaporate.

[0099] Mass spectrometry analysis was performed on the samples. 0.5 μL of the precipitated sample solution and the diluted sample solution were spotted onto an ITO target plate. After the solvent evaporated, the target plate was placed in the instrument for mass spectrometry analysis. The mass spectrometry conditions were: positive ion mode; mass range: m / z 200-1000 Da; sample voltage: 3.5 kV; detector voltage: 1.90 kV. Mass spectra of the precipitated sample and the diluted sample were obtained, and the results are as follows: Figure 4 As shown, the top image is the mass spectrum of the sample without any added sample, the middle image is the mass spectrum of the settled sample, and the bottom image is the mass spectrum of the diluted sample.

[0100] The algorithm compares the intrinsic proportion parameters of compounds. Compounds with the same intrinsic proportion parameters are assigned to the same class of substances, and the original spectrum (…) Figure 5 (Top left) Analysis results are as follows Figure 5 As shown. In the test spectra described in the experimental example, the intrinsic proportion parameter of graphene oxide is 0 to 1, the intrinsic proportion parameter of PLA is -3.0 to -1.0, and the intrinsic proportion parameter of UV234 is -1.0 to -0.5. Figure 5(See the three figures on the right). Mass spectrometry peaks with intrinsic proportion parameters of -1.0 to -0.5 were extracted to construct the characteristic peak spectrum of UV234. The UV234 characteristic peak spectrum was compared with the UV234 spectrum in the database. Figure 5 (Bottom left) Comparison confirms the presence of UV234 in the sample.

[0101] Example 4: Analysis of UV234 Standard

[0102] In this embodiment, the UV234 standard was analyzed, as follows:

[0103] 1. Accurately weigh the solid UV234 standard, dissolve it in ACN, and prepare a standard solution with a concentration of 1 mg / mL. Dilute to the required concentration before use.

[0104] 2. Construction of the auxiliary ionization surface: 500 µL of graphene oxide solution (4 mg / mL) was pipetted into the cavity of a manual spray gun (MR. Linear Compressor L7 / PS270 Airbrush, Tokyo, Japan); the distance between the spray gun tip and the target surface was approximately 8 cm; in the first 3 cycles, the matrix was sprayed for 10 s every 60 s, and in the subsequent 7 cycles, the matrix was sprayed continuously for 10 s every 30 s; after spraying, a uniform auxiliary ionization surface was formed on the sample slice surface. Finally, the slide was placed in a fume hood for 5 minutes to allow the solvent to evaporate.

[0105] 3. UV234 standard (100 ppm) was added dropwise to the GO-assisted ionization surface, the solvent was evaporated, and the standard spectrum was obtained by instrumental analysis, such as... Figure 6 As shown in the left figure, further secondary mass spectrometry data were acquired for the characteristic peak of UV234 (m / z=486), as follows: Figure 6 As shown in the figure on the right.

[0106] 4. By adding UV234 standards of different concentrations (1-100 ppm) to the GO-assisted ionization surface, evaporating the solvent, and analyzing the surface with instruments, a semi-quantitative dynamic range curve was obtained. Linear regression was performed between the standard concentration per unit area and the corresponding intensity. Each calibration point was repeated three times. The UV234 content in the sample could be determined using the average ionic intensity in the actual sample and the linear regression equation. The results are as follows: Figure 7 As shown.

[0107] Example 5: Construction of a Partial Light Stabilizer Spectral Database

[0108] In this embodiment, a database of spectra for UV71, UV326, UV327, UV328, and UV329 standards is constructed, as detailed below:

[0109] 1. Accurately weigh the solids of UV71, UV326, UV327, UV328, and UV329, dissolve them in ACN, and prepare a standard solution with a concentration of 1 mg / mL. Dilute to the required concentration before use.

[0110] 2. Construction of the auxiliary ionization surface: 500 µL of graphene oxide solution (4 mg / mL) was pipetted into the cavity of a manual spray gun (MR. Linear Compressor L7 / PS270 Airbrush, Tokyo, Japan); the distance between the spray gun tip and the target surface was approximately 8 cm; in the first 3 cycles, the matrix was sprayed for 10 s every 60 s, and in the subsequent 7 cycles, the matrix was sprayed continuously for 10 s every 30 s; after spraying, a uniform auxiliary ionization surface was formed on the sample slice surface. Finally, the slide was placed in a fume hood for 5 minutes to allow the solvent to evaporate.

[0111] 3. By adding each UV standard (50 ppm) dropwise to the GO-assisted ionization surface, evaporating the solvent, and then analyzing the standard database spectrum using instruments, such as... Figure 8 As shown.

[0112] Example 6: Comparison of Spectral Databases of Mixed Light Stabilizers

[0113] 10 mg of light stabilizer UV-71, 10 mg of light stabilizer UV-234, and 10 mg of light stabilizer UV-327 were uniformly mixed and dissolved in ACN to prepare a solution with a final concentration of 100 ppm for each standard. 1000 µL of graphene oxide solution (4 mg / mL) was added to the cavity of a manual spray gun (MR. Linear Compressor L7 / PS270 Airbrush, Tokyo, Japan). The distance between the spray gun tip and the surface of the ITO target plate was approximately 8 cm. The matrix was sprayed for 5 seconds every 60 seconds, for a cycle of 10-15 times. The ITO target plate was placed in a fume hood for 5 minutes to allow the solvent to evaporate.

[0114] The mass spectrometry analysis method described in Example 3 was used for detection. 0.5 μL of the actual sample solution was spotted onto an ITO target plate, and the solvent was allowed to evaporate. The target plate was then placed in the instrument for mass spectrometry analysis. The mass spectrometry conditions were: positive ion mode; mass range: m / z 200-1000 Da; sample voltage: 3.5 kV; detector voltage: 1.90 kV. The mixed mass spectrum is shown below. Figure 9 As shown above.

[0115] Importing the mixed mass spectrum into the database for retrieval revealed three light stabilizers, as shown in the following results. Figure 9As shown below, UV234 scored 0.968, UV71 scored 0.921, and UV327 scored 0.840.

[0116] The results show that the spectra of mixed light stabilizers can be analyzed one by one through database comparison. This demonstrates that the method for screening light stabilizers using the embodiments of the present invention can rapidly screen for light stabilizers in the test samples, and the screening speed is fast and the accuracy is high.

[0117] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0118] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for screening light stabilizers, characterized in that, include: The sample powder to be tested is initially dissolved using a first solvent to obtain an initial solution; The initial solution is diluted with a second solvent to obtain a diluted solution; The initial solution is mixed with a non-solvent and subjected to sedimentation treatment to precipitate the polymer compounds, thereby obtaining a sediment. The sediment is centrifuged to obtain a supernatant; The diluted solution and the supernatant were dropped onto a carrier plate with an auxiliary ionization surface construction matrix, and open-type mass spectrometry was performed to obtain the mass spectrometry information of the sample to be tested. as well as The mass spectrometry information of the test sample in the diluted solution and the supernatant is analyzed and compared to obtain the type of light stabilizer.

2. The method according to claim 1, characterized in that, The particle size of the sample powder to be tested is 20-200 μm.

3. The method according to claim 1, characterized in that, The mass fraction of polylactic acid in the initial solution is 0.5-10%.

4. The method according to claim 1, characterized in that, The first solvent and the second solvent are each independently selected from acetone, acetonitrile, benzene, chloroform, m-cresol, dimethylformamide, dimethyl sulfoxide, 1,4-dioxane, 1,3-dioxane, ethyl acetate, furan, hexafluoroisopropanol, isoamyl alcohol, dichloromethane, methyl ethyl ketone, n-methyl benzophenone, pyridine, tetrahydrofuran, toluene, or xylene, preferably chloroform. Optionally, the first solvent and the second solvent are the same. Optionally, the non-solvent is selected from isopropyl ether, cyclohexane, hexane, ethanol, methanol, water, and diethyl ether, preferably methanol.

5. The method according to claim 1, characterized in that, The second solution and the non-solvent are mixed in the same proportion as the initial solution.

6. The method according to claim 1, characterized in that, The matrix for constructing the auxiliary ionization surface is a solution containing graphene oxide. Optionally, the concentration of the graphene oxide solution for constructing the auxiliary ionization surface matrix is ​​4 mg / mL.

7. The method according to claim 1, characterized in that, The operating parameters for the open-type mass spectrometry detection are as follows: Focused laser with a pulse width of 5-10 ns; The operating parameters of the focused laser are: frequency 950-1050 Hz, laser intensity 18-42.0, and laser number 100-1000. Minimum laser spot diameter: no more than 5 μm. Optionally, the detection conditions for the open-type mass spectrometry detection are as follows: Ion mode: Positive ion mode; Quality range: m / z 200-1000 Da; Sample voltage: 3-4 kV; Detector voltage: 1.80-2.00 kV.

8. The method according to claim 1, characterized in that, The analysis and comparison include: Based on the intensity information of each mass spectrometry peak in the diluted solution and the supernatant, the intrinsic proportion parameters of the contained compounds are calculated. The intrinsic parameter ranges of light stabilizer compounds are defined based on the different proportions of intrinsic parameters of different types of compounds. The characteristic peaks belonging to the intrinsic parameter range of the light stabilizer compound are compared with the light stabilizer compound spectral database to confirm the type of the light stabilizer compound.

9. The method according to claim 1, characterized in that, Further includes: Based on the confirmed types of light stabilizer compounds, standard curves for each light stabilizer compound were constructed. Based on the standard curve of the light stabilizer compounds, the content of each light stabilizer compound is obtained. Optionally, the sample to be tested is a biodegradable plastic.

10. A kit for screening light stabilizers, characterized in that, Includes the reagents, standards, auxiliary materials, or combinations thereof used in the method for screening light stabilizers according to any one of claims 1-9.

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