CN114720610B - Analysis method of volatile compounds in walnut oil - Google Patents
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Abstract
The invention provides an analysis method of volatile compounds in walnut oil, which comprises the following steps: (1) The method comprises the steps of adopting a dynamic headspace sample preparation mode to adsorb volatile compounds in walnut oil, wherein an adsorption material is an electrostatic spinning fiber membrane, and the electrostatic spinning fiber membrane is selected from a polystyrene electrostatic spinning fiber membrane, an acrylic resin electrostatic spinning fiber membrane or a polystyrene-acrylic resin blended electrostatic spinning fiber membrane; (2) Carrying out thermal desorption on the adsorbed volatile compounds to obtain enriched volatile compounds; (3) The enriched volatile compounds were analyzed using a gas chromatograph-sniffer-mass spectrometer. According to the analysis method disclosed by the invention, the electrostatic spinning fiber membrane is used as an adsorption material, so that volatile compounds, especially flavor compounds, in walnut oil are effectively extracted, the operation is simple and convenient, and the adsorption efficiency is high.
Description
Technical Field
The invention relates to the technical field of food analysis, in particular to a method for analyzing volatile compounds in walnut oil.
Background
Walnut, named Qiang Guo, juglans regia, belongs to the genus Juglans of the family Juglandaceae. The walnut has rich resources, various varieties and high cultivation area and yield. Because of the long history of walnut cultivation and utilization and wide popularity, people can know and attach considerable importance to the nutrition and health care functions and economic and ecological benefits of the walnut. Along with the continuous improvement of the cultural living standard of people, besides taking walnuts as instant foods, the demand for the walnut finish products is also increasing, wherein walnut oil is one of the most representative products.
The walnut oil is an oil product with high added value extracted from walnut kernels, and is widely applied to the fields of food and health care. The walnut oil has high nutritive value, and the fatty acid composition of the walnut oil mainly comprises unsaturated fatty acids such as linoleic acid, oleic acid, linolenic acid and the like, the content of the unsaturated fatty acids is about 90%, and the walnut oil can effectively reduce cholesterol and prevent and treat coronary heart disease, arteriosclerosis and myocardial infarction. In addition to good fatty acid content, minor components in walnut oil, such as polyphenols, tocopherols, squalene and phytosterols, also have important nutritional values. The walnut polyphenol can inhibit the activity of low-density lipoprotein oxidation; while tocopherols have antiproliferative and anti-inflammatory effects on cancer; squalene is used as skin emollient; phytosterols may interfere with intestinal cholesterol absorption and reduce the risk of coronary heart disease. In addition, walnut oil is used in cosmetics, sesame oil and soap production. Walnut oil is also commonly used in industry as a high grade lubricant and feedstock.
The aroma quality is the most important sensory quality of the vegetable oil, is not only an important evaluation index of the quality of the walnut oil, but also is a primary standard for selecting products by consumers, so that research on the inherent smell of the walnut oil is very important. Because of the complexity of the food matrix, selecting different separation and extraction techniques for different samples is critical to the accuracy of the analysis result, so that different aroma extraction methods are required to extract volatile compounds in the food to the greatest extent, then the next analysis is performed, and the commonly used extraction methods of volatile flavor substances are mainly divided into two main types: solvent extraction techniques and headspace adsorption techniques. Solvent Assisted Flavor Evaporation (SAFE) is the most commonly used solvent extraction technique, and has high volatile recovery rate and low temperature and high boiling point to realize the separation of volatile compounds, and is widely applied at present.
The headspace adsorption technology is generally divided into two sample preparation methods of static headspace and dynamic headspace, and solid-phase micro-extraction (SPME) is the most commonly used static headspace adsorption technology, and is a solvent-free extraction technology with sampling, concentration and sample injection. The method has the advantages of easy handling, portability, strong adsorptivity, high extraction rate, few required samples, low detection limit, better repeatability under certain strict conditions and the like, and becomes one of the most effective and most used methods for extracting the aroma substances at present. The dynamic headspace sample preparation (dynamic headspace sampling, DHS) is to purge the surface of a sample in a closed container by using inert gas (such as nitrogen), enrich volatile compounds in the sample headspace by using a trapping object, volatilize the compounds by using a thermal desorption technology, and perform component analysis by using a gas chromatograph or a gas chromatograph-mass spectrometer. The common trapping material is Tenax TA adsorption column, wherein the filler is a polymer adsorbent, which can effectively adsorb odor volatile matters. In the last decade, many new materials, especially nanostructured materials, have been studied as adsorbents for gaseous organic molecules, such as the enrichment of volatile substances by using thin films as the adsorbent material, which is mainly distinguished from the traditional adsorption by the use of an extraction phase with a larger volume and a larger specific surface area, which can improve the adsorption sensitivity without sacrificing the sampling time. In addition, studies have demonstrated that adsorbents based on electrospun nanofibers can also be used to extract organic matter, and that the felt-like and fibrous structures of nanofibers provide better mechanical properties, larger specific surface area and pore structure for their use as adsorbent materials.
At present, the extraction mode of volatile substances is more traditional and single, along with the progress of technology and the staggered development of multiple disciplines, the development of novel adsorption materials is urgently needed at present, so that the extraction of the volatile substances can be more effective, rapid and accurate analysis technology.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide an analysis method for volatile compounds in walnut oil, which adopts an electrostatic spinning fiber membrane as an adsorption material to effectively adsorb and extract the volatile compounds in the walnut oil for analysis.
In order to achieve the above objective, the present invention provides a method for analyzing volatile compounds in walnut oil, comprising the following steps:
(1) The method comprises the steps of adopting a dynamic headspace sample preparation mode to adsorb volatile compounds in walnut oil, wherein an adsorption material is an electrostatic spinning fiber membrane, and the electrostatic spinning fiber membrane is selected from a polystyrene electrostatic spinning fiber membrane, an acrylic resin electrostatic spinning fiber membrane or a polystyrene-acrylic resin blended electrostatic spinning fiber membrane;
(2) Carrying out thermal desorption on the adsorbed volatile compounds to obtain enriched volatile compounds;
(3) The enriched volatile compounds were analyzed using a gas chromatograph-sniffer-mass spectrometer.
According to a specific embodiment of the present invention, preferably, the electrospun fiber film is used in an amount of 0.15 to 0.25% based on 100% of the mass of the walnut oil.
According to a specific embodiment of the present invention, preferably, the acrylic resin electrospun fiber film is an acrylic resin II electrospun fiber film.
According to a specific embodiment of the present invention, preferably, the polystyrene electrospun fiber film has a fiber diameter of 300 to 800nm.
According to a specific embodiment of the present invention, preferably, the acrylic electrospun fiber film has a fiber diameter of 200 to 400nm.
According to a specific embodiment of the present invention, preferably, the fiber diameter of the polystyrene-acrylic resin blend electrospun fiber membrane is 200 to 900nm.
According to a specific embodiment of the invention, preferably, an internal standard is further added to the walnut oil during dynamic headspace sampling, wherein the internal standard is selected from 2-methyl-3-heptanone. The 2-methyl-3-heptanone is not present in the walnut oil sample and the peak time does not mask volatile compounds in the sample.
According to a specific embodiment of the present invention, preferably, the dynamic headspace preparation includes a hatching program and an adsorption program, and the adsorption temperature is 50-60 ℃.
According to a specific embodiment of the invention, the incubation temperature is preferably 50-55℃and the equilibration time is 10-15min.
According to a specific embodiment of the present invention, preferably, the nitrogen flow rate at the time of adsorption is 20-25mL/min, and the nitrogen flow rate after the completion of adsorption is 10-12mL/min.
According to a specific embodiment of the present invention, it is preferable that the thermal desorption temperature is 240-250 ℃ and the thermal desorption time is 10-12min.
According to a specific embodiment of the present invention, preferably, step (2) further comprises: before the thermal desorption, the adsorbed volatile compounds are cryofocused in a solvent-venting mode.
According to a specific embodiment of the invention, the cold trap temperature is preferably-78 ℃ to-80 ℃ and the equilibration time is 0.5-1min.
According to a specific embodiment of the present invention, preferably, the gas chromatography conditions are as follows:
chromatographic column: j & W DB-WAX quartz capillary column, 30m x 0.25mm x 0.25 μm;
heating program: the initial column temperature is 40 ℃, after the column temperature is kept for 2min, the temperature is increased to 75 ℃ at 5 ℃/min, then the column temperature is increased to 150 ℃ at 2 ℃/min, and finally the column temperature is increased to 230 ℃ at 7 ℃/min, and the column temperature is maintained for 2min; the temperature of the sample inlet is 230 ℃ and the temperature of the detector is 280 ℃; the carrier gas is nitrogen, and the flow rate is 3mL/min; no split flow is produced.
According to a specific embodiment of the present invention, preferably, the mass spectrometry conditions are as follows:
electron bombardment, electron energy of 70eV, transmission line temperature of 280 ℃, ion source temperature of 230 ℃, quadrupole temperature of 150 ℃, full scanning, mass scanning range of 50-350m/z and solvent delay of 5min.
According to a specific embodiment of the invention, the analysis is preferably performed in a semi-quantitative manner using an internal standard.
According to a specific embodiment of the present invention, preferably, the walnut oil is obtained by squeezing walnut kernels at a high temperature of 200-250 ℃.
In the analysis method of the present invention, volatile compounds refer to compounds in walnut oil that are detectable only by gas chromatography-mass spectrometry, and flavor compounds refer to compounds in volatile compounds that are detectable by sniffing detectors.
The technical scheme provided by the invention has the following beneficial effects:
(1) According to the analysis method, the electrostatic spinning fiber membrane is used as an adsorption material, so that the volatile compounds in the walnut oil are effectively extracted, the adsorption capacity is high, the adsorption efficiency is high, and the operation is simple and convenient;
(2) The analysis method of the invention adopts the electrostatic spinning fiber membrane as the adsorption material, expands the detection range of the volatile compounds, and particularly has wider sniffing detection range for the flavor compounds in the volatile compounds;
(3) The electrostatic spinning fiber membrane provided by the invention is simple to prepare and low in cost.
Drawings
FIG. 1 is a graph showing the comparison of the amounts of various volatile compounds adsorbed by four materials;
FIG. 2 is a comparison of the amount of odorous flavor compounds adsorbed by four materials;
figure 3 is a comparison of the total concentration of the four materials adsorbed to the odoriferous flavour compounds.
Detailed Description
The technical solution of the present invention will be described in detail below for a clearer understanding of technical features, objects and advantageous effects of the present invention, but should not be construed as limiting the scope of the present invention.
The experimental materials and instruments used in the examples of the present invention are as follows:
materials: a hot pressed walnut oil, 2-methyl-3 heptanone, a polystyrene electrostatic spinning fiber film (PS) (fiber diameter 300-800 nm), an acrylic resin II electrostatic spinning fiber film (AR II) (fiber diameter 200-400 nm), a polystyrene-acrylic resin II blended electrostatic spinning fiber film (PS-AR) (fiber diameter 200-900 nm) and a Tenax TA (2, 6-diphenyl furan porous polymer) adsorption column;
instrument: 20mL headspace glass sample bottle, thermal desorption tube, multipurpose sampler (MPS), dynamic headspace sample system (DHS), cooling injection-thermal desorption coupling system (CIS-TDU), gas chromatography-sniffing-mass spectrometer (GC-O-MS).
The hot pressed walnut oil used in the embodiment of the invention is prepared by the following steps: selecting walnut kernels with normal development and full fruits, cutting the walnut kernels, and then putting the cut walnut kernels into a preheated oil press for high-temperature squeezing at 200-250 ℃; centrifuging the obtained hot pressed oleum Juglandis at 12000r/min for 30min, packaging the supernatant in glass bottle, sealing, and storing at 4deg.C in dark place.
In the embodiment of the invention, the actual retention index (actual RI) is obtained by using a logarithmic interpolation method based on the retention time of adjacent normal paraffins on two sides of a substance to be detected on a chromatogram.
Example 1
The embodiment provides an analysis method of volatile compounds in walnut oil, which comprises the following steps:
1. enrichment of volatile compounds from hot pressed walnut oil
Accurately weighing 5.0g of hot pressed walnut oil into a 20mL headspace glass sample bottle, adding 1 mu L of 2-methyl-3 heptanone (0.816 mu g/. Mu.L) as an internal standard substance, sealing with a sealing film after capping to serve as an upper sample, and adopting a multipurpose sampler for sample injection.
Incubating the sample in a dynamic headspace sample preparation system at 55 ℃ and stirring speed of 500rpm for 10min; the sample was purged with 800mL of nitrogen at 25 ℃ at a nitrogen flow rate of 20mL/min, and the volatile compounds were captured using three thermal desorption tubes equipped with PS membranes; after the capturing is finished, carrying out dewatering and drying treatment on the thermal desorption tube by using 100mL of nitrogen at a flow rate of 10 mL/min; placing the thermal desorption tube in a cooling injection-thermal desorption coupling system (equipped with an inactive glass wool lining), freezing and focusing in a solvent emptying mode, balancing the cold trap temperature at-80 ℃ for 0.5min and maintaining for 0.1min; then, the temperature is raised to 250 ℃ at the speed of 10 ℃/min for thermal desorption, and the temperature is maintained for 10min, so that the sample gas enriched in the volatile compounds is obtained and transferred to a gas chromatography-sniffing-mass spectrometer.
2. Performing gas chromatography-sniffing-mass spectrometry
2.1 gas chromatography conditions
Chromatographic column: j & W DB-WAX quartz capillary column (30 m 0.25mm 0.25 μm);
heating program: the initial column temperature was 40℃and after 2min holding it was warmed to 75℃at 5℃per minute, then to 150℃at 2℃per minute, and finally to 230℃at 7℃per minute for 2min. The temperature of the sample inlet is 230 ℃ and the temperature of the detector is 280 ℃; the carrier gas is nitrogen, and the flow rate is 3mL/min; the split ratio is not split.
2.2 Mass Spectrometry Detector Condition
Electron Impact (EI), electron energy of 70eV, transmission line temperature of 280 ℃, ion source temperature of 230 ℃, quadrupole temperature of 150 ℃, scanning mode of full scanning, mass scanning range of 50-350m/z, and solvent delay of 5min.
2.3 sniffing detector conditions
Nitrogen was introduced into a vial containing distilled water at a rate of 20mL/min to supply water vapor to the sniffing port, maintaining the nasal cavity in a moist state during sniffing by the tester.
3. Quantitative analysis of volatile compounds in hot pressed walnut oil
The quantitative analysis of volatile compounds of the hot pressed walnut oil adopts an internal standard semi-quantitative mode. 2-methyl-3-heptanone (0.816. Mu.g/. Mu.L) is used as an internal standard, namely the mass concentration and the ratio of the peak area of the internal standard to the peak area of an unknown are calculated according to the following formula:
wherein f represents a correction factor, and the value is 1; a is that 1 、A x Represents the peak area of the internal standard substance and the peak area of the unknown substance respectively, ρ 1 、ρ x Representing the internal standard mass concentration and the unknown mass concentration, respectively.
Example 2
The present embodiment provides a method for analyzing volatile compounds in walnut oil, which is the same as that in embodiment 1, and differs only in that: the adsorption material in the thermal desorption tube of this embodiment is an arii film.
Example 3
The present embodiment provides a method for analyzing volatile compounds in walnut oil, which is the same as that in embodiment 1, and differs only in that: the adsorption material in the thermal desorption tube of the embodiment is a PS-AR film.
Comparative example 1
The comparative example provides a method for analyzing volatile compounds in walnut oil, which adopts a conventional adsorption material Tenax TA (2, 6-diphenyl furan porous polymer) and specifically comprises the following steps:
1. aging the adsorption material
The Tenax TA adsorption column is uniformly inserted into a Tube type temperature controller (TC 2, gerstel) in advance for aging treatment, wherein the aging temperature is 250 ℃, the nitrogen purging flow rate is 700mL/min, and the aging is carried out for 2 hours.
2. Enrichment of volatile compounds from hot pressed walnut oil
Accurately weighing 5.0g of hot pressed walnut oil into a 20mL headspace glass sample bottle, adding 1 mu L of 2-methyl-3 heptanone (0.816 mu g/. Mu.L) as an internal standard, capping, sealing with a sealing film to serve as an upper sample, and adopting a multipurpose sampler for sample injection.
Incubating the sample in a dynamic headspace sample preparation system at 55 ℃ and stirring speed of 500rpm for 10min; the sample is purged with 800mL of nitrogen at 25 ℃ at a nitrogen flow rate of 20mL/min, and the volatile compounds are captured by using a Tenax TA adsorption column; after the capturing is finished, carrying out dewatering and drying treatment on the Tenax TA adsorption column by using 100mL of nitrogen at a flow rate of 10 mL/min; placing the Tenax TA adsorption column in a cooling injection-thermal desorption coupling system (equipped with an inactive glass wool lining), freezing and focusing in a solvent emptying mode, balancing the cold trap temperature at-80 ℃ for 0.5min and maintaining for 0.1min; then, the temperature is raised to 250 ℃ at the speed of 10 ℃/min for thermal desorption, and the temperature is maintained for 10min, so that the sample gas enriched in the volatile compounds is obtained and transferred to a gas chromatography-sniffing-mass spectrometer.
3. Performing gas chromatography-sniffing-mass spectrometry
3.1 gas chromatography conditions
Chromatographic column: j & W DB-WAX quartz capillary column (30 m 0.25mm 0.25 μm);
heating program: the initial column temperature was 40℃and after 2min holding it was warmed to 75℃at 5℃per minute, then to 150℃at 2℃per minute, and finally to 230℃at 7℃per minute for 2min. The temperature of the sample inlet is 230 ℃ and the temperature of the detector is 280 ℃; the carrier gas is nitrogen, and the flow rate is 3mL/min; the split ratio is not split.
3.2 Mass Spectrometry Detector Condition
Electron Impact (EI), electron energy of 70eV, transmission line temperature of 280 ℃, ion source temperature of 230 ℃, quadrupole temperature of 150 ℃, scanning mode of full scanning, mass scanning range of 50-350m/z, and solvent delay of 5min.
3.3 sniffing detector conditions
Nitrogen was introduced into a vial containing distilled water at a rate of 20mL/min to supply water vapor to the sniffing port, maintaining the nasal cavity in a moist state during sniffing by the tester.
4. Quantitative analysis of volatile compounds in hot pressed walnut oil
The quantitative analysis of volatile compounds of the hot pressed walnut oil adopts an internal standard semi-quantitative mode. 2-methyl-3-heptanone (0.816. Mu.g/. Mu.L) is used as an internal standard, namely the mass concentration and the ratio of the peak area of the internal standard to the peak area of an unknown are calculated according to the following formula:
wherein f represents a correction factor, and the value is 1; a is that 1 、A x Represents the peak area of the internal standard substance and the peak area of the unknown substance respectively, ρ 1 、ρ x Representing the internal standard mass concentration and the unknown mass concentration, respectively.
Table 1 adsorption results of four materials on volatile compounds
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Table 2 sniffing results of flavor compounds adsorbed by four materials
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The measurement results of the concentration of volatile compounds in the hot pressed walnut oil and the sniffing results of examples 1 to 3 and comparative example 1 are shown in tables 1 and 2, respectively, and in table 2, S, M, W corresponds to three grades of strong, medium and weak sniffing strength, respectively. As can be seen from Table 1, for the same hot pressed walnut oil sample, tenax TA identified 93 volatile compounds altogether, PS membrane identified 50, AR-II membrane identified 73, and PS-AR membrane identified 68. Although Tenax TA is advantageous in terms of the identification number of volatile compounds, it is not so in terms of the kind of volatile compounds. The volatile compounds identified in table 1 can be divided into: alcohols, aldehydes, acids, ketones, esters, ethers, aromatics, hydrocarbons, and others, in 9 categories. Fig. 1 shows the amounts of volatile compounds adsorbed by Tenax TA and the three electrospun fiber membranes of examples 1-3, and it can be seen from fig. 1 that Tenax TA has a better effect of extracting aldehydes and ketones, and the electrospun fiber membrane of the present invention has a better effect of enriching volatile compounds in hot pressed walnut oil, and it is also apparent from table 1 that the concentration of volatile compounds identified by the electrospun fiber membrane adsorption material of the present invention is greater, and that the concentration of volatile compounds can even reach about 10 times of the adsorption amount of Tenax TA.
While AR II and PS-AR films can be enriched in more acids, ethers, hydrocarbons such as 2-butanoic acid (baking flavor), (E) -2-nonenoic acid (fat, oil flavor), ethylene glycol phenyl ether (balsam, cinnamon flavor), and styrene (balsam, oil flavor), all of which have good oil flavor profile, contribute to the rich flavor profile of the hot pressed walnut oil, but which are not detected when adsorbed with Tenax TA. Therefore, the electrostatic spinning fiber membrane adsorption material has a certain utilization value for identifying and analyzing the flavor profile composition of the hot pressed walnut oil.
More importantly, the aroma quality is the most important sensory quality of the vegetable oil, is not only an important evaluation index of the quality of the walnut oil, but also a primary standard for selecting products by consumers, and not all volatile compounds have outstanding contribution to the aroma composition of the hot pressed walnut oil, so that the sniffing result is an important evaluation standard for identifying whether an extraction method is good or not. According to the invention, part of the volatile compounds which can be smelled and identified are used as flavor compounds, 16 flavor compounds are smelled by a Tenax TA adsorption column according to the smelling results shown in table 2, 21 are smelled by a PS film, 35 are smelled by an AR II film, and 28 are smelled by a PS-AR film. The three electrospun fiber membranes of examples 1-3 have better flavor compound adsorption properties, in combination with the amount of the four materials shown in fig. 2 that adsorb the various odorous flavor compounds. And it can also be seen from Table 2 that the concentration of the compounds detected by co-adsorption of Tenax TA, PS film, AR II film or PS-AR film in Tenax TA is much lower than that of the electrospun fiber film of the present invention, which is also a part of the important reason for the weak smell of Tenax TA. In addition, according to the extracted 9 volatile compounds, the total concentration of each substance in each flavor compound identified by sniffing is compared, and as can be clearly seen in fig. 3, the electrostatic spinning fiber membrane adsorption material has a certain advantage in the adsorption efficiency of the flavor compounds. In conclusion, based on the sniffing result, the electrostatic spinning fiber membrane is applied to extraction of flavor compounds of the hot pressed walnut oil, and is superior to the conventional Tenax TA material.
It should be understood that the foregoing examples of the present invention are provided merely for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention, and that various other changes and modifications may be made therein by one skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims.
Claims (8)
1. An analysis method of volatile compounds in walnut oil comprises the following steps:
(1) The method comprises the steps of adopting a dynamic headspace sample preparation mode to adsorb volatile compounds in walnut oil, wherein an adsorption material is an electrostatic spinning fiber membrane, and the electrostatic spinning fiber membrane is selected from a polystyrene electrostatic spinning fiber membrane, an acrylic resin electrostatic spinning fiber membrane or a polystyrene-acrylic resin blended electrostatic spinning fiber membrane;
when the dynamic headspace is used for preparing a sample, an internal standard substance is also added into the walnut oil, and the internal standard substance is selected from 2-methyl-3-heptanone;
the dynamic headspace sample preparation comprises a hatching program and an adsorption program, wherein the hatching temperature is 50-55 ℃, and the balancing time is 10-15min; the adsorption temperature is 50-60 ℃, the nitrogen flow rate during adsorption is 20-25mL/min, and the nitrogen flow rate after the adsorption is completed is 10-12mL/min;
(2) Freezing and focusing the adsorbed volatile compounds in a solvent emptying mode, wherein the cold trap temperature is between-78 ℃ and-80 ℃ and the equilibrium time is between 0.5 and 1min; then, carrying out thermal desorption on the adsorbed volatile compounds, wherein the thermal desorption temperature is 240-250 ℃, and the thermal desorption time is 10-12min, so as to obtain enriched volatile compounds;
(3) Analyzing the enriched volatile compounds by using a gas chromatograph-sniffer-mass spectrometer;
wherein, the gas chromatography conditions are as follows:
chromatographic column: j & W DB-WAX quartz capillary column, 30m x 0.25mm x 0.25 μm;
heating program: the initial column temperature is 40 ℃, after the column temperature is kept for 2min, the temperature is increased to 75 ℃ at 5 ℃/min, then the column temperature is increased to 150 ℃ at 2 ℃/min, and finally the column temperature is increased to 230 ℃ at 7 ℃/min, and the column temperature is maintained for 2min; the temperature of the sample inlet is 230 ℃ and the temperature of the detector is 280 ℃; the carrier gas is nitrogen, and the flow rate is 3mL/min; not split;
the mass spectrometry conditions were as follows:
electron bombardment, electron energy of 70eV, transmission line temperature of 280 ℃, ion source temperature of 230 ℃, quadrupole temperature of 150 ℃, full scanning, mass scanning range of 50-350m/z and solvent delay of 5min.
2. The analysis method according to claim 1, wherein the electrospun fiber membrane is used in an amount of 0.15 to 0.25% based on 100% of the walnut oil.
3. The analytical method according to claim 2, wherein the acrylic electrospun fiber membrane is an acrylic II electrospun fiber membrane.
4. The analytical method according to claim 1, wherein the polystyrene electrospun fiber membrane has a fiber diameter of 300-800nm.
5. The analysis method according to claim 1, wherein the fiber diameter of the acrylic electrospun fiber film is 200-400nm.
6. The analysis method according to claim 1, wherein the fiber diameter of the polystyrene-acrylic resin blend electrospun fiber membrane is 200-900nm.
7. The assay of claim 1, wherein the assay is performed semi-quantitatively by an internal standard.
8. The analytical method according to claim 1, wherein the walnut oil is obtained by squeezing walnut kernels at a high temperature of 200-250 ℃.
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