阅读说明：本技术 一种基于超声雾化进样的微等离子体激发源及激发方法 (Micro-plasma excitation source and excitation method based on ultrasonic atomization sampling ) 是由 朱振利 董俊航 杨春 丁涵清 于 2021-08-19 设计创作，主要内容包括：本发明提供一种基于超声雾化进样的微等离子体激发源,涉及发射光谱元素分析激发光源领域,微等离子体激发源包括：交流电源、两根金属电极和超声雾化片；所述交流电源分别与所述金属电极的一端电性连接；所述金属电极的放电端位于同一平面内；所述超声雾化片水平设置在所述金属电极的放电端的上方,用于将待测溶液转化成气溶胶并向下喷射至所述金属电极的放电端上以及所述金属电极之间；所述交流电源、所述金属电极和所述气溶胶配合,用于在所述金属电极的下方形成V形微等离子体；本发明还提出采用上述基于超声雾化进样的微等离子体激发源的激发方法,能够有效地提高金属元素的检测精度。(The invention provides a microplasma excitation source based on ultrasonic atomization sampling, which relates to the field of excitation light sources for emission spectrum element analysis, and comprises: the ultrasonic atomization device comprises an alternating current power supply, two metal electrodes and an ultrasonic atomization sheet; the alternating current power supply is electrically connected with one end of the metal electrode respectively; the discharge ends of the metal electrodes are positioned in the same plane; the ultrasonic atomization sheet is horizontally arranged above the discharge end of the metal electrode and used for converting a solution to be tested into aerosol and downwards spraying the aerosol onto the discharge end of the metal electrode and between the metal electrodes; the alternating current power supply, the metal electrode and the aerosol are matched and used for forming V-shaped micro plasma below the metal electrode; the invention also provides an excitation method of the micro-plasma excitation source based on ultrasonic atomization sampling, which can effectively improve the detection precision of the metal elements.)

1. A microplasma excitation source based on ultrasonic atomization sampling is characterized by comprising: the ultrasonic atomization device comprises an alternating current power supply, two metal electrodes and an ultrasonic atomization sheet;

the alternating current power supply is electrically connected with one end of the metal electrode respectively; the discharge ends of the metal electrodes are positioned in the same plane;

the ultrasonic atomization sheet is horizontally arranged above the discharge end of the metal electrode and used for converting a solution to be tested into aerosol and downwards spraying the aerosol onto the discharge end of the metal electrode and between the metal electrodes;

the alternating current power supply, the metal electrode and the aerosol are matched and used for forming V-shaped micro plasma below the metal electrode.

2. The microplasma excitation source based on ultrasonic atomization sampling of claim 1, wherein the distance between the discharge ends is 2-8 mm; the vertical distance between the ultrasonic atomization sheet and the discharge end of the metal electrode is 10-50 mm.

3. The microplasma excitation source based on ultrasonic atomization sampling of claim 1, wherein the atomization speed of the ultrasonic atomization sheet is 3-100 μ L/s.

4. The micro-plasma excitation source based on ultrasonic atomization sampling of claim 1, wherein the metal electrode is made of tungsten or titanium.

5. The micro-plasma excitation source based on ultrasonic atomized sampling according to claim 1, further comprising an integrated circuit board and a mobile power supply; the mobile power supply is electrically connected with the ultrasonic atomization sheet through the integrated circuit board; the integrated circuit board is used for adjusting the output power and the frequency of the ultrasonic atomization piece.

6. The micro-plasma excitation source based on ultrasonic atomization sampling is characterized in that the output voltage of the mobile power supply is 4-24V, and the output current of the mobile power supply is 5-100 mA.

7. The micro-plasma excitation source based on the ultrasonic atomization sampling is characterized in that the output voltage of the alternating current power supply is 3-20 kV, and the output current is 5-100 mA.

8. An excitation method using the microplasma excitation source based on ultrasonic atomization sampling according to any one of claims 1-7, characterized by comprising the following steps:

dropwise adding the solution to be detected onto the ultrasonic atomization sheet;

converting the solution to be tested into aerosol through the ultrasonic atomization sheet and downwards spraying the aerosol onto the discharge end of the metal electrode and between the metal electrodes;

and forming V-shaped micro plasma below the metal electrode through the alternating current power supply and the metal electrode.

Technical Field

The invention relates to the field of excitation light sources for analyzing emission spectrum elements, in particular to a microplasma excitation source and an excitation method based on ultrasonic atomization sampling.

Background

The traditional excitation source comprises an inductively coupled plasma excitation source, but the problems of high power consumption, high gas consumption, difficult maintenance and the like are limited in a laboratory, so that the in-situ field analysis and detection cannot be met. In order to meet the requirement of in-situ elemental analysis, a plurality of microplasma excitation sources are developed successively, and an excitation light source such as an invention patent authorization publication No. CN 101330794B, CN 102445445B, CN 102866224B, CN 103760138B is a DBD; the invention patent publication No. CN 103776818B, CN 104254188B, application publication No. CN 107991272B and other excitation light sources are APGD; the excitation light source such as the invention patent publication No. CN 102288594B and the application publication No. CN 103969244A, CN 105675585A, CN 106596515A is SCGD. Although the micro-plasma excitation source reported at present has a small size and can greatly reduce power consumption and gas consumption, the dependence on compressed gas or peristaltic pump for plasma maintenance and sample introduction is still avoided, which is not beneficial to the overall miniaturization of the analytical instrument, so that the development of a simpler micro-plasma excitation source is necessary.

Ultrasonic atomization is an alternative scheme of traditional pneumatic atomization sampling, has higher atomization sampling efficiency, is a very effective sampling method, and is also applied to the technical field of on-site chemical component detection and analysis, for example, the invention patent publication No. CN 101788487A adopts ultrasonic atomization to assist in electric spark breakdown spectroscopy detection, but the ultrasonic atomization device has large volume and depends on a sample cell and gas guide, which is not beneficial to the requirement of integral miniaturization of an analysis instrument. Although the element field analysis can be carried out, the excitation source belongs to instantaneous breakdown discharge, so that a long-term continuous and stable signal is difficult to provide, only qualitative or semi-quantitative analysis can be achieved, and the requirement of high-precision quantitative analysis cannot be met.

Disclosure of Invention

The invention aims to provide a microplasma excitation source and an excitation method based on ultrasonic atomization sampling, which can improve the detection precision of metal elements.

The invention provides a microplasma excitation source based on ultrasonic atomization sampling, which comprises: the ultrasonic atomization device comprises an alternating current power supply, two metal electrodes and an ultrasonic atomization sheet;

the alternating current power supply is electrically connected with one end of the metal electrode respectively; the discharge ends of the metal electrodes are positioned in the same plane;

the ultrasonic atomization sheet is horizontally arranged above the discharge end of the metal electrode and used for converting a solution to be tested into aerosol and downwards spraying the aerosol onto the discharge end of the metal electrode and between the metal electrodes;

the alternating current power supply, the metal electrode and the aerosol are matched and used for forming V-shaped micro plasma below the metal electrode.

Further, the distance between the discharge ends is 2-8 mm; the vertical distance between the ultrasonic atomization sheet and the discharge end of the metal electrode is 10-50 mm.

Furthermore, the atomization speed of the ultrasonic atomization sheet is 3-100 mu L/s.

Furthermore, the metal electrode is made of tungsten or titanium.

Further, the micro-plasma excitation source based on ultrasonic atomization sampling further comprises an integrated circuit board and a mobile power supply; the mobile power supply is electrically connected with the ultrasonic atomization sheet through the integrated circuit board and used for supplying power to the ultrasonic atomization sheet; the integrated circuit board is used for adjusting the output power and the frequency of the ultrasonic atomization piece.

Furthermore, the output voltage of the mobile power supply is 4-24V, and the output current is 5-100 mA.

Further, the output voltage of the alternating current power supply is 3-20 kV, and the output current is 5-100 mA.

The invention also provides an excitation method of the micro-plasma excitation source based on ultrasonic atomization sampling, which comprises the following steps:

dropwise adding the solution to be detected onto the ultrasonic atomization sheet;

converting the solution to be tested into aerosol through the ultrasonic atomization sheet and downwards spraying the aerosol onto the discharge end of the metal electrode and between the metal electrodes;

and forming V-shaped micro plasma below the metal electrode through the alternating current power supply and the metal electrode.

The technical scheme provided by the embodiment of the invention has the following beneficial effects: the micro-plasma excitation source based on ultrasonic atomization sampling in the embodiment of the invention comprises an alternating current power supply, two metal electrodes and an ultrasonic atomization sheet; the alternating current power supply is electrically connected with one end of the metal electrode respectively; the discharge ends of the metal electrodes are positioned in the same plane; the ultrasonic atomization sheet is horizontally arranged above the discharge end of the metal electrode and used for converting a solution to be tested into aerosol and downwards spraying the aerosol onto the discharge end of the metal electrode and between the metal electrodes; the alternating current power supply, the metal electrode and the aerosol are matched and used for forming V-shaped micro plasma below the metal electrode; when the ultrasonic atomization device is used, the solution to be detected is sprayed onto the metal electrodes in the form of aerosol through the ultrasonic atomization sheet, and the temperature of the metal electrodes can be effectively reduced, meanwhile, under the action of the aerosol positioned between the discharge ends of the metal electrodes, the resistance of the original breakdown position (namely the position of the linear connection section of the discharge end of the metal electrode) of the metal electrodes is increased, so that the discharge path of the metal electrodes is deviated downwards, and stable and continuous V-shaped micro-plasmas are formed below the discharge end of the metal electrodes, so that the detection accuracy of metal elements is improved; in addition, the V-shaped micro-plasma is positioned below the discharge end of the metal electrode, so that the micro spectrometer can pointedly acquire signals of the V-shaped micro-plasma below the metal electrode, thereby effectively avoiding background interference of continuous light emitted by the metal electrode, and meanwhile, the V-shaped plasma excitation source can provide a longer discharge path at the same electrode distance, thereby increasing the contact area of the micro-plasma and aerosol, improving the excitation efficiency of metal elements, obtaining high-sensitivity signals, reducing the detection limit of the metal elements and further improving the detection precision of the metal elements; the invention is combined with emission spectrum, can realize the rapid in-situ detection of alkali metal elements such as lithium, sodium, potassium and the like, wherein the detection limit of the lithium element is less than 0.6ng/mL, the detection limit of the sodium element is less than 0.3ng/mL, and the detection limit of the potassium element is less than 1.5 ng/mL.

Drawings

FIG. 1 is a schematic structural diagram of a microplasma excitation source based on ultrasonic atomization sampling in an embodiment of the present invention;

FIG. 2 is a reference diagram of the usage state of the microplasma excitation source based on ultrasonic atomization sampling in FIG. 1;

FIG. 3 is a graph of the background blank and atomic emission spectra of lithium, sodium and potassium obtained in example 1 of the present invention;

FIG. 4 is a graph showing atomic emission spectra of lithium, sodium and potassium obtained in example 2 of the present invention;

FIG. 5 is a graph of integrated signal intensity of peak area of lithium obtained in time-resolved mode in example 2 of the present invention;

FIG. 6 is a standard curve of Li, Na and K elements in the present invention;

wherein, 1, ultrasonic atomization sheet; 2. an integrated circuit board; 3. a mobile power supply; 4. a metal electrode; 5. an alternating current power supply; 6. a rubber head dropper; 7. a solution to be tested; 8. aerosol; 9. v-shaped microplasma; 10. a spectral detector.

Detailed Description

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and together with the description, serve to explain the principles of the invention and not to limit the scope of the invention.

Referring to fig. 1, an embodiment of the present invention provides a microplasma excitation source based on ultrasonic atomization sampling, including: an alternating current power supply 5, two metal electrodes 4 and an ultrasonic atomization sheet 1;

the alternating current power supply 5 is respectively electrically connected with one end of the metal electrode 4; the discharge ends of the metal electrodes 4 are positioned in the same plane; one end of the metal electrode 4 is connected with an alternating current power supply 5, and the other end of the metal electrode is used as a discharge end;

the ultrasonic atomization sheet 1 is horizontally arranged above the discharge end of the metal electrode 4 and used for converting a solution 7 to be tested into aerosol 8 and downwards spraying the aerosol 8 onto the discharge end of the metal electrode 4 and between the metal electrodes 4;

the alternating current power supply 5, the metal electrode 4 and the aerosol 8 are matched for forming V-shaped micro-plasma 9 below the metal electrode 4.

Exemplarily, in the present embodiment, the metal electrodes 4 are distributed horizontally and are coaxially disposed; the center of the ultrasonic atomization sheet 1 is positioned on the perpendicular bisector of the connecting line of the discharge ends of the metal electrodes 4, so that the ultrasonic atomization sheet 1 can better convert the solution 7 to be tested into aerosol 8, and then spray the aerosol 8 onto the discharge ends of the metal electrodes 4 and the area between the discharge ends of the metal electrodes 4.

Specifically, the distance between the discharge ends of the metal electrodes 4 is 2-8 mm; the vertical distance between the ultrasonic atomization sheet 1 and the discharge end of the metal electrode 4 is 10-50 mm.

Specifically, the atomization speed of the ultrasonic atomization sheet 1 is 3-30 mu L/s.

Specifically, the metal electrode 4 is made of tungsten or titanium.

Further, referring to fig. 1, the microplasma excitation source based on ultrasonic atomization sampling further includes an integrated circuit board 2 and a mobile power supply 3; the mobile power supply 3 is electrically connected with the ultrasonic atomization sheet 1 through the integrated circuit board 2 and used for supplying power to the ultrasonic atomization sheet 1; the integrated circuit board 2 is used for adjusting the output power and frequency of the ultrasonic atomization sheet 1.

Specifically, the output voltage of the mobile power supply 3 is 4-24V, and the output current is 5-100 mA.

It should be noted that the portable power source is a better and portable mode; as a variation of this embodiment, the ultrasonic atomization sheet 1 may also be directly connected to a commercial power supply or a USB jack on a laptop or desktop computer through an adapter to supply power to the ultrasonic atomization sheet.

Specifically, the output voltage of the alternating current power supply 5 is 3-20 kV, and the output current is 5-100 mA.

Exemplarily, in the present embodiment, the mobile power supply 3 is a power bank.

Referring to fig. 2, the excitation method of the microplasma excitation source based on ultrasonic atomization sampling in this embodiment includes the following steps:

dripping a solution 7 to be detected onto the ultrasonic atomization sheet 1 through a rubber head dropper 6;

the solution 7 to be measured is converted into aerosol 8 through the ultrasonic atomization sheet 1 and is sprayed downwards onto the discharge end of the metal electrode 4 and between the metal electrodes 4, and V-shaped micro plasma 9 is formed below the metal electrodes 4.

In the present embodiment, in order to detect the concentration of the metal element in the solution to be detected 7, after the above steps, the V-shaped micro plasma 9 below the metal electrode 4 is subjected to signal acquisition by the spectrum detector 10, so as to realize simple, fast and accurate detection of the metal element in the solution to be detected 7.

The method for detecting lithium, sodium and potassium elements in different samples is exemplified by selecting different sample solutions. In all the following embodiments, the metal electrodes 4 are titanium rods with the diameter of 2mm, and the solution to be measured 7 (including a blank solution, a standard solution and a sample solution) is added to the central area of the ultrasonic atomization sheet 1 through a rubber head dropper 6, so that the introduction of the solution to be measured 7 is realized; the distance between the two metal electrodes 4 is 3mm, the vertical distance between the ultrasonic atomization sheet 1 and the discharge end of the metal electrode 4 is 20mm, the ultrasonic atomization speed is 5 mu L/s, the output voltage of the alternating current power supply 5 for maintaining the discharge work of the V-shaped micro plasma 9 is 7000V, and the output current is 20 mA; the output voltage of the mobile power supply 3 is 5V; the vibration frequency of the ultrasonic atomization sheet 1 is 110 kHz; the spectrum detector 10 is a micro spectrometer with a detection wavelength range of 186-986 nm.

Example 1

In this embodiment, the method for analyzing lithium, sodium, and potassium elements in a natural surface water sample is established based on the combination of a micro-plasma excitation source for ultrasonic atomization sampling and a micro spectrometer, which includes the following steps:

the method comprises the steps of dropwise adding a natural surface water sample solution into the central area of the ultrasonic atomization sheet 1, converting the solution into aerosol 8 through cavitation to be sprayed out, enabling the aerosol 8 to continuously enter a plasma excitation source, changing the path of the plasma, forming V-shaped stable plasma, and transferring heat generated by an electrode to play a cooling role. After evaporation, dissociation, atomization and excitation processes, lithium, sodium and potassium elements are excited to obtain a characteristic emission spectrum, and a blank or an emission spectrogram of lithium, sodium and potassium is obtained by detecting through a micro spectrometer 9, so that the detection of the elements such as lithium, sodium and potassium in the water body is realized, and the details are shown in an attached figure 3.

Example 2

In this embodiment, the method for analyzing lithium, sodium, and potassium elements in a serum sample based on the combination of the micro-plasma excitation source for ultrasonic atomization sampling and the micro spectrometer specifically includes:

(1) turning on the mobile power supply 3 and the alternating current power supply 5; (2) dropwise adding the blank solution into the central area of the ultrasonic atomization sheet 1, and automatically breaking down air to discharge under the action of the aerosol 8 to form stable V-shaped plasma between the metal electrodes 4; (3) diluting a serum sample by 10-100 times with ultrapure water, and then dropwise adding the diluted serum sample into the central area of the ultrasonic atomization sheet 1 to convert the diluted serum sample into aerosol 8 which enters plasma; (4) the excitation source of the micro-plasma based on ultrasonic atomization sample injection and the aerosol 8 act to generate characteristic emission light of lithium, sodium and potassium, and a micro spectrometer detects the emission spectrogram of the lithium, sodium and potassium to realize the detection of lithium, sodium and potassium elements in serum, and the details are shown in an attached figure 4; referring to fig. 5, the residual signal of lithium can be washed to a blank level in 8s, the total analysis time of a single sample is less than 40s, and high-throughput detection of lithium element in serum can be realized.

It should be noted that, the technical detection results of the detection method for lithium, sodium, and potassium elements described in this embodiment are only for illustrating the detection effect of the combination of the micro-plasma excitation source based on ultrasonic atomization sample injection and the spectrum detector 10 in this embodiment, and are not limited by the present invention; the micro-plasma excitation source based on ultrasonic atomization sampling can be used together with the spectral detector 10 to detect metal elements such As Zn, Cd, Mg, Ca, Ba, Rb, Sr, Cs, Cu, Fe, Ni, Co, As, Au, Pb, Mn, Hg and the like.

The method for preparing the standard curve of the lithium, sodium and potassium elements comprises the following steps:

(1) the emission signal intensities of the standard solutions of lithium, sodium and potassium with different concentrations were measured by the method of example 1, and the results are detailed in tables 1, 2 and 3.

TABLE 1 table of standard solution test results of lithium element

TABLE 2 table of sodium standard solution test results

TABLE 3 detection result of potassium standard solution

(2) Respectively drawing standard curves of lithium, sodium and potassium elements according to the data in the tables 1, 2 and 3, and referring to the attached figure 5 in detail; wherein the content of the first and second substances,

1) the standard curve equation of lithium element is:

y＝20.26x+0.66，R2＝0.99993；

2) the standard curve equation of sodium element is:

y＝24.62x+16.57，R2＝0.99999；

3) the standard curve equation of potassium element is:

y＝9.79x+8.41，R2＝0.99998。

in the invention, the detection limits of lithium, sodium and potassium elements are measured as follows:

the detection limits of lithium, sodium and potassium are respectively calculated by adopting a formula (1),

LOD 3 sigma/K equation (1)

Wherein LOD is detection limit in ng.mL^-1(ii) a σ is the standard deviation of eleven blank sample (pure water) emission signal intensity tests, in a.u.; k is the signal value of the target element in unit concentration, the unit is mL. ng^-1；

(1) Eleven blank samples (pure water) of lithium (Li) emitted signal intensities as shown in table 4;

TABLE 4 table of the results of the detection of the emitted signal intensity of eleven blank samples of lithium

As can be seen from Table 4:

σ(Li)＝4.1a.u.，

K(Li)＝20.26mL·ng^-1，

(2) eleven blank samples (pure water) of sodium (Na) emitted signal intensities as shown in table 5;

TABLE 5 emission signal intensity detection results of eleven blank samples of sodium

As can be seen from Table 5:

σ(Na)＝2.5a.u.，

K(Na)＝24.62mL·ng^-1，

(3) the signal intensities emitted by eleven blank samples (pure water) of potassium (K) are shown in table 6;

TABLE 6 emission signal intensity detection results of eleven blank samples of sodium

As can be seen from Table 6:

σ(K)＝4.8a.u.，

K(K)＝9.79mL·ng^-1，

as can be seen from the above, the detection limit of lithium element was 0.6ng/mL, that of sodium element was 0.3ng/mL, and that of potassium element was 1.5 ng/mL.

The micro-plasma excitation source based on ultrasonic atomization sampling in the embodiment has the following advantages:

1) in the embodiment, the microplasma excitation source based on ultrasonic atomization sampling belongs to a stable and continuous excitation source, and the maintenance does not need any heat dissipation refrigeration device, a sample cell, a peristaltic pump or compressed (inert) gas;

2) the micro-plasma excitation source based on ultrasonic atomization sampling in the embodiment has the characteristics of low power consumption, easiness in manufacturing, small volume, low cost, high sensitivity, simultaneous detection of multiple elements and the like, and can be used for rapidly detecting lithium, sodium and potassium alkali metal elements;

3) due to the cavitation effect of the ultrasonic atomization sheet 1, the solution 7 to be detected forms airflow wrapped with aerosol 8, so that the resistance of the original breakdown position between the metal electrodes 4 is increased, the discharge path of the metal electrodes 4 is deviated downwards, and V-shaped micro-plasma 9 is formed; in addition, the micro spectrometer can pointedly collect signals of the V-shaped micro plasma 9 below the metal electrode 4, thereby effectively avoiding background interference of continuous light emitted by the material of the metal electrode 4;

4) the V-shaped microplasma 9 excitation source can provide a longer discharge path under the same distance between the metal electrodes 4, and the contact area between the microplasma and the aerosol 8 is increased, so that the excitation efficiency of metal elements is improved, and a high-sensitivity signal is obtained;

5) the ultrasonic atomization sheet 1 is adopted to realize the rapid and effective introduction of a sample, and simultaneously, the heat dissipation effect is provided for the metal electrode 4, and an additional waste discharge device is not needed;

6) the continuous stable microplasma can adopt a micro spectrometer to collect signals, and the signals in the continuous stable microplasma can be continuously collected for a plurality of times within a certain time while the spectral detector 10 is ensured to be portable, small and highly integrated, so that better accuracy and precision are provided;

7) the low-temperature micro-plasma has better ionization interference resistance, and provides a high-efficiency, cheap, portable, reliable and high-sensitivity field analysis and detection means for analyzing alkali metal elements (lithium, sodium, potassium and the like) and other elements in a high-salt matrix sample;

8) in this embodiment, the spectrum detector 10 is used together to realize the rapid in-situ detection of lithium, sodium and potassium elements, wherein the detection limit of lithium element is 0.6ng/mL, the detection limit of sodium element is 0.3ng/mL and the detection limit of potassium element is 1.5 ng/mL.

The above is not relevant and is applicable to the prior art.

In this document, the terms front, back, upper and lower are used to define the components in the drawings and the positions of the components relative to each other, and are used for clarity and convenience of the technical solution. It is to be understood that the use of the directional terms should not be taken to limit the scope of the claims.

The features of the embodiments and embodiments described herein above may be combined with each other without conflict.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.