Dissolved-state fluorine element measuring method, functional paper-based chip and application

Abstract

The invention provides a dissolved fluorine element measuring method, a functional paper-based chip and application. The preparation method of the functionalized paper-based chip comprises the following steps: placing the paper base in a calcium chloride solution, oscillating to obtain the calcium chloride solution soaked with the paper base, then adding a NaOH solution, stirring and cleaning. The calcium hydroxide nano-particle functionalized paper-based chip provided by the invention is used for efficiently soaking and enriching fluorine elements in tea soup, and efficient enrichment of the fluorine elements is realized by utilizing physical and chemical adsorption of a calcium hydroxide nano-material on fluorine ions. Meanwhile, in the process of further detecting the fluorine element by adopting LIBS, when the paper-based chip adsorbed with fluorine ions is ablated by laser, the calcium hydroxide nanoparticles on the surface of the paper-based chip provide sufficient calcium particles for forming calcium fluoride molecule free radicals, and high-sensitivity measurement of the soluble fluorine element in the tea is realized by detecting a CaF molecule spectrum.

Description

Technical Field

[0001] The present invention relates to the field of detection technology, and in particular to a method for measuring dissolved fluorine element, a functionalized paper-based chip and applications. Background Art

[0002] Excessive fluorine content in tea poses a potential risk to human health. Fluorine is an indicator of tea safety, and excessive fluorine may lead to health problems such as dental fluorosis and skeletal fluorosis. Therefore, accurate detection of fluorine in tea to determine whether its content exceeds the standard is crucial to ensure the safety of tea drinking. At present, methods for measuring fluorine in tea, such as ion chromatography and atomic absorption spectrometry, usually require complex sample pretreatment and have high detection costs, making it difficult to achieve rapid detection of fluorine in tea.

[0003] Laser-induced breakdown spectroscopy (LIBS) technology is an efficient means of element detection and has significant advantages in the rapid measurement of elements. However, in the measurement of fluorine in tea, since the spectral lines of fluorine in visible light are difficult to excite and the low-energy spectral lines are in the ultraviolet band, LIBS technology faces certain difficulties in achieving high-precision measurement of fluorine. At present, there is an urgent need to develop a method for rapid in-situ detection of fluorine in tea. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for measuring dissolved fluorine element, a functionalized paper-based chip and applications.

[0005] In a first aspect, the present invention provides a method for preparing a functionalized paper-based chip, comprising: placing a paper base in a calcium chloride solution and shaking it to obtain a calcium chloride solution in which the paper base is soaked, and then adding a NaOH solution and stirring and washing it.

[0006] The present invention provides a calcium hydroxide nanoparticle functionalized paper-based chip for efficient enrichment of fluorine in tea soup, and utilizes the physical and chemical adsorption of fluorine ions by calcium hydroxide nanomaterials to achieve efficient enrichment of fluorine. At the same time, in the process of further using LIBS to detect fluorine, when laser ablation is performed on the paper-based chip adsorbed with fluorine ions, the calcium hydroxide nanoparticles on the surface of the paper-based chip provide sufficient calcium particles for forming calcium fluoride molecular free radicals, and by detecting the CaF molecular spectrum, highly sensitive measurement of soluble fluorine in tea leaves is achieved.

[0007] Preferably, the stirring time is 30 to 60 minutes. Stirring for 30 to 60 minutes allows the calcium hydroxide nanomaterial to be better modified on the paper base surface.

[0008] More preferably, the concentration of the NaOH solution is 0.8-1.2 M, preferably 1 M; and / or the NaOH solution is added dropwise until the pH of the calcium chloride solution is ≥10.

[0009] More preferably, deionized water is used for washing until the pH is neutral; and / or, a drying step is also included after the washing.

[0010] In a second aspect, the functionalized paper-based chip provided by the present invention is obtained by the above-mentioned preparation method, wherein the functionalized paper-based chip is a calcium hydroxide nanomaterial functionalized paper-based chip, in which the calcium hydroxide nanomaterial is modified on the surface of the paper base.

[0011] In a third aspect, the present invention provides a functionalized paper-based chip obtained by the above preparation method or an application of the above functionalized paper-based chip, wherein the functionalized paper-based chip is used for enriching fluorine and providing Ca particles to generate CaF free radicals, preferably for measuring dissolved fluorine in tea. The paper-based chip provided by the present invention is not only used for enriching fluorine, but also can provide Ca particles to generate CaF free radicals, which is crucial for the detection of F in tea.

[0012] In a fourth aspect, the present invention provides a method for measuring dissolved fluorine element, including:

[0013] 1) The functionalized paper-based chip is placed in a test solution and subjected to an oscillation treatment to obtain a paper-based chip adsorbed with fluoride ions.

[0014] 2) Drying the paper-based chip adsorbed with fluoride ions, and then measuring with LIBS.

[0015] 3) Obtaining the measurement result and deriving the concentration of dissolved fluorine element in the test liquid according to the calibration model.

[0016] Wherein, the functionalized paper-based chip is the functionalized paper-based chip obtained by the above preparation method or the above functionalized paper-based chip, and the liquid to be tested is preferably tea.

[0017] In the present invention, a calcium hydroxide nanoparticle functionalized paper-based chip is used for highly sensitive measurement of soluble fluorine in tea leaves. The calcium hydroxide nanoparticles can efficiently capture the fluorine element. Based on the LIBS technology, the calcium hydroxide nanoparticles are used to provide calcium particles that combine with the fluorine element adsorbed on the chip surface to form CaF free radicals. The CaF molecular spectrum is detected, thereby achieving highly sensitive detection of soluble fluorine in tea leaves.

[0018] Preferably, in step 1), the oscillation treatment includes oscillating on an oscillator for 5 to 30 minutes, preferably 15 to 20 minutes. By oscillating on the oscillator for a certain period of time, the fluorine element in the tea soup can fully contact with the calcium hydroxide nanoparticles on the surface of the paper-based chip, so that the fluorine ions can be efficiently fixed on the surface of the paper-based chip.

[0019] Preferably, in step 2), the measurement includes using LIBS to obtain the CaF molecular radical spectrum signal of the dried paper-based chip to obtain the fluorescence intensity in the 528-544 nm signal band; preferably, the signal band is 533 nm. By taking the 528-544 nm band range of the CaF molecular spectrum, especially the more obvious characteristic peak 533.0 nm, and establishing a calibration model with the fluorine element concentration, the analysis of dissolved fluorine in unknown samples can be better performed.

[0020] Preferably, in step 3), obtaining the calibration model comprises: placing the functionalized paper-based chip in tea water of different concentrations for oscillation treatment to obtain a paper-based chip adsorbed with fluoride ions; drying the paper-based chip adsorbed with fluoride ions, and then measuring with LIBS, and establishing a calibration model based on the fluorescence intensity measurement results in the 528-544 nm signal band and the fluorine element concentration of the tea water.

[0021] The beneficial effects of the present invention are at least that: the present invention adopts the calcium hydroxide nanomaterial functionalized paper-based chip to achieve efficient enrichment of soluble fluorine in tea soup, and the calcium element is environmentally friendly and pollution-free; moreover, in the measurement of fluorine element by detecting the CaF molecular spectrum using the LIBS technology, the calcium hydroxide nanomaterial functionalized paper-based chip can provide Ca particles for combining with F particles to generate CaF free radicals, and finally achieve high-sensitivity measurement of soluble F in tea leaves. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 This is a schematic diagram of the calcium hydroxide nanomaterial functionalized paper-based chip adsorbing fluorine in tea leaves in an embodiment of the present invention.

[0024] Figure 2 This is a spectrum diagram of CaF molecules measured by LIBS in an embodiment of the present invention.

[0025] Figure 3This is a SEM characterization image of the calcium hydroxide nanomaterial functionalized paper-based chip in an embodiment of the present invention.

[0026] Figure 4 This is a SEM characterization image of the paper-based chip functionalized with calcium hydroxide nanomaterials adsorbed with fluorine in an embodiment of the present invention.

[0027] Figure 5 This is a spectrum intensity diagram of CaF molecules measured by LIBS at different fluorine element concentrations in an embodiment of the present invention.

[0028] Figure 6 LIBS calibration curve diagram of different fluorine element concentrations in the embodiment of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods. If no specific techniques or conditions are specified in the examples, they are all conventional methods or the techniques or conditions described in the literature in this field, or according to the product instructions. If the manufacturers of the reagents and instruments are not specified, they are all conventional products that can be purchased through regular channels.

[0031] Figure 1 The present invention provides a method for measuring fluorine in tea leaves. Figure 1 The details are as follows: placing a paper base in a calcium chloride solution and shaking it for several minutes so that the surface of the paper base is completely soaked in the calcium chloride solution; then adding a sodium hydroxide solution dropwise into the calcium chloride solution until the pH of the solution is greater than 10, and then continuing to shake for several minutes to generate calcium hydroxide nanoparticles on the surface of the paper base; then taking out the paper base and washing it with deionized water several times to remove excess calcium hydroxide and calcium chloride on the surface of the paper base; the above steps obtain a paper base with a surface modified with calcium hydroxide.

[0032] The paper substrate modified with calcium hydroxide was placed in a beaker containing the test solution and shaken for several minutes to allow it to react fully. After that, the paper substrate adsorbed with CaF molecules was taken out and placed under the LIBS instrument for measurement. Finally, the following was obtained: Figure 2 The spectrum shown is for fluorine analysis.

[0033] In the present invention, the main chemical reagents such as calcium chloride (CaCl 2), sodium hydroxide, paper base, deionized water, etc. are all easily available in the art. The paper base used is absorbent paper purchased from Taizhou Aoke Filter Paper Factory.

[0034] Example 1

[0035] This embodiment provides a paper-based chip and a method for measuring fluorine in an aqueous solution, and the specific steps are as follows.

[0036] 1) Preparation of calcium hydroxide nanomaterial functionalized paper-based chips.

[0037] A calcium chloride solution with a concentration of 20 mM and a sodium hydroxide solution with a concentration of 1 M are prepared; 20 mL of the calcium chloride solution is taken and a paper-based film cut to a size of 10 mm x 10 mm is placed in the calcium chloride solution, and the paper-based film is placed on an oscillator for 10 minutes of oscillation; the prepared sodium hydroxide solution is then added dropwise to the calcium chloride solution containing the paper-based film, so that calcium hydroxide nanoparticles are gradually generated on the surface of the paper-based film, and the addition is stopped after the pH of the solution is greater than 10; the oscillation on the oscillator is continued for 60 minutes, so that calcium hydroxide nanoparticles are fully generated on the surface of the paper-based chip; the paper-based chip is taken out and the paper-based surface is rinsed with deionized water to remove the calcium hydroxide and calcium chloride not attached to the paper-based surface, and the pH of the final cleaning waste liquid is 7, and finally a calcium hydroxide nanomaterial functionalized paper-based chip is obtained. Figure 3 This is the SEM characterization picture of the calcium hydroxide nanomaterial functionalized paper-based chip. Figure 4 This is the SEM characterization image of the paper-based chip functionalized with calcium hydroxide nanomaterials adsorbed with fluorine.

[0038] 2) Enrichment, reaction and measurement of fluorine in aqueous solution.

[0039] First, the solution pH and adsorption oscillation time were optimized, and the optimal solution pH was selected as 7 and the optimal adsorption time was selected as 20 minutes.

[0040] The prepared paper-based chip was placed in a solution containing fluorine and oscillated on an oscillator for 20 minutes to allow the fluorine in the aqueous solution to be effectively enriched on the surface of the paper-based chip. The paper-based chip was then taken out and placed on a heating plate to remove excess water from the surface of the paper-based chip. The LIBS instrument was then used to measure and observe the CaF molecular spectrum band 528~544 nm signal.

[0041] The present embodiment also provides a method for obtaining the above-mentioned calibration model, including: placing the prepared calcium hydroxide nanomaterial functionalized paper-based chips in solutions with different fluorine concentrations, and placing them on an oscillator for 20 minutes to allow the fluorine element in the solution to fully contact the calcium hydroxide nanoparticles on the surface of the paper-based chip, so that the fluorine ions can be efficiently fixed on the surface of the paper-based chip; taking out the paper-based chip adsorbed with fluorine ions and drying it to remove excess surface moisture, and then using LIBS to measure and observe the CaF molecular free radical spectrum signal, the signal band of which is 528-544 nm; taking the relatively obvious characteristic peak 533.0 nm in the 528-544 nm band of the CaF molecular spectrum and the F element concentration to establish a calibration model. The spectrum diagram and calibration curve of the calcium hydroxide nanoparticle functionalized paper-based chip adsorbed with fluorine element for LIBS measurement are shown in the figure below: Figure 5 and Figure 6 As shown, the calibration model provided in this embodiment is y=0.75x-0.25; wherein y is the fluorescence intensity in the 528-544 nm signal band; and x is the concentration of dissolved fluorine element (mg / L).

[0042] This embodiment provides tests on the blank paper-based chip (untreated paper-based chip), the sodium hydroxide functionalized paper-based chip (paper-based chip soaked in sodium hydroxide), and the calcium hydroxide nanoparticle functionalized paper-based chip, and the test results show.

[0043] 1) The measurement effects of blank paper-based chip, sodium hydroxide functionalized paper-based chip and calcium hydroxide nanoparticle functionalized paper-based chip on fluorine element are as follows: Figure 2 It can be seen that the blank paper-based chip and the sodium hydroxide functionalized paper-based chip have no obvious CaF spectral signal, while the calcium hydroxide nanoparticle functionalized paper-based chip can obtain obvious CaF molecular spectral signal.

[0044] 2) Spectrum and calibration curve of LIBS measurement using a paper-based chip functionalized with calcium hydroxide nanoparticles adsorbed with fluorine ( Figure 5 and Figure 6 ) It can be seen that with the increase of fluorine concentration, the spectral intensity of CaF molecules is significantly enhanced, indicating that this method can be well used for the detection of excessive fluorine in solution.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a functionalized paper-based chip, characterized in that: include: The paper base is placed in a calcium chloride solution and shaken to obtain a calcium chloride solution in which the paper base is soaked, and then a NaOH solution is added and stirred for washing.

2. The method for preparing the functionalized paper-based chip according to claim 1, characterized in that: The stirring time is 30 to 60 minutes.

3. The method for preparing the functionalized paper-based chip according to claim 1 or 2, characterized in that: The concentration of the NaOH solution is 0.8-1.2 M; and / or, the NaOH solution is added dropwise until the pH of the calcium chloride solution is ≥10.

4. The method for preparing the functionalized paper-based chip according to any one of claims 1 to 3, characterized in that: The cleaning is performed with deionized water until the pH value is neutral; and / or, the cleaning further includes a drying step.

5. A functionalized paper-based chip, characterized in that: Obtained by the preparation method according to any one of claims 1 to 4, the functionalized paper-based chip is a calcium hydroxide nanomaterial functionalized paper-based chip, in which the calcium hydroxide nanomaterial is modified on the surface of the paper base.

6. Use of the functionalized paper-based chip obtained by the preparation method according to any one of claims 1 to 4 or the functionalized paper-based chip according to claim 5, characterized in that: The functionalized paper-based chip is used for enriching fluorine and providing Ca particles to generate CaF free radicals, and is preferably used in measuring dissolved fluorine in tea.

7. A method for measuring dissolved fluorine, characterized in that: include: 1) placing the functionalized paper-based chip in a test solution and performing an oscillation treatment to obtain a paper-based chip adsorbed with fluoride ions; 2) drying the paper-based chip adsorbed with fluoride ions, and then measuring using LIBS; 3) obtaining the measurement result and deriving the concentration of dissolved fluorine element in the test liquid according to the calibration model; Wherein, the functionalized paper-based chip is a functionalized paper-based chip obtained by the preparation method according to any one of claims 1 to 4 or a functionalized paper-based chip according to claim 5, and the liquid to be tested is preferably tea.

8. The method for measuring dissolved fluorine according to claim 7, characterized in that: In step 1), the shaking treatment includes shaking on an oscillator for 5 to 30 minutes.

9. The method for measuring dissolved fluorine according to claim 7 or 8, characterized in that: In step 2), the measurement includes using LIBS to obtain the CaF molecular radical spectrum signal of the dried paper-based chip to obtain the fluorescence intensity in the signal band of 528-544 nm; preferably, the signal band is 533 nm.

10. The method for measuring dissolved fluorine according to any one of claims 7 to 9, characterized in that: In step 3), obtaining the calibration model includes: placing the functionalized paper-based chip in tea water of different concentrations for oscillation treatment to obtain a paper-based chip adsorbed with fluoride ions; drying the paper-based chip adsorbed with fluoride ions, and then measuring it using LIBS, and establishing a calibration model based on the fluorescence intensity measurement results in the 528-544 nm signal band and the fluorine element concentration of the tea water.

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