Heat tracing plasma sample introduction device and method

Abstract

The invention discloses a heat tracing plasma sample introduction device and method, and belongs to the technical field of analytical chemistry. In order to solve the problems of slow release of to-be-detected elements in a sample, complex operation and high energy consumption, the invention mainly adopts a method of arranging a heating plasma area in an evaporator, combining a heating unit and a plasma generation unit, and synchronously heating and carrying out plasma treatment on the sample in a reducing atmosphere. According to the invention, the to-be-detected element can be quickly and efficiently released, the sample pretreatment step is simplified, the detection sensitivity and efficiency are improved, the operation energy consumption is reduced, and the influence on the environment is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of analytical chemistry, and particularly relates to a heated plasma sample introduction device and method. Background Art

[0002] In recent years, the importance of element introduction technology has become increasingly prominent in the fields of chemical analysis, environmental monitoring, materials science, etc. Traditional element introduction methods often rely on complex reagents and cumbersome operation processes, which not only increase the experimental cost, but also pose higher requirements for the laboratory environment and the professional skills of operators.

[0003] Electrothermal Vaporization (ETV) technology rapidly introduces target elements into the spectral detection system in the form of vapor or atomic state by heating the sample to a high temperature in a very short time, so as to achieve sensitive quantitative analysis of trace and ultra-trace elements. However, this method may cause the co-export of other inorganic components, thus interfering with the elements to be measured. Controlling the temperature to reduce the evaporation of interfering substances usually slows down the evaporation rate of the elements to be measured, thereby affecting the sensitivity of the final detection. In addition, the cold area of the heating device may also affect signal transmission, resulting in a relatively low final transmission efficiency.

[0004] Chemical Vapor Generation (CVG) is a sample pretreatment and injection technology that converts target elements into volatile species through chemical reactions and transports them to the detector by carrier gas. The core of this method lies in the proper ratio of reducing agent, acidity and additives to convert the target elements from the liquid phase into the gas phase. This process not only helps to separate from the matrix, but also significantly improves the sensitivity and accuracy of detection. However, this method requires a large amount of chemical reagents, and not all elements can generate gas through chemical reactions, and the gas generation conditions of different elements vary significantly, resulting in relatively complex method development.

[0005] In addition, nebulization injection is a common introduction method. Its operation process is to first treat the sample with strong acid into a liquid, and then connect it to detection instruments such as ICP-MS and ICP-OES through a nebulizer to achieve high-sensitivity multi-element detection. However, the transmission rate of nebulization injection is generally low, and usually only less than 10% of the analytes can effectively reach the plasma center.

[0006] With the progress of technology, more and more new technologies have been developed to improve the efficiency and accuracy of element introduction. Although existing technologies, such as Laser Induced Breakdown Spectroscopy (LIBS) and X-ray Fluorescence Spectroscopy (XRF), perform well in rapid analysis and non-destructive testing, they still have deficiencies such as high requirements for sample pretreatment, many interference factors and complex operation. Summary of the Invention

[0007] The object of the present invention is to provide a heated plasma sample introduction device and method, which do not require the use of reagents, and can rapidly release the elements to be measured in the sample through the simultaneous action of heating and plasma under a reducing atmosphere, with low power consumption and low interference.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] A heated plasma sample introduction device includes an evaporator, a heating unit, a plasma generation unit, and a carrier gas source unit;

[0010] The evaporator includes an evaporation chamber, and a heated plasma region is provided in the evaporation chamber for containing the sample; the evaporator is provided with an inlet and an outlet, and the inlet is used for introducing the sample and a reducing atmosphere;

[0011] The heating unit is located in the heated plasma region of the evaporator and is used to heat the heated plasma region;

[0012] The plasma generation unit is used to ionize the gas in the heated plasma region of the evaporator to generate plasma;

[0013] The carrier gas source unit is connected to the inlet of the evaporator and is used to provide a reducing atmosphere, which is composed of a reducing gas and an inert gas.

[0014] Further, the evaporator is provided with one inlet shared by the sample and the reducing atmosphere or two separate inlets; the evaporator is further provided with an inlet for using air, and the inlet for using air and the inlet for using the reducing atmosphere are one inlet or two independent inlets.

[0015] Further, the material of the evaporator is quartz, ceramic, or other high-temperature resistant insulating materials.

[0016] Further, the heating unit is one of an electric heater, an electromagnetic heater, and a light radiation heater.

[0017] Further, the plasma generation unit is one of a dielectric barrier discharge device, a DC high-voltage plasma generation device, a glow discharge device, an arc generation device, a corona discharge device, a plasma jet device, a microwave plasma generation device, and a laser plasma generation device.

[0018] Further, the heating region of the heating unit and the plasma region generated by the plasma generation unit completely or partially overlap, and the overlapping part is the heated plasma region.

[0019] Furthermore, it also includes a sample boat for holding samples and placing them in the heating plasma zone of the evaporator; the shape of the sample boat is a boat-shaped, flat-plate-shaped, curved-plate-shaped or barrel-shaped structure, and the sample boat can be inserted or removed from the evaporation chamber of the evaporator, or directly embedded in the evaporation chamber; the material of the sample boat is ceramic, quartz, metal, platinum, graphite or other high-temperature resistant materials; when the sample boat is made of metal or graphite, it can be heated in conjunction with an electromagnetic heater, thereby improving the sample heating speed and efficiency.

[0020] A method for introducing a heated plasma sample, used in the above-mentioned device, comprises the following steps:

[0021] The sample is added to the heated plasma zone within the evaporator;

[0022] If the sample needs to be ashed, air is introduced into the evaporator, and the sample is heated, dried, and ashed by the heating unit to remove moisture and organic matter from the sample and discharge them;

[0023] If the sample does not need to be ashed or has been ashed, a reducing atmosphere consisting of a reducing gas and an inert gas is introduced into the evaporation chamber through the carrier gas source unit, the heating unit is turned on to heat the sample, and the plasma generating unit is turned on to generate plasma;

[0024] Under the simultaneous action of reducing atmosphere, heating and plasma, the elements to be measured in the sample are quickly brought out and exported.

[0025] Furthermore, the sample is a 0-1 mL liquid sample or a slurry sample, or a 0-1 g solid sample, and is added to the heated plasma zone in the evaporator through a sample boat or directly.

[0026] Furthermore, the theoretical heating temperature of the heating unit is 100-2000°C; during ashing, the heating unit is controlled to heat the sample to 100-500°C; when a reducing atmosphere is introduced, the heating temperature of the sample by the heating unit is 200-2000°C.

[0027] Furthermore, the reducing atmosphere is introduced at a flow rate of 300-1500 ml / min.

[0028] Furthermore, the reducing gas is one of hydrogen, ammonia, hydrocarbons, and carbon monoxide, the inert gas is one of argon and helium, and the volume concentration of the reducing gas in the reducing atmosphere is 1%-10%, preferably 1%-3%.

[0029] The beneficial effects achieved by the present invention are as follows:

[0030] 1. The device of the present invention has a simple overall structure and low power consumption, reducing equipment maintenance and operating costs. Using this device, the combined effects of heating and plasma can rapidly extract the element being analyzed. This is ineffective when using heating or plasma treatment alone. This significantly reduces the evaporation temperature of the element being analyzed in the sample, ensuring efficient extraction of the element.

[0031] 2. This method can rapidly extract the element being tested, converting it into atomic or aerosol form, which is then introduced into various spectral or mass spectrometric detection devices to achieve qualitative and quantitative analysis of the element. This method results in faster sample peak generation, narrower and higher signal intensity, improved detection accuracy and efficiency, and eliminates the need for complex pre-processing, simplifying the operational process.

[0032] 3. The present invention achieves local selective release of samples by adjusting the area where plasma acts, thereby improving the flexibility of sample analysis.

[0033] 4. The present invention can perform drying and ashing in air, and can also assist in releasing the elements to be tested in a reducing atmosphere, meeting various analytical requirements.

[0034] 5. The sample introduction technology of the present invention does not require the use of reagents, simplifies the operation steps, and enables users to directly inject samples, significantly reducing the impact of the experiment on the environment and the skill requirements of the operator. At the same time, it relies on a simplified instrument structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of a heated plasma sample introduction device provided by an embodiment of the present invention.

[0036] Figure 2 This is a graph showing the relationship between the current size and the element release signal in the experiment.

[0037] Figure 3 This is a graph showing the relationship between temperature and element release signals in the experiment.

[0038] Figure 4 This is a graph showing the relationship between the hydrogen content and the element release signal in the experiment.

[0039] Figure 5 This is a graph showing the relationship between the carrier gas flow rate and the element release signal in the experiment.

[0040] Figure 6 This is a schematic structural diagram of a heated plasma sample introduction device provided in Example 1.

[0041] Figure 7 This is a graph showing the release of cadmium at different temperatures during the experiment in Example 1.

[0042] Figure 8 It is a schematic structural diagram of a heat - traced plasma sample introduction device provided by Example 2.

[0043] Figure 9 It is a schematic structural diagram of a heat - traced plasma sample introduction device provided by Example 3.

[0044] Figure 10 It is a schematic structural diagram of a heat - traced plasma sample introduction device provided by Example 4. Specific embodiments

[0045] To make the technical features and advantages or technical effects in the above - mentioned technical solutions of the present invention more obvious and understandable, the following will be described in detail through examples, instances and drawings.

[0046] An embodiment of the present invention provides a heat - traced plasma sample introduction device, the structure of which is as Figure 1 shown. The device includes an evaporator 1, a heating unit 2, a plasma generation unit 3 and a sample boat 4. The evaporator 1 contains an evaporation chamber, and a heating plasma region 1a is provided in the evaporation chamber for containing the sample to be heated and excited. The heating unit 2 is located in the heating plasma region 1a of the evaporator 1 and surrounds the outside of the evaporator 1, responsible for providing the necessary heating effect. The plasma generation unit 3 consists of two metal electrodes 3a (metal ring electrodes are used in this embodiment), and the electrodes 3a are respectively arranged at both ends of the heating plasma region 1a and surround the outside of the evaporator 1 for generating plasma. The sample boat 4 is used to hold the sample and can be placed at the position of the heating plasma region 1a of the evaporator 1. The left inlet and outlet of the evaporator 1 are used to put in and take out the sample boat 4, and after the sample boat is put in, it can be sealed with a plug 1b. An air pump 5 and a carrier gas source 6 are arranged near the inlet and outlet of the evaporator 1, which are used to introduce air and reducing atmosphere respectively, and the opposite end of the inlet and outlet of the evaporator 1 is connected with an atomic fluorescence detection device 7 for detecting the elements to be measured in the sample.

[0047] During the operation, first, 20 μL of liquid sample or 100 μL of slurry sample is added into the sample boat 4. Subsequently, the plug 1b at the sample inlet and outlet on the left side of the evaporator 1 is opened, the sample boat 4 is placed at the position of the heated plasma region 1a, and the plug 1b is covered. At this time, the air pump 5 is started to introduce air, and the temperature of the evaporator 1 is controlled to 300 °C by the heating unit 2 and maintained at this temperature for 2 minutes to complete the drying and ashing treatment of the sample. Next, the air pump 5 is closed, the carrier gas source 6 is opened, the flow rate is set to 500 ml / min, and the gas in the sample boat 4 is purged for 1 minute to displace the air in the evaporator 1. Then, the temperature of the heating unit 2 is raised to 600 °C, and the plasma generation unit 3 is started to form plasma in the heated plasma region 1a between the two metal electrodes 3a. Under the dual action of heating and plasma, the elements to be measured (such as As) in the sample in the sample boat 4 are rapidly released, exported in gaseous form, and enter the atomic fluorescence detection device 7 for qualitative and quantitative analysis, thus realizing the rapid analysis of the elements to be measured.

[0048] The following analyzes the element release behavior and mechanism in the heated plasma sample introduction device through experiments:

[0049] 1. Analysis of plasma release conditions:

[0050] For dielectric barrier discharge devices, DC high-voltage plasma generation devices, glow discharge devices, arc generation devices, corona discharge devices, etc., during the dielectric barrier discharge process, the magnitude of the discharge current usually affects the density of plasma in the discharge region and the generation rate of active species (such as electrons, ions, and free radicals). As the discharge current increases, the discharge power synchronously increases, which helps to improve the generation rate of active species in the plasma. Theoretically, this enhancement effect may improve the release efficiency of the elements to be measured and the detection signal intensity. However, within the range of discharge current set in this experiment, although the current increases, the actual detection signal does not show a significant change, as Figure 2 shown. The experimental results show that when the discharge current range (for example, greater than or equal to 0.1 A) is reached, the generation of plasma can be achieved, and this process has tended to be saturated or reached a stable state. The generation amount of active species has approached the plateau period, and a stable and good release effect of the elements to be measured can be achieved. Further increasing the discharge current will not significantly improve the release performance. For plasma jet devices, microwave plasma generation devices, laser plasma generation devices, etc., as long as the minimum injection power requirement for macroscopic plasma generation (usually above 5 W) can be achieved, the required plasma concentration of the system can be achieved.

[0051] 2. Analysis of temperature conditions:

[0052] During the experiment, it was found that the release signal is not sensitive to changes in plasma intensity, but is highly sensitive to the temperature during the release process. The theoretical heating temperature of the heating unit is 100-2000℃. When a reducing atmosphere is introduced, the heating temperature of the heating unit for the sample is 200-2000℃. For the released elements, the temperature is usually not higher than 1000℃. Taking cadmium as an example, under the same plasma conditions, different temperatures show significant differences in its release effect. The specific results are as follows: Figure 3 and Figure 7 Experiments show that at room temperature, cadmium release is low; as the temperature rises, the release efficiency increases significantly. As the temperature approaches 300°C, cadmium release becomes more complete, indicating that temperature is a key factor affecting cadmium release efficiency.

[0053] 3. Analysis of the proportion of reducing atmosphere components:

[0054] In the absence of reducing gas and only pure argon, the release signal generated during the discharge process is weak. As the volume concentration of hydrogen increases from 1% to 3%, the release signal intensity increases significantly, indicating that reducing hydrogen plays a key role in promoting the release of the elements to be measured in the sample. However, when the hydrogen concentration exceeds a certain threshold, the signal intensity shows a downward trend, such as Figure 4 A possible explanation for this change is that high hydrogen concentrations may inhibit the dielectric barrier discharge process to a certain extent, thereby weakening the plasma excitation ability and resulting in a decrease in release efficiency. When the volume concentration of reducing gas in the reducing atmosphere is between 1% and 10%, the release signal intensity meets general requirements. It reaches its highest intensity in the 1%-3% range, with 2% being the relatively optimal condition.

[0055] 5. Carrier gas (reducing atmosphere) flow analysis:

[0056] In the spectral detection system, the carrier gas plays a vital role. Its main function is to effectively transport the target elements from the sample area to the analysis area to achieve efficient detection. The carrier gas flow rate directly affects the speed at which the measured elements enter the analysis area and their concentration distribution, thus having a decisive impact on the signal intensity and repeatability. The experimental results are as follows Figure 5 The results show that a significant carryover effect is achieved after the carrier gas flow rate reaches 300 mL / min. The cadmium signal intensity reaches its peak at approximately 600 mL / min, and further increases in the carrier gas flow rate lead to signal attenuation. Considering the release signal intensity and effective carrier gas utilization, a carrier gas flow rate range of 300-1500 mL / min is selected. 600 mL / min was determined to be the optimal flow rate for this experiment, balancing the need for increased signal intensity with maintaining an appropriate concentration.

[0057] 3. Mechanism Analysis:

[0058] To deeply study the specific mechanism of temperature, reducing atmosphere, and discharge in this device, the following experiments were designed:

[0059] 50 μL of 1000 ppm cadmium standard solution was separately dropped onto three quartz wafers and dried, labeled as Samples 1, 2, and 3. Sample 1 was only dried; Sample 2 was heat-treated in a reducing atmosphere after drying. The sample was placed in a 2% hydrogen-argon mixed gas, heated to 300 °C and maintained for 40 seconds; Sample 3 was subjected to heat-assisted discharge treatment after drying. The treatment conditions were the same as those of Sample 2, but discharge treatment was carried out in the last 10 seconds of the heat treatment.

[0060] Subsequently, X-ray photoelectron spectroscopy (XPS) was used to perform the first surface detection on the three samples. Then, each sample was sputtered with argon for 60 seconds to remove the surface layer and perform the second detection. Finally, argon sputtering treatment was carried out again for 60 seconds and the third detection was performed. The experimental results are shown in Table 1.

[0061] Table 1 XPS Detection Results

[0062]

[0063] For Sample 1, the sample was only treated by drying the cadmium solution on the surface of the quartz wafer, and the surface cadmium-oxygen ratio was 81. After 60 seconds and 120 seconds of sputtering detection respectively, the second and third detection results showed that the surface cadmium-oxygen ratios were 8 and 5 respectively.

[0064] For Sample 2, after drying the cadmium solution and heat-treating in a reducing atmosphere and then cooling, it was immediately detected. Compared with the binding energy of the surface layer of Sample 1, the binding energy of Sample 2 decreased slightly, indicating that the chemical state of the surface cadmium changed, transferring from a high valence state to a low valence state. The surface cadmium-oxygen ratio of Sample 2 was 90, which increased compared with Sample 1; the subsequent second and third detection results showed that the cadmium-oxygen ratio continued to rise. This phenomenon indicates that under the combined action of hydrogen and temperature, cadmium tends to migrate to the surface and segregation occurs.

[0065] For Sample 3, after heat treatment in a reducing atmosphere and discharge treatment, no cadmium signal was detected. This indicates that under the triple action of reducing atmosphere, temperature, and discharge, cadmium was significantly released. This result provides key evidence for studying the behavior mechanism of cadmium under different conditions, indicating that the reducing atmosphere and temperature affect the surface state of cadmium, which may promote its migration to the surface and provide a prerequisite for release, while the discharge process is the decisive factor for release.

[0066] The following are specific application examples for the specific implementation of the structure of the device proposed by the present invention. Among them, the evaporator will be presented in the form of a quartz evaporator or an evaporation chamber, etc., the heating unit will be presented in the form of a heating wire, an electromagnetic heater, a ceramic heater, etc., the plasma generation unit will be presented in the form of internal and external electrodes, a plasma jet generator, a laser, etc., and the sample boat will be presented in different structural shapes. All of these belong to the specific implementation manners of the composition of these devices and should be understandable.

[0067] Example 1

[0068] Figure 6 FIG. is a schematic structural diagram of a heat - accompanied plasma sample introduction device provided for this example. The device is mainly composed of the following parts: a quartz evaporator 11, an air inlet 111, an air outlet 112, a sample inlet / outlet 113, an inner electrode protective sleeve 114, a heating wire 12, an outer electrode 13, an inner electrode 14, an atomic fluorescence spectrometer 15, an annular sample boat 16, and a sealing plug 17. Among them, the main body of the quartz evaporator 21 is a cylindrical quartz tube. One end of it is provided with a sample inlet / outlet 213 for the annular sample boat 26 to freely enter and exit. After the sample boat is placed, the sample inlet / outlet 213 needs to be covered with a sealing plug 27 to prevent air leakage. An air inlet 212 is arranged beside the sample inlet / outlet of the quartz evaporator for carrier gas or air to enter the evaporator. The other end of the cylindrical quartz tube is bent and gradually narrowed to form an air outlet 212. Another coaxial welded quartz tube is located in the center of the cylindrical quartz tube to form an inner electrode protective sleeve 214. A metal conductive layer is coated on the outside of the quartz tube to form an outer electrode 23 for discharging between the outer electrode and the inner electrode 24 to generate dielectric barrier discharge. The heating wire 22 is wound outside the outer electrode but is not in direct contact with the outer electrode. The whole device is connected to the atomic fluorescence spectrometer 25 through the air outlet 212 for qualitative and quantitative analysis of elements.

[0069] The operation process of this device is as follows:

[0070] First, evenly coat the inner surface of the annular sample boat with a liquid or slurry sample. Subsequently, place the annular sample boat into the quartz tube evaporator through the sample inlet and outlet, ensuring that the sample is located in the area between the inner and outer electrodes. Pass air through the air inlet and start heating the heating wire to dry the sample. After drying, further increase the temperature of the heating wire to ash the sample, thereby effectively removing the organic matrix. After ashing is completed, stop the air supply, and after the system cools to the set temperature, introduce a reducing carrier gas through the air inlet to displace the system atmosphere. Subsequently, maintain the heating wire at a high temperature to ensure that the ambient temperature meets the requirements of subsequent processing. Then, start the high-voltage high-frequency power supply to form a dielectric barrier discharge between the inner and outer electrodes, generating plasma. Under the synergistic action of high temperature and plasma, the elements to be measured in the sample are rapidly released and transported to the atomic fluorescence spectrometer to achieve qualitative and quantitative analysis of the target elements. The parameters involved in this process are shown in Table 2.

[0071] Table 2

[0072] Process Heating Temperature (°C) Time (s) Atmosphere Plasma Power Drying 120 120 600 mL / min Air / Ashing 300 600 600 mL / min Air / Purge / 30 <![CDATA[600mL / min 2%H2 / Ar]]> / Preheating 300 120 <![CDATA[600mL / min 2%H2 / Ar]]> / Release 300 10 <![CDATA[600mL / min 2%H2 / Ar]]> 10W

[0073] A specific implementation step is as follows:

[0074] Evenly coat the inner side of the annular sample boat with a suspension prepared from 100 μL of rice sample, and then insert the sample boat into the quartz evaporator, ensuring that it is located between the inner and outer electrodes. Pass air through the air inlet, start the heating wire and keep the temperature at 120 °C for 2 minutes to complete sample drying. Subsequently, increase the temperature of the heating wire to 300 °C and keep it for 10 minutes to complete sample ashing and matrix removal. After stopping the air injection, inject 2% argon-hydrogen gas at 600 ml / min into the evaporator for purging for 30 seconds. Keep the temperature of the heating wire at 300 °C, connect the high-voltage high-frequency power supply of the inner and outer electrodes to form a dielectric barrier discharge and generate plasma. At this time, the cadmium element in the annular sample boat is rapidly released and enters the atomic fluorescence spectrometer with the carrier gas for analysis. The analysis results are shown in Table 3. The detection limit of cadmium for this device is 0.05 μg / kg, and the relative standard deviation of repeated measurements is less than 8%. The detection results of the rice sample and the reference material are both within the expected range, and there is no significant difference in the results.

[0075] Table 3

[0076]

[0077] Example 2

[0078] Figure 8Schematic structural diagram of a heat tracing plasma sample introduction device provided for this example. The device mainly consists of the following parts: evaporation chamber 21, gas outlet 211, sealing cover 22, plasma jet generator 23, air inlet 231, jet outlet 232, electromagnetic heater 24, sample boat 25, and atomic absorption spectrometer 26. Among them, the evaporation chamber 21 is a ceramic cavity provided with a gas outlet 211. The upper part of the ceramic cavity is sealed by a sealing cover 22 made of polytetrafluoroethylene material. A plasma jet generator 23 is installed above the sealing cover, and the jet generator is equipped with an air inlet 231 for connecting an air or carrier gas source. A jet outlet 232 is provided below the jet generator, and a tungsten steel sample boat 25 is placed below the outlet. An electromagnetic induction heater is installed outside the ceramic evaporator below the sample boat for heating the metal sample. The gas outlet 211 of the evaporator is connected to the sample inlet of the atomic absorption spectrometer to facilitate the atomic absorption spectrometer to perform elemental analysis on the outlet gas.

[0079] The operation process of this device is as follows:

[0080] Place the sample in the tungsten steel sample boat and place it at the bottom of the ceramic evaporation chamber. With the sealing cover open, start the electromagnetic heater to heat the tungsten steel sample boat, and complete the drying and ashing treatment of the sample in an air atmosphere to remove the organic matrix therein. After ashing is completed, turn off the heater to allow the system to cool naturally, then cover the sealing cover and ensure that the evaporation chamber is airtight. Pass a reducing atmosphere through the air inlet to displace the internal atmosphere of the cavity. After displacement is completed, start the electromagnetic heater again to heat the tungsten steel sample boat to the set temperature. At the same time, start the jet device to spray the reducing atmosphere onto the sample surface in the form of a plasma jet. Under the combined action of high temperature and plasma, the metal elements to be measured in the sample are rapidly released and introduced into the atomic absorption spectrometer with the carrier gas to achieve qualitative and quantitative analysis of the metal elements. The reducing atmosphere used is a mixed gas composed of 1% hydrocarbon gas and 99% argon. The parameters involved in this process are shown in Table 4.

[0081] Table 4

[0082] Process Heating Temperature (°C) Time (s) Atmosphere Plasma Power Drying Ashing 300 180 Air / Purge / 120 2 L / min 1% Methane and 99% Argon / Preheating 550 300 2 L / min / ​ 550 10 ​ 25W

[0083] A specific implementation step is as follows:

[0084] Add 50 μL of blood sample onto the metal sample boat, and place the sample boat at the bottom of the ceramic evaporation chamber. Without covering the upper lid, heat the metal sample boat to 300 °C using an electromagnetic heater and hold for 3 minutes to complete the drying and ashing of the sample. After cooling, cover with the sealing lid, and input a mixture of 1% methane and 99% argon with a flow rate of 2 L / min through the air inlet of the jet generator and purge for 2 minutes. Then, raise the temperature of the sample boat to 550 °C using the electromagnetic heater and start the plasma jet. The plasma jet formed in the reducing atmosphere is sprayed onto the sample, and under the action of heating and plasma, the elements to be measured in the sample are rapidly released. The released elements enter the atomic absorption spectrometer with the carrier gas for detection, and the detection results are shown in Table 5. The detection limit of lead for this device is 0.8 μg / L, and the relative standard deviation of repeated measurements is less than 9%. The detection results of blood samples and reference materials are all within the expected range and there is no significant difference.

[0085] Table 5

[0086]

[0087] Example 3

[0088] ​ The structure diagram of a heated plasma sample introduction device provided for this example. The main components of this device include: an evaporation chamber 31, an air outlet 311, an air inlet 312, a sealing lid 32, a laser 33, a ceramic heater 34, a sample boat 35, and an inductively coupled plasma spectrometer 36. Among them, the evaporation chamber 31 is a cavity made of polytetrafluoroethylene, provided with a gas outlet 311 and an air inlet 312, and its upper opening facilitates the taking and placing of the sample. The upper part of the evaporation chamber is sealed by the sealing lid 32, and the sealing lid is made of polytetrafluoroethylene material. A laser source 33 is installed on the upper part of the sealing lid in the direction of the laser beam irradiating the sample boat ३५. The bottom of the evaporation chamber is equipped with a ceramic heater 34, and a sample boat 35 made of quartz is placed above the heater to quickly heat the sample. The air inlet of the evaporation chamber can be connected to an air or carrier gas source, and the air outlet 311 of the evaporation chamber is connected to the sample inlet of the inductively coupled plasma spectrometer to facilitate elemental analysis of the outlet gas.

[0089] The operation process of this device is as follows:

[0090] Place the sample in a metal sample boat and place it on the ceramic heater in the evaporation chamber. Open the upper cover of the evaporation chamber, start the ceramic heater to heat the metal sample boat, and complete the drying and ashing of the sample under air atmosphere conditions to remove the organic matrix and achieve preliminary purification. After the sample ashing is completed and it cools naturally to the set temperature, close the upper cover and ensure the evaporation chamber is sealed. Subsequently, introduce a reducing atmosphere through the inlet to displace the air atmosphere in the chamber and form a reducing environment. After the atmosphere displacement is completed, continue to raise the temperature of the metal sample boat, and at the same time start the laser to irradiate the sample surface to generate plasma. Under the synergistic effect of high temperature and laser-induced plasma, the metal elements to be measured in the sample are rapidly released and transported to the inductively coupled plasma spectrometer with the carrier gas to achieve qualitative and quantitative analysis of the elements. The reducing atmosphere used is a mixed gas composed of 1% hydrogen and 99% argon. The parameters involved in this process are shown in Table 6.

[0091] Table 6

[0092] ​ ​ ​ ​ ​ ​ 400 300 ​ / ​ / 120 <![CDATA[500mL / min 1%H2 / Ar]]> / ​ 400 200 <![CDATA[500mL / min 1%H2 / Ar]]> / ​ 400 10 <![CDATA[500mL / min 1%H2 / Ar]]> 5W

[0093] A specific implementation step is as follows:

[0094] Add 100 mg of the sample to the metal sample boat and place the sample boat on the ceramic heater. Heat the sample to 400 °C through the ceramic heater and hold for 5 minutes to complete the drying and ashing of the sample. Then cover the sealing cover, input a mixed gas of 1% hydrogen and 99% argon through the inlet at a flow rate of 500 mL / min for purging. Subsequently, adjust the temperature of the ceramic heater to 400 °C and start the laser to irradiate the sample to prompt the rapid release of cadmium elements in the sample. The released cadmium elements enter the inductively coupled plasma spectrometer with the carrier gas for quantitative analysis, and the analysis results are shown in Table 7. The detection limit of cadmium by this device is 1 μg / kg, and the relative standard deviation of repeated measurements is less than 8%. The detection results of rice samples and reference materials are all within the expected range and there is no significant difference.

[0095] Table 7

[0096]

[0097] Example 4

[0098] ​Schematic diagram of the structure of a heat - traced plasma sample introduction device provided for this example. The main components of the device include: a five - way quartz evaporator 41, an air outlet 411, an air inlet 412, a sample inlet / outlet 413, an infrared radiation heating tube 42, a graphite tube 43, a continuous sample introduction boat 44, and an inductively coupled plasma mass spectrometry detector 45. The main structure of the device is a five - way quartz tube 41. Among them, two opposite pipelines are respectively the air inlet and the electrode lead - in port, and the other two opposite pipelines are the sample inlet / outlet. The upward pipeline is the gas outlet. Two graphite tube - shaped electrodes are inserted into the two opposite air inlets of the quartz evaporator, and a sealing device is used to ensure the sealing of the interface between the graphite tube and the quartz tube. The inside of the graphite tube is a gas inlet channel. When the two graphite electrodes are connected to a DC high - voltage power supply, plasma can be generated between the electrodes. By adjusting the discharge current of the high - voltage power supply, glow discharge or arc discharge modes can be achieved. A continuous sample introduction boat 44 is placed inside the sample inlet / outlet 413, and the sample inlet / outlet is closed. Samples are placed at intervals inside the continuous sample introduction boat. As the sample boat moves, the samples will be successively introduced into the heated plasma region of the five - way quartz evaporator for the release of the substances to be measured. The infrared radiation heating tube 42 is located above the five - way quartz evaporator and is used to heat the samples inside the evaporator. The upward outlet 411 of the five - way quartz evaporator is connected to an inductively coupled plasma mass spectrometer, which is convenient for introducing the released elemental gas into the mass spectrometer for analysis.

[0099] The operation process of this device is as follows:

[0100] Place the samples on the continuous sample introduction boat at intervals and insert them into the quartz evaporator through the sample inlet / outlet to ensure that the first sample is positioned in the heated plasma region between the two graphite electrodes. After completing the sample insertion, close the sample inlet / outlet to form a closed system. Pass an air atmosphere into the evaporator through the graphite tube inserted into the air inlet and start the infrared radiation heating tube to heat the samples to complete the drying and ashing processes, removing the volatile components and matrix interferences in the samples. After the drying and ashing are completed, stop heating and let it cool naturally. Subsequently, pass a reducing atmosphere through the graphite tube to displace the atmosphere inside the evaporator and construct a reducing environment. After the atmosphere displacement is completed, raise the temperature of the infrared radiation heating tube again to keep the samples at a high temperature state. At the same time, start the high - voltage power supply to supply power to the two graphite electrodes and adjust the discharge current to excite and form a stable plasma. Under the combined action of high temperature and plasma, the elements to be measured in the samples are rapidly released and flow through the air outlet with the carrier gas and enter the inductively coupled plasma mass spectrometer (ICP - MS) for qualitative and quantitative analysis. The reducing atmosphere used is a mixed gas composed of 3% carbon monoxide and 97% helium. The parameters involved in this process are shown in Table 8.

[0101] Table 8

[0102]

[0103] A specific implementation step is as follows:

[0104] Prepare 3 soil samples, each weighing 50 mg. Prepare a suspension for each sample and add them dropwise at intervals onto a continuous sampling boat. Insert the continuous sampling boat into the quartz evaporator through the inlet and outlet, ensuring that the first sample stays between two graphite electrodes inside the quartz evaporator. Connect the gas outlet of the five-way quartz evaporator to the inlet of the inductively coupled plasma mass spectrometer. Control the temperature of the sample through an infrared radiation heater. First, introduce air and heat it to 300 °C to dry and ashing the sample. Then, introduce a mixture of 3% carbon monoxide and 97% helium and maintain it for 120 seconds. Subsequently, raise the temperature to 600 °C and turn on the discharge power supply of the electrodes to generate plasma between the electrodes. The arsenic element in the sample is rapidly released and enters the inductively coupled plasma mass spectrometer with the carrier gas for detection. After stopping the discharge and heating, move the sampling boat to the next sample position manually or electronically, and repeat the above steps of heating, gas introduction, and discharge to complete the continuous measurement of subsequent samples. The measurement results are shown in Table 9. The detection limit of arsenic by this device is 0.1 μg / L, and the relative standard deviation of repeated measurements is less than 9%. The detection results of the reference materials are all within the specified range and there is no significant difference.

[0105] Table 9

[0106]

[0107] Although the present invention has been disclosed above with examples and instances, it is not intended to limit the present invention. Appropriate modifications or equivalent replacements made by those of ordinary skill in the art to the technical solutions of the present invention shall all be covered within the protection scope of the present invention. The protection scope of the present invention shall be subject to that defined by the claims.

Claims

1. A heat tracing plasma sample introduction device, characterized in that, It includes an evaporator, a heating unit, a plasma generation unit, and a carrier gas source unit; The evaporator includes an evaporation chamber, and a heating plasma region is provided in the evaporation chamber for containing a sample; the evaporator is provided with an inlet and an outlet, and the inlet is used for introducing the sample and a reducing atmosphere; The heating unit is located in the heating plasma region of the evaporator and is used for heating the heating plasma region; The plasma generation unit is used for ionizing the gas in the heating plasma region of the evaporator to generate plasma; The carrier gas source unit is connected to the inlet of the evaporator and is used for providing a reducing atmosphere, which is composed of a reducing gas and an inert gas.

2. The heat tracing plasma sample introduction device according to claim 1, characterized in that, The evaporator is provided with one inlet shared by the sample and the reducing atmosphere or two separate inlets; the evaporator is further provided with an inlet for using air, and the inlet for using air and the inlet for using the reducing atmosphere are one inlet or two independent inlets.

3. The heat tracing plasma sample introduction device according to claim 1, wherein The heating unit is one of an electric heater, an electromagnetic heater, and a light radiation heater; the plasma generation unit is one of a dielectric barrier discharge device, a DC high-voltage plasma generation device, a glow discharge device, an arc generation device, a corona discharge device, a plasma jet device, a microwave plasma generation device, and a laser plasma generation device.

4. The heating plasma sample introduction device according to claim 1, characterized in that, It further includes a sample boat for containing the sample and placing it in the heating plasma region of the evaporator; the shape of the sample boat is a boat shape, a flat plate shape, an arc plate shape, or a barrel shape; the sample boat can be inserted into or taken out of the evaporation chamber of the evaporator, or directly embedded in the evaporation chamber.

5. The heating plasma sample introduction device according to claim 4, characterized in that, The material of the evaporator is quartz or ceramic; the material of the sample boat is ceramic, quartz, metal, platinum, or graphite.

6. A heat tracing plasma sample introduction method, for the heat tracing plasma sample introduction device according to any one of claims 1-5, characterized in that, It includes the following steps: Adding the sample into the heating plasma region in the evaporator; If the sample needs to be ashed, air is introduced into the evaporator, and the sample is heated and dried and ashed by the heating unit to remove the moisture and organic matter in the sample and discharge them; If the sample does not need to be ashed or the ashing has been completed, a reducing atmosphere composed of a reducing gas and an inert gas is introduced into the evaporation chamber through the carrier gas source unit, the heating unit is turned on to heat the sample, and the plasma generation unit is turned on to generate plasma; Under the simultaneous action of the reducing atmosphere, heating, and plasma, the elements to be measured in the sample are quickly carried out and exported.

7. The heating plasma sample introduction method according to claim 6, characterized in that, The sample is a 0-1 mL liquid sample or a slurry sample, or a 0-1 g solid sample, and is added to the heating plasma region in the evaporator through the sample boat or directly.

8. The heat tracing plasma sample introduction method according to claim 6, wherein The theoretical heating temperature of the heating unit is 100-2000 °C; during ashing, the heating unit is controlled to heat the sample to 100-500 °C; when the reducing atmosphere is introduced, the heating temperature of the heating unit for the sample is 200-2000 °C.

9. The heat tracing plasma sample introduction method according to claim 6, characterized in that The flow rate of the introduced reducing atmosphere is 300-1500 ml / min.

10. The heating plasma sample introduction method according to claim 6, characterized in that, The reducing gas is one of hydrogen, ammonia, hydrocarbons, and carbon monoxide, the inert gas is one of argon and helium, and the volume concentration of the reducing gas in the reducing atmosphere is 1%-10%.

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