Preparation method and application of electrode capable of simultaneously detecting three pigments of amaranth, carmine and indigo

Abstract

The invention relates to the field of electrochemical analysis methods, and particularly discloses a preparation method and application of an electrode capable of simultaneously detecting three pigments of amaranth, carmine and indigo. The preparation method of the electrode comprises the following steps: firstly, preparing Fe / Co Prussian blue seed crystal modified carbon fiber paper through a chemical deposition method; the Fe / Co type Prussian blue crystal seed modified carbon fiber paper is subjected to a hydrothermal reaction, and a hollow cubic octahedron Fe / Co type Prussian blue nanometer material modified carbon fiber paper electrode is prepared; and finally, calcining to obtain the hollow cubic octahedron Fe / Co oxide nano material modified carbon fiber paper electrode (CoFe2O4 (at) CFP). The CoFe2O4-coated CFP electrode serves as a working electrode, differential pulse voltammetry is combined with chronoamperometry, and the content of three pigments including amaranth, carmine and indigo in a sample to be detected can be detected at the same time. Compared with other methods, the method has the advantages that the preparation is simple, the detection is rapid, the method can be used for simultaneously determining amaranth, carmine and indigo in actual samples such as candies, tap water and beverages, the detection sensitivity is high, the range is wide, and the method has great practical application potential.

Description

Technical Field

[0001] The present invention relates to an electrochemical sensor and its application, in particular to an electrode preparation method and its application method for simultaneously detecting three pigments, namely, indigo (IC), carmine (Pon) and amaranth (Amar). The electrode can be widely used in the simultaneous quantitative analysis of three pigments, namely, IC, Pon and Amar, in the fields of food, medicine, environment, etc. Technical Background

[0002] Pigments are important additives in many fields such as food, cosmetics, and textiles. In particular, natural or synthetic pigments such as indigo, carmine, and amaranth have been widely used as colorants in food and medicine. However, with the excessive use of these pigments, their potential health hazards have gradually attracted attention. Studies have shown that large intake of food or beverages containing certain artificial pigments (such as indigo, carmine, and amaranth) may lead to abnormal liver function and kidney damage. In addition, the accumulation of these pigments may cause damage to genes and increase the risk of cancer. In particular, certain synthetic pigments may have a negative impact on children's neurobehavior and increase the risk of problems such as attention deficit hyperactivity disorder (ADHD). Therefore, it has become a vital task to conduct efficient, accurate, and selective detection of these pigments to ensure their use within a safe range.

[0003] Traditional pigment detection methods such as spectrophotometry, high performance liquid chromatography-mass spectrometry, fluorescence emission spectroscopy and capillary electrophoresis, although they have high sensitivity and can provide relatively accurate analysis results, these methods usually require complex operating steps, high costs, and long detection times. In addition, traditional methods are usually difficult to achieve simultaneous detection of multiple pigments, especially in complex sample systems, and are easily interfered by other components, thereby affecting the accuracy and efficiency of detection. In order to solve the above problems, electrochemical sensors have gradually become a powerful tool in pigment detection due to their simple operation, low cost, fast response speed and the ability to monitor with portable devices. However, in the prior art, electrochemical sensors face several key problems: (1) Selectivity problem: The electrochemical behaviors of different pigments are similar, and existing sensors often find it difficult to achieve selective detection of specific pigments, especially in complex samples, where this interference problem is particularly prominent. (2) Sensitivity problem: Although existing electrochemical methods can detect pigments, their sensitivity and detection range are usually insufficient, especially in low concentration conditions, making it difficult to accurately detect pigments such as indigo, carmine, and amaranth. (3) Stability issues: Existing electrode materials may face stability issues during long-term use, which in turn affects the repeatability and long-term detection performance of the electrode.

[0004] Therefore, how to improve the selectivity, sensitivity and stability of electrochemical sensors by optimizing electrode materials and improving sensing mechanisms has become a key issue in current technical research. The development of new electrode materials or modification technologies can effectively solve these technical bottlenecks and achieve efficient and selective detection of the three pigments of indigo, carmine and amaranth, which has important application value. Summary of the invention

[0005] The present invention provides a method for preparing an electrode capable of simultaneously detecting three pigments, namely, indigo (IC), carmine (Pon), and amaranth (Amar), and an application method thereof. The electrode adopts an in-situ growth preparation method, has excellent selectivity, sensitivity, and stability, can accurately and rapidly detect the three pigments, namely, indigo, carmine, and amaranth, in complex samples, and can be widely used in pigment detection in the fields of food, medicine, and environment. In order to achieve the above-mentioned purpose, the technical scheme adopted by the present invention is as follows:

[0006] 1. Preparation of an electrode capable of simultaneously detecting three pigments: indigo (IC), carmine (Pon), and amaranth (Amar). The electrode preparation method provided by the present invention comprises the following steps:

[0007] Step (1): After preheating the carbon fiber paper (CFP) in an oven at 200°C for 20 minutes, soak it in a mixed aqueous solution containing cobalt salt and sodium citrate and an aqueous solution of potassium ferrocyanide in turn. Each soaking time is 20 seconds. After taking it out, put the carbon fiber paper into an oven and control the temperature at 200°C for pyrolysis reaction for 5 to 10 minutes. This process is repeated twice to obtain Fe / Co-type Prussian blue seed modified carbon fiber paper.

[0008] Step (2): Add the mixed aqueous solution containing cobalt salt and sodium citrate to the potassium ferricyanide aqueous solution, stir evenly and pour into a polytetrafluoroethylene lined autoclave, put the Fe / Co type Prussian blue seed modified carbon fiber paper obtained in step (1) into the reactor, control the temperature at 50-150°C, and perform a hydrothermal reaction for 2-8 hours. After the reaction is completed, cool to room temperature, take out the carbon fiber paper, rinse with deionized water and dry, and obtain a hollow cubic octahedral Fe / Co type Prussian blue nanomaterial modified carbon fiber paper electrode.

[0009] Step (3): placing the electrode in a tube furnace, calcining it in an air atmosphere at 100-350° C. for 1-3 hours, taking it out and cooling it to room temperature, rinsing it with deionized water and drying it to obtain a hollow cubic octahedral Fe / Co oxide nanomaterial-modified carbon fiber paper (CoFe 2 O 4 @CFP), cut into 1 cm × 2 cm rectangles, and obtain an electrode that can simultaneously detect three pigments: amaranth, carmine, and indigo.

[0010] Furthermore, according to the electrode preparation method of the present invention, the cobalt salt in steps (1) and (2) can be selected from one of cobalt acetate, cobalt chloride and cobalt nitrate.

[0011] Further, the molar concentration of the cobalt salt aqueous solution is 0.01-0.1 mol / L, and the molar ratio of the cobalt salt to the sodium citrate is 1:1.5. Further, the molar concentration of the potassium ferrocyanide aqueous solution is 0.01-0.05 mol / L.

[0012] 2. An application method for simultaneously detecting three pigment electrodes: indigo (IC), carmine (Pon), and amaranth (Amar)

[0013] The present invention provides a CoFe 2 O 4 @CFP electrode is used as working electrode, saturated calomel electrode is used as reference electrode, platinum wire electrode is used as counter electrode, 0.1M phosphate buffer solution (PBS, pH 7.0) is used as electrolyte, and differential pulse voltammetry (DPV) and chronoamperometry (CA) are combined to achieve synchronous detection of target pigments, which specifically includes the following steps:

[0014] Standard solution detection:

[0015] (1) adding a standard solution containing IC, Pon, and Amar to the electrolyte, scanning the test solution using DPV, and recording the current response at different potentials;

[0016] (2) CoFe 2 O 4 @CFP electrode can identify and oxidize three pigments at different potentials, among which indigo is oxidized at lower potential, carmine is oxidized at medium-high potential, and amaranth is oxidized at high potential;

[0017] (3) The chronoamperometric curves of the three pigment standard solutions at the above-mentioned low potential, medium-high potential and high potential are measured respectively to establish a standard curve between pigment concentration and current response.

[0018] Unknown sample detection:

[0019] (1) adding a sample to be tested to the electrolyte, performing current response detection at the lowest potential, and if a response is generated, calculating the concentration of indigo in the solution based on a standard curve between the pigment concentration at the low potential and the current response; if no response is generated, continuing to increase the potential for detection;

[0020] (2) performing current response detection at medium and high potentials. If a response is generated, the concentration of carmine in the solution is calculated based on a standard curve between the pigment concentration at medium and high potentials and the current response, while deducting the effect of the measured concentration of indigo on the current; if no response is generated, continuing to increase the potential for detection;

[0021] (3) Performing current response detection at the highest potential. If a response is generated, the concentration of amaranth in the solution is calculated based on a standard curve between the pigment concentration at high potential and the current response, while deducting the effect of the measured indigo and carmine concentrations on the current. If no response is generated, it is determined that the sample does not contain the target pigment.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] (1) The present invention adopts simple soaking pyrolysis and hydrothermal reaction, calcination and other methods to directly modify Fe-Co-based Prussian blue nano-oxide on carbon fiber paper in situ, thereby preparing a carbon fiber paper electrode without the need to add an additional adhesive, which has good conductivity, structural stability and designability, simplifies the preparation process, and reduces costs.

[0024] (2) The electrode material obtained by the present invention can realize accurate quantitative analysis of indigo, carmine and amaranth at different potentials, and has high detection sensitivity and short response time, and is suitable for real-time monitoring of complex samples. Through standard curve comparison, the three pigments can be effectively detected simultaneously, providing reliable technical support for pigment detection in the fields of food, medicine, environment, etc.

[0025] (3) The electrode prepared by the present invention has good stability, can be used for a long time in practical applications, and can be repeatedly tested many times, showing high practicality and application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Shows CoFe 2 O 4 @CFP Scanning electron microscope (SEM) and transmission electron microscope (TEM) images

[0027] Figure 2 shows that CoFe 2 O 4 @CFP and CoFe 2 O 4 X-ray diffraction (XRD) pattern

[0028] Figure 3 The results show the indigo (IC), carmine (Pon) and amaranth (Amar) standard solutions and their mixed solutions in CoFe 2 O 4@Differential pulse voltammetry (DPV) curve on CFP electrode.

[0029] Figure 4 The linear relationship curves between the pigment concentration and the current response of indigo (IC), carmine (Pon) and amaranth (Amar) standard solutions at low potential, medium potential and high potential are shown. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings:

[0031] Implementation Case 1

[0032] 1. A method for preparing an electrode capable of simultaneously detecting indigo, carmine and amaranth, comprising the following steps: Step (1): preheating carbon fiber paper (CFP) in an oven at 200°C for 20 minutes, and then immersing the CFP in a solution containing 0.03 M Co(NO 3 ) 2 The mixture was immersed in a 0.045M sodium citrate aqueous solution and a 0.02M potassium ferricyanide aqueous solution for 20 seconds each time, and then put into an oven and pyrolyzed at 200°C for 5 minutes. The process was repeated twice to obtain Fe / Co-type Prussian blue seed-modified carbon fiber paper.

[0033] Step (2) contains 0.03M Co(NO 3 ) 2 The mixture is mixed with a mixed aqueous solution of 0.045M sodium citrate and a 0.02M potassium ferrocyanide aqueous solution, and poured into a hydrothermal kettle. The carbon fiber paper modified with the Fe / Co type Prussian blue seed obtained in step (1) is placed in the kettle and hydrothermalized at 100°C for 6 hours. After the reaction is completed, the carbon fiber paper is cooled to room temperature, taken out, rinsed with deionized water, and dried to obtain a hollow cubic octahedral Fe / Co type Prussian blue nanomaterial modified carbon fiber paper electrode.

[0034] Step (3) The electrode is placed in a tube furnace and calcined in an air atmosphere at 250°C for 2 hours. After being taken out, it is cooled to room temperature, rinsed with deionized water, and dried to obtain a hollow cubic octahedral Fe / Co oxide nanomaterial-modified carbon fiber paper electrode, denoted as CoFe 2 O 4 @CFP, cut into 1 cm × 2 cm rectangles, to obtain CoFe that can simultaneously detect three pigments: amaranth, carmine, and indigo. 2 O 4 @CFP electrode.

[0035] The inventors have obtained the CoFe 2 O 4 @CFP electrodes were tested by scanning electron microscopy and transmission electron microscopy, and the results are as follows Figure 1 shown. Figure 1 a depicts CoFe 2 O 4 @CFP morphology, nano hollow CoFe uniformly grown on the carbon fiber surface 2 O 4 Cuboctahedral particles. Magnified by scanning electron microscopy Figure 1 b, c CoFe 2 O 4 The cubic octahedral particle size is about 200nm. CoFe 2 O 4 @CFP’s EDS Figure 2 As shown in the figure, it can be seen that Co, Fe, O and C elements are evenly distributed on the electrode surface. 2 O 4 TEM of nanoparticles Figure 1 As shown in e, CoFe 2 O 4 It is a hollow cubic octahedron, CoFe 2 O 4 The hollow cuboctahedron is composed of a large number of nanoparticles, with a particle size of about 10nm. In the high-resolution TEM image after further magnification ( Figure 1 f), lattice fringes are clearly observed. The spacing of the lattice fringes is 0.295nm and 0.253nm, corresponding to cobalt ferrite (CoFe 2 O 4 ) phase. These lattice spacings are similar to those of CoFe 2 O 4 The characteristic crystal planes of the cubic crystal phase are consistent, confirming the presence of this specific phase in the sample.

[0036] Depend on Figure 2 The XRD pattern of the prepared CoFe 2 O 4 @CFP electrode gives standard CoFe 2 O 4 Characteristic diffraction peaks.

[0037] Implementation Case 2

[0038] The inventor prepared CoFe according to Example 1 2 O 4 @CFP electrode uses differential pulse voltammetry combined with chronopotentiometry to simultaneously detect the contents of indigo (IC), carmine (Pon), and amaranth (Amar) to evaluate the CoFe 2 O 4 Electrochemical response of @CFP electrode: The prepared CoFe 2 O 4@CFP electrode was used as the working electrode, saturated calomel electrode as the reference electrode, and platinum wire electrode as the counter electrode. Standard solutions containing indigo, carmine, and amaranth were added to a pH 7.0 PBS buffer solution to perform differential pulse voltammetry. The results are as follows: In the potential range of 0.1V to 0.9V, CoFe 2 O 4 @CFP electrode recognizes and oxidizes three pigments at different potentials. Indigo is oxidized at a low potential of 0.35V, carmine is oxidized at a medium-high potential of 0.56V, and amaranth is oxidized at a high potential of 0.69V. Figure 3 shown.

[0039] The chronoamperometric curves of the three pigment standard solutions at the three potentials of low (0.35 V), medium-high (0.56 V), and high (0.69 V) were measured respectively, and the standard curves between the corresponding pigment concentration and the current response were established, such as Figure 3 The specific linear equation is shown in the following table.

[0040] Table 1 Linear equations between the concentration and current response of indigo, carmine and amaranth at different potentials.

[0041]

[0042] (C IC is the indigo concentration, I IC is the indigo current response; C Pon is the carmine concentration, I Pon is the carmine current response; C Amar is the concentration of amaranth, I Amar is the current response of amaranth)

[0043] Case 3: Simultaneous determination of amaranth, carmine and indigo in rainbow sugar pigment extract

[0044] Weigh 10 Ludi Rabbit Rainbow Candies (97166301#), add 20mL of ethanol-water (1:1, v / v) mixed solution, stir magnetically for 10min, centrifuge the extract at 10000rpm for 5min to remove insoluble impurities, filter the filtrate with a 0.45μm filter membrane to obtain a clear pigment solution. Take the supernatant and add phosphate buffer solution to dilute to the detection concentration. CoFe was prepared using Example 1 2 O 4 @CFP electrode was used as the working electrode to detect the contents of IC, Pon and Amar in actual rainbow candy samples using the spike recovery method. It was found that the electrode had a good recovery rate of 99.0% to 106.7%.

[0045] Table 1 Simultaneous detection of IC, Pon and Amar contents in rainbow candy samples by sample recovery method

[0046]

[0047]

[0048] a Five parallel measurements were performed

[0049] Implementation Case 4: Simultaneous Determination of Amaranth, Carmine and Indigo in Tap Water

[0050] Take tap water from Haizhou District, Lianyungang City, Jiangsu Province and add phosphate buffer solution to dilute to the detection concentration. 2 O 4 @CFP electrode was used as the working electrode, and the contents of IC, Pon and Amar in the tap water were detected by the spike recovery method. It was found that the electrode had a good recovery rate, which reached 96.7% to 106.0%.

[0051] Table 2 Simultaneous detection of IC, Pon and Amar contents in tap water samples by sample recovery method

[0052]

[0053] a Five parallel measurements were performed

[0054] The present invention is disclosed as above only in terms of preferred embodiments, but it is not intended to limit the present invention in other forms. Any modification, equivalent replacement and modification made to the above embodiments according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention. Therefore, the protection scope of the present invention shall be subject to the definition of the claims.

Claims

1. A method for preparing a pigment electrode capable of simultaneously detecting indigo, carmine and amaranth, characterized in that: The preparation method includes the following steps: Step (1): preheat the carbon fiber paper CFP in an oven at 200° C. for 20 minutes, and then soak it in a mixed aqueous solution containing cobalt salt and sodium citrate and a potassium ferrocyanide aqueous solution in turn, each soaking time is 20 seconds, take it out and put it into an oven, control the temperature at 200° C. for pyrolysis reaction for 5 to 10 minutes; repeat this process twice to obtain Fe / Co type Prussian blue seed modified carbon fiber paper; Step (2): add the mixed aqueous solution containing cobalt salt and sodium citrate to the potassium ferrocyanide aqueous solution, stir evenly and pour it into a polytetrafluoroethylene lined autoclave, put the Fe / Co type Prussian blue seed modified carbon fiber paper obtained in step (1) into the autoclave, control the temperature at 50 to 150° C., and carry out hydrothermal reaction for 2 to 8 hours; after the reaction is completed, cool it to room temperature, take out the carbon fiber paper, rinse it with deionized water, and dry it to obtain a hollow cubic octahedral Fe / Co type Prussian blue nanomaterial modified carbon fiber paper electrode; Step (3): The electrode is placed in a tube furnace and calcined in an air atmosphere at 100 to 350° C. for 1 to 3 hours. After being taken out, it is cooled to room temperature, rinsed with deionized water, and dried to obtain a hollow cubic octahedral Fe / Co oxide nanomaterial-modified carbon fiber paper electrode, denoted as CoFe2O4@CFP, which is cut into a 1 cm × 2 cm rectangle to obtain an electrode that can simultaneously detect three pigments: amaranth, carmine, and indigo.

2. The method for preparing an electrode according to claim 1, characterized in that: The cobalt salt in steps (1) and (2) is one of cobalt acetate, cobalt chloride and cobalt nitrate.

3. The method for preparing an electrode according to claim 1, characterized in that: The molar concentration of the cobalt salt aqueous solution in steps (1) and (2) is 0.01-0.1 mol / L, and the molar ratio of the cobalt salt to sodium citrate is 1:1.

5.

4. The method for preparing an electrode according to claim 1, characterized in that: The molar concentration of the potassium ferrocyanide aqueous solution in step (1) is 0.01 to 0.05 mol / L.

5. An application of an electrode capable of simultaneously detecting three pigments, indigo, carmine and amaranth, characterized in that: The CoFe2O4@CFP described in claims 1-4 is used as a working electrode, a saturated calomel electrode is used as a reference electrode, a platinum wire electrode is used as a counter electrode, and a phosphate buffer solution PBS, pH 7.0 is used as an electrolyte. The contents of amaranth, carmine and indigo in the sample are simultaneously detected by combining differential pulse voltammetry DPV with chronoamperometry CA, specifically comprising the following steps: (1) adding a standard solution containing amaranth, carmine and indigo to the electrolyte, scanning the test solution by DPV, and recording the current response at different potentials; the CoFe2O4@CFP electrode recognizes and oxidizes the three pigments at different potentials, wherein indigo is oxidized at a low potential, carmine is oxidized at a medium-high potential, and amaranth is oxidized at a high potential; (2) respectively measuring the chronoamperometric curves of the three pigment standard solutions at the three potentials of low, medium-high and high, and establishing a standard curve between the corresponding pigment concentration and the current response.

6. The use according to claim 5, characterized in that: The identification and quantitative analysis of the three pigments were achieved by CA step potential scanning, which specifically included the following steps: (1) adding a sample to be tested to the electrolyte, performing current response detection at the lowest potential, and if a current response is detected, calculating the concentration of indigo in the solution based on a standard curve between the pigment concentration and the current response at the low potential; if no response is detected, continuing to increase the detection potential; (2) performing current response detection at medium and high potentials. If a current response is detected, the concentration of carmine in the solution is calculated based on a standard curve between the pigment concentration and the current response at the medium and high potentials, and the effect of the measured indigo concentration on the current signal is deducted; if no response is detected, the detection potential is further increased; (3) performing current response detection at the highest potential. If a current response is detected, the concentration of amaranth in the solution is calculated based on a standard curve between the pigment concentration and the current response at the above high potential, and the influence of the measured indigo and carmine concentrations on the current signal is deducted; if no response is detected, it is determined that the sample does not contain the target pigment.

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