Detection method for determining content of dissolved substances in polyvinyl alcohol film based on gas chromatography

Abstract

The invention relates to the technical field of analysis and detection, in particular to a detection method for determining the content of dissolved substances in a polyvinyl alcohol film based on gas chromatography, which comprises the following steps: S1, placing a polyvinyl alcohol film sample in a humidity control box for balancing; s2, carrying out brittle failure treatment to obtain sphere-like fragments; s3, carrying out drying treatment to obtain dehydrated activated fragments; s4, low-temperature plasma surface treatment is carried out, and the surface micropore expansion rate is increased; s5, performing dynamic extraction in an alternating pressure field; s6, carrying out third-stage separation treatment to remove large particles and colloidal substances; s7, carrying out a derivatization reaction to convert the dissolved substance into a volatile derivative; s8, injecting the derivatization solution into a gas chromatograph-mass spectrometer for detection; according to the method, the pretreatment process of the polyvinyl alcohol film is optimized, and the micropore expansion rate correction factor is introduced, so that the detection precision and sensitivity of the dissolved substance are improved, and the problem of insufficient precision is solved.

Description

Technical Field

[0001] The present invention relates to the field of analytical detection technology, and particularly to a detection method for determining the content of leachates in polyvinyl alcohol films based on gas chromatography. Background Art

[0002] As a polymer material with excellent physical and chemical properties, polyvinyl alcohol (PVA) films are widely used in many fields such as packaging, drug delivery systems, and electronic devices; due to their good water solubility, degradability, and high transparency, the application of PVA films in environmentally friendly products is increasing; however, with the wide application of PVA films, the content of leachates during their use has become a problem that cannot be ignored; the content of leachates not only affects the performance of PVA films, but may also have potential impacts on the use environment and consumer health; therefore, accurately determining the content of leachates in polyvinyl alcohol films is of great significance for their quality control and safety assessment of applications.

[0003] Currently, there are some techniques for determining the content of leachates in polyvinyl alcohol films, but most methods have certain limitations; for example, traditional leachate detection methods usually rely on simple leaching methods, lacking sufficient precision and sensitivity, and it is difficult to effectively distinguish trace leachates; although techniques such as liquid chromatography and gas chromatography have been applied to the detection of film leachates, these methods usually require complex pretreatment processes and expensive equipment, and cannot effectively compensate for the volatility of leachates and the relationship between them and the microporous structure on the film surface accurately. Therefore, the existing techniques are insufficient in improving detection precision, simplifying operations, and reducing costs. Summary of the Invention

[0004] Based on the above purposes, the present invention provides a detection method for determining the content of leachates in polyvinyl alcohol films based on gas chromatography.

[0005] The detection method for determining the content of leachates in polyvinyl alcohol films based on gas chromatography includes the following steps: S1: Place the polyvinyl alcohol film sample in a humidity control box for equilibration to obtain a humidity homogenized film; S2: Place the humidity homogenized film in liquid nitrogen vapor and quickly cool it to a predetermined temperature, and perform brittle fracture treatment using a shock wave crusher to obtain spherical-like fragments; S3: Transfer the spherical-like fragments to a microwave drying device for drying treatment to obtain dehydrated and activated fragments; S4: Perform low-temperature plasma surface treatment on the dehydrated and activated fragments to increase their surface micropore expansion rate; S5: Mix the treated fragments with an ethanol-n-hexane mixture in a predetermined ratio, and perform dynamic extraction in an alternating pressure field to obtain an extraction solution; S6: Perform a three - stage separation process on the extraction solution to remove large particulate matter and colloidal substances to obtain a clarified test solution; S7: Add a derivatization reagent to the clarified test solution to carry out a derivatization reaction, converting the dissolved substances into volatile derivatives to obtain a derivatized solution; S8: Inject the derivatized solution into a gas chromatography - mass spectrometry (GC - MS) instrument for detection, and perform quantitative compensation on the detection results based on the micropore expansion rate correction factor, and finally obtain the content of the dissolved substances in the polyvinyl alcohol film.

[0006] Optionally, the specific steps of S1 include: S11: Place the polyvinyl alcohol film sample in a humidity control box, set the temperature of the humidity control box to 22°C to 24°C, and the relative humidity to 38% to 42%; S12: Keep the film sample in the set temperature and humidity control box for 24 hours until the moisture in the sample is evenly distributed to obtain a humidity - homogenized film.

[0007] Optionally, the specific steps of S2 include: S21: Place the humidity - homogenized film sample in liquid nitrogen vapor for rapid cooling, and cool the film temperature to - 50°C; S22: Transfer the rapidly cooled film sample to a shock wave crusher, and set the impact pressure of the shock wave crusher to 0.3 MPa to 0.5 MPa; S23: Start the shock wave crusher for brittle fracture treatment, and the treatment time is 2 to 3 minutes until spherical - like fragments with a particle size of 0.3 mm to 0.8 mm are obtained.

[0008] Optionally, the specific steps of S3 include: S31: Transfer the spherical - like fragments to a microwave drying device and ensure that the fragments are evenly distributed in the drying chamber; S32: Set the vacuum degree of the microwave drying device to 10 Pa; S33: Set the working frequency of the microwave drying device to 2450 MHz, and start microwave radiation for drying treatment; S34: Continuously dry the fragments under the set vacuum degree and frequency until the water content of the fragments is less than 0.05% to obtain dehydrated and activated fragments.

[0009] Optionally, the specific steps of S4 include: S41: Place the dehydrated and activated fragments in a low - temperature plasma reaction chamber, and set the reaction chamber temperature to - 20°C to - 30°C; S42: Introduce argon gas into the reaction chamber as the plasma atmosphere, and adjust the argon gas flow rate to 10 sccm to 15 sccm; S43: Set the power of the low-temperature plasma source to 180 - 220 W, and start the plasma source for surface treatment; S44: Maintain the plasma treatment for 3 - 8 minutes until the micropore expansion rate on the debris surface reaches 15% to 20%.

[0010] Optionally, the specific steps of S5 are as follows: S51: Mix the treated debris with an ethanol - n - hexane mixture at a mass - to - volume ratio of 1:25 to 1:30 to form mixture A, where the volume ratio of the ethanol - n - hexane mixture is 3:1; S52: Transfer mixture A to an alternating pressure field device, set the initial positive pressure of the alternating pressure field to 0.1 MPa, and maintain this pressure for 10 - 15 minutes; S53: Switch the alternating pressure field to negative pressure, set the negative pressure to - 0.08 MPa, and maintain the negative pressure state for 5 - 10 minutes. Through the treatment of the alternating pressure field, the dissolved substances in the extract are gradually released to obtain an extract.

[0011] Optionally, the specific steps of S6 are as follows: S61: Transfer the extract to a centrifuge, set the centrifugation speed to 8000 - 10000 r / min, and the centrifugation time to 5 - 10 minutes to remove large particles; S62: Cross - flow filter the centrifuged extract through a 0.22 - μm ceramic membrane to remove fine particles and suspended matter; S63: Treat the filtered extract through a molecular sieve adsorption column to remove colloidal substances and obtain a clarified test solution. The pore size of the molecular sieve is controlled between 3 Å and 5 Å.

[0012] Optionally, the specific steps of S7 are as follows: S71: Add a silylation derivatization reagent to the clarified test solution. The derivatization reagent is selected from N,O - bis(trimethylsilyl)acetamide or dimethyldichlorosilane, and the addition amount is 3% to 5% of the volume of the test solution; S72: Place the test solution added with the derivatization reagent in a temperature - control device, set the reaction temperature to 50 - 70 °C, and maintain the reaction temperature; S73: Conduct a derivatization reaction for 10 - 20 minutes; S74: After the reaction is completed, obtain volatile derivatives to form a derivatized solution.

[0013] Optionally, the specific steps of S8 are as follows: S81: Inject the derivatized solution into a gas chromatography - mass spectrometry (GC - MS) instrument through an injector, set the column temperature of the chromatograph to 50 °C to 60 °C, and adjust the gas flow rate to 1.0 mL / min to 1.5 mL / min; S82: Set the temperature programming of the gas chromatography-mass spectrometry (GC-MS) instrument so that the column temperature rises from 50 °C to 250 °C at a heating rate of 5-10 °C / min; S83: Perform detection in selective ion monitoring mode and record the mass spectrometry data; S84: Based on the microporous expansion rate correction factor of the fragment surface, quantitatively compensate the detection results of the gas chromatography-mass spectrometry instrument, and calculate the content of the eluate of the polyvinyl alcohol film according to the compensated detection results, and obtain the final result.

[0014] Optionally, S84 specifically includes: S841: According to the detection results of the gas chromatography-mass spectrometry instrument, obtain the peak area of the eluate, denoted as ; S842: Calculate the microporous expansion rate correction factor , and the formula is, , where the expansion rate is the microporous expansion rate of the fragment after surface treatment in S4; S843: Calculate the content of the eluate of the polyvinyl alcohol film , and the formula is: , where is the content of the eluate of the polyvinyl alcohol film; is the peak area detected by gas chromatography; F is the microporous expansion rate correction factor; is the volume of the sample dissolution solution.

[0015] Advantages of the present invention: In the present invention, by optimizing the pretreatment process of the polyvinyl alcohol film, high-precision and high-sensitivity detection of eluates is achieved; compared with traditional detection methods, the operation steps are simplified during the pretreatment process, avoiding cumbersome operations and the use of high-cost equipment; through innovations in microwave drying, low-temperature plasma surface treatment, and dynamic extraction, etc., the extraction efficiency of eluates can be effectively improved, thereby significantly enhancing the accuracy and reliability of the detection results.

[0016] In the present invention, by introducing the microporous expansion rate correction factor, quantitative compensation is performed on the content of the eluate during the detection by the gas chromatography-mass spectrometry instrument, further improving the measurement accuracy. Through this innovative correction mechanism, the influence of the microporous structure on the eluate release kinetics can be effectively eliminated, thereby ensuring the accurate calculation of the eluate content. Description of the Drawings

[0017] To more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only those of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 Schematic diagram of the detection method for the content of the eluate of the polyvinyl alcohol film in the embodiment of the present invention; Figure 2 Schematic diagram of the alternating pressure field dynamic extraction method in the embodiment of the present invention. Detailed implementation manners

[0019] The present invention will be described in detail below in conjunction with the drawings and specific embodiments. At the same time, it should be noted here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments. For some well-known technologies, those skilled in the art can also adopt other alternative methods for implementation; moreover, the drawing part is only for more specifically describing the embodiments, and is not intended to specifically limit the present invention.

[0020] It should be noted that in the specification, when referring to "an embodiment", "embodiments", "exemplary embodiments", "some embodiments", etc., it indicates that the described embodiments may include specific features, structures or characteristics, but not necessarily every embodiment includes such specific features, structures or characteristics. Additionally, when combining embodiments to describe specific features, structures or characteristics, implementing such features, structures or characteristics in combination with other embodiments (whether explicitly described or not) should be within the knowledge scope of those skilled in the relevant art.

[0021] Generally, the terms can be understood at least in part from their use in the context. For example, at least in part depending on the context, the term "one or more" used herein can be used to describe any feature, structure or characteristic in a singular sense, or can be used to describe a combination of features, structures or characteristics in a plural sense. Additionally, the term "based on" can be understood as not necessarily intended to convey a set of exclusive factors, but rather, at least in part depending on the context, allowing for the existence of other factors that may not be explicitly described.

[0022] Embodiment 1 As Figure 1 - Figure 2 shown, a detection method for determining the content of the eluate of the polyvinyl alcohol film based on gas chromatography includes the following steps: S1: Place the polyvinyl alcohol film sample in a humidity control box for equilibration to obtain a humidity homogenized film; S2: Place the humidity homogenized film in liquid nitrogen vapor for rapid cooling to a predetermined temperature, and perform brittle fracture treatment using a shock wave crusher to obtain spherical-like fragments; S3: Transfer the spheroidal fragments to a microwave drying device for drying treatment to obtain dehydrated and activated fragments; S4: Perform low-temperature plasma surface treatment on the dehydrated and activated fragments to increase the surface micropore expansion rate; S5: Mix the treated fragments with an ethanol-n-hexane mixture in a predetermined ratio and perform dynamic extraction in an alternating pressure field to obtain an extract; S6: Perform a three-stage separation treatment on the extract to remove large particulate matter and colloidal substances to obtain a clarified test solution; S7: Add a derivatization reagent to the clarified test solution to carry out a derivatization reaction to convert the eluate into a volatile derivative to obtain a derivatized solution; S8: Inject the derivatized solution into a gas chromatography-mass spectrometry instrument for detection and perform quantitative compensation on the detection results based on the micropore expansion rate correction factor, and finally obtain the content of the eluate of the polyvinyl alcohol film.

[0023] S1 specifically includes: S11: Place the polyvinyl alcohol film sample in a humidity control box with the temperature of the humidity control box set at 23°C and the relative humidity at 40%; S12: Keep the film sample in the set temperature and humidity control box for 24 hours to balance until the moisture in the sample is evenly distributed to obtain a humidity homogenized film.

[0024] S2 specifically includes: S21: Place the humidity homogenized film sample in liquid nitrogen vapor for quenching treatment to quench the film temperature to -50°C; S22: Transfer the quenched film sample to a shock wave crusher and set the impact pressure of the shock wave crusher at 0.4 MPa; S23: Start the shock wave crusher for brittle fracture treatment for 2.5 minutes until spheroidal fragments with a particle size of 0.5 mm are obtained.

[0025] S3 specifically includes: S31: Transfer the spheroidal fragments to a microwave drying device and ensure that the fragments are evenly distributed in the drying chamber; S32: Set the vacuum degree of the microwave drying device at 10 Pa; S33: Set the working frequency of the microwave drying device at 2450 MHz and start microwave radiation for drying treatment; S34: Continuously dry the fragments under the set vacuum degree and frequency until the water content of the fragments is lower than 0.05% to obtain dehydrated and activated fragments.

[0026] S4 specifically includes: S41: Place the dehydrated and activated fragments in a low-temperature plasma reaction chamber, and set the reaction chamber temperature to -25°C; S42: Introduce argon gas into the reaction chamber as the plasma atmosphere, and adjust the argon gas flow rate to 12 sccm; S43: Set the power of the low-temperature plasma source to 200 W, and start the plasma source for surface treatment; S44: Maintain the plasma treatment for 5 minutes until the micropore expansion rate on the fragment surface reaches 18%.

[0027] S5 specifically includes: S51: Mix the treated fragments with an ethanol-n-hexane mixture at a mass-to-volume ratio of 1:28 to form mixture A, where the volume ratio of the ethanol-n-hexane mixture is 3:1; S52: Transfer mixture A to an alternating pressure field device, set the initial positive pressure of the alternating pressure field to 0.1 MPa, and maintain this pressure for 10 - 15 minutes; S53: Switch the alternating pressure field to negative pressure, set the negative pressure to -0.08 MPa, and maintain the negative pressure state for 7 minutes. Through the treatment of the alternating pressure field, the dissolved substances in the extract are gradually released to obtain the extract.

[0028] S6 specifically includes: S61: Transfer the extract to a centrifuge, set the centrifugation speed to 9000 r / min, and the centrifugation time to 5 - 10 minutes to remove large particles; S62: Cross-flow filter the centrifuged extract through a 0.22 μm ceramic membrane to remove fine particles and suspended matter; S63: Treat the filtered extract through a molecular sieve adsorption column to remove colloidal substances and obtain a clarified test solution. The pore size of the molecular sieve is controlled at 4 Å.

[0029] S7 specifically includes: S71: Add a silylation derivatization reagent to the clarified test solution. The derivatization reagent is selected from N,O-bis(trimethylsilyl)acetamide, and the addition amount is 4% of the volume of the test solution; S72: Place the test solution added with the derivatization reagent in a temperature control device, set the reaction temperature to 60°C, and maintain the reaction temperature; S73: Carry out the derivatization reaction, and the reaction time is 15 minutes; S74: After the reaction is completed, obtain volatile derivatives to form a derivatized solution, and prepare for subsequent analysis.

[0030] S8 specifically includes: S81: Inject the derivatized solution into a gas chromatography-mass spectrometry (GC-MS) instrument through an injector, set the column temperature of the chromatograph to 55°C, and adjust the gas flow rate to 1.2 mL / min; S82: Set the temperature programming of the gas chromatography - mass spectrometry (GC - MS) instrument to increase the column temperature from 50 °C to 250 °C at a heating rate of 7 °C / min; S83: Detect using the selective ion monitoring mode and record the mass spectrometry data; S84: Based on the microporous expansion rate correction factor of the fragment surface, perform quantitative compensation on the detection results of the gas chromatography - mass spectrometry instrument, and calculate the content of the eluate of the polyvinyl alcohol film according to the compensated detection results to obtain the final result.

[0031] S84 specifically includes: S841: According to the detection results of the gas chromatography - mass spectrometry instrument, obtain the peak area of the eluate, denoted as ; S842: Calculate the microporous expansion rate correction factor , the formula is, , where the expansion rate is the microporous expansion rate of the fragment after surface treatment in S4; S843: Calculate the content of the eluate of the polyvinyl alcohol film: .

[0032] Example 2 S1: Place the polyvinyl alcohol film sample in a humidity control chamber, set the temperature to 22 °C and the relative humidity to 38%, and maintain equilibrium for 24 hours until the moisture is evenly distributed to obtain a humidity - homogenized film; S2: Quench the humidity - homogenized film in liquid nitrogen vapor so that the film temperature is quenched to - 50 °C; then, transfer the quenched film sample to a shock - wave crusher, set the impact pressure to 0.3 MPa, start the crusher for brittle fracture treatment for 2 minutes to obtain spherical - like fragments with a particle size of 0.3 mm; S3: Transfer the spherical - like fragments to a microwave drying device to ensure even distribution of the fragments, set the vacuum degree to 10 Pa and the working frequency to 2450 MHz, start microwave radiation for drying treatment, and continuously dry until the water content of the fragments is less than 0.05% to obtain dehydrated and activated fragments; S4: Place the dehydrated and activated fragments in a low - temperature plasma reaction chamber, set the temperature to - 20 °C, introduce an argon atmosphere with a flow rate of 10 sccm, set the low - temperature plasma source power to 180 W, and perform surface treatment for 5 minutes with a surface microporous expansion rate reaching 15%; S5: Mix the treated fragments with an ethanol - n - hexane mixture at a mass - to - volume ratio of 1:25 to form mixture A; transfer mixture A to an alternating pressure field device, set the initial positive pressure to 0.1 MPa and maintain for 10 minutes, then switch to a negative pressure of - 0.08 MPa and maintain for 5 minutes to obtain an extract; S6: Transfer the extract to a centrifuge, set the centrifugation speed at 8000 r / min, centrifuge for 5 minutes to remove large particles; remove fine particles and suspended matter by cross-flow filtration through a 0.22-μm ceramic membrane; treat with a molecular sieve adsorption column with a pore size of 3 Å to obtain a clarified test solution. S7: Add dimethyldichlorosilane derivatization reagent to the clarified test solution, with the addition amount being 3% of the volume of the test solution, set the reaction temperature at 50 °C, and maintain for 10 minutes to obtain volatile derivatives and form a derivatized solution. S8: Inject the derivatized solution into a gas chromatography-mass spectrometry (GC-MS) instrument, set the column temperature at 50 °C, the gas flow rate at 1.0 mL / min, and the temperature programming as rising from 50 °C to 250 °C at a rate of 5 °C / min; perform detection using the selective ion monitoring mode and record the mass spectrometry data; perform quantitative compensation based on the surface micropore expansion rate correction factor.

[0033] The specific calculation process is as follows: 1. According to the detection results, the peak area detected by gas chromatography is ; 2. According to the surface micropore expansion rate, the correction factor ; 3. The volume of the sample dissolution solution ; 4. Use the formula to calculate the content of the eluate: .

[0034] Example 3 S1: Place the polyvinyl alcohol film sample in a humidity control box, set the temperature at 24 °C and the relative humidity at 42%, and maintain equilibrium for 24 hours until the moisture is evenly distributed to obtain a humidity homogenized film. S2: Place the humidity homogenized film in liquid nitrogen vapor for quenching treatment, and quickly cool the film temperature to -50 °C; then, transfer the quenched film sample to a shock wave crusher, set the impact pressure at 0.5 MPa, start the crusher for brittle fracture treatment, and the treatment time is 3 minutes to obtain spherical fragments with a particle size of 0.8 mm. S3: Transfer the spherical fragments to a microwave drying device, ensure that the fragments are evenly distributed, set the vacuum degree at 10 Pa and the working frequency at 2450 MHz, start microwave radiation for drying treatment, and continuously dry until the water content of the fragments is lower than 0.05% to obtain dehydrated and activated fragments. S4: Place the dehydrated and activated fragments in a low-temperature plasma reaction chamber, set the temperature at -30 °C, introduce an argon atmosphere with a flow rate of 15 sccm, set the power of the low-temperature plasma source at 220 W, perform surface treatment for 8 minutes, and the surface micropore expansion rate reaches 20%. S5: Mix the processed fragments with an ethanol - n - hexane mixture at a mass - to - volume ratio of 1:30 to form mixture A; transfer mixture A to an alternating pressure field device, set the initial positive pressure to 0.1 MPa, maintain for 15 minutes, then switch to a negative pressure of - 0.08 MPa and maintain for 10 minutes to obtain an extract. S6: Transfer the extract to a centrifuge, set the centrifugation speed to 10000 r / min, centrifuge for 10 minutes to remove large particles; remove fine particles and suspended matter by cross - flow filtration through a 0.22 - μm ceramic membrane; treat with a molecular sieve adsorption column with a pore size of 5 Å to obtain a clarified test solution. S7: Add an N,O - bis(aminodimethylsilyl) derivative reagent to the clarified test solution, with the addition amount being 5% of the volume of the test solution, set the reaction temperature to 70 °C, and maintain for 20 minutes to obtain volatile derivatives and form a derivatized solution. S8: Inject the derivatized solution into a gas chromatography - mass spectrometry (GC - MS) instrument, set the column temperature to 60 °C, the gas flow rate to 1.5 mL / min, the temperature programming to increase from 50 °C to 250 °C at a rate of 10 °C / min; perform detection in the selective ion monitoring mode and record the mass spectrometry data; perform quantitative compensation based on the surface micropore expansion rate correction factor.

[0035] The specific calculation process is as follows: 1. According to the detection results, the peak area detected by gas chromatography is ; 2. According to the surface micropore expansion rate, the correction factor ; 3. The volume of the sample dissolution solution ; 4. Use the formula to calculate the content of the dissolved substance: ;

[0036] Table 1 Comparison of experimental data As can be seen from Table 1 above, the content of the dissolved substance in Example 1 is 0.6925 mg / g, which is at the middle level among the three; the surface micropore expansion rate of Example 3 (20%) is the highest, while that of Example 2 (15%) is the lowest, indicating that the surface treatment effect of Example 3 is better; in terms of processing time, 2.5 minutes of Example 1 is the best, slightly higher than the processing times of other examples; in terms of particle size, the particle size of Example 1 is 0.5 mm, between the other two; in terms of centrifugation speed, there is a large difference between Example 1 and Example 3, indicating that the processing intensities of the two are different; the gas flow rate and reaction temperature are moderately selected in Example 1. Generally speaking, Example 1 has better balance performance in terms of the content of the dissolved substance, particle size control, and processing time, and is the best example.

[0037] The present invention covers any alternatives, modifications, equivalent methods, and solutions made within the spirit and scope of the present invention. For the public to have a thorough understanding of the present invention, specific details are elaborated in the following preferred embodiments of the present invention. However, those skilled in the art can fully understand the present invention even without the description of these details. Additionally, well-known methods, processes, procedures, components, and circuits, etc. are not described in detail to avoid unnecessary confusion to the essence of the present invention.

[0038] The above description is only a preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A detection method for determining the content of eluate in a polyvinyl alcohol film based on gas chromatography, characterized in that, It includes the following steps: S1: Place the polyvinyl alcohol film sample in a humidity control chamber for equilibration to obtain a humidity-homogenized film; S2: Quench the humidity-homogenized film in liquid nitrogen vapor to a predetermined temperature and perform brittle fracture treatment using a shock wave crusher to obtain spherical-like fragments; S3: Transfer the spherical-like fragments to a microwave drying device for drying treatment to obtain dehydrated and activated fragments; S4: Perform low-temperature plasma surface treatment on the dehydrated and activated fragments to increase their surface micropore expansion rate; S5: Mix the treated fragments with an ethanol-n-hexane mixture in a predetermined ratio and perform dynamic extraction in an alternating pressure field to obtain an extract; S6: Perform three-stage separation treatment on the extract to remove large particulate matter and colloidal substances to obtain a clarified test solution; S7: Add a derivatization reagent to the clarified test solution to carry out a derivatization reaction to convert the dissolved substances into volatile derivatives to obtain a derivatized solution; S8: Inject the derivatized solution into a gas chromatography-mass spectrometry (GC-MS) instrument for detection and perform quantitative compensation on the detection results based on the micropore expansion rate correction factor to finally obtain the content of the dissolved substances in the polyvinyl alcohol film.

2. The detection method for determining the content of the extractables in the polyvinyl alcohol film based on gas chromatography according to claim 1, characterized in that The specific steps of S1 include: S11: Place the polyvinyl alcohol film sample in a humidity control chamber with the temperature of the humidity control chamber set at 22°C to 24°C and the relative humidity at 38% to 42%; S12: Keep the film sample in the set temperature and humidity control chamber for 24 hours until the moisture in the sample is evenly distributed to obtain a humidity-homogenized film.

3. The detection method for determining the content of the extractables in the polyvinyl alcohol film based on gas chromatography according to claim 1, wherein, The specific steps of S2 include: S21: Place the humidity-homogenized film sample in liquid nitrogen vapor for quenching treatment to quench the film temperature to -50°C; S22: Transfer the quenched film sample to a shock wave crusher and set the impact pressure of the shock wave crusher at 0.3 MPa to 0.5 MPa; S23: Start the shock wave crusher for brittle fracture treatment for 2 to 3 minutes until spherical-like fragments with a particle size of 0.3 mm to 0.8 mm are obtained.

4. The detection method for determining the content of the eluate of the polyvinyl alcohol film based on gas chromatography according to claim 1, wherein, The specific steps of S3 include: S31: Transfer the spherical-like fragments to a microwave drying device and ensure that the fragments are evenly distributed in the drying chamber; S32: Set the vacuum degree of the microwave drying device at 10 Pa; S33: Set the working frequency of the microwave drying device at 2450 MHz and start microwave radiation for drying treatment; S34: Continuously dry the fragments under the set vacuum degree and frequency until the water content of the fragments is lower than 0.05% to obtain dehydrated and activated fragments.

5. The detection method for determining the content of the eluate of the polyvinyl alcohol film based on gas chromatography according to claim 1, wherein The specific steps of S4 include: S41: Place the dehydrated and activated fragments in a low-temperature plasma reaction chamber and set the reaction chamber temperature at -20°C to -30°C; S42: Introduce argon gas into the reaction chamber as a plasma atmosphere and adjust the argon gas flow rate at 10 sccm to 15 sccm; S43: Set the power of the low-temperature plasma source at 180 - 220 W and start the plasma source for surface treatment; S44: Maintain the plasma treatment for 3 - 8 minutes until the surface micropore expansion rate of the fragments reaches 15% to 20%.

6. The detection method for determining the content of eluate of polyvinyl alcohol film based on gas chromatography according to claim 1, characterized in that The specific steps of S5 include: S51: Mix the processed fragments with an ethanol-n-hexane mixture at a mass-to-volume ratio of 1:25 to 1:30 to form mixture A, where the volume ratio of the ethanol-n-hexane mixture is 3:1; S52: Transfer mixture A to an alternating pressure field device, set the initial positive pressure of the alternating pressure field to 0.1 MPa, and maintain this pressure for 10 - 15 minutes; S53: Switch the alternating pressure field to negative pressure, set the negative pressure to -0.08 MPa, and maintain the negative pressure state for 5 - 10 minutes. Through the treatment of the alternating pressure field, the dissolved substances in the extract are gradually released to obtain the extract.

7. The detection method for determining the content of eluate in a polyvinyl alcohol film based on gas chromatography according to claim 1, characterized in that, The specific steps of S6 are as follows: S61: Transfer the extract to a centrifuge, set the centrifugation speed to 8000 - 10000 r / min, and the centrifugation time to 5 - 10 minutes to remove large particles; S62: Cross-flow filter the centrifuged extract through a 0.22 μm ceramic membrane to remove fine particles and suspended matter; S63: Treat the filtered extract through a molecular sieve adsorption column to remove colloidal substances to obtain a clear test solution, and the pore size of the molecular sieve is controlled between 3 Å and 5 Å.

8. The detection method for determining the content of eluate of polyvinyl alcohol film based on gas chromatography according to claim 1, wherein The specific steps of S7 are as follows: S71: Add a silylation derivatization reagent to the clear test solution. The derivatization reagent is selected from N,O-bisaminodimethylsilane or dimethyldichlorosilane, and the addition amount is 3% to 5% of the volume of the test solution; S72: Place the test solution added with the derivatization reagent in a temperature control device, set the reaction temperature to 50 - 70 °C, and maintain the reaction temperature; S73: Carry out the derivatization reaction, and the reaction time is 10 - 20 minutes; S74: After the reaction is completed, volatile derivatives are obtained to form a derivatized solution.

9. The detection method for determining the content of the eluate of the polyvinyl alcohol film based on gas chromatography according to claim 1, characterized in that, The specific steps of S8 are as follows: S81: Inject the derivatized solution into a gas chromatography-mass spectrometry (GC-MS) instrument through an injector, set the column temperature of the gas chromatography to 50 °C to 60 °C, and adjust the gas flow rate to 1.0 mL / min to 1.5 mL / min; S82: Set the temperature programming of the GC-MS instrument to increase the column temperature from 50 °C to 250 °C at a heating rate of 5 - 10 °C / min; S83: Detect using the selective ion monitoring mode and record the mass spectrometry data; S84: Based on the correction factor of the micropore expansion rate on the fragment surface, quantitatively compensate the detection results of the GC-MS instrument, and calculate the content of the dissolved substances in the polyvinyl alcohol film according to the compensated detection results to obtain the final result.

10. The detection method for determining the content of the eluate of a polyvinyl alcohol film based on gas chromatography according to claim 9, wherein, The specific steps of S84 are as follows: S841: Obtain the peak area of the extractables based on the test results of the gas chromatography-mass spectrometry, denoted as ; S842: Calculate the correction factor for the micropore expansion rate , and the formula is , where the expansion rate is the micropore expansion rate of the fragments after surface treatment in S4; S843: Calculate the content of the extractables of the polyvinyl alcohol film , the formula is: , where is the content of the extractables of the polyvinyl alcohol film; is the peak area detected by gas chromatography; F is the correction factor for the micropore expansion rate; is the volume of the sample dissolution solution.

Images