A fluorescent probe for detecting aluminum ions in tap water and food containing aluminum additives and a detection method thereof

Abstract

The application discloses a fluorescent probe for detecting aluminum ions in tap water and aluminum additive food and a detection method thereof. The fluorescent probe is natural polyphenol, i.e., flavoxanthin. The tap water sample with a standard sample and the aluminum additive food sample without a standard sample are dropped into a flavoxanthin solution, and the fluorescence intensity is measured by using a fluorescence spectrometer to realize quantitative detection of aluminum ions in the tap water and the aluminum additive food. The fluorescent probe provided by the application has low toxicity, is friendly to human bodies and the environment, and has simple and convenient detection methods and is green and environment-friendly. The detection limit of the fluorescent probe for aluminum ions is 0.52 muM, and the fluorescent probe has high sensitivity and rapid response. In the detection of the tap water and the aluminum additive food samples, the aluminum ion detection method provided by the application has the advantages of simple operation, simple process, short detection time and good application potential.

Description

Technical Field

[0001] This invention belongs to the field of ion detection technology, specifically relating to a fluorescent probe and its detection method for detecting aluminum ions in tap water and food containing aluminum additives. This method can visually detect whether aluminum ions are present in tap water and food samples containing aluminum additives, selectively detect aluminum ions in these samples, and has anti-interference capabilities against other ions. Background Technology

[0002] Aluminum is the most widely distributed metallic element in nature. Due to its abundance and excellent properties, aluminum and its compounds are widely used in textiles, papermaking, industrial manufacturing, and food processing. However, worryingly, the harmful effects of aluminum accumulation on the natural environment and human health have become increasingly prominent and severe in recent years. The discharge of industrial waste and wastewater leads to the accumulation of large amounts of aluminum ions in the natural environment. High concentrations of aluminum ions can acidify soil, inhibit plant growth, and damage ecosystems. The potential toxicity of aluminum ions accumulated in aquatic organisms can affect their growth and development and even lead to death. Excessive intake of aluminum ions by the human body is difficult to eliminate quickly, and the aluminum ions retained in the body can cause long-term chronic toxic side effects. Increasing research shows that excessive aluminum ions have adverse effects on the central nervous system, digestive system, hematopoietic system, brain, liver, kidneys, and cells. For the brain and hippocampus, aluminum is a neurotoxic substance with a strong affinity, and its damage to the nervous system can easily lead to neurological diseases such as Parkinson's disease, Alzheimer's disease, airway encephalopathy, and memory decline. Aluminum can also bind to DNA in liver cells, causing liver damage. Frequent inhalation of aluminum dust can lead to widespread pulmonary fibrosis, triggering diseases such as pneumoconiosis, asthma, and decreased lung ventilation. Furthermore, aluminum chloride is toxic to embryos; excessive aluminum intake by pregnant women can cause abnormal fetal development. In 2017, the International Agency for Research on Cancer (IARC) of the World Health Organization published a preliminary list of carcinogens, and aluminum production processes were listed as Group 1 carcinogens.

[0003] According to the recommendations of the World Health Organization and the regulations of my country's Drinking Water Hygiene Standard GB 5749-2022, the aluminum content in drinking water should not exceed 0.2 mg / L. The Food Additives Standard GB 2760-2014 stipulates that the use of aluminum-containing additives in food production and processing should be in appropriate amounts, with residual aluminum not exceeding 100 mg / kg. The World Health Organization also recommends a maximum daily intake of aluminum of no more than 2 mg / kg per person per week. The aluminum content in natural water varies considerably due to different physical, chemical, and mineral factors. Generally, most water bodies in nature contain very little aluminum. However, in industrial production and drinking water purification processes, alum is often used as a flocculant, resulting in higher aluminum content in tap water. In the production of foods such as noodles and rice noodles, the use of aluminum-containing food additives is often unavoidable. Adding alum when making rice noodles improves their toughness, elasticity, and transparency, making them more chewy and less prone to falling apart when cooked in boiling water. my country has a history of flour milling spanning over a thousand years, and there's a saying that "vermicelli cannot be made without alum." Furthermore, to enhance the appearance and taste of food products, many vendors add large amounts of aluminum-based leavening agents to fried dough sticks, steamed buns, and puffed snacks. Given my country's large population and the significant proportion of flour and wheat-based foods in food consumption, the detection of aluminum content in tap water and food is of significant scientific and public health importance.

[0004] my country's national food safety standard for the determination of aluminum in food (GB 5009.182-2017) specifies that spectrophotometry is suitable for detecting aluminum in food additives, while inductively coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption spectrometry (GFAAS) are suitable for detecting aluminum in food. In addition, commonly used methods for aluminum ion detection include high-performance liquid chromatography (HPLC), electrochemical methods, and complexometric titration. These methods have high precision and reliability, but are limited by high cost, complex operation, low sensitivity, and long processing time, making it difficult to achieve convenient and rapid detection of aluminum ions. In recent years, fluorescence analysis has gained popularity in the field of aluminum ion detection. Fluorescence analysis has advantages such as high sensitivity, rapid response, simple operation, and good selectivity, enabling accurate and quantitative analysis of target substances under complex conditions. Compared with traditional methods such as chromatography, mass spectrometry, and spectrophotometry, fluorescence analysis is more likely to meet the requirements of rapid, convenient, visual, and on-site detection of aluminum ions.

[0005] The fluorescence intensity of the system changes due to the chemical reaction between aluminum ions and the fluorophore in the fluorescent probe. This is the principle and basis of fluorescence analysis for detecting aluminum ions. Currently, fluorescence analysis has made some progress in the field of aluminum ion detection, but many problems remain to be solved. Chinese patent CN116223460A, "A Rapid Detection Method for Aluminum Ions in Food," provides a fluorescent probe 1-phenyl-3-diferrocenylenone and a detection method for detecting aluminum ions in food. This method is simple to operate and time-saving, but it can only qualitatively detect the presence or absence of aluminum ions in food samples based on changes in fluorescence spectra, and cannot provide accurate quantitative analysis of aluminum ion content. Chinese patent CN113884476A, "A Sensor for Detecting Aluminum Ions and a Method for Detecting Aluminum Ions," prepares a europium-doped carbon quantum dot ratiometric fluorescent probe. This fluorescent probe is obtained by reacting citric acid, melamine, and Eu(NO3)3·6H2O dissolved in formaldehyde solution at a high temperature of 200℃. A fluorescent sensor solution obtained by dissolving tetracycline and europium-doped carbon quantum dot ratiometric probes together in water can achieve quantitative and visual detection of aluminum ions. However, the europium, melamine, and formaldehyde in the raw materials are highly toxic and pose serious threats to human health and the environment. Chinese patent CN115745868A, "A method for detecting Al...", is relevant. 3+ The paper "A Fluorescent Probe, Its Preparation Method, and Its Application" discloses a fluorescence-enhanced aluminum ion detection probe and its preparation method. This method exhibits high sensitivity for aluminum ion detection, with a detection limit of 1.486 μM and a response range of 0–500 μM. The fluorescent probe is prepared from 4-nitro-(4'-fluoro)benzophenone, carbazole, and salicylaldehyde through a series of reactions. The preparation process involves the synthesis of multiple intermediate compounds, with a total reaction time exceeding 60 hours, making it complex and costly. Therefore, developing a green, environmentally friendly, simple, convenient, and rapid-response high-sensitivity aluminum ion detection method is of great significance. Summary of the Invention

[0006] To address the shortcomings and deficiencies of existing fluorescence analysis methods for detecting aluminum ions, this invention aims to provide a fluorescent probe and detection method for detecting aluminum ions in tap water and aluminum-containing food additives, thereby achieving a simple, convenient, green, and environmentally friendly aluminum ion detection method.

[0007] This invention uses natural polyphenol rosin as an aluminum ion fluorescent probe. After the fluorescent probe complexes with aluminum ions, it can enhance the fluorescence intensity at a specific wavelength. By measuring the relationship between aluminum ion concentration and fluorescence intensity, a standard curve and a linear equation for aluminum ion detection can be obtained. Using the standard curve and the linear equation, the quantitative detection of aluminum ions in tap water and aluminum-containing food additives can be achieved.

[0008] Fisetin is a widely distributed natural polyphenol compound in the plant kingdom, also known as 3,3′,4′,7-tetrahydroxyflavone. It exists in various plants and possesses diverse pharmacological activities, such as anti-inflammatory, anti-allergic, uric acid-lowering, antitumor, antibacterial, and antiviral effects. It can be directly extracted from plants, making the raw materials readily available and inexpensive. Compared to other chemically synthesized fluorescent probes, natural polyphenols have low biotoxicity and do not require extensive organic synthesis reactions, making them environmentally friendly and human-friendly. Fisetin responds rapidly to aluminum ions, with its solution immediately changing from colorless to yellow upon response. Furthermore, in the application of aluminum ion detection in tap water and aluminum-containing food samples, the detection method provided by this invention is simple to implement and operate. The fluorescent probe exhibits good selectivity for aluminum ion detection, enabling visual detection of aluminum ions under handheld ultraviolet light. It also selectively detects aluminum ions in tap water and aluminum-containing food samples, while also detecting other ions such as Cu. 2+ Fe 2+ Fe 3+ Zn 2+ Mg 2+ Na + K + Ca 2+ Ba 2+ Cr 3+ Li + Co 2+ Ni 2+ It has anti-interference capabilities.

[0009] The molecular structure of rosin, a fluorescent probe for detecting aluminum ions in tap water and aluminum-containing food additives provided by this invention, is shown below:

[0010]

[0011] This invention provides a method for detecting aluminum ions in tap water and food containing aluminum additives, comprising the following steps:

[0012] (1) Dissolve the fluorescent probe lacquinone in a solvent stock solution to prepare a probe solution;

[0013] (2) Pre-treatment and spiked treatment were performed on tap water samples, while pre-treatment was performed on food samples containing aluminum additives without spiked treatment, resulting in spiked tap water samples and unspecified food samples containing aluminum additives; the standard used for spiked treatment was aluminum salt.

[0014] (3) Take a spiked sample of tap water and an unspiked sample of food containing aluminum additives respectively and add them to the probe solution to obtain the test sample solution. After the response is complete, use a fluorescence spectrometer to measure the fluorescence intensity of the test sample solution at 487nm. The aluminum ion content in the test sample solution is calculated by the linear equation of the fitted curve of the detection standard curve.

[0015] Preferably, in step (1), the solvent stock solution is an aqueous ethanol solution (EtOH:H2O = 1:1, v:v).

[0016] Preferably, in step (1), the concentration range of the probe solution is 25–35 μM.

[0017] Preferably, in step (2), the aluminum salt includes any one of aluminum chloride hexahydrate, aluminum sulfate, and aluminum nitrate.

[0018] Preferably, in step (2), the following is true:

[0019] The specific procedures for pretreatment and spiking of tap water are as follows: centrifuge the tap water sample at a speed of 3000-4000 r / min for 5-10 min, then filter the insoluble matter in the water sample with qualitative filter paper, add aluminum salt to the centrifuge tube according to different spiking concentrations, add an appropriate amount of filtrate to dissolve, and thus obtain tap water spiked sample solutions with different spiking concentrations.

[0020] For food samples containing aluminum additives, pretreatment is sufficient and no spiking is required. The specific procedure is as follows: Dry the food sample containing aluminum additives in an oven at 100-110℃, and then grind it into powder in a mortar. Add an appropriate amount of the aluminum additive food sample powder and water to centrifuge tubes, and then add a small amount of dilute hydrochloric acid to promote the dissolution of aluminum ions. Centrifuge at 3000-4000 r / min for 5-10 min, filter, and add an appropriate amount of NaOH solution to neutralize the solution, thus obtaining the unspiked aluminum additive food sample solution.

[0021] Preferably, in step (3), the excitation wavelength of the fluorescence spectrometer is set to 365 nm.

[0022] Preferably, in step (3), the detection is carried out at room temperature throughout, and the flavonoid in the probe solution and the aluminum ions in the sample solution respond completely within 10 minutes.

[0023] Preferably, in step (3), the steps for plotting the linear equations of the standard curve and the fitted curve are as follows:

[0024] (1) Dissolve lacquinone in a solvent stock solution to obtain lacquinone stock solution; dissolve aluminum salt in a solvent stock solution to obtain aluminum ion stock solution;

[0025] (2) A series of lacquer-Al solutions were obtained by adding solvent stock solution and aluminum ion stock solution of different concentrations to lacquer stock solution. 3+ Test solution;

[0026] (3) Measurement of laccase-Al using a fluorescence spectrometer 3+The fluorescence intensity of the test solution at 487 nm was measured, and the fluorescence intensity data was processed to obtain the standard curve and the linear equation of the fitted curve for aluminum ion detection.

[0027] Preferably, in step (1), the concentration of the laccoside stock solution is 3 mM and the concentration of the aluminum ion stock solution is 3 mM.

[0028] Preferably, in step (2), laccasein-Al 3+ The concentration range of aluminum ions in the test solution is 5–60 μM. A larger concentration of aluminum ion stock solution can be diluted to this concentration range before testing.

[0029] The aluminum ion detection method of this invention exhibits a good linear relationship between the fluorescence intensity of the sample solution and the aluminum ion concentration. The linear equation of the fitted curve is Y = 222.87 + 7.22*X (where X is the aluminum ion concentration and Y is the fluorescence emission peak intensity). The detection limit of lacquer xanthocyanin for aluminum ions is 0.52 μM. Furthermore, in the selective detection experiments of different metal ions, only the lacquer xanthocyanin solution with added aluminum ions emitted bright blue fluorescence under a handheld ultraviolet lamp. Therefore, lacquer xanthocyanin, as a fluorescent probe, can achieve selective and visual detection of aluminum ions.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The aluminum ion detection fluorescent probe provided by the present invention is lacquinone, which is a natural polyphenol that can be directly extracted from plants. It does not require a large amount of organic synthesis reaction to prepare. The raw materials are readily available and inexpensive, and can be purchased directly. Natural polyphenols have low biological toxicity and are friendly to the human body and the environment.

[0032] (2) The fluorescent probe provided by this invention exhibits good selectivity for aluminum ion detection, is unaffected by interference from other metal ions, and has a fast response speed. Within the aluminum ion solution concentration range of 5–60 μM, the fluorescence intensity of this fluorescent probe shows a good linear relationship with the aluminum ion concentration (R0). 2 =0.99), with a detection limit of 0.52 μM for aluminum ions, exhibiting high sensitivity and rapid response.

[0033] (3) The aluminum ion detection method provided by this invention has a simple process, is easy to operate, and has a short detection time. It can identify whether tap water and food samples contain aluminum ions under the illumination of a handheld ultraviolet lamp, realizing visual detection. Attached Figure Description

[0034] Figure 1 The UV-Vis absorption and fluorescence emission spectra of the laccoside test sample solution (30 μM) are shown.

[0035] Figure 2The fluorescence emission spectra of the laccoside test sample solution (30 μM) before and after the addition of aluminum ions (60 μM) are shown.

[0036] Figure 3 The graph shows the relationship between fluorescence intensity at 487 nm and time after rutin responds to aluminum ions.

[0037] Figure 4 The fluorescence emission spectra are those of rutin in response to various metal ions.

[0038] Figure 5 This is a bar chart comparing the fluorescence intensity of laccosin at 487 nm after its response to various metal ions.

[0039] Figure 6a The images show a comparison of laccase reacting with various metal ions under natural light and 365nm ultraviolet light.

[0040] Figure 6b The images show grayscale values ​​of lacquer yellow pigment in response to various metal ions under natural light and 365nm ultraviolet light.

[0041] Figure 7 The fluorescence emission spectra of rutin (30 μM) in response to different concentrations of aluminum ions (0–200 μM) are shown.

[0042] Figure 8 The graph shows the linear relationship between fluorescence intensity at 487 nm and aluminum ion concentration after lacquinone responds to aluminum ions. Detailed Implementation Plan

[0043] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. The described embodiments are only a part of the embodiments of the present invention, but the implementation of the present invention is not limited to the following scope. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0044] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods, and the materials and reagents used in the experiments are all obtained from commercial sources. All reagents selected in the embodiments are commercially available analytical grade or chemically pure.

[0045] Example 1: Test of fluorescence properties of lacquer xanthocyanin in response to aluminum ions and determination of standard curve for aluminum ion detection.

[0046] (1) Preparation of various stock solutions

[0047] The solvent in both the solvent stock solution and the test sample solution was an aqueous solution of ethanol (EtOH:H2O = 1:1, v:v). 500 mL of water and 500 mL of ethanol were measured into beakers and mixed thoroughly to obtain the solvent stock solution.

[0048] Preparation of lacquer xanthocyanin stock solution: Weigh 25.8 mg of lacquer xanthocyanin and dissolve it in 30 mL of solvent stock solution to obtain lacquer xanthocyanin stock solution (3 mM).

[0049] Preparation of 14 metal ion stock solutions: 14.4 mg (CuSO4), 36.0 mg (Fe2(SO4)3), 14.5 mg (ZnSO4), 13.7 mg (FeSO4), 8.6 mg (MgCl2), 5.3 mg (NaCl), 6.7 mg (KCl), 21.7 mg (AlCl3·6H2O), 10.0 mg (CaCl2), 18.7 mg (BaCl2), 14.3 mg (CrCl3), 3.8 mg (LiCl), 11.7 mg (CoCl2), and 11.8 mg (NiCl2) of metal ion compound powder were weighed and dissolved in 30 mL of solvent stock solution to obtain various metal ion stock solutions (3 mM).

[0050] (2) UV-Vis absorption and fluorescence emission spectra of laccase before and after aluminum ion response

[0051] Using a pipette, transfer 30 μL of lacquer xanthocyanin stock solution into two centrifuge tubes. Add 2.97 mL of solvent stock solution to one centrifuge tube and mix thoroughly to obtain the lacquer xanthocyanin test sample solution (30 μM). Add 2.91 mL of solvent stock solution and 60 μL of AlCl3·6H2O stock solution (aluminum ion concentration 60 μM) to the other centrifuge tube and mix thoroughly to obtain lacquer xanthocyanin-Al 3+ The test sample solutions were allowed to stand for 30 minutes before being used for testing.

[0052] The laccoside test sample solution was placed in a UV-Vis spectrophotometer, and its UV-Vis absorption spectrum was measured. For example... Figure 1 As shown, the absorbance of the lacquer xanthocyanin test sample solution peaks at 365 nm. The lacquer xanthocyanin test sample solution was placed in a fluorescence spectrometer, the excitation wavelength was set to 365 nm, and its fluorescence emission spectrum was measured. Figure 1 As shown, the fluorescence intensity of the laccoside test sample solution showed two peaks at 465 nm and 527 nm, respectively.

[0053] The above-mentioned lacquinone test sample solution and lacquinone-Al were measured using a fluorescence spectrometer. 3+ The fluorescence emission spectrum of the sample solution was tested, with the excitation wavelength set to 365 nm. For example... Figure 2As shown, after the addition of aluminum ions, the two fluorescence intensity peaks of 465nm and 527nm of lacquer xanthophyll disappeared, while a stronger fluorescence intensity peak appeared at 487nm. This indicates that lacquer xanthophyll has the potential to serve as a fluorescent probe for responding to and detecting aluminum ions.

[0054] (3) Response time test of lacquer yellow pigment to aluminum ions

[0055] Transfer 30 μL of lacquinone stock solution into a quartz cuvette, then add 2.91 mL of solvent stock solution and 60 μL of AlCl3·6H2O stock solution. Shake rapidly until homogeneous, and immediately use a fluorescence spectrometer to measure the change in fluorescence intensity of the test sample solution over time. Figure 3 As shown, upon the addition of aluminum ions, the fluorescence intensity of the test solution at 487 nm rapidly increased, and simultaneously, the lacquer xanthocyanin solution immediately turned yellow. Within 10 minutes of adding aluminum ions, the fluorescence intensity of the test solution tended to stabilize. These results indicate that lacquer xanthocyanin exhibits a rapid recognition response to aluminum ions and can be applied to the rapid detection of aluminum ions.

[0056] (4) Selectivity detection test of lacquer xanthocyanin for aluminum ions

[0057] Using a pipette, 30 μL of lacquer xanthocyanin stock solution was transferred into 14 centrifuge tubes. 2.91 mL of solvent stock solution was added to each tube, followed by 60 μL of various metal ion stock solutions. After thorough mixing, test sample solutions were obtained, showing the lacquer xanthocyanin response to each of the 14 metal ions. After standing for 30 min, the fluorescence emission spectra of each test sample solution were measured using a fluorescence spectrometer with an excitation wavelength set to 365 nm.

[0058] like Figure 4 As shown, only the test sample solution with added aluminum ions exhibited a significantly enhanced fluorescence intensity, while the fluorescence intensity of the test sample solutions with added copper, iron, and ferrous ions was significantly weakened, and the fluorescence intensity of the remaining test sample solutions showed no significant change. The fluorescence intensity of each test sample solution was compared with that of the lacquer xanthocyanin solution without any added metal ions at 487 nm. Figure 5 As shown, it can be seen that rosin has excellent selective response and detection performance to aluminum ions.

[0059] Each of the above test sample solutions was poured into a quartz cuvette, and photographed under natural light and 365nm ultraviolet light, respectively. The results are as follows. Figure 6a and Figure 6b As shown. Under natural light, lacquer yellow pigment - Al 3+ The solution is bright yellow, containing laccasein-Cu. 2+ The solution is yellow, containing laccasein-Fe 3+The solution is pale yellow and contains laccasein-Fe. 2+ The solution was pale brown, while the other solutions were all transparent and colorless, consistent with the lacquer yellow solution without added metal ions. Under 365nm ultraviolet light irradiation, only lacquer yellow-Al... 3+ The solution emitted a strong bright blue fluorescence, while the other solutions emitted no fluorescence or very weak fluorescence. This demonstrates that using flavonoids as a fluorescent probe not only allows for the selective detection of aluminum ions using fluorescence spectroscopy, but also enables convenient and visual detection of aluminum ions in solution under handheld ultraviolet light.

[0060] (5) Determination of the standard curve for the detection of aluminum ions by rosin

[0061] 30 μL of lacquer xanthocyanin stock solution was transferred to different centrifuge tubes. Then, 2.97 mL, 2.96 mL, 2.95 mL, 2.94 mL, 2.93 mL, 2.92 mL, 2.91 mL, 2.89 mL, 2.87 mL, 2.83 mL, 2.81 mL, and 2.77 mL of solvent stock solution were added sequentially to each centrifuge tube. Then, 0 μL, 10 μL, 20 μL, 30 μL, 40 μL, 50 μL, 60 μL, 80 μL, 100 μL, 140 μL, 160 μL, and 200 μL of AlCl3·6H2O stock solution were added sequentially to each centrifuge tube. This yielded a series of test sample solutions of lacquer xanthocyanin (30 μM) responding to different concentrations of aluminum ions (0–200 μM). The fluorescence emission spectra of these test sample solutions were measured using a fluorescence spectrometer. The results are shown below. Figure 7 As shown, the fluorescence intensity of the test sample solution at 487 nm gradually increases with increasing aluminum ion concentration.

[0062] Following the above procedure, a smaller aluminum ion concentration gradient was set to prepare a series of test sample solutions showing the response of rutin (30 μM) to different concentrations of aluminum ions (0–60 μM). The fluorescence intensity of the sample solutions at 487 nm was measured using a fluorescence spectrometer. Linear fitting was performed on each fluorescence intensity data point. Figure 8 It can be seen that within the aluminum ion concentration range of 0–60 μM, the fluorescence intensity of the test sample solution exhibits a good linear relationship with the aluminum ion concentration (R0). 2=0.99), indicating that lacquer xanthocyanin holds promise for the detection and quantitative analysis of aluminum ion concentration. The linear equation of the fitted curve is Y = 222.87 + 7.22*X (where X is the aluminum ion concentration and Y is the fluorescence emission peak intensity). Based on the detection limit equation LOD = 3σ / k (where σ is the standard deviation of the blank sample and k is the slope of the fitted curve), the detection limit of lacquer xanthocyanin for aluminum ions is calculated to be 0.52 μM. This detection limit is far lower than the maximum residual limit of aluminum ions specified in the Drinking Water Hygiene Standard GB 5749-2022 (0.2 mg / L, i.e., 7.41 μM). This demonstrates that lacquer xanthocyanin has high sensitivity for detecting aluminum ions and can effectively detect trace amounts of aluminum in the sample.

[0063] Example 2: Detection of aluminum ions in tap water spiked with lacquer xanthocyanin

[0064] Tap water was collected from the laboratory and pretreated and spiked: the tap water samples were centrifuged at 3000-4000 r / min for 5-10 min, and the insoluble matter was filtered out using qualitative filter paper. 1.81 mg, 3.62 mg, 5.43 mg, and 7.24 mg of AlCl3·6H2O crystals were added to four centrifuge tubes according to different spiking concentrations, respectively. A suitable amount of filtrate was added to dissolve the crystals, resulting in four groups of tap water sample solutions with spiking concentrations of 2.50 μM, 5.00 μM, 7.50 μM, and 10.00 μM.

[0065] Take 12 centrifuge tubes, add 30 μL of lacquinone stock solution and 2.91 mL of solvent stock solution to each, mix well, and divide the 12 centrifuge tubes into 4 groups. Add 60 μL of tap water sample solution with different spiking concentrations to each of the 4 groups of centrifuge tubes to obtain 4 groups of spiked detection sample solutions for aluminum ion detection (2.50 μM, 5.00 μM, 7.50 μM, 10.00 μM). The aluminum ion concentration in each of the 3 centrifuge tubes in each group is the same. Take 3 parallel experiments and calculate the relative standard deviation. Use a fluorescence spectrometer to measure the fluorescence intensity of the 4 groups of spiked detection sample solutions at 487 nm. Calculate the actual measured value of aluminum ion content in each group of spiked sample solutions using the aluminum ion detection standard curve obtained in Example 1. Finally, calculate the recovery rate and relative standard deviation (RSD).

[0066] Table 1

[0067]

[0068] As shown in Table 1, the recoveries of aluminum ions in the four groups of spiked tap water samples ranged from 98.53% to 101.87%, with relative standard deviations all less than 3%. The detected aluminum ion concentrations showed minimal error compared to the corresponding spiked concentrations. This indicates that laccasein has high accuracy in detecting aluminum ions in actual tap water samples and shows promising application prospects.

[0069] Example 3: Detection of aluminum ions in unspecified samples of high-tenacity instant vermicelli (aluminum-containing additive food) using urochrome.

[0070] Three brands of high-tenacity instant vermicelli were obtained through online purchase and pretreated as follows: the vermicelli was dried in an oven at 100-110℃, and 10g of each type of vermicelli was weighed and ground into powder in a mortar. 10g of vermicelli powder and 10mL of water were added to three centrifuge tubes, followed by a small amount of dilute hydrochloric acid to promote aluminum ion dissolution. The tubes were centrifuged at 3000-4000 rpm for 5-10 minutes, filtered, and an appropriate amount of NaOH solution was added to neutralize the solution, resulting in three groups of unspecified high-tenacity instant vermicelli sample solutions. Nine centrifuge tubes were divided into three groups. Each group was mixed with 30 μL of lacquer xanthocyanin stock solution and 2.91 mL of solvent stock solution. Then, 60 μL of unspecified vermicelli sample solutions from three different brands were added to each group of centrifuge tubes to obtain unspecified detection solutions for aluminum ions in three different brands of vermicelli. The aluminum ion concentration was the same in each of the three centrifuge tubes. Three parallel experiments were conducted, and the relative standard deviation was calculated. The fluorescence intensity of the three unspecified detection solution groups at 487 nm was measured using a fluorescence spectrometer. The actual measured value of aluminum ion concentration in each detection solution group was calculated using the aluminum ion detection standard curve obtained in Example 1. This was then converted to obtain the actual measured value of aluminum ion mass concentration in the high-tenacity instant vermicelli. Finally, the exceedance rate and relative standard deviation (RSD) were calculated.

[0071] Table 2

[0072]

[0073] The test results are shown in Table 2. The aluminum ion content in the three groups of unlabeled vermicelli samples were 213.54 mg / Kg, 167.93 mg / Kg, and 148.52 mg / Kg, respectively, all exceeding the maximum limit of 100 mg / Kg specified in the Food Additives Standard GB 2760-2014. The maximum exceedance rate was 113.54%. The test results indicate that there are still many aluminum-containing food additives on the market with excessive aluminum content. The detection method provided by this invention can effectively detect various aluminum-containing food additives with excessive aluminum content, which is of great significance for ensuring food safety and public health.

Claims

1. A method for detecting aluminum ions in tap water and aluminum-containing food additives, characterized in that, Includes the following steps: (1) The fluorescent probe lacquinone is dissolved in a solvent stock solution to prepare a probe solution; the solvent stock solution is an aqueous ethanol solution, wherein the volume ratio of ethanol to water is 1:1; the concentration range of the probe solution is 25~35 μM; (2) Pre-treat and spike the tap water sample to obtain spiked tap water sample; pre-treat the aluminum-containing food sample without adding the spike to obtain unspecified aluminum-containing food sample. The specific operations for pretreatment and spiking of tap water are as follows: centrifuge the tap water sample, then filter the insoluble matter in the water sample with qualitative filter paper, add aluminum salt to the centrifuge tube according to different spiking concentrations, and add filtrate to dissolve, thus obtaining tap water spiked sample solutions with different spiking concentrations. The specific operation of pre-treating the aluminum-containing food sample without adding the additive is as follows: dry the aluminum-containing food sample in an oven, then grind it into powder in a mortar, add the food sample powder, water, and dilute hydrochloric acid to a centrifuge tube, sonicate, centrifuge, filter, add NaOH solution to make the solution neutral, and thus obtain the aluminum-containing food sample solution without the additive. (3) Spiked tap water and unspiked aluminum-containing food samples were added to the probe solution to obtain the test sample solution. After the response was complete, the fluorescence intensity of the test sample solution at 487 nm was measured using a fluorescence spectrometer. The aluminum ion content in the test sample solution was calculated by the linear equation of the fitted curve of the detection standard curve. The excitation wavelength of the fluorescence spectrometer was set to 365 nm. The entire detection process was carried out at room temperature. The lacquinone in the probe solution and the aluminum ions in the test sample solution responded completely within 10 min. The laccosin has a detection limit of 0.52 μM for aluminum ions and can be used to visually detect whether tap water and food samples containing aluminum additives contain aluminum ions under ultraviolet light. It can also selectively detect aluminum ions in tap water and food samples containing aluminum additives and has anti-interference ability against other ions.

2. The method according to claim 1, characterized in that, The aluminum salt includes any one of aluminum chloride hexahydrate, aluminum sulfate, and aluminum nitrate.

Images