Dual-mode rapid chromium detection method

Abstract

The embodiment of the invention discloses a dual-mode rapid chromium detection method which comprises the following steps: firstly, determining a first linear relationship between the Cr (VI) concentration and fluorescence intensity I based on an MIL-101 (Fe)-NH2 material, Cr (VI) standard solutions with different concentrations and ascorbic acid, and determining a second linear relationship between the Cr (VI) concentration and absorbance A based on the MIL-101 (Fe)-NH2 material, the Cr (VI) standard solutions with different concentrations and TMB (Tetramethylbenzidine). After the first linear relation and the second linear relation are obtained, the Cr (VI concentration in the sample determination liquid is determined on the basis of the first linear relation and the second linear relation, a Cr (VI detection method through a fluorescence / colorimetric dual mode has a wide linear range (7.5-750 [mu] g / L and 13.3-1000 [mu] g / L) and a low detection limit (0.99 [mu] g / L and 1.98 [mu] g / L), and related requirements can be met; the method has the characteristics of simplicity in operation, high sensitivity, rapidness and the like.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of chemical analysis and detection, and in particular to a method for rapid dual-mode detection of chromium. Background Art

[0002] The heavy metal element chromium is a key detection indicator in cigarettes and tobacco materials. It may come from the chromium absorbed and enriched from the environment by tobacco crops during their growth, or from trace amounts of chromium in tobacco auxiliary materials such as flavors and fragrances, water-based adhesives, cigarette paper, and cigarette tipping paper used in the cigarette processing process. During the smoking process of cigarettes, if chromium is present, it may enter the body with mainstream smoke, thus causing harm to human health. The common valence states of chromium are trivalent and hexavalent. Hexavalent chromium is 100 times more toxic than trivalent chromium. Inhalation can damage the lungs and kidneys and has a strong carcinogenic effect. Therefore, accurate determination of the hexavalent chromium content in tobacco and related products is of great significance for the evaluation of the hazard of cigarettes. At present, the determination methods of Cr mainly include atomic absorption spectrometry (AAS), inductively coupled plasma mass spectrometry (ICP-MS), electrochemical method and colorimetric probe method. Instrumental analysis requires precise instruments and professional operators. Compared with other methods, colorimetry and fluorescence methods have the advantages of simplicity, rapidity, and high sensitivity. They are often used for rapid on-site monitoring, but their sensitivity threshold is usually high. The detection media in traditional technologies are complex to operate and have low sensitivity, which leads to low detection efficiency. Therefore, the development of new systems that can amplify the fluorescence or absorbance signals of trace analytes and achieve detection and quantification at lower concentrations is a very active research field. Summary of the invention

[0003] A series of simplified concepts are introduced in the Summary of the Invention, which will be further described in detail in the Detailed Description of the Invention. This part of the invention does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the scope of protection of the claimed technical solution.

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0005] In view of this, the present application proposes a dual-mode rapid detection method for chromium, comprising:

[0006] Based on MIL-101(Fe)-NH 2 materials, Cr(VI) standard solutions of different concentrations and ascorbic acid, and determining the first linear relationship between Cr(VI) concentration and fluorescence intensity I;

[0007] Based on MIL-101(Fe)-NH 2materials, Cr(VI) standard solutions of different concentrations and TMB, and determining the second linear relationship between Cr(VI) concentration and absorbance A;

[0008] Cr(VI) in the detection sample is digested to obtain a sample test solution, and the concentration of Cr(VI) in the sample test solution is determined based on the first linear relationship and the second linear relationship.

[0009] In a feasible embodiment, the MIL-101(Fe)-NH 2 Materials, Cr(VI) standard solutions of different concentrations and ascorbic acid, the steps of determining a first linear relationship between Cr(VI) concentration and fluorescence intensity I include:

[0010] The Cr(VI) standard solutions of different concentrations were mixed with ascorbic acid and then added to MIL-101(Fe)-NH 2 Nanomaterials;

[0011] Use pH 6.8 MES buffer solution to make up to 3 mL, shake well, and let stand for 5-10 minutes;

[0012] The fluorescence intensity was measured at an excitation wavelength of 352 nm and an emission wavelength of 448 nm to determine the first linear relationship between the Cr(VI) concentration and the fluorescence intensity I.

[0013] In a feasible embodiment, the ascorbic acid concentration is 1 mg / mL and the volume is 15-20 μL.

[0014] In a feasible embodiment, the MIL-101(Fe)-NH 2 The steps of preparing the second linear relationship between the concentration of Cr(VI) and the absorbance A include:

[0015] The Cr(VI) standard solutions with different concentrations were mixed with MIL-101(Fe)-NH 2 Nanomaterials, TMB and H 2 O 2 mix;

[0016] Make up to 3 mL with pH 4.0 acetate buffer solution, shake well, and let stand for 5-10 minutes;

[0017] The absorbance was measured at a wavelength of 652 nm to determine the second linear relationship between the Cr(VI) concentration and the absorbance A.

[0018] In a feasible embodiment, the TMB concentration is 5 mmol / L, and the volume is 40-80 μL;

[0019] The H 2 O2 The concentration is 50mmol / L and the volume is 40-80μL.

[0020] In a feasible implementation manner, the concentration of the Cr(VI) standard solution used to obtain the first linear relationship is 7.5-750 μg / L.

[0021] In a feasible implementation manner, the concentration of the Cr(VI) standard solution used to obtain the second linear relationship is 1-100 μg / L.

[0022] In a feasible embodiment, the MIL-101(Fe)-NH 2 The material is MIL-101(Fe)-NH with a concentration of 2 mg / mL and an addition amount of 50-100 μL. 2 Nanomaterial solutions.

[0023] In a feasible embodiment, in the MIL-101(Fe)-NH 2 Materials, Cr(VI) standard solutions of different concentrations and ascorbic acid, before the step of determining the first linear relationship between Cr(VI) concentration and fluorescence intensity I, the method further comprises:

[0024] Based on 2-aminoterephthalic acid, FeCl 3 6H 2 Preparation of MIL-101(Fe)-NH 2 Material.

[0025] In a feasible embodiment, the 2-aminoterephthalic acid, FeCl 3 6H 2 Preparation of MIL-101(Fe)-NH 2 The material steps include:

[0026] 2.5-3.0 mmol of 2-aminoterephthalic acid, 5-6 mmol of FeCl 3 6H 2 O was added to 35-45 mL of DMF and sonicated for 15-20 min;

[0027] The solution was transferred into a polytetrafluoroethylene reaction tank and placed in a muffle furnace and heated at 110-120°C for 24 hours. After the reaction was completed, it was naturally cooled to room temperature.

[0028] Wash with anhydrous ethanol and DMF 3-4 times each, and dry in vacuum to obtain MIL-101(Fe)-NH 2 .

[0029] Compared with the prior art, the present invention has at least the following beneficial effects:

[0030] The dual-mode rapid detection method of chromium provided in the embodiment of the present application is first based on MIL-101(Fe)-NH 2 Materials, different concentrations of Cr(VI) standard solutions and ascorbic acid were used to determine the first linear relationship between Cr(VI) concentration and fluorescence intensity I based on MIL-101(Fe)-NH 2 Materials, Cr(VI) standard solutions of different concentrations and TMB are used to determine the second linear relationship between the Cr(VI) concentration and the absorbance A. After obtaining the first linear relationship and the second linear relationship, the Cr(VI) concentration in the sample determination solution is determined based on the first linear relationship and the second linear relationship. The fluorescence / colorimetric dual-mode Cr(VI) detection method has a wide linear range (7.5-750 μg / L and 13.3-1000 μg / L) and a low detection limit (0.99 μg / L and 1.98 μg / L), which can meet relevant requirements; the method has the characteristics of simple operation, high sensitivity, rapidity, etc.

[0031] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0033] Figure 1 A schematic flowchart of the steps of a dual-mode rapid detection method of chromium according to an embodiment of the present application;

[0034] Figure 2 MIL-101(Fe)-NH prepared in Example 1 of the present invention 2 TEM images of

[0035] Figure 3 TEM image of MIL-101(Fe)-NH2+AA in Example 1 of the present invention;

[0036] Figure 4 MIL-101(Fe)-NH 2 、MIL-101(Fe)-NH 2 +AA and MIL-101(Fe)-NH 2 + AA + Cr (VI) fluorescence spectrum;

[0037] Figure 5 MIL-101(Fe)-NH 2 +TMB+H 2 O 2 and

[0038] MIL-101(Fe)-NH 2 +TMB+H 2 O 2 +Visible absorption spectrum of Cr(VI);

[0039] Figure 6a and Figure 6b MIL-101(Fe)-NH 2 + AA system to detect fluorescence spectrum and linear equation of Cr(VI);

[0040] Figure 7a and Figure 7b MIL-101(Fe)-NH 2 +TMB+H 2 O 2 The system detects the UV absorption spectrum and linear equation of Cr(VI);

[0041] Figure 8a and Figure 8b The results of the effects of the coexisting substances in fluorescence and visible absorption spectra on Cr(VI) in Example 1 are shown. DETAILED DESCRIPTION

[0042] In the following description, a large number of specific details are given to provide a more thorough understanding of the technical solutions provided by the present invention. However, it is obvious to those skilled in the art that the technical solutions provided by the present invention can be implemented without one or more of these details.

[0043] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of the features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0044] Now, exemplary embodiments according to the present invention will be described in more detail with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in a variety of different forms and should not be interpreted as being limited to the embodiments set forth herein. It should be understood that these embodiments are provided to make the disclosure of the present invention thorough and complete, and to fully convey the concept of these exemplary embodiments to those of ordinary skill in the art.

[0045] like Figure 1 As shown, the embodiment of the present application proposes a dual-mode rapid detection method for chromium, comprising:

[0046] Step 101: Based on MIL-101(Fe)-NH 2 materials, Cr(VI) standard solutions of different concentrations and ascorbic acid, and determining the first linear relationship between Cr(VI) concentration and fluorescence intensity I;

[0047] Step 102: Based on MIL-101(Fe)-NH 2 materials, Cr(VI) standard solutions of different concentrations and TMB, and determining the second linear relationship between Cr(VI) concentration and absorbance A;

[0048] Step 103: digest Cr(VI) in the test sample to obtain a sample test solution, and determine the Cr(VI) concentration in the sample test solution based on the first linear relationship and the second linear relationship.

[0049] The dual-mode rapid detection method of chromium provided in the embodiment of the present application is first based on MIL-101(Fe)-NH 2 Materials, different concentrations of Cr(VI) standard solutions and ascorbic acid were used to determine the first linear relationship between Cr(VI) concentration and fluorescence intensity I based on MIL-101(Fe)-NH 2 Materials, Cr(VI) standard solutions of different concentrations and TMB are used to determine the second linear relationship between the Cr(VI) concentration and the absorbance A. After obtaining the first linear relationship and the second linear relationship, the Cr(VI) concentration in the sample determination solution is determined based on the first linear relationship and the second linear relationship. The fluorescence / colorimetric dual-mode Cr(VI) detection method has a wide linear range (7.5-750 μg / L and 13.3-1000 μg / L) and a low detection limit (0.99 μg / L and 1.98 μg / L), which can meet relevant requirements; the method has the characteristics of simple operation, high sensitivity, rapidity, etc.

[0050] The present application takes into account that metal-organic frameworks (MOFs) are a class of inorganic-organic hybrid materials assembled by coordination of metal ions or metal clusters with organic bridging ligands. MOFs are highly diverse in structure and properties, and usually exhibit advantages such as high porosity, high specific surface area, open functional sites, adjustable pore size and high chemical / thermal stability. Luminescent MOFs (LMOFs), as a new type of organic-inorganic hybrid functional material, have been widely used as luminescent sensors for sensitive and selective detection of small organic molecules, metal ions, temperature, amino acids and antibiotics because of their advantages such as modifiable luminescent response sites, tailorable structures and adjustable pore size. The inherent permanent porosity of MOFs can also achieve encapsulation or adsorption of guest luminescent species, thereby obtaining guest molecule-induced LMOFs, and their luminescent properties can be conveniently regulated by rationally selecting suitable guest luminescent species and host MOFs.

[0051] Furthermore, MIL-101(Fe)-NH 2 Has dual functions: 2-aminoterephthalic acid (NH 2 -BDC) ligand has strong fluorescence emission at 428nm, and the Fe central ion has peroxidase-like catalytic activity, which can oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) substrate to blue oxTMB. Reducing substances such as ascorbic acid (AA) can make MIL-101 (Fe)-NH 2 The structure of AA collapses due to the iron reduction, which leads to the release of fluorescent NH 2 -BDC. When Cr(VI) is present, due to Fe 3+ The reduction of MIL-101(Fe)-NH 2 The fluorescence intensity of the +AA system decreased, and the Fe 3+ and Fe 2+ The electron transfer rate of MIL-101(Fe)-NH 2 The rate of oxidation of TMB was significantly accelerated. 2 , using AA to synthesize MIL-101(Fe)-NH 2Nanomaterials are reduced to produce fluorescence and have intrinsic peroxidase-like properties, and Fe(III) has an inhibitory and sensitizing effect on the detection system, so a Cr(VI) fluorescence / colorimetric dual-mode rapid detection method was established. This method has a wide linear range (7.5-750μg / L and 13.3-1000μg / L) and a low detection limit (0.99μg / L and 1.98μg / L), which can meet relevant requirements; this method has the characteristics of simple operation, high sensitivity and rapidity.

[0052] In a feasible embodiment, the MIL-101(Fe)-NH 2 The steps of determining the first linear relationship between the Cr(VI) concentration and the fluorescence intensity I include: mixing the Cr(VI) standard solutions with different concentrations and the ascorbic acid, and adding the ascorbic acid in MIL-101(Fe)-NH 2 Nanomaterials; dilute to 3 mL with pH 6.8 MES buffer solution, shake well, and let stand for 5-10 minutes; measure the fluorescence intensity at an excitation wavelength of 352 nm and an emission wavelength of 448 nm to determine the first linear relationship between the concentration of Cr (VI) and the fluorescence intensity I. This arrangement further improves the specific method of determining the first linear relationship, making the corresponding relationship between the concentration of Cr (VI) and the fluorescence intensity I more accurate, and thus making the first linear relationship have a wider linear range, which can reach 7.5-750 μg / L and 13.3-1000 μg / L, and can have a good detection limit, which can reach 0.99 μg / L and 1.98 μg / L.

[0053] In a feasible embodiment, the ascorbic acid concentration is 1 mg / mL, the volume is 15-20 μL, the concentration of the Cr(VI) standard solution used to obtain the first linear relationship is 7.5-750 μg / L, and the MIL-101(Fe)-NH 2 The material is MIL-101(Fe)-NH with a concentration of 2 mg / mL and an addition amount of 50-100 μL. 2 Nano material solution. Such an arrangement can make the determination of the first linear relationship more accurate.

[0054] In a feasible embodiment, the MIL-101(Fe)-NH 2 The step of determining the second linear relationship between the Cr(VI) concentration and the absorbance A comprises: mixing the Cr(VI) standard solutions with different concentrations with MIL-101(Fe)-NH 2 Nanomaterials, TMB and H 2 O 2Mix; dilute to 3 mL with pH 4.0 acetate buffer solution, shake well, and let stand for 5-10 minutes; measure the absorbance at a wavelength of 652 nm to determine the second linear relationship between the concentration of Cr(VI) and the absorbance A. This arrangement further improves the specific method of determining the second linear relationship, making the corresponding relationship between the concentration of Cr(VI) and the absorbance A more accurate, and thus making the second linear relationship have a wider linear range, which can reach 7.5-750μg / L and 13.3-1000μg / L, and can have a good detection limit, which can reach 0.99μg / L and 1.98μg / L.

[0055] In a feasible embodiment, the TMB concentration is 5 mmol / L, and the volume is 40-80 μL; 2 O 2 The concentration is 50mmol / L, the volume is 40-80μL, the concentration of the Cr(VI) standard solution used to obtain the second linear relationship is 1-100μg / L, the MIL-101(Fe)-NH 2 The material is MIL-101(Fe)-NH with a concentration of 2 mg / mL and an addition amount of 50-100 μL. 2 Nano material solution. Such an arrangement can make the determination of the second linear relationship more accurate.

[0056] In a feasible embodiment, in the MIL-101(Fe)-NH 2 materials, Cr(VI) standard solutions of different concentrations and ascorbic acid, and before the step of determining the first linear relationship between Cr(VI) concentration and fluorescence intensity I, the method further includes: based on 2-aminoterephthalic acid, FeCl 3 6H 2 Preparation of MIL-101(Fe)-NH 2 Material.

[0057] In this technical solution, MIL-101(Fe)-NH 2 The specific preparation method of the material is to use 2-aminoterephthalic acid, FeCl 3 6H 2 O and DMF as raw materials for MIL-101(Fe)-NH 2 The iron-based metal organic framework MIL-101(Fe)-NH 2 Nanoparticles can improve the MIL-101(Fe)-NH 2 The preparation efficiency and purity of nanoparticles can further ensure the reliability and accuracy of subsequent testing.

[0058] In a feasible embodiment, the 2-aminoterephthalic acid, FeCl 3 6H 2 Preparation of MIL-101(Fe)-NH 2 The material steps include:

[0059] 2.5-3.0 mmol of 2-aminoterephthalic acid, 5-6 mmol of FeCl 3 6H 2 O was added to 35-45 mL of DMF and sonicated for 15-20 min;

[0060] The solution was transferred into a polytetrafluoroethylene reaction tank and placed in a muffle furnace and heated at 110-120°C for 24 hours. After the reaction was completed, it was naturally cooled to room temperature.

[0061] Wash with anhydrous ethanol and DMF 3-4 times each, and dry in vacuum to obtain MIL-101(Fe)-NH 2 .

[0062] In this technical solution, a method for preparing MIL-101(Fe)-NH 2 The specific method of nanoparticle material is to make 2-aminoterephthalic acid, FeCl 3 6H 2 O and DMF are fully fused to increase the contact probability of the reactants. Further heating at 110-120°C for 24 hours can further promote the completion of the reaction. Afterwards, impurities can be removed by washing with anhydrous ethanol and DMF 3-4 times to ensure that MIL-101(Fe)-NH 2 Purity of nanoparticles.

[0063] Example 1: Determination of Cr(VI) in heated cigarette tobacco materials

[0064] 1. MIL-101(Fe)-NH 2 Preparation: 2.5 mmol of 2-aminoterephthalic acid, 5 mmol of FeCl 3 6H 2 O was added to 35 mL DMF and ultrasonically treated for 15 min. The solution was transferred to a polytetrafluoroethylene reaction tank and placed in a muffle furnace and heated at 110 °C for 24 h. After the reaction was completed, it was naturally cooled to room temperature, washed with anhydrous ethanol and DMF 3-4 times each, and dried in vacuum to obtain MIL-101(Fe)-NH 2 ; Prepared MIL-101(Fe)-NH 2 Transmission electron microscopy was performed and the results were as follows Figure 2 ,MIL-101(Fe)-NH 2It has a square biscuit shape with an average diameter of about 200nm; Figure 3 As shown in MIL-101(Fe)-NH 2 When AA is added to the MOF material, its shape collapses, which means that the NH 2 -BDC released.

[0065] 2. MIL-101(Fe)-NH 2 Fluorescence properties of 2 mg / mL MIL-101(Fe)-NH 2 There is weak emission under 352nm excitation, with the maximum emission wavelength at 430nm, while the same concentration of NH 2 -BDC has a certain red shift and strong fluorescence emission under 352nm excitation, with the maximum emission wavelength at 448nm; when 1mg / mL AA is added, MIL-101(Fe)-NH 2 The fluorescence of Figure 4 As shown, after adding 200μg / L Cr(VI), the fluorescence intensity of the system was inhibited and decreased.

[0066] 3. MIL-101(Fe)-NH 2 Peroxidase-like activity: Take 50 μL of 5 mmol / L TMB and add 2 mg / mL MIL-101(Fe)-NH 2 70μL, add 0.1mmol / L pH 4.0 acetate buffer solution to 3mL, shake well, let stand for 10min, and measure the absorbance at 652nm wavelength. Figure 5 The results showed that MIL-101(Fe)-NH 2 It has good simulated oxidase activity. When 200μg / L Cr(VI) is added, the absorbance of the system is greatly improved.

[0067] 4. Preparation of working curve for fluorescence detection of Cr(VI): Add 7.5-750 μg / LCr(VI) standard solution into a 5 mL stoppered colorimetric tube, add 20 μL of 1 mg / mL ascorbic acid, react for 10 min, then add 100 μL of 2 mg / mL MIL-101(Fe)-NH 2 , dilute to 3 mL with pH 6.8 MES buffer solution, shake well, let stand for 5-10 min, measure the fluorescence intensity at 352 nm excitation wavelength and 448 nm emission wavelength, draw a standard curve with Cr(VI) concentration as the horizontal axis and fluorescence intensity I as the vertical axis, and get the regression equation, see Figure 6a and Figure 6bThe regression equation, correlation coefficient, relative standard deviation, linear range, etc. are shown in Table 1. The TMB concentration was 5 mmol / L, the volume was 40-80 μL, and H 2 O 2 The concentration is 50mmol / L and the volume is 40-80μL

[0068] 5. Preparation of working curve for visible light detection of Cr(VI): Add 13.3-1000μg / LCr(VI) standard solution into a 5mL stoppered colorimetric tube, add 80μL 5mmol / L TMB, 80μL 50mmol / L H 2 O 2 , dilute to 3 mL with pH 4.0 acetate buffer solution, shake well, let stand for 10 min, measure absorbance at 652 nm, plot standard curve with Cr(VI) concentration as abscissa and absorbance A as ordinate, and get regression equation, see Figure 7a and Figure 7b ; The regression equation, correlation coefficient, relative standard deviation, linear range, etc. are shown in Table 1.

[0069] Table 1 Linear equation, correlation coefficient, relative standard deviation, linear range

[0070]

[0071] 6. Method specificity investigation: Cr(VI) was mixed with other coexisting ions to detect the effect of coexisting ions on Cr(VI) in the above detection system. The concentration of Cr(VI) was 25 μg / L and the concentration of the above interfering substances was 200 μg / L. Figure 8a and Figure 8b Is the coexisting ion (Na + , K + , Ca 2+ Mg 2+ , Cu 2+ 、Zn 2+ , Pb 2+ 、Cd 2+ , Fe 2+ Cr 3+ 、Ag + , CO 3 2- 、NO 3 - 、SO 4 2- , Cl - The results of the effects of Cr(VI) on Figure 8a and Figure 8b It can be seen that MIL-101(Fe)-NH 2The detection system has good selectivity. Only Cr(VI) has obvious fluorescence inhibition and absorbance enhancement effects, while other substances have almost no effects. The method has good selectivity for the determination of Cr(VI).

[0072] 7. Determination of Cr(VI) in tobacco materials for heated cigarettes

[0073] (1) Sample treatment: Take about 50 g of tobacco flakes from a heated cigarette cartridge and grind them into powder using a blender. Accurately weigh 3 portions of 0.25 g (accurate to 0.001 g) and place them in a microwave digestion tank. Add 5 mL of nitric acid and digest according to the microwave digestion program in Table 2. After cooling, take out the digestion tank and remove the acid at 150°C to about 1 mL. After the digestion tank is cooled, transfer the digestion solution to a 10 mL volumetric flask. Wash the digestion tank with a small amount of water for 2-3 times. Combine the washing solution in the volumetric flask and dilute to the mark with deionized water to obtain the Cr(VI) sample determination solution. Perform a blank test at the same time.

[0074] Table 2 Microwave digestion heating program

[0075]

[0076]

[0077] (2) Fluorescence determination of Cr(VI) in heated cigarette tobacco materials: 200 μL of the sample solution prepared in step (1) was added to a 5 mL stoppered colorimetric tube, followed by 20 μL of 1 mg / mL ascorbic acid. After reacting for 10 min, 100 μL of 2 mg / mL MIL-101(Fe)-NH 2 , dilute to 3 mL with pH 6.8 MES buffer solution, shake well, let stand for 5-10 min, measure the fluorescence intensity at 352 nm excitation wavelength and 448 nm emission wavelength, substitute into the regression equation, and calculate the Cr(VI) content to be 6.58 μg / kg.

[0078] (3) Photometric determination of Cr(VI) in heated cigarette tobacco materials: 200 μL of the sample solution prepared in step (1) was added to a 5 mL stoppered colorimetric tube, and 80 μL of 5 mmol / L TMB and 80 μL of 50 mmol / L H 2 O 2 , dilute to 3 mL with pH 4.0 acetate buffer solution, shake well, let stand for 10 min, measure the absorbance at a wavelength of 652 nm, substitute into the regression equation, and calculate the Cr(VI) content to be 6.51 μg / kg.

[0079] (4) Recovery and precision experiment: Three different concentrations of Cr(VI) standard solutions were added to the heated cigarette tobacco material samples; each concentration was measured three times in parallel, and the spiked recovery was calculated, and the relative standard deviation (RSD) was calculated. The results are shown in Table 3. The spiked recoveries of Cr(VI) measured by fluorescence and photometry were between 93.2% and 105.2%, and the RSD was between 2.45% and 4.12%. This method has good accuracy and precision.

[0080] Table 3 Sample spike recovery and RSD (n = 3)

[0081]

[0082] Example 2: Determination of Cr(VI) in Cigarette Samples

[0083] 1. MIL-101(Fe)-NH 2 Preparation: 3.0 mmol of 2-aminoterephthalic acid, 6 mmol of FeCl 3 6H 2 O was added to 45 mL DMF and ultrasonically treated for 15-20 min. The solution was transferred to a polytetrafluoroethylene reaction tank and placed in a muffle furnace and heated at 120 °C for 24 h. After the reaction was completed, it was naturally cooled to room temperature, washed with anhydrous ethanol and DMF 3-4 times each, and dried in vacuum to obtain MIL-101(Fe)-NH 2 .

[0084] 2. Preparation of working curve for fluorescence detection of Cr(VI): Same as Example 1.

[0085] 3. Preparation of working curve for visible light detection of Cr(VI): same as in Example 1.

[0086] 4. Determination of Cr(VI) in cigarette samples

[0087] (1) Sample treatment: Take a cigarette, peel off the tobacco filler, weigh 0.2000 g of tobacco sample, add 20 mL of 100 mmol / LEDTA solution (adjusted to pH 7.5 with ammonia water), extract in a 50°C water bath for 3 h, take 5 mL of the extract and pass it through a graphitized carbon black column to obtain a sample solution of cigarette tobacco.

[0088] (2) Determination of Cr(VI) in heated cigarette tobacco materials: Same as in Example 1, the fluorescence measurement result was 210

[0089] The Fe(III) and Cr(VI) determination method established by the present invention has the advantages of fewer processing steps, shorter time, lower processing cost, simple operation, and no need for large-scale instruments and equipment, and has great advantages in actual detection.

[0090] In the present invention, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance; the term "plurality" refers to two or more, unless otherwise clearly defined. The terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0091] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by terms such as “upper”, “lower”, “left”, “right”, “front” and “back” are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific orientation, and therefore, cannot be understood as a limitation on the present invention.

[0092] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0093] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A dual-mode rapid detection method for chromium, characterized in that: include: Based on MIL-101(Fe)-NH2 material, different concentrations of Cr(VI) standard solutions and ascorbic acid, the first linear relationship between Cr(VI) concentration and fluorescence intensity I was determined; Based on MIL-101(Fe)-NH2 material, Cr(VI) standard solutions of different concentrations and TMB, the second linear relationship between Cr(VI) concentration and absorbance A was determined; Cr(VI) in the detection sample is digested to obtain a sample test solution, and the concentration of Cr(VI) in the sample test solution is determined based on the first linear relationship and the second linear relationship.

2. The method for rapid dual-mode detection of chromium according to claim 1, characterized in that: The step of determining the first linear relationship between Cr(VI) concentration and fluorescence intensity I based on MIL-101(Fe)-NH2 material, Cr(VI) standard solutions of different concentrations and ascorbic acid comprises: The Cr(VI) standard solutions with different concentrations were mixed with ascorbic acid, and then added to the MIL-101(Fe)-NH2 nanomaterials after 5-10 minutes. Use pH 6.8 MES buffer solution to make up to 3 mL, shake well, and let stand for 5-10 minutes; The fluorescence intensity was measured at an excitation wavelength of 352 nm and an emission wavelength of 448 nm to determine the first linear relationship between the Cr(VI) concentration and the fluorescence intensity I.

3. The method for rapid dual-mode detection of chromium according to claim 1, characterized in that: The ascorbic acid concentration is 1 mg / mL, and the volume is 15-20 μL.

4. The method for rapid dual-mode detection of chromium according to claim 1, characterized in that: The step of determining the second linear relationship between Cr(VI) concentration and absorbance A based on MIL-101(Fe)-NH2 material, Cr(VI) standard solutions of different concentrations and TMB comprises: The Cr(VI) standard solutions with different concentrations were mixed with MIL-101(Fe)-NH2 nanomaterials, TMB and H2O2; Make up to 3 mL with pH 4.0 acetate buffer solution, shake well, and let stand for 5-10 min; The absorbance was measured at a wavelength of 652 nm to determine the second linear relationship between the Cr(VI) concentration and the absorbance A.

5. The method for rapid dual-mode detection of chromium according to claim 4, characterized in that: The TMB concentration is 5 mmol / L, and the volume is 40-80 μL; The H2O2 concentration is 50mmol / L and the volume is 40-80μL.

6. The dual-mode rapid detection method for chromium according to any one of claims 1 to 5, characterized in that: The concentration of the Cr(VI) standard solution used to obtain the first linear relationship is 7.5-750 μg / L.

7. The dual-mode rapid detection method for chromium according to any one of claims 1 to 5, characterized in that: The concentration of the Cr(VI) standard solution used to obtain the second linear relationship is 1-100 μg / L.

8. The dual-mode rapid detection method for chromium according to any one of claims 1 to 5, characterized in that: The MIL-101(Fe)-NH2 material is a MIL-101(Fe)-NH2 nano material solution with a concentration of 2 mg / mL and an addition amount of 50-100 μL.

9. The dual-mode rapid detection method for chromium according to any one of claims 1 to 5, characterized in that: Before the step of determining the first linear relationship between the Cr(VI) concentration and the fluorescence intensity I based on the MIL-101(Fe)-NH2 material, the Cr(VI) standard solutions of different concentrations and ascorbic acid, the method further includes: MIL-101(Fe)-NH2 material was prepared based on 2-aminoterephthalic acid, FeCl3·6H2O and DMF.

10. The dual-mode rapid detection method for chromium according to claim 9, characterized in that: The steps of preparing the MIL-101(Fe)-NH2 material based on 2-aminoterephthalic acid, FeCl3·6H2O and DMF include: Add 2.5-3.0 mmol of 2-aminoterephthalic acid and 5-6 mmol of FeCl3·6H2O to 35-45 mL of DMF and perform ultrasonic treatment for 15-20 min; The solution was transferred into a polytetrafluoroethylene reaction tank and placed in a muffle furnace and heated at 110-120°C for 24 hours. After the reaction was completed, it was naturally cooled to room temperature. The product was washed with anhydrous ethanol and DMF for 3-4 times respectively and dried in vacuo to obtain MIL-101(Fe)-NH2.

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