A pressure ring device for direct measurement of atmospheric particles carried by filter membrane using total reflection X-ray fluorescence spectrometer

Abstract

The present invention relates to a pressure ring device for directly measuring atmospheric particles carried by filter membranes with a total reflection X-ray fluorescence spectrometer, comprising a pressure ring component, a sample tray and a sample rack; the surface of the sample tray is higher than the sample rack; the pressure ring component cooperates with the sample rack to tighten the filter membrane to be measured on the surface of the sample tray. The beneficial effects of the present invention are as follows: the present invention can quickly make the surface of the filter membrane flat and realize total reflection of X-rays, so that the elemental composition of atmospheric particles carried by the filter membrane can be directly and quickly analyzed using TXRF technology, and the analysis time is shortened from the three hours required for the previous transfer membrane sample preparation analysis to 10 minutes, which greatly improves the efficiency, reduces the work intensity and analysis cost, and because the sample preparation and analysis are non-destructive, the precious atmospheric particles carried by the filter membrane can be preserved.

Description

Technical Field

[0001] The present invention relates to the fields of chemical analysis and environmental monitoring, and particularly to a pressing ring device for keeping an air filter membrane flat so as to directly measure the elemental composition of atmospheric particles carried by the filter membrane by total reflection X-ray fluorescence spectrometer (TXRF). Background Art

[0002] At present, the air quality of 30% of the key environmental protection cities and 17% of the prefecture-level cities in China fails to meet the national secondary standard. Atmospheric particulate matter represented by PM2.5 has become one of the biggest factors threatening the lives and health of Chinese people. In addition to measuring the content of particulate matter in the atmosphere, it is also necessary to quickly analyze the elemental composition of atmospheric particles carried by air filter membranes, so as to judge the potential toxicity of atmospheric particles and provide clues for determining pollution sources.

[0003] At present, there are mainly three methods for measuring the elemental composition of atmospheric particulate matter, inductively coupled plasma mass spectrometry (ICP-MS), X-ray fluorescence spectrometry (XRF), and total reflection X-ray fluorescence spectrometry (TXRF). ICP-MS has high measurement accuracy, but it is necessary to first quantitatively dissolve atmospheric particulate matter and then convert the dissolved solution into plasma; although X-ray fluorescence spectrometry (XRF) can directly measure atmospheric particles carried by air filter membranes, because the incident X-ray angle of this method is large and the noise signal is strong, the sensitivity of this method is low and it cannot well meet the needs of air pollution monitoring. The incident angle of total reflection X-ray fluorescence spectrometry is very small, about 0.1 degree, and almost all of the X-rays are reflected, so the noise background drops by about 3 orders of magnitude, and the content of 10 to 20 elements in atmospheric particulate matter can be analyzed, and the lowest absolute detection limit is in the <ng level (elements with atomic number greater than K). When analyzing atmospheric particles carried by filter membranes, the existing TXRF measurement method has high requirements for the flatness of samples, otherwise it is difficult to achieve total reflection of X-rays. Therefore, TXRF requires film transfer, that is, stripping atmospheric particles from the air filter membrane, chemically dissolving them, and dropping them on a quartz sample disk. The process of film transfer is time-consuming, laborious, costly, and errors will be introduced due to factors such as dissolution efficiency and impurities. Some air pollution monitoring and analysis work has urgent time limits, so the existing TXRF technology is not commonly used for the analysis of atmospheric particulate matter. The analysis of atmospheric particles carried by filter membranes using ICP-MS and the existing TXRF methods belongs to destructive analysis methods and the samples cannot be preserved.

[0004] At present, the national standard polytetrafluoroethylene (PTFE) air filter membrane (diameter 47mm) is uniformly used in the domestic atmospheric environment monitoring system. This filter membrane is relatively soft and is prone to curling and deformation when placed on the sample stage, being uneven and unable to perform TXRF analysis.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a pressure ring device for directly measuring the atmospheric particles on the filter membrane with a total reflection X-ray fluorescence spectrometer in view of the defects existing in the preparation of the existing TXRF analysis filter membrane-carried atmospheric particulate matter samples, so that the air filter membrane sample carrying atmospheric particulate matter can be stably and flatly fixed on the sample plate to achieve total reflection of X-rays, thereby greatly accelerating the sample analysis operation speed and reducing costs, so that the TXRF rapid analysis technology can be used for daily analysis and monitoring of atmospheric particulate matter and retaining samples.

[0007] The technical solution of the present invention is as follows:

[0008] A pressure ring device for directly measuring atmospheric particles carried by a filter membrane by a total reflection X-ray fluorescence spectrometer comprises a pressure ring component, a sample tray and a sample rack; the surface of the sample tray is higher than the sample rack; the pressure ring component cooperates with the sample rack to tighten the filter membrane to be measured on the surface of the sample tray.

[0009] Furthermore, in the above-mentioned pressure ring device for directly measuring atmospheric particles carried by the filter membrane by the total reflection X-ray fluorescence spectrometer, the pressure ring component is a steel pressure ring, and the sample rack is provided with a magnet block that can attract the steel pressure ring so that it presses the filter membrane to be measured onto the sample rack. The magnetism thereof is moderate, which is sufficient to flatten the air filter membrane and can easily remove the pressure ring component.

[0010] Furthermore, in the above-mentioned pressure ring device for directly measuring atmospheric particles carried by filter membranes using a total reflection X-ray fluorescence spectrometer, there are multiple magnet blocks, which are evenly arranged on the sample rack.

[0011] Furthermore, in the above-mentioned pressure ring device for directly measuring atmospheric particles carried by filter membranes using a total reflection X-ray fluorescence spectrometer, a concave hole is provided on the sample rack; and the magnet block is fixed in the concave hole.

[0012] Furthermore, in the above-mentioned pressure ring device for directly measuring atmospheric particles carried by filter membrane using total reflection X-ray fluorescence spectrometer, the magnet block is fixed to the corresponding position of the sample holder by epoxy resin.

[0013] Furthermore, in the above-mentioned pressure ring device for directly measuring the atmospheric particles carried by the filter membrane by the total reflection X-ray fluorescence spectrometer, as another option, the material of the pressure ring component has uniform and appropriate magnetism, and its magnetism is moderate enough to flatten the air filter membrane and make it easier to remove the pressure ring component. At least part of the sample holder is made of ferromagnetic material that can cooperate with the pressure ring component.

[0014] Furthermore, in the above-mentioned pressure ring device for directly measuring atmospheric particles carried by filter membranes using a total reflection X-ray fluorescence spectrometer, the sample disk is a quartz disk, and the elevation difference between the upper surface of the quartz disk and the sample rack is 0.5-3 mm.

[0015] The beneficial effects of the present invention are as follows:

[0016] The present invention can make the surface of the filter membrane close to the surface of the sample disk and keep it flat to achieve total reflection of X-rays. Therefore, the elemental composition of atmospheric particulate matter carried on the filter membrane can be directly and quickly analyzed by TXRF technology. The analysis time is about 10 minutes, which saves about two hours of digestion and membrane transfer time, greatly improves efficiency, reduces work intensity and analysis costs, and because sample preparation and analysis are non-destructive, precious atmospheric particulate matter samples carried on the filter membrane can be preserved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a schematic structural diagram of a pressure ring device used for directly measuring atmospheric particles carried by a filter membrane using a total reflection X-ray fluorescence spectrometer.

[0018] Figure 2 A bar graph showing the results of the detection and pollution source analysis of atmospheric particulate matter collected from the same batch of samples collected in Beijing during the same period of time using the TXRF analysis technology supported by the technical solution of this patent application and the ICP-MS analysis technology with the highest accuracy currently available.

[0019] In the above drawings, 1, pressure ring component; 2, sample plate; 3, sample rack; 4, magnet block; 5, filter membrane. DETAILED DESCRIPTION

[0020] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0021] TXRF analysis technology is more sensitive than XRF, but due to the strict requirements on the surface flatness of the sample, the current TXRF technology cannot directly measure the atmospheric particulate matter carried by the filter membrane. The purpose of the present invention is to design a device that can stably and evenly fix the air filter membrane sample carrying atmospheric particulate matter on the sample plate to achieve total reflection of X-rays, so that the TXRF rapid analysis technology can be used for daily analysis and detection of atmospheric particulate matter carried by the filter membrane. Another purpose is that the atmospheric particulate matter sample is very precious. When the TXRF technology is used directly to analyze the atmospheric particulate matter carried by the filter membrane, the sample is only affected by weak X-ray irradiation, and its composition and morphology are not damaged. It can be preserved and other components and morphology can be analyzed.

[0022] Example 1

[0023] like Figure 1As shown, the present invention provides a pressure ring device for keeping the atmospheric filter membrane flat so as to directly measure the atmospheric particles carried by the filter membrane using a total reflection X-ray fluorescence spectrometer. It includes a pressure ring component 1, a sample tray 2 and a sample rack 3; the surface of the sample tray 3 is higher than the sample rack 2; the pressure ring component 1 is attracted by the magnet block on the sample rack 3 so that the filter membrane 5 to be measured is stretched tight on the surface of the sample tray 2. The pressure ring component 1 is a steel pressure ring, and the sample rack is provided with a magnet block 4 that can attract the steel pressure ring so that the steel pressure ring presses the filter membrane to be measured onto the sample rack. There are multiple magnet blocks with moderate magnetic force, which are evenly arranged on the sample rack 3. The sample rack 3 is provided with a concave hole; the magnet block 4 is fixed in the concave hole, preferably with epoxy resin.

[0024] The sample disk 2 is preferably a quartz disk, and the height difference between the upper surface of the quartz disk and the sample holder 3 is preferably 0.5-3 mm so as to tighten the filter membrane and prevent the filter membrane from being broken due to over-tightening.

[0025] In this embodiment, a plurality of magnet blocks are installed on the sample rack, and the air filter membrane carrying atmospheric particles is placed directly above the quartz sample plate of the sample rack, and a steel pressure ring is placed with tweezers, whose inner diameter is slightly larger than the outer diameter of the quartz sample plate. The air filter membrane will be fixed by the steel pressure ring, tightened on the sample plate, and kept flat.

[0026] The analysis experiment of atmospheric particulate matter carried on the filter membrane has verified that this design fully meets the requirements, that is, the atmospheric particulate matter carried on the filter membrane can be directly analyzed by TXRF.

[0027] As mentioned above, in the prior art, the use of TXRF technology to analyze atmospheric particulate matter must undergo a transfer operation, including ultrasonic oscillation to peel off particles from the filter membrane, microwave digestion, quantitative transfer to a quartz sample tray with a dropper, infrared drying, etc., and each sample takes about two hours. By using the technical solution of this patent application, the TXRF technology can be used to directly and quickly analyze the elemental composition of atmospheric particulate matter carried on the filter membrane, saving the time for particle digestion and transfer, and shortening the analysis time to 10 minutes, greatly improving efficiency, reducing work intensity and analysis costs, and allowing precious atmospheric particulate matter samples carried on the filter membrane to be preserved.

[0028] In some cases of severe atmospheric pollution, it is necessary to complete the analysis and measurement in a short time and give the composition of atmospheric particulate matter. Obviously, it is too late to perform TXRF analysis after the atmospheric particulate matter is digested and transferred to the membrane, or to perform ICP-MS analysis after dissolution. After using the magnetic pressure ring device, the flatness of the filter membrane meets the requirements for direct TXRF analysis, and rapid analysis of the elemental composition of atmospheric particulate matter is achieved. The purchase cost of ICP-MS equipment is more than 3 million yuan, and the operating cost is also high, while this equipment is about 800,000 yuan, and the operating cost is very low. Therefore, the cost of TXRF atmospheric particulate elemental analysis technology supported by the filter membrane pressure ring technology related to this patent is much lower than that of ICP-MS.

[0029] Tables 1 and 2 respectively indicate the detection limits of several major elements commonly found in atmospheric particulate matter using tungsten target and molybdenum target TXRF analysis techniques, which have been verified by a third party. The detection limit is calculated based on the blank background value. Quartz and organic membranes have different impurity contents, so the two are not directly comparable. However, according to the data in the table, both can meet the requirements of the detection limit. The measurement results of atmospheric particulate matter after digestion and transfer to quartz sample sheets (the method before this patented technology) were compared with the results of direct measurement of atmospheric particulate matter carried on the filter membrane using this technology, proving that this patented technology realizes the direct TXRF measurement of atmospheric particulate matter carried on the filter membrane, without a significant adverse effect on the detection limit (MDL), and can meet the detection limit requirements required for the source analysis of atmospheric particulate matter in the prior art.

[0030] Table 1

[0031]

[0032] Table 2

[0033]

[0034] Example 2

[0035] The basic concept of this embodiment is consistent with that of Embodiment 1, except for the location of the magnet. In this embodiment, the pressure ring component is made of a material with uniform magnetism, which can attract the sample holder so that the pressure ring component presses the filter membrane to be measured onto the sample holder; at least a part of the sample holder is made of an iron material that can cooperate with the ferromagnetic material of the pressure ring component.

[0036] Experimental example

[0037] Using the TXRF analysis technology supported by the technical solution of this patent application and the currently most accurate ICP-MS analysis technology, the atmospheric particulate matter collected by the same batch of samples collected in Beijing during the same period of time using PTFE sampling membranes was detected and analyzed for pollution sources. The analysis results are shown in Figure 2The left column in the figure is the result of TXRF detection using the pressure ring device of the present invention, and the right column is the result of detection using ICP-MS analysis technology by the monitoring center. Figure 2 The data in the figure show that the results of pollution source analysis using the TXRF analysis method supported by this patented technology are almost consistent with the results obtained using the precise ICP-MS analysis method, and the detection time is shortened from 2 hours required for ICP-MS pre-analysis to 10 minutes, greatly improving efficiency and speeding up analysis.

[0038] At present, there are 1,500 county-level environmental monitoring stations in China, and many universities and research institutions need to analyze the atmospheric particulate matter carried by the filter membrane. Therefore, the device of this patent invention can make the TXRF analysis technology widely used in the atmospheric particulate matter monitoring and analysis work. In addition, the present invention can also be used for the analysis of the particulate matter carried by the filter membrane directly by Raman spectroscopy analysis technology.

[0039] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A pressure ring device for keeping an atmospheric filter membrane flat so as to be used for direct measurement of atmospheric particles carried by the filter membrane by a total reflection X-ray fluorescence spectrometer, characterized in that: It comprises a pressing ring component, a sample tray and a sample rack; the surface of the sample tray is higher than the sample rack; the pressing ring component cooperates with the sample rack to tighten the filter membrane to be measured on the surface of the sample tray, the pressing ring component is a steel pressing ring, and the sample rack is provided with a magnet block which can attract the steel pressing ring so that the steel pressing ring presses the filter membrane to be measured on the sample rack. There are multiple magnet blocks which are evenly arranged on the sample rack, and the material of the pressing ring component has uniform magnetism; at least part of the sample rack is made of ferromagnetic material which can cooperate with the magnetic pressing ring component, the sample tray is a quartz tray, and the elevation difference between the upper surface of the quartz tray and the sample rack is 0.5-3mm, so as to realize the total reflection of X-rays and enable the TXRF rapid analysis technology to be used for the analysis and detection of atmospheric particulate matter carried by daily filter membranes.

2. The pressure ring device for keeping the atmospheric filter membrane flat so as to be used for direct measurement of atmospheric particles carried by the filter membrane by a total reflection X-ray fluorescence spectrometer as claimed in claim 1, characterized in that: The sample rack is provided with a concave hole; the magnet block is fixed in the concave hole.

3. The pressure ring device for keeping the atmospheric filter membrane flat so as to be used for direct measurement of atmospheric particles carried by the filter membrane by a total reflection X-ray fluorescence spectrometer as claimed in claim 2, characterized in that: The magnet blocks are fixed at corresponding positions by bonding with epoxy resin.

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