Analysis method for detecting bromophenol flavor substances in seafood seasoning

Abstract

The invention discloses an analysis method for detecting bromophenol flavor substances in seafood condiments, and belongs to the technical field of food detection. A metal organic framework material (MIL-101-Cr) is prepared through a hydrothermal synthesis method, and the metal organic framework material (MIL-101-Cr) is used as an adsorbent to manufacture a solid phase extraction (SPE) column and is used for separating and enriching bromophenol flavor substances (BPs). Under optimized SPE (Solid Phase Extraction) conditions, a gas chromatography-mass spectrometry technology is combined, and an analysis method for detecting four BPs (4-bromophenol, 2, 4-dibromophenol, 2, 6-dibromophenol and 2, 4, 6-tribromophenol) is established. The method has good linearity (R2 is greater than or equal to 0.996), low detection limit (1.3-5.7 ng.L <-1 >) and high precision (1.5-8.3%, n = 6). The method is applied to detection of seafood condiments such as oyster sauce, seafood soy sauce and the like, and the detected contents of 4-bromophenol in the seafood soy sauce and oyster sauce are 57 ng.kg <-1 > and 63 ng.kg <-1 > respectively. Through low, medium and high standard addition recovery experiments, the recovery rate is measured to be 81.2-103.4%.

Description

Technical Field

[0001] The present invention belongs to the technical field of food detection, and particularly relates to an analytical method for detecting bromophenol flavor substances in seafood condiments Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the overall understanding of the present invention, and is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art already known to those of ordinary skill in the art

[0003] Bromophenol flavor compounds (BPs) are a class of phenolic compounds containing bromine atoms, including 4-bromophenol, 2,4-dibromophenol, 2,6-dibromophenol, 2,4,6-tribromophenol, etc. The content of BPs plays a crucial role in the flavor quality of products and has attracted much attention in the food field. Especially in seafood condiments, as one of the key flavor components, the content of BPs directly affects the flavor intensity and product quality of the products. Research shows that appropriate amounts of BPs can endow foods with unique aromas or tastes and enhance the sensory attractiveness of foods; however, excessive use of BPs may produce off-flavors, such as bitterness, astringency, or other abnormal flavors, thus having a negative impact on the overall quality of foods. This duality of flavors makes food quality control extremely challenging, and the accurate quantification of BPs has become a key factor affecting flavor regulation. Therefore, it is particularly important to develop a method for efficiently and accurately detecting the content of BPs in foods

[0004] Given the complex matrix interference (such as sugars, proteins, etc.) of food samples and the low content of BPs, it is difficult to directly detect BPs using analytical instruments. Developing new sample pretreatment technologies is an effective means to solve the above problems. As a commonly used pretreatment technology, solid-phase extraction (SPE) has the advantages of simple operation, high enrichment efficiency, and less solvent consumption. Currently, some commercial solid-phase extraction columns (such as Oasis HLB, Alumina N, and C18) have been applied to the field of sample pretreatment. However, these commercial adsorbents still have certain limitations in terms of selectivity and service life, which prompts researchers to continuously explore new adsorption materials. In recent years, various new adsorbent materials, such as carbon nanomaterials, graphene, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs), have been successfully applied to SPE and can, to a certain extent, make up for the deficiencies of commercial solid-phase extraction columns. Therefore, from the perspective of cost and efficiency, developing adsorbent materials with high enrichment efficiency and service life is the research focus of SPE technology

[0005] Metal-organic framework materials (MOFs) are a class of porous crystalline materials with a periodic and infinitely extended framework structure formed by inorganic metal ions (or metal clusters) as nodes or centers and organic ligands through self-assembly. They have characteristics such as high porosity, adjustable framework structure, multiple active sites, and easy functional modification, and are widely used in many fields such as chemical sensing, gas storage, and chemical separation.

[0006] MOFs have great application potential in the field of SPE. However, at present, the industry has not found MOFs and their detection methods that have good adsorption effects on various bromophenol flavor substances in seafood seasonings. Summary of the Invention

[0007] In order to solve the deficiencies of the prior art, the purpose of the present invention is to provide an analytical method for detecting bromophenol flavor substances in seafood seasonings. The present invention prepares a metal-organic framework material (MIL-101-Cr) by hydrothermal synthesis method, makes a solid-phase extraction (SPE) column with it as an adsorbent, and applies it to the separation and enrichment of bromophenol flavor substances (BPs) for the first time. Under optimized solid-phase extraction conditions, combined with gas chromatography-mass spectrometry (GC-MS) technology, an analytical method for detecting BPs is established. This method not only has a good linear relationship and low detection limit, but also shows excellent repeatability and accuracy. By applying this method to the detection of actual samples, the presence of BPs has been successfully detected in seafood seasonings such as oyster sauce and seafood soy sauce, providing strong technical support for the quality control and safety assessment of seafood seasonings. In addition, the developed SPE column is superior to commonly used commercial columns in terms of extraction efficiency and service life, and has certain commercial application prospects.

[0008] MOFs show good application potential in the field of sample pretreatment: (1) The large specific surface area can increase the contact between the material and the target, improving the extraction capacity and extraction efficiency; (2) The specific pore size and pore surface in the framework can use the size exclusion effect to match and enrich the target molecules; (3) The through pores with recognition functions and coordinatively unsaturated metal sites synergistically promote the combination of the target with the "selective active sites" located in the cavity; (4) MOFs are easy to be functionalized and modified, including functional conversions such as polarity-nonpolarity and hydrophobicity-hydrophilicity, which can all promote the selective extraction of target molecules.

[0009] In order to achieve the above purpose, the technical solution of the present invention is as follows:

[0010] In the first aspect, the present invention provides an analytical method for detecting bromophenol flavor substances in seafood seasonings, including the following steps:

[0011] Fill the metal-organic framework material into the solid-phase extraction column to prepare the solid-phase extraction column;

[0012] Using the pretreated seafood condiment as a sample, the sample is detected by a solid-phase extraction column and gas chromatography-mass spectrometry;

[0013] The metal-organic framework material is MIL-101-Cr.

[0014] In one or more embodiments, the bromophenol flavor substances include one or more of 4-bromophenol (also known as p-bromophenol, 4-BP), 2,4-dibromophenol (2,4-DBP), 2,6-dibromophenol (2,6-DBP), and 2,4,6-tribromophenol (2,4,6-TBP).

[0015] In one or more embodiments, the seafood condiment includes one or more of oyster sauce and seafood soy sauce.

[0016] In one or more embodiments, the MIL-101-Cr material is an octahedral crystal grain,

[0017] The MIL-101-Cr material is prepared by a hydrothermal method. The specific surface area of MIL-101-Cr is 400-800 m 2 / g, the pore size is 1-10 nm, preferably 1-5 nm.

[0018] In one or more embodiments, MIL-101-Cr is filled into a solid-phase extraction column (SPE), and both ends are sealed with gaskets. Before each extraction, the solid-phase extraction column is activated with 5-10 mL of methanol and 5-10 mL of water.

[0019] In one or more embodiments, the solid-phase extraction column is fixed on a solid-phase extraction device, and a connecting tube connects the solid-phase extraction column with the sample solution. The solid-phase extraction device is connected to a vacuum pump.

[0020] In one or more embodiments, the solid-phase extraction column is dried under the maximum negative pressure of the vacuum pump, the solid-phase extraction column is eluted with a desorbing solution, the eluate is collected and dried under a nitrogen stream at 25-35 °C, redissolved with methanol, ultrasonically treated for 0.5-5 min, then 0.1-0.3 mL of acetic anhydride and 0.01-0.1 mL of triethylamine are added for derivatization, and then the solution is shaken at 25-35 °C for 10-30 minutes, filtered through a 0.22 μm organic membrane and then detected by an instrument.

[0021] The desorbing solution includes one or more of methanol, dichloromethane, ethanol, ethyl acetate, and acetonitrile, preferably acetonitrile.

[0022] The volume of the desorbing solution is 2-10 mL, and can be 2 mL, 3 mL, 4 mL, 5 mL, 6 mL, 7 mL, 8 mL, 9 mL, 10 mL. Preferably 7-9 mL.

[0023] The filling amount of MIL-101-Cr is 40-60 mg, which can be 40, 45, 50, 55, 60, preferably 45-80 mg, and further preferably 50-60 mg.

[0024] In one or more embodiments, the pretreatment is as follows: a solvent is added to the seafood condiment to be tested, and after ultrasonic treatment and centrifugation, the supernatant is retained. An alcohol solvent is added to the lower precipitate, and after ultrasonic treatment and centrifugation, the supernatants are combined and dried under a nitrogen stream at 25-35 °C.

[0025] The solvent is acetonitrile-water or acetonitrile, wherein the volume ratio of acetonitrile-water is 1:1.

[0026] The alcohol solvent is methanol.

[0027] The ultrasonic time is 5-15 min, the centrifugation speed is 5000-15000 rpm, and the centrifugation time is 5-20 min, preferably 5-15 min.

[0028] The dosage ratio of the seafood condiment to be tested, the solvent, and the alcohol solvent is (0.5-1.5 g):(5-15 mL):(5-15 mL).

[0029] The pH of the sample is 2-10, which can be 2, 4, 6, 8, 10, preferably 6-8.

[0030] The addition amount of NaCl is 0-2.0 wt.%, which can be 0, 0.5, 1.1, 1.5, 2.0 wt.%.

[0031] In one or more embodiments, the volume of the sample is 50-250 mL, which can be 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250 mL, preferably 90-110 mL.

[0032] In one or more embodiments, the flow rate of the sample is 2-6 mL·min -1 , which can be 2 mL·min -1 , 3 mL·min -1 , 4 mL·min -1 , 5 mL·min -1 , 6 mL·min -1 , preferably 3-5 mL·min -1 .

[0033] One or some of the above technical solutions have the following advantages or beneficial effects:

[0034] In this invention, a metal-organic framework material (MIL-101-Cr) was prepared by the hydrothermal synthesis method. It has advantages such as a large specific surface area, excellent stability, and abundant functional groups. As an adsorbent, a solid-phase extraction (SPE) column was fabricated and used for the separation and enrichment of bromophenol flavor substances (BPs). Under the optimized SPE conditions, combined with gas chromatography-mass spectrometry technology, an analytical method for detecting 4 kinds of BPs (4-bromophenol, 2,4-dibromophenol, 2,6-dibromophenol, 2,4,6-tribromophenol) was established. This method has good linearity (R 2 ≥0.996), low detection limits (1.3 - 5.7 ng·L -1 ), and high precision (1.5 - 8.3%, n = 6). Applying this method to the detection of seafood condiments such as oyster sauce and seafood soy sauce, the contents of 4-bromophenol in seafood soy sauce and oyster sauce were measured to be 57 ng·kg -1 and 63 ng·kg -1 respectively. Through low, medium, and high spiked recovery experiments, the recoveries were measured to be between 81.2 - 103.4%, further verifying the accuracy and reliability of this method.

[0035] In addition, compared with commonly used commercial solid-phase extraction columns, the SPE column prepared based on MIL-101-Cr not only has better extraction efficiency but also has a good service life, that is, after 9 adsorption-desorption cycle operations, its adsorption capacity still remains good, and this SPE column has certain commercial application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The specification drawings forming a part of this invention are used to provide a further understanding of this invention. The schematic embodiments of this invention and their descriptions are used to explain this invention and do not constitute an improper limitation to this invention.

[0037] Figure 1 It is the characterization diagram of MIL-101-Cr in Example 1 of this invention, where, (a) SEM image, (b) XRD spectrum, (c) Fourier transform infrared spectrum, (d) N2 adsorption-desorption isotherm and pore size distribution curve, (e) EDS diagram, (f) water contact angle;

[0038] Figure 2 It is the influence of adsorbent dosage on the extraction effect;

[0039] Figure 3 It is the influence of sample pH and salt concentration on the extraction effect, where, (a) the influence of sample pH on the extraction effect, (b) the influence of salt concentration on the extraction effect;

[0040] Figure 4Effects of sample volume and sample flow rate on extraction efficiency, where (a) shows the effect of sample volume on extraction efficiency and (b) shows the effect of sample flow rate on extraction efficiency;

[0041] Figure 5 Effects of desorbent type and desorbent volume on extraction efficiency, where (a) shows the effect of desorbent type on extraction efficiency and (b) shows the effect of desorbent volume on extraction efficiency;

[0042] Figure 6 Chromatograms of four different spiked concentrations of BPs in oil samples, where (a) is 0 ng / L -1 , (b) is 100 ng / L -1 , (c) is 1000 ng / L -1 , (d) is 5000 ng / L -1 ;

[0043] Figure 7 Comparison of the number of times of reuse of MIL-101-Cr column and extraction efficiency with commercial column, where (a) shows the number of times of reuse of MIL-101-Cr column and (b) shows the comparison of extraction efficiency between MIL-101-Cr column and commercial column. Detailed implementation

[0044] Unless otherwise specified, all chemicals are of analytical reagent grade. 4-Bromophenol (4-BP, purity ≥ 98%), 2,4-dibromophenol (2,4-DBP, purity ≥ 98%), 2,6-dibromophenol (2,6-DBP, purity ≥ 98%), 2,4,6-tribromophenol (2,4,6-TBP, purity ≥ 98%) were all purchased from Shanghai Macklin Biochemical Co., Ltd. Ethanol and chromium(III) nitrate nonahydrate (chromatographically pure) were purchased from Sinopharm Chemical Reagent Co., Ltd. N,N-Dimethylformamide, ethyl acetate, dichloromethane were bought from Tianjin Kemiou Chemical Reagent Co., Ltd. Methanol, acetonitrile, and sodium chloride were purchased from Thermo Fisher Scientific Co., Ltd. Terephthalic acid (purity ≥ 96%) was bought from Tianjin Sians Chemical Technology Co., Ltd.

[0045] Weigh 5 mg of four bromophenol (4-BP, 2,4-DBP, 2,6-DBP, 2,4,6-DBP) standards, dissolve them in methanol in a 100 mL volumetric flask to obtain a 50 mg / L standard stock solution of four BPs, and store it in the dark at 4 °C. Gradually dilute the BPs standard stock solution with methanol to obtain BPs standard solutions with different concentrations.

[0046] The morphology of the material was obtained by scanning electron microscopy (SEM) analysis on a SWPRATM 55 instrument (Zeiss, Germany). The spectra in the range of 400 - 4000 cm were collected on a Nicolet 710 spectrometer (Thermo, USA)-1 The infrared spectrum and X-ray diffraction (XRD) analysis data were obtained using a Bruker D8 Advance diffractometer (Bruker, Germany). The N2 adsorption-desorption isotherm results of the material were obtained using an ASAP 2460 analyzer (Micromeritics, USA). The chemical composition of MIL-101-Cr was analyzed using energy-dispersive X-ray spectroscopy (EDS) on a SWPRATM 55 instrument. The contact angle of the material with water was analyzed using an OCA20 instrument (Dataphysics, Germany).

[0047] The instrument used for GC-MS detection was Agilent (7890B-7000D), and the gas chromatography column was HP-5ms (30 m × 0.25 mm × 0.25 μm) for the separation of bromophenols. The temperature gradient program was as follows: the initial temperature was maintained at 60 °C for 2 min, and then heated at a rate of 20 °C·min -1 to 220 °C and maintained for 2 min. The auto-injection mode was used, the injection volume was 1.0 μL, and the injection was carried out in the splitless mode. The collision gas was helium, and the constant flow rate was set at 2.25 mL·min -1 . The ion source was an EI source, and the SIM mode was selected for the detection mode. The specific parameters are shown in Table 1 below.

[0048] Table 1 Retention times and SIM mode parameters of bromophenols

[0049]

[0050]

[0051] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0052] Example 1

[0053] 1. Synthesis of MIL-101-Cr:

[0054] The hydrothermal method was used for synthesis. Cr(NO3)3·9H2O (2 g, 5 mmol) was dissolved in 12 mL of deionized water, and terephthalic acid (0.83 g, 5 mmol) was weighed and mixed with 12 mL of deionized water. Since terephthalic acid has low solubility in water, the mixed solution was ultrasonicated for 20 min, then added to the first solution, and 0.1 mL of hydrofluoric acid was added. The mixture was stirred for 15 min, and the solution was transferred to a polytetrafluoroethylene reaction kettle and stored in an oven at 220 °C for 8 h. After cooling to room temperature, it was washed 3 times with deionized water and DMF respectively, centrifuged, and dried at 80 °C for 12 h to obtain a green solid of MIL-101-Cr.

[0055] 2. Preparation and Application of Solid Phase Extraction Column

[0056] Preparation of MIL-101-Cr solid phase extraction column: Grind the completely dried MIL-101-Cr solid in an agate mortar until it becomes a uniform powder. Place a gasket in an SPE empty column (column height 6 cm, diameter 0.8 cm), weigh 55 mg of MIL-101-Cr powder, add another gasket, and ensure that the material is fully packed in the column to reduce material loss during subsequent operations. Before each extraction, activate the solid phase extraction column with 6 mL of methanol and 6 mL of ultrapure water.

[0057] Fix the MIL-101-Cr solid phase extraction column on the solid phase extraction device, and connect the column to the sample solution with a polytetrafluoroethylene connecting tube. Connect the entire device to a vacuum pump, and adjust the pressure so that the sample flows through the solid phase extraction column at a uniform and appropriate speed. Subsequently, dry the solid phase extraction column under the maximum negative pressure of the vacuum pump for 3 minutes. Use 8 mL of acetonitrile as the eluent to elute the solid phase extraction column. Collect the eluate, dry it under a nitrogen stream at 30 °C, redissolve it with 1 mL of methanol, ultrasonicate for 1 min, then add 0.15 mL of acetic anhydride and 0.05 mL of triethylamine for derivatization. Subsequently, shake the solution at 30 °C for 20 minutes, filter it through a 0.22 μm organic membrane, and then perform instrumental detection.

[0058] 3. Sample Collection and Pretreatment

[0059] In this experiment, 1 kind of soy sauce (Brand 1 soy sauce) and 3 kinds of oyster sauces (Brand 1 oyster sauce, Brand 2 oyster sauce, Brand 3 oyster sauce) were selected as actual samples. The samples were all purchased from local supermarkets.

[0060] Treatment of soy sauce: Weigh 1 g of soy sauce into a 50 mL centrifuge tube, add 10 mL of acetonitrile-water (v / v = 1:1) to reduce the salt concentration and precipitate pigments, vortex and then ultrasonicate for 10 min, centrifuge at 10000 rpm for 10 min, retain the upper supernatant, add 10 mL of methanol to the lower precipitate to extract the possibly remaining bromophenol, ultrasonicate for 5 min and then centrifuge, combine the upper organic solutions, and dry them under a nitrogen stream at 30 °C. Redissolve with 100 mL of ultrapure water with a pH of 6 before SPE.

[0061] Treatment of oyster sauce: Weigh 1 g of oyster sauce into a 50 mL centrifuge tube, add 10 mL of acetonitrile to destroy its protein, vortex and then ultrasonicate for 10 min, centrifuge at 10000 rpm for 5 min, retain the supernatant, add 10 mL of methanol to the lower precipitate to extract the possibly remaining bromophenol, ultrasonicate for 5 min and then centrifuge, combine the upper organic solutions, dry them under a nitrogen stream at 30 °C and then dissolve. Redissolve with 100 mL of ultrapure water with a pH of 6 before SPE.

[0062] Spiked actual sample treatment: After adding the actual sample in the above process, 1 mL (1 μg / L) of the mixed bromophenol standard solution was added, and the remaining treatment steps were the same as above.

[0063] 4. Methodological investigation

[0064] Sample solutions with bromophenol concentrations of 5, 10, 50, 100, 500, 1000, and 5000 ng·L -1 were prepared. After SPE and derivatization, GC-MS analysis was performed to obtain the linear range, limits of detection (LODs), and limits of quantification (LOQs) of the method. The LODs and LOQs were obtained by the baseline noise method at S / N of 3 and 10, respectively. The precision of the method was determined by analyzing the relative standard deviations (RSDs) of day-to-day and within-day. The accuracy of the method was analyzed by calculating the average recovery rate and RSD through three parallel spiking experiments on actual samples at low, medium, and high concentrations. The matrix effect (ME) was measured according to the following formula:

[0065] ME = B / A

[0066] where A is the peak area of the analyte in pure solvent; B is the peak area of the analyte in the blank sample matrix solution.

[0067] The morphology of the MIL-101-Cr material was observed using a scanning electron microscope (SEM). Figure 1 As shown in (a) of Figure 1 , the MIL-101-Cr material is octahedral grains. Figure 1 As shown in (b) of -1 , the X-ray diffraction pattern of the synthesized MIL-101-Cr material basically coincides with the simulated pattern, and strong peaks appear at 2θ = 5.14°, 5.87°, 8.38°, and 9.03°, corresponding to the diffraction peaks of the (511), (531), (822), and (911) planes of MIL-101-Cr, which is consistent with the previously reported literature. Figure 1 As shown in (c) of -1 , the Fourier transform infrared spectrum of the MIL-101-Cr material shows that in the wavenumber range of 400 - 4000 cm -1 , at 1404 cm -1 is the characteristic vibration peak of the COO- group of the carboxyl group in MIL-101-Cr. The absorption peaks at 745 cm -1 and 1180 cm -1 prove the presence of the benzene ring in the material. The peak at 530 cm -1 is related to the Cr-O vibration. Due to the breathing characteristics of the MIL-101-Cr pore channels, there is less water adsorbed on the material surface, resulting in -1The absorption peak at this position is weak. The above results indicate the successful synthesis of MIL-101-Cr. At the same time, after soaking in acidic, alkaline, pure water, and organic solutions for 24 h and then drying, infrared detection was carried out again, and the characteristic peaks of the material were retained, proving that the material has good chemical stability. As Figure 1 (d) in shows the results of the nitrogen adsorption-desorption experiment. The specific surface area of MIL-101-Cr is 562.91 m 2 / g, and the pore size is 3.38 nm. As Figure 1 (e) in shows that the surface energy spectrum results show the presence of C, N, O, and in addition, the presence of Cr, proving the successful synthesis of MIL-101-Cr. Figure 1 (f) in shows that by analyzing the contact angle with water, the contact angles of the material with water are 36.72° and 40.73°, indicating that the material is a hydrophilic material.

[0068] Example 2 Optimization of Solid Phase Extraction Parameters

[0069] The adsorbent dosage, pH, salt ion concentration, sample volume, sample flow rate, eluent type, and volume of SPE were optimized to determine the best extraction conditions to obtain higher extraction recovery rates.

[0070] (1) Adsorbent Dosage

[0071] The core of solid phase extraction is the adsorbent, and the dosage of the adsorbent directly affects the extraction effect. In this experiment, the effects of different adsorbent dosages (45 - 60 mg) on the extraction effect of bromophenol were analyzed. As Figure 2 shown, when the adsorbent increased from 40 mg to 55 mg, the extraction efficiency continuously increased. When the adsorbent was increased again, the extraction efficiency did not increase significantly. Therefore, considering the extraction efficiency and cost savings, 55 mg of adsorbent was selected for the subsequent experiment in this experiment.

[0072] (2) Sample pH and Salt Concentration

[0073] The pH of the solution can affect the existence form of the analyte in the solution, thereby affecting the extraction efficiency. Therefore, choosing the appropriate pH has a great effect on extraction. The effects of solution pH (pH = 2 - 10) on the extraction of bromophenol were studied. As Figure 3As shown in (a) of [reference], the extraction effect is better when the pH is between 6 and 8. The possible reason is that the pKa of the pollutant is 6.34 - 9.37. When the pH value is greater than the pKa, most of the target substances exist in ionic form, BPs ionize in the solution and exist in anionic state. There is an electrostatic interaction between the positively charged surface of MIL-101-Cr material and the anionic BPs. At the same time, it may be that the molecular state of BPs reduces its solubility in water, which is beneficial to the adsorption between the material and the molecules. In addition, the pH value of the samples involved in this experiment is weakly acidic. For the convenience of the experiment, the pH value of the sample solution is selected as 6 for subsequent experiments.

[0074] The ionic strength of the solution was affected by adding different amounts (0 - 2% wt) of NaCl, and the effect on the extraction efficiency of BPs was observed. As Figure 3 shown in (b) of [reference], when no NaCl was added, the extraction efficiency of bromophenol was the best. The increase in salt concentration led to an increase in the viscosity of the solution, which affected the diffusion rate of BPs in the solution. In addition, it was also possible that NaCl occupied the adsorption sites on the surface of MIL-101-Cr material, resulting in a decrease in the extraction effect. Therefore, no NaCl was added in this experiment.

[0075] (3) Sample volume and sample flow rate

[0076] The sample volume is also a factor affecting the extraction effect. It is closely related to the enrichment factor of the analytical method. At the same time, increasing the sample volume can improve the detection sensitivity. In this study, the effect of sample volume (50 - 250 mL) on the extraction effect of BPs was investigated. As Figure 4 shown in (a) of [reference], when the sample volume was higher than 100 mL, the extraction efficiency decreased significantly. To obtain a higher enrichment factor and extraction efficiency, 100 mL was selected as the sample volume for the experiment.

[0077] The sample flow rate will affect the adsorption between the adsorbent and the pollutant. Too fast a flow rate will result in incomplete adsorption of the adsorbent and the pollutant, affecting the extraction effect. Too slow a flow rate will require too long an extraction time, reducing the extraction efficiency. In this experiment, the extraction effect between a sample flow rate of 2 - 6 mL·min -1 was investigated. As Figure 4 shown in (b) of [reference], within a flow rate of 4 mL·min -1 , the sample flow rate had no obvious effect on the recovery rate. When the flow rate was higher than 5 mL·min -1 , the extraction efficiency began to decline and the recovery rate was lower than 80%. To obtain a better extraction effect and higher extraction efficiency, the experimental flow rate was controlled at 4 mL·min -1 .

[0078] (4) Desorbing solution type and volume

[0079] The type of desorbing solution is also one of the factors affecting the extraction efficiency. The desorbing solution determines whether the analytes can be completely desorbed and collected. In this experiment, the effects of organic solvents such as methanol, dichloromethane, ethanol, ethyl acetate, and acetonitrile on the extraction efficiency were investigated. As Figure 5 shown in (a) of

[0080] , acetonitrile had the best elution effect. The reason might be that acetonitrile has a relatively high polarity, and BPs are also a class of compounds with relatively high polarity. According to the "like dissolves like" principle, BPs are more easily eluted by acetonitrile. Figure 5 In this experiment, the volume of the desorbing solution (2 - 10 mL) was explored. As

[0081] shown in (b) of

[0082] , as the volume of the desorbing solution increased, the extraction efficiency of bromophenols gradually increased. When the volume increased to 8 mL, further increasing the volume of the desorbing solution did not significantly improve the extraction efficiency. To ensure the stability and reliability of the results and considering the impact on the environment, 8 mL of the desorbing solution was selected for elution in this experiment. -1 , 4-BP linear range was 10 - 5000 ng·L -1 , with good linear correlation coefficients (R 2 ≥0.996). The LODs and LOQs in oyster sauce samples were 1.5 - 5.7 ng·L -1 and 5.0 - 19 ng·L -1 , respectively. The LODs and LOQs in soy sauce samples were 1.3 - 5.4 ng·L -1 and 4.3 - 18 ng·L -1 , respectively. The intra-day RSDs of this method were 1.5% - 6.8%, and the inter-day RSDs were 3.4% - 8.3%. The above data indicate that the developed method has satisfactory reliability in detecting BPs.

[0083] Table 2 Related data of the established method

[0084]

[0085] Table 3 Matrix effect of BPs

[0086]

[0087] Example 3 Analysis of actual samples

[0088] The method proposed by the present invention examines BPs in actual samples of oil-consuming and soy sauce. As shown in Table 4, among the three actual samples of oil-consuming, the content of 4-BP was found to be 63 ng·kg in Brand 1 oil-consuming -1 , and the content of 4-BP was found to be 57 ng·kg in the actual sample of Brand 1 soy sauce -1 . Three concentrations of low, medium and high (100, 1000, 5000 ng·L -1 ) were selected within the linear range for the standard addition recovery experiment. The standard addition recovery rate of the actual sample was between 81.2 - 103.4%. The experimental results show that the established method has reliability and applicability for the analysis of BPs in complex samples Figure 6 It is the chromatogram of BPs at four standard addition concentrations in the oil-consuming sample

[0089] Table 4 Content and standard addition recovery rate of BPs in actual samples

[0090]

[0091]

[0092] Note: a The unit is ng·kg -1 ; b means not detected

[0093] Compared with the prior art, the amount of adsorbent may be as high as 500 mg, the enrichment factor may be only 10, the extraction time may be as high as 60 min, and the recovery rate may be lower than 70%. The SPE-GC-MS method established by the present invention has a lower detection limit (1.3 ng·L -1 ) when extracting bromophenols, less adsorbent amount (55 mg) and higher enrichment factor (100); it has a shorter extraction time (25 min) and higher recovery rate (81.2%); at a similar detection limit, the method adopted by the present invention can detect samples with more complex matrices (soy sauce, oil-consuming). After comparison, the method developed by the present invention has the advantages of low detection limit, short extraction time, less adsorbent amount and higher enrichment factor, and can meet the detection requirements of trace BPs in food samples

[0094] Example 4 Reusability of MIL-101-Cr and comparison with commercial columns

[0095] The reusability of the MIL-101-Cr extraction column was investigated through multiple adsorption-desorption cycles. As Figure 7 shown in (a) of Figure 7 , the extraction efficiency of a single MIL-101-Cr extraction column did not significantly decrease after being recycled 9 times. The results indicate that the developed solid-phase extraction column has good practicability for the four BPs pollutants. Meanwhile, the extraction performance of this column was compared with that of 4 commonly used commercial columns (Cleanert PEP, Silica, SAX, and C18) for BPs. Under the same conditions, BPs in fuel oil were extracted, and the results are as Figure 7 shown in (b) of Figure 7 . The prepared extraction column has a higher extraction efficiency, and the filling material of the MIL-101-Cr extraction column is 55 mg, while the adsorbent filling amounts of other commercial columns are higher than that of the prepared extraction column. The results show that the developed MIL-101-Cr extraction column has good commercial practicability for the four BPs pollutants.

[0096] In this invention, an MIL series of MOFs materials was synthesized and used as the adsorbent for solid-phase extraction. A method for analyzing 4 BPs in seafood seasonings was established by combining solid-phase extraction with GC-MS technology. This method has advantages such as good linearity (R 2 ≥0.996), low detection limits (1.3 - 5.7 ng·L -1 ), and high precision (RSD≤8.3%, n = 6). This method was applied to the detection of fuel oil and soy sauce, and satisfactory recoveries of 81.2 - 103.4% were obtained in the spiked recovery experiments. When commonly used seafood seasonings on the market were determined by this method, the content of 4-BP in soy sauce was measured to be 57 ng·kg -1 , while the content of 4-BP in fuel oil was 63 ng·kg -1 . At the same time, the prepared extraction column was compared with common commercial columns, and the prepared extraction column has advantages such as higher extraction performance and service life. In summary, this invention successfully established a method for analyzing bromophenol flavor substances in seafood seasonings and successfully realized the detection of seafood seasonings, providing technical support for constructing a scientific product quality management framework and safety verification system.

[0097] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An analytical method for detecting bromophenol flavor substances in seafood seasonings, characterized in that, It includes the following steps: Fill the metal-organic framework material into a solid-phase extraction column to prepare the solid-phase extraction column; Use the pretreated seafood condiment as a sample, and detect the sample by using the solid-phase extraction column and gas chromatography-mass spectrometry; The metal-organic framework material is MIL-101-Cr.

2. The analysis method according to claim 1, wherein The bromophenol flavor substances include one or more of 4-bromophenol, 2,4-dibromophenol, 2,6-dibromophenol, and 2,4,6-tribromophenol.

3. The analysis method according to claim 1, characterized in that, The seafood condiment includes one or more of oyster sauce and seafood soy sauce.

4. The analysis method according to claim 1, characterized in that, The MIL-101-Cr material is prepared by a hydrothermal method; Preferably, the specific surface area of MIL-101-Cr is 400-800 m 2 / g, and the pore size is 1-10 nm.

5. The analysis method according to claim 1, characterized in that Fill MIL-101-Cr into the solid-phase extraction column, and seal both ends with gaskets; Preferably, before each extraction, activate the solid-phase extraction column with methanol and water; Preferably, the filling amount of MIL-101-Cr is 40-60 mg.

6. The analysis method according to claim 1, wherein Fix the solid-phase extraction column on a solid-phase extraction device, connect the solid-phase extraction column to the sample solution with a connecting tube, and connect the solid-phase extraction device to a vacuum pump; Dry the solid-phase extraction column under the maximum negative pressure of the vacuum pump, elute the solid-phase extraction column with a desorbing solution, collect the eluate, dry it under a nitrogen stream, redissolve it with methanol, after ultrasonic treatment, then add acetic anhydride and triethylamine for derivatization, then shake the solution, filter it through an organic membrane and then conduct instrumental detection.

7. The analysis method according to claim 6, characterized in that, The desorbing solution includes one or more of methanol, dichloromethane, ethanol, ethyl acetate, and acetonitrile; Preferably, the volume of the desorbing solution is 2-10 mL.

8. The analysis method according to claim 1, wherein The pretreatment is as follows: Add a solvent to the seafood condiment to be measured, perform ultrasonic treatment and then centrifugation, retain the upper clear liquid, add an alcohol solvent to the lower precipitate, perform ultrasonic treatment and then centrifugation, combine the upper clear liquids, and dry them under a nitrogen stream.

9. The analysis method according to claim 8, wherein The solvent is acetonitrile-water or acetonitrile, wherein the volume ratio of acetonitrile-water is 1:1; Preferably, the alcohol solvent is methanol; Preferably, the dosage ratio of the seafood condiment to be measured, the solvent, and the alcohol solvent is (0.5-1.5 g):(5-15 mL):(5-15 mL); Preferably, the pH of the sample is 2-10; Preferably, the addition amount of NaCl is 0-2.0 wt.%; 10. The analysis method according to claim 1, characterized in that The volume of the sample is 50-250 mL; Preferably, the flow rate of the sample is 2-6 mL·min -1 .

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