Ultra-trace thallium analysis system and method

Abstract

The invention discloses an ultra-trace thallium analysis system and method. The ultra-trace thallium analysis system comprises a pretreatment unit, a separation and enrichment unit, a pH regulation unit and a detection unit. The pretreatment unit is used for filtering, acidifying and oxidizing a water sample to be treated to obtain a pretreated water sample; the separation and enrichment unit is used for enriching thallium ions in the pretreated water sample and separating out interfering ions; the pH adjusting unit reduces the acidity of the enriched water sample to obtain a water sample to be analyzed; the detection unit receives the water sample to be analyzed and carries out thallium analysis detection on the water sample to be analyzed. Wherein the pH adjusting unit comprises a pH adjusting column, and the pH adjusting column comprises hydroxyl type resin and is used for exchanging anions in the enriched water sample and carrying out neutralization reaction with H < + > in the enriched water sample so as to reduce the acidity of the enriched water sample, so that the compatibility contradiction between the solid-phase extraction elution acidity and the liquid anode glow discharge spectrum sample introduction acidity in the prior art is overcome; meanwhile, interference cations are prevented from being introduced, and high-sensitivity analysis on trace thallium in water is realized.

Description

Technical Field

[0001] This application relates to the analysis and detection of heavy metals, and more particularly to an ultra-trace thallium analysis system and method. Background Technology

[0002] Thallium, a highly toxic heavy metal, is crucial for environmental pollution control through trace detection in water bodies. my country's "Surface Water Environmental Quality Standard" (GB3838-2002) and "Standards for Drinking Water Quality" (GB5749-2022) stipulate a thallium concentration limit of 0.1 μg / L, posing a significant challenge to the sensitivity and interference resistance of existing detection technologies.

[0003] Currently, common methods for thallium detection include spectrophotometry, anodic stripping voltammetry, atomic absorption spectrometry, and inductively coupled plasma mass spectrometry (ICP-MS / MS). Among these, spectrophotometry and ICP-MS have relatively low sensitivity but high detection limits. Anodic stripping voltammetry, while portable and fast, suffers from poor electrode stability and matrix interference, leading to insufficient accuracy and reproducibility. Graphite furnace atomic absorption spectrometry involves cumbersome pretreatment steps and is severely affected by matrix interference. While ICP-MS offers excellent analytical performance, its expensive instruments and reliance on laboratory conditions limit its practical application in the rapid detection of trace thallium in environmental water samples. In contrast, liquid cathode glow discharge spectrometry (SCGD-OES) offers advantages such as portability, low energy consumption, operation at ambient pressure, and low cost, making it a promising candidate for environmental monitoring. However, the detection limit of SCGD-OES for Tl cannot meet the requirement of 0.1 μg / L in my country's water quality standards, and the recovery rate is low under high-salt matrix conditions.

[0004] In recent years, liquid anodic glow discharge spectroscopy (SAGD-OES), as a novel micro-plasma technique, has shown superior detection capabilities (detection limit < 0.1 μg / L) for volatile elements (Ag, Bi, Cd, In, Hg, Pb, Zn, Tl) compared to SCGD-OES. However, this technique has significant limitations in its tolerance to matrix interference: when the concentration of alkali metal (K, Na) / alkaline earth metal (Ca, Mg) ions is ≥ 10 mg / L, the recovery rate of thallium drops below 70%. This is because the concentration of Ca in actual water samples (such as tap water and surface water) is relatively low. 2+ Mg 2+ Na + The concentration of plasma generally exceeds 10 mg / L. Balancing high-sensitivity detection with tolerance to alkali / alkaline earth metals has become the core bottleneck of this technology.

[0005] Currently, SAGD-OES technology mainly employs dilution methods, standard addition methods, masking agents to complex transition metals, and crown ethers to complex alkali / alkaline earth metals to overcome matrix interference. However, dilution methods reduce the concentration of target analytes, severely affecting the accuracy of trace detection; while standard addition methods can match matrix effects, the sample matrix itself reduces detection sensitivity; masking agents and crown ethers can selectively complex interfering ions, but the recovery rate of thallium is still below 75%, and subsequent introduction of antioxidants has not shown significant improvement. This indicates that chemical modification is insufficient to overcome the matrix interference bottleneck of SAGD-OES. A more fundamental solution lies in utilizing the synergistic effect of enriching target elements and separating the matrix to simultaneously reduce interference suppression and improve detection sensitivity. For example, solid-phase extraction (SPE), through a selective adsorption-elution mechanism, can efficiently enrich target elements and specifically exclude interference from coexisting ions. In recent years, it has been successfully introduced into liquid cathode glow discharge spectroscopy systems.

[0006] However, there is a clear contradiction between the high acidity requirement for SPE elution and the low acidity limitation imposed by the introduction of SCGD-OES samples. At present, research on the combination of solid phase extraction and liquid anodic glow discharge spectroscopy is still lacking.

[0007] Therefore, how to improve the technical defects existing in the prior art has always been a problem that ordinary people skilled in the art need to solve. Summary of the Invention

[0008] The purpose of this application is to provide an ultra-trace thallium analysis system and method that breaks through the technical gap of combining solid-phase extraction with liquid anodic glow discharge spectroscopy, enabling highly sensitive analysis of trace thallium in water.

[0009] The technical solution provided by this invention is as follows:

[0010] An ultra-trace thallium analysis system, comprising:

[0011] The pretreatment unit, separation and enrichment unit, pH adjustment unit, and detection unit are connected in sequence.

[0012] The pretreatment unit is used to filter, acidify, and oxidize the water sample to obtain a pretreated water sample; the separation and enrichment unit is used to enrich thallium ions in the pretreated water sample and separate interfering ions; the pH adjustment unit is used to adjust the pH value of the enriched water sample to reduce its acidity and obtain the water sample to be analyzed; the detection unit is used to receive the water sample to be analyzed and to analyze and detect thallium in the water sample.

[0013] The pH adjustment unit includes a pH adjustment column, which contains hydroxide-type resin for exchanging anions in the enriched water sample and reacting with H+ in the enriched water sample. +A neutralization reaction occurs to reduce the acidity of the enriched water sample.

[0014] In some embodiments, the pH adjustment unit further includes an alkaline solution supplier and a buffer solution supplier, both of which are connected to the pH adjustment column. The alkaline solution supplier supplies alkaline solution to the pH adjustment column for the regeneration of hydroxide-type resin; the buffer solution supplier supplies buffer solution to the pH adjustment column to wash away residual cations and adjust the pH value of the pH adjustment column.

[0015] In some embodiments, the pH adjusting column is connected to a first inlet pipe and a first outlet pipe;

[0016] The inlet end of the first inlet pipe is equipped with a first three-way valve. One port of the first three-way valve is connected to the separation and enrichment unit, and the other port of the first three-way valve is connected to the alkaline solution supplier and the buffer solution supplier. The outlet end of the first outlet pipe is equipped with a second three-way valve. One port of the second three-way valve is connected to a temporary storage bottle for storing the water sample to be analyzed, and the other port of the second three-way valve is connected to the first drain pipe for discharging waste liquid.

[0017] In some embodiments, the first three-way valve is connected to a first connecting pipeline, the first connecting pipeline is provided with a first six-way valve, and the first six-way valve is connected to an alkaline solution supplier and a buffer solution supplier respectively.

[0018] In some embodiments, the temporary storage bottle is connected to a second connecting pipe, which is connected to the detection unit, and the second connecting pipe is equipped with a first pump body, which is used to pump the water sample to be analyzed in the temporary storage bottle to the detection unit.

[0019] In some embodiments, the hydroxide-type resin is a strongly basic anion exchange resin, a weakly basic anion exchange resin, or an ammonium-type resin; and the detection unit is a liquid anodic glow discharge spectrometer.

[0020] In some embodiments, the detection unit includes an anode tube, a cathode tube, a graphite electrode, and a DC power supply. The anode tube is connected to a pH adjustment unit. The water sample to be analyzed is prepared by adding dilute nitric acid solution and then overflowing from the anode tube. The anode tube is in contact with the graphite electrode to form a discharge anode. A carrier gas is introduced into the cathode tube to form a discharge cathode. The DC power supply applies a high-voltage current to the discharge anode and discharge cathode to generate glow discharge micro-plasma between the discharge anode and discharge cathode in the water sample to be analyzed.

[0021] In some embodiments, the pretreatment unit includes a water sample storage container, an oxidant supplier, and an acid solution supplier. The water sample storage container is used to store the water sample to be treated. The oxidant supplier and the acid solution supplier are both connected to the water sample storage container so that the water sample to be treated is mixed with the supplied oxidant and acid solution to form a pretreated water sample.

[0022] In some embodiments, the separation and enrichment unit includes an enrichment column, a pure water supply unit, and an eluent supply unit, and the water sample storage container, acid solution supply unit, pure water supply unit, and eluent supply unit are all connected to the enrichment column.

[0023] The enrichment column includes a chelating resin for adsorbing thallium ions in the pretreated water sample and separating interfering ions from the pretreated water sample; an acid solution supplier for supplying acid solution to the enrichment column to activate and regenerate the chelating resin; an eluent supplier for supplying eluent to the enrichment column after the pretreated water sample enters the enrichment column to elute the thallium ions on the enrichment column and obtain the enriched water sample; and a pure water supplier for supplying pure water to the enrichment column to clean the activated and regenerated chelating resin and rinse away any residual interfering ions on the enrichment column.

[0024] This application also provides a method for ultra-trace thallium analysis, including the following steps:

[0025] Collect water samples to be treated;

[0026] Microporous membrane filters out insoluble substances in water samples to be treated;

[0027] The water sample to be treated is mixed with an acid solution and an oxidant to carry out acidification and oxidation reactions, forming a pretreated water sample;

[0028] The pretreated water sample flows into the enrichment column, which is filled with chelating resin to adsorb thallium ions and separate interfering ions.

[0029] Pump pure water into the enrichment column to rinse away interfering ions on the enrichment column;

[0030] Eluent was pumped into the enrichment column to elute thallium ions on the enrichment column and obtain a enriched water sample.

[0031] After enrichment, the water sample flows into a pH adjustment column, which is filled with hydroxide-type resin to adjust the pH value of the enriched water sample to 6-7, and then the water sample to be analyzed is obtained.

[0032] After adding dilute nitric acid to the water sample to be analyzed, the liquid anodic glow discharge atomic emission spectrometry method was used to analyze and detect the water sample.

[0033] In some implementations, the process includes the following steps before the enriched water sample flows into the pH adjustment column:

[0034] Pump an alkaline solution into the pH adjustment column and flush the hydroxide resin at a flow rate of 1-5 mL / min to regenerate the hydroxide resin.

[0035] Pump buffer solution into the pH adjustment column and rinse the hydroxyl-type resin at a flow rate of 1-10 mL / min to remove residual cations and adjust the pH of the hydroxyl-type resin to 6-7.

[0036] The technical advantages of this application are as follows:

[0037] 1. This application overcomes the compatibility issue between solid-phase extraction elution acidity and liquid anolyte glow discharge spectroscopy injection acidity in existing technologies by introducing a pH adjustment unit and setting a pH adjustment column, based on a resin-based solution pH adjustment method. This broadens its application scope in environmental monitoring. Furthermore, the pH adjustment column includes hydroxide-type resin, which not only adjusts the pH value of the enriched water sample but also avoids the introduction of interfering cations, such as Na+. + NH4 + This improves detection sensitivity and accuracy, thereby enabling the ultra-trace thallium analysis system to perform highly sensitive analysis of trace thallium in water.

[0038] 2. In this application, the pH adjustment unit also includes an alkaline solution supplier and a buffer solution supplier. Before the enriched water sample enters the pH adjustment column, an alkaline solution is first introduced to regenerate the hydroxide-type resin, and then a buffer solution is introduced to clean the residual cations in the pH adjustment column and adjust the pH value of the pH adjustment column. This effectively avoids cation interference, ensures the adjustment function of the pH adjustment column, and realizes the long-term stable operation of the pH adjustment unit so as to enable real-time analysis of ultra-trace thallium.

[0039] 3. In this application, a neutral water sample to be analyzed is obtained through a pH adjustment unit. After adding dilute nitric acid solution to the water sample, it is detected by a liquid anodic glow discharge spectrometer. This effectively solves the problem that liquid anodic glow discharge technology requires a suitable acidity to effectively generate analyte vapor. During the detection process, the water sample to be analyzed continuously overflows from the anode tube, which can stabilize the plasma discharge and avoid the memory effect. The introduction of carrier gas into the cathode tube not only regulates the gas flow but also plays a cooling role, preventing the discharge cathode from overheating and ensuring the normal operation of the liquid anodic glow discharge spectrometer.

[0040] 4. In this application, the enrichment column includes a chelating resin, which has high selectivity and can efficiently adsorb thallium ions in pretreated water samples while separating other interfering ions. Moreover, the chelating resin also has good adsorption capacity for low concentrations of thallium, which can effectively enrich trace amounts of thallium in water and ensure the accuracy of detection. Combined with the hydroxide-type resin of the pH adjustment column, the interference problem of coexisting ions in liquid anodic glow discharge atomic emission spectroscopy is successfully solved. Attached Figure Description

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0042] Figure 1 This is a schematic diagram of the structure of an ultra-trace thallium analysis system provided in one embodiment of this application.

[0043] Figure label:

[0044] 1. Filter; 2. Water sample storage container; 3. Magnetic stirring rotor; 4. Third connecting pipe; 5. Branch line; 6. Second pump body; 7. Oxidant supplier; 8. Acid solution supplier; 9. Pure water supplier; 10. First eluent supplier; 11. Second eluent supplier; 12. Second six-way valve; 13. Fourth connecting pipe; 14. Third pump body; 15. Second inlet pipe; 16. Enrichment column; 17. Second outlet pipe; 18. Third three-way valve; 19. Waste liquid container; 20. First three-way valve; 21. First connecting pipe Piping; 22. First six-way valve; 23. Alkaline solution supplier; 24. Buffer solution supplier; 25. First inlet pipe; 26. pH adjustment column; 27. First outlet pipe; 28. Second three-way valve; 29. ​​Temporary storage bottle; 30. First pump body; 31. Second connecting pipe; 32. Anode tube; 33. Graphite electrode; 34. Ballast resistor; 35. DC power supply; 36. Cathode tube; 37. Carrier gas; 38. Waste discharge pipe; 39. Waste liquid tank; 40. Condensing lens; 41. Optical fiber; 42. Miniature spectrometer; 43. Computer. Detailed Implementation

[0045] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application can also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0046] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the specific implementation methods of this application will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without creative effort.

[0047] To keep the drawings concise, each drawing only schematically shows the parts relevant to this application, and they do not represent the actual structure of the product. Furthermore, for ease of understanding, in some drawings, only one of the components with the same structure or function is schematically shown, or only one is labeled. In this document, "one" not only means "only one," but can also mean "more than one."

[0048] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0049] In this document, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0050] In the embodiments shown in the accompanying drawings, the directional indications (such as up, down, left, right, front, and back) used to explain the structure and movement of the various components of this application are relative rather than absolute. These descriptions are appropriate when these components are in the positions shown in the drawings. If the descriptions of the positions of these components change, these directional indications also change accordingly.

[0051] Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0052] Liquid anodic glow discharge spectroscopy (LAD), as a novel microplasma technique, offers superior ultra-trace detection capabilities for volatile elements (Ag, Bi, Cd, In, Hg, Pb, Zn, Tl) compared to liquid cathode glow discharge spectroscopy. However, this technique suffers from significant limitations in its tolerance to matrix interference: when the concentration of alkali metal (K, Na) / alkaline earth metal (Ca, Mg) ions is ≥10 mg / L, the recovery rate of thallium drops below 70%. Currently, solid-phase extraction (SPE) can be used to overcome matrix interference by employing a selective adsorption-elution mechanism, which can efficiently enrich the target element while specifically eliminating interference from coexisting ions. However, this method is currently only used in liquid cathode glow discharge spectroscopy due to a significant contradiction between the high acidity requirements of SPE elution and the low acidity limitations imposed by liquid cathode glow discharge spectroscopy on sample introduction.

[0053] In response, this application discloses an ultra-trace thallium analysis system that can overcome the compatibility contradiction between the acidity of solid-phase extraction elution and the acidity of sample introduction in liquid anodic glow discharge spectroscopy in the prior art, and solve the problem that the tolerance of liquid anodic glow discharge spectroscopy to matrix interference is significantly limited. It has the advantages of simple operation, low power consumption, low cost and small size, and can analyze ultra-trace thallium in real time.

[0054] Specifically, see Figure 1The ultra-trace thallium analysis system comprises a pretreatment unit, a separation and enrichment unit, a pH adjustment unit, and a detection unit connected in sequence. The pretreatment unit filters, acidifies (adjusts the pH of the water sample to 1-7), and oxidizes the water sample to obtain a pretreated water sample. The separation and enrichment unit enriches thallium ions in the pretreated water sample and separates interfering ions. The pH adjustment unit adjusts the pH of the enriched water sample, specifically including a pH adjustment column 26, which further includes hydroxide ions (OH-). - Type 1 resin is used to exchange anions in enriched water samples and react with H+ in the enriched water samples. + A neutralization reaction occurs, thereby reducing the acidity of the enriched water sample and obtaining the water sample to be analyzed; the detection unit is used to receive the water sample to be analyzed and to analyze and detect thallium in the water sample to be analyzed.

[0055] This embodiment, by setting up a pretreatment unit, a separation and enrichment unit, and a detection unit, realizes the steps of water sample pretreatment, enrichment, elution, pH adjustment, and online detection. In particular, in the pH adjustment step, the method of adjusting the solution pH based on resin effectively solves the problem that liquid anodic glow discharge technology requires a suitable acidity to effectively generate analyte vapor. It overcomes the compatibility contradiction between the acidity of solid phase extraction elution and the acidity of liquid anodic glow discharge spectroscopy in the prior art, broadens its application scope in the field of environmental monitoring, realizes the joint use of solid phase extraction system and liquid anodic glow discharge spectrometer, and successfully solves the interference problem of coexisting ions in liquid anodic glow discharge atomic emission spectroscopy.

[0056] The pH adjustment column 26 uses hydroxyl-type resin as packing material, which not only enables pH adjustment of the enriched water sample but also avoids the introduction of interfering cations, such as Na+. + NH4 + This improves detection sensitivity and accuracy, thereby enabling highly sensitive analysis of trace thallium in water using an ultra-trace thallium analysis system, which is beneficial for online analysis of ultra-trace thallium. The hydroxide-type resin can be a strongly basic anion exchange resin, a weakly basic anion exchange resin (e.g., 717 resin), or an ammonium-type resin (e.g., polyamine CR20 resin), which will not be elaborated further here, but are all within the scope of protection of this application.

[0057] Furthermore, the pH adjustment unit also includes an alkaline solution supplier 23 and a buffer solution supplier 24, both of which are connected to the pH adjustment column 26. The alkaline solution supplier 23 supplies alkaline solution to the pH adjustment column 26, while the buffer solution supplier 24 supplies a buffer solution, such as ammonium acetate buffer, to the pH adjustment column 26. This allows for the regeneration of the hydroxide-type resin by first introducing an alkaline solution before the enriched water sample enters the pH adjustment column 26, followed by the introduction of a buffer solution to wash away residual cations in the pH adjustment column 26 and adjust its pH value. This effectively avoids cation interference, ensures the pH adjustment function of the column 26, achieves long-term stable operation of the pH adjustment unit, and ultimately improves the performance of the ultra-trace thallium analysis system.

[0058] Specifically, the pH adjustment column 26 is connected to a first inlet pipe 25 and a first outlet pipe 27. The inlet end of the first inlet pipe 25 is equipped with a first three-way valve 20. One of the remaining two ports of the first three-way valve 20 is connected to the separation and enrichment unit, and the other port is connected to the alkaline solution supplier 23 and the buffer solution supplier 24. The outlet end of the first outlet pipe 27 is equipped with a second three-way valve 28. One of the remaining two ports of the second three-way valve 28 is connected to a temporary storage bottle 29 for storing the water sample to be analyzed, and the other port of the second three-way valve 28 is used to discharge waste liquid.

[0059] The first three-way valve 20 is connected to the port of the alkaline solution supplier 23 and the buffer solution supplier 24 by a first connecting pipe 21. The first connecting pipe 21 is equipped with a first six-way valve 22, which connects the alkaline solution supplier 23 and the buffer solution supplier 24 respectively. By switching the first six-way valve, the alkaline solution and the buffer solution can be delivered sequentially, avoiding the mixing of alkaline solution and buffer solution and causing bubble interference, thus further ensuring the accuracy of detection.

[0060] The temporary storage bottle 29 is connected to a second connecting pipe 31, which leads to the detection unit. The second connecting pipe 31 is equipped with a first pump 30, which pumps the water sample to be analyzed from the temporary storage bottle 29 to the detection unit. The detection unit is a liquid anodic glow discharge spectrometer. In this embodiment, the water sample to be analyzed is adjusted to neutral (pH = 6-7) by the pH adjustment unit before entering the temporary storage bottle 29. Dilute nitric acid (e.g., 0.1 mL of 0.5 mol / L nitric acid solution) should be added to the temporary storage bottle 29 first to control the acidity of the water sample to be analyzed to be comparable to that of the 0.01 mol / L dilute nitric acid. After measurement with a conductivity meter, the sample is then pumped by the first pump 30. The first pump 30 is preferably a peristaltic pump, which can automatically pump the water sample from the temporary storage bottle 29 to the detection unit, achieving automatic sample delivery and further improving the automation level of the ultra-trace thallium analysis system.

[0061] To further enhance the ability of the ultra-trace thallium analysis system to resist interference from coexisting ions, the separation and enrichment unit includes an enrichment column 16, which further comprises a chelating resin. The chelating resin exhibits high selectivity and efficiently adsorbs thallium ions from pretreated water samples while separating other interfering ions. Specifically, the chelating resin can be an iminodiacetic acid type resin, with Chelex-100 and D401 resins being preferred. These resins demonstrate good enrichment effects for both high (μg / L) and low (ng / L) concentrations of thallium, thereby effectively reducing the influence of interfering ions in the matrix environment on the selective adsorption of thallium ions and improving detection accuracy.

[0062] Considering that iminodiacetic acid type resins react with K under pH conditions of 1-2... + Na + Ca2 + Mg2 + Since common matrix ions are not adsorbed, when acidifying the water sample to be treated, it is preferable to acidify the water sample to be treated to pH=1-2, thereby further improving the selective adsorption of thallium ions by the enrichment column 16 in the subsequent enrichment step.

[0063] Specifically, the pretreatment unit includes a water sample storage container 2, an oxidant supplier 7, and an acid solution supplier 8. The water sample storage container 2 is used to store the water sample to be treated. Both the oxidant supplier 7 and the acid solution supplier 8 are connected to the water sample storage container 2 so that the water sample to be treated is mixed with the supplied oxidant and acid solution to form a pretreated water sample. The acid solution is preferably a nitric acid solution or a hydrochloric acid solution to acidify the water sample to pH 1-2. The oxidant is used to oxidize monovalent thallium in the water sample to hypervalent thallium, which is more conducive to the selective adsorption of thallium ions by the iminodiacetic acid type resin. Since the addition of the acid solution acidifies the water sample to pH 1-2, bromine water is preferably used as the oxidant. Bromine water has stronger oxidizing power under acidic conditions and more easily oxidizes monovalent thallium in the water sample to hypervalent thallium.

[0064] In actual production, the oxidant supplier 7 supplies bromine water with a concentration of 0.5%-5%, and the acid solution supplier 8 supplies acid solution with a concentration of 1%-10%. Bromine water and acid solution are added to the water sample at a ratio of 0.5%-5% of the sample volume, with the ratio of added bromine water to added acid solution being 1:1. The water sample, bromine water, and acid solution are stirred and mixed for 2-10 minutes to obtain the pretreated water sample. Notably, the water sample does not fade after 5 minutes of adding bromine water.

[0065] In this embodiment, one of the oxidant supplier 7 and the acid solution supplier 8 is connected to the water sample storage container 2 via a third connecting pipe 4, and this third connecting pipe 4 has a branch connecting to the other of the oxidant supplier 7 and the acid solution supplier 8. A second pump body 6 is connected to the third connecting pipe 4. The second pump body 6 is preferably a micro peristaltic pump, capable of automatically pumping bromine water and acid solution, for example, at a ratio of 1% of the volume of the water sample to be treated, into the water sample storage container 2, with the ratio of pumped bromine water to pumped acid solution being 1:1. Furthermore, the water sample storage container 2 may also be equipped with a magnetic stirring rotor 3, which can achieve automated stirring of the water sample, bromine water, and acid solution, resulting in a high degree of automation.

[0066] Furthermore, the pretreatment unit also includes a filter 1, which comprises a microporous membrane with a pore size of 0.22-0.45 μm, capable of effectively removing insoluble matter from the water sample as it flows through. The filter 1 is connected to a water sample storage container 2 so that the filtered water sample can enter the water sample storage container 2 for subsequent mixing and reaction.

[0067] Specifically, the separation and enrichment unit also includes a pure water supplier 9 and an eluent supplier. The water sample storage container 2, acid solution supplier 8, pure water supplier 9, and eluent supplier are all connected to the enrichment column 16. Thus, before the pretreated water sample enters the enrichment column 16, acid solution can be supplied to the enrichment column 16 by the acid solution supplier 8 to activate the iminodiacetic acid type resin. Then, pure water is supplied to the enrichment column 16 by the pure water supplier 9 to rinse away residual impurities, effectively improving the selectivity of the iminodiacetic acid type resin and making it more conducive to the enrichment of thallium ions. After the pretreated water sample enters the enrichment column 16, eluent is first supplied to the enrichment column 16 to elute the thallium ions on the enrichment column 16, obtaining the enriched water sample. Then, pure water is supplied to the enrichment column 16 by the pure water supplier 9 to rinse away any remaining interfering ions on the enrichment column 16.

[0068] The eluent is a mixture of two solutions. Specifically, the eluent supply device further includes a first eluent supply device 10 and a second eluent supply device 11. The first eluent supply device 10 is used to supply 5 mL of a mixed solution of 1%-10% nitric acid and 0.1%-6% sulfurous acid to the enrichment column 16 (in actual operation, a mixed solution of 6% nitric acid and 0.6% sulfurous acid can be used, for example). The second eluent supply device 11 is used to supply 3 mL of a nitric acid solution with pH=2 to the enrichment column 16, and the elution flow rate of the eluent is 0.5-4 mL / min.

[0069] The enrichment column 16 is connected to a second inlet pipe 15 and a second outlet pipe 17. The inlet end of the second inlet pipe 15 is equipped with a second six-way valve 12. The remaining five ports of the second six-way valve 12 are respectively connected to five fourth connecting pipes 13, which are respectively connected to the water sample storage container 2, the acid solution supplier 8, the pure water supplier 9, the first eluent supplier 10, and the second eluent supplier 11. In this embodiment, by switching the second six-way valve 12, the acid solution, pure water, pretreated water sample, and eluent can be sequentially delivered, avoiding solution mixing and bubble interference, thus ensuring the accuracy of the detection. Conversely, the outlet end of the second outlet pipe 17 is connected to a third three-way valve 18. One of the remaining two ports of the third three-way valve 18 is connected to a first three-way valve 20, and the other port is connected to a waste liquid container 19 for discharging and collecting waste liquid.

[0070] The second inlet pipe 15 is equipped with a third pump body 14, which is preferably a peristaltic pump, capable of pumping the liquid (acid solution, pure water, pretreated water sample, eluent, or any one of these) in the second inlet pipe 15 to the enrichment column 16, thereby achieving automatic liquid delivery.

[0071] Specifically, the detection unit includes an anode tube 32, a cathode tube 36, a graphite electrode 33, and a DC power supply 35. The anode tube 32 is connected to a pH adjustment unit. The water sample to be analyzed is prepared by adding dilute nitric acid solution and then overflowing from the anode tube 32, with the anode tube 32 contacting the graphite electrode 33 to form a discharge anode. At this time, the water sample to be analyzed is one of inorganic acids such as nitric acid or hydrochloric acid with a pH value between 1.8 and 2.5. By adjusting the flow rate of the first pump body 30 to 2.5-5.5 mL / min, the water sample to be analyzed can continuously overflow from the top of the anode tube 32. The continuous overflow of the water sample to be analyzed can stabilize the plasma discharge and avoid the memory effect. Conversely, a carrier gas 37 is introduced into the cathode tube 36 to form a discharge cathode. The DC power supply 35 applies a high-voltage current to the discharge anode and discharge cathode to generate glow discharge micro-plasma between the discharge anode and discharge cathode. The anode tube 32 is made of tungsten or similar materials, and its inner diameter is approximately 1-2 mm and its outer diameter is approximately 2-4 mm. In contrast, the cathode tube 36 is a hollow tungsten cathode tube, with an inner diameter of approximately 1-3 mm and an outer diameter of approximately 2-5 mm.

[0072] In practical use, the carrier gas 37 can be hydrogen-helium or helium. Taking hydrogen-helium as an example, its gas flow rate is 200-500 mL / min, and the ratio of hydrogen to helium is 3:97. In this case, the carrier gas 37 not only regulates the gas flow but also plays a cooling role, preventing the discharge cathode from overheating and being damaged.

[0073] Specifically, the detection unit also includes a ballast resistor 34, a waste liquid tank 39, a waste discharge pipe 38, a three-dimensional platform, a focusing lens, an optical fiber 41, a miniature spectrometer 42, and a computer 43. The DC power supply 35 is a high-voltage power supply capable of providing 0-1500V DC high voltage and 0-200mA DC current. The negative terminal of this DC power supply 35 is connected to the cathode tube 36, and the positive terminal is connected to the ballast resistor 34 and the graphite electrode 33. The graphite electrode 33 horizontally penetrates the wall of the waste liquid tank 39 and is fixed to one side of the waste liquid tank 39, which is located directly below the cathode tube. The anode tube 32 vertically passes through the perforated graphite electrode 33 and the bottom of the waste liquid tank 39, and is located directly below the cathode tube 36. The anode tube 32 vertically passes through the bottom of the waste liquid tank 39. The cathode tube 36 and the waste liquid tank 39 are fixed on a three-dimensional platform with an adjustable accuracy of 2μm in the X, Y, and Z directions. At this time, the glow discharge region is the area 1-3mm between the two vertically placed discharge anodes and discharge cathodes. The light radiation signal generated in the glow discharge region is focused by the focusing lens 40, and the focused light radiation signal is transmitted by the optical fiber 41 and coupled to the entrance slit of the micro spectrometer 42. The detection results are then processed and recorded by the computer 43 to realize the detection of trace thallium.

[0074] The preferred detection wavelength of the miniature spectrometer 42 is 377.6 nm, the preferred electrode spacing is 1-3 mm, the preferred voltage is 700-1500 V, and the preferred current is 40-100 mA.

[0075] Preferably, the ultra-trace thallium analysis system also includes a control unit, which is connected to the separation and enrichment unit, pH adjustment unit and detection unit respectively. It can control the operation of each unit, significantly improve the analysis efficiency, and enable the ultra-trace thallium analysis system to meet the needs of field detection and dynamic environmental monitoring, and has significant social benefits and promotion value.

[0076] This application also provides an ultra-trace thallium analysis method, comprising the following steps: 1) extracting approximately 50-100 mL of water sample to be treated, wherein during the extraction process, the water sample is first filtered through a microporous membrane to remove insoluble matter, and then stored in a water sample storage container 2; 2) mixing the water sample with an acid solution (1%-10% nitric acid) to adjust the pH value, and then mixing with an oxidant (1%-5% bromine water) to carry out acidification and oxidation reactions to form a pretreated water sample; 3) the pretreated water sample flows into an enrichment column 16, which is filled with chelating resin to adsorb thallium ions and separate interfering ions; 4) pumping into the enrichment column 16... 5) Use pure water to rinse away the interfering ions remaining on the enrichment column 16; 6) Pump eluent into the enrichment column 16 to elute the thallium ions on the enrichment column 16 and obtain the enriched water sample; 7) Flow the enriched water sample into the pH adjustment column 26, which is filled with hydroxide-type resin to adjust the pH value of the enriched water sample to 6-7 and obtain the water sample to be analyzed; 8) Add dilute nitric acid to the water sample to be analyzed, precisely control the acidity of the water sample to be equivalent to that of 0.01 mol / L dilute nitric acid, and provide stable detection conditions for the detection unit. Then, use liquid anodic glow discharge atomic emission spectrometry to analyze and detect the water sample to be analyzed.

[0077] Before step 6), an alkaline solution should be pumped into the pH adjustment column 26 to rinse the hydroxyl resin at a flow rate of 1-5 mL / min to regenerate the hydroxyl resin; then, a buffer solution should be pumped into the pH adjustment column 26 to rinse the hydroxyl resin at a flow rate of 1-10 mL / min to remove residual cations and adjust the pH of the hydroxyl resin to 6-7.

[0078] In contrast, before step 3), an acid solution is pumped into the enrichment column 16 to rinse the chelating resin at a flow rate of 1-5 mL / min to activate and regenerate the chelating resin; then, pure water is pumped into the enrichment column 16 to rinse the chelating resin at a flow rate of 1-10 mL / min to clean and adjust the pH value of the chelating resin to 5-7.

[0079] Specifically, taking a 100 mL water sample as an example, the following steps are described for the use of the ultra-trace thallium analysis apparatus and method provided in this application:

[0080] (1) Draw 100 mL of water sample 1 from the water sample container and let it enter the pretreatment unit. The water sample first passes through filter 1, where the insoluble matter in the water sample is effectively filtered out by the microporous membrane to ensure the clarity of the water sample. Then it enters the acidification device (water sample storage container 2), where 6% nitric acid is added to the water sample through the second pump 6 to adjust the pH value of the water sample to about 1-2, which helps to separate interfering elements in the subsequent process. Finally, 1 mL of 3% bromine water is added to the water sample through the second pump 6, and the magnetic stirrer is turned on to allow the water sample to be fully mixed with nitric acid and bromine water for 5 minutes, so that the monovalent thallium in the water sample is oxidized to hypervalent thallium, thereby improving the resin's selectivity for thallium.

[0081] (2) The pretreated water sample enters the enrichment column 16 of the separation and enrichment unit. The enrichment column 16 uses Chelex-100 resin to efficiently adsorb thallium while separating other interfering elements. After enrichment is completed, 5 mL of a mixed solution of 6% nitric acid and 0.6% sulfurous acid, and 3 mL of nitric acid solution with pH=2 are added to the enrichment column 16 through the third pump 14. The elution flow rate is set to 0.5 mL / min to obtain the enriched and eluted solution.

[0082] (3) The enriched and eluted solution enters the pH adjustment column 26. The pH adjustment column 26 uses CR20 resin to reduce the acidity of the solution through ion exchange, so that the solution reaches the appropriate acidity conditions.

[0083] (4) Add 0.1 mL of 0.8 mol / L dilute nitric acid and mix it with the eluted water sample. Precisely control the acidity so that the acidity of the solution is equivalent to that of 0.01 mol / L dilute nitric acid to obtain a mixed solution.

[0084] (5) The control unit sends the mixed solution into the liquid anolyte glow discharge spectrometer of the detection unit for thallium analysis and detection. During the detection process, the instrument operates according to the set parameters (detection wavelength of 377.6 nm, hydrogen-helium flow rate of 450 mL / min, electrode spacing of 1 mm, and discharge current of 50 mA) to accurately determine the thallium content. The thallium content in water sample 1 is quantitatively obtained based on the standard curve method by reading the peak height or peak area. The results are verified with those of existing commercial inductively coupled plasma mass spectrometry, as shown in Table 1.

[0085] Table 1 shows the detection results (mean ± standard deviation, n = 3) of Tl content in actual water sample 1 using the apparatus and method of this application.

[0086]

[0087] As shown in Table 1, the detection results of 100 mL samples analyzed using the device and method described in this application are highly consistent with the ICP-MS results, confirming the reliable accuracy of the device and method. The detection limit for thallium using the device and method described in this application is reduced to 0.009 μg / L, which is lower than the national limits for thallium in industrial wastewater discharge and drinking water. This provides a reliable means for the accurate detection of trace thallium in water and lays a solid foundation for the development of solid-phase extraction coupled with liquid anodic glow discharge spectroscopy. It effectively solves the limitations of this technology in practical sample detection, broadens its application scope in environmental monitoring, and plays an important role in ensuring environmental safety and human health.

[0088] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0089] It should be noted that the above embodiments can be freely combined as needed. The above are merely preferred embodiments of this application. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A trace thallium analysis system, characterized in that, include: The pretreatment unit, separation and enrichment unit, pH adjustment unit, and detection unit are connected in sequence. The pretreatment unit is used to filter, acidify, and oxidize the water sample to be treated in order to obtain a pretreated water sample. The separation and enrichment unit is used to enrich thallium ions in the pretreated water sample and separate interfering ions; the pH adjustment unit is used to adjust the pH value of the enriched water sample to reduce the acidity of the enriched water sample and obtain the water sample to be analyzed. The detection unit is used to receive the water sample to be analyzed and to analyze and detect thallium in the water sample; The pH adjustment unit includes a pH adjustment column, which comprises a hydroxide-type resin for exchanging anions in the enriched water sample and reacting with H+ in the enriched water sample. + A neutralization reaction occurs to reduce the acidity of the enriched water sample.

2. The ultra-trace thallium analysis system according to claim 1, characterized in that, The pH adjustment unit further includes an alkaline solution supplier and a buffer solution supplier, both of which are connected to the pH adjustment column. The alkaline solution supplier supplies alkaline solution to the pH adjustment column for the regeneration of the hydroxide-type resin. The buffer solution supplier supplies buffer solution to the pH adjustment column to wash away residual cations and adjust the pH value of the pH adjustment column.

3. The ultra-trace thallium analysis system according to claim 2, characterized in that, The pH adjustment column is connected to a first inlet pipe and a first outlet pipe; The first inlet pipe is equipped with a first three-way valve at its inlet end. One port of the first three-way valve is connected to the separation and enrichment unit, and the other port of the first three-way valve is connected to the alkaline solution supplier and the buffer solution supplier. The first outlet pipe is equipped with a second three-way valve at its outlet end. One port of the second three-way valve is connected to a temporary storage bottle for storing the water sample to be analyzed, and the other port of the second three-way valve is connected to a first drain pipe for discharging waste liquid.

4. The ultra-trace thallium analysis system according to claim 3, characterized in that, The first three-way valve is connected to a first connecting pipeline, the first connecting pipeline is equipped with a first six-way valve, and the alkaline solution supplier and the buffer solution supplier are respectively connected through the first six-way valve.

5. The ultra-trace thallium analysis system according to claim 3, characterized in that, The temporary storage bottle is connected to a second connecting pipe, which is connected to the detection unit. The second connecting pipe is equipped with a first pump body, which is used to pump the water sample to be analyzed in the temporary storage bottle to the detection unit.

6. The ultra-trace thallium analysis system according to any one of claims 1-5, characterized in that, The hydroxide-type resin is a strongly basic anion exchange resin, a weakly basic anion exchange resin, or an ammonium-type resin; and the detection unit is a liquid anodic glow discharge spectrometer.

7. The ultra-trace thallium analysis system according to claim 6, characterized in that, The detection unit includes an anode tube, a cathode tube, a graphite electrode, and a DC power supply. The anode tube is connected to the pH adjustment unit. The water sample to be analyzed is prepared by adding dilute nitric acid solution and then overflowing from the anode tube. The anode tube is in contact with the graphite electrode to form a discharge anode. A carrier gas is introduced into the cathode tube to form a discharge cathode. The DC power supply applies a high-voltage current to the discharge anode and the discharge cathode to generate glow discharge micro-plasma between the discharge anode and the discharge cathode in the water sample to be analyzed.

8. The ultra-trace thallium analysis system according to any one of claims 1-5, characterized in that, The pretreatment unit includes a water sample storage container, an oxidant supplier, and an acid solution supplier. The water sample storage container is used to store the water sample to be treated. The oxidant supplier and the acid solution supplier are both connected to the water sample storage container so that the water sample to be treated is mixed with the supplied oxidant and acid solution to form a pretreated water sample.

9. The ultra-trace thallium analysis system according to claim 8, characterized in that, The separation and enrichment unit includes an enrichment column, a pure water supply device, and an eluent supply device. The water sample storage container, the acid solution supply device, the pure water supply device, and the eluent supply device are all connected to the enrichment column. The enrichment column includes a chelating resin for adsorbing thallium ions in the pretreated water sample and separating interfering ions from the pretreated water sample; an acid solution supplier supplies an acid solution to the enrichment column for activating and regenerating the chelating resin; an eluent supplier supplies an eluent to the enrichment column after the pretreated water sample enters the enrichment column to elute the thallium ions on the enrichment column and obtain the enriched water sample; and a pure water supplier supplies pure water to the enrichment column to clean the activated and regenerated chelating resin and rinse away any residual interfering ions on the enrichment column.

10. A method for ultra-trace thallium analysis, characterized in that, Including the following steps: Collect water samples to be treated; Microporous membrane filters out insoluble substances in the water sample to be treated; The water sample to be treated is mixed with an acid solution and an oxidant to carry out acidification and oxidation reactions, forming a pretreated water sample; The pretreated water sample flows into an enrichment column, which is filled with chelating resin to adsorb thallium ions and separate interfering ions. Pure water is pumped into the enrichment column to rinse away interfering ions on the enrichment column; Eluent is pumped into the enrichment column to elute thallium ions on the enrichment column and obtain a enriched water sample. The enriched water sample flows into a pH adjustment column, which is filled with hydroxide-type resin to adjust the pH value of the enriched water sample to 6-7, and obtain the water sample to be analyzed. After dilute nitric acid was added to the water sample to be analyzed, the water sample was analyzed and detected by liquid anodic glow discharge atomic emission spectrometry.

11. The ultra-trace thallium analysis method according to claim 10, characterized in that, Before the enriched water sample flows into the pH adjustment column, the following steps are included: An alkaline solution is pumped into the pH adjustment column to rinse the hydroxide-type resin at a flow rate of 1-5 mL / min, thereby regenerating the hydroxide-type resin. Buffer solution is pumped into the pH adjustment column to rinse the hydroxyl group resin at a flow rate of 1-10 mL / min to remove residual cations and adjust the pH of the hydroxyl group resin to 6-7.

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