Liquid cathode glow discharge spectrum device and method for analyzing trace thallium

Abstract

The invention discloses a liquid cathode glow discharge spectrum device and method for analyzing trace thallium. The device comprises a pretreatment unit, a separation and enrichment unit and a detection unit. The pretreatment unit is used for mixing a to-be-treated water sample with an oxidant and an acid solution to form a pretreated water sample; an enrichment column of the separation and enrichment unit comprises chelating resin, after the pretreated water sample enters the enrichment column, leacheate and an eluent are sequentially supplied to the enrichment column, and a water sample to be analyzed is obtained; and the detection unit receives the to-be-analyzed water sample for analysis and detection. According to the invention, high-selectivity chelate resin is used as an enrichment column filler, thallium ions in a pretreated water sample can be efficiently adsorbed, and other interfering ions can be separated; and after enrichment is completed, leacheate is supplied to the enrichment column, the pH environment of the enrichment column can be adjusted while interference ions are leached, and the thallium ions are effectively eluted under the assistance of a proper eluent, so that the interference problem of coexisting ions under a high-salt matrix is solved, the accuracy and sensitivity of analysis and detection are improved, and the device has the characteristics of miniaturization, low power consumption and high sensitivity.

Description

Technical Field

[0001] The present application relates to heavy metal analysis and detection, and in particular to a liquid cathode glow discharge spectroscopy device and method for analyzing trace thallium. Background Art

[0002] Thallium is a rare and highly toxic metal, with toxic effects in vivo far exceeding those of other heavy metals such as mercury, lead, chromium, and cadmium. Thallium pollution incidents pose a serious threat to ecosystem balance and human health. Although thallium is present in low concentrations in the natural environment, its strong toxicity and industrial applications have led to thallium poisoning and pollution incidents.

[0003] my country has promulgated a thallium emission limit of no more than 5 μg / L for industrial water pollution. The "Standard for Drinking Water Quality" (GB 5749-2022) and the "Environmental Quality Standard for Surface Water" (GB 3838-2002) set a thallium limit of 0.1 μg / L. Currently, the main methods for detecting thallium include spectrophotometry, electrochemistry, flame atomic absorption spectrometry, graphite furnace atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, and inductively coupled plasma mass spectrometry. Among them, spectrophotometry, flame atomic absorption spectrometry, and inductively coupled plasma atomic emission spectrometry have low sensitivity and high detection limits, which are not conducive to the determination of trace thallium; electrochemical methods have disadvantages such as many interference factors, sensitivity to electrode status, the need for regular maintenance, and the involvement of toxic elements; for graphite furnace atomic absorption spectrometry (Publication No.: CN102768191A), the addition of matrix modifiers is required, the steps are cumbersome, the analysis efficiency is low, and online monitoring is impossible; inductively coupled plasma mass spectrometry has good analytical sensitivity and fast analysis speed, but the analysis steps are cumbersome and the instrument analysis cost is high. In addition, graphite furnace atomic absorption spectrometry, inductively coupled plasma spectrometry, and mass spectrometry not only rely on high-power power supplies, consume a lot of carrier gas, and have strict requirements for the detection environment, but are also limited by the large size of the instruments, which directly restricts the application of these mature analytical techniques in field analysis and dynamic environmental monitoring.

[0004] Liquid cathode glow discharge atomic emission spectrometry (LCGDS) holds broad application prospects in field elemental analysis due to its compact size, portability, low cost, low energy consumption, operation at atmospheric pressure, and the absence of complex atomization equipment. Currently, this technique has successfully analyzed over thirty metallic elements. However, the extremely low thallium content in environmental water and the complex matrix have hindered the technique from achieving the higher requirements of real-time on-site analysis and commercialization.

[0005] Currently, the patent with publication number CN 112461814 A introduces a method for enriching trace thallium based on conventional cation exchange resin. In practical applications, especially in the detection of complex samples such as industrial wastewater, there are still certain limitations. Industrial wastewater often contains high concentrations of Na + , Ca 2+ Conventional cation exchange resins have insufficient selectivity for Tl(I), making it difficult to achieve efficient separation and enrichment of thallium in a high-salt matrix environment. Ions compete with thallium for the adsorption sites of the resin, thereby affecting the enrichment efficiency of thallium. In addition, this method requires the addition of an acid reagent mixed solution during the elution stage to ensure that the acidity of the solution is within a specific range before detection, which increases the complexity of the operation. At the same time, this operation will lead to the dilution of thallium ions in the water sample after enrichment and elution, affecting the sensitivity of trace thallium detection.

[0006] Therefore, how to improve the technical defects in the existing technology has always been a problem that ordinary technicians in this field need to solve urgently. Summary of the Invention

[0007] The purpose of this application is to provide a liquid cathode glow discharge spectroscopy device and method for analyzing trace thallium, which can solve the interference problem of coexisting ions in a high salt matrix, has the advantages of simple operation, low power consumption, low cost, and small size, and can be used for real-time online analysis of trace thallium in various environments.

[0008] The technical solutions provided by the present invention are as follows:

[0009] A liquid cathode glow discharge spectrometer for analyzing trace amounts of thallium, comprising:

[0010] Pretreatment unit, separation and enrichment unit and detection unit;

[0011] 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.

[0012] The separation and enrichment unit includes an enrichment column, an eluent supplier, and an eluent supplier. The water sample storage container, the eluent supplier, and the eluent supplier are all connected to the enrichment column. After the pretreated water sample enters the enrichment column, the eluent supplier and the eluent supplier sequentially supply eluent and eluent to the enrichment column to obtain the water sample to be analyzed. The enrichment column includes a chelating resin for adsorbing thallium ions in the pretreated water sample and separating interfering ions in the pretreated water sample.

[0013] The detection unit is used to receive a water sample to be analyzed and perform thallium analysis and detection on the water sample to be analyzed.

[0014] In some embodiments, the separation and enrichment unit further includes a pure water supplier, and the pure water supplier and the acid solution supplier are both connected to the enrichment column; the acid solution supplier is used to supply acid solution to the enrichment column for activation and regeneration of the chelating resin; the pure water supplier is used to supply pure water to the enrichment column to clean the activated and regenerated chelating resin.

[0015] In some embodiments, the enrichment column is connected to a liquid inlet pipe and a liquid outlet pipe;

[0016] The liquid inlet end of the liquid inlet pipe is provided with a six-way valve, which is connected to five first connecting pipes, and the five first connecting pipes are respectively connected to the water sample storage container, the acid solution supplier, the pure water supplier, the washing liquid supplier and the eluent supplier; and the liquid outlet end of the liquid outlet pipe is connected to a three-way pipe, which is connected to the first drain pipe and the second connecting pipe, the first drain pipe is used to discharge waste liquid, and the second connecting pipe is used to connect the detection unit.

[0017] In some embodiments, a liquid cathode glow discharge spectrometer for analyzing trace amounts of thallium further comprises:

[0018] Waste liquid collection container, used for collecting discharged waste liquid;

[0019] The first drain pipe is connected to the waste liquid collection container; and the detection unit includes a waste liquid pool and a second drain pipe, the second drain pipe is connected to the waste liquid pool and the waste liquid collection container to allow the waste liquid in the waste liquid pool to enter the waste liquid collection container.

[0020] In some embodiments, a liquid cathode glow discharge spectrometer for analyzing trace amounts of thallium further comprises:

[0021] A double-line peristaltic pump is connected to the liquid inlet pipe and the second liquid discharge pipe respectively, and is used to pump the liquid in the liquid inlet pipe to the enrichment column and pump the waste liquid in the second liquid discharge pipe to the waste liquid collection container.

[0022] In some embodiments, one of the oxidant supplier and the acid solution supplier is connected to the water sample storage container via a third connecting pipe, and the third connecting pipe is provided with a branch, which is connected to the other of the oxidant supplier and the acid solution supplier;

[0023] The third connecting pipeline is connected to a pump body, which is used to pump the oxidant and the acid solution into the water sample storage container; and a magnetic stirring rotor is provided in the water sample storage container.

[0024] In some embodiments, the pretreatment unit further includes a filter, which includes a microporous filter membrane for removing insoluble matter in the water sample to be treated; the filter is connected to the water sample storage container so that the filtered water sample to be treated enters the water sample storage container.

[0025] In some embodiments, the oxidant is bromine water with a concentration of 0.5% to 5%, the concentration of the acid solution is 2% to 10%, and the mixing ratio of the oxidant and the acid solution is 0.5% to 5% of the volume of the water sample to be treated; and / or the chelating resin is an iminodiacetic acid type resin; and / or the eluent is hydrochloric acid with a pH value of 1 to 2, and the flow rate of the eluent is 1 to 5 mL / min; and / or the eluent is a mixed solution of a nitric acid solution with a concentration of 0.5% to 5% and a sulfurous acid solution with a concentration of 0.1% to 6%, and the flow rate of the eluent is 1 to 5 mL / min.

[0026] The present application also provides a liquid cathode glow discharge spectrometer for analyzing trace amounts of thallium, comprising the steps of:

[0027] Collect water samples for treatment;

[0028] The microporous membrane filters the insoluble matter in the water sample to be treated;

[0029] The water sample to be treated is mixed with an acid solution and an oxidant to perform acidification and oxidation reactions to form a pretreated water sample;

[0030] The pretreated water sample flows into the enrichment column, which is filled with chelating resin to adsorb thallium ions and separate interfering ions;

[0031] Pump eluent into the enrichment column to flush out interfering ions on the enrichment column;

[0032] Pumping eluent into the enrichment column to elute the thallium ions on the enrichment column to obtain the water sample to be analyzed;

[0033] Liquid cathode glow discharge atomic emission spectrometry was used to analyze and detect the water samples.

[0034] In some embodiments, the concentration of the acid solution is 2% to 10%, the oxidant is bromine water with a concentration of 0.5% to 5%, the acid solution and the oxidant are mixed with the water sample to be treated at a ratio of 0.5% to 5% of the volume of the water sample to be treated, and react for 2 to 10 minutes;

[0035] The chelating resin is an iminodiacetic acid type resin;

[0036] The eluent is hydrochloric acid with a pH of 1 to 2, and the flow rate of the eluent is 1 to 5 mL / min;

[0037] The eluent is a mixed solution of a nitric acid solution with a concentration of 0.5% to 5% and a sulfurous acid solution with a concentration of 0.1% to 6%, and the flow rate of the eluent is 1 to 5 mL / min.

[0038] In some embodiments, the pretreated water sample, before flowing into the enrichment column, comprises the following steps:

[0039] Pumping acid solution into the enrichment column to flush the chelate resin at a flow rate of 1 to 5 mL / min to activate and regenerate the chelate resin;

[0040] Pump pure water into the enrichment column and flush the chelating resin at a flow rate of 1 to 10 mL / min to clean and adjust the pH value of the chelating resin to 5 to 7.

[0041] The technical effects of this application are:

[0042] 1. The application adopts a kind of liquid cathode glow discharge spectrometer for analyzing trace thallium, can realize the multiple water sample pretreatment to be measured such as surface water, industrial waste water, high salt waste water, enrichment, elution, wash-out and online detection step, thus can real-time online analysis of trace thallium in various environments.Wherein, enrichment column comprises chelate resin, and chelate resin has high selectivity, can efficiently adsorb the thallium ion in pretreatment water sample, separate other interfering ions simultaneously, and chelate resin also has good adsorption capacity to low concentration thallium, can effectively enrich trace thallium in water, guarantee the accuracy of detection.After enrichment is completed, eluent is pumped into enrichment column, when the interfering ion that elution is unnecessary, can also adjust the pH environment of chelate resin, then select suitable eluent, just can guarantee that thallium ion is effectively eluted, solve the interference problem of coexisting ions under high salt matrix, improve detection sensitivity and accuracy, have the characteristics of miniaturization, low power consumption and high sensitivity.

[0043] 2, in the application, before enrichment column feeds pre-treatment water sample, earlier feed acid solution and pure water to enrichment column successively, can activate resin and wash away impurity, improve the selectivity of resin, more help the enrichment of thallium ion.After thallium ion wash-out is finished, feed acid solution and pure water again, can realize the activation regeneration of resin, make it recover adsorption property again, be fully prepared for next separation and enrichment, help this long-time repeated use of the liquid cathode glow discharge spectroscopic device that is used to analyze trace thallium, strong practicality.

[0044] 3. In this application, the liquid inlet pipe of the enrichment column is connected to a six-way valve, and the other five interfaces of the six-way valve are respectively connected to the water sample storage container, acid solution supplier, pure water supplier, eluent supplier and eluent supplier. In this way, by switching the six-way valve, the acid solution, pure water, pretreated water sample, eluent and eluent can be delivered in sequence, avoiding bubble interference caused by mixing of eluent and eluent, and further ensuring the accuracy of the detection.

[0045] 4. In this application, the chelating resin adopts iminodiacetic acid type resin, which has a good enrichment effect on high concentration (μg / L) and low concentration (ng / L) of thallium ions, and after the acid solution is mixed with the water sample to be treated, it can be acidified to pH=1-2. Within this range, the iminodiacetic acid type chelating resin has a good effect on K + 、Na+ , Ca 2+ Mg 2+ In addition, the oxidant used in this application is bromine water, which has stronger oxidizing properties under acidic conditions and can oxidize Tl(I) in the water sample to Tl(III), further improving the selective adsorption capacity of the iminodiacetic acid chelating resin for thallium ions.

[0046] 5. In this application, the eluent is hydrochloric acid with a pH of 1 to 2. The Cl- in the hydrochloric acid reacts with Tl 3+ Can form stable [TlX4] - Complex anions, and the iminodiacetic acid type chelating resin can be used as an anion resin in an environment of pH = 1, making it difficult for thallium ions to be eluted, while effectively washing other matrix ions, further improving the selectivity of the iminodiacetic acid type chelating resin for thallium ions. The eluent uses a mixed solution of nitric acid and sulfurous acid, in which the reducing effect of sulfurous acid can convert Tl(Ⅲ) into Tl(Ⅰ), weakening the complexing effect between thallium ions and the iminodiacetic acid type chelating resin, thereby significantly improving the elution efficiency. This application solves the interference problem of coexisting ions under high salt matrix through the triple synergistic mechanism of resin selective adsorption, eluent pH control and eluent reduction effect, breaking through the bottleneck of insufficient sensitivity of traditional spectral technology, and filling the technical gap in on-site rapid detection of trace thallium. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0048] Figure 1 This is a schematic structural diagram of a liquid cathode glow discharge spectrometer for analyzing trace amounts of thallium provided in one embodiment of the present application;

[0049] Figure 2 This is a comparison chart of characteristic spectra of 50 mL of 50 μg / L thallium element containing 0.5% salt detected by using a liquid cathode glow discharge spectroscopic apparatus and method for analyzing trace thallium provided by the present application, and 50 mL of 50 μg / L thallium standard solution detected without using the liquid cathode glow discharge spectroscopic apparatus and method for analyzing trace thallium provided by the present application;

[0050] Figure 3 This is a timing diagram of detecting 50 mL of 50 μg / L thallium containing 0.5% salt using a liquid cathode glow discharge spectrometer and method for analyzing trace thallium provided by the present application;

[0051] Figure 4 The present invention provides a timing diagram of detecting 50 mL of laboratory waste liquid and three sets of parallel data using a liquid cathode glow discharge spectrometer and method for analyzing trace thallium provided by the present application.

[0052] Reference numerals:

[0053] 1. Filter; 2. Water sample storage container; 3. Magnetic stirring rotor; 4. Third connecting pipeline; 41. Branch; 5. Pump body; 6. Oxidant supplier; 7. Acid solution supplier; 8. Pure water supplier; 9. Eluent supplier; 10. Eluent supplier; 11. Six-way valve; 12. First connecting pipeline; 13. Liquid inlet pipe; 14. Dual-line peristaltic pump; 15. Enrichment column; 16. Liquid outlet pipe; 17. Tee pipe; 18. First drain pipe; 19. Second connecting pipeline; 20. Waste liquid collection container; 21. Waste liquid tank; 22. Cathode tube; 23. Graphite electrode; 24. Ballast resistor; 25. DC power supply; 26. Anode tungsten rod; 27. Second drain pipe; 28. Focusing lens; 29. Optical fiber; 30. Spectrometer; 31. Computer. DETAILED DESCRIPTION

[0054] In the following description, specific details such as specific system structures and technologies are provided for illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid obstructing the description of the present application with unnecessary details.

[0055] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the specific implementation methods of the present application will be described below with reference to the accompanying drawings. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without inventive work.

[0056] To simplify the drawings, only the parts relevant to this application are schematically shown in each figure. They do not represent the actual structure of the product. In addition, to simplify the drawings and facilitate understanding, in some figures, only one of the components with the same structure or function is schematically depicted or labeled. In this document, "one" not only means "only one" but also "more than one."

[0057] It should be further understood that the term "and / or" used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0058] It should be noted that, unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they can refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0059] In the embodiments shown in the accompanying drawings, directional indications (such as up, down, left, right, front, and back) are used to explain the structure and movement of various components of the present application, not absolute but relative. These descriptions are applicable when these components are in the positions shown in the accompanying drawings. If the descriptions of the positions of these components are changed, these directional indications will also change accordingly.

[0060] In addition, in the description of the present application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0061] Liquid cathode glow discharge atomic emission spectrometry (SCGD-AES) is an emerging detection technology that can be used to directly detect thallium in water samples without the need for complex sample pretreatment. Currently, the patent with publication number CN 112461814 A introduces a trace thallium enrichment method based on conventional cation exchange resin, but in practical applications, especially in the detection of complex samples such as industrial wastewater, there are still certain limitations. For example, industrial wastewater often contains high concentrations of Na + , Ca 2 + and other coexisting cations. According to our previous research data, when coexisting ions (such as Na + With K + When the concentration of thallium (I) reaches 400 mg / L, the recovery rate of thallium directly detected by liquid cathode glow discharge atomic emission spectrometry drops significantly to 56%. This method itself is subject to interference from high-salt matrix, and conventional cation exchange resins lack selectivity for Tl(I), making it difficult to achieve efficient separation and enrichment of thallium in a high-salt matrix environment. Coexisting cations compete with thallium for resin adsorption sites, resulting in the concentration of the high-salt matrix after elution, ultimately amplifying the matrix effect of the detection system and reducing analytical accuracy.

[0062] In this regard, the present application discloses a liquid cathode glow discharge spectroscopy device and method for analyzing trace thallium. Based on the combination of solid phase extraction and liquid cathode glow discharge spectroscopy, it can solve the interference problem of coexisting ions in a high salt matrix. It has the advantages of simple operation, low power consumption, low cost, and small size, and can perform real-time online analysis of trace thallium in various environmental water samples.

[0063] Specifically, see Figure 1 The liquid cathode glow discharge spectrometer for analyzing trace thallium includes a pretreatment unit, a separation and enrichment unit, and a detection unit. The pretreatment unit is used to filter, acidify, and oxidize the water sample to be treated, and includes a water sample storage container 2, an oxidant supplier 6, and an acid solution supplier 7. The water sample storage container 2 is used to store the water sample to be treated, and the oxidant supplier 6 and the acid solution supplier 7 are connected to the water sample storage container 2, and can transport the oxidant and acid solution to the water sample storage container 2 to mix with the water sample to be treated to form a pretreated water sample. The separation and enrichment unit is used to enrich thallium ions in the pretreated water sample and separate interfering ions, and includes an enrichment column 15, a washing liquid supplier 9, and an eluent supplier 10. The water sample storage container 2, eluent supply 9, and eluent supply 10 are all connected to an enrichment column 15. After the pretreated water sample enters the enrichment column 15, the eluent supply 9 and eluent supply 10 sequentially supply eluent and eluent to the enrichment column 15 to obtain the water sample to be analyzed. The enrichment column 15 includes a chelating resin for adsorbing thallium ions in the pretreated water sample and separating interfering ions in the pretreated water sample. The detection unit is used to receive the water sample to be analyzed and perform thallium analysis on the water sample to be analyzed.

[0064] The present embodiment is by arranging pre-treatment unit, separation and enrichment unit and detection unit, realized water sample pre-treatment, enrichment, drip washing, wash-out and online detection step, especially in the enrichment step, adopt highly selective chelating resin as filler, energy-efficiently adsorb the thallium ion in the pre-treatment water sample, separate other interfering ions simultaneously, weaken the influence of interfering ion on thallium ion selective adsorption under the high salt matrix environment, improve the accuracy of detection, thereby meet field detection and environmental dynamic monitoring demand.And chelating resin also has good adsorptive capacity to low concentration thallium, can effectively enrich trace thallium [trace thallium exists with microgram every liter (μ g / L) or lower concentration conventionally] in the water sample, help the trace thallium in the various environments of real-time online analysis, have a wide range of applications, have filled up the technical gap of trace thallium on-site rapid detection.

[0065] As a preferred chelating resin, iminodiacetic acid type resin can be used, with Chelex-100 resin and D401 resin being preferred, which have good enrichment effects on high concentration (μg / L) and low concentration (ng / L) of thallium. Considering that iminodiacetic acid type resin has a low enrichment effect on K + 、Na + , Ca 2+ Mg 2+ Common matrix ions such as thallium are basically not adsorbed. When the water sample is acidified by a mixed acid solution, it is preferably acidified to pH = 1-2, so as to further improve the selective adsorption of thallium ions by the enrichment column 15, wherein the acid solution is preferably nitric acid solution or hydrochloric acid solution.

[0066] In addition, this embodiment also includes an oxidizing agent to oxidize the water sample, thereby converting Tl(I) in the treated water sample to Tl(III). This further facilitates the selective adsorption of thallium ions by the iminodiacetic acid resin. The addition of the acid solution acidifies the water sample to a pH of 1-2. Bromine water is preferably used as the oxidizing agent, as bromine water has stronger oxidizing properties under acidic conditions and more readily oxidizes Tl(I) in the treated water sample to Tl(III).

[0067] Specifically, the concentration of bromine water supplied by the oxidant supplier 6 is 0.5% to 5% bromine water, and the concentration of acid solution supplied by the acid solution supplier 7 is 2% to 10%. Bromine water and acid solution are added to the water sample to be treated at 0.5% to 5% of the volume of the water sample to be treated, and the ratio of the added bromine water to the added acid solution is 1:1. The water sample to be treated, bromine water and acid solution are stirred and mixed for 2 to 10 minutes to obtain the above-mentioned pretreated water sample.

[0068] In this embodiment, one of the oxidant supplier 6 and the acid solution supplier 7 is connected to the water sample storage container 2 via a third connecting line 4. This third connecting line 4 is provided with a branch line 41 that connects to the other of the oxidant supplier 6 and the acid solution supplier 7. A pump 5 is connected to the third connecting line 4. This pump 5 is preferably a micro peristaltic pump that can automatically pump bromine water and an acid solution into the water sample storage container 2, for example, at a ratio of 1% of the volume of the water sample to be processed, with a 1:1 ratio of bromine water to acid solution. Furthermore, a magnetic stirring rotor 3 is provided within the water sample storage container 2, enabling automated stirring of the water sample to be processed, the bromine water, and the acid solution, resulting in a high degree of automation.

[0069] Specifically, the pretreatment unit also includes a filter 1, which includes a microporous filter membrane that can remove insoluble matter from the water sample to be treated as it flows through. The filter 1 is connected to a water sample storage container 2, so that the filtered water sample to be treated can enter the water sample storage container 2 for subsequent mixing reactions.

[0070] In an exemplary embodiment, the eluent supplied by the eluent supply device is hydrochloric acid with a pH value of 1 to 2, and the interfering ions are eluted at a flow rate of 1 to 5 mL / min, so that the pH environment of the iminodiacetic acid type resin can be maintained at about 1. On the one hand, the iminodiacetic acid type resin has a low pH value of K + 、Na + , Ca 2+ Mg 2+ Common matrix ions such as HCl are basically not adsorbed, which is more conducive to the elution of interfering ions; on the other hand, Cl- and Tl 3+ Can form stable [TlX4] -The complex anion, and the iminodiacetic acid type resin can be used as an anion resin under this pH environment, making it difficult for thallium ions to be eluted; in addition, it can also ensure that the thallium ions are in a normal ignition state after being eluted by the eluent and entering the detection unit.

[0071] In contrast, the eluent supplied by the eluent supply 10 is a mixture of a 0.5% to 5% nitric acid solution and a 0.1% to 6% sulfurous acid solution, and is used to elute the thallium ions at a flow rate of 1 to 5 mL / min. The reducing effect of the sulfurous acid solution converts Tl(III) into Tl(I), thereby weakening the complexation between the thallium ions and the iminodiacetic acid resin, thereby significantly improving the elution efficiency to over 95%.

[0072] This embodiment solves the interference problem of coexisting ions in a high-salt matrix through the triple synergistic mechanism of resin selective adsorption, eluent pH control, and eluent reduction, breaking through the bottleneck of insufficient sensitivity of traditional spectroscopy technology. Moreover, the entire process does not require complex pretreatment or additional acidity adjustment, and the single detection time is ≤20 minutes, which significantly improves the analysis efficiency. It provides reliable technical support for environmental monitoring, industrial wastewater control, and emergency detection of sudden thallium pollution incidents, filling the technical gap in on-site rapid detection of trace thallium.

[0073] Particularly, the separation and enrichment unit also comprises a pure water feeder 8, and the pure water feeder 8 and the acid solution feeder 7 are all connected with the enrichment column 15.Like this, before enrichment column 15 feeds the pre-treated water sample to carry out separation and enrichment, can earlier be supplied with acid solution by the acid solution feeder 7 to enrichment column 15, iminodiacetic acid type resin is activated, then supply pure water to enrichment column 15 by the pure water feeder 8 and clean impurity, can effectively improve the selectivity of iminodiacetic acid type resin, more help the enrichment of thallium ion.And, after the thallium ion wash-out is finished, also can feed acid solution and pure water again, can realize the activation regeneration of resin, make it recover adsorption property again, for separation and enrichment next time is fully prepared, help this long-time repeated use of the liquid cathode glow discharge spectrometer that is used to analyze trace thallium, and practicality is strong.

[0074] Furthermore, the enrichment column 15 is connected to a liquid inlet pipe 13 and a liquid outlet pipe 16. The liquid inlet end of the liquid inlet pipe 13 is provided with a six-way valve 11, and the other five interfaces of the six-way valve 11 are respectively connected to five first connecting pipes 12, and the five first connecting pipes 12 are respectively connected to the water sample storage container 2, the acid solution supplier 7, the pure water supplier 8, the eluent supplier 9 and the eluent supplier 10. In this way, by switching the six-way valve, the acid solution, pure water, pretreated water sample, eluent and eluent can be transported in sequence, avoiding the mixing of eluent and eluent to cause bubble interference, further ensuring the accuracy of the detection. Relatively speaking, the liquid outlet end of the liquid outlet pipe 16 is connected to a three-way pipe 17, and the other two interfaces of the three-way pipe 17 are respectively connected to a first drain pipe 18 and a second connecting pipe 19, the first drain pipe 18 is used to discharge waste liquid, and the second connecting pipe 19 is used to connect the detection unit.

[0075] The liquid inlet pipe 13 of the enrichment column 15 is preferably provided with a peristaltic pump, which can pump the liquid (any of an acid solution, pure water, a pretreated water sample, a washing solution, and an eluent) in the liquid inlet pipe 13 to the enrichment column 15, thereby achieving automatic liquid delivery and further improving the automation level of the liquid cathode glow discharge spectrometer for analyzing trace thallium. In addition, the liquid cathode glow discharge spectrometer for analyzing trace thallium may also include a waste liquid collection container 20 for collecting waste liquid discharged from the first liquid discharge pipe 18 to reduce its environmental pollution.

[0076] In one exemplary embodiment, the detection unit employs a liquid cathode glow discharge spectrometer, comprising an excitation source, a spectrometer 30, and a computer 31. The detection unit also includes a cathode tube 22, an anode tungsten rod 26, a DC power supply 25, a ballast resistor 24, a graphite electrode 23, a waste liquid reservoir 21, and a second drain pipe 27. The DC power supply 25 is a high-voltage power supply capable of providing a DC voltage of 0 to 1500V and a DC current of 0 to 200mA. The positive electrode of the DC power supply 25 is connected to the anode tungsten rod 26, while the negative electrode of the DC power supply 25 is connected to the ballast resistor 24 and the graphite electrode 23. The anode tungsten rod 26 is fixed to a one-dimensional platform that can be raised and lowered in the Y direction to control ignition. The waste liquid reservoir 21 is located below the tungsten rod 26, and a second drain pipe 27 is connected to the bottom of the waste liquid reservoir 21 to allow for the removal of waste liquid. A graphite electrode 23 is transversely positioned through the sidewall of the waste liquid reservoir 21 and fixed to one side of the reservoir. A cathode tube 22 extends through the bottom of the waste liquid reservoir 21 and the graphite electrode 23, positioned below the tungsten rod 26. This allows the water sample to enter the excitation source through the cathode tube 22, where the thallium ions within the sample are excited by the excitation source to produce a plasma light source. A spectrometer 30 acquires the light source signal from the plasma light source and transmits it to a computer 31, which then outputs a corresponding timing diagram.

[0077] Specifically, the detection unit further comprises a three-dimensional platform, a focusing lens 28, and an optical fiber 29. The focusing lens 28 is used to focus the plasma light source generated by thallium ion excitation. The optical fiber 29 is fixed to the three-dimensional platform and electrically connected to the spectrometer 30. It collects the focused light source, converts it into a light source signal, and transmits it to the spectrometer 30 in the form of an electrical signal. The three-dimensional platform has an adjustable accuracy of 2μm in the X, Y, and Z axes. This allows the optical path position of the optical fiber 29 to be adjusted so that the spectrometer 30 obtains the strongest spectral signal, thereby more accurately analyzing and detecting results.

[0078] In this embodiment, one end of the second liquid discharge pipe 27 away from the waste liquid pool 21 can be connected to the waste liquid collection container 20, reducing the pollution to the environment caused by the liquid cathode glow discharge spectrometer used to analyze trace thallium. In addition, the peristaltic pump on the liquid inlet pipe 13 can adopt a dual-line peristaltic pump 14, which can be connected to the liquid inlet pipe 13 and the second liquid discharge pipe 27 respectively. It can not only pump the liquid in the liquid inlet pipe 13 to the enrichment column 15, but also pump the waste liquid in the second liquid discharge pipe 27 to the waste liquid collection container 20. The structure is highly compact and practical, which is more conducive to the miniaturization of the liquid cathode glow discharge spectrometer used to analyze trace thallium.

[0079] Preferably, the liquid cathode glow discharge spectrometer for analyzing trace thallium also includes a control unit, which is respectively connected to the separation and enrichment unit and the detection unit, and can control the operation of each unit, including setting and adjusting processing parameters, controlling the elution process, and starting detection, thereby realizing full process automation from enrichment, elution to detection, and the single detection time is ≤20 minutes, which significantly improves the analysis efficiency and provides reliable technical support for environmental monitoring, industrial wastewater control and emergency detection of sudden thallium pollution incidents. It has the characteristics of miniaturization, low power consumption and high sensitivity, and is not affected by complex matrix interference. It can meet the needs of field on-site detection and dynamic environmental monitoring, and has significant social benefits and promotion value.

[0080] The present application also provides a liquid cathode glow discharge spectroscopic method for analyzing trace thallium, comprising the following steps: 1) collecting a water sample to be processed; 2) filtering insoluble matter in the water sample to be processed through a microporous filter membrane; 3) mixing an acid solution and an oxidant with the water sample to be processed to undergo acidification and oxidation reactions to form a pretreated water sample; 4) allowing the pretreated water sample to flow into an enrichment column 15, which is filled with a chelating resin to adsorb thallium ions and separate interfering ions; 5) pumping eluent into the enrichment column 15 to rinse away interfering ions on the enrichment column 15; 6) pumping an eluent into the enrichment column 15 to elute the thallium ions on the enrichment column 15 to obtain the water sample to be analyzed; and 7) analyzing and detecting the water sample to be analyzed using liquid cathode glow discharge atomic emission spectrometry.

[0081] The acid solution used in step 1) is preferably a nitric acid solution or a hydrochloric acid solution with a concentration of 2% to 10%, and the oxidant is preferably a bromine water with a concentration of 0.5% to 5%, which is added in a ratio of 1:1 to the volume of the water sample to be treated, and stirred for 2 to 10 minutes. The chelating resin in step 4) is an iminodiacetic acid type resin, which can selectively adsorb thallium ions with an adsorption efficiency of more than 95%. The eluent in step 5) is hydrochloric acid with a pH value of 1 to 2 and is eluted at a flow rate of 1 to 5 mL / min, which forms a stable [TlX4] - The complexed anion strengthens the selective retention of thallium by the chelating resin. The eluent in step 6) is a mixed solution of a nitric acid solution with a concentration of 0.5% to 5% and a sulfurous acid solution with a concentration of 0.1% to 6%, and is eluted at a flow rate of 1 to 5 mL / min. It can convert Tl(III) into Tl(I) through reduction, weakening the complexation between thallium ions and the chelating resin, thereby significantly improving the elution efficiency. During the elution process, H + Changes in concentration can cause fluctuations in the discharge current of the liquid cathode glow discharge, which in turn affects the intensity of the elemental signal. Therefore, in step 7), the liquid cathode glow discharge spectrometer preferably uses constant current mode to effectively reduce interference caused by differences in discharge current, thereby ensuring detection stability and accuracy. This method does not require additional adjustment of electrolyte acidity, simplifies the operating process, and enables rapid online detection of trace thallium.

[0082] Furthermore, in step 7), the detection wavelength of the liquid cathode glow discharge spectrometer is 377 nm, the electrode spacing is 2 to 5 mm, and the current is greater than or equal to 40 to 80 mA.

[0083] Furthermore, before step 4), it is necessary to first pump an acid solution into the enrichment column 15 and rinse the chelate resin at a flow rate of 1 to 5 mL / min to activate and regenerate the chelate resin; subsequently, pure water is pumped into the enrichment column 15 and rinse the chelate resin at a flow rate of 1 to 10 mL / min to clean and adjust the pH value of the chelate resin to 5 to 7.

[0084] Specifically, taking a simulated wastewater sample containing 0.5% salt as an example, a liquid cathode glow discharge spectrometer and method for analyzing trace thallium provided by the present application are described, including the following steps:

[0085] Resin activation and regeneration: Using a dual-line peristaltic pump 14 and a six-way valve, control the acid solution supplier 7 with a concentration of 5% acid and the pure water in the pure water supplier 8 to flush the resin at a flow rate of 5 mL / min, respectively, for 2 minutes, thereby converting the resin into H-type, fully preparing for the subsequent separation and enrichment steps.

[0086] Water sample pretreatment: 50 mL of simulated wastewater sample (containing 0.5% salt) was first filtered through a microporous membrane to remove insoluble matter. 0.5 mL of a 5% acid solution and 0.5 mL of 3% bromine water were then added to the filtered sample. A magnetic stirrer was then activated to allow the sample, acid, and bromine water to mix thoroughly for 5 minutes. This step acidifies the sample to a pH of 1-2 by adding the acid solution. Simultaneously, the bromine water oxidizes the monovalent thallium in the sample into higher-valent thallium, thereby enhancing the resin's selective adsorption capacity for thallium. This results in a pretreated water sample.

[0087] Separation and enrichment: The pretreated water sample enters the enrichment column 15 of the separation and enrichment unit through a dual-line peristaltic pump 14 and a six-way valve. The waste liquid flows directly out of the first drain pipe 18 at the lower end of the three-way valve. The resin uses iminodiacetic acid type Chelex-100 resin, which efficiently adsorbs thallium and simultaneously separates other interfering elements. When the enrichment is completed, the six-way valve is switched to the eluent. The dual-line peristaltic pump 14 controls the pumping of hydrochloric acid eluent with a pH of 1 into the enrichment column 15. The eluent flow rate is set to 2.0 mL / min. After 90 seconds of elution, the control unit controls the lower outlet of the three-way valve to close and the right outlet to open. The eluent flows into the detection unit through the second connecting pipe 19. The control unit controls the raising and lowering of the tungsten rod 26 for ignition, and the plasma is stabilized for 30 seconds.

[0088] Elution: After the plasma stabilizes for 30 seconds, the six-way valve is switched to the eluent, and the dual-line peristaltic pump 14 controls the pumping of a mixed eluent of 1% nitric acid solution and 1.2% sulfurous acid into the enrichment column 15 to elute the target thallium element. The elution flow rate is set to 2.0 mL / min.

[0089] Analysis and detection: The eluted solution flows into the detection unit from the right outlet of the three-way valve for thallium analysis and detection. During the detection process, the detection instrument (liquid cathode glow discharge spectrometer) works according to the set parameters (detection wavelength of 377nm, electrode spacing of 3.5mm, current of 55mA, constant current mode) to accurately measure the thallium content. The peak height or peak area reading is used to quantitatively obtain the thallium ion content in the simulated wastewater sample based on the standard curve method. The results are as follows: Figure 2 、 Figure 3 As shown in Table 1, even if the simulated wastewater sample contains 0.5% salt, the recovery rate can still reach more than 80%.

[0090] Table 1 Test results of simulated wastewater samples, laboratory wastewater and standard reference material GBW07405

[0091]

[0092] See also Figure 2, which is a comparison chart of the characteristic spectra of a simulated wastewater sample detected by a liquid cathode glow discharge spectroscopic apparatus and method for analyzing trace thallium provided by the present application, and a 50mL 50μg / L thallium standard solution detected without using the liquid cathode glow discharge spectroscopic apparatus and method for analyzing trace thallium provided by the present application. It can be seen that when the simulated wastewater sample is not detected using the device and method provided by the present application, the liquid cathode glow discharge plasma is directly used, which is extremely unstable and no obvious signal is detected. After using the device and method provided by the present application, an obvious characteristic spectrum line appears at 377.6nm, and the signal intensity is increased by at least 22 times compared with the characteristic spectrum line of the 50μg / L thallium standard solution without using the device and method of the present invention. Therefore, the present application greatly reduces the detection limit of high-salt simulated wastewater, successfully reducing it to 0.23μg / L. When the water sample volume was further increased to 100 mL, the detection limit was reduced to 0.096 μg / L, which is lower than the national water quality standard limit (0.1 μg / L). This fully demonstrates the excellent ability of this application to improve the detection accuracy in trace thallium detection and the high sensitivity detection performance for lower thallium content elements, which strongly proves the great advantages and application value of the present invention in the detection of complex water samples.

[0093] Then the test was carried out with laboratory waste liquid (including laboratory waste liquid spiked with 10ug / L, which can be used to evaluate the accuracy and reliability of the analytical method). The results are as follows Figure 4 As shown in Table 1, this method demonstrates good accuracy and parallelism, making it suitable for the detection of trace thallium in complex environments. Furthermore, the standard substance GBW07405 (digested and diluted 483 times) was also tested, as shown in Table 1.

[0094] GBW07405, a reference material commonly used in geological surveys and environmental analysis, is suitable for a variety of analytical methods and quality control scenarios. Testing with this material further validated the accuracy of the analytical device and method provided in this application, expanding the application of liquid cathode glow discharge spectrometers for trace thallium analysis in real-world samples. For ultra-trace thallium analysis, the enrichment factor can be increased by increasing the water sample volume to meet detection requirements.

[0095] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0096] It should be noted that the above embodiments can be freely combined as needed. The above are only preferred implementations of the present application. It should be noted that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application, and these improvements and modifications should also be considered as the scope of protection of the present application.

Claims

1. A liquid cathode glow discharge spectrometer for analyzing trace amounts of thallium, characterized in that: include: Pretreatment unit, separation and enrichment unit and detection unit; 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. The separation and enrichment unit includes an enrichment column, an eluent supplier, and an eluent supplier. The water sample storage container, the eluent supplier, and the eluent supplier are all connected to the enrichment column. After the pretreated water sample enters the enrichment column, the eluent supplier and the eluent supplier sequentially supply eluent and eluent to the enrichment column to obtain the water sample to be analyzed; wherein the enrichment column includes a chelating resin for adsorbing thallium ions in the pretreated water sample and separating interfering ions in the pretreated water sample; The detection unit is used to receive the water sample to be analyzed and perform thallium analysis and detection on the water sample to be analyzed.

2. A liquid cathode glow discharge spectrometer for analyzing trace thallium according to claim 1, characterized in that: The separation and enrichment unit also includes a pure water supplier, and the pure water supplier and the acid solution supplier are both connected to the enrichment column; the acid solution supplier is used to supply acid solution to the enrichment column for activation and regeneration of the chelate resin; the pure water supplier is used to supply pure water to the enrichment column to clean the activated and regenerated chelate resin.

3. The liquid cathode glow discharge spectrometer for analyzing trace thallium according to claim 2, characterized in that: The enrichment column is connected to a liquid inlet pipe and a liquid outlet pipe; The liquid inlet end of the liquid inlet pipe is provided with a six-way valve, and the six-way valve is connected to five first connecting pipes, and the five first connecting pipes are respectively connected to the water sample storage container, the acid solution supplier, the pure water supplier, the washing liquid supplier and the eluent supplier; and the liquid outlet end of the liquid outlet pipe is connected to a three-way pipe, and the three-way pipe is connected to a first drain pipe and a second connecting pipe, the first drain pipe is used to discharge waste liquid, and the second connecting pipe is used to connect the detection unit.

4. The liquid cathode glow discharge spectrometer for analyzing trace thallium according to claim 3, characterized in that: Also includes: Waste liquid collection container, used for collecting discharged waste liquid; The first drain pipe is connected to the waste liquid collection container; and the detection unit includes a waste liquid pool and a second drain pipe, the second drain pipe is connected to the waste liquid pool and the waste liquid collection container to allow the waste liquid in the waste liquid pool to enter the waste liquid collection container.

5. The liquid cathode glow discharge spectrometer for analyzing trace thallium according to claim 4, characterized in that: Also includes: A double-line peristaltic pump is connected to the liquid inlet pipe and the second liquid discharge pipe respectively, and is used to pump the liquid in the liquid inlet pipe to the enrichment column and pump the waste liquid in the second liquid discharge pipe to the waste liquid collection container.

6. A liquid cathode glow discharge spectrometer for analyzing trace thallium according to any one of claims 1 to 5, characterized in that: One of the oxidant supplier and the acid solution supplier is connected to the water sample storage container via a third connecting pipe, and the third connecting pipe is provided with a branch, and the branch is connected to the other of the oxidant supplier and the acid solution supplier; The third connecting pipeline is connected to a pump body, and the pump body is used to pump the oxidant and the acid solution into the water sample storage container; and a magnetic stirring rotor is provided in the water sample storage container.

7. A liquid cathode glow discharge spectrometer for analyzing trace thallium according to any one of claims 1 to 5, characterized in that: The pretreatment unit further comprises a filter, wherein the filter comprises a microporous filter membrane for removing insoluble matter in the water sample to be treated; The filter is connected to the water sample storage container so that the filtered water sample to be processed enters the water sample storage container.

8. A liquid cathode glow discharge spectrometer for analyzing trace thallium according to any one of claims 1 to 5, characterized in that: The oxidant is bromine water with a concentration of 0.5% to 5%, the concentration of the acid solution is 2% to 10%, and the mixing ratio of the oxidant and the acid solution is 0.5% to 5% of the volume of the water sample to be treated; and / or the chelating resin is an iminodiacetic acid type resin; and / or the eluent is hydrochloric acid with a pH value of 1 to 2, and the flow rate of the eluent is 1 to 5 mL / min; and / or the eluent is a mixed solution of a nitric acid solution with a concentration of 0.5% to 5% and a sulfurous acid solution with a concentration of 0.1% to 6%, and the flow rate of the eluent is 1 to 5 mL / min.

9. A liquid cathode glow discharge spectroscopic method for analyzing trace amounts of thallium, characterized in that: Including steps: Collect water samples for treatment; filtering insoluble matter in the water sample to be processed through a microporous filter membrane; The water sample to be treated is mixed with an acid solution and an oxidant to undergo acidification and oxidation reactions to form a pretreated water sample; The pretreated water sample flows into an enrichment column, which is filled with a chelating resin to adsorb thallium ions and separate interfering ions; Pumping eluent into the enrichment column to flush out interfering ions on the enrichment column; Pumping an eluent into the enrichment column to elute the thallium ions on the enrichment column to obtain a water sample to be analyzed; Liquid cathode glow discharge atomic emission spectrometry was used to analyze and detect the water samples.

10. The liquid cathode glow discharge spectroscopic method for analyzing trace thallium according to claim 9, characterized in that: The concentration of the acid solution is 2% to 10%, and the oxidant is bromine water with a concentration of 0.5% to 5%. The acid solution and the oxidant are mixed with the water sample to be treated at a ratio of 0.5% to 5% of the volume of the water sample to be treated, and react for 2 to 10 minutes; The chelating resin is an iminodiacetic acid type resin; The eluent is hydrochloric acid with a pH value of 1 to 2, and the flow rate of the eluent is 1 to 5 mL / min; The eluent is a mixed solution of a nitric acid solution with a concentration of 0.5% to 5% and a sulfurous acid solution with a concentration of 0.1% to 6%, and the flow rate of the eluent is 1 to 5 mL / min.

11. The liquid cathode glow discharge spectroscopic method for analyzing trace thallium according to claim 9, characterized in that: Before the pretreated water sample flows into the enrichment column, the steps include: Pumping an acid solution into the enrichment column to flush the chelate resin at a flow rate of 1 to 5 mL / min to activate and regenerate the chelate resin; Pure water is pumped into the enrichment column to flush the chelate resin at a flow rate of 1 to 10 mL / min to clean and adjust the pH value of the chelate resin to 5 to 7.

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