Hydroxyapatite-chitosan modified polyether sulfone membrane, its preparation method and application in detection of heavy metal ions in membrane solid phase extraction-laser induced breakdown spectroscopy combination

Abstract

The present application belongs to the technical field of analytical chemistry, environmental monitoring and water quality online detection, and particularly relates to a hydroxyapatite-chitosan modified polyether sulfone membrane, a preparation method thereof and application of the membrane in detection of heavy metal ions in combination of membrane solid phase extraction and laser-induced breakdown spectroscopy. The present application mixes chitosan, hydroxyapatite and an aqueous glacial acetic acid solution to obtain a functional solution; the functional solution is coated on the surface of a polyether sulfone microporous filter membrane, and then solidified by alkali neutralization to obtain a hydroxyapatite-chitosan modified polyether sulfone membrane. The hydroxyapatite-chitosan modified polyether sulfone membrane provided by the present application can be well adapted to LIBS, can realize effective enrichment of trace heavy metals in a liquid sample to the membrane surface, can construct a high-stability solid target, and can realize rapid, high-sensitivity and high-anti-interference detection of heavy metal ions in the liquid sample.

Description

Technical Field

[0001] This invention belongs to the fields of analytical chemistry, environmental monitoring and online water quality detection technology, specifically involving hydroxyapatite-chitosan modified polyethersulfone membranes and their preparation methods, as well as their application in the detection of heavy metal ions using membrane solid-phase extraction-laser induced breakdown spectroscopy. Background Technology

[0002] Copper is a common heavy metal pollutant, widely found in industrial wastewater from electroplating, printed circuit boards, metallurgy, and mining tailings. Excessive copper ions can harm aquatic ecosystems and human health. Current methods for detecting copper in water mainly rely on laboratory instruments such as atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), or intramolecular plasma mass spectrometry (ICP-MS). These methods have the following drawbacks: complex pretreatment: often requiring acid digestion, extraction, and enrichment, resulting in long operation times; large and expensive instruments: unsuitable for on-site online or mobile monitoring; difficulty in achieving rapid batch detection: unable to adequately meet the needs of environmental emergency monitoring and process control.

[0003] Laser-induced breakdown spectroscopy (LIBS) offers advantages such as no need for complex pretreatment, fast analysis speed, simultaneous multi-element detection, and portable instrumentation, making it a potential technical route for online monitoring of heavy metals. However, direct LIBS detection of water samples has significant drawbacks: the laser's interaction with the liquid surface generates droplet splashing and bubbles, resulting in highly unstable plasma and poor signal reproducibility; strong liquid-phase matrix effects lead to a high background continuum and a relatively high detection limit; and in trace (ppb) level copper ion analysis, direct LIBS detection of liquid samples is insufficient to meet sensitivity requirements.

[0004] Membrane solid-phase extraction (MSPE) selectively adsorbs, enriches, and transforms target components into solid targets by constructing a functional layer on the membrane surface, providing an effective solution to the problems of liquid splashing and bubbles. Current MSPE techniques are mostly used in conjunction with AAS / ICP, but their application in LIBS (Liquid Iron-Based Stereolithography) results in poor enrichment rates and matrix adaptability for copper ions. Summary of the Invention

[0005] The purpose of this invention is to provide a hydroxyapatite-chitosan modified polyethersulfone membrane, its preparation method, and its application in the detection of heavy metal ions using membrane solid-phase extraction-laser induced breakdown spectroscopy. The hydroxyapatite-chitosan modified polyethersulfone membrane provided by this invention is well adapted to LIBS, enabling the effective enrichment of trace heavy metals in liquid samples onto the membrane surface, constructing a highly stable solid target, and achieving rapid, highly sensitive, and highly interference-resistant detection of heavy metal ions in liquid samples.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a hydroxyapatite-chitosan modified polyethersulfone membrane, comprising the following steps: Chitosan, hydroxyapatite (n-HAP), and an aqueous solution of glacial acetic acid were mixed to obtain a functionalized solution. The functionalized solution was coated onto the surface of a polyethersulfone (PES) microporous filter membrane, and then neutralized and cured with alkali to obtain a hydroxyapatite-chitosan modified polyethersulfone membrane.

[0007] Preferably, the average particle size of the hydroxyapatite is 20-100 nm; the volume fraction of glacial acetic acid in the aqueous acetic acid solution is 1.5-3%; the mass ratio of the hydroxyapatite to the chitosan is (0.5-2):1; and the pH value of the functionalized solution is 3.5-5.5.

[0008] Preferably, the pore size of the polyethersulfone microporous filter membrane is 0.22~0.45μm, and the diameter of the polyethersulfone microporous filter membrane is 13~25mm.

[0009] Preferably, the coating method includes spin coating or vacuum filtration; the volume ratio of the functionalized solution to the diameter of the polyethersulfone microporous filter membrane is (200~400) μL : (13~25) mm; when the coating method is spin coating, the spin coating speed is 200~500 rpm and the time is 20~40 s; the alkali neutralization and curing is performed using sodium hydroxide solution, the molar concentration of NaOH in the sodium hydroxide solution is 1~3 mol / L, and the alkali neutralization and curing time is 5~10 min; after alkali neutralization and curing, the process further includes sequential water washing and drying, and the drying temperature is 45~60℃.

[0010] The present invention provides a hydroxyapatite-chitosan modified polyethersulfone membrane prepared by the preparation method described above.

[0011] This invention provides the application of the hydroxyapatite-chitosan modified polyethersulfone membrane described above in the detection of heavy metal ions using membrane solid-phase extraction-laser induced breakdown spectroscopy.

[0012] This invention provides a method for detecting heavy metal ions in liquids using membrane solid-phase extraction coupled with laser-induced breakdown spectroscopy, comprising the following steps: A liquid sample containing heavy metal ions is mixed with an alkali metal diethyldithiocarbamate to undergo a complexation reaction, resulting in a suspension system containing a particulate complex of the heavy metal diethyldithiocarbamate. The suspension system is filtered through the hydroxyapatite-chitosan modified polyethersulfone membrane described in the above technical solution. The hydroxyapatite-chitosan modified polyethersulfone membrane captures the diethyldithiocarbamate particulate complex of the heavy metal, thereby obtaining a heavy metal enriched solid target. The heavy metal-enriched solid target was detected by laser-induced breakdown spectroscopy to obtain the static intensity of the characteristic spectral lines of heavy metal elements in the liquid sample to be tested. The concentration of heavy metal ions in the liquid sample is obtained from the static intensity of the characteristic spectral lines of heavy metal elements in the liquid sample to be tested.

[0013] Preferably, the alkali metal diethyldithiocarbamate is sodium diethyldithiocarbamate; the heavy metal ions include one or more of copper ions, iron ions, lead ions, cadmium ions, nickel ions, zinc ions and chromium ions; the molar ratio of the alkali metal diethyldithiocarbamate to the heavy metal ions in the liquid sample to be tested is ≥3:1.

[0014] Preferably, the pH value of the complexation reaction is 6.5-9; the time of the complexation reaction is 5-15 min; and the complexation reaction is followed by a settling treatment of the obtained complexation reaction solution for 2-5 min.

[0015] Preferably, the detection conditions include: a laser wavelength of 1064 nm, a single pulse energy of 50-80 mJ, a repetition frequency of 5-10 Hz, a delay time of 0.8-1.5 μs, an integration time of 1.0-3.0 μs, and when the heavy metal ion is copper ion, the detection spectral line is Cu(I) 324.75 nm or Cu(I) 327.40 nm.

[0016] This invention provides a method for preparing a hydroxyapatite-chitosan modified polyethersulfone (PES) membrane, comprising the following steps: mixing chitosan, hydroxyapatite (n-HAP), and an aqueous solution of glacial acetic acid to obtain a functionalized solution; coating the functionalized solution onto the surface of a polyethersulfone (PES) microporous filter membrane, and then neutralizing and curing it with alkali to obtain the hydroxyapatite-chitosan modified PES membrane. This invention uses a PES microporous filter membrane as the base membrane and employs hydroxyapatite and chitosan to synergistically modify the PES microporous filter membrane. The resulting hydroxyapatite-chitosan modified PES membrane significantly improves the capture capacity of heavy metal diethyldithiocarbamates (e.g., Cu(DDTC)₂). This invention uses hydroxyapatite and chitosan for modification; hydroxyapatite provides a large specific surface area and Ca²⁺ content. 2+ / PO4 3-Chitosan provides -NH2 / -OH functional groups, which together construct a multi-site, multi-mechanism adsorption interface on the surface of the PES microporous filter membrane. While heavy metal diethyldithiocarbamate (e.g., Cu(DDTC)2) particles are physically retained, the enrichment efficiency and signal stability are also improved through hydrogen bonding, hydrophobic interactions, and weak coordination between heavy metal ions and sulfur / nitrogen atoms (e.g., Cu-S / N atoms).

[0017] Furthermore, this invention optimizes the mass ratio of n-HAP to chitosan (0.5~2):1, achieving the best intensity and reproducibility of heavy metal ion (Cu ion) spectral lines.

[0018] This invention provides a method for detecting heavy metal ions in liquids using membrane solid-phase extraction coupled with laser-induced breakdown spectroscopy, comprising the following steps: mixing a test liquid sample containing heavy metal ions with an alkali metal diethyldithiocarbamate to undergo a complexation reaction to obtain a suspension system, wherein the suspension system contains particulate complexes of heavy metal diethyldithiocarbamate (e.g., Cu(DDTC)2); filtering the suspension system through a hydroxyapatite-chitosan modified polyethersulfone membrane as described above, wherein the hydroxyapatite-chitosan modified polyethersulfone membrane captures the particulate complexes of heavy metal diethyldithiocarbamate (e.g., Cu(DDTC)2) to obtain a heavy metal-enriched solid target; detecting the heavy metal-enriched solid target using laser-induced breakdown spectroscopy to obtain the static intensity of the characteristic spectral lines of heavy metal elements in the test liquid sample; and obtaining the concentration of heavy metal ions in the test liquid sample from the static intensity of the characteristic spectral lines of heavy metal elements in the test liquid sample. The detection method provided by this invention transforms liquid samples into solid targets. When the heavy metal ion is copper, the detection limit can reach 1.5 ppb. Through DDTC complexation precipitation and membrane solid-phase enrichment, this invention transforms water samples, which are originally difficult to detect directly by LIBS, into highly stable solid targets. In the range of 5~200 ppb, the net intensity of the Cu spectral line shows good linearity with the copper concentration, and the detection limit (LOD) can reach 1.5 ppb, which is significantly better than direct LIBS detection of water samples (LOD is usually >100 ppm, see Comparative Example 1), and the sensitivity is improved by several orders of magnitude. Compared with the prior art, the detection method provided by this invention has the following advantages: This invention provides a method for detecting heavy metal ions in liquids using membrane solid-phase extraction coupled with laser-induced breakdown spectroscopy (LIBS). This method is applicable to the detection of various heavy metal ions, including one or more of copper, iron, lead, cadmium, nickel, zinc, and chromium ions. When using LIBS detection, different types of heavy metals correspond to different wavelengths of characteristic spectral lines. The wavelength of these characteristic spectral lines is determined by the energy levels of electrons in the metal atoms. Different energy levels correspond to different LIBS spectra, resulting in different spectral wavelengths for different metals (including different valence states), thus enabling the simultaneous detection of multiple metals. This invention utilizes DDTC complexation and membrane material enrichment to transfer metal ions from the liquid sample to the membrane material surface for solid-state sample detection. This is equivalent to concentrating the liquid sample to a dry state for detection, significantly improving sensitivity. Compared to directly detecting the liquid sample using LIBS, when the laser strikes the liquid sample, phenomena such as splashing and atomization occur on the liquid surface. This leads to a decrease in the spectral intensity of metal ions, resulting in reduced detection sensitivity, or even the inability to detect metal ion signals in water. The method provided by this invention effectively overcomes the aforementioned shortcomings of LIBS direct detection of liquid samples.

[0019] The method provided by this invention has high anti-interference capability: experiments show that it can effectively resist common coexisting ions (Na+). + K + Ca 2+ Mg 2+ Zn 2+ Pb 2+ Fe 3+ In the presence of (etc.) and representative organic compounds (humic acid, surfactants, such as the anionic surfactant sodium dodecyl sulfate (SDS)), the method provided by this invention maintains a spiked recovery of 50 ppb Cu of 96-104%, with RSD generally below 8% (see results for anti-interference). Figure 4 This demonstrates that the method provided by the present invention has good anti-interference performance for complex water samples.

[0020] The method provided by this invention is simple to operate and suitable for rapid on-site monitoring: the pretreatment is only "add DDTC-Na → reaction → filtration", and the entire process and LIBS determination can be completed within minutes, avoiding cumbersome steps such as sample digestion, extraction, rinsing, and injection. It is suitable for use with portable or online LIBS instruments for rapid monitoring of copper in industrial wastewater, surface water and drinking water. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the copper ion detection method in water according to the present invention; Figure 2Cu in this invention 2+ Fitting curve of net spectral intensity versus concentration in water sample; Figure 3 Comparison of LIBS signal intensity for 50 ppb Cu using different membrane materials; Figure 4 For common coexisting ions and organic compounds, Cu 2+ Results of signal interference experiments; Figure 5 This is a SEM image of the polyethersulfone film material. Figure 5 (a) and (b) in the figure are polyethersulfone-based films. Figure 5 (c) and (d) in the image are SEM images after modification; Figure 6 For the present invention, for Zn-containing 2+ Cr 3+ Ni 2+ Enrichment and Libs test results of mixed heavy metal water samples; Figure 7 These are photographs of the membrane materials after processing a series of water samples containing copper ions of different concentrations in this invention. Figure 8 The membrane material provided in Example 1 for Zn 2+ Ni 2+ Cr 3+ Fitting curves of net spectral intensity versus concentration in water sample. Detailed Implementation

[0022] This invention provides a method for preparing a hydroxyapatite-chitosan modified polyethersulfone membrane, comprising the following steps: Chitosan, hydroxyapatite (n-HAP, or HAP for short) and glacial acetic acid aqueous solution were mixed to obtain a functionalized solution; The functionalized solution was coated onto the surface of a polyethersulfone (PES) microporous filter membrane, and then neutralized and cured with alkali to obtain a hydroxyapatite-chitosan modified polyethersulfone membrane.

[0023] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0024] This invention mixes chitosan, hydroxyapatite, and an aqueous solution of glacial acetic acid to obtain a functionalized solution. In this invention, the mixing preferably includes the following steps: dissolving the chitosan in an aqueous solution of glacial acetic acid to obtain a chitosan solution; and ultrasonically dispersing the chitosan solution and the hydroxyapatite to obtain the functionalized solution. The volume fraction of glacial acetic acid in the aqueous solution is preferably 1.5-3%, more preferably 2-2.5%. The mass concentration of chitosan in the chitosan solution is preferably 1-4% (w / v), more preferably 2-3% (w / v). The average particle size of the hydroxyapatite is preferably 20-100 nm, more preferably 50-70 nm. The mass ratio of the hydroxyapatite to the chitosan is preferably (0.5-2):1, more preferably (1-1.5):1. This invention does not have specific requirements for the specific implementation of the ultrasonic dispersion. The functionalized solution is a HAP-chitosan functionalized solution. The pH value of the functionalized solution is preferably 3.5 to 5.5, and in the examples it can be 4.5 ± 0.5.

[0025] After obtaining the functionalized solution, the present invention coats the functionalized solution onto the surface of a polyethersulfone microporous filter membrane, and then cures it with alkali to obtain a hydroxyapatite-chitosan modified polyethersulfone membrane. In the present invention, the pore size of the polyethersulfone microporous filter membrane is preferably 0.22~0.45 μm. The diameter of the polyethersulfone microporous filter membrane is preferably 13~25 mm. The volume ratio of the functionalized solution to the diameter of the polyethersulfone microporous filter membrane is preferably (200~400) μL : (13~25) mm. The coating method preferably includes spin coating or vacuum filtration. When the coating method is preferably spin coating, the spin coating speed is preferably 200~500 rpm, more preferably 250~400 rpm. The spin coating time is preferably 20~40 s, more preferably 25~30 s. The alkali neutralization and curing are preferably performed using a sodium hydroxide solution. The alkali neutralization and curing are preferably performed by immersing the coated wet membrane in a sodium hydroxide solution. The molar concentration of NaOH in the sodium hydroxide solution is preferably 1-3 mol / L, more preferably 1.5-2.5 mol / L. The impregnation temperature can be room temperature, and the impregnation time is preferably 5-10 min. The alkali neutralization and curing time is preferably 5-10 min. After alkali neutralization and curing, the present invention preferably further includes washing and drying the alkali-neutralized and cured product sequentially with water. The water washing uses deionized water. The drying temperature is preferably 45-60℃.

[0026] This invention provides a hydroxyapatite-chitosan modified polyethersulfone membrane prepared by the preparation method described above. In this invention, the hydroxyapatite-chitosan modified polyethersulfone membrane comprises a base membrane and a hydroxyapatite-chitosan composite layer disposed on the surface of the base membrane. The base membrane is a polyethersulfone (PES) microporous filter membrane. The hydroxyapatite-chitosan composite layer comprises hydroxyapatite and chitosan.

[0027] This invention provides the application of the hydroxyapatite-chitosan modified polyethersulfone membrane described above in the detection of heavy metal ions using membrane solid-phase extraction-laser-induced breakdown spectroscopy. In this invention, the heavy metal ions preferably include copper ions (Cu). 2+ ), iron ions (Fe 3+ and / or Fe 2+ ), lead ions (Pb) 2+ ), cadmium ions (Cd) 2+ Nickel ions (Ni) 2+ ), zinc ions (Zn 2+ ) and chromium ions (Cr 2+ Cr 3+ and Cr 6+ One or more of the following (in the examples, copper ions, zinc ions, nickel ions, or Cr ions).

[0028] The hydroxyapatite-chitosan modified polyethersulfone membrane provided by this invention significantly improves the membrane's adsorption and capture capacity for heavy metal diethyldithiocarbamates (i.e., DDTC-heavy metal complexes, such as Cu(DDTC)2). This invention also provides a method for detecting heavy metal ions in liquids using membrane solid-phase extraction-laser-induced breakdown spectroscopy (LIBS), which converts heavy metal ions in the liquid sample into a solid target on the membrane surface, overcoming the splashing and matrix effect problems of liquid LIBS. Furthermore, this invention enables ppb-level detection of copper ions in liquid samples, with a detection limit of up to 1.5 μg / L, and exhibits excellent resistance to interference from coexisting ions and organic matter.

[0029] This invention provides a method for detecting heavy metal ions in liquids using membrane solid-phase extraction coupled with laser-induced breakdown spectroscopy, comprising the following steps: The test liquid sample containing heavy metal ions is mixed with alkali metal diethyl dithiocarbamate to undergo a complexation reaction to obtain a suspension system. The suspension system contains particulate complexes of heavy metal diethyl dithiocarbamate (i.e., DDTC-heavy metal complex, such as Cu(DDTC)2). The suspension system is filtered through the hydroxyapatite-chitosan modified polyethersulfone membrane described in the above technical solution. The hydroxyapatite-chitosan modified polyethersulfone membrane captures the diethyldithiocarbamate particulate complex of the metal to obtain a heavy metal enriched solid target. The heavy metal-enriched solid target was detected by laser-induced breakdown spectroscopy to obtain the static intensity of the characteristic spectral lines of heavy metal elements in the liquid sample to be tested. The concentration of heavy metal ions in the liquid sample is obtained from the static intensity of the characteristic spectral lines of heavy metal elements in the liquid sample to be tested.

[0030] This invention involves mixing a test liquid sample containing heavy metal ions with an alkali metal diethyldithiocarbamate to undergo a complexation reaction, resulting in a suspension system containing a metal-containing diethyldithiocarbamate particulate complex. In this invention, the test liquid sample containing heavy metal ions can be an aqueous solution containing heavy metal ions. The heavy metal ions preferably include copper ions (Cu). 2+ ), iron ions (Fe 3+ and / or Fe 2+ ), lead ions (Pb) 2 + ), cadmium ions (Cd) 2+ Nickel ions (Ni) 2+ ), zinc ions (Zn 2+ ) and chromium ions (Cr 2+ Cr 3+ and Cr 6+ One or more of the following (including one or more of the following). The alkali metal diethyldithiocarbamate can be sodium diethyldithiocarbamate (DDTC-Na). In the embodiments of the present invention, the alkali metal diethyldithiocarbamate can be used in the form of an aqueous solution of alkali metal diethyldithiocarbamate, and the molar concentration of alkali metal diethyldithiocarbamate in the aqueous solution of alkali metal diethyldithiocarbamate is preferably 0.01~0.05 mol / L. The molar ratio of the alkali metal diethyldithiocarbamate to the heavy metal ions in the liquid sample to be tested is preferably ≥3:1, more preferably (5~10):1. The present invention ensures that the alkali metal diethyldithiocarbamate is in excess, thereby enabling complete complexation of heavy metal ions in the liquid sample to be tested.

[0031] In this invention, the pH value of the complexation reaction is preferably 6.5-9, more preferably 7-8.5. This invention preferably controls the pH value of the complexation reaction within the range of 6.5-9 to avoid affecting the subsequent performance of the hydroxyapatite-chitosan modified polyethersulfone membrane. The temperature of the complexation reaction is room temperature, i.e., no heating or cooling treatment is required. The time of the complexation reaction is preferably 5-15 minutes. After the complexation reaction, the obtained complexation reaction solution is allowed to stand to obtain a suspension system. The standing time is preferably 2-5 minutes. This invention, through the standing treatment, can obtain a stable suspension system.

[0032] After obtaining the suspension system, the present invention filters the suspension system through the hydroxyapatite-chitosan modified polyethersulfone membrane described in the above technical solution. The hydroxyapatite-chitosan modified polyethersulfone membrane captures the diethyldithiocarbamate particulate complex of the metal, thus obtaining a heavy metal enriched solid target. In the present invention, the volume of the suspension system that can be processed by a single hydroxyapatite-chitosan modified polyethersulfone membrane is preferably 10-200 mL, more preferably 50-100 mL. The filtration method preferably includes vacuum filtration or syringe-type membrane filtration. The filtration time is preferably 2-5 min.

[0033] In this invention, the filtration process is a membrane solid-phase extraction and enrichment process. The present invention uses the aforementioned hydroxyapatite-chitosan modified polyethersulfone membrane to filter the suspension system obtained by complexing with alkali metal diethyl dithiocarbamate. Cu(DDTC)₂ particulate complexes are physically retained on the membrane surface, and the chemical adsorption / coordination of the HAP-chitosan composite layer efficiently captures them, achieving solid-phase enrichment of trace copper ions in the liquid and forming a solid target suitable for LIBS detection.

[0034] After obtaining the heavy metal-enriched solid target, this invention uses laser-induced breakdown spectroscopy to detect the heavy metal-enriched solid target, obtaining the static intensity of the characteristic spectral lines of heavy metal elements in the liquid sample to be tested; the concentration of heavy metal ions in the liquid sample to be tested is obtained from the static intensity of the characteristic spectral lines of heavy metal elements in the liquid sample to be tested. In this invention, the preferred detection conditions include: laser wavelength preferably 1064 nm, single pulse energy preferably 50~80 mJ, repetition frequency preferably 5~10 Hz, delay time preferably 0.8~1.5 μs, integration time preferably 1.0~3.0 μs, when the heavy metal ion is Cu 2+ When the detection spectral line is preferably Cu(I) 324.75 nm or Cu(I) 327.40 nm, the preferred spectral line is Cu(I) 324.75 nm or Cu(I) 327.40 nm.

[0035] In this invention, the detection preferably includes: fixing the heavy metal enriched solid target on a LIBS sample stage, and performing laser ablation and spectral acquisition on a selected area of ​​the film surface of the heavy metal enriched solid target.

[0036] In this invention, when the heavy metal ion is Cu 2+ When recording the net spectral intensity of Cu element characteristic spectral lines (preferably Cu(I) 324.75 nm or 327.40 nm), the net spectral intensity is recorded.

[0037] In this invention, in laser-induced breakdown spectroscopy (LIBS), a high-energy laser pulse instantaneously ablates, atomizes, and excites all matter in the sample (regardless of its original state as atoms, molecules, or ions) into a high-temperature plasma. In this plasma, copper primarily exists as neutral atoms (Cu...). 0 ) and primary ionized ions (Cu + They exist in the form of ) and emit their respective characteristic spectra.

[0038] In this invention, the two spectral lines at 324.75 nm and 327.40 nm are the most sensitive and commonly used analytical lines for neutral copper atoms (Cu I), and are widely used in LIBS analysis of copper.

[0039] In this invention, Cu(I) represents a neutral copper atom (Cu). 0 The emission spectral lines of ).

[0040] The present invention preferably uses a calibration curve or linear regression equation between the net intensity of the Cu spectral line and the copper concentration to quantitatively detect the concentration of copper ions in the liquid sample to be tested. The calibration curve or linear regression equation between the net intensity of the Cu spectral line and the copper concentration is established using a series of copper standard solutions of known concentrations (after the same DDTC complexation-membrane enrichment process).

[0041] This invention substitutes the static intensity of the characteristic spectral lines of copper in the liquid sample into a calibration curve or linear regression equation between the net intensity of the Cu spectral lines and the copper concentration to obtain the copper ion concentration in the liquid sample. The detection method provided by this invention has a detection limit of up to 1.5 ppb and a linear correlation coefficient R0. 2 It is usually not lower than 0.99.

[0042] To further illustrate the present invention, the technical solutions provided by the present invention are described in detail below with reference to embodiments, but these should not be construed as limiting the scope of protection of the present invention. The polyethersulfone microporous filter membranes used in the following embodiments and comparative examples were purchased from Tianjin Jinteng Experimental Equipment Co., Ltd. Figure 1A flowchart of a method for detecting copper ions in liquids using membrane solid-phase extraction coupled with laser-induced breakdown spectroscopy provided by this invention is shown below. Figure 1 The detection method provided by the present invention will be described in detail below.

[0043] Example 1: Preparation of hydroxyapatite-chitosan modified polyethersulfone membrane Preparation of functionalized solution: Take 2.0 g of chitosan and add it to 100 mL of 2% (v / v) glacial acetic acid aqueous solution. Stir magnetically until completely dissolved to obtain a chitosan solution with a mass concentration of 2% (w / v). Weigh 2.0 g of nano-hydroxyapatite (average particle size 50 nm) and add it to the above chitosan solution in batches. Disperse by ultrasonication for 30 min to obtain HAP-chitosan functionalized solution, wherein the mass ratio of HAP to chitosan is 1:1. The pH of the functionalized solution is controlled at 4.5±0.5. The base membrane material was a polyethersulfone microporous filter membrane (PES membrane) with a diameter of 13 mm and a pore size of 0.45 μm. 400 μL of functionalized solution was pipetted and added to the center of the PES membrane. The membrane was then spin-coated at 400 rpm for 30 s to ensure that the functionalized solution was evenly spread on the membrane surface. The coated membrane was immediately transferred to a dish containing 3 mol / L NaOH solution and soaked for 5 min to allow the chitosan to neutralize and solidify, forming a stable composite layer with HAP on the PES surface. The membrane surface was thoroughly rinsed with deionized water until the pH of the rinsing solution was close to neutral, and then dried in a 50 ℃ oven to obtain a hydroxyapatite-chitosan modified polyethersulfone membrane, namely the HAP-chitosan / PES functionalized modified membrane.

[0044] Figure 5 These are electron microscope images of the polyethersulfone microporous filter membrane and the hydroxyapatite-chitosan modified polyethersulfone membrane from Example 1. Figure 5 Images (a) and (b) are electron microscope images of the polyethersulfone microporous filter membrane before modification. Figure 5 Images (c) and (d) are electron micrographs of the hydroxyapatite-chitosan modified polyethersulfone membrane. Figure 5 It can be seen that the surface of the hydroxyapatite-chitosan modified polyethersulfone film prepared in Example 1 of the present invention forms a hydroxyapatite-chitosan composite layer composed of hydroxyapatite and chitosan.

[0045] Example 2: Calibration curve and detection limit of copper standard solution Preparation of copper standard solutions and DDTC-Na complexation: Preparation of 6 groups of Cu 2+ Standard solution (in Cu) 2+ (Based on deionized water): 5, 10, 20, 50, 100, 200 ppb; Add 0.5 mL of 0.05 mol / L DDTC-Na solution to every 50 mL of copper standard solution, adjust the pH to 7.5 (using a small amount of NH4Cl-NH3·H2O buffer solution), stir magnetically for 10 min, and let stand for 3 min to generate a water-insoluble Cu(DDTC)2 precipitate suspension.

[0046] Membrane solid-phase enrichment: The HAP-chitosan / PES functionalized modified membrane prepared in Example 1 was loaded into a glass filter funnel; the above suspension was filtered under slight vacuum, and the filtration time was controlled within 3 min; after filtration, the membrane surface was gently rinsed with a small amount of deionized water (about 2 mL) to remove free (excess) DDTC-Na and salts, avoiding washing away the particles, and dried at room temperature for later use.

[0047] LIBS detection: The dried modified film (containing Cu(DDTC)2 particles) was fixed on the LIBS sample stage; a 1064 nm Nd:YAG laser with a single pulse energy of 60 mJ and a frequency of 5 Hz was used to focus on the film surface; the Cu(I) 324.75 nm spectrum was acquired with a delay of 1.0 μs and an integration time of 2.0 μs; 10 different positions were selected for repeated targeting of each film, and the average net spectral intensity was taken to calculate the RSD.

[0048] Table 1. Results of solid-phase extraction-laser-induced breakdown spectroscopy based on polyethersulfone membranes.

[0049] Figure 2 Cu 2+ The fitting curve between the net intensity of the spectral line and the concentration in the water sample was linearly fitted using Cu ion concentration X (ppb) and the net intensity Y of the Cu(I) 324.75 nm spectral line: Y = 383.0 X + 1326, R 2 = 0.9850; where X is the Cu ion concentration in ppb (μg / L) and Y is the net intensity of the Cu(I) 324.75 nm spectral line; By measuring the signal fluctuation of a blank membrane (treated only with DDTC-Na solution and without Cu ions), the following can be calculated using LOD = 3σ / k (where σ is the standard deviation of the blank signal and k is the slope of the calibration curve): The limit of detection (LOD) for copper is approximately 1.5 ppb. This indicates that the method of this invention can achieve rapid quantitative analysis of copper ions in water at the ppb level.

[0050] Figure 7 These are photographs of the membrane materials after processing a series of water samples containing copper ions of different concentrations, as described in this invention. Figure 7 Cu in water samples containing copper ions2+ The concentrations were 50 ppb, 200 ppb, 20 ppb, and 5 ppb, respectively.

[0051] Example 3: Optimization Experiment of Modification Conditions With 50 ppb Cu 2+ Using standard solutions as the subject, the effects of the HAP:chitosan mass ratio and the concentration of chitosan in the chitosan solution on the membrane enrichment performance were investigated.

[0052] 3.1 HAP:Chitosan mass ratio optimization: Keeping the chitosan concentration constant at 2% (w / v), the HAP to chitosan mass ratio was adjusted. Other film-forming conditions were the same as in Example 1, and the detection conditions were the same as in Example 2. The results are shown in Table 2: Table 2. Effect of HAP to chitosan mass ratio on detection results

[0053] As shown in Table 2, the Cu signal intensity and reproducibility are optimal when the HAP:chitosan mass ratio is 1:1.

[0054] 3.2 Optimization of chitosan mass concentration: With a fixed HAP:chitosan mass ratio of 1:1, the chitosan mass concentration in the chitosan solution was adjusted. Other film-forming conditions were the same as in Example 1, and the detection conditions were the same as in Example 2. The results are shown in Table 3. Table 3. Effect of chitosan mass concentration on detection results

[0055] This invention comprehensively considers factors such as film density and flow rate, with 2% (w / v) chitosan being the preferred condition. In this invention, chitosan solution and nano-hydroxyapatite are ultrasonically dispersed to obtain a functionalized HAP-chitosan solution. This HAP-chitosan functionalized solution forms a uniform thin film on the base film, allowing the target metal ions (such as Cu) to be detected. 2+ It can be effectively enriched and fixed on the substrate.

[0056] When the chitosan concentration in the chitosan solution is too low (e.g., 0.1% (w / v)), the film formation is incomplete, the metal sample is unevenly distributed, resulting in large signal fluctuations (high RSD) during laser ablation. When the chitosan concentration in the chitosan solution is moderate (e.g., 2.0% (w / v)), a dense and uniform film is formed, the metal sample is uniformly distributed, and the plasma excitation is stable, resulting in good signal repeatability and high intensity.

[0057] The chitosan used in this invention has good adhesion, which can reduce particle spatter during laser ablation. However, if the chitosan concentration in the solution is too high (e.g., 5.0% (w / v)), the solution viscosity will be too high, resulting in an excessively thick film after drying or the appearance of cracks / agglomerations. This leads to uneven laser energy absorption, plasma instability, and ultimately, a decrease in signal quality.

[0058] Example 4: Anti-interference performance and actual water sample test Using a 50 ppb Cu standard solution as a baseline, common coexisting ions and organic compounds were added, and enrichment and LIBS detection were performed according to the procedure in Example 2. The recovery rates were calculated by comparing the Cu concentrations before and after spiking, as shown in Table 4. Figure 4 As shown: Table 4 shows the recovery rates of Cu concentration before and after spiking.

[0059] Figure 4 For common coexisting ions and organic compounds, Cu 2+ Results of the signal interference experiment. Table 4 and Figure 4 The results show that, in the presence of the above-mentioned typical coexisting components, the Cu recovery rate measured by the method of the present invention is between 96% and 104%, and the RSD is less than 4%, indicating that the method has good resistance to matrix interference.

[0060] Furthermore, this invention conducted spike recovery experiments on actual water samples (such as tap water, river water, and industrial wastewater), and the experimental results are shown in Table 5. The results show that the results of this method are consistent with those of traditional ICP determination and can be used for quantitative analysis of actual water samples.

[0061] Table 5 Results of Spike Recovery Experiments on Actual Water Samples

[0062] Comparative Example 1: LIBS detection of direct water samples Using a 50 ppb Cu standard solution as the target, without DDTC-Na complexation and membrane enrichment, a focused laser was directly applied to the water surface. The detection conditions were the same as in Example 2, and the Cu(I) 324.75 nm spectral line was detected. The results are shown in Table 6. Table 6 shows the test results of Comparative Example 1.

[0063] As shown in Table 6, direct liquid LIBS has low signal intensity, large fluctuations, and a high detection limit; the present invention significantly improves signal intensity and stability through membrane solid phase enrichment, and reduces the detection limit by about two orders of magnitude.

[0064] Comparative Example 2: Unmodified polyethersulfone membrane ( Figure 3 (Unmodified PES in the membrane, a polyethersulfone microporous filter membrane with a diameter of 13 mm and a pore size of 0.45 μm) The commercially available PES microporous membrane (unmodified, 13 mm diameter, 0.45 μm pore size polyethersulfone microporous membrane) from Example 1 was used to directly filter Cu-DDTC suspension and perform LIBS analysis. Comparisons are shown in Table 7 (taking 50 ppb Cu as an example). The results show that the HAP-chitosan modified layer plays a key role in improving enrichment efficiency and signal stability.

[0065] Table 7 shows the test results of Comparative Example 2.

[0066] Comparative Example 3: Membrane with a single modified material Under the same conditions as in Example 1, "chitosan / PES membranes only" (without HAP) were prepared. Figure 3 The chitosan / PES in the sample (also the "0:1 (chitosan only)" sample in Table 2) and the "HAP / PES membrane only" sample (without chitosan) Figure 3 HAP / PES in The preparation method of the chitosan / PES membrane specifically includes: taking 2.0 g of chitosan and adding it to 100 mL of 2% (v / v) glacial acetic acid aqueous solution, stirring magnetically until completely dissolved to obtain a chitosan solution with a mass concentration of 2% (w / v); the pH of the chitosan solution is controlled at 4.5±0.5. The base membrane material is a polyethersulfone microporous filter membrane with a diameter of 13 mm and a pore size of 0.45 μm: 400 μL of chitosan solution is pipetted and added to the center of the PES membrane, and spin-coated at 400 rpm for 30 s to ensure the chitosan solution is evenly spread on the membrane surface; the coated membrane is immediately transferred to a dish containing 3 mol / L NaOH solution and soaked for 5 min to allow the chitosan to neutralize and solidify, forming a stable membrane layer on the PES surface; the membrane surface is thoroughly rinsed with deionized water until the pH of the rinsing solution is near neutral, and then dried in a 50 ℃ oven to obtain the chitosan / PES membrane.

[0067] The specific preparation method of the HAP / PES membrane includes: taking 100 mL of 2% (v / v) glacial acetic acid aqueous solution; weighing 2.0 g of nano-hydroxyapatite (average particle size 50 nm), adding it in batches to the above glacial acetic acid aqueous solution, and ultrasonically dispersing it for 30 min to obtain the HAP functionalized solution; the pH of the HAP functionalized solution is controlled at 4.5±0.5. The base membrane material was a polyethersulfone microporous filter membrane with a diameter of 13 mm and a pore size of 0.45 μm. 400 μL of HAP functionalization solution was pipetted and added to the center of the PES membrane. The membrane was then spin-coated at 400 rpm for 30 s to ensure that the HAP functionalization solution was evenly spread on the membrane surface. The coated membrane was immediately transferred to a dish containing 3 mol / L NaOH solution and soaked for 5 min to allow HAP to form a stable membrane layer on the PES surface. The membrane surface was thoroughly rinsed with deionized water until the pH of the rinsing solution was close to neutral. The membrane was then dried in an oven at 50 ℃ to obtain a hydroxyapatite-modified polyethersulfone membrane, i.e., a HAP / PES membrane.

[0068] The chitosan / PES membrane, HAP / PES membrane prepared in Comparative Example 3, and HAP-chitosan / PES membrane prepared in Example 1 of this invention were compared. The detection method was the same as in Example 2 (taking 50 ppb Cu as an example). The detection results are shown in Table 8.

[0069] Table 8 shows the test results of Comparative Example 3.

[0070] The results in Table 8 demonstrate that the synergistic effect of hydroxyapatite and chitosan significantly enhances the capture and enrichment efficiency of Cu-DDTC, which is key to achieving high signal intensity and low detection limit.

[0071] Figure 3 Comparison of LIBS signal intensity for 50 ppb Cu using different membrane materials. Figure 3 The “HAP-chitosan / PES” in the text refers to the HAP-chitosan / PES functionalized modified membrane prepared in Example 1. Figure 3 "HAP / PES" and "chitosan / PES" in the text refer to the membrane materials prepared in Comparative Example 3. Figure 3 The "unmodified PES" in this context refers to the commercially available PES microporous filter membrane provided in Comparative Example 2. Figure 3 It can be seen that the HAP-chitosan / PES functionalized modified membrane prepared in Example 1 has the highest net intensity of Cu spectral lines.

[0072] Figure 6 For the present invention, for Zn-containing 2+ Cr 3+ Ni 2+ Enrichment and Libs test results of mixed heavy metal water samples. Figure 6 The experimental process is as follows: Formulating a product containing Zn 2+ Cr 3+ Ni 2+ A mixed heavy metal standard water sample was prepared. An excess of sodium diethyldithiocarbamate (DDTC-Na) solution was added to the mixed water sample to adjust the pH to 7.5, allowing the heavy metal ions to fully react with DDTC to form a hydrophobic complex precipitate suspension system. This suspension system was then filtered through a hydroxyapatite-chitosan modified polyethersulfone membrane prepared in Example 1 (vacuum filtration or syringe filtration). The heavy metal-DDTC complex was enriched on the membrane surface through physical retention and chemical adsorption. After washing to remove free reagents, the membrane was dried to prepare a heavy metal enrichment solid target. Finally, laser-induced breakdown spectroscopy (LIBS) was used to detect the solid target. By identifying the characteristic spectral wavelengths of Zn, Cr, and Ni (such as the characteristic emission lines of Zn, Ni, and Cr), and simultaneously obtaining the net intensity of each element's spectral lines, simultaneous enrichment and qualitative / quantitative testing of the mixed heavy metal water sample was achieved.

[0073] Figure 6 (a) and (b) in the text contain Zn, respectively. 2+ Cr 3+ Ni 2+ The LIBS spectrum (or characteristic spectral line identification map of different heavy metal elements) of a water sample enriched with mixed heavy metals is obtained from... Figure 6 It can be seen that the hydroxyapatite-chitosan modified polyethersulfone membrane combined with LIBS technology provided by this invention can achieve simultaneous enrichment and detection of multiple heavy metal ions (such as Zn, Cr, and Ni). In mixed water samples, each element can exhibit clear and independent characteristic emission lines (such as Zn at 213.86 nm, Ni at 231.60 nm, and Cr around 425.44 nm), and there is no obvious spectral interference, which proves that the method has good multi-element simultaneous detection capability and high selectivity.

[0074] Figure 6 Quantitative analysis of Zn is primarily based on the net intensity of the characteristic peak at 213.86 nm. Nickel (Ni): Main detection lines: 231.604 nm (Ni I, high sensitivity) or 341.476 nm (Ni I). Other common lines: 352.454 nm, 344.629 nm, 305.082 nm (Ni I). Note: Figure 6For the identification and quantification of Ni, the characteristic peaks at 231.60 nm or 341.48 nm, which are free from interference, are usually selected. Chromium (Cr): The main detection lines are 425.435 nm (Cr I, strong line) or 427.480 nm (Cr I), and other common lines are 357.869 nm, 359.349 nm, and 428.972 nm (Cr I). Figure 6 The detection of Cr in the medium is mainly based on the characteristic emission spectral line near 425.44 nm.

[0075] Figure 8 The membrane material provided in Example 1 for Zn 2+ and Ni 2+ The fitted curve of net spectral intensity versus concentration in the water sample. Figure 8 The experimental procedure was basically the same as in Example 2, using the hydroxyapatite-chitosan modified polyethersulfone membrane prepared in Example 1. The experimental procedure is as follows: Preparation of zinc, nickel, and Cr standard solutions and their complexation with DDTC-Na: Preparation of 6 groups of Cu 2+ Standard solution (in Zn) 2+ Ni 2+ Cr 3+ (Based on deionized water): 1, 2, 3, 4, 5, 6 mg / L; Add 0.5 mL of 0.05 mol / L DDTC-Na solution to each 50 mL zinc standard solution, nickel standard solution, and Cr standard solution, respectively, adjust the pH to 7.5 (using a small amount of NH4Cl-NH3·H2O buffer solution), stir magnetically for 10 min, and let stand for 3 min to generate water-insoluble Zn(DDTC)2 precipitate suspension, Ni(DDTC)2 precipitate suspension, and Cr(DDTC)2 precipitate suspension.

[0076] Membrane solid-phase enrichment: The HAP-chitosan / PES functionalized modified membrane prepared in Example 1 was loaded into a glass filter funnel; the above suspension was filtered under slight vacuum, and the filtration time was controlled within 3 min; after filtration, the membrane surface was gently rinsed with a small amount of deionized water (about 2 mL) to remove free (excess) DDTC-Na and salts, avoiding washing away the particles, and dried at room temperature for later use.

[0077] LIBS detection: The dried modified film (containing Zn(DDTC)2 particles, Ni(DDTC)2 particles, and Cr(DDTC)2 particles) was fixed on the LIBS sample stage; a 1064 nm Nd:YAG laser with a single pulse energy of 60 mJ and a frequency of 5 Hz was used to focus on the film surface; the delay was 1.0 μs and the integration time was 2.0 μs; the target was repeatedly applied to 10 different positions on each film, and the average net spectral intensity was taken to calculate the RSD.

[0078] Specific details: Zinc (Zn): Main detection line: 213.856 nm (Zn I, atomic line, highest intensity, most commonly used); Auxiliary detection lines: 472.216 nm, 481.053 nm (Zn I) or 202.548 nm (Zn II, ionic line); Figure 8 Zn 2+ Ni 2+ Cr 3+ The fitting curve of net spectral intensity versus concentration in water sample, with Zn 2+ Ni 2+ Cr 3+ The linear fit between concentration X (mg / L) and net intensity Y of the characteristic spectral line is as follows: Y = 688.3X + 1708, R 2 = 0.9000; where X is the Zn ion concentration in mg / L and Y is the net intensity of the Zn(I)2 spectral line at 13.86 nm; Y = 621.9X + 847.4, R 2 = 0.9139; where X is the Ni ion concentration in mg / L and Y is the net intensity of the Ni(I)2 31.60 nm spectral line; Y = 389.9X + 627.6, R 2 = 0.8510; where X is the Cr ion concentration in mg / L and Y is the net intensity of the Cr(I)4 25.44 nm spectral line.

[0079] As can be seen from the above embodiments, this invention relates to the application of membrane solid-phase extraction-laser induced breakdown spectroscopy to analyze heavy metal elements (chitosan contains –NH2 and –OH, which can coordinate with various heavy metal ions; hydroxyapatite (HAP) surface is rich in Ca). 2+ PO4 3- and OH - Pb can be adsorbed through ion exchange and surface complexation. 2+ Cd 2+ Zn 2+ DDTC (sodium diethyldithiocarbamate) is a broad-spectrum metal chelating agent that can react with Cu.2+ Pb 2+ Cd 2+ Ni 2+ Zn 2+ Hydrophobic complexes are formed. LIBS itself has no element selectivity: as long as an element is enriched on the membrane, it can be detected through its characteristic spectral lines. This invention specifically relates to a detection method that utilizes a hydroxyapatite-chitosan modified polyethersulfone membrane to enrich copper-diethyldithiocarbamate complexes in water, achieving rapid and highly sensitive quantitative analysis of trace copper ions in liquids, and its dedicated modified membrane material. The detection method provided by this invention integrates multiple approaches, including heavy metal complexation precipitation, functionalized microporous membrane preparation, solid-phase enrichment, and laser-induced breakdown spectroscopy solid target analysis. It can be widely applied to online monitoring and emergency detection of copper ions in industrial wastewater, surface water, drinking water, and industrial process water. It is also suitable for rapid on-site screening of other heavy metal elements that can form insoluble complexes with organosulfur ligands. This invention focuses on improving the pretreatment enrichment efficiency of copper ions in water samples, enhancing LIBS plasma stability and signal reproducibility under high salinity, complex matrix, or low concentration conditions, providing a technical basis for constructing portable or semi-online water quality heavy metal monitoring systems. Meanwhile, this invention can provide technical support for the engineering application and standardization of laser-induced breakdown spectroscopy in the field of heavy metal monitoring in water environment.

[0080] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a hydroxyapatite-chitosan modified polyethersulfone membrane, characterized in that, Includes the following steps: Chitosan, hydroxyapatite, and an aqueous solution of glacial acetic acid were mixed to obtain a functionalized solution. The functionalized solution was coated onto the surface of a polyethersulfone microporous filter membrane, and then neutralized and cured with alkali to obtain a hydroxyapatite-chitosan modified polyethersulfone membrane.

2. The preparation method according to claim 1, characterized in that, The average particle size of the hydroxyapatite is 20~100nm; the volume fraction of glacial acetic acid in the aqueous acetic acid solution is 1.5~3%; the mass ratio of the hydroxyapatite to the chitosan is (0.5~2):1; and the pH value of the functionalized solution is 3.5~5.

5.

3. The preparation method according to claim 1, characterized in that, The polyethersulfone microporous filter membrane has a pore size of 0.22~0.45μm and a diameter of 13~25mm.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The coating method includes spin coating or vacuum filtration; the volume ratio of the functionalized solution to the diameter of the polyethersulfone microporous filter membrane is (200~400) μL : (13~25) mm; when the coating method is spin coating, the spin coating speed is 200~500 rpm and the time is 20~40 s; the alkali neutralization and curing is performed using sodium hydroxide solution, the molar concentration of NaOH in the sodium hydroxide solution is 1~3 mol / L, and the alkali neutralization and curing time is 5~10 min; after alkali neutralization and curing, the process further includes sequential water washing and drying, and the drying temperature is 45~60℃.

5. The hydroxyapatite-chitosan modified polyethersulfone membrane prepared by the preparation method according to any one of claims 1 to 4.

6. The application of the hydroxyapatite-chitosan modified polyethersulfone membrane according to claim 5 in the detection of heavy metal ions using membrane solid-phase extraction-laser induced breakdown spectroscopy.

7. A method for detecting heavy metal ions in liquids using membrane solid-phase extraction coupled with laser-induced breakdown spectroscopy, characterized in that, Includes the following steps: A liquid sample containing heavy metal ions is mixed with an alkali metal diethyldithiocarbamate to undergo a complexation reaction, resulting in a suspension system containing a particulate complex of the heavy metal diethyldithiocarbamate. The suspension system is filtered through the hydroxyapatite-chitosan modified polyethersulfone membrane of claim 5, wherein the hydroxyapatite-chitosan modified polyethersulfone membrane captures the diethyldithiocarbamate particulate complex of the heavy metal to obtain a heavy metal enriched solid target. The heavy metal-enriched solid target was detected by laser-induced breakdown spectroscopy to obtain the static intensity of the characteristic spectral lines of heavy metal elements in the liquid sample to be tested. The concentration of heavy metal ions in the liquid sample is obtained from the static intensity of the characteristic spectral lines of heavy metal elements in the liquid sample to be tested.

8. The detection method according to claim 7, characterized in that, The alkali metal diethyldithiocarbamate is sodium diethyldithiocarbamate; the heavy metal ions include one or more of copper ions, iron ions, lead ions, cadmium ions, nickel ions, zinc ions, and chromium ions; the molar ratio of the alkali metal diethyldithiocarbamate to the heavy metal ions in the liquid sample to be tested is ≥3:

1.

9. The detection method according to claim 7 or 8, characterized in that, The pH value of the complexation reaction is 6.5-9; the time of the complexation reaction is 5-15 min; the complexation reaction is followed by a settling treatment of the obtained complexation reaction solution for 2-5 min.

10. The detection method according to claim 7, characterized in that, The detection conditions include: laser wavelength of 1064 nm, single pulse energy of 50-80 mJ, repetition frequency of 5-10 Hz, delay time of 0.8-1.5 μs, integration time of 1.0-3.0 μs, and when the heavy metal ion is copper ion, the detection spectral line is Cu(I) 324.75 nm or Cu(I) 327.40 nm.

Images