Metal-ceramic electrothermal evaporation mercury analyzer and method for determining mercury content in soil

Abstract

The present invention provides a metal-ceramic electrothermal evaporation mercury analyzer and a method for determining mercury content in soil. The metal-ceramic electrothermal evaporation mercury analyzer includes an electrothermal evaporation device, a catalytic pyrolysis furnace, and an atomic spectrum detector. The electrothermal evaporation device is connected to the inlet of the catalytic pyrolysis furnace, and the inlet of the atomic spectrum detector is connected to the outlet of the catalytic pyrolysis furnace for detecting the mercury content in the sample. The electrothermal evaporation device includes a metal-ceramic heating cup and a sealed silica gel base. The sealed silica gel base is hermetically connected to the inlet of the catalytic pyrolysis furnace. The ceramic heating cup is arranged above the sealed silica gel base and is located inside the catalytic pyrolysis furnace. A vertical air inlet pipe is provided inside the sealed silica gel base, and the upper end of the air inlet pipe extends into the catalytic pyrolysis furnace. Compared with the original mercury analyzer, the metal-ceramic electrothermal evaporation mercury analyzer provided by the present invention significantly reduces the power consumption of the evaporator, improves the catalyst life, reduces the size of the sampling device, and saves costs.

Description

Technical Field

[0001] The invention belongs to the technical field of mercury detectors, and in particular relates to a metal-ceramic electrothermal evaporation mercury detector and a method for determining mercury content in soil. Background Art

[0002] Mercury (Hg) is a highly toxic heavy metal that can be ingested into the body through skin contact, respiratory tract and digestive tract absorption, and in the form of highly toxic organic compounds, it can cause serious damage to the brain, nerves, kidneys and digestive system. In order to prevent and control heavy metal mercury pollution in the agricultural sector, my country has formulated a series of mercury limit standards.

[0003] At present, the commonly used analytical methods for mercury determination are mainly: hydride generation atomic fluorescence spectrometry (HG-AFS), cold vapor atomic absorption spectrometry (CVAAS), inductively coupled plasma mass spectrometry (ICP-MS), etc. These traditional laboratory detection methods have high analytical sensitivity and technical maturity, but usually require complex sample pretreatment, which is time-consuming and laborious, and trace mercury elements are easily lost, making it difficult to achieve rapid detection. In order to achieve rapid analysis of mercury, the direct solid sampling (SS) method based on electrothermal evaporation (ETV) has been widely adopted as a standard method. So far, direct injection mercury analyzers have become the most successful commercial ETV instruments, mainly consisting of ETV, catalytic pyrolysis furnace (with or without gold amalgam), and atomic absorption spectrometry (AAS) or atomic fluorescence spectrometry (AFS) detectors. However, due to the use of ETV, catalytic pyrolysis furnace and gold amalgam, the instrument size of these direct injection mercury analyzers is still large and the power consumption is large. From the perspective of principle and design, it is difficult to further miniaturize and field-based.

[0004] In addition to the catalytic pyrolysis furnace, direct solid sampling cannot be separated from the ETV device. In the existing technology, the ETV device is mainly composed of a quartz tube covered with a nickel-chromium (Ni-Cr) heating coil. At 600°C, the total energy consumption of the ETV is more than 500W, accounting for about one-third of the total energy consumption. Although metal coil ETVs such as tungsten wire and rhenium wire have excellent heating efficiency and low power consumption (tens of watts), they cannot directly load solid samples, complicating the on-site sample preparation process. In addition, graphite furnaces can be used as ETVs for mercury evaporation introduction in AAS, ICP-OES and ICP-MS, but their power consumption is still very high and cannot be used on-site.

[0005] The ETV of traditional mercury detectors is usually followed by a catalytic pyrolysis furnace, which is often filled with catalysts and adsorbents such as Mn3O4, KMnO4, CaO, and MgO to decompose gaseous organic compounds and soot particles generated after sample combustion, and at the same time absorb matrix interferences such as halogens and sulfur oxides. These commonly used catalyst fillers on the market are not only expensive, but also prone to powdering and failure during use, with a short lifespan and frequent replacement required, resulting in increased detection costs. Summary of the Invention

[0006] Aiming at the above deficiencies in the prior art, the metal-ceramic electrothermal evaporation mercury detector provided by the present invention solves the problems of large volume, high power consumption, and difficulty in further miniaturization of existing mercury detectors.

[0007] In order to achieve the above invention objectives, the technical solution adopted by the present invention is as follows:

[0008] Provide a metal-ceramic electrothermal evaporation mercury detector, including an electrothermal evaporation device, a catalytic pyrolysis furnace, and an atomic spectrum detector. The lower end of the catalytic pyrolysis furnace is provided with an inlet, and the upper end is provided with an outlet. The electrothermal evaporation device is connected to the inlet of the catalytic pyrolysis furnace, and the atomic spectrum detector is connected to the outlet of the catalytic pyrolysis furnace for detecting the mercury content in the sample.

[0009] The electrothermal evaporation device includes a metal-ceramic heating cup and a sealed silica gel base. The sealed silica gel base is hermetically connected to the inlet of the catalytic pyrolysis furnace. The metal-ceramic heating cup is arranged above the sealed silica gel base and is located inside the catalytic pyrolysis furnace. A vertical air inlet pipe is provided inside the sealed silica gel base, and the upper end of the air inlet pipe extends into the catalytic pyrolysis furnace.

[0010] Further: It also includes a constant power control component, and the metal-ceramic heating cup is connected to the constant power control component.

[0011] Further: A support seat is arranged at the upper end of the sealed silica gel base, and the metal-ceramic heating cup is arranged on the support seat.

[0012] Further: The upper end of the metal-ceramic heating cup is a sample inlet, and a metal heating wire is arranged inside the cup wall of the metal-ceramic heating cup.

[0013] Further: The metal heating wire is a heating wire made of tungsten-molybdenum alloy.

[0014] Further: The air inlet pipe is a hollow copper pipe.

[0015] Further, the catalytic pyrolysis furnace includes a quartz tube and a small constant-temperature heating furnace. The filler inside the quartz tube is alumina particles, which are used for interference elimination during mercury evaporation and mercury atom transmission.

[0016] Further: The atomic spectrum detector includes an atomic fluorescence detector and an atomic absorption detector.

[0017] A method for determining the mercury content in soil by a metal-ceramic electrothermal evaporation mercury analyzer, comprising the following steps:

[0018] S1. Load 0 - 200 mg of dry powdered soil sample into a metal-ceramic heating cup;

[0019] S2. Place the metal-ceramic heating cup in a catalytic pyrolysis furnace and seal it for heating. At the same time, introduce a carrier gas (the types of carrier gas include argon, air, and oxygen) into the catalytic pyrolysis furnace through an inlet pipe;

[0020] S3. Use an atomic spectral detector to detect the Hg content at the outlet of the catalytic pyrolysis furnace, read the area of the peak spectrum diagram, and obtain the quantitative detection result of the Hg content in the soil sample according to the linear relationship between the peak area and the Hg injection amount.

[0021] The beneficial effects of the present invention are as follows:

[0022] 1. The mercury analyzer provided by the present invention can realize direct injection analysis of solid samples. Using a metal-ceramic material as an electrothermal evaporation device (ETV), a metal-ceramic heating cup is designed to replace the original ETV. The heating power is as low as 30 W to completely evaporate mercury in the soil.

[0023] 2. Using alumina particles to replace the catalytic combustion filler, it is applicable to soil samples with an organic matter content of less than 20%, avoiding the pulverization and failure of traditional catalytic fillers and improving the service life of the filler.

[0024] 3. Canceling the gold amalgam without losing the anti-interference ability and sensitivity of the instrument. Compared with the original mercury analyzer, the analysis performance significantly reduces the power consumption of the evaporator, reduces the size of the evaporator, and saves costs. This new type of metal-ceramic ETV undoubtedly has good commercial application potential in direct injection mercury analyzers. Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the overall structure of the metal-ceramic electrothermal evaporation mercury analyzer of the present invention;

[0026] Figure 2 It is a schematic diagram of the structure of the electrothermal evaporation device of the metal-ceramic electrothermal evaporation mercury analyzer of the present invention;

[0027] Figure 3 It is a schematic diagram of the fitting linear equation of the soil matrix reference material provided in Example 2 of the present invention; wherein, the abscissa represents the Hg injection amount, and the ordinate represents the area of the peak spectrum diagram;

[0028] Figure 4 It is a schematic diagram of the fitting linear equation of the soil matrix reference material provided in Example 3 of the present invention; wherein, the abscissa represents the Hg injection amount, and the ordinate represents the area of the peak spectrum diagram.

[0029] Among them: 1. Electrothermal evaporation device; 2. Catalytic pyrolysis furnace; 3. Atomic spectroscopy detector; 4. Metal-ceramic heating cup; 5. Sealed silicone base; 6. Inlet pipe; 7. Constant power control component; 8. Support base; 9. Sampling port; 10. Metal heating wire. Specific embodiments

[0030] The specific embodiments of the present invention will be described below to facilitate those skilled in the art of the present technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art of the present technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions created using the concept of the present invention are within the scope of protection.

[0031] Example 1

[0032] Referring to Figure 1-2 , a metal-ceramic electrothermal evaporation mercury analyzer, including an electrothermal evaporation device 1, a catalytic pyrolysis furnace 2 and an atomic spectroscopy detector 3. The atomic spectroscopy detector 3 includes an atomic fluorescence detector and an atomic absorption detector. The lower end of the catalytic pyrolysis furnace 2 is provided with an inlet, and the upper end is provided with an outlet. The electrothermal evaporation device 1 is connected to the inlet of the catalytic pyrolysis furnace 2, and the atomic spectroscopy detector 3 is connected to the outlet of the catalytic pyrolysis furnace 2 for detecting the mercury content in the sample; preferably, the catalytic pyrolysis furnace 2 is movably arranged on the electrothermal evaporation device 1 for convenient sampling.

[0033] Specifically, the electrothermal evaporation device 1 includes a metal-ceramic heating cup 4 and a sealed silicone base 5. The sealed silicone base 5 is hermetically connected to the lower end of the catalytic pyrolysis furnace 2. A support base 8 is provided at the upper end of the sealed silicone base 5, and the metal-ceramic heating cup 4 is arranged on the support base 8. The upper end of the metal-ceramic heating cup 4 is a sampling port 9, and a metal heating wire 10 is arranged inside the cup wall of the metal-ceramic heating cup 4. Preferably, the metal heating wire 10 is a heating wire made of tungsten-molybdenum alloy. An inlet pipe 6 is vertically arranged inside the sealed silicone base 5, and the upper end of the inlet pipe 6 extends into the catalytic pyrolysis furnace 2. Preferably, the inlet pipe 6 is a hollow copper pipe.

[0034] The present invention further includes a constant power control component 7, and the metal-ceramic heating cup 4 is connected to the constant power control component 7 to control the power of the metal-ceramic heating cup 4.

[0035] In order to solve the problem that the commonly used catalyst fillers are expensive at present, and are prone to powdering and failure during use, have a short service life, and need to be replaced frequently, resulting in an increase in detection costs, the present invention also has the following design.

[0036] The catalytic pyrolysis furnace includes a quartz tube and a small constant-temperature heating furnace. The filler in the quartz tube is alumina particles, which are used for interference elimination during mercury evaporation and mercury atom transmission.

[0037] In view of the characteristics of low organic matter content and relatively low organic interference in soil samples, this embodiment selects the simpler and lower-cost alumina in this embodiment. Alumina is a high-hardness inorganic compound and belongs to a typical amphoteric oxide. Using alumina particles to replace the traditional composite catalyst filler can not only increase the service life but also significantly reduce the price, thus effectively reducing the usage and consumption cost of the catalytic tube.

[0038] Example 2

[0039] A method for determining the mercury content in soil using the metal-ceramic electrothermal evaporation mercury analyzer provided in Example 1 includes the following steps:

[0040] S1. Load 0 - 200 mg of dry powdered soil sample into the metal-ceramic heating cup 4;

[0041] S2. Place the metal-ceramic heating cup 4 in the catalytic pyrolysis furnace 2 and seal it for heating. At the same time, introduce a carrier gas into the catalytic pyrolysis furnace 2 through the inlet pipe 6. The selected carrier gas is argon;

[0042] S3. Use an atomic fluorescence detector to detect the Hg content at the outlet of the catalytic pyrolysis furnace 2, read the area of the peak spectrum, and obtain the quantitative detection result of the Hg content in the soil sample according to the linear relationship between the peak area and the Hg injection amount.

[0043] In this embodiment, a soil matrix reference material is selected to fit the linear equation. In the range of 0.16 - 11.8 ng Hg, the linear regression coefficient R 2 = 0.996. The detection limit (LOD) of this method is 8 pg, and the quantification limit (LOQ) is 26 pg. The RSD of repeated determination of soil samples 3 times is 2% - 11%. Compared with the standard method of "HJ 923-2017 Determination of total mercury in soil and sediment - Catalytic pyrolysis / cold atomic absorption spectrophotometry", the Hg recovery rate is 96% - 107%, indicating that this method has good accuracy, and this metal-ceramic electrothermal evaporation mercury analyzer can be used for rapid detection of soil Hg.

[0044]

[0045] a GSS-2a, certified value: 17 ± 4 μg / kg; b GSS-28, certified value: 143 ± 13 μg / kg; c GSS-5, certified value: 290 ± 30 μg / kg.

[0046] Example 3

[0047] A method for determining the mercury content in soil by using the metal-ceramic electrothermal evaporation mercury analyzer provided in Example 1, comprising the following steps:

[0048] S1. Load 0 - 200 mg of dry powdered soil sample into the metal-ceramic heating cup 4;

[0049] S2. Place the metal-ceramic heating cup 4 in the catalytic pyrolysis furnace 2 and seal it for heating. Meanwhile, introduce carrier gas into the catalytic pyrolysis furnace 2 through the inlet pipe 6. The types of carrier gas include air and oxygen;

[0050] S3. Detect the Hg content at the outlet of the catalytic pyrolysis furnace 2 with an atomic absorption detector, read the area of the peak spectrum. According to the linear relationship between the peak area and the Hg injection amount, the quantitative detection result of the Hg content in the soil sample can be obtained.

[0051] In this example, a soil matrix reference material is selected to fit the linear equation. In the range of 0.4 - 11.8 ng Hg, the linear regression coefficient R 2 = 0.998. The LOD of this method is 20 pg, and the LOQ is 67 pg. The RSD of repeated determination of soil samples 3 times is 2% - 13%. Compared with the standard method of "HJ 923-2017 Determination of total mercury in soil and sediment - Catalytic pyrolysis / cold atomic absorption spectrophotometry", the Hg recovery rate is 85% - 113%, indicating that this method has good accuracy, and this metal-ceramic electrothermal evaporation mercury analyzer can be used for rapid detection of soil Hg.

[0052]

[0053] a GSS-2a, certified value: 17 ± 4 μg / kg; b GSS-28, certified value: 143 ± 13 μg / kg; c GSS-5, certified value: 290 ± 30 μg / kg.

[0054] The metal-ceramic electrothermal vaporization mercury analyzer provided by the present invention can directly detect solid samples. Using metal-ceramic materials as the electrothermal vaporization device ETV, a metal-ceramic heating cup is designed to replace the ETV after the original catalytic pyrolysis furnace. The heating power is as low as 30 W to completely vaporize mercury in soil. In addition, the gold amalgam is removed without losing the anti-interference ability and sensitivity of the instrument. The LOD of the metal-ceramic electrothermal vaporization mercury analyzer of the present invention is as low as 0.1 μg / kg, the relative standard deviation RSD of the Hg standard is within 7%, and the relative standard deviation RSD of the actual sample is within 15%, with high sensitivity and precision. Compared with the original mercury analyzer in terms of analytical performance, the power consumption of the evaporator is significantly reduced, the size of the instrument is reduced, and the cost is saved. This new type of metal-ceramic ETV undoubtedly has good commercial application potential in direct injection mercury analyzers.

[0055] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0056] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A metal-ceramic electrothermal evaporation mercury analyzer, comprising an electrothermal evaporation device (1), a catalytic pyrolysis furnace (2) and an atomic spectrum detector (3), characterized in that: The lower end of the catalytic pyrolysis furnace (2) is provided with an inlet, and the upper end is provided with an outlet. The electrothermal evaporation device (1) is connected to the inlet of the catalytic pyrolysis furnace (2), and the atomic spectrum detector (3) is connected to the outlet of the catalytic pyrolysis furnace (2) for detecting the mercury content in the sample; The electrothermal evaporation device (1) includes a metal-ceramic heating cup (4) and a sealed silica gel base (5). The sealed silica gel base (5) is hermetically connected to the inlet of the catalytic pyrolysis furnace (2). The metal-ceramic heating cup (4) is arranged above the sealed silica gel base (5) and is located inside the catalytic pyrolysis furnace (2). A gas inlet pipe (6) is vertically arranged inside the sealed silica gel base (5), and the upper end of the gas inlet pipe (6) extends into the catalytic pyrolysis furnace (2); The upper end of the metal-ceramic heating cup (4) is a sample inlet (9), and a metal heating wire (10) is arranged inside the cup wall of the metal-ceramic heating cup (4); the metal heating wire (10) is a heating wire made of tungsten-molybdenum alloy; The catalytic pyrolysis furnace (2) includes a quartz tube and a small constant-temperature heating furnace. The filler inside the quartz tube is alumina particles, which are used for interference elimination during mercury evaporation and mercury atom transmission.

2. The metal-ceramic electrothermal evaporation mercury analyzer according to claim 1, wherein: It further includes a constant power control component (7), and the metal-ceramic heating cup (4) is connected to the constant power control component (7).

3. The metal-ceramic electrothermal evaporation mercury analyzer according to claim 1, wherein: A support seat (8) is arranged at the upper end of the sealed silica gel base (5), and the metal-ceramic heating cup (4) is arranged on the support seat (8).

4. The metal-ceramic electrothermal evaporation mercury analyzer according to claim 1, characterized in that: The gas inlet pipe (6) is a hollow copper pipe.

5. The metal-ceramic electrothermal evaporation mercury analyzer according to claim 1, characterized in that: The atomic spectrum detector (3) includes an atomic fluorescence detector and an atomic absorption detector.

6. A method for determining the mercury content in soil by a metal-ceramic electrothermal evaporation mercury analyzer as described in claim 1, characterized in that: It includes the following steps: S1. Load 0 - 200 mg of dry powdered soil sample into the metal-ceramic heating cup (4); S2. Place the metal-ceramic heating cup (4) in the catalytic pyrolysis furnace (2) and seal and heat it. At the same time, introduce a carrier gas into the catalytic pyrolysis furnace (2) through the gas inlet pipe (6). The types of carrier gas include argon, air, and oxygen; S3. Use the atomic spectrum detector (3) to detect the Hg content at the outlet of the catalytic pyrolysis furnace (2), read the area of the peak spectrum diagram, and according to the linear relationship between the peak area and the Hg injection amount, obtain the quantitative detection result of the Hg content in the soil sample.

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