An electrochemically modified electrode for detecting bisphenol A in food, and its preparation method and application

Abstract

The present invention discloses a method for preparing an electrochemically modified electrode for detecting bisphenol A in food. The method comprises forming silica nanochannels modified with cetyltrimethylammonium bromide micelles on the surface of an indium tin oxide conductive substrate using a solution growth method to produce a silica / indium tin oxide composite material; and depositing a polydimethylsiloxane layer on the surface of the silica / indium tin oxide composite material to produce a uPS@SNCM / ITO electrochemically modified electrode. This method enables relatively stable, highly sensitive, and selective monitoring of bisphenol A in ethanol with good interference resistance. The present invention also discloses the electrochemically modified electrode prepared using this method and its applications.

Description

Technical Field

[0001] The present invention belongs to the field of compound detection, and in particular relates to an electrochemically modified electrode for detecting bisphenol A in food, and a preparation method and application thereof. Background Art

[0002] In recent years, with the global popularity of alcoholic beverages, people have become increasingly concerned about the safety issues associated with alcoholic beverages. During the fermentation and storage process of alcoholic beverages, a series of potential hydrophobic organic contaminants such as mycotoxins, pesticides, and plasticizers are often introduced or formed. Among them, the hydrophobic organic compound bisphenol A (BPA) is widely used in the synthesis of plastic products such as polycarbonate and epoxy resin, which are used for food storage and packaging. However, due to its high solubility, BPA easily leach out of the polymer matrix and migrate into food and beverages, especially in alcoholic beverages.

[0003] Bisphenol A (BPA) is an estrogen-like substance with endocrine-disrupting properties. It can diffuse rapidly and completely into cell membranes. Toxicology experiments have shown that BPA affects normal cellular function in the human body by mimicking the effects of estrogen agonists and androgen antagonists, altering hormone levels and affecting metabolism. This can lead to endocrine system disorders and induce pathological changes in the reproductive system, embryonic development, and the central nervous system. BPA accumulates, and sensitive detection of trace levels of BPA can, to a certain extent, mitigate the environmental and human hazards caused by its long-term accumulation.

[0004] The conventional methods for detecting bisphenol A mainly include liquid chromatography, liquid chromatography-mass spectrometry, gas chromatography-mass spectrometry, enzyme-linked immunosorbent assay, capillary electrophoresis, solid phase extraction, chemiluminescence immunoassay, molecular imprinting polymer technology, etc. Most of these methods require complex pretreatment processes and have the disadvantages of being time-consuming, expensive, and consuming too many organic reagents.

[0005] In comparison, electrochemical methods offer advantages such as rapid detection and simplicity. However, existing electrochemical sensors for detecting bisphenol A still have drawbacks, including limited selectivity and stability, and low sensitivity. Furthermore, unlike electrochemical detection in aqueous solutions, non-aqueous ethanol media significantly affect redox kinetics and electron transfer rates, suppressing the electrochemical signal to a certain extent. Therefore, developing a method for direct detection of trace bisphenol A in complex alcohol groups with strong stability, high sensitivity, and strong selectivity in ethanol-containing media is of great significance to both human health and ecosystems.

[0006] At the same time, the direct detection of hydrophobic harmful substances in complex alcohol groups without sample pretreatment remains a challenge. Substances such as phenol, sugar, sulfite and ascorbic acid often contained in complex ethanol matrices have high background redox currents, which interfere with the detection and analysis of the substances to be tested. So far, the analysis of alcohol samples reported so far still relies on dilution with aqueous solution or additional pretreatment steps before electrochemical analysis. Therefore, further research on electrodes with high selectivity, high sensitivity and strong anti-interference properties for detecting hydrophobic compounds is necessary and of great significance. Summary of the Invention

[0007] The present invention provides a method for preparing an electrochemically modified electrode for detecting bisphenol A in food. The method can monitor bisphenol A in ethanol with relatively high stability, high sensitivity, good selectivity and anti-interference performance.

[0008] A method for preparing an electrochemically modified electrode for detecting bisphenol A in food, comprising:

[0009] (1) Pass A solution growth method was used to form silica nanochannels modified with cetyltrimethylammonium bromide micelles on the surface of an indium tin oxide conductive substrate to prepare a cetyltrimethylammonium bromide micelle-modified silica / indium tin oxide composite material (SNCM / ITO).

[0010] (2) A polydimethylsiloxane layer was deposited on the surface of the silica / indium tin oxide composite material to prepare an ultrathin polydimethylsiloxane layer@silica / indium tin oxide composite material modified with hexadecyltrimethylammonium bromide micelles (uPS@SNCM / ITO) electrochemically modified electrode.

[0011] The present invention prevents the dissolution of cetyltrimethylammonium bromide micelles by an ethanol solution by depositing a polydimethylsiloxane layer, thereby ensuring the stable detection of a hydrophobic target, namely, bisphenol A, in the ethanol solution. Furthermore, the combined action of the cetyltrimethylammonium bromide micelles and the polydimethylsiloxane layer enables relatively sensitive detection of bisphenol A in the ethanol solution.

[0012] The thickness of the ultra-thin polydimethylsiloxane layer is 4-6 nm. On the one hand, this thickness avoids the problem of target detection molecules being unable to reach the electrode surface due to being too thick. On the other hand, it effectively prevents the dissolution of hydrophobic micelles CTAB in ethanol-containing solutions, thereby synergistically enhancing the performance of detecting bisphenol A in ethanol-containing solutions with CTAB.

[0013] described The solution is prepared by dissolving hexadecyltrimethylammonium bromide in a mixed solution of water and ethanol, and adding ammonia solution and tetraethyl orthosilicate.

[0014] The mass ratio of the hexadecyltrimethylammonium bromide, the mixed solution of water and ethanol, the ammonia solution and tetraethyl orthosilicate is 16-24:0.91-1.12:7.44.

[0015] Said through Before the solution growth method, the indium tin oxide conductive substrate is ultrasonically cleaned in sequence with sodium hydroxide ethanol solution, acetone, ethanol and deionized water.

[0016] described Solution growth methods, including:

[0017] Adding indium tin oxide conductive base The solution is heated to a temperature of 50-70° C. and kept warm for 12-48 hours. The indium tin oxide conductive substrate is then taken out, dried, and aged to obtain a silicon dioxide / indium tin oxide composite material.

[0018] In step (2), the deposition method is the contact transfer method.

[0019] The contact transfer method comprises:

[0020] A polydimethylsiloxane block is coated on a silica / indium tin oxide composite and incubated at room temperature or elevated temperature for 0.5-4 hours. The block is then peeled off, depositing a layer of polydimethylsiloxane on the surface of the silica / indium tin oxide composite. Compared to the heated deposition method at a distance, the contact method can form a thin polydimethylsiloxane layer in a shorter time, resulting in higher efficiency and a denser deposition.

[0021] The present invention also provides an electrochemically modified electrode prepared by utilizing the preparation method of the electrochemically modified electrode for detecting bisphenol A in an ethanol-containing medium.

[0022] The present invention also provides an application of the electrochemically modified electrode prepared by the preparation method of the electrochemically modified electrode for detecting bisphenol A in an ethanol-containing medium in detecting bisphenol A in an ethanol-containing medium, comprising:

[0023] The electrochemically modified electrode is used to monitor bisphenol A in an alcohol solution through cyclic voltammetry or differential pulse stripping voltammetry.

[0024] The cyclic voltammetry and differential pulse voltammetry both adopt a three-electrode system, wherein uPS@SNCM / ITO is used as the working electrode, a saturated calomel electrode (SCE) is used as the reference electrode, and a platinum wire (Pt) is used as the counter electrode.

[0025] The electrolyte solution used in the differential pulse voltammetry is a phosphate buffered saline solution (PBS solution), and the pH of the electrolyte solution is adjusted to 7-9.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention provides a uPS@SNCM / ITO electrode. Hexadecyltrimethylammonium bromide is unstable in ethanol. In an ethanol-containing medium, a certain amount of hexadecyltrimethylammonium bromide will dissolve from the pores of the SNCM, causing the electrode to lose its ability to detect hydrophobic targets. By depositing an ultrathin PDMS film on the surface of the SNCM / ITO electrode via thermal deposition, the problem of CTAB dissolution from the SNCM / ITO electrode is effectively avoided, while maintaining the CTAB extraction effect on hydrophobic targets in ethanol solutions, effectively improving the sensitivity and selectivity of bisphenol A detection. In actual liquor beverages, the linear detection range of bisphenol A is 1.0-100.0 μmol / L.

[0028] (2) The prepared electrode can be used to determine bisphenol A in complex real alcohol solutions, and has outstanding advantages such as high stability, high selectivity and sensitivity, strong anti-interference and anti-pollution properties, and short detection time. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 These are scanning electron microscope photos of ITO, SNCM / ITO, and uPS@SNCM / ITO prepared in Example 1, where: Figure 1 (a) is a scanning electron microscope photo of ITO. Figure 1 (b) is a scanning electron microscope image of SNCM / ITO. Figure 1 (c) Scanning electron microscope image of uPS@SNCM / ITO.

[0030] Figure 2 X-ray photoelectron spectra of the silica nanochannels prepared in Example 1 and the silica nanochannels deposited with polydimethylsiloxane;

[0031] Figure 3 are the cyclic voltammetry curves of each electrode under different immersion conditions, where: Figure 3 (a) is the concentration of 200 μmol / LRu(NH3)6 3+ Cyclic voltammetry curves of different soaking times in 0.5 mol / L KCl solution containing 50% ethanol, Figure 3 (b) Cyclic voltammetry curves of the electrochemical signal in milk wine containing 0.5 mol / L KCl after immersion in 1.0 mol / L HCl ethanol solution;

[0032] Figure 4 Cyclic voltammetry curves of ITO, SNCM / ITO and uPS@SNCM / ITO in four real sample alcohol solutions, where: Figure 4(a) is the cyclic voltammetry curves of ITO, SNCM / ITO and uPS@SNCM / ITO in white wine solution. Figure 4 (b) Cyclic voltammetry curves of ITO, SNCM / ITO and uPS@SNCM / ITO in milk wine solution. Figure 4 (c) Cyclic voltammetry curves of ITO, SNCM / ITO and uPS@SNCM / ITO in beer solution. Figure 4 (d) Cyclic voltammetry curves of ITO, SNCM / ITO, and uPS@SNCM / ITO in cocktail solution;

[0033] Figure 5 The differential pulse stripping voltammetry curve of bisphenol A concentration changes (1.0-100.0 μmol / L) recorded on the uPS@SNCM / ITO electrode prepared in Example 1 in real sample liquor;

[0034] Figure 6 The calibration graph of the peak current of bisphenol A concentration recorded on the uPS@SNCM / ITO electrode prepared in Example 1 in a real sample of white wine;

[0035] Figure 7 The uPS@SNCM / ITO electrode and the SNCM / ITO electrode prepared in Example 2 were mixed in a solution containing 200 μmol / LRu(NH3)6 3+ Cyclic voltammetry curves of the sample immersed in 0.5 mol / L KCl solution containing 50% ethanol for a certain period of time;

[0036] Figure 8 The electrode prepared in Comparative Example 1 was prepared in a solution containing 200 μmol / L Ru(NH3)6 3+ Cyclic voltammetry curves in 0.5 mol / L KCl solution with 50% ethanol;

[0037] Figure 9 The electrode prepared in Comparative Example 2 was prepared in a solution containing 200 μmol / L Ru(NH3)6 3+ Cyclic voltammetry curves in 0.5 mol / L KCl solution containing 50% ethanol. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to specific embodiments.

[0039] Example 1

[0040] (1) Cleaning the electrode: First, immerse the electrode in an ethanol solution containing 1 mol / L sodium hydroxide and ultrasonically treat it for 1 hour. Then, immerse the electrode in acetone and ethanol in sequence, ultrasonically treat them for 15 minutes each, and then rinse the electrode with deionized water for 15 minutes. Repeat this process twice. Finally, blow dry the electrode with nitrogen gas and set aside for use.

[0041] (2) Deposition of silicon dioxide nanochannels on the surface of the indium tin oxide electrode:

[0042] 1. Configuration Solution: Dissolve 0.16 g of hexadecyltrimethylammonium bromide in 100 mL of a water / ethanol mixture (70 mL / 30 mL). After the hexadecyltrimethylammonium bromide is completely dissolved, slowly add ammonia solution (10 μL) and tetraethyl orthosilicate (80 μL) to the hexadecyltrimethylammonium bromide solution while stirring.

[0043] 2. Place indium tin oxide electrodes, such as Figure 1 As shown in (a), soak in the above The solution was heated in a 60°C water bath, and vibration was avoided as much as possible during the whole process. After 24 hours, the electrode was taken out and rinsed with a large amount of deionized water and blown dry with nitrogen. Subsequently, the electrode was placed in a dry box and placed at a temperature of 100°C for 12 hours for aging. At this time, the nanopores of the obtained electrode were filled with the surfactant hexadecyltrimethylammonium bromide, and an SNCM / ITO composite material with a silicon dioxide nanochannel array with pores perpendicular to the substrate deposited on the surface of the indium tin oxide conductive substrate was obtained. The thickness of the deposited layer was about 110nm, and its scanning electron microscope image was as follows Figure 1 (b)

[0044] (3) Contact transfer method: The prepared polydimethylsiloxane block is gently adsorbed on the SNCM / ITO surface without generating bubbles, and then heated at 100℃ for 1h. Finally, the block polymer is peeled off, leaving an ultra-thin polydimethylsiloxane layer on the SNCM / ITO surface. The scanning electron microscope image is shown as follows: Figure 1 As shown in (c), after the deposition of polydimethylsiloxane, the thickness of SNCM slightly increased from 110nm to 115nm, indicating the presence of an ultrathin polydimethylsiloxane coating. The morphology of ITO particles disappeared after modification. The X-ray photoelectron spectrum of the uPS@SNCM / ITO electrode was obtained by Figure 2 As shown, it is further confirmed that polydimethylsiloxane is deposited on the silica nanochannel;

[0045] (4) Drawing of working curve: 1.0-100 μmol / L bisphenol A was added to 0.1 mol / L PBS (pH 8.0) solution. Under optimized conditions, a positive potential scan of 0.6-1.5 V was applied to the polydimethylsiloxane@cetyltrimethylammonium bromide modified silica nanochannel / indium tin oxide electrode. After standing for 10 s, the differential pulse stripping voltammetry curve of the solution was recorded. The peak current signal was linearly fitted with the bisphenol A concentration data, and the standard curve was drawn as shown below. Figure 6 As shown in Figure 2, 1.0-20.0μmol / L and 20.0-100.0μmol / L showed a good linear relationship, and their linear correlation coefficients were R 2 = 0.99997 and 0.99369. Based on the response current of the uPS@SNCM / ITO electrode to bisphenol A in real alcoholic beverages and the linear relationship curve between current and concentration, the concentration of bisphenol A in the test solution was calculated, thereby achieving the determination of the concentration of bisphenol A in the test solution;

[0046] The performance of traditional electrodes in high concentration ethanol matrix decreases to a certain extent. In order to test the stability of the electrode modified with polydimethylsiloxane in ethanol solution, Figure 3 As shown in (a), after being immersed in a certain concentration of ethanol solution for 5.0 min, SNCM / ITO showed obvious electrochemical signals. The hydrophilic Ru(NH3)6 3+ The presence of the probe redox signal means that the hydrophobic layer is destroyed, indicating that the hydrophobic hexadecyltrimethylammonium bromide micelles are dissolved in the ethanol medium and dissolved from the silica nanochannels, resulting in the destruction of the hydrophobic properties of the electrode. However, uPS@SNCM / ITO does not show obvious redox properties. In actual sample alcoholic beverages, the stability of uPS@SNCM / ITO in alcoholic solutions eliminates the interference of hydrophilic molecules that are often contained. Figure 3 As shown in (b), in the presence of a real-world sample of milk wine containing 0.5 mol / L KCl, SNCM / ITO detected a high background current peak at 1.0 V, while no significant analytical response was observed using uPS@SNCM / ITO. This result confirms that the ultrathin polydimethylsiloxane layer can effectively enhance the target signal and strengthen its anti-interference ability in complex alcohol groups. These results confirm that uPS@SNCM / ITO has excellent stability, target signal enhancement, and excellent anti-interference performance in alcohol solutions and extreme environments.

[0047] In real alcoholic beverage samples, uPS@SNCM / ITO is directly inserted into the actual alcohol sample for analysis without additional pretreatment. Figure 4 (a)- Figure 4(d) The results show that under all conditions, the peak difference (DE) between the oxidation and reduction potentials of this electrode is minimal, indicating the most favorable electron transfer process. Furthermore, in most real-world beverages, the signal on this electrode is significantly higher than that of other electrodes, indicating that the ultrathin polydimethylsiloxane coating on the SNCM / ITO electrode acts as a protective and extraction layer, improving the electrode's performance in real-world alcoholic beverages. The electrode also exhibits excellent anti-interference and anti-fouling properties, demonstrating its ability to detect common hydrophobic substances in complex real-world alcoholic beverages.

[0048] In order to more accurately quantitatively detect bisphenol A in actual alcoholic beverages, differential pulse stripping voltammetry was used, such as Figure 5 After optimizing the accumulation time, uPS@SNCM / ITO recorded the electrochemical behavior of bisphenol A in actual alcohol samples with concentrations ranging from 1.0 to 100 μmol / L. The peak current density was linearly correlated with the increase in bisphenol A concentration. The linear calibration diagram of bisphenol A (1.0-100.0 μmol / L) on this electrode probe is shown in Figure 2. Figure 6 As shown, the regression equations for 1.0-20.0 and 20.0-100.0 μmol / L are: Ip(μA)=0.06719C(μmol / L)+0.06196(R 2 =0.99997) and Ip(μA)=0.02872C(μmol / L)+0.82281(R 2 =0.99369). The detection limit for BPA in the actual alcohol sample was calculated using the formula 3σ / S (σ is the standard deviation of 10 replicate blank signals) to be 0.23 μmol / L (S / N = 3). This sensitivity is significantly lower than the GB 9685-2008 requirement for unbound bisphenol A to be less than 0.6 mg kg. -1 Furthermore, the developed method showed high recovery in authentic liquor samples, as shown in Table 1, demonstrating the feasibility of the developed uPS@SNCM / ITO electrode for electrochemical analysis in complex alcohol matrices.

[0049] Table 1 Detection results and statistical analysis of bisphenol A in liquor samples

[0050]

[0051] Example 2

[0052] (1)-(2): Same as (1)-(2) in Example 1;

[0053] (3) Contact transfer method: The prepared polydimethylsiloxane block was gently adsorbed on the SNCM / ITO surface without generating bubbles, and then heated at 100 °C for 40 min. Finally, the block polymer was peeled off, leaving an ultrathin polydimethylsiloxane layer on the SNCM / ITO surface;

[0054] (4) Figure 7 As shown in the figure, SNCM / ITO immersed in 50% ethanol solution for 0s showed obvious electrochemical signals, and the hydrophilic Ru(NH3)6 3+ The presence of the probe redox signal indicates that the hydrophobic cetyltrimethylammonium bromide micelles dissolved in the ethanol medium and eluted from the silica nanochannels, resulting in the destruction of the electrode's hydrophobic properties. However, uPS@SNCM / ITO immersed in 50% ethanol for 40 minutes showed no significant redox characteristics, further confirming the excellent stability of uPS@SNCM / ITO in ethanolic solutions.

[0055] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principles of the technical solution of the present invention should be equivalent replacement methods. As long as they meet the purpose of the invention, they belong to the scope of protection of the present invention.

[0056] Comparative Example 1

[0057] Compared with Example 1, a thicker polydimethylsiloxane layer is left on the SNCM / ITO surface. The thickness of the polydimethylsiloxane deposition layer is about 3 mm. Figure 8 It shows that the electrode has almost no redox signal, which indicates that an overly thick polydimethylsiloxane layer will hinder the target detection molecules from reaching the electrode surface, thereby affecting the detection performance of the electrode.

[0058] Comparative Example 2

[0059] Compared with Example 1, a layer of polydimethylsiloxane is left on the surface of SNCM / ITO. After the deposition of polydimethylsiloxane, the thickness of SNCM increases slightly from 110 nm to 111 nm. Figure 9 The electrode showed obvious electrochemical signals, and the hydrophilic Ru(NH3)6 3+ The presence of the probe redox signal means that the hydrophobic layer is destroyed, indicating that the polydimethylsiloxane layer with too low thickness cannot avoid the dissolution of hydrophobic hexadecyltrimethylammonium bromide micelles in the ethanol medium, resulting in the destruction of the hydrophobic properties of the electrode.

Claims

1. A method for preparing an electrochemically modified electrode for detecting bisphenol A in food, characterized in that: include: (1) Pass A solution growth method is used to form silica nanochannels modified with hydrophobic hexadecyltrimethylammonium bromide micelles on the surface of an indium tin oxide conductive substrate to prepare a silica / indium tin oxide composite material modified with hexadecyltrimethylammonium bromide micelles; (2) Depositing an ultrathin polydimethylsiloxane layer on the surface of the silica / indium tin oxide composite material by the contact transfer method to prepare an ultrathin polydimethylsiloxane layer@silica / indium tin oxide electrochemically modified electrode modified with hexadecyltrimethylammonium bromide micelles; In step (2), the deposition method is a contact transfer method; The contact transfer method comprises: The polydimethylsiloxane block is attached to the silicon dioxide / indium tin oxide composite electrode material, incubated at room temperature or high temperature for 0.5-4 hours, and then the polydimethylsiloxane block is peeled off so that an ultra-thin polydimethylsiloxane film remains on the surface of the silicon dioxide / indium tin oxide composite material; described The solution is prepared by dissolving hexadecyltrimethylammonium bromide in a mixed solution of water and ethanol, and adding ammonia solution and tetraethyl orthosilicate; The mass ratio of the hexadecyltrimethylammonium bromide, the mixed solution of water and ethanol, the ammonia solution and tetraethyl orthosilicate is 16-24:0.91-1.12:7.

44.

2. The method for preparing an electrochemically modified electrode for detecting bisphenol A in food according to claim 1, wherein: Said through Before the solution growth method, the indium tin oxide conductive substrate is ultrasonically cleaned in sequence with sodium hydroxide ethanol solution, acetone, ethanol and deionized water.

3. The method for preparing an electrochemically modified electrode for detecting bisphenol A in food according to claim 1, wherein: described Solution growth methods, including: Adding indium tin oxide conductive base The solution is heated to a temperature of 50-70° C. and kept warm for 12-48 hours. The indium tin oxide conductive substrate is then taken out, dried, and aged to obtain a silicon dioxide / indium tin oxide composite material.

4. An electrochemically modified electrode prepared according to the method for preparing an electrochemically modified electrode for detecting bisphenol A in food according to any one of claims 1 to 3.

5. An application of the electrochemically modified electrode prepared by the method for preparing an electrochemically modified electrode for detecting bisphenol A in food according to claim 4 in detecting bisphenol A in ethanol-containing food, characterized in that: include: The electrochemically modified electrode can be directly inserted into the original complex alcoholic food to monitor the bisphenol A content therein by cyclic voltammetry or differential pulse stripping voltammetry without any sample pretreatment. The cyclic voltammetry and differential pulse stripping voltammetry both adopt a three-electrode system, wherein a polydimethylsiloxane layer@silica / indium tin oxide composite material electrochemically modified electrode modified with hexadecyltrimethylammonium bromide micelles is the working electrode, a saturated calomel electrode is the reference electrode, and a platinum wire is the counter electrode.

6. Application of the electrochemically modified electrode prepared by the preparation method of the electrochemically modified electrode for detecting bisphenol A in food according to claim 5 in detecting bisphenol A in ethanol-containing food, characterized in that: The electrolyte solution used in the differential pulse stripping voltammetry is a phosphate buffered saline solution, and the pH of the electrolyte solution is adjusted to 7-9.

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