Aerosol sampling and focusing device for laser ablation plasma mass spectrometry

Abstract

The invention discloses an aerosol sampling and focusing device for a laser ablation plasma mass spectrometer, comprising an aerosol focuser, a plasma mass spectrometer, an ablation cell and a laser. A sample to be ablated is placed in the ablation cell, and a carrier aerosol is transported to a carrier aerosol hose connected to the other end of the ablation cell. The carrier aerosol hose is connected to an air inlet port of an aerosol focuser for leaking carrier gas. A semipermeable membrane tube is connected to an air outlet port at the rear end thereof. A sealing box surrounds the semipermeable membrane tube to form an aerosol focuser cavity. An electric gate is installed on the outside of the air release port to control the pressure in the aerosol focuser cavity. The carrier aerosol in a central tube enters the plasma mass spectrometer after being atomized and ionized, and the elements to be detected in the aerosol are detected. The invention increases the ion concentration of the elements to be detected entering the plasma mass spectrometer by discharging the carrier gas, thereby improving the sensitivity of the instrument, and effectively improving the detection limit of the elements to be detected without changing other instruments and devices.

Description

Technical Field

[0001] The invention relates to the technical field of chemical analysis, and in particular to an aerosol sampling and focusing device for a laser ablation plasma mass spectrometer. Background Art

[0002] The plasma mass spectrometer has become an important member of analytical instruments in the field of analytical chemistry and geochemistry due to its super element detection ability. Its application in many fields such as environment, geology, medicine, agriculture, etc. is becoming more and more extensive. Due to the needs of scientific research and the super analytical ability of ICPMS, the technology of micro-area in-situ analysis of samples is becoming more and more mature. The instruments suitable for micro-area in-situ analysis of samples currently include electron probe, secondary particle probe, and laser ablation plasma mass spectrometry. Laser ablation-ICP-MS is an accurate and precise in-situ analysis technology for solid trace elements. These solids include natural and artificial silicates, carbonates, oxides and sulfides.

[0003] Laser ablation technology is a technique in which the laser generated by the laser is focused to the surface of the sample to be tested through the laser optical path. The aerosol particles generated by the ablation of the sample surface are transported to the plasma through the carrier gas for atomization and ionization, and then introduced into the mass spectrometer for element or isotope analysis. The amount of the element to be tested that finally enters the MS mass analyzer after ionization by the plasma torch is less than 1% of the aerosol amount. In order to improve the sensitivity and precision of LA-ICPMS instrument analysis. Previous research work has focused on changing the wavelength of the laser (1064nm, 532nm, 266nm, 248nm, 222nm, 213nm, 193nm, 157nm), changing the shape of the ablation cell, adding a smoother in the aerosol pipeline, and changing the shape of the sample cone (S cone and Jet cone) and the intercepting cone (X cone and H cone). The instrument performance has been greatly improved. Despite this, the determination of elements in some ultra-low content samples (such as ultra-low content uranium and lead determination in quartz) is very difficult. Therefore, there is an urgent need to design an aerosol sampling and focusing device for a laser ablation plasma mass spectrometer to solve the problem that low-content elements in the sample cannot be detected. Summary of the invention

[0004] In view of the problems existing in the prior art, the object of the present invention is to provide an aerosol sampling and focusing device for a laser ablation plasma mass spectrometer.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a laser ablation plasma mass spectrometer aerosol sampling and focusing device, comprising an aerosol focuser, a plasma mass spectrometer, an ablation cell and a laser, wherein a sample to be ablated is placed in the ablation cell, and the sample to be ablated is irradiated by the laser to form an aerosol, a gas cylinder is connected to one side of the ablation cell, and the carrier gas in the gas cylinder and the aerosol form a carrier gas aerosol in the ablation cell, and the carrier gas aerosol is transported to a carrier gas aerosol hose connected to the other end of the ablation cell, and the carrier gas aerosol hose is connected to the air inlet port of the aerosol focuser, and the rear end of the air inlet port is connected to a semipermeable membrane tube, and the semipermeable membrane tube is sampled. It has a frustum-shaped structure and is hollow inside, and is used for the infiltration of carrier gas. The rear end of the semipermeable membrane tube is connected to an outlet pipe port, and the air inlet pipe port and the air outlet pipe port are relatively installed on the wall of the sealed box. The sealed box surrounds the semipermeable membrane tube to form an aerosol focuser cavity. Two air leakage pipe ports are provided on the wall of the sealed box. An electric gate is installed on the outside of the air leakage pipe port to control the pressure in the aerosol focuser cavity. The rear end of the air outlet pipe port is connected to the central tube of the plasma matrix tube through a transition hose. The carrier aerosol in the central tube enters the plasma mass spectrometer through the interface after being atomized and ionized by ICP, and is used to detect the elements to be measured in the aerosol.

[0006] Specifically, the rear end of the laser refracts the laser through a lens installed, and a focusing objective lens is installed below the lens to focus the laser and irradiate it on the sample to be etched in the etch pool.

[0007] Specifically, a camera with a microscope is installed above the lens for observing and recording laser ablation.

[0008] Specifically, the tube wall of the semipermeable membrane tube adopts a multi-microporous tubular semipermeable membrane frustum-shaped tube, and the semipermeable membrane tube is made of polytetrafluoroethylene or silicon material.

[0009] Specifically, the inner diameters of one end of the semipermeable membrane tube and the air inlet port are consistent with each other, which are 4 mm, and the inner diameters of the other end of the semipermeable membrane tube and the air outlet port are consistent with each other, which are 2 mm or 1 mm.

[0010] Specifically, the carrier gas is helium or argon or a mixed gas of the two, and the helium or argon passes through the semipermeable membrane tube under pressure.

[0011] Specifically, the electric gate of the air vent is connected to the controller via a communication line to control the opening of the air vent. A purge air pipe is connected to the air vent at one end as needed to discharge the carrier gas in the aerosol focuser cavity.

[0012] Specifically, the interface is a sampling cone and a skimmer cone.

[0013] Specifically, the sealing box is made of transparent polytetrafluoroethylene.

[0014] The present invention has the following beneficial effects:

[0015] The laser ablation plasma mass spectrometer aerosol sampling and focusing device designed by the present invention increases the concentration of aerosol entering the plasma torch by discharging the carrier gas, thereby increasing the concentration of ions of the element to be measured in the plasma torch, increasing the number of ions of the element to be measured entering the LA-ICPMS mass analyzer through the interface (sampling cone and interceptor cone), thereby improving the sensitivity of the instrument and effectively improving the detection limit of the element to be measured without changing other instruments and devices; the designed electric gate automatically controls the opening size of the vent pipe port, controls the pressure in the aerosol focuser cavity, and controls the discharge amount of the carrier gas; the device is made of easily available materials, has a simple structure, is easy to manufacture, is easy to operate, has a low cost, and is easy to promote and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the workflow structure of the laser ablation plasma mass spectrometer.

[0017] Figure 2 It is a schematic diagram of the structure of the aerosol sampling and focusing device of the laser ablation plasma mass spectrometer.

[0018] In the figure: 1-aerosol focuser; 2-plasma mass spectrometer; 3-erosion cell; 4-plasma matrix tube; 5-laser; 6-camera with microscope; 7-lens; 8-sample to be eroded; 9-gas cylinder; 10-focusing objective lens; 11-carrier aerosol hose; 101-aerosol focuser cavity; 102-sealed box; 103-semipermeable membrane tube; 104-inlet pipe port; 105-outlet pipe port; 106-vent pipe port; 107-carrier aerosol flow direction; 401-sampling cone; 402-intercepting cone; 403-cold air inlet; 404-center tube. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely further describe the technical solutions in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0020] like Figure 1-2 As shown, the aerosol sampling and focusing device of the laser ablation plasma mass spectrometer includes an aerosol focuser 1, a plasma mass spectrometer 2, an ablation cell 3, a plasma torque tube 4, a laser 5 and a camera 6 with a microscope. The rear end of the laser 5 refracts the laser through a lens 7 installed. A focusing objective lens 10 is installed below the lens 7 to focus the laser and irradiate it on the sample 8 to be ablated in the ablation cell 3. A camera 6 with a microscope is installed above the lens 7 to observe and record the laser ablation.

[0021] A sample 8 to be etched is placed in the erosion pool 3. The sample 8 to be etched generates an aerosol after being irradiated by the laser 5. A gas cylinder 9 is connected to one side of the erosion pool 3. The carrier gas and the aerosol contained in the gas cylinder 9 form a carrier gas aerosol in the erosion pool. The carrier gas is helium or argon or a mixed gas of the two. The helium or argon passes through the semipermeable membrane tube under pressure, and the carrier gas transports the carrier gas aerosol to the carrier gas aerosol hose 11 connected to the other end of the erosion pool 3.

[0022] The carrier gas aerosol enters the air inlet port 104 of the aerosol focuser 1 connected at the rear end through the carrier gas aerosol hose 11. The rear end of the air inlet port 104 is connected to a semipermeable membrane tube 103. The semipermeable membrane tube 103 adopts a frustum-shaped structure and is hollow inside for infiltrating the carrier gas. The tube wall of the semipermeable membrane tube 103 adopts a multi-microporous tubular semipermeable membrane frustum-shaped tube, and the semipermeable membrane tube 103 is made of polytetrafluoroethylene or silicon material. An outlet pipe port 105 is connected to the rear end of the semipermeable membrane tube 103, and the air inlet pipe port 104 and the air outlet pipe port 105 are relatively installed on the box wall of the sealed box 102. The sealed box 102 surrounds the semipermeable membrane tube 103 to form an aerosol focuser cavity 101. Two air leakage pipe ports 106 are provided on the box wall of the sealed box 102. Electric gates are installed on the outside of the air leakage pipe ports 106 to control the pressure in the aerosol focuser cavity 101. The electric gates of the air leakage pipe ports 106 are connected to the controller through a communication line to control the opening of the air leakage pipe ports 106. A purge air pipe is connected to the air leakage pipe port 106 at one end as needed to discharge the carrier gas in the aerosol focuser cavity 101, so as to ensure that the flow rate of the concentrated carrier gas in the semipermeable membrane tube 103 entering the central tube 404 of the plasma matrix tube 4 is basically consistent with the flow rate of the carrier gas in the instrument without the present device. The pressure in the aerosol focuser cavity 101 is controlled to control the discharge amount of the carrier gas, and a purge gas can also be connected to increase the discharge speed of the carrier gas.

[0023] The rear end of the gas outlet 105 enters the central tube 404 of the plasma matrix tube 4 through a transition hose. The carrier gas aerosol in the central tube 404 is atomized and ionized by the ICP of the plasma matrix tube 4 and then enters the plasma mass spectrometer 2 through the interface (sampling cone 401 and intercepting cone 402) for detecting the elements to be measured in the aerosol.

[0024] The inner diameter of one end of the semipermeable membrane tube 103 and the air inlet port 104 is consistent with 4mm, and the inner diameter of the other end of the semipermeable membrane tube 103 and the air outlet port 105 is consistent with 2mm or 1mm, and is consistent with the diameter of the central tube 404 of the plasma torque tube 4. The sealing box 102 is made of transparent polytetrafluoroethylene.

[0025] The working steps of the device added to the laser ablation plasma mass spectrometer are as follows:

[0026] 1) The laser emitted by the laser 5 is refracted by the lens 7, and then focused by the focusing lens 10 so that the laser beam is irradiated onto the sample to be ablated 8 in the ablation cell 3, and an aerosol is formed in the ablation cell 3;

[0027] 2) The carrier gas in the gas cylinder 9 transports the aerosol to the carrier gas aerosol hose 11, and then enters the semipermeable membrane tube 103 through the air inlet port 104. The controller controls the electric gate to open the air release port 106. The carrier gas in the semipermeable membrane tube 103 generates a pressure difference between the inside and outside of the semipermeable membrane tube 103 due to the reduction of the outlet. The carrier gas is discharged from the semipermeable membrane tube 103 through the micropores and then discharged through the air release port.

[0028] 3) The concentration of the carrier gas aerosol increases after the carrier gas is removed, so that the ion concentration of the element to be measured in the plasma increases. The element to be measured enters the plasma mass spectrometer 2 through the central tube 404, the sampling cone 401 and the intercepting cone 402 to detect the element to be measured.

[0029] This device improves the sensitivity of the instrument and effectively increases the detection limit of the element to be measured without changing other instrument devices.

[0030] The present invention is not limited to the above-mentioned implementation modes, and anyone should be aware of the structural changes made under the enlightenment of the present invention, and all those having the same or similar technical solutions as the present invention fall within the protection scope of the present invention.

[0031] The techniques, shapes, and structural parts not described in detail in the present invention are all well-known techniques.

Claims

1. An aerosol sampling and focusing device for a laser ablation plasma mass spectrometer, characterized in that: The invention comprises an aerosol focuser, a plasma mass spectrometer, an ablation cell and a laser, wherein a sample to be ablated is placed in the ablation cell, and the sample to be ablated is irradiated by the laser to form an aerosol, a gas cylinder is connected to one side of the ablation cell, a carrier gas in the gas cylinder and an aerosol form a carrier gas aerosol in the ablation cell, and the carrier gas aerosol is transported to a carrier gas aerosol hose connected to the other end of the ablation cell, the carrier gas aerosol hose is connected to an air inlet port of the aerosol focuser, a semipermeable membrane tube is connected to the rear end of the air inlet port, the semipermeable membrane tube adopts a cone-shaped structure and is hollow inside, and is used to infiltrate the carrier gas, and the semipermeable membrane tube adopts a cone-shaped structure and is hollow inside, and is used to infiltrate the carrier gas. The rear end of the membrane tube is connected with an air outlet, and the air inlet and the air outlet are relatively installed on the box wall of the sealed box. The sealed box surrounds the semipermeable membrane tube to form an aerosol focuser cavity. Two air leakage pipe openings are arranged on the box wall of the sealed box. An electric gate is installed on the outside of the air leakage pipe opening to control the pressure in the aerosol focuser cavity. The rear end of the air outlet pipe opening is connected to the central tube of the plasma matrix tube through a transition hose. The carrier gas aerosol in the central tube enters the plasma mass spectrometer through the interface after being atomized and ionized by ICP, so as to detect the elements to be measured in the aerosol. The laser is refracted by a lens installed at the rear end of the laser, and a focusing objective lens is installed below the lens to focus the laser and irradiate it on the sample to be etched in the etch pool; The tube wall of the semipermeable membrane tube adopts a multi-microporous tubular semipermeable membrane frustum-shaped tube, and the semipermeable membrane tube adopts polytetrafluoroethylene or silicon material.

2. The aerosol sampling and focusing device for laser ablation plasma mass spectrometry according to claim 1, characterized in that: A camera with a microscope is installed above the lens for observing and recording laser ablation.

3. The aerosol sampling and focusing device for laser ablation plasma mass spectrometry according to claim 1, characterized in that: The inner diameters of one end of the semipermeable membrane tube and the air inlet port are consistent with each other, which are 4 mm, and the inner diameters of the other end of the semipermeable membrane tube and the air outlet port are consistent with each other, which are 2 mm or 1 mm.

4. The aerosol sampling and focusing device for laser ablation plasma mass spectrometry according to claim 1, characterized in that: The carrier gas is helium or argon or a mixed gas of the two, and the helium or argon passes through the semipermeable membrane tube under pressure.

5. The aerosol sampling and focusing device for laser ablation plasma mass spectrometry according to claim 1, characterized in that: The electric gate of the air vent is connected to the controller via a communication line to control the opening of the air vent. A purge air pipe is connected to the air vent at one end as needed to discharge the carrier gas in the aerosol focuser cavity.

6. The aerosol sampling and focusing device for laser ablation plasma mass spectrometry according to claim 1, characterized in that: The interfaces are a sampling cone and a skimmer cone.

7. The aerosol sampling and focusing device for laser ablation plasma mass spectrometry according to claim 1, characterized in that: The sealing box is made of transparent polytetrafluoroethylene.

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