A ruthenium-palladium bimetallic loaded mesoporous polystyrene microsphere and a method for preparing the same and detecting freshness of meat

Abstract

The application discloses a kind of loaded ruthenium palladium bimetal mesoporous polystyrene microspheres and its preparation and the method for detecting meat freshness.The material is mesoporous polystyrene microspheres as carrier, surface is evenly distributed with etching hole, by in-situ oxidation-reduction deposition method, ruthenium and palladium two metal active components are loaded on the surface of microsphere, and form ruthenium palladium heterostructure.The application also provides the specific method for using the material as detection substrate, including electrochemical detection and colorimetric detection two modes, and establishes the fitting relationship curve between signal value and myoglobin oxidation time.The whole detection process is mild, simple to operate, and the detection substrate shows good detection effect in meat freshness evaluation.

Description

Technical Field

[0001] This invention relates to the field of functional materials, specifically to a ruthenium-palladium bimetallic mesoporous polystyrene microsphere supported on the same and a method for preparing and detecting the freshness of meat. Background Technology

[0002] Meat products are prone to spoilage during storage and transportation, and the oxidation state of myoglobin is one of the important indicators for assessing meat freshness. In fresh meat, myoglobin mainly exists in a reduced state. With prolonged storage, myoglobin is gradually oxidized to methemoglobin, causing the meat color to change from bright red to brown, and indicating a decline in freshness. Therefore, rapid and sensitive detection of the oxidation state of myoglobin is of great significance for assessing meat freshness.

[0003] Traditional methods for detecting myoglobin freshness include sensory evaluation, microbial culture, and volatile basic nitrogen determination. These methods suffer from drawbacks such as high subjectivity, long processing times, and complex operation. In recent years, nanomaterial-based sensing methods have attracted widespread attention due to their advantages of rapid response, high sensitivity, and ease of operation. However, most existing detection methods employ only a single detection mode, making them susceptible to interference from the sample matrix, and the accuracy and reliability of the results need improvement.

[0004] The dual-mode detection strategy integrates two independent detection modes, enabling mutual verification within the same system and effectively improving the accuracy and anti-interference capability of the detection results. Therefore, developing a dual-mode detection method for meat freshness based on nanomaterials has significant practical application value. Summary of the Invention

[0005] To address the above technical problems, this invention provides ruthenium-palladium bimetallic mesoporous polystyrene microspheres, their preparation, and a method for detecting meat freshness. This invention also provides specific methods for using this material as a detection substrate, including both electrochemical and colorimetric detection modes, and establishes a fitting curve between signal values ​​and myoglobin oxidation time. The entire detection process is mild and simple to operate, and this detection substrate exhibits good detection performance in evaluating meat freshness.

[0006] The first objective of this invention is to provide a ruthenium-palladium bimetallic mesoporous polystyrene microsphere supported on a mesoporous polystyrene microsphere as a carrier, and a ruthenium-palladium heterostructure supported on the surface of the carrier or inside the mesopores.

[0007] In some embodiments of the present invention, the molar ratio of ruthenium to palladium in the ruthenium-palladium heterostructure is (1-4):(1-4).

[0008] A second objective of this invention is to provide a method for preparing ruthenium-palladium bimetallic mesoporous polystyrene microspheres as described in claim 1 or 2, characterized by comprising the following steps: A polystyrene microsphere suspension is provided; An inert porogen is used to penetrate into the interior of polystyrene microspheres and induce polymer chain rearrangement, promoting the formation of mesoporous structures. Mesoporous polystyrene microspheres are obtained by static reaction. Mesoporous polystyrene microspheres were dispersed in a solvent, and ruthenium source solution and palladium source solution were added. The mixture was stirred continuously to allow the metal ions to diffuse and adsorb onto the surface and inside the pores of the mesoporous polystyrene microspheres, thus obtaining a mixed solution. A reducing agent was added to the resulting mixed solution and reacted to obtain the loaded ruthenium-palladium bimetallic mesoporous polystyrene microspheres.

[0009] In some embodiments of the present invention, the ratio of polystyrene microspheres to toluene is 1:20 to 1:23; The concentration of the polystyrene microsphere suspension is 12–30 mg / mL; The solvent for the polystyrene microsphere suspension includes deionized water and ethanol, wherein the volume ratio of deionized water to ethanol is (4-5):(0.8-1.0). The temperature for static reaction is 25~30 ℃, and the static reaction time is 8~12 h. The inert porogen includes one or more of toluene, dibutyl phthalate, toluene, cyclohexane, and n-heptane.

[0010] In some embodiments of the present invention, the mass ratio of mesoporous polystyrene microspheres, ruthenium source, and palladium source is (0.1~0.2):(0.015~0.06):(0.01~0.04). The concentration ratio of the ruthenium source solution to the palladium source solution is (0.25~4):1.

[0011] In some embodiments of the present invention, the ruthenium source is selected from one or more of ruthenium trichloride, ruthenium nitrite, and ruthenium ammonium chloride; The palladium source is selected from one or more of potassium tetrachloropalladium, chloropalladium, and potassium tetranitropalladium.

[0012] In some embodiments of the present invention, the reducing agent is selected from one or more of sodium borohydride, potassium permanganate, and sodium citrate; the concentration of the reducing agent is 10-15 mg / mL; Conditions for redox reactions: time 30-120 min, temperature 30-35 ℃.

[0013] The third objective of this invention is to provide the application of the aforementioned ruthenium-palladium bimetallic mesoporous polystyrene microspheres in detecting meat freshness, by detecting the degree of myoglobin oxidation in the meat to determine meat freshness.

[0014] In some embodiments of the present invention, the detection method is a dual-mode method, which includes an electrochemical detection mode and a colorimetric detection mode; A) Electrochemical detection mode: The ruthenium-palladium bimetallic mesoporous polystyrene microspheres loaded with ruthenium and palladium bimetallic mesoporous polystyrene microspheres are mixed and incubated with the sample to allow myoglobin in the sample to bind with the ruthenium-palladium bimetallic mesoporous polystyrene microspheres. The changes in electrochemical signals before and after binding are detected by differential pulse voltammetry. B) Colorimetric detection mode: The ruthenium-palladium bimetallic mesoporous polystyrene microspheres loaded with the sample to be tested are mixed and incubated. TMB and hydrogen peroxide are added to carry out the catalytic reaction. The maximum absorbance of the reaction solution at 550~750nm is detected by UV-Vis spectrophotometer.

[0015] In some embodiments of the present invention, the detection parameters of the differential pulse voltammetry are: potential range -1.0 V to 0.0 V, pulse amplitude 50~100 mV, pulse width 50~100 ms, and scan rate 10~50 mV / s; The conditions for the catalytic reaction were: pH 4.0~5.0, reaction temperature 37 ℃, and reaction time 10~30 min.

[0016] The beneficial effects of this invention are: The ruthenium-palladium bimetallic mesoporous polystyrene microspheres of this invention possess characteristic electrochemical differential pulse voltammetry signals and peroxidase-like catalytic activity. They can catalyze the reaction of 3,3',5,'-tetramethylbenzidine (TMB) with hydrogen peroxide to generate a blue product (oxTMB), exhibiting a characteristic UV absorption peak at 652 nm. When the ruthenium-palladium bimetallic mesoporous polystyrene microspheres bind to myoglobin at different oxidation levels, both the electrochemical signal and catalytic activity of the microspheres are affected. Specifically, after myoglobin binds to the microspheres, it occupies the active sites on the microsphere surface, leading to a decrease in the electrochemical signal; simultaneously, the catalytic ability of the bound microspheres for TMB decreases, the amount of blue product generated decreases, and the UV absorbance decreases. The degree of change in both signals is positively correlated with the degree of oxidation of myoglobin. By detecting the decrease in electrochemical signal and UV absorbance separately, a dual-mode quantitative detection of meat freshness can be achieved. This detection method features a simple preparation process, with two independent signals—electrochemical and UV colorimetric—that can be cross-calibrated to effectively eliminate interference from meat matrix impurities, avoid false positives, and achieve higher detection accuracy. It also boasts excellent material chemical stability, simple sample pretreatment, and a linear range covering the complete oxidation cycle of meat products in daily life, facilitating standardized batch testing in food quality inspection. Attached Figure Description

[0017] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein... Figure 1 The images show scanning electron microscope (SEM) images of the polystyrene microspheres and ruthenium-palladium bimetallic mesoporous polystyrene microspheres obtained in Example 1 of this invention.

[0018] Figure 2 The image shows the UV-Vis spectrophotometric spectrum obtained by catalyzing TMB with ruthenium-palladium bimetallic mesoporous polystyrene microspheres obtained in Example 1 of this invention.

[0019] Figure 3 The differential pulse voltammetric response curve of the ruthenium-palladium bimetallic mesoporous polystyrene microspheres obtained in Example 1 of this invention is shown.

[0020] Figure 4 The images show the UV-Vis spectra of the ruthenium-palladium bimetallic mesoporous polystyrene microspheres obtained in Example 1 of this invention under different catalytic conditions.

[0021] Figure 5 Electrochemical anti-interference performance test of ruthenium-palladium bimetallic mesoporous polystyrene microspheres obtained in Example 1 after different salt ion interference treatments.

[0022] Figure 6 Differential pulse voltammetric response curves of myoglobin with different oxidation levels and the ruthenium-palladium bimetallic mesoporous polystyrene microspheres obtained in Example 1.

[0023] Figure 7 UV-Vis spectrophotometric spectra of myoglobin with different oxidation levels and the ruthenium-palladium bimetallic mesoporous polystyrene microspheres loaded in Example 1 after catalyzing TMB.

[0024] Figure 8 Standard curve of electrochemical signal decrease versus myoglobin oxidation time.

[0025] Figure 9 Standard curve of UV absorbance decrease versus myoglobin oxidation time. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0027] The detection method of the present invention includes the following specific steps: A) Electrochemical detection mode: The ruthenium-palladium bimetallic mesoporous polystyrene microspheres obtained in Example 1 of this invention are mixed and incubated with the extract of the sample to be tested (e.g., meat sample) to allow myoglobin in the sample to bind to the ruthenium-palladium bimetallic mesoporous polystyrene microspheres. The changes in electrochemical signals before and after binding are detected using differential pulse voltammetry. The preferred detection parameters for differential pulse voltammetry are: potential range -1.0 V to 0.0 V, pulse amplitude 50 mV, pulse width 50 ms, and scan rate 10 mV / s.

[0028] B) Colorimetric detection mode: The ruthenium-palladium bimetallic mesoporous polystyrene microspheres obtained in Example 1 of this invention are mixed and incubated with the extract of the meat sample to be tested. TMB and hydrogen peroxide are added to catalyze the reaction. The maximum absorbance of the reaction solution at 550–750 nm is detected by a UV-Vis spectrophotometer. The preferred conditions for the catalytic reaction are: pH 4.0–5.0, reaction temperature 37 °C, and reaction time 10 min.

[0029] Example 1: This embodiment provides a method for preparing ruthenium-palladium bimetallic mesoporous polystyrene microspheres, as detailed below: 1. Preparation of polystyrene microspheres S11 The initiator azobisisobutyronitrile, the dispersant polyvinylpyrrolidone and styrene monomer are dispersed in a dispersion medium (a mixed solution of ethylene glycol methyl ether and ethanol with a mass ratio of 23.16:28.4) and mixed, wherein the mass ratio of styrene monomer, dispersant, initiator and dispersion medium is 10:2:0.14:51.56.

[0030] S12 Pour the mixed solution into a single-necked flask, stir well, and then introduce nitrogen gas into it for 30 min (connect the nitrogen gas delivery tube to the 1 mL pipette tip, insert it to the bottom of the liquid surface, and the gas flow rate is 50 mL / min). After that, tighten the stopper and seal the flask with plastic film to prevent air from entering.

[0031] S13 was heated to 70 °C, and the stirring speed was maintained at 300 r / min. The reaction was carried out for 24 h to obtain a polystyrene microsphere solution. The solution was washed with ethanol by centrifugation at 3000 r / min for 5 minutes, and finally dried under vacuum at 40 °C to obtain polystyrene microsphere powder.

[0032] 2. Preparation of mesoporous polystyrene microspheres S21: Weigh 0.2 g of polystyrene microsphere powder with a particle size of 1.4 µm and disperse it uniformly in a mixed solvent system consisting of 5.0 mL of deionized water and 8.0 mL of ethanol.

[0033] S22: Slowly add 500 µL of toluene under continuous stirring, and let it stand at 35 °C for 1 h to allow the toluene to penetrate into the interior of the polystyrene microspheres for etching, promoting the formation of mesoporous structures.

[0034] S23: After the reaction is completed, the product is dried isothermally and then separated by centrifugation. The product is then washed repeatedly with alternating ethanol and deionized water to remove residual organic solvents and unreacted substances, thereby obtaining mesoporous polystyrene microspheres with stable structure and clean surface.

[0035] 3. Metal ion adsorption S31: The 0.2 g mesoporous polystyrene microspheres prepared in step 2 were redispersed in 10 mL of deionized water and a uniform and stable suspension was obtained by ultrasonic treatment.

[0036] S32: Add 0.2 mM sodium tetrachloropalladium solution and 0.2 mM ruthenium trichloride solution to the system, controlling the volume ratio of the two to be 1:1. Stir continuously at low speed for 1 h at 35 °C to allow Pd to precipitate. 2+ and Ru 3+ It diffuses and adsorbs fully onto the surface and inside the pores of mesoporous polystyrene microspheres.

[0037] 4. Reduction Deposition S41: After the adsorption of metal ions reaches equilibrium, slowly add 1 mL of 0.2 mM sodium borohydride solution made with fresh ice to the system.

[0038] S42: An isothermal redox reaction was carried out at 35 °C for 1 h to allow ruthenium and palladium components to be synergistically deposited on the surface of mesoporous polystyrene microspheres, gradually forming a stable Pd-Ru composite active layer.

[0039] S43: After the reaction is completed, the product is collected by centrifugation and repeatedly washed with deionized water to remove unbound metal ions and byproducts. After purification, a mesoporous polystyrene microsphere-supported manganese-ruthenium bimetallic heterostructure catalyst is obtained.

[0040] Example 2 This embodiment provides a variety of methods for preparing ruthenium-palladium bimetallic mesoporous polystyrene microspheres, which are the same as the preparation method in Example 1. The difference is that in step 3, S32, which is used for metal ion adsorption, different concentration ratios of sodium tetrachloropalladate solution and ruthenium trichloride solution are provided, specifically 1:4, 1:2, 2:1 and 4:1.

[0041] Example 3 This embodiment provides a variety of methods for preparing ruthenium-palladium bimetallic mesoporous polystyrene microspheres, which are the same as the preparation method in Example 1, except that the reaction temperature in step 4, S42 of redox deposition, is replaced with 25, 45, 55, 65, or 75°C.

[0042] Example 4 This embodiment provides a variety of methods for preparing ruthenium-palladium bimetallic mesoporous polystyrene microspheres, which are the same as the preparation method in Example 1, except that the reaction time in step 4, S42 of redox deposition, is replaced with 0.5, 1.5, 2.0, 2.5, and 3.0 h.

[0043] Example 5 This embodiment provides a variety of methods for preparing ruthenium-palladium bimetallic mesoporous polystyrene microspheres, which are the same as the preparation method in Example 1, except that the amount of sodium borohydride solution added in step 4, S41 of redox deposition, is 10, 20, 30, 40, and 50 μL.

[0044] Comparative Example 1 The preparation method of the supported ruthenium-palladium bimetallic mesoporous polystyrene microsphere catalyst in this comparative example is similar to that in Example 1, except that steps 3 and 4 are omitted, and mesoporous polystyrene microspheres PS MPs are finally obtained.

[0045] Comparative Example 2 The preparation method of the supported ruthenium-palladium bimetallic mesoporous polystyrene microsphere catalyst in this comparative example is similar to that in Example 1, except that ruthenium trichloride solution is not added to S32 during metal ion adsorption in step 3; finally, MesPS@Pd is obtained.

[0046] Comparative Example 3 The preparation method of the supported ruthenium-palladium bimetallic mesoporous polystyrene microsphere catalyst in this comparative example is similar to that in Example 1, except that sodium tetrachloropalladate solution is not added to S32 during metal ion adsorption in step 3; finally, MesPS@Ru is obtained.

[0047] Characterization and performance testing The structure of the ruthenium-palladium bimetallic mesoporous polystyrene microspheres obtained in Example 1 was characterized, and the results are shown in the figure. Figure 1 ,Depend on Figure 1 The SEM images show that the prepared PS MPs and MesPS@Ru-Pt are both spherical and uniform in size, with a large number of interconnected mesopores on the surface, proving that this method can stably synthesize mesoporous polystyrene composite microspheres loaded with Ru-Pt bimetals.

[0048] The ruthenium-palladium bimetallic mesoporous polystyrene microspheres obtained in Example 1 were used to test the catalytic activity of TMB. The procedure was as follows: 1 mL of ruthenium-palladium bimetallic mesoporous polystyrene microspheres (2 mg / mL) were mixed with 1 mL of a commercial myoglobin solution (1 mg / mL) and incubated at 37 °C. Then, TMB and hydrogen peroxide were added to initiate the catalytic reaction. The maximum absorbance of the reaction solution in the range of 550–750 nm was measured using a UV-Vis spectrophotometer. The catalytic reaction conditions were pH 4.0, reaction temperature 37 °C, and reaction time 10 min. The experimental results are shown below. Figure 2 As shown in the figure, there is a significant ultraviolet absorption peak within the set wavelength range, located at 654 nm.

[0049] The ruthenium-palladium bimetallic mesoporous polystyrene microspheres obtained in Example 1 were subjected to differential pulse voltammetry (CPV) response testing. The procedure was as follows: 1 mL of 2 mg / mL ruthenium-palladium bimetallic mesoporous polystyrene microspheres and 1 mL of 1 mg / mL commercial myoglobin solution were mixed and incubated at 37°C for 15 min to allow the myoglobin in the sample to bind to the ruthenium-palladium bimetallic mesoporous polystyrene microspheres. The changes in electrochemical signals before and after binding were detected using differential pulse voltammetry. The preferred detection parameters for differential pulse voltammetry were: potential range -1.0 V to 0.0 V, pulse amplitude 50 mV, pulse width 50 ms, and scan rate 10 mV / s. Experimental results are shown below. Figure 3 As shown in the figure, there is a significant electrochemical oxidation peak within the set potential range, located at -0.5 V, with a peak intensity of 188.2 µA, indicating a clear oxidation signal, which provides a basis for expanding the detection range in the future.

[0050] Application Example 1: Establishment of Standard Curve for Colorimetric Detection Mode Preparation of five myoglobin samples with different oxidation levels: Five samples of 1 mL commercial myoglobin with a concentration of 1 mg / mL were placed in an environment of 37 degrees Celsius and exposed to air for 1, 2, 4, 8 and 16 h respectively.

[0051] The ruthenium-palladium bimetallic mesoporous polystyrene microspheres prepared in Example 1 were diluted to 0.2 mg / mL with acetate buffer (20 mM, pH 4.5). Five centrifuge tubes were used, each containing 200 µL of the microsphere dispersion. Then, 200 µL of five myoglobin samples with different oxidation levels after air treatment for 1, 2, 4, 8, and 16 h were added to each tube. The mixture was incubated at 37 °C for 15 min. 50 µL of TMB solution (10 mM, dissolved in dimethyl sulfoxide), 50 µL of hydrogen peroxide solution (50 mM), and 1.5 mL of deionized water were added to each tube. The mixture was immediately added to a cuvette, and the maximum absorbance in the range of 550–750 nm was measured. Using the microsphere dispersion without myoglobin as a blank control, the absorbance of the blank control was measured to be 3.42. The absorbances of the five samples were measured to be 2.11, 1.86, 1.67, 1.48, and 1.36, respectively. The absorbance decreases were calculated to be 1.31, 1.56, 1.75, 1.94, and 2.06.

[0052] A standard curve was plotted with myoglobin oxidation time on the x-axis and absorbance decrease rate on the y-axis, yielding the linear regression equation: y = 1.46 + 0.23 * ln(x - 0.58), R0 2 = 0.98, linear range 1–16 h, such as Figure 7 and 9 As shown.

[0053] Application Example 2: Establishment of Standard Curve for Electrochemical Detection Mode The prepared ruthenium-palladium bimetallic mesoporous polystyrene microspheres were diluted to 0.5 mg / mL with phosphate buffer (10 mM, pH 7.4). Five centrifuge tubes were used, each containing 200 µL of the microsphere dispersion, followed by 200 µL of each of the five myoglobin samples with different oxidation levels from Application Example 1. The mixtures were then incubated at 37 °C for 15 min.

[0054] Differential pulse voltammetry was performed using an electrochemical workstation with the following parameters: potential range -1.0 V to 0.0 V, pulse amplitude 50 mV, pulse width 50 ms, and scan rate 10 mV / s. The ruthenium-palladium bimetallic mesoporous polystyrene microsphere dispersion prepared in Example 1 without myoglobin was used as a blank control, and the peak current of the blank control was measured to be 189.6 µA. The peak current values ​​measured for the six samples were 149.0 µA, 118.4 µA, 86.3 µA, 69.5 µA, and 38.2 µA, respectively. The peak current decreases were calculated to be 40.6 µA, 71.2 µA, 103.3 µA, 120.1 µA, and 151.4 µA.

[0055] A standard curve was plotted with myoglobin oxidation time on the x-axis and peak current decrease rate on the y-axis, yielding the linear regression equation: y = 57.52 + 32.74 * ln(x - 0.41), R0 2 = 0.98, linear range 1–16 h, such as Figure 6 and 8 As shown.

[0056] Anti-interference performance test One mL of the 2 mg / mL mesoporous polystyrene microsphere-supported ruthenium-palladium bimetallic heterostructure catalyst obtained in Application Example 2 was mixed with 10 μM solutions of various salts (CuSO4, MgSO4, CaCl2, NaCl, KCl) and incubated at room temperature for 30 min. The supernatant was then removed by centrifugation. Differential pulse voltammetry (PPV) was then performed on the PPV of the mesoporous polystyrene microsphere-supported ruthenium-palladium bimetallic heterostructure catalyst treated with the five salt ions. The potential range was -1.0 V to 0.0 V, the pulse amplitude was 50 mV, the pulse width was 50 ms, and the scan rate was 10 mV / s. The peak values ​​were recorded. The experimental results are shown below. Figure 5 As shown in the figure, salt ion treatment has almost no effect on the peak value of the detection signal. The difference between the electrochemical signals of the materials treated with the five salts and the signals without salt ion treatment is maintained at ±20 µA.

[0057] The embodiments described above are merely preferred embodiments for fully illustrating the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A ruthenium-palladium bimetallic mesoporous polystyrene microsphere, characterized in that, Mesoporous polystyrene microspheres are used as a carrier, and ruthenium-palladium heterostructures are loaded on the surface of the carrier or inside the mesopores.

2. The ruthenium-palladium bimetallic mesoporous polystyrene microspheres according to claim 1, characterized in that, The molar ratio of ruthenium to palladium in the ruthenium-palladium heterostructure is (1-4):(1-4).

3. A method for preparing ruthenium-palladium bimetallic mesoporous polystyrene microspheres as described in claim 1 or 2, characterized in that, Includes the following steps: A polystyrene microsphere suspension is provided; An inert porogen is used to penetrate into the interior of polystyrene microspheres and induce polymer chain rearrangement, promoting the formation of mesoporous structures. Mesoporous polystyrene microspheres are obtained by static reaction. Mesoporous polystyrene microspheres were dispersed in a solvent, and ruthenium source solution and palladium source solution were added. The mixture was stirred continuously to allow the metal ions to diffuse and adsorb onto the surface and inside the pores of the mesoporous polystyrene microspheres, thus obtaining a mixed solution. A reducing agent was added to the resulting mixed solution and reacted to obtain the loaded ruthenium-palladium bimetallic mesoporous polystyrene microspheres.

4. The preparation method according to claim 3, characterized in that, The ratio of polystyrene microspheres to toluene is 1:20 to 1:23; The concentration of the polystyrene microsphere suspension is 1.43~1.48 mg / mL; The solvent for the polystyrene microsphere suspension includes deionized water and ethanol, wherein the volume ratio of deionized water to ethanol is (4-5):(0.8-1.0). The temperature for static reaction is 25~30 ℃, and the static reaction time is 8~12 h. The inert porogen includes one or more of toluene, dibutyl phthalate, toluene, cyclohexane, and n-heptane.

5. The preparation method according to claim 3, characterized in that, The mass ratio of mesoporous polystyrene microspheres, ruthenium source, and palladium source was (0.1~0.2):(0.015~0.06):(0.01~0.04). The concentration ratio of the ruthenium source solution to the palladium source solution is (0.25~4):

1.

6. The preparation method according to claim 3, characterized in that, The ruthenium source is selected from one or more of ruthenium trichloride, ruthenium nitrite, and ruthenium ammonium chloride; The palladium source is selected from one or more of potassium tetrachloropalladium, chloropalladium, and potassium tetranitropalladium.

7. The preparation method according to claim 3, characterized in that, The reducing agent is selected from one or more of sodium borohydride, potassium permanganate, and sodium citrate; the concentration of the reducing agent is 10-15 mg / mL; Conditions for redox reactions: time 30~120 min, temperature 30~35 ℃.

8. The application of the ruthenium-palladium bimetallic mesoporous polystyrene microspheres according to claim 1 or 2 in detecting meat freshness, wherein the freshness of meat is determined by detecting the degree of myoglobin oxidation in the meat.

9. The application according to claim 8, characterized in that, The detection method is a dual-mode method, which includes an electrochemical detection mode and a colorimetric detection mode. A) Electrochemical detection mode: The ruthenium-palladium bimetallic mesoporous polystyrene microspheres loaded with ruthenium and palladium bimetallic mesoporous polystyrene microspheres are mixed and incubated with the sample to allow myoglobin in the sample to bind with the ruthenium-palladium bimetallic mesoporous polystyrene microspheres. The changes in electrochemical signals before and after binding are detected by differential pulse voltammetry. B) Colorimetric detection mode: The ruthenium-palladium bimetallic mesoporous polystyrene microspheres loaded with the sample to be tested are mixed and incubated. TMB and hydrogen peroxide are added to carry out the catalytic reaction. The maximum absorbance of the reaction solution at 550~750 nm is detected by UV-Vis spectrophotometer.

10. The application according to claim 9, characterized in that, The detection parameters for differential pulse voltammetry are: potential range -1.0 V to 0.0 V, pulse amplitude 50~100 mV, pulse width 50~100 ms, and scan rate 10~50 mV / s; The conditions for the catalytic reaction were: pH 4.0~5.0, reaction temperature 37 ℃, and reaction time 10~30 min.

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