Direct mass spectrometric detection method for degrading antioxidant in plastic and kit thereof

Abstract

The invention discloses a direct mass spectrometric detection method for an antioxidant in degradable plastics and a kit thereof.The method for detecting the antioxidant in the degradable plastics comprises the steps that a to-be-detected sample is smashed so as to obtain sample powder; mixing the sample powder with a solvent to obtain a solution containing the sample powder; mixing the solution with an auxiliary ionization matrix to obtain a mixed solution; and carrying out open-type mass spectrometric detection on the mixed solution so as to qualitatively / quantitatively detect the antioxidant. According to the method, a to-be-detected sample is crushed and dissolved, is mixed with a matrix, and is directly detected by using an open-type mass spectrum, so that the method is simple to operate, short in analysis time, does not need or only needs very little pretreatment, can be used for detection only by using a trace sample, is low in sample loss, realizes simultaneous qualitative and quantitative analysis of multiple antioxidants in degradable plastics, and has good application prospects. The detection speed, the sensitivity and the accuracy are high.

Description

Technical Field

[0001] The invention relates to the field of analytical chemistry, in particular to a direct mass spectrometry detection method for antioxidants in degraded plastics and a kit thereof. Background Art

[0002] The application of biodegradable plastic materials in various fields is constantly expanding. The types of additives used to modify the properties of polymers are also growing proportionally. Adding 0.05% w Up to 3% w Antioxidants are added to prevent polymer degradation due to oxidation. This helps to extend the service life of the plastic and maintain its physical properties. The exact amount of antioxidant added depends on the type of plastic, the intended use environment and the desired performance characteristics. The degradation process can reduce the physical properties of the plastic and cause the release of additives into the environment, causing environmental pollution and health risks. It is often difficult to find information about the additive content on the label of the final plastic product. Testing antioxidants in degradable plastics is essential to ensure the safety and compliance of plastic products.

[0003] Traditional methods for analyzing additives in biodegradable plastics are time-consuming, especially when it comes to detecting the content of migratable substances in food packaging materials. They usually involve sample extraction, followed by chromatographic analysis (such as gas chromatography or liquid chromatography), and then detection using mass spectrometry or UV / visible spectroscopy. In addition, the pretreatment process is easily interfered by environmental pollutants. Pyrolysis-gas chromatography / mass spectrometry (Py-GC / MS) is suitable for the identification and semi-quantitative analysis of organic plastic additives (OPAs), with the advantages of reducing sample preparation steps and minimizing contamination, but the high-temperature pretreatment process may destroy the compounds to be analyzed, and the analytical equipment is expensive. Commonly used spectroscopic methods such as Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy can quickly screen additives in plastics within a few minutes. However, due to strong interference with background signals and subtle spectral differences in additives, spectroscopic methods are difficult to reliably identify mixed additives and perform quantitative analysis of additives.

[0004] Therefore, the detection method of antioxidants in degradable plastics based on on-site analysis still needs to be improved. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one object of the present invention is to provide a method for detecting antioxidants in degradable plastics, which realizes a one-time analysis of multiple antioxidants in degradable plastics, with a short analysis time and a fast detection speed.

[0006] According to one aspect of the present invention, the present invention provides a method for detecting antioxidants in degradable plastics. According to an embodiment of the present invention, the method comprises: pulverizing a sample to be tested to obtain a sample powder; mixing the sample powder with a solvent to obtain a solution containing the sample powder; mixing the solution with an auxiliary ionization matrix to obtain a mixed solution; and performing open mass spectrometry detection on the mixed solution to obtain a qualitative detection of the antioxidant.

[0007] According to the method for detecting antioxidants in degradable plastics according to an embodiment of the present invention, the sample to be tested is crushed, dissolved, and mixed with a matrix, and directly detected by open mass spectrometry. The operation is simple, the analysis time is short, and no or only very little pretreatment is required. Only a trace amount of sample is required for detection, and the sample loss is small. Simultaneous qualitative and quantitative analysis of multiple antioxidants in degradable plastics is achieved. In addition, the detection speed is fast and can be reduced to one tenth of the time used by existing mass spectrometry instrument methods. The sensitivity and accuracy are higher than optical spectral analysis technology.

[0008] In addition, the method for detecting antioxidants in degradable plastics according to the above embodiment of the present invention may also have the following additional technical features:

[0009] According to an embodiment of the present invention, the pulverization process is cryogenic grinding.

[0010] According to an embodiment of the present invention, the conditions of the cryogenic grinding are 20-30 Hz, 1-2 min.

[0011] According to an embodiment of the present invention, the particle size of the sample powder is 20-200 μm.

[0012] According to an embodiment of the present invention, the auxiliary ionization matrix is ​​a single layer of graphene oxide. According to an embodiment of the present invention, the single layer of graphene oxide has a thickness of 0.8-1.2 nm and a radius of less than 5 μm.

[0013] According to an embodiment of the present invention, the concentration of graphene oxide in the mixed solution is 0.5-10 mg / mL.

[0014] According to an embodiment of the present invention, the volume of the mixed solution is 2-200 μL.

[0015] According to an embodiment of the present invention, the open mass spectrometer is a time-of-flight (TOF) mass spectrometer configured with a laser source.

[0016] According to an embodiment of the present invention, the working parameters of the mass spectrometry detection are: ion source: focused laser with a pulse width of 5ns; the working parameters of the focused laser are: frequency 1000Hz, laser intensity 15-25.0, laser number 100-1000; minimum laser spot diameter: no more than 10μm.

[0017] According to an embodiment of the present invention, the mass spectrometry conditions of the mass spectrometry detection are: ion polarity: positive ion; mass range: m / z200-1000Da; sampling voltage: 3.2-3.8kV; detector voltage: 1.50-2.0kV.

[0018] According to an embodiment of the present invention, the sample to be tested is degradable plastic and its products.

[0019] According to an embodiment of the present invention, the antioxidant is an antioxidant functional additive that can be used for degrading plastics, preferably, at least one selected from antioxidant 1098, antioxidant 1520, antioxidant 1726 and antioxidant 3114.

[0020] According to another aspect of the present invention, the present invention provides a kit for detecting antioxidants in degradable plastics. According to an embodiment of the present invention, the kit includes the reagents, standard substances, auxiliary ionization matrix or a combination of at least one of the above-mentioned methods for detecting antioxidants in degradable plastics. Thus, the use of the kit to detect antioxidants in degradable plastics is simple to operate, the analysis time is short, only a trace amount of sample is required for detection, and no or only very little pretreatment is required, and the sample loss is small, thereby achieving simultaneous qualitative and quantitative analysis of multiple antioxidants in degradable plastics, and the detection speed is fast, and the sensitivity and accuracy are high.

[0021] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0023] Figure 1 A schematic flow chart of a method for detecting antioxidants in degradable plastics according to one embodiment of the present invention is shown;

[0024] Figure 2 The background mass spectra of auxiliary matrices DHB, CHCA, and GO according to one embodiment of the present invention are shown, which are DHB, CHCA, and GO from top to bottom;

[0025] Figure 3 The mass spectra of PLA under the action of DHB, CHCA, and GO matrices according to one embodiment of the present invention are shown, which are DHB, CHCA, and GO from top to bottom;

[0026] Figure 4The mass spectra of the antioxidant 1098 according to one embodiment of the present invention under the action of DHB, CHCA, and GO matrices are shown, which are DHB, CHCA, and GO from top to bottom;

[0027] Figure 5 A schematic diagram showing the comparison results of the auxiliary matrix dispersant according to one embodiment of the present invention, wherein the solvents from left to right are water, ethanol, and acetonitrile;

[0028] Figure 6 A schematic diagram showing the direct mass spectrometry results of antioxidants (1098, 1520, 1726 and 3114) according to one embodiment of the present invention is shown;

[0029] Figure 7 A schematic diagram of the quantitative curve results of antioxidants (1098, 1520, 1726 and 3114) according to an embodiment of the present invention is shown;

[0030] Figure 8 The figure shows the result of direct mass spectrometry analysis of oxidant 1098 in polylactic acid (PLA) according to one embodiment of the present invention. DETAILED DESCRIPTION

[0031] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0032] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0033] According to one aspect of the present invention, the present invention provides a method for detecting antioxidants in degradable plastics. According to the method for detecting antioxidants in degradable plastics according to an embodiment of the present invention, by crushing and dissolving the sample to be tested and mixing it with a matrix, an open mass spectrometer is used for direct detection, which is simple to operate, short in analysis time, requires no or very little pretreatment, requires only a trace amount of sample for detection, and has little sample loss, and realizes simultaneous qualitative and quantitative analysis of multiple antioxidants in degradable plastics, and has a fast detection speed, which can be reduced to one tenth of the time used by existing mass spectrometry instrument methods, and has higher sensitivity and accuracy than optical spectroscopy analysis technology.

[0034] In order to facilitate understanding of the method for detecting antioxidants in degradable plastics according to the embodiment of the present invention, refer to Figure 1 According to an embodiment of the present invention, the method is explained and described, and the method includes:

[0035] S100 crushing process

[0036] According to an embodiment of the present invention, the sample to be tested is crushed to obtain sample powder, thereby pulverizing the sample to be tested into powder, which facilitates subsequent analysis and detection, and improves the convenience and reliability of detection.

[0037] It should be noted that the method of pulverization can be selected according to the sample to be tested, experimental conditions, and the type of antioxidant to be tested. According to an embodiment of the present invention, the pulverization is cryogenic grinding. Specifically, the operation method of cryogenic grinding includes: placing the sample in a freezer or liquid nitrogen for precooling to reduce the temperature of the sample; placing the cooled sample in a grinding jar, ensuring that the lid of the grinding jar is well sealed to prevent the sample from splashing during the grinding process; setting the operating parameters of the grinder according to the properties of the sample and the desired grinding effect, and grinding the sample. Thus, low temperature can improve the sample pulverization effect.

[0038] According to an embodiment of the present invention, the conditions of the cryogenic grinding are 20-30 Hz, 1-2 min, preferably 1 min. Thus, the particle size of the sample obtained by grinding is suitable.

[0039] According to an embodiment of the present invention, the particle size of the sample powder is 20-200 μm. Therefore, this particle size range can accelerate sample dissolution and improve the dispersion effect of the suspension.

[0040] S200 First Hybrid

[0041] According to an embodiment of the present invention, the sample powder is mixed with a solvent to obtain a solution containing the sample powder, thereby facilitating subsequent quantitative dilution and mixing.

[0042] According to an embodiment of the present invention, the solvent is chloroform (CHCl3), which is conducive to complete dissolution of the sample powder.

[0043] S300 Second Hybrid

[0044] According to an embodiment of the present invention, the suspension (solution) is mixed with an auxiliary ionization matrix to obtain a mixed solution, whereby the auxiliary ionization matrix can form co-crystals with the antioxidant and effectively ionize the target substance.

[0045] According to an embodiment of the present invention, the auxiliary ionization matrix is ​​a monolayer graphene oxide. Thus, using a monolayer graphene oxide as an auxiliary ionization matrix can significantly reduce complex background interference peaks. In some embodiments, the ionization signal intensity of the target antioxidant is several dozen times higher than that of the traditional matrix (e.g. Figure 4 shown).

[0046] According to an embodiment of the present invention, the thickness of the single-layer graphene oxide is 0.8-1.2 nm, and the radius is less than 5 μm. Thus, the graphene can form uniform crystallized sample points with the sample.

[0047] According to an embodiment of the present invention, the concentration of graphene oxide in the mixed solution is 0.5-10 mg / mL. Therefore, graphene oxide at this concentration can fully ionize the target compound and produce less background interference peaks.

[0048] According to an embodiment of the present invention, the volume of the mixed solution is 2-200 μL, so that the volume is suitable for the requirements of open mass spectrometry detection.

[0049] S400 Mass Spectrometry

[0050] According to an embodiment of the present invention, the mixed solution is subjected to open mass spectrometry detection to obtain a qualitative detection of the antioxidant. Thus, direct detection using open mass spectrometry is simple to operate, has a short analysis time, requires little or no sample pretreatment, and uses a small amount of sample, and is suitable for antioxidant detection of crushed samples.

[0051] According to an embodiment of the present invention, the open mass spectrometer is a time-of-flight (TOF) mass spectrometer equipped with a laser source. Therefore, the mass spectrometry detection is suitable for simultaneous qualitative analysis of multiple antioxidants without the need for additional labeling, antibody reaction, staining or other complex sample pretreatment steps; and the mass spectrometry detection method can directly analyze the sample without extraction, thereby reducing the analysis time and sample usage.

[0052] According to an embodiment of the present invention, the microscope for the open mass spectrometry detection is an iMScope TRIO microscope. Thus, the microscope can be used to observe the volatilization of the solvent at the sample point before mass spectrometry analysis, thereby improving the analysis effect.

[0053] According to an embodiment of the present invention, the working parameters of the mass spectrometry detection are: ion source: focused laser with a pulse width of 5ns; the working parameters of the focused laser are: frequency 1000Hz, laser intensity 10.0-25.0, laser number 100-1000; minimum laser spot diameter: no more than 10μm. Thus, it is ensured that the target is completely ionized under different conditions and the generation of interfering background peaks is significantly reduced.

[0054] According to an embodiment of the present invention, the mass spectrometry conditions of the mass spectrometry detection are: ion polarity: positive ion; mass range: m / z200-1000Da; sampling voltage: 3.2-3.8kV; detector voltage: 1.50-2.0kV. Thus, the signal intensity is high, the impurity peaks are small, and the detection sensitivity and accuracy are high.

[0055] Since degradable plastic products are often used in disposable lunch boxes, straws and other tableware, contact with food may cause antioxidants to migrate into food, etc., and thus, rapid detection of additives in degradable plastic products, especially antioxidants, is necessary. According to an embodiment of the present invention, the sample to be tested is a degradable plastic and its products, that is, the sample to be tested is a degradable plastic or a product made of a degradable plastic.

[0056] According to an embodiment of the present invention, the antioxidant is an antioxidant functional additive that can be used for degrading plastics, preferably, at least one selected from antioxidant 1098, antioxidant 1520, antioxidant 1726 and antioxidant 3114.

[0057] According to another aspect of the present invention, the present invention provides a kit for detecting antioxidants in degradable plastics. According to an embodiment of the present invention, the kit includes the reagents, standard substances, auxiliary ionization matrix or a combination of at least one of the above-mentioned methods for detecting antioxidants in degradable plastics. Thus, the use of the kit to detect antioxidants in degradable plastics is simple to operate, the analysis time is short, only a trace amount of sample is required for detection, and no or only very little pretreatment is required, and the sample loss is small, thereby achieving simultaneous qualitative and quantitative analysis of multiple antioxidants in degradable plastics, and the detection speed is fast, and the sensitivity and accuracy are high.

[0058] The present invention is described below 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.

[0059] Below in conjunction with embodiment, the scheme of the present invention will be explained.It will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.Unrepresented specific techniques or conditions in the embodiment, according to the technology or conditions described in the document in this area or according to the product specification sheet.Reagents used or instruments that do not indicate manufacturers are conventional products that can be obtained commercially, for example, can be purchased from Sigma company.

[0060] The equipment and materials used in the examples in this specification are as follows:

[0061] 1. The equipment:

[0062] mass spectrometry microscope instrument (iMScope TRIO, Shimadzu Corporation, Japan);

[0063] cryomill (Retsch CryoMill, Germany);

[0064] AG-204 electronic analytical balance (Mettler Toledo, Switzerland).

[0065] 2. Materials:

[0066] Antioxidant 1098, CAS: 23128-74-7, purity> 98.0%, antioxidant 1520, CAS: 110553-27-0, purity> 97.0%, antioxidant 1726, CAS: 110675-26-8, purity> 95.0%, antioxidant 3114, CAS: 27676-62-6, purity> 98.0% were purchased from Tokyo Chemical Industry (TCI Shanghai, China); polylactic acid (PLA, Mw ~ 60.000, powder), graphene oxide powder was purchased from Xianfeng Nano; graphene oxide aqueous dispersion (4 mg / mL) was purchased from Sigma-Aldrich (St. Louis, MO, USA); HPLC grade chloroform (CHCl3) and acetonitrile (ACN) were purchased from Merck (Darmstadt, Germany); deionized water was provided by Milliq water purification system (Millipore Indium tin oxide (ITO) coated glass slides (size 75 mm×25 mm, surface resistivity 8-12 Ω / sq) were purchased from Sigma-Aldrich (St. Louis, MO, USA).

[0067] Example 1

[0068] The analysis of additives in degradable plastics greatly depends on the selection of auxiliary matrix. A potential matrix compound should meet specific conditions, including high absorption at the laser wavelength, the lowest background signal of the matrix peak and its cluster peak, the ability to form co-crystallization with the analyte, and effective ionization of the target. This example screened an open mass spectrometry auxiliary matrix suitable for antioxidants in degradable plastics by comparing the signal intensities of PLA and antioxidant 1098 in different matrices, as follows:

[0069] 1. Weigh an appropriate amount of CHCA (a-cyano-4-hydroxycinnamic acid) matrix and dissolve it in 70% ethanol solution containing 0.1% formic acid to prepare a matrix solution with a concentration of 10 mg / mL.

[0070] 2. Weigh an appropriate amount of DHB (2,5-dihydroxybenzoic acid) and prepare a matrix solution with a concentration of 20 mg / mL using a 70% ethanol solution containing 0.1% formic acid.

[0071] 3. Weigh an appropriate amount of graphene oxide (GO) powder and prepare a matrix solution with a concentration of 10 mg / mL with water, and ultrasonicate for 30 minutes.

[0072] 4. Use the droplet drying method to drop the prepared CHCA, DHB and GO matrix solutions (0.5 μL) onto the target plate respectively.

[0073] 5. Detection in positive ionization mode, the mass spectrometry results are as follows Figure 2-4 shown. Figure 2 The background mass spectra of DHB, CHCA, and GO are shown (from top to bottom). Figure 3 The mass spectra of PLA under the action of DHB, CHCA, and GO matrices are shown (from top to bottom). It can be seen that only GO as a matrix can obtain the characteristic peaks of PLA. Figure 3 The mass spectra of antioxidant 1098 under the action of DHB, CHCA, and GO matrices are shown (from top to bottom). While antioxidant 1098 can be detected in all three matrices, the spectrum of GO is simpler, with a signal intensity about ten times higher than that of the other two matrices, while other antioxidants DHB and CHCA cannot even obtain characteristic spectra. The above results show that GO matrix can simultaneously analyze PLA and antioxidants, and is suitable as an open mass spectrometry auxiliary matrix for antioxidants in degradable plastics.

[0074] Example 2

[0075] In this embodiment, the dispersant of the screened GO-assisted matrix is ​​selected and optimized as follows:

[0076] Deionized water, ethanol, and acetonitrile were used to dissolve GO powder into a 10 mg / mL suspension. The experimental results are shown in Figure 5 As shown in the figure, the left, middle and right parts are suspensions prepared with deionized water, ethanol and acetonitrile respectively. The results after 60 minutes of ultrasound are as follows Figure 5 As shown in a, about 1 minute later, the GO dissolved in acetonitrile began to settle in layers. Figure 5 As shown in b, Figure 5 The three suspensions in a are spotted on the plate, such as Figure 5 c (partial enlarged view as shown in Figure 5 d), it can be seen that the spots formed by water-dispersed GO are more uniform ( Figure 5 c left), the uniformity of GO spots dispersed in acetonitrile is the worst. Therefore, it is preferred to use water-dispersed GO for the experiment.

[0077] Example 3

[0078] The method for detecting antioxidants in degradable plastics according to the embodiment of the present invention detects antioxidant 1098, which is specifically as follows:

[0079] The solid powder of antioxidant 1098 was dissolved in ACN to prepare a solution with a concentration of 1 mg / mL, and then diluted to a gradient concentration of 0.4 to 250 μg / mL for later use.

[0080] Before each test, 0.5 μL of antioxidant 1098 solution and graphene oxide (GO) aqueous dispersion (1:1) was spotted on the ITO-coated glass slide, the solvent was evaporated, and the glass slide was placed in the instrument for mass spectrometry analysis. The mass spectrometry results are shown in Figure 6 As shown in a.

[0081] The dynamic curve was obtained and different concentrations (0.4-250 μg / mL) of antioxidant 1098 were tested by mass spectrometry. The unit area concentration was used as the horizontal axis and the mass spectrometry signal intensity was used as the vertical axis, and the least squares regression was used for fitting. The average ion intensity and linear regression equation can be used to determine the content of additives in degradable plastics. Each calibration point was repeated 5 times. The results are shown in Figure 2. Figure 7 As shown in a.

[0082] MS detection conditions: MS was in full scan positive ion mode with a mass range of 200-1000Da. The sampling voltage was set to 3.50kV and the detector voltage was set to 1.80kV. During the analysis, the laser energy intensity and the number of needles were carefully adjusted to obtain the mass spectrum with the best signal-to-noise ratio and the least interference. The typical optimized values ​​were laser intensity 20.0 and laser number 100.

[0083] Example 4

[0084] The method for detecting antioxidants in degradable plastics according to the embodiment of the present invention detects antioxidant 1520, which is specifically as follows:

[0085] The solid powder of antioxidant 1520 was dissolved in ACN to prepare a solution with a concentration of 1 mg / mL, and then diluted to the required concentration for use. Before each test, 0.5 μL of antioxidant 1520 solution and GO aqueous dispersion (1:1) was spotted on the ITO-coated glass slide, the solvent was evaporated, and the glass slide was placed in the instrument for mass spectrometry analysis. The mass spectrometry results are shown in Figure 6 As shown in b.

[0086] The dynamic curve was obtained, and different concentrations (0.4-250 μg / mL) of antioxidant 1520 were tested by mass spectrometry. The concentration per unit area was used as the horizontal axis, and the mass spectrometry signal intensity was used as the vertical axis. The least squares regression fitting was used. The average ion intensity and the linear regression equation were used to determine the content of the additive in the degradable plastic. Each calibration point was repeated 5 times. The results are as follows Figure 7 As shown in b.

[0087] MS detection conditions: MS was in full scan positive ion mode with a mass range of 200-1000Da; the sampling voltage was set to 3.50kV and the detector voltage was set to 1.80kV. During the analysis, the laser energy intensity and the number of needles were carefully adjusted to obtain the mass spectrum with the best signal-to-noise ratio and the least interference. The typical optimized values ​​were laser intensity 20.0 and laser number 100.

[0088] Example 5

[0089] The method for detecting antioxidants in degradable plastics according to the embodiment of the present invention detects antioxidant 1726, which is specifically as follows:

[0090] The solid powder of antioxidant 1726 was dissolved in ACN to prepare a solution with a concentration of 1 mg / mL, and then diluted to a gradient concentration of 0.4-250 μg / mL for later use. Before each test, 0.5 μL of antioxidant 1726 solution and GO aqueous dispersion (1:1) was spotted on the ITO-coated glass slide, the solvent was evaporated, and the glass slide was placed in the instrument for mass spectrometry analysis. The mass spectrometry results are shown in Figure 6 As shown in c.

[0091] The dynamic curve was obtained and different concentrations (0.4-250 μg / mL) of antioxidant 1726 were tested by mass spectrometry. The unit area concentration was used as the horizontal axis and the mass spectrometry signal intensity was used as the vertical axis, and the least squares regression was used for fitting. The content of additives in the biodegradable plastic can be determined using the average ion intensity and the linear regression equation. Each calibration point was repeated 5 times, and the results are as follows: Figure 7 As shown in c.

[0092] MS detection conditions: MS was in full scan positive ion mode with a mass range of 200-1000Da. The sampling voltage was set to 3.50kV and the detector voltage was set to 1.80kV. During the analysis, the laser energy intensity and the number of needles were carefully adjusted to obtain the mass spectrum with the best signal-to-noise ratio and the least interference. The typical optimized values ​​were laser intensity 20.0 and laser number 100.

[0093] Example 6

[0094] The method for detecting antioxidants in degradable plastics according to the embodiment of the present invention detects antioxidant 3114, which is specifically as follows:

[0095] The solid powder of antioxidant 3114 was dissolved in ACN to prepare a solution with a concentration of 1 mg / mL, and then diluted to the required concentration before use. Before each test, 0.5 μL of antioxidant 3114 solution and GO aqueous dispersion (1:1) was spotted on the ITO-coated glass slide, the solvent was evaporated, and the glass slide was placed in the instrument for mass spectrometry analysis. The mass spectrometry results are shown in Figure 6 As shown in d.

[0096] The dynamic curve was obtained and different concentrations (0.4-250 μg / mL) of antioxidant 3114 were tested by mass spectrometry. The unit area concentration was used as the horizontal axis and the mass spectrometry signal intensity was used as the vertical axis, and the least squares regression was used for fitting. The average ion intensity and linear regression equation can be used to determine the content of additives in degradable plastics. Each calibration point was repeated 5 times. The results are shown in Figure 2. Figure 7 As shown in d.

[0097] MS detection conditions: MS was in full scan positive ion mode with a mass range of 200-1000Da. The sampling voltage was set to 3.50kV and the detector voltage was set to 1.80kV. During the analysis, the laser energy intensity and the number of needles were carefully adjusted to obtain the mass spectrum with the best signal-to-noise ratio and the least interference. The typical optimized values ​​were laser intensity 20.0 and laser number 100.

[0098] Example 7

[0099] In this embodiment, the accuracy of the method for detecting antioxidants in degradable plastics according to the embodiment of the present invention is tested as follows:

[0100] 1. Preparation of samples to be tested

[0101] Prepare polylactic acid with a specified concentration of antioxidant 1098 as a true standard for method validation. Evenly mix 990 mg of PLA powder with 10 mg of antioxidant 1098 to prepare a standard sample with a mass fraction of 1%. Dissolve a small amount of the mixed powder in a glass vial with chloroform until a uniform paste is formed. After ultrasonication for 5 minutes, fill the paste into an aluminum foil mold with a size of 10 mm × 10 mm and place it in a fume hood at room temperature until the solvent evaporates. Crush the standard sample at low temperature, weigh 1 mg of the standard sample and dissolve it in chloroform to prepare a 1 mg / mL actual sample.

[0102] 2. Analysis and testing

[0103] The patented method was used for mass spectrometry analysis. 0.5 μL of the actual sample solution and GO aqueous dispersion (1:1) were spotted on an ITO-coated glass slide, the solvent was evaporated, and the glass slide was placed in the instrument for mass spectrometry analysis. The mass spectrometry results were as follows: Figure 8 As shown in b. Figure 8 a shows the results of simultaneous analysis of four antioxidants, indicating that this method can simultaneously determine multiple potential antioxidants.

[0104] Referring to the mass spectrometry analysis results of the mixed sample of four antioxidant standard substances in Example 3-6, the qualitative analysis of the antioxidants can be achieved, and the analysis results are brought into the dynamic curve constructed in Example 3-6 to achieve the qualitative analysis of the antioxidant 1098 in PLA.

[0105] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0106] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for detecting antioxidants in degradable plastics, characterized in that: include: The sample to be tested is crushed to obtain sample powder; mixing the sample powder with a solvent to obtain a solution containing the sample powder; mixing the solution with an auxiliary ionization matrix to obtain a mixed solution; as well as The mixed solution is subjected to open mass spectrometry detection to obtain a qualitative detection of the antioxidant.

2. The method according to claim 1, characterized in that: The pulverization process is cryogenic grinding, Optionally, the conditions of the cryogenic grinding are 20-30 Hz, 1-2 min, Optionally, the particle size of the sample powder is 20-200 μm.

3. The method according to claim 1, characterized in that The auxiliary ionization matrix is ​​a single layer of graphene oxide, Optionally, the single-layer graphene oxide has a thickness of 0.8-1.2 nm and a radius of less than 5 μm.

4. The method according to claim 1, characterized in that: The concentration of graphene oxide in the mixed solution is 0.5-10 mg / mL, Optionally, the volume of the mixed solution is 2-200 μL.

5. The method according to claim 1, characterized in that The open mass spectrometer is a time-of-flight (TOF) mass spectrometer equipped with a laser source.

6. The method according to claim 1, characterized in that The operating parameters of the mass spectrometry detection are: Ion source: focused laser with 5ns pulse width; The working parameters of the focused laser are: frequency 1000 Hz, laser intensity 15-25.0, laser number 100-1000; Minimum laser spot diameter: no more than 10μm.

7. The method according to claim 1, characterized in that Mass spectrometry conditions for the mass spectrometry detection: Ionic polarity: positive ion; Mass range: m / z 200-1000Da; Sampling voltage: 3.2-3.8kV; Detector voltage: 1.50-2.0 kV.

8. The method according to claim 1, characterized in that The samples to be tested are degradable plastics and products thereof.

9. The method according to claim 1, characterized in that: The antioxidant is an antioxidant functional additive that can be used for degrading plastics, preferably, at least one selected from antioxidant 1098, antioxidant 1520, antioxidant 1726 and antioxidant 3114.

10. A kit for detecting antioxidants in degradable plastics, characterized in that: The method comprises the reagents, standards, auxiliary ionization matrix or a combination of at least one of them used in the method for detecting antioxidants in degraded plastics according to any one of claims 1 to 9.

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