A method for analyzing cardanol in paint by thermal cracking gas chromatography-mass spectrometer and application

Abstract

The application provides a method for analyzing cardanol in paint by using a thermal cracking gas chromatograph-mass spectrometer, and comprises the following steps: dissolving a paint sample with a solvent, performing thermal cracking, and then testing and analyzing by using a gas chromatograph-mass spectrometer; the solvent used is a mixed solvent of ethyl acetate, dimethylbenzene and acetone; and thermal cracking is performed at a suitable cracking temperature; and qualitative and quantitative analysis is performed on the content of cardanol in the paint.

Description

Technical Field

[0001] This invention belongs to the field of analytical testing, specifically relating to a method and application for analyzing cashew phenol in coatings using a pyrolysis gas chromatography-mass spectrometry (GC-MS) instrument. Background Technology

[0002] Cashew nut shell oil (CPO) is a green and renewable phenol that can be extracted from natural cashew nut shell oil. It is biodegradable, renewable, and environmentally friendly. Structurally, CPO contains long unsaturated carbon chains, which can enhance the flexibility of coatings; it also contains benzene rings, which can enhance the corrosion resistance of coatings. Adding an appropriate amount of CPO to coatings can increase their flexibility and reduce their viscosity, making it a coating toughening agent with excellent chemical and physical properties. However, due to the relatively high price of CPO and the fact that only appropriate amounts can achieve optimal coating performance, finding an accurate analytical method for analyzing CPO in coatings is crucial for determining coating performance.

[0003] Currently, common methods for analyzing cashew nut shellac in coatings include infrared spectroscopy and liquid chromatography. However, infrared spectroscopy is not effective for analyzing trace amounts of cashew nut shellac in complex coating components; liquid chromatography requires complex and lengthy separation steps. Conventional gas chromatography-mass spectrometry (GC-MS) instruments have low injection temperatures, making it impossible to analyze cashew nut shellac, which has a large molecular weight and high volatilization temperature, in coatings.

[0004] A thermal pyrolysis gas chromatography-mass spectrometry (Py-GC / MS) method was employed. This method rapidly pyrolyzes trace amounts of paint samples under an inert atmosphere, generating numerous pyrolysis products that are effectively separated in the gas chromatography system. Characteristic pyrolysis fragments are then accurately identified by mass spectrometry. The method can qualitatively identify cashew nut shellac in trace paint samples in just 1 hour. Py-GC / MS can directly identify pyrolysis product fragments and use the final pyrolysis fragments to deduce the composition and structure of the analyte. Since the fragmentation mode mainly depends on the molecular structure of the sample and the absorbed energy, the characteristic peaks of cashew nut shellac can be identified. The results are highly correlated, and the method is rapid, accurate, and simple. Summary of the Invention

[0005] This invention employs a thermal pyrolysis gas chromatography-mass spectrometry (Py-GC / MS) method, which utilizes the rapid heating and pyrolysis of trace amounts of coating samples in an inert atmosphere. The resulting numerous pyrolysis products are effectively separated in a gas chromatography system, allowing the characteristic cashew phenol fragments to be accurately identified by mass spectrometry. Qualitative and quantitative analysis of cashew phenol in trace amounts of coating samples can be performed in just 1 hour.

[0006] One objective of this invention is to provide a method for analyzing cashew nut shellac in coatings using a pyrolysis gas chromatography-mass spectrometry (GC-MS) system. The method includes: dissolving the coating sample in a solvent, performing pyrolysis, and then analyzing the resulting sample using a GC-MS system. The solvent is a mixture of ethyl acetate, xylene, and acetone. The cashew nut shellac obtained by this method includes both free cashew nut shellac in the coating sample and cashew nut shellac that has reacted with other components.

[0007] In the method for analyzing cashew phenol in coatings using a pyrolysis gas chromatography-mass spectrometry system provided by this invention:

[0008] In the mixed solvent, the content of ethyl acetate is 1-45% by volume, the content of xylene is 1-45% by volume, and the content of acetone is 10-100% by volume; preferably, the content of ethyl acetate is 20-35% by volume, the content of xylene is 20-35% by volume, and the content of acetone is 30-60% by volume; more preferably, the content of ethyl acetate is 35% by volume, the content of xylene is 35% by volume, and the content of acetone is 30% by volume.

[0009] There is no particular limitation on the amount of the mixed solvent, as long as it is sufficient to fully dissolve the coating sample. For example, the amount of the mixed solvent is 10 to 50 times that of the sample.

[0010] In the method for analyzing cashew phenol in coatings using a pyrolysis gas chromatography-mass spectrometry system provided by this invention:

[0011] The sample dissolution process includes centrifugation, followed by thermal pyrolysis of the supernatant and analysis using gas chromatography-mass spectrometry (GC-MS). The dissolution temperature is between 15 and 35°C.

[0012] In the method for analyzing cashew phenol in coatings using a pyrolysis gas chromatography-mass spectrometry system provided by this invention:

[0013] The pyrolysis is carried out in a protective gas atmosphere, which may be nitrogen.

[0014] The temperature of the thermal decomposition is 200–650°C, preferably 300–600°C, and more preferably 450°C;

[0015] The pressure for thermal decomposition is 30–70 kPa;

[0016] The thermal decomposition time is 5–25 seconds.

[0017] In the method for analyzing cashew phenol in coatings using a pyrolysis gas chromatography-mass spectrometry system provided by this invention:

[0018] The testing conditions for the gas chromatography-mass spectrometry (GC-MS) instrument are as follows:

[0019] The gas chromatography conditions were as follows: DB-5MS column; injection port temperature: 200–300℃; detector temperature: 200–300℃.

[0020] In gas chromatography, multi-stage heating is used in the column oven to separate the pyrolysis products; preferably, the operating conditions of the column oven are as follows: first, maintain the temperature at 35-65℃ for 3-7 minutes, then increase the temperature at a rate of 3-10℃ / min to 160-220℃ and maintain it for 3-7 minutes, and finally increase the temperature at a rate of 5-12℃ / min to 230-300℃ and maintain it for 3-7 minutes.

[0021] The mass spectrometry conditions were as follows: EI ion source was used; ion source temperature was 200–350℃; transfer line temperature was 150–290℃; ion source energy was 50–90 eV; full scan mode was used; and mass scan range was 50 m / z–500 m / z.

[0022] Ions with mass-to-charge ratios of 10⁸, 120, and 30² were selected from the spectra obtained by gas chromatography-mass spectrometry (GC-MS) for analysis.

[0023] In the method for analyzing cashew nut shellac in coatings using pyrolysis gas chromatography-mass spectrometry (GC-MS) provided by this invention: The external standard method is used for quantitative analysis of cashew nut shellac in the coatings. The standard curve used in the external standard method can be plotted according to commonly used methods in the art. Specifically, the standard curve can be plotted as follows: First, at least three samples of different concentrations are prepared using bisphenol A epoxy resin and cashew nut shellac as standard samples. The concentration of cashew nut shellac in the standard samples can be selected within the range of 1% to 50%. Then, the standard samples of different concentrations are tested according to the above-described dissolution-centrifugation-pyrolysis-GC-MS analysis procedure. A standard curve is constructed with the concentration of cashew nut shellac in the standard samples as the abscissa (x) and the response value as the ordinate (y). Substituting the response value of cashew nut shellac in the test results of the coating sample to be tested into the standard curve yields the cashew nut shellac content in the coating sample to be tested.

[0024] The second objective of this invention is to provide an application of the above-mentioned method for analyzing cashew phenols in coatings using a thermal pyrolysis gas chromatography-mass spectrometry (GC-MS) system in coating component analysis.

[0025] This invention utilizes a suitable pyrolysis temperature to decompose high-molecular-weight substances in coatings into compounds of appropriate molecular weight. Multi-stage heating allows for better separation of compounds with different volatilization temperatures within the coating sample, resulting in improved separation between different compounds and minimizing mutual interference. This facilitates better separation and qualitative analysis in chromatography, improving the accuracy of subsequent mass spectrometry analysis. The invention pretreatment the coating sample using methods such as mixed solvent dissolution, ultrasonication, and ultra-high-speed centrifugation, followed by thermal pyrolysis at a specific temperature. The pyrolysis products are then separated by multi-stage gas chromatography followed by mass spectrometry analysis, enabling rapid qualitative identification of cashew phenols in the coating. This is of significant importance for determining coating performance. Attached Figure Description

[0026] Figure 1 The total ion flux diagrams are for samples from Examples 1, 3-4 and Comparative Example 3, where curves a, b, and c are the total ion flux diagrams for samples from Examples 1, 4, and 3, respectively, and curve d is the total ion flux diagram for samples from Comparative Example 3.

[0027] Figure 2 The total ion flux diagrams are for the samples of Examples 1-2 and Comparative Examples 1-2, where curves a and b are the total ion flux diagrams obtained from the test samples of Examples 1 and 2, respectively, and curves c and d are the total ion flux diagrams obtained from the test samples of Comparative Examples 1 and 2, respectively.

[0028] Figure 3 This is a total ion flux diagram of the sample from Example 1.

[0029] Figure 4 This is the mass spectrum of pure cashew phenol.

[0030] Figure 5 The chromatogram of the sample from Example 1 at 26.68 min is shown. Detailed Implementation

[0031] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0032] The testing instruments and conditions used in this embodiment are as follows:

[0033] 7000D Triple Quadrupole Gas Spectrometer, Agilent Technologies, Inc., USA;

[0034] EGA / PY-3030D pyrolysis unit, EGA Japan;

[0035] CS1200 ultra-high speed centrifuge, Hitachi, Japan.

[0036] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0037] Cashew phenol, analytical grade, Sinopharm Reagent; Ethyl acetate, chromatographic grade, Xilong Scientific Co., Ltd.; Acetone, analytical grade, Sinopharm Reagent; Xylene, analytical grade, Sinopharm Reagent.

[0038] Example 1

[0039] (1) Weigh 1g of commercially available paint sample A (HHY706, provided by the Marine Chemical Research Institute), add 20mL of a mixed solvent of ethyl acetate, xylene and acetone to dissolve the sample at 20℃. The types and proportions of the solvents used are shown in Table 1. After ultrasonic dissolution for 30min, centrifuge at 15000 rpm for 20min in an ultra-high speed centrifuge.

[0040] (2) Take the supernatant liquid for thermal pyrolysis. Under nitrogen conditions, the pyrolysis temperature is 450℃, the pyrolyzer pressure is 56.75kPa, and the pyrolysis time is 20s.

[0041] (3) After pyrolysis, the sample was analyzed by gas chromatography-mass spectrometry.

[0042] The testing conditions for the gas chromatography-mass spectrometry (GC-MS) instrument are as follows:

[0043] The gas chromatography conditions were as follows: DB-5MS column; injection port temperature 250℃; detector temperature 270℃.

[0044] The column oven uses a programmed temperature rise: 50℃ for 5 minutes, then rises to 200℃ at a rate of 5℃ / min and holds for 5 minutes, and finally rises to 280℃ at a rate of 10℃ / min and holds for 5 minutes.

[0045] The mass spectrometry conditions were: EI ion source; ion source temperature 260℃; transfer line temperature 270℃; ion source energy 75eV; full scan mode; mass scan range 50m / z~500m / z.

[0046] Example 2

[0047] The testing process is the same as in Example 1, except that the mixed solvent is different. The types and proportions of the solvents used are shown in Table 1. The specific method is as follows:

[0048] (1) Weigh 1g of commercially available paint sample A, add 20mL of a mixed solvent of ethyl acetate, xylene and acetone to dissolve the sample at 20℃. The types and proportions of the solvents used are shown in Table 1. After ultrasonic dissolution for 30min, centrifuge at 15000 rpm for 20min in an ultra-high speed centrifuge.

[0049] (2) Take the supernatant liquid for thermal pyrolysis. Under nitrogen conditions, the pyrolysis temperature is 450℃, the pyrolyzer pressure is 56.75kPa, and the pyrolysis time is 20s.

[0050] (3) After pyrolysis, the sample was analyzed by gas chromatography-mass spectrometry.

[0051] The testing conditions for the gas chromatography-mass spectrometry (GC-MS) instrument are as follows:

[0052] The gas chromatography conditions were as follows: DB-5MS column; injection port temperature 250℃; detector temperature 270℃.

[0053] The column oven uses a programmed temperature rise: 50℃ for 5 minutes, then rises to 200℃ at a rate of 5℃ / min and holds for 5 minutes, and finally rises to 280℃ at a rate of 10℃ / min and holds for 5 minutes.

[0054] The mass spectrometry conditions were: EI ion source; ion source temperature 260℃; transfer line temperature 270℃; ion source energy 75eV; full scan mode; mass scan range 50m / z~500m / z.

[0055] Comparative Example 1

[0056] The testing process is the same as in Example 1, except that the mixed solvent is different. The types and proportions of the solvents used are shown in Table 1. The specific method is as follows:

[0057] (1) Weigh 1g of commercially available paint sample A, add 20mL of a mixed solvent of ethyl acetate, xylene and acetone to dissolve the sample at 20℃. The types and proportions of the solvents used are shown in Table 1. After ultrasonic dissolution for 30min, centrifuge at 15000 rpm for 20min in an ultra-high speed centrifuge.

[0058] (2) Take the supernatant liquid for thermal pyrolysis. Under nitrogen conditions, the pyrolysis temperature is 450℃, the pyrolyzer pressure is 56.75kPa, and the pyrolysis time is 20s.

[0059] (3) After pyrolysis, the sample was analyzed by gas chromatography-mass spectrometry.

[0060] The testing conditions for the gas chromatography-mass spectrometry (GC-MS) instrument are as follows:

[0061] The gas chromatography conditions were as follows: DB-5MS column; injection port temperature 250℃; detector temperature 270℃.

[0062] The column oven uses a programmed temperature rise: 50℃ for 5 minutes, then rises to 200℃ at a rate of 5℃ / min and holds for 5 minutes, and finally rises to 280℃ at a rate of 10℃ / min and holds for 5 minutes.

[0063] The mass spectrometry conditions were: EI ion source; ion source temperature 260℃; transfer line temperature 270℃; ion source energy 75eV; full scan mode; mass scan range 50m / z~500m / z.

[0064] Comparative Example 2

[0065] The testing process is the same as in Example 1, except that the mixed solvent is different. The types and proportions of the solvents used are shown in Table 1. The specific method is as follows:

[0066] (1) Weigh 1g of commercially available paint sample A, add 20mL of a mixed solvent of ethyl acetate, xylene and acetone to dissolve the sample at 20℃. The types and proportions of the solvents used are shown in Table 1. After ultrasonic dissolution for 30min, centrifuge at 15000 rpm for 20min in an ultra-high speed centrifuge.

[0067] (2) Take the supernatant liquid for thermal pyrolysis. Under nitrogen conditions, the pyrolysis temperature is 450℃, the pyrolyzer pressure is 56.75kPa, and the pyrolysis time is 20s.

[0068] (3) After pyrolysis, the sample was analyzed by gas chromatography-mass spectrometry.

[0069] The testing conditions for the gas chromatography-mass spectrometry (GC-MS) instrument are as follows:

[0070] The gas chromatography conditions were as follows: DB-5MS column; injection port temperature 250℃; detector temperature 270℃.

[0071] The column oven uses a programmed temperature rise: 50℃ for 5 minutes, then rises to 200℃ at a rate of 5℃ / min and holds for 5 minutes, and finally rises to 280℃ at a rate of 10℃ / min and holds for 5 minutes.

[0072] The mass spectrometry conditions were: EI ion source; ion source temperature 260℃; transfer line temperature 270℃; ion source energy 75eV; full scan mode; mass scan range 50m / z~500m / z.

[0073] Table 1. Mixed solvent ratios (volume ratio) for Examples 1-2 and Comparative Examples 1-2

[0074] Example 1 35 35 30 Example 2 20 20 60 Comparative Example 1 50 50 0 Comparative Example 2 0 0 100

[0075] Thermal pyrolysis-GC-MS analysis revealed that the peak elution time of cashew nut shellac in the sample was approximately 26.6 min. After dissolution with the mixed solvent, the peak response values ​​of the coating samples from Examples 1 and 2 were larger, indicating that the mixed solvent from Examples 1 and 2 could better dissolve the cashew nut shellac in the samples. The total ion flux chromatograms for cashew nut shellac detection after extraction with four different proportions of mixed solvents are shown below. Figure 3 The response values ​​are shown in Table 2.

[0076] Table 2. Mass spectral peak response values ​​of cashew nut shell extract after mixed solvent extraction in Examples 1-2 and Comparative Examples 1-2

[0077] Example 1 47582 Example 2 34521 Comparative Example 1 28554 Comparative Example 2 19775

[0078] Example 3

[0079] The testing process is the same as in Example 1, except that the pyrolysis temperature is different; the pyrolysis temperature is 300℃. The specific method is as follows:

[0080] (1) Weigh 1g of commercially available paint sample A, add 20mL of mixed solvent (ethyl acetate, xylene and acetone in a volume ratio of 35:35:30) and dissolve the sample at 20℃. The types and proportions of the solvents used are shown in Table 1. After ultrasonic dissolution for 30min, centrifuge at 15000 rpm for 20min in an ultra-high speed centrifuge.

[0081] (2) Take the supernatant liquid for thermal pyrolysis. Under nitrogen conditions, the pyrolysis temperature is 300℃, the pyrolyzer pressure is 56.75kPa, and the pyrolysis time is 20s.

[0082] (3) After pyrolysis, the sample was analyzed by gas chromatography-mass spectrometry.

[0083] The testing conditions for the gas chromatography-mass spectrometry (GC-MS) instrument are as follows:

[0084] The gas chromatography conditions were as follows: DB-5MS column; injection port temperature 250℃; detector temperature 270℃.

[0085] The column oven uses a programmed temperature rise: 50℃ for 5 minutes, then rises to 200℃ at a rate of 5℃ / min and holds for 5 minutes, and finally rises to 280℃ at a rate of 10℃ / min and holds for 5 minutes.

[0086] The mass spectrometry conditions were: EI ion source; ion source temperature 260℃; transfer line temperature 270℃; ion source energy 75eV; full scan mode; mass scan range 50m / z~500m / z.

[0087] Example 4

[0088] The testing process is the same as in Example 1, except that the pyrolysis temperature is different; the pyrolysis temperature is 600℃. The specific method is as follows:

[0089] (1) Weigh 1g of commercially available paint sample A, add 20mL of mixed solvent (ethyl acetate, xylene and acetone in a volume ratio of 35:35:30) and dissolve the sample at 20℃. The types and proportions of the solvents used are shown in Table 1. After ultrasonic dissolution for 30min, centrifuge at 15000 rpm for 20min in an ultra-high speed centrifuge.

[0090] (2) Take the supernatant liquid for thermal pyrolysis. Under nitrogen conditions, the pyrolysis temperature is 600℃, the pyrolyzer pressure is 56.75kPa, and the pyrolysis time is 20s.

[0091] (3) After pyrolysis, the sample was analyzed by gas chromatography-mass spectrometry.

[0092] The testing conditions for the gas chromatography-mass spectrometry (GC-MS) instrument are as follows:

[0093] The gas chromatography conditions were as follows: DB-5MS column; injection port temperature 250℃; detector temperature 270℃.

[0094] The column oven uses a programmed temperature rise: 50℃ for 5 minutes, then rises to 200℃ at a rate of 5℃ / min and holds for 5 minutes, and finally rises to 280℃ at a rate of 10℃ / min and holds for 5 minutes.

[0095] The mass spectrometry conditions were: EI ion source; ion source temperature 260℃; transfer line temperature 270℃; ion source energy 75eV; full scan mode; mass scan range 50m / z~500m / z.

[0096] Example 5

[0097] The testing process is the same as in Example 1, except that the pyrolysis temperature is different; the pyrolysis temperature is 550℃. The specific method is as follows:

[0098] (1) Weigh 1g of commercially available paint sample A, add 20mL of a mixed solvent of ethyl acetate, xylene and acetone (the volume ratio of ethyl acetate, xylene and acetone is 35:35:30) to dissolve the sample at 25℃, sonicate for 30min, and then centrifuge at 15000 rpm for 20min in an ultra-high speed centrifuge.

[0099] (2) Take the supernatant liquid for thermal pyrolysis. Under nitrogen conditions, the pyrolysis temperature is 550℃, the pyrolyzer pressure is 56.75kPa, and the pyrolysis time is 20s.

[0100] (3) After pyrolysis, the sample was analyzed by gas chromatography-mass spectrometry.

[0101] The testing conditions for the gas chromatography-mass spectrometry (GC-MS) instrument are as follows:

[0102] The gas chromatography conditions were as follows: DB-5MS column; injection port temperature: 230℃; detector temperature: 300℃.

[0103] The column oven uses a programmed temperature rise: maintain 30℃ for 5 minutes, then rise to 200℃ at a rate of 10℃ / min and maintain for 5 minutes, and finally rise to 300℃ at a rate of 5℃ / min and maintain for 5 minutes.

[0104] The mass spectrometry conditions were: EI ion source; ion source temperature 260℃; transfer line temperature 270℃; ion source energy 75eV; full scan mode; mass scan range 50m / z~500m / z.

[0105] Comparative Example 3

[0106] The testing process is the same as in Example 1, except that the pyrolysis temperature is different; the pyrolysis temperature is 150℃. The specific method is as follows:

[0107] (1) Weigh 1g of commercially available paint sample A, add 20mL of mixed solvent (ethyl acetate, xylene and acetone in a volume ratio of 35:35:30) and dissolve the sample at 20℃. The types and proportions of the solvents used are shown in Table 1. After ultrasonic dissolution for 30min, centrifuge at 15000 rpm for 20min in an ultra-high speed centrifuge.

[0108] (2) Take the supernatant liquid for thermal pyrolysis. Under nitrogen conditions, the pyrolysis temperature is 150℃, the pyrolyzer pressure is 56.75kPa, and the pyrolysis time is 20s.

[0109] (3) After pyrolysis, the sample was analyzed by gas chromatography-mass spectrometry.

[0110] The testing conditions for the gas chromatography-mass spectrometry (GC-MS) instrument are as follows:

[0111] The gas chromatography conditions were as follows: DB-5MS column; injection port temperature 250℃; detector temperature 270℃.

[0112] The column oven uses a programmed temperature rise: 50℃ for 5 minutes, then rises to 200℃ at a rate of 5℃ / min and holds for 5 minutes, and finally rises to 280℃ at a rate of 10℃ / min and holds for 5 minutes.

[0113] The mass spectrometry conditions were: EI ion source; ion source temperature 260℃; transfer line temperature 270℃; ion source energy 75eV; full scan mode; mass scan range 50m / z~500m / z.

[0114] Figure 1 The results showed that the peak elution time of cashew phenol was 26.6 min, and the pyrolysis temperatures with the largest response values ​​were 450℃, 600℃, and 300℃, respectively. Cashew phenol showed no response value at 150℃. This may be because excessively high pyrolysis temperatures caused some cashew phenol to decompose into smaller compounds, while excessively low temperatures prevented its complete vaporization.

[0115] Table 3. Response values ​​of total ion flux at different pyrolysis temperatures

[0116] Comparative Example 3 150 0 Example 1 450 38745 Example 3 300 19587 Example 4 600 28675 Example 5 550 33521

[0117] Mass spectrometric fragments of pure cashew phenol are shown in Figure 2 Cashew nut shell powder fragments have characteristic mass-to-charge ratios of 108, 120, and 302. Analyzing the retention time and mass-to-charge ratio of pure cashew nut shell powder can be compared with that of unknown coatings to qualitatively analyze whether the unknown coatings contain cashew nut shell powder.

[0118] The total ion flow chromatogram obtained in Example 1 is as follows: Figure 4 As shown, cashew phenols elute at 26.68 min, exhibiting excellent peak response, shape, and separation between the two peaks, allowing for good qualitative analysis. Mass spectrometric fragments of the coating at 26.68 min are shown below. Figure 5 Characteristic mass-to-charge ratio fragments include 108, 120, and 302, which are consistent with the retention time and mass-to-charge ratio of pure cashew phenol.

[0119] Example 6: Quantitative Analysis of Cashew Phenol in Coating Samples

[0120] 10%, 20%, and 30% cashew nut shellac were added to bisphenol A epoxy resin as standard samples, and the tests were conducted according to the procedure shown below to create a standard curve.

[0121] Standard curve and test methods for commercially available paint sample 2:

[0122] (1) Weigh 1g of the sample to be tested, add 20mL of a mixed solvent of ethyl acetate, xylene and acetone (the volume ratio of ethyl acetate, xylene and acetone is 35:35:30) to dissolve the sample at 25℃, sonicate for 30min, and then centrifuge at 15000 rpm for 20min in an ultra-high speed centrifuge.

[0123] (2) Take the supernatant liquid for thermal pyrolysis. Under nitrogen conditions, the pyrolysis temperature is 450℃, the pyrolyzer pressure is 56.75kPa, and the pyrolysis time is 20s.

[0124] (3) After pyrolysis, the sample was analyzed by gas chromatography-mass spectrometry.

[0125] The testing conditions for the gas chromatography-mass spectrometry (GC-MS) instrument are as follows:

[0126] The gas chromatography conditions were as follows: DB-5MS column; injection port temperature 250℃; detector temperature 270℃.

[0127] The column oven uses a programmed temperature rise: 50℃ for 5 minutes, then rises to 200℃ at a rate of 5℃ / min and holds for 5 minutes, and finally rises to 280℃ at a rate of 10℃ / min and holds for 5 minutes.

[0128] The mass spectrometry conditions were: EI ion source; ion source temperature 260℃; transfer line temperature 270℃; ion source energy 75eV; full scan mode; mass scan range 50m / z~500m / z.

[0129] After testing, the instrument response values ​​for 10%, 20%, and 30% cashew phenol standard samples were 1.09 × 10⁻⁶, respectively. 8 1.92×10 8 2.98×10 8 A standard curve was established with the concentration of cashew phenol in the three standard samples as the x-axis and the response value as the y-axis. The obtained standard curve equation is y = 9459474x + 10626117, and the correlation coefficient r = 0.995.

[0130] Following the above testing procedures, the cashew phenol content in commercially available paint sample 2 (HHY705, provided by the Marine Chemical Research Institute) was tested, and the sample's response value was 7.26 × 10⁻⁶. 7 Substituting the values ​​into the standard curve, the cashew phenol content in the commercially available paint sample was calculated to be 6.55%.

[0131] This invention involves thermally pyrolyzing the coating and analyzing the pyrolysis products using a gas chromatography-mass spectrometry (GC-MS). Analysis revealed that the pyrolysis temperatures with the highest to lowest total ion flux response values ​​were 450℃, 600℃, and 300℃, confirming 450℃ as a relatively suitable pyrolysis temperature. The coating was dissolved in mixed solvents of varying proportions. Analysis of the solvent used in Example 1 showed the highest chromatographic peak response, indicating that this mixed solvent can more effectively extract cashew nut shellac from the coating. Under optimal conditions, the total ion flux chromatogram of the coating sample showed cashew nut shellac eluted at 26.68 min, exhibiting significant characteristic mass-to-charge ratio fragmentation. The peak response, peak shape, and separation between peaks were all excellent, allowing for good qualitative analysis. Subsequently, standard curves can be established using different concentrations of pure cashew nut shellac to accurately quantify the cashew nut shellac content in the coating.

Claims

1. A method for analyzing cashew phenols in coatings using a pyrolysis gas chromatography-mass spectrometry (GC-MS) system, comprising: After dissolving the coating sample in a solvent, thermally pyrolyzing it, and then analyzing it using gas chromatography-mass spectrometry (GC-MS), the solvent was a mixture of ethyl acetate, xylene, and acetone. The mixed solvent contained, by volume percentage, 20-35% ethyl acetate, 20-35% xylene, and 30-60% acetone. In the GC-MS column oven, the pyrolysis products were separated using multi-stage heating. The operating conditions of the column oven were: first, maintaining the temperature at 35-65℃ for 3-7 minutes; then, increasing the temperature at a rate of 3-10℃ / min to 160-220℃ and maintaining it for 3-7 minutes; finally, increasing the temperature at a rate of 5-12℃ / min to 230-300℃ and maintaining it for 3-7 minutes. The testing conditions for the gas chromatography-mass spectrometry (GC-MS) instrument were as follows: GC conditions: DB-5MS column; injection port temperature: 200–300℃; detector temperature: 200–300℃; mass spectrometry conditions: EI ion source; ion source temperature: 200–350℃; transfer line temperature: 150–290℃; ion source energy: 50–90 eV; full scan mode; mass scan range: 50 m / z–500 m / z; ions with mass-to-charge ratios of 10⁸, 120, and 30² were selected for analysis from the GC-MS spectra.

2. The method according to claim 1, characterized in that, After the sample is dissolved, a centrifugation step is also included. The supernatant after centrifugation is thermally pyrolyzed and then tested and analyzed using a gas chromatography-mass spectrometry (GC-MS) instrument.

3. The method according to claim 1, characterized in that, The dissolution temperature is 15~35℃.

4. The method according to claim 1, characterized in that, The pyrolysis is carried out under a protective gas atmosphere; and / or, The temperature of the pyrolysis is 200~650℃; and / or, The pressure of the thermal decomposition is 30~70 kPa; and / or, The thermal decomposition time is 5~25s.

5. The method according to claim 4, characterized in that, The temperature of the pyrolysis is 300~600℃.

6. The method according to any one of claims 1 to 5, characterized in that, The external standard method was used to quantitatively analyze cashew phenol in the coating.

7. The method for analyzing cashew phenol in coatings using a pyrolysis gas chromatography-mass spectrometry system as described in any one of claims 1 to 6, and its application in coating component analysis.

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