CN114778507B - Atomic fluorescence spectrometer based on integrated full-angle excitation source and measuring method - Google Patents

Abstract

The invention discloses an atomic fluorescence spectrometer based on an integrated full-angle excitation source and a measuring method, belonging to the technical field of analytical instruments, and comprising a gas control unit (21), a sample injection system (22), a microwave source (23), an excitation source (24), a fluorescence detection unit (25), a data processing unit (26) and a display recording unit (27), wherein the excitation source (24) consists of an excitation light source module and an annular atomizer module. The invention uses the light source and atomizer of the integrated full-angle excitation source to replace the hollow cathode lamp and oxyhydrogen flame in the prior art, and the excitation light source has the advantages of high radiation intensity, narrow spectral line, good spectral selectivity, capability of exciting the tested sample in 360-degree direction and full-angle.

Description

Atomic fluorescence spectrometer based on integrated full-angle excitation source and measurement method

Technical Field

The invention belongs to the technical field of analytical instruments, and particularly relates to an atomic fluorescence spectrometer based on an integrated full-angle excitation source and an atomic fluorescence spectrum measurement method.

Background Art

In atomic spectrometers, the excitation source (atomizer and/or excitation light source) is the key and core, which directly determines the structure of the instrument and the quality of the analytical performance. In existing atomic fluorescence spectrometers, the excitation light source and the atomizer are separated in physical space. Usually, the atomizer uses a hydrogen-oxygen flame in a quartz tube furnace, and the excitation light source uses a high-intensity hollow cathode lamp. The quartz tube atomizer is only suitable for elements that can generate gaseous hydrides at room temperature. The hydrogen generated by the hydride generation method is burned with oxygen in the air in an argon environment to achieve sample atomization. Therefore, the types of elements in the sample being tested are subject to certain restrictions.

The biggest problem with hollow cathode lamps as excitation light sources is that the luminous intensity of the lamp drifts severely, and the instrument needs to calibrate the standard curve regularly, which is inconvenient for users. Secondly, the commonly used hollow cathode lamps are sharp-line light sources. A hollow cathode lamp can only emit light radiation of one element corresponding to it, and can only be used to measure samples of the same type as the element. When different types of elements need to be measured, hollow cathode lamps of different elements need to be replaced. For example, if the zinc element in the sample is measured, a zinc element lamp needs to be configured for analysis. Due to the limitation of the types of hollow cathode lamps, the types of elements to be measured cannot be expanded at will. In addition, for the analysis of samples of multiple elements, lamps of multiple elements must be configured, which requires a larger instrument space.

In terms of instrument layout, in order to prevent the light radiation emitted by the excitation light source from affecting the measurement of weak atomic fluorescence signals, the direction in which the fluorescence detector receives the light signal must be at right angles or at an acute angle to the direction in which the excitation light irradiates the atomizer, and the excitation light beam irradiates the atomizer within a range of 180 degrees at best, as shown in Figure 1. As we all know, the intensity of the fluorescence signal is proportional to the intensity of the excitation light. Since the entire circumference of the quartz tube atomizer can only receive the excitation light within a range of 180 degrees at most, the measurement sensitivity of the instrument will inevitably be affected.

In summary, the existing atomic fluorescence spectrometers need further optimization.

Summary of the invention

In order to overcome the shortcomings of the above-mentioned existing atomic fluorescence spectrometers, the present invention provides an atomic fluorescence spectrometer based on an integrated full-angle excitation source, which is based on a microwave coaxial resonant cavity. An easily ionized working gas, a combustible gas, and a combustion-supporting gas are introduced into the microwave coaxial resonant cavity. In the same time and space range, a microwave coupled plasma and a high-temperature flame fusion excitation light source are obtained to complete the excitation of the standard sample injected in a pulsed manner and obtain pulsed excitation light. At the same time, a ring atomizer is arranged inside or outside the outer conductor of the microwave coaxial resonant cavity, and the atomization of the sample to be tested is completed by using a flame. The pulsed excitation light irradiates the atomized sample to be tested in a 360-degree direction to obtain a ring-shaped pulse fluorescence.

An atomic fluorescence spectrometer based on an integrated full-angle excitation source comprises a gas control unit 21, an injection system 22, a microwave source 23, an excitation source 24, a fluorescence detection unit 25, a data processing unit 26 and a display and recording unit 27; wherein the gas control unit 21 is used to accurately control the flow of each gas, inputs gas from a steel cylinder, and accurately controls the output of each gas to the outer gas inlet 5, the middle gas inlet 7, the inner gas inlet 9, the working gas inlet 13 and the shielding gas inlet 15 of the excitation source 24 and the carrier gas required by the injection system 22 through a pressure reducing valve, a pressure regulating valve, a flow regulating valve and a flow meter; the microwave source 23 outputs microwave power to the microwave input port 2 of the excitation source 24; the fluorescence detection unit 25 receives the fluorescence signal through a photoelectric detector, and then outputs it to the data processing unit 26 through an electronic circuit; the data processing unit 26 uses a microprocessor to collect, process and calculate the fluorescence signal, and outputs it to the display and recording unit 27 to complete display and storage;

The invention is characterized in that the excitation source 24 includes an excitation light source module and a ring atomizer module; the excitation light source module is a microwave coaxial resonant cavity, including an outer conductor 1, a microwave input port 2, a microwave antenna 3, an inner conductor 4, an outer gas inlet 5, a middle tube 6, a middle gas inlet 7, an inner tube 8, an inner gas inlet 9, a standard sample tube 10, and a standard sample inlet 11; the outer conductor 1, the inner conductor 4, the middle tube 6, the inner tube 8, and the standard sample tube 10 are nested in sequence from outside to inside and are coaxial, the inner conductor 4, the middle tube 6, the inner tube 8 and the sample tube 10 are flush at the outlet end face, and the inner conductor 4, the middle tube 6, the inner tube 8 and the standard sample tube 10 form a micro-cavity with a nested coaxial structure with the outer conductor 1. The invention discloses a microwave resonant cavity, wherein the characteristic impedance of the resonant cavity ranges from 50 to 80 ohms; the outer conductor 1 is a hollow cylinder with an inner diameter of 35 to 60 mm; the outlet end face of the nested coaxial structure formed by the inner conductor 4, the middle tube 6 and the inner tube 8 also has the function of a high-temperature flame combustion nozzle, and microwave coupled plasma and high-temperature flame are simultaneously generated at the outlet end face; the axis of the microwave input port 2 is 1/4 times the wavelength of the microwave used at the bottom of the microwave coaxial resonant cavity, and the microwave antenna 3 introduces microwave energy through the microwave input port 2 and is electrically connected to the inner conductor 4; the upper end face of the outer conductor 1 is (2n+1)/4 times the wavelength of the microwave used at the bottom of the microwave coaxial resonant cavity, wherein n is 1, 2 or 3;

The outer gas inlet 5 is located at a radial position at the lower part of the inner conductor 4 near the bottom end of the inner conductor 4, the middle gas inlet 7 is located at a radial position at the lower part of the middle tube 6 near the bottom end of the middle tube 6, and the inner gas inlet 9 is located at a radial position at the lower part of the inner tube 8 near the bottom end of the inner tube 8, all of which adopt a radial air intake method; the easily ionized gas entering from the outer gas inlet 5, the middle gas inlet 7 and the inner gas inlet 9 all flows out at its outlet end face in a laminar state, and is ionized by the microwave electric field energy to form a microwave coupled plasma; the easily ionized gas entering from the outer gas inlet 5, the middle gas inlet 7 and the inner gas inlet 9 The combustible gas and the combustion-supporting gas flow out of the combustion nozzle formed by the outlet end face thereof in a layered state, and burn to form a high-temperature flame; the microwave coupled plasma and the high-temperature flame merge at the same time and space to form a standard sample excitation light source; the standard sample inlet 11 is located at the bottom of the sample tube 10, and the high-concentration standard sample aerosol with the same element type as the sample to be tested enters the standard sample tube 10 through the standard sample inlet 11, and enters the excitation light source at the outlet side end face of the standard sample tube 10, and after excitation, the excitation light required for the fluorescence measurement of the sample to be tested is obtained;

The annular atomizer module includes a guide ring 12, a working gas inlet 13, a sample inlet 14, a shielding gas inlet 15, an inner layer guide tube 16, a middle layer guide tube 17 and an outer layer guide tube 18. The annular atomizer module is located above the microwave input port 2, on the inner or outer side of the outer conductor 1 of the microwave coaxial resonant cavity.

Specifically, when the annular atomizer is arranged on the inner side of the outer conductor 1 of the microwave coaxial resonant cavity above the microwave input port 2, the guide ring 12 is located inside the annular space formed by the outer conductor 1 and the inner conductor 4, and the guide ring 12 is made of non-metallic material; the outer conductor 1 has a working gas inlet 13, a sample inlet 14 and a shielding gas inlet 15 on the side; the guide ring 12 has a concave gas guide groove on the outside, and the guide ring 12 is designed with a working gas inlet 13 and a sample inlet 14 on the inside; the height of the gas guide groove is respectively consistent with the height of the working gas inlet 13 and the sample inlet 14 on the side of the outer conductor 1; the inner layer guide tube 16, the middle layer guide tube 17 and the outer layer guide tube 18 are installed in sequence on the inner side of the guide ring 12, and the inner layer guide tube 16, the middle layer guide tube 17 and the outer layer guide tube 18 are flush at the upper outlet end face; the inner layer guide tube 16, the middle layer guide tube 17 and the outer layer guide tube 18 are flush at the upper outlet end face; the inner layer guide tube 16, the middle layer guide tube 1 7 and the outer flow guide tube 18 are made of non-metallic materials that do not affect the electromagnetic field distribution inside the cavity, preferably quartz or ceramics; the inner flow guide tube 16 and the middle flow guide tube 17 constitute an annular atomizer for the sample to be tested, complete the atomization of the sample to be tested, and are excited by the pulsed excitation light source at all angles to generate annular fluorescence; the working gas is introduced into the annular gap formed by the inner flow guide tube 16 and the middle flow guide tube 17; the working gas is introduced in the tangential direction or radial direction of the annular gap formed by the inner flow guide tube 16 and the middle flow guide tube 17, flows to the end face in the form of eddy current or laminar flow, and participates in the flame combustion process; the aerosol of the sample to be tested is introduced into the annular gap formed by the middle flow guide tube 17 and the outer flow guide tube 18; the shielding gas is introduced into the annular gap formed by the outer flow guide tube 18 and the outer conductor 1; the shielding gas is introduced in the tangential or radial direction of the inner diameter of the outer conductor 1 to form an eddy current or laminar shielding layer.

Specifically, when the annular atomizer is arranged on the outside of the outer conductor 1 of the microwave coaxial resonant cavity above the microwave input port 2, the guide ring 12 is located outside the outer conductor 1 above the microwave input port 2, and the guide ring 12 is made of metal or non-metal material; the side of the guide ring 12 has a working gas inlet 13, a sample inlet 14 and a shielding gas inlet 15; the inner side of the guide ring 12 is successively installed with an inner layer guide tube 16, a middle layer guide tube 17 and an outer layer guide tube 18, and the inner layer guide tube 16, the middle layer guide tube 17 and the outer layer guide tube 18 are flush at the upper outlet end face; the inner layer guide tube 16, the middle layer guide tube 17 and the outer layer guide tube 18 can be non-metallic materials, preferably quartz or ceramics; or they can be metal materials, preferably brass; the outer conductor 1 and the inner flow guide tube 16 form an annular atomizer for the sample to be tested, complete the atomization of the sample to be tested, and are excited by the pulsed excitation light source at all angles to generate annular fluorescence; the working gas is introduced into the annular gap formed by the outer conductor 1 and the inner flow guide tube 16; the working gas is introduced in the tangential or radial direction of the annular gap formed by the outer conductor 1 and the inner flow guide tube 16, flows to the end face in the form of eddy current or laminar flow, and participates in the flame combustion process; the aerosol of the sample to be tested is introduced into the annular gap formed by the inner flow guide tube 16 and the middle flow guide tube 17; the shielding gas is introduced into the annular gap formed by the middle flow guide tube 17 and the outer flow guide tube 18; the shielding gas is introduced in the tangential direction or radial direction of the annular gap formed by the middle flow guide tube 17 and the outer flow guide tube 18, and forms an eddy current or laminar shielding layer.

Preferably, the standard sample excitation light source is located on the central axis of the microwave coaxial resonant cavity (as shown in FIG. 2 ); the upper end surface of the conductor 4 in the microwave coaxial resonant cavity is 5 to 15 mm lower than the upper end surface of the annular atomizer; the atomizer portion surrounds the standard sample excitation light source at the same height; the excitation light emitted by the standard sample excitation light source illuminates the atomizer surrounding it in a 360-degree (full angle) direction, and the sample to be tested is atomized in the atomizer and excited at all angles by the excitation light to generate annular fluorescence; multiple fluorescence detectors can be arranged outside the fluorescence ring to improve the measurement sensitivity.

Preferably, the specific structure of the sampling system 22 includes a peristaltic pump 220, a solenoid valve A221, a syringe pump 222, a solenoid valve B223, a pneumatic nebulizer A224, a cyclonic mist chamber A225, a cyclonic mist chamber B226, and a pneumatic nebulizer B227.

A method for fluorescence measurement using the atomic fluorescence spectrometer based on the integrated full-angle excitation source comprises the following steps:

1) The standard sample aerosol with the same element type as the sample to be tested is injected into the excitation light source in a pulsed manner to obtain pulsed excitation light;

2) The sample aerosol of unknown concentration is continuously injected into the annular atomizer and atomized continuously;

3) Exciting the atomized atoms of the sample to be tested by pulsed excitation light to obtain a temporally resolvable pulse fluorescence signal of the sample to be tested;

4) The pulse fluorescence signal is measured using a photodetector, and then combined with the instrument standard curve, the concentration of the sample to be tested is obtained through data processing.

Beneficial effects:

1. The atomic fluorescence spectrometer of the present invention uses an integrated full-angle excitation source to replace the hollow cathode lamp in the prior art, which has high stability in time and space and can obtain good measurement precision. At the same time, the excitation light source has high radiation intensity and narrow spectrum, which is conducive to subsequent fluorescence spectrum measurement. In addition, the excitation light source has good spectral selectivity and is convenient to replace the excitation spectrum. It only needs to replace the high-concentration standard solution of the same element type as the object to be measured that introduces the excitation light source. In theory, it can be applied to any element.

2. The atomic fluorescence spectrometer of the present invention uses an atomizer with an integrated full-angle excitation source to replace the hydrogen-oxygen flame in the prior art. By adjusting the gas flow rate, the ideal atomization efficiency and fluorescence efficiency can be obtained, the measurement sensitivity can be improved, and the detection limit can be reduced. At the same time, the types of measurement objects can be expanded so that they are no longer limited to elements that rely on hydride generation method for sampling.

3. The excitation source in the present invention has a compact structure, and the light source is located in the center. It can excite the sample to be tested in 360-degree directions to generate annular fluorescence, and can receive fluorescence signals at all angles, with high measurement sensitivity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a light path diagram of an existing atomic fluorescence spectrometer.

FIG. 2 is a light path diagram of the atomic fluorescence spectrometer of the present invention.

FIG3 is a schematic diagram of the structure of the integrated full-angle excitation source of Example 1.

FIG. 4 is a schematic diagram of the structure of an integrated full-angle excitation source of Example 2.

FIG5 is a flow chart of the overall structure of the atomic fluorescence spectrometer of the present invention.

FIG6 is a flow chart of the atomic fluorescence spectrometer sampling system of the present invention.

DETAILED DESCRIPTION

Example 1

FIG3 is a schematic diagram of the structure of an integrated full-angle excitation source used in the present invention, which is composed of an excitation light source module and a ring-shaped atomizer module. The excitation light source module is a microwave coaxial resonant cavity, comprising an outer conductor 1, a microwave input port 2, a microwave antenna 3, an inner conductor 4, an outer gas inlet 5, a middle tube 6, a middle gas inlet 7, an inner tube 8, an inner gas inlet 9, a standard sample tube 10, and a standard sample inlet 11; the outer conductor 1, the inner conductor 4, the middle tube 6, the inner tube 8, and the standard sample tube 10 are nested and coaxial in order from outside to inside, the inner conductor 4, the middle tube 6, the inner tube 8 and the sample tube 10 are flush at the outlet end face, the inner conductor 4, the middle tube 6, the inner tube 8 and the standard sample tube 10 and the outer conductor 1 form a microwave resonant cavity of a nested coaxial structure, and the characteristic impedance range of the resonant cavity is 50 to 80 ohms; the outer conductor 1 is a hollow cylinder with an inner diameter of 35 to 60 mm; the outlet end face of the nested coaxial structure formed by the inner conductor 4, the middle tube 6 and the inner tube 8 also has the function of a high-temperature flame combustion nozzle, and microwave coupled plasma and high-temperature flame can be obtained simultaneously.

The axis of the microwave input port 2 is 1/4 times the wavelength of the microwave used from the bottom surface of the microwave coaxial resonant cavity. The microwave antenna 3 introduces microwave energy through the microwave input port 2 and is electrically connected to the inner conductor 4 .

Preferably, the depth between the upper end surface of the outer conductor 1 and the bottom surface of the resonance cavity is (2n+1)/4 times the wavelength of the microwave used, where n is 1, 2 or 3. For example, when n=1, the distance between the upper end surface of the outer conductor and the bottom surface of the resonance cavity is about 90-100 mm. Preferably, the outer diameter of the inner conductor 5 is 10-18 mm, and the inner diameter is 9-16 mm.

The outer gas inlet 5 is located at a radial position at the lower part of the inner conductor 4 near the bottom end of the inner conductor 4, the middle gas inlet 7 is located at a radial position at the lower part of the middle tube 6 near the bottom end of the middle tube 6, and the inner gas inlet 9 is located at a radial position at the lower part of the inner tube 8 near the bottom end of the inner tube 8, all of which adopt a radial air intake method.

The easily ionized gas entering from the outer gas inlet 5, the middle gas inlet 7 and the inner gas inlet 9 flows out in a laminar state at its outlet end face, and is ionized by the microwave electric field energy to form a microwave coupled plasma; the combustible gas and the combustion-supporting gas entering from the outer gas inlet 5, the middle gas inlet 7 and the inner gas inlet 9 flow out in a layer state at the combustion nozzle formed at its outlet end face, and burn to form a high-temperature flame; the microwave coupled plasma and the high-temperature flame merge at the same time and space to form a standard sample excitation light source.

The standard sample inlet 11 is located at the bottom of the sample tube 10. The high-concentration standard sample aerosol with the same element type as the sample to be tested enters the standard sample tube 10 through the standard sample inlet 11 and enters the excitation light source at the end face of the outlet side of the standard sample tube 10. After excitation, the excitation light required for fluorescence measurement of the sample to be tested is obtained. When the standard sample enters the excitation light source in a pulsed manner, the pulsed excitation light required for fluorescence excitation of the sample to be tested can be obtained.

The annular atomizer module includes a guide ring 12 , a working gas inlet 13 , a sample inlet 14 , a shielding gas inlet 15 , an inner layer guide tube 16 , a middle layer guide tube 17 and an outer layer guide tube 18 .

In this embodiment, the annular atomizer is arranged inside the outer conductor 1 of the microwave coaxial resonant cavity above the microwave input port 2, and the guide ring 12 is located inside the annular space formed by the outer conductor 1 and the inner conductor 4, and the guide ring 12 is made of non-metallic material; the side of the outer conductor 1 is designed with a working gas inlet 13, a sample inlet 14 to be tested and a shielding gas inlet 15; the outer side of the guide ring 12 is designed with a concave gas guide groove, and the inner side of the guide ring 12 is designed with a working gas inlet 13 and a sample inlet 14 to be tested; the height of the gas guide groove is respectively consistent with the height of the working gas inlet 13 and the sample inlet 14 to be tested designed on the side of the outer conductor 1; the inner layer guide tube 16, the middle layer guide tube 17 and the outer layer guide tube 18 are installed in sequence on the inner side of the guide ring 12, and the inner layer guide tube 16, the middle layer guide tube 17 and the outer layer guide tube 18 are flush at the upper outlet end face; the inner layer guide tube 16, the middle layer guide tube 17 and the outer layer guide tube 18 are made of quartz or ceramic, which does not affect the electromagnetic field distribution inside the cavity. The inner layer flow guide tube 16 and the middle layer flow guide tube 17 form an annular atomizer for the sample to be tested, which completes the atomization of the sample to be tested and is excited at all angles by a pulsed excitation light source to generate annular fluorescence.

The working gas is introduced into the annular gap formed by the inner flow guide tube 16 and the middle flow guide tube 17; the working gas is introduced in the tangential direction of the annular gap formed by the inner flow guide tube 16 and the middle flow guide tube 17, flows to the end face in the form of vortex flow, and participates in the flame combustion process. The working gas can also be introduced in the radial direction of the annular gap formed by the inner flow guide tube 16 and the middle flow guide tube 17, flows to the end face in the form of laminar flow, and participates in the flame combustion process; the working gas can be mixed with combustion-supporting gas and combustible gas, and can also be mixed with inert gas at the same time; the combustion-supporting gas can be air or oxygen, preferably oxygen; the combustible gas can be hydrogen or methane, preferably hydrogen.

The aerosol of the sample to be tested is introduced into the annular gap formed by the middle flow tube 17 and the outer flow tube 18; the aerosol of the sample to be tested is introduced into the annular gap formed by the middle flow tube 17 and the outer flow tube 18, and the aerosol of the sample to be tested can be mixed with combustible gas or combustion-supporting gas. The mixed combustion-supporting gas or combustible gas participates in the flame combustion process at the same time. The aerosol of the sample to be tested can also be mixed with an inert gas, and preferably, argon is selected as the inert gas. The sample to be tested is atomized in the flame on the end face of the annular atomizer.

The shielding gas is passed into the annular gap formed by the outer flow guide tube 18 and the outer conductor 1; the shielding gas is introduced in the tangential direction of the outer conductor 1 to form an eddy current shielding layer. The shielding gas can also be introduced in the radial direction of the outer conductor 1 to form a laminar shielding layer. The shielding gas can inhibit the diffusion of the sample to be tested into the free space, and also prevent the atmospheric components from being involved in the flame atomization zone to produce background interference, effectively prevent the quenching of atomic fluorescence, and improve the atomic fluorescence intensity. The shielding gas can be oxygen or argon, preferably, argon.

Example 2

Fig. 4 is another structural schematic diagram of the integrated full-angle excitation source used in the present invention, which is composed of an excitation light source module and a ring atomizer module. The excitation light source module is a microwave coaxial resonant cavity, which is the same as the excitation source embodiment 1 and will not be described in detail here.

In this embodiment, the annular atomizer is arranged outside the outer conductor 1 of the microwave coaxial resonant cavity above the microwave input port 2, and the guide ring 12 is located outside the outer conductor 1 above the microwave input port 2; the side of the guide ring 12 is designed with a working gas inlet 13, a sample inlet 14 and a shielding gas inlet 15; the inner side of the guide ring 12 is installed with an inner layer guide tube 16, a middle layer guide tube 17 and an outer layer guide tube 18 in sequence, and the inner layer guide tube 16, the middle layer guide tube 17 and the outer layer guide tube 18 are flush at the upper outlet end face.

The inner layer flow guide tube 16 , the middle layer flow guide tube 17 and the outer layer flow guide tube 18 may be made of non-metallic materials, such as quartz or ceramic, or metallic materials, such as brass.

The working gas is introduced into the annular gap formed by the outer conductor 1 and the inner flow tube 16; the working gas is introduced in the tangential direction of the annular gap formed by the outer conductor 1 and the inner flow tube 16, flows to the end face in the form of eddy current, and participates in the flame combustion process. The working gas can also be introduced in the radial direction of the annular gap formed by the outer conductor 1 and the inner flow tube 16, flows to the end face in the form of laminar flow, and participates in the flame combustion process. The working gas can be mixed with combustion-supporting gas and combustible gas, and can also be mixed with inert gas at the same time; the combustion-supporting gas can be air or oxygen, preferably oxygen; the combustible gas can be hydrogen or methane, preferably hydrogen.

The aerosol of the sample to be tested is introduced into the annular gap formed by the inner flow tube 16 and the middle flow tube 17; the aerosol of the sample to be tested is introduced into the annular gap formed by the inner flow tube 16 and the middle flow tube 17, and the aerosol of the sample to be tested can be mixed with combustible gas or combustion-supporting gas. The mixed combustion-supporting gas or combustible gas participates in the flame combustion process at the same time. The aerosol of the sample to be tested can also be mixed with an inert gas, and preferably, argon is selected as the inert gas. The sample to be tested is atomized in the flame on the end face of the annular atomizer.

The shielding gas is introduced into the annular gap formed by the middle flow tube 17 and the outer flow tube 18; the shielding gas is introduced in the tangential direction of the annular gap formed by the middle flow tube 17 and the outer flow tube 18 to form an eddy current shielding layer. The shielding gas can also be introduced in the radial direction of the annular gap formed by the middle flow tube 17 and the outer flow tube 18 to form a laminar shielding layer. The shielding gas can inhibit the diffusion of the sample to be tested into the free space, and also prevent the atmospheric components from being involved in the flame atomization zone to produce background interference, effectively preventing the quenching of atomic fluorescence and improving the atomic fluorescence intensity. The shielding gas can be oxygen or argon, preferably, argon.

It is understandable that the excitation source used in the present invention has a strong excitation ability because the excitation light source is mainly plasma, and there is no drift problem of hollow cathode lamp, so there is no need to regularly calibrate the working curve of the instrument, and the application is more convenient. At the same time, compared with the existing instruments, since the excitation light source excites the sample to be tested in the annular flame atomizer at all angles, multiple fluorescence detectors can be set around the atomizer, and the distance is close, so that higher measurement sensitivity can be obtained.

Example 3

The structure of an atomic fluorescence spectrometer of the present invention is described with reference to FIG5 .

The present invention discloses an atomic fluorescence spectrometer based on an integrated full-angle excitation source, comprising a gas control unit 21, an injection system 22, a microwave source 23, an excitation source 24, a fluorescence detection unit 25, a data processing unit 26 and a display and recording unit 27. The gas control unit 21 is used to accurately control the flow of each gas. The gas is input from a steel cylinder, and the gas is accurately controlled by a pressure reducing valve, a pressure stabilizing valve, a flow stabilizing valve and a flow meter to be output to the outer gas inlet 5, the middle gas inlet 7, the inner gas inlet 9, the working gas inlet 13 and the shielding gas inlet 15 of the excitation source 24 and the carrier gas required by the pneumatic atomizers A and B in the injection system 22. The carrier gas output by the gas control unit 21 is used as a power to complete the atomization and pulse injection of high-concentration standard samples and transport them to the standard sample tube of the excitation light source. At the same time, the carrier gas output by the gas control unit 21 is used as a power to vaporize by a hydride generator or atomize by a pneumatic atomizer to achieve continuous injection of the sample to be tested and introduce it into the annular atomizer of the excitation source. The standard sample in the injection system 22 is input into the pneumatic nebulizer A224 via the peristaltic pump 220, the solenoid valve A221, the syringe pump 222 and the solenoid valve B223, and then the carrier gas input into the pneumatic nebulizer A224 by the gas control unit 21 is used to output the standard sample to the cyclonic spray chamber A225 for buffering, and then the sample is injected into the excitation source 24 in a pulsed manner. The sample to be tested in the injection system 22 is input into the pneumatic nebulizer B227 via the peristaltic pump 220, and then the carrier gas input into the pneumatic nebulizer B227 by the gas control unit 21 is used to output the sample to be tested to the cyclonic spray chamber B226 for buffering, and then the sample is injected into the excitation source 24 in a continuous manner; the pneumatic nebulizer B can be replaced by a hydride generator; the cyclonic spray chamber B can be replaced by a gas-liquid separator. The microwave source 23 outputs microwave power to the microwave input port 2 of the excitation source 24. Start the microwave output, the excitation light source generates a plasma torch flame, and the pulsed standard sample is excited in the torch flame, emitting pulsed light radiation of a specific wavelength. The sample to be tested enters the annular flame and is atomized. The pulsed light radiation generated by the excitation light source irradiates the atomizer at all angles, exciting the atoms of the sample to be tested to generate a pulsed fluorescence signal that can be resolved in time, and the signal enters the fluorescence detection unit 25. The fluorescence detection unit 25 receives the fluorescence signal through a photodetector, and then outputs it to the data processing unit 26 through an electronic circuit. The data processing unit 26 uses a microprocessor to collect, process, and calculate the fluorescence signal, and outputs it to the display recording unit 27 to complete the display and storage.

Example 4

The fluorescence spectrum measurement method using the atomic fluorescence spectrometer of the present invention is described in conjunction with Figure 6. Based on the atomic fluorescence spectrometer of the present invention, the specific fluorescence spectrum measurement steps are:

(1) Take a standard sample solution with an appropriate content and the same element type as the sample to be tested, use a syringe pump and a solenoid valve to form a pulse aerosol after being atomized by a coaxial pneumatic atomizer and enter the cyclonic spray chamber A, and then enter the standard sample inlet 11 after buffering. Enter the central channel of the excitation light source through the sample tube 10, be excited by the excitation light source, and obtain the pulsed excitation light required for fluorescence measurement of the sample to be tested;

(2) The sample to be tested of unknown concentration is atomized by a hydride generator or a pneumatic atomizer and enters the cyclonic spray chamber B. After being buffered, it continuously enters the sample inlet 14 to be tested and is continuously atomized in the flame of the annular atomizer.

(3) Exciting the atomized sample with a pulsed excitation light to obtain a time-resolvable annular pulse fluorescence signal;

(4) The pulse fluorescence signal is measured using a photodetector, and then combined with the instrument standard curve, the concentration of the sample to be tested is obtained through data processing to complete the measurement of the sample to be tested.

Claims (6)

1. An atomic fluorescence spectrometer based on an integrated full-angle excitation source comprises a gas control unit (21), a sample injection system (22), a microwave source (23), an excitation source (24), a fluorescence detection unit (25), a data processing unit (26) and a display recording unit (27); the gas control unit (21) is used for precisely controlling the flow rate of each path of gas, gas is input from the steel cylinder, and each path of gas is precisely controlled to be output to an outer layer gas inlet (5), a middle layer gas inlet (7), an inner layer gas inlet (9), a working gas inlet (13), a shielding gas inlet (15) and carrier gas required by the sample injection system (22) through a pressure reducing valve, a pressure stabilizing valve, a flow stabilizing valve and a flow meter; the microwave source (23) outputs microwave power to a microwave input port (2) of the excitation source (24); the fluorescence detection unit (25) receives fluorescence signals through the photoelectric detector and outputs the fluorescence signals to the data processing unit (26) through the electronic circuit; the data processing unit (26) collects, processes and calculates fluorescent signals by utilizing a microprocessor, and outputs the fluorescent signals to the display recording unit (27) to finish display and storage;

Wherein the excitation source 24 comprises an excitation light source module and a ring atomizer module; the excitation light source module is a microwave coaxial resonant cavity and comprises an outer conductor (1), a microwave input port (2), a microwave antenna (3), an inner conductor (4), an outer layer gas inlet (5), a middle pipe (6), a middle layer gas inlet (7), an inner pipe (8), an inner layer gas inlet (9), a standard sample pipe (10) and a standard sample inlet (11); the outer conductor (1), the inner conductor (4), the middle tube (6), the inner tube (8) and the standard sample tube (10) are sequentially nested and coaxial in an outer-to-inner sequence, the inner conductor (4), the middle tube (6), the inner tube (8) and the sample tube (10) are flush at the outlet end face, the inner conductor (4), the middle tube (6), the inner tube (8) and the standard sample tube (10) and the outer conductor (1) form a microwave resonant cavity with a nested coaxial structure, and the characteristic impedance range of the resonant cavity is 50-80 ohms; the outer conductor (1) is a cylinder with a hollow inside, and the inner diameter is 35-60 mm; the nested coaxial structure formed by the inner conductor (4), the middle pipe (6) and the inner pipe (8) has the function of a high-temperature flame combustion nozzle, and microwave coupling plasma and high-temperature flame are generated at the outlet end face; the axis of the microwave input port (2) is 1/4 times of the wavelength of the microwave used on the bottom surface of the microwave coaxial resonant cavity, and the microwave antenna (3) is used for introducing microwave energy through the microwave input port (2) and is electrically connected with the inner conductor (4); the distance between the upper end surface of the outer conductor (1) and the bottom surface of the microwave coaxial resonant cavity is (2n+1)/4 times of the wavelength of the microwave, wherein n is 1, 2 or 3;

The outer layer gas inlet (5) is positioned at the radial position of the lower part of the inner conductor (4) close to the bottom end of the inner conductor (4), the middle layer gas inlet (7) is positioned at the radial position of the lower part of the middle pipe (6) close to the bottom end of the middle pipe (6), the inner layer gas inlet (9) is positioned at the radial position of the lower part of the inner pipe (8) close to the bottom end of the inner pipe (8), and a radial air inlet mode is adopted; the ionized gas entering from the outer layer gas inlet (5), the middle layer gas inlet (7) and the inner layer gas inlet (9) flows out in a laminar flow state at the outlet end surfaces of the ionized gas, and microwave coupling plasma is formed by utilizing microwave electric field energy ionization; the combustible gas and the combustion-supporting gas entering from the outer layer gas inlet (5), the middle layer gas inlet (7) and the inner layer gas inlet (9) flow out in a layered manner from a combustion nozzle formed by the outlet end surfaces of the combustible gas and the combustion-supporting gas, and are combusted to form high-temperature flame; the microwave coupling plasma and the high-temperature flame are fused in the same time and space to form a standard sample excitation light source; the standard sample inlet (11) is positioned at the bottom of the sample tube (10), high-concentration standard sample aerosol with the same type as the element of the sample to be detected enters the standard sample tube (10) through the standard sample inlet (11), enters an excitation light source at the end face of the outlet side of the standard sample tube (10), and obtains excitation light required by fluorescence measurement of the sample to be detected after excitation;

The annular atomizer module comprises a guide ring (12), a working gas inlet (13), a sample inlet (14) to be detected, a shielding gas inlet (15), an inner guide pipe (16), a middle guide pipe (17) and an outer guide pipe (18), and is positioned above the microwave input port (2) and at the inner side or the outer side of an outer conductor (1) of the microwave coaxial resonant cavity.

2. The atomic fluorescence spectrometer based on the integrated full-angle excitation source according to claim 1, wherein when the annular atomizer is arranged on the inner side of the outer conductor (1) of the microwave coaxial resonant cavity above the microwave input port (2), the guide ring (12) is positioned in the annular space formed by the outer conductor (1) and the inner conductor (4), and the guide ring (12) is made of nonmetallic materials; the side surface of the outer conductor (1) is provided with a working gas inlet (13), a sample inlet (14) to be tested and a shielding gas inlet (15); the outside of the guide ring (12) is provided with a concave air guide groove, and the inside of the guide ring (12) is provided with a working air inlet (13) and a sample inlet (14) to be tested; the height of the air guide groove is respectively consistent with the heights of a working air inlet (13) and a sample inlet (14) to be tested on the side surface of the outer conductor (1); an inner layer flow guide pipe (16), a middle layer flow guide pipe (17) and an outer layer flow guide pipe (18) are sequentially arranged on the inner side of the flow guide ring (12), and the inner layer flow guide pipe (16), the middle layer flow guide pipe (17) and the outer layer flow guide pipe (18) are flush at the upper outlet end face; the inner layer honeycomb duct (16), the middle layer honeycomb duct (17) and the outer layer honeycomb duct (18) are made of nonmetallic materials which do not influence the electromagnetic field distribution in the cavity; the inner layer flow guide pipe (16) and the middle layer flow guide pipe (17) form an annular atomizer of the sample to be tested, atomization of the sample to be tested is completed, and the sample to be tested is excited by a pulse excitation light source at all angles to generate annular fluorescence; the working gas is introduced into an annular gap formed by the inner guide pipe (16) and the middle guide pipe (17); the working gas is introduced in the tangential direction or radial direction of an annular gap formed by the inner-layer flow guide pipe (16) and the middle flow guide pipe (17), flows to the end face in a vortex or laminar flow mode, and participates in the flame combustion process; introducing the aerosol of the sample to be tested into an annular gap formed by the middle guide pipe (17) and the outer guide pipe (18); shielding gas is introduced into an annular gap formed by the outer guide pipe (18) and the outer conductor (1); the shielding gas is introduced in a tangential or radial direction of the inner diameter of the outer conductor (1) to form an eddy or laminar shielding layer.

3. The atomic fluorescence spectrometer based on the integrated full-angle excitation source according to claim 1, wherein when the annular atomizer is arranged outside the outer conductor (1) of the microwave coaxial resonant cavity above the microwave input port (2), the guide ring (12) is positioned outside the upper outer conductor (1) of the microwave input port (2), and the guide ring (12) is made of metal or nonmetal materials; the side surface of the guide ring (12) is provided with a working gas inlet (13), a sample inlet (14) to be tested and a shielding gas inlet (15); an inner layer flow guide pipe (16), a middle layer flow guide pipe (17) and an outer layer flow guide pipe (18) are sequentially arranged on the inner side of the flow guide ring (12), and the inner layer flow guide pipe (16), the middle layer flow guide pipe (17) and the outer layer flow guide pipe (18) are flush at the upper outlet end face; the inner layer flow guide pipe (16), the middle layer flow guide pipe (17) and the outer layer flow guide pipe (18) are non-metal materials or metal materials; the outer conductor (1) and the inner layer flow guide pipe (16) form an annular atomizer of the sample to be tested, atomization of the sample to be tested is completed, and the sample to be tested is excited by a pulse excitation light source at all angles to generate annular fluorescence; the working gas is introduced into an annular gap formed by the outer conductor (1) and the inner guide pipe (16); the working gas is introduced in the tangential or radial direction of an annular gap formed by the outer conductor (1) and the inner guide pipe (16), flows to the end face in a vortex or laminar flow mode, and participates in the flame combustion process; introducing the aerosol of the sample to be tested into an annular gap formed by the inner guide pipe (16) and the middle guide pipe (17); shielding gas is introduced into an annular gap formed by the middle guide pipe (17) and the outer guide pipe (18); the shielding gas is introduced in the tangential direction or the radial direction of an annular gap formed by the middle guide pipe (17) and the outer guide pipe (18), and forms a vortex or laminar flow shielding layer.

4. An atomic fluorescence spectrometer based on an integrated full-angle excitation source according to any one of claims 1-3, wherein the standard sample excitation light source is located on the central axis of the microwave coaxial resonant cavity, and the upper end surface of the inner conductor (4) of the microwave coaxial resonant cavity is 5-15 mm lower than the upper end surface of the annular atomizer; the atomizer part surrounds the standard sample excitation light source at the same height; the excitation light emitted by the standard sample excitation light source irradiates an atomizer surrounding the standard sample excitation light source in the 360-degree direction, and the sample to be tested is excited by the excitation light at all angles after being atomized in the atomizer, so that annular fluorescence is generated.

5. An atomic fluorescence spectrometer based on an integrated full-angle excitation source according to any one of claims 1-3, wherein the specific structure of the sample injection system (22) comprises a peristaltic pump (220), a solenoid valve a (221), an injection pump (222), a solenoid valve B (223), a pneumatic atomizer a (224), a swirl mist chamber a (225), a swirl mist chamber B (226) and a pneumatic atomizer B (227).

6. A method of fluorescence measurement using the integrated omnidirectional excitation source-based atomic fluorescence spectrometer of claim 1, comprising the steps of:

1) The standard sample aerosol with the same element type as the sample to be detected is sampled to an excitation light source in a pulse mode to obtain pulse excitation light;

2) Sample aerosol with unknown concentration to be detected is continuously sampled to an annular atomizer and continuously atomized;

3) Exciting light pulses excite atoms of the sample to be detected after atomization to obtain pulse fluorescent signals of the sample to be detected which can be distinguished in time;

4) And measuring a pulse fluorescence signal by using a photoelectric detector, and then combining an instrument standard curve to obtain the concentration of the sample to be measured through data processing.