Method and device for simultaneously testing trace mercury and arsenic in water body through mass spectrometry

Abstract

The invention relates to the field of physical and chemical analysis of chemical substances, in particular to a method and a device for simultaneously testing trace mercury and arsenic in a water body through mass spectrometry. The method comprises the following steps: introducing hydrogen into a water body sample to obtain gas a; introducing the gas a into an enrichment device; and introducing carrier gas into the enrichment device, heating, continuously introducing the gas b discharged from the enrichment device into an atomizing chamber of the inductively coupled plasma mass spectrometer by using the carrier gas, or directly introducing the gas a into the atomizing chamber by using the carrier gas. According to the invention, hydrogen reacts with mercury and arsenic elements in a water sample to generate elemental mercury and arsenic hydride, so that the interference of a sample substrate on the test is avoided, and meanwhile, salt in the sample is prevented from being deposited in the interception cone and the atomization chamber in the atomization process, so that the replacement frequency of key parts is reduced, the equipment operation cost is reduced, and the test efficiency is improved. And the accuracy of a test result is improved.

Description

Technical Field

[0001] This invention relates to the field of physicochemical analysis of chemical substances, and specifically to a method and apparatus for simultaneously testing trace amounts of mercury and arsenic in water using mass spectrometry. Background Technology

[0002] With the development of environmental science, biomedicine, and other disciplines, our understanding of the bioavailability, toxicity, chemical activity, and re-migration of heavy metal elements has become increasingly profound. Mercury and arsenic, as two important heavy metal elements, pose a serious threat to the environment and the health of organisms. In particular, mercury and arsenic in seawater are typical highly toxic trace elements, which can exist in multiple valence states and organic / inorganic forms, and are prone to migration and transformation within complex matrix structures, directly affecting their bioavailability and ecotoxicity. Accurate analysis of the content and forms of mercury and arsenic in seawater is not only the scientific basis for assessing the safety and health risks of marine ecosystems, but also an important prerequisite for understanding geochemical cycles, pollution source apportionment, and cross-media migration patterns.

[0003] Mercury is a typical highly toxic trace element, existing in the environment in the forms of elemental mercury, inorganic mercury, and organic mercury. Methylmercury, in particular, accumulates through the food chain and poses a significant threat to the human nervous system. Due to the extremely low concentration and complex forms of mercury in nature, accurate analysis has long faced the dual challenges of sensitivity and matrix interference. Existing detection methods include: Cold Atomic Absorption Spectrophotometry for the Determination of Mercury in Water (HJ 597-2011), Cold Atomic Fluorescence Spectrophotometry for the Determination of Mercury in Water (HJ 543-2009), and Cold Atomic Absorption Spectrophotometry for the Determination of Total Mercury in Ambient Air (HJ 910-2017), providing standard methods for the detection of trace mercury in water and the atmosphere. While cold atomic absorption and cold atomic fluorescence methods offer high sensitivity, they are still affected by matrix effects in high-salt environments such as seawater, leading to inaccurate detection. High concentrations of salts such as sodium chloride in seawater severely interfere with the signal stability of cold atomic absorption / fluorescence methods, causing baseline drift, decreased sensitivity, and even inaccurate quantification.

[0004] Arsenic is an important environmental pollutant, and its toxicity, migration, transformation, and speciation are closely related. As(III) is the most toxic, followed by As(V), while organic arsenic is relatively weaker. Arsenic pollution is prominent in groundwater, drinking water, and some soils and sediments, making the establishment of accurate detection methods crucial. Existing detection methods include: "Determination of Arsenic in Water by Silver Diethyldithiocarbamate Extraction Spectrophotometry" (HJ 694-2014), "Determination of Arsenic in Water by Atomic Fluorescence Spectrometry" (Appendix to HJ 694-2014), and "Determination of Arsenic in Soil by Flame Atomic Absorption Spectrometry" (HJ 832-2017), which are widely used in routine environmental monitoring.

[0005] Currently, the testing of mercury and arsenic mainly employs atomic absorption spectrometry and atomic fluorescence spectrometry. These methods require specialized instruments, involve cumbersome enrichment processes, and suffer from significant fluctuations in recovery rates. While inductively coupled plasma mass spectrometry (ICP-MS) is commonly used for the analysis of metal elements in water, it is susceptible to interference from matrix components such as water salinity, especially in the determination of trace elements like arsenic and mercury, where the signal response is significantly affected by the water matrix. Due to severe sample matrix interference during analysis, and the fact that the concentration of the analyte in the actual sample is at trace or even ultra-trace levels, conventional analytical methods are no longer sufficient to meet the requirements for accurate determination of these trace analytes. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method and apparatus for simultaneously testing trace mercury and arsenic in water by mass spectrometry with high sensitivity, low detection limit and less susceptibility to substrate interference.

[0007] The technical solution adopted by the present invention to solve its technical problem is as follows: A method for simultaneously testing trace mercury and arsenic in water by mass spectrometry, wherein a water sample is placed in a reaction device, and hydrogen gas is introduced into the sample at 60℃~90℃ to obtain gas a; gas a is detected by method (1) and / or method (2); Method (1): Use a carrier gas to carry gas a into the nebulization chamber of the inductively coupled plasma mass spectrometer for elemental analysis to obtain the concentration information of mercury and arsenic in the sample; Method (2): Gas a is introduced into the enrichment device for enrichment; a carrier gas is introduced into the enrichment device and heated, and the carrier gas is used to continuously carry the gas b discharged from the enrichment device into the nebulization chamber of the inductively coupled plasma mass spectrometer for elemental analysis to obtain the concentration information of mercury and arsenic in the sample; the enrichment device achieves mercury enrichment by forming an amalgam.

[0008] Preferably, the hydrogen gas is introduced into the sample for 3 to 20 minutes.

[0009] Preferably, a carrier gas with a flow rate of 100 mL / min to 200 mL / min is used to carry gas a and / or gas b into the nebulization chamber of the inductively coupled plasma mass spectrometer.

[0010] Preferably, in method (2), the flow rate of the carrier gas introduced into the enrichment device is 100 mL / min to 500 mL / min.

[0011] Preferably, in method (2), the time for introducing carrier gas into the enrichment device is 10 min to 40 min.

[0012] Preferably, the enrichment device uses one or more of gold, palladium, and nano-molybdenum disulfide as the enrichment material.

[0013] Preferably, in method (2), the heating temperature is 180℃~250℃.

[0014] Preferably, the water sample contains salt-related interfering components.

[0015] Preferably, a standard sample of known concentration is prepared, a standard curve is plotted based on the test results of the standard sample, and the mercury and arsenic content in the sample to be tested is calculated based on the standard curve.

[0016] Preferably, the standard sample is prepared using nitric acid as a matrix.

[0017] Based on the same inventive concept, the present invention also provides an apparatus for simultaneously testing trace amounts of mercury and arsenic in water by mass spectrometry, comprising a reaction device, a flow path switching control component, and an enrichment device; the reaction device is connected to the nebulization chamber and the enrichment device of an inductively coupled plasma mass spectrometer respectively through the flow path switching control component; the enrichment device is connected to the nebulization chamber of the inductively coupled plasma mass spectrometer through a pipeline.

[0018] The present invention has the following beneficial effects: (1) By reacting hydrogen with mercury and arsenic in the water sample to generate elemental mercury and arsine, the interference of the sample substrate on the test is effectively avoided. At the same time, it prevents the salt in the sample from depositing on the snipping cone and atomizing chamber during the atomization process, thereby reducing the frequency of replacement of key components, reducing equipment operating costs, and improving the accuracy of test results. (2) For the analysis of arsenic, the method of first converting arsenic into gaseous arsine is adopted, and then the arsenic is introduced into the plasma flame by carrier gas in the atomization chamber. This completely avoids the interference of salt matrix such as sodium chloride. At the same time, chloride ions cannot form argon chloride interference with argon, which effectively improves the detection sensitivity and applicability of arsenic. (3) Based on the existing inductively coupled plasma mass spectrometry instrument in the laboratory, the present invention can realize the measurement of ultra-trace mercury without the need to purchase an atomic fluorescence mercury instrument, which effectively reduces the instrument purchase cost and improves the analytical efficiency of the laboratory. It can simultaneously test the mercury and arsenic content in complex matrices.

[0019] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is the arsenic standard curve diagram of Example 1 of the present invention; Figure 2 This is a mercury standard curve diagram of Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the device used in Embodiment 3 of the present invention.

[0021] Legend: 1. Reaction apparatus; 2. Enrichment apparatus; 3. Inductively coupled plasma mass spectrometer nebulization chamber. Detailed Implementation

[0022] To make the objectives, solutions, and beneficial technologies of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. It should be noted that the embodiments described in this specification are merely illustrative of the invention and are not intended to limit the invention.

[0023] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range.

[0024] In this description, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, "multiple" in "one or more" means two or more, and "more than" in "one or more" means two or more.

[0025] An embodiment of the present invention provides a method for simultaneously testing trace amounts of mercury and arsenic in water by mass spectrometry. A water sample is placed in a reaction device, and hydrogen gas is introduced into the sample at 60°C to 90°C to obtain gas a. Gas a is detected by method (1) and / or method (2). Method (1): Use a carrier gas to carry gas a into the nebulization chamber of the inductively coupled plasma mass spectrometer for elemental analysis to obtain the concentration information of mercury and arsenic in the sample; Method (2): Gas a is introduced into the enrichment device for enrichment; a carrier gas is introduced into the enrichment device and heated, and the carrier gas is used to continuously carry the gas b discharged from the enrichment device into the nebulization chamber of the inductively coupled plasma mass spectrometer for elemental analysis to obtain the concentration information of mercury and arsenic in the sample; the enrichment device achieves mercury enrichment by forming an amalgam.

[0026] This embodiment provides a method for simultaneously testing trace amounts of mercury and arsenic in water using mass spectrometry. It employs a hydrogen reaction system, where hydrogen reacts with mercury and arsenic in the water sample to generate elemental mercury and arsine. The gaseous mercury vapor and arsine are then directly introduced into the nebulization chamber of the inductively coupled plasma mass spectrometer, effectively avoiding interference from the sample substrate. Simultaneously, it prevents salts from depositing on the apex cone and nebulization chamber during nebulization, thereby reducing the frequency of replacement of key components, lowering equipment operating costs, and improving the accuracy of test results.

[0027] When it is necessary to detect trace amounts of mercury in a water sample, gas a is introduced into the enrichment device to form an amalgam, thereby enriching the mercury. A carrier gas is then introduced into the enrichment device and heated to desorb the mercury atoms in the amalgam and release them back as elemental mercury vapor. During this process, the carrier gas continuously carries the arsine and elemental mercury from the enrichment device into the nebulization chamber of the inductively coupled plasma mass spectrometer for elemental analysis, obtaining the concentration information of mercury and arsenic in the sample.

[0028] The method of this invention can not only effectively avoid the interference of the sample substrate on the test and improve the accuracy of the test results, but also be applicable to the detection needs of different detection scenarios, and has strong versatility.

[0029] Conventional ICP-MS injection methods typically involve the following steps: First, the sample needs to be filtered (e.g., using a 0.45 μm pore size filter membrane) to remove any potential particulate matter. Then, the filtered sample solution is delivered to a nebulizer via a peristaltic pump for atomization. The atomized droplets enter the nebulization chamber and are carried into the ICP ion source by argon gas, where ionization is finally completed. However, conventional ICP-MS methods have the following drawbacks: First, they are susceptible to substrate interference, making it difficult to effectively address the interference from high-salt matrices. For example, in the determination of arsenic, when argon (Ar) is used as the carrier gas, the argon in the plasma readily reacts with chloride ions (Cl-) in the sample matrix or reagents. - ) combine to generate 40Ar35Cl + Polyatomic ions, which are related to the target detection ion 75As +The similarity in mass numbers leads to overlap in the detection signals, resulting in mass number interference. This interference is significantly amplified by the extremely high chloride ion concentration in seawater (approximately 19 g / L), causing arsenic determination results to be generally 20%–50% higher. Secondly, operating costs are high. Due to the small nebulizer aperture, impurities in the water sample easily clog the nebulizer, requiring frequent cleaning or replacement of key components (such as the nebulization chamber and the extraction cone), leading to increased failure rates and maintenance costs. Thirdly, the analysis speed is slow. The water sample needs to undergo pretreatment via a microfiltration module, increasing sample pretreatment steps and thus affecting detection efficiency. Fourthly, the large dead volume and significant memory effect, specifically manifested in the long sample transport path (water sample nebulization → gas transport → nebulization chamber mixing → torch introduction), result in significant sample loss, thereby reducing sample transport efficiency and analytical accuracy. The testing method described in this application eliminates the need for filtration and avoids the use of peristaltic pumps and nebulizers, allowing the analytes in the sample to directly enter the nebulization chamber. This not only simplifies the operation process and improves sample transfer efficiency and analytical accuracy, but also reduces the use of precision components and eliminates the need for frequent nebulizer cleaning required in existing detection methods, thus significantly improving analysis speed. Simultaneously, it effectively avoids many shortcomings of conventional ICP-MS, greatly reducing instrument failure rates and operating costs.

[0030] Taking the analysis of trace mercury in seawater as an example, the main challenges in detection stem from three aspects: complex matrix, extremely low concentration, and significant interference. Specifically, these can be broken down as follows: First, the difficulty of detecting ultra-low concentrations. Mercury content in seawater is usually at the ng / L (ppt) level or even lower, approaching the detection limit of most conventional analytical instruments. Conventional analytical methods require pre-concentration techniques to achieve reliable determination, but this process is often time-consuming and complex. Second, the significant matrix effect in seawater. The Na+ content in seawater... + Cl - Mg 2+ The extremely high concentration of plasma can easily interfere with the detection results. For example, while cold atomic absorption / fluorescence has high sensitivity, it is highly susceptible to interference from matrix components such as salt. Furthermore, the enrichment process is cumbersome and the recovery rate fluctuates greatly. Traditional enrichment methods are not only cumbersome in procedure but also face problems such as unstable recovery rates, further increasing the uncertainty and operational difficulty of detection. The testing method of this invention overcomes the limitations of existing technologies that rely on dedicated instruments, and solves the problems of low sensitivity and matrix interference in inductively coupled plasma mass spectrometry (ICP-MS) for mercury testing. It also simplifies sample pretreatment, avoids complex sample pretreatment steps, significantly shortens the detection cycle, and improves detection efficiency. This method can improve the sensitivity and accuracy of detection, enabling the detection of trace mercury in water and seawater.

[0031] In this invention, hydrogen reacts with elements such as arsenic and mercury in a water sample to generate elemental mercury and hydrides or elements such as arsine. When the elemental mercury passes through the enrichment device, it forms an amalgam, an alloy of mercury, formed by elemental mercury and an enrichment material in the enrichment device. The specific shape of the enrichment material is not limited. The enrichment material can be gold, palladium, or nano-molybdenum disulfide. When the enrichment device is heated, the mercury atoms in the amalgam gain energy to desorb and are released back as elemental mercury vapor. The enrichment device itself returns to its original state and can be reused. The introduction of hydrogen gas simultaneously forms arsine with the mercury vapor. Both arsine and mercury vapor enter the nebulizer, thus allowing for simultaneous measurement of arsenic and mercury.

[0032] When carrier gas is introduced into the enrichment device and heated, gas is continuously discharged from the enrichment device. This continuously discharged gas (b) is guided by the carrier gas into the nebulization chamber of the inductively coupled plasma mass spectrometer for detection. Compared to no enrichment, enrichment followed by heating to release mercury vapor, although the total amount of mercury remains unchanged throughout the process, allows for a concentrated release of mercury vapor in a short period, changing from a long-term low concentration to a short-term relatively high concentration. This avoids situations where the concentration is too low for the instrument to detect, thus improving detection accuracy.

[0033] For the analysis of ultra-trace mercury, atomic fluorescence spectrometry is commonly used in laboratories, but this method requires specialized instruments. This invention employs hydrogen-mercury amalgam enrichment-thermal desorption-inductively coupled plasma mass spectrometry (ICP-MS) for detection, enabling the monitoring of ultra-trace mercury without increasing laboratory equipment costs. In contrast, in existing ICP-MS determination of arsenic, argon gas (Ar, carrier gas) in the plasma readily reacts with chloride ions (Cl-) in the sample matrix or reagents. - ) combine to generate 40Ar35Cl + Polyatomic ions, which are related to the target detection ion 75As + The similarity in mass numbers leads to overlap in the detection signals of the two methods, resulting in mass number interference. This interference is significantly amplified by the extremely high chloride ion concentration in seawater (approximately 19 g / L), causing arsenic determination results to be generally 20%-50% higher. The testing method of this invention achieves complete separation of the analyte from the high-salt matrix by converting the analyte into a gaseous form: mercury into gaseous mercury vapor and arsenic into arsine gas. This eliminates the need for dilution or desalination of the seawater sample, effectively avoiding potential elemental changes and losses during pretreatment. Simultaneously, the amalgam enrichment-thermal desorption step reduces the detection limit of mercury from 0.04 μg / L in existing methods to 0.001 μg / L, meeting the requirements for detecting trace amounts of mercury in seawater. Furthermore, the generation of arsine completely eliminates the interference from the 40Ar35Cl... +This method reduces interference, making arsenic determination results more reliable. It not only solves key technical challenges in detecting mercury and arsenic in high-salt matrices but also provides a reliable technical means for the accurate monitoring of trace highly toxic elements in the marine environment, effectively supporting marine ecological security assessment and pollution prevention and control.

[0034] In some embodiments of the present invention, the carrier gas is argon.

[0035] In an embodiment of the present invention, the hydrogen gas is introduced into the sample for 3 min to 20 min.

[0036] In an embodiment of the present invention, a carrier gas with a flow rate of 100 mL / min to 200 mL / min is used to carry gas a and / or gas b into the nebulization chamber of the inductively coupled plasma mass spectrometer.

[0037] In an embodiment of the present invention, in method (2), the flow rate of the carrier gas introduced into the enrichment device is 100 mL / min to 500 mL / min.

[0038] In an embodiment of the present invention, in method (2), the time for introducing carrier gas into the enrichment device is 10 min to 40 min.

[0039] In embodiments of the present invention, the enrichment device uses one or more of gold, palladium, and nano-molybdenum disulfide as enrichment materials.

[0040] In some embodiments of the present invention, the ratio of gold to sample mass in the enrichment device is 1:5 to 10.

[0041] In an embodiment of the present invention, in method (2), the heating temperature is 180°C to 250°C. The release effect is better within this temperature range.

[0042] In an embodiment of the present invention, the water sample contains salt-related interfering components. Conventional methods are ineffective in detecting water containing salt-related interfering components (such as seawater), while the method of the present invention has better detection results.

[0043] In an embodiment of the present invention, a standard sample of known concentration is prepared, a standard curve is plotted based on the test results of the standard sample, and the mercury and arsenic content in the sample to be tested is calculated based on the standard curve.

[0044] In an embodiment of the present invention, the standard sample is prepared using nitric acid as a matrix. Nitric acid is used to ensure the quality of the standard sample; as a fixative, nitric acid can prevent changes in the analyte in the standard sample. There is no need to use nitric acid in the test sample.

[0045] This invention provides an apparatus for simultaneously testing trace amounts of mercury and arsenic in water using mass spectrometry. The apparatus includes a reaction device, a flow path switching control component, and an enrichment device. The reaction device is connected to the nebulization chamber and the enrichment device of an inductively coupled plasma mass spectrometer via the flow path switching control component. The enrichment device is connected to the nebulization chamber of the inductively coupled plasma mass spectrometer via a pipeline.

[0046] When the device is used for testing, if the detection is performed using only method (1), the gas a is prevented from passing through the enrichment device and enters the nebulization chamber of the inductively coupled plasma mass spectrometer by the flow path switching control component; if the detection is performed using only method (2), the gas a is first allowed to enter the enrichment device by the flow path switching control component, and then the gas b discharged from the enrichment device is allowed to enter the nebulization chamber of the inductively coupled plasma mass spectrometer.

[0047] For example, the reaction device is connected to the nebulization chamber and enrichment device of the inductively coupled plasma mass spectrometer via a flow path switching control component; the enrichment device is connected to the nebulization chamber of the inductively coupled plasma mass spectrometer via a pipe. When the device is used for testing, if only method (1) is used for detection, the reaction device is connected to the nebulization chamber of the inductively coupled plasma mass spectrometer via the flow path switching control component, so that gas a does not pass through the enrichment device and directly enters the nebulization chamber of the inductively coupled plasma mass spectrometer; if only method (2) is used for detection, the reaction device is connected to the enrichment device via the flow path switching control component, so that gas a enters the enrichment device, and then gas b discharged from the enrichment device enters the nebulization chamber of the inductively coupled plasma mass spectrometer.

[0048] Example The following examples describe the disclosure of this invention in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight. Unless otherwise stated, all reagents used in the examples are available commercially or synthesized using conventional methods and are ready for use without further processing. Unless otherwise stated, all instruments used in the examples are available commercially.

[0049] Example 1 The sample to be tested in this embodiment is seawater. Preparation method of standard sample: Use 2wt% high-purity nitric acid as matrix to dilute mercury and arsenic single-element standard stock solution (100mg / L) stepwise.

[0050] The method for simultaneously testing trace amounts of mercury and arsenic in water using mass spectrometry in this embodiment is as follows: (1) Take a water sample and place it in the reaction device. At 70°C, introduce hydrogen into the sample for 10 min. Collect the gas a discharged from the reaction device. Pass gas a into the enrichment device, where the mass ratio of gold wire to sample is 1:10. (2) Argon gas is introduced into the enrichment device and heated to 180°C. The argon gas flow rate is 100 mL / min for 30 min. Argon gas is used to continuously carry the gas b discharged from the enrichment device into the nebulization chamber of the inductively coupled plasma mass spectrometer for elemental analysis to obtain sample information. The argon gas flow rate is 100 mL / min.

[0051] First, a standard curve is plotted based on the test results of the standard sample. Then, the mercury and arsenic contents in the sample to be tested are calculated based on the standard curve.

[0052] The operating parameters of the inductively coupled plasma mass spectrometer are as follows: power 1500W, plasma gas flow rate 14L / min, auxiliary gas flow rate 0.8L / min, nebulizer flow rate 1.1L / min, injection pump flow rate 30rpm, injection flushing time 16s, scanning mode is peak skipping, residence time is 0.15s, single element integration time is 6s, sampling cone is 1.1mm, and cutoff is 0.7mm.

[0053] The arsenic standard curve obtained in this embodiment is shown below. Figure 1 The mercury standard curve can be found in [the original text]. Figure 2 .

[0054] In this embodiment, a repeatability verification test was performed on a certain seawater sample to be tested. The results are shown in Table 1. The units for arsenic and mercury content in the table are mg / L.

[0055] Table 1. Repeatability verification test results of Example 1 As can be seen from the results in Table 1, the method of the present invention for testing the arsenic and mercury content in water samples has high stability and good repeatability.

[0056] Example 2 In this embodiment, the sample to be tested is seawater, and the accuracy of the analysis results is determined by adding spikes and recovering the samples.

[0057] Preparation method of standard samples: Use 2wt% high-purity nitric acid as the matrix to serially dilute the mercury and arsenic single-element standard stock solutions (100mg / L). The concentration sampling points for the arsenic and mercury standard sample curves in Example 2 are shown in Table 2. The units for arsenic and mercury content in the table are mg / L.

[0058] Table 2. Sampling points for the concentration curves of arsenic and mercury standard samples in Example 2 (unit: mg / L) In this embodiment, the arsenic spiked amount is 0.005 mg / L, and the mercury spiked amount is 0.00002 mg / L. The spiking solution is prepared as follows: add the corresponding amount of standard sample to a volumetric flask using a pipette, and then dilute to the mark with the sample to be tested. The spiked solution recovery rate is calculated as follows: Spike recovery rate (%) = [(Spiked test value - Water sample test value) / Spiked amount] × 100%.

[0059] The method for simultaneously testing trace amounts of mercury and arsenic in water using mass spectrometry in this embodiment is as follows: (1) Take a water sample and place it in the reaction device. At 60°C, introduce hydrogen into the sample for 20 minutes. Collect the gas a discharged from the reaction device. Pass gas a into the enrichment device, where the mass ratio of gold wire to sample is 1:5. (2) Argon gas is introduced into the enrichment device and heated to 220°C. The argon gas flow rate is 500 mL / min for 20 min. Argon gas is used to continuously carry the gas b discharged from the enrichment device into the nebulization chamber of the inductively coupled plasma mass spectrometer for elemental analysis to obtain sample information. The argon gas flow rate is 200 mL / min.

[0060] First, a standard curve is plotted based on the test results of the standard sample. Then, the mercury and arsenic contents in the sample to be tested are calculated based on the standard curve.

[0061] The operating parameters of the inductively coupled plasma mass spectrometer are as follows: power 1500W, plasma gas flow rate 14L / min, auxiliary gas flow rate 0.8L / min, nebulizer flow rate 1.1L / min, injection pump flow rate 30rpm, injection flushing time 16s, scanning mode is peak skipping, residence time is 0.15s, single element integration time is 6s, sampling cone is 1.1mm, and cutoff is 0.7mm.

[0062] The test results of a certain seawater sample in this embodiment are shown in Table 3. The units of arsenic and mercury content in the table are mg / L.

[0063] Table 3. Test results of actual seawater samples for trace arsenic and mercury in Example 2 As can be seen from the recovery rate in Table 3, this embodiment has a relatively accurate test effect.

[0064] Example 3 In this embodiment, the sample to be tested was industrial wastewater. The accuracy of the analytical results was determined by spiked recovery. Industrial wastewater often has a high content of heavy metals, which can also be detected using a non-concentration method. This embodiment conducted experiments using both concentration and non-concentration methods.

[0065] Preparation method of standard samples: Use 2wt% high-purity nitric acid as the matrix to serially dilute the mercury and arsenic single-element standard stock solutions (100mg / L). The concentration sampling points for the arsenic and mercury standard sample curves in Example 3 are shown in Table 4. The units for arsenic and mercury content in the table are mg / L.

[0066] Table 4. Sampling points for the concentration curves of arsenic and mercury standard samples in Example 3 (unit: mg / L) In this embodiment, the arsenic spiking amount is 0.02 mg / L, and the mercury spiking amount is 0.01 mg / L. The spiking solution is prepared as follows: add the corresponding amount of standard sample to a volumetric flask using a pipette, and then dilute to the mark with the sample to be tested. The spiked recovery rate is calculated as follows: Spike recovery rate (%) = [(Spiked test value - Water sample test value) / Spiked amount] × 100%.

[0067] The method for testing trace amounts of mercury and arsenic in water in this embodiment, using a non-enrichment approach, is as follows: A water sample was placed in a reaction apparatus, and hydrogen gas was introduced into the sample at 90°C for 15 min. Gas a was collected from the reaction apparatus. Argon gas was used to continuously carry gas a from the reaction apparatus into the nebulization chamber of an inductively coupled plasma mass spectrometer for elemental analysis to obtain sample information. The argon gas flow rate was 200 mL / min.

[0068] The method for testing trace amounts of mercury and arsenic in water through enrichment in this embodiment is as follows: (1) Take a water sample and place it in the reaction device. At 90°C, introduce hydrogen into the sample for 15 min. Collect the gas a discharged from the reaction device. Pass gas a into the enrichment device, where the mass ratio of gold wire to sample is 1:10. (2) Argon gas is introduced into the enrichment device and heated to 200℃. The argon gas flow rate is 200mL / min for 40min. Argon gas is used to continuously carry the gas b discharged from the enrichment device into the nebulization chamber of the inductively coupled plasma mass spectrometer for elemental analysis to obtain sample information. The argon gas flow rate is 200mL / min.

[0069] like Figure 3As shown, the apparatus used in this embodiment includes a reaction device 1, a flow path switching control component, and an enrichment device 2. The reaction device 1 is connected to the nebulization chamber 3 and the enrichment device 2 of the inductively coupled plasma mass spectrometer via the flow path switching control component. The enrichment device 2 is connected to the nebulization chamber 3 of the inductively coupled plasma mass spectrometer via a pipeline. The reaction device 1 can be connected to a hydrogen generator or a hydrogen cylinder (not shown in the figure). A flow regulating device (such as a regulating valve, not shown in the figure) is provided on the pipeline. During the non-enrichment test, the flow path switching control component allows gas a to enter the nebulization chamber 3 of the inductively coupled plasma mass spectrometer without passing through the enrichment device 2. During the enrichment test, in step (1), the flow path switching control component allows gas a to enter the enrichment device 2. In step (2), the gas b discharged from the enrichment device 2 enters the nebulization chamber 3 of the inductively coupled plasma mass spectrometer.

[0070] First, a standard curve is plotted based on the test results of the standard sample. Then, the mercury and arsenic contents in the sample to be tested are calculated based on the standard curve.

[0071] The operating parameters of the inductively coupled plasma mass spectrometer are as follows: power 1500W, plasma gas flow rate 14L / min, auxiliary gas flow rate 0.8L / min, nebulizer flow rate 1.1L / min, injection pump flow rate 30rpm, injection flushing time 16s, scanning mode is peak skipping, residence time is 0.15s, single element integration time is 6s, sampling cone is 1.1mm, and cutoff is 0.7mm.

[0072] The test results of a certain industrial wastewater sample in this embodiment are shown in Table 5. The units for arsenic and mercury content in the table are mg / L.

[0073] Table 5 Test results of actual samples of arsenic and mercury in industrial wastewater from Example 3 As can be seen from the recovery rates in Table 5, this embodiment has a relatively accurate test effect, especially when using the enrichment method.

[0074] Example 4 In this embodiment, the sample to be tested is surface water (river water), and the accuracy of the analysis results is determined by adding spikes and recovering the samples.

[0075] Preparation method of standard samples: Use 2wt% high-purity nitric acid as the matrix to serially dilute the mercury and arsenic single-element standard stock solutions (100mg / L). The concentration sampling points for the arsenic and mercury standard sample curves in Example 4 are shown in Table 6. The units for arsenic and mercury content in the table are mg / L.

[0076] Table 6. Sampling points for the concentration curves of arsenic and mercury standard samples in Example 3 (unit: mg / L) In this embodiment, the arsenic spiked amount is 0.01 mg / L, and the mercury spiked amount is 0.001 mg / L. The spiking solution is prepared as follows: add the corresponding amount of standard sample to a volumetric flask using a pipette, and then dilute to the mark with the sample to be tested. The spiked recovery rate is calculated as follows: Spike recovery rate (%) = [(Spiked test value - Water sample test value) / Spiked amount] × 100%.

[0077] The method for simultaneously testing trace amounts of mercury and arsenic in water using mass spectrometry in this embodiment is as follows: (1) Take a water sample and place it in the reaction device. At 80°C, introduce hydrogen into the sample for 5 minutes. Collect the gas a discharged from the reaction device. Introduce gas a into the enrichment device, where the mass ratio of gold wire to sample is 1:8. (2) Argon gas is introduced into the enrichment device and heated to 250°C. The argon gas flow rate is 400 mL / min for 10 min. Argon gas is used to continuously carry the gas b discharged from the enrichment device into the nebulization chamber of the inductively coupled plasma mass spectrometer for elemental analysis to obtain sample information. The argon gas flow rate is 150 mL / min.

[0078] First, a standard curve is plotted based on the test results of the standard sample. Then, the mercury and arsenic contents in the sample to be tested are calculated based on the standard curve.

[0079] The operating parameters of the inductively coupled plasma mass spectrometer are as follows: power 1500W, plasma gas flow rate 14L / min, auxiliary gas flow rate 0.8L / min, nebulizer flow rate 1.1L / min, injection pump flow rate 30rpm, injection flushing time 16s, scanning mode is peak skipping, residence time is 0.15s, single element integration time is 6s, sampling cone is 1.1mm, and cutoff is 0.7mm.

[0080] The test results of a certain seawater sample in this embodiment are shown in Table 7. The units of arsenic and mercury content in the table are mg / L.

[0081] Table 7 Test results of actual samples of arsenic and mercury in surface water in Example 4 As can be seen from the recovery rate in Table 7, this embodiment has a relatively accurate test effect.

[0082] Example 5 To compare the testing results of the method of this invention with the traditional ICP-MS method, six different seawater samples were tested for mercury content using both methods (the method in Example 2 and the traditional ICP-MS method). The samples were numbered Seawater 1 to 6. Samples 4 to 6 were also subjected to spiking tests; the preparation and spiking methods for the standard samples were as described in Example 2. The test results for Seawater 1 to 3 are shown in Table 8, and the test results for Seawater 4 to 6 are shown in Table 9. The concentration units in Table 8 are ng / L.

[0083] Table 8. Test results of mercury in seawater 1-3 in Example 5 Table 9. Test results of mercury in seawater 4-6 in Example 5 As can be seen from Table 8, for the same sample, the method of the present invention has smaller fluctuations in test results, higher sensitivity, and stronger response to low concentration samples compared with the traditional ICP-MS method. The detection limit of the traditional ICP-MS method is about 0.04 μg / L, while the method of the present invention can reach 0.001 μg / L, which improves the sensitivity by about 2 to 3 orders of magnitude.

[0084] As can be seen from the results in Table 9, the recovery rate of traditional ICP-MS spiked samples is higher than 130%, and the accuracy is not high. The method of this invention has made significant progress in terms of accuracy compared with traditional ICP-MS.

Claims

1. A method for simultaneously determining trace amounts of mercury and arsenic in water using mass spectrometry, characterized in that, A water sample is placed in a reaction apparatus, and hydrogen gas is introduced into the sample at 60℃~90℃ to obtain gas a; gas a is detected by method (1) and / or method (2); Method (1): Use a carrier gas to carry gas a into the nebulization chamber of the inductively coupled plasma mass spectrometer for elemental analysis to obtain the concentration information of mercury and arsenic in the sample; Method (2): Gas a is introduced into the enrichment device for enrichment; a carrier gas is introduced into the enrichment device and heated, and the carrier gas is used to continuously carry the gas b discharged from the enrichment device into the nebulization chamber of the inductively coupled plasma mass spectrometer for elemental analysis to obtain the concentration information of mercury and arsenic in the sample; the enrichment device achieves mercury enrichment by forming an amalgam.

2. The method for simultaneously testing trace amounts of mercury and arsenic in water by mass spectrometry according to claim 1, characterized in that, The hydrogen gas was introduced into the sample for 3 to 20 minutes.

3. The method for simultaneously testing trace amounts of mercury and arsenic in water by mass spectrometry according to claim 1, characterized in that, Gas a and / or gas b are introduced into the nebulization chamber of the inductively coupled plasma mass spectrometer using a carrier gas with a flow rate of 100 mL / min to 200 mL / min.

4. The method for simultaneously testing trace amounts of mercury and arsenic in water by mass spectrometry according to claim 1, characterized in that, In method (2), the flow rate of the carrier gas introduced into the enrichment device is 100 mL / min to 500 mL / min; in method (2), the time for introducing the carrier gas into the enrichment device is 10 min to 40 min.

5. The method for simultaneously testing trace amounts of mercury and arsenic in water by mass spectrometry according to claim 1, characterized in that, The enrichment device uses one or more of gold, palladium, and nano-molybdenum disulfide as enrichment materials.

6. The method for simultaneously testing trace amounts of mercury and arsenic in water by mass spectrometry according to claim 1, characterized in that, In method (2), the heating temperature is 180℃~250℃.

7. The method for simultaneously testing trace amounts of mercury and arsenic in water by mass spectrometry according to claim 1, characterized in that, The water sample contained salt-related interfering components.

8. The method for simultaneously determining trace amounts of mercury and arsenic in water by mass spectrometry according to any one of claims 1 to 7, characterized in that, Prepare standard samples with known concentrations, plot a standard curve based on the test results of the standard samples, and calculate the mercury and arsenic content in the sample to be tested based on the standard curve.

9. The method for simultaneously testing trace amounts of mercury and arsenic in water by mass spectrometry according to claim 8, characterized in that, The standard sample was prepared using nitric acid as the matrix.

10. An apparatus for simultaneously testing trace amounts of mercury and arsenic in water by mass spectrometry, used to implement the method for simultaneously testing trace amounts of mercury and arsenic in water by mass spectrometry as described in any one of claims 1 to 9, characterized in that, It includes a reaction device, a flow path switching control component, and an enrichment device; the reaction device is connected to the nebulization chamber and the enrichment device of the inductively coupled plasma mass spectrometer via the flow path switching control component; the enrichment device is connected to the nebulization chamber of the inductively coupled plasma mass spectrometer via a pipeline.

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