Liquid cathode glow discharge spectrometer with optical filter automatic switching function

Abstract

The invention belongs to the technical field of atomic spectrum metal element analysis, and particularly relates to a liquid cathode glow discharge spectrometer with an optical filter automatic switching function, which comprises a solid anode, a liquid cathode, an optical filter assembly, a circular convex lens and an optical fiber spectrometer, a glow discharge area is arranged between the solid anode and the liquid cathode, the optical fiber spectrometer is arranged outside the glow discharge area, and the circular convex lens is arranged between the glow discharge area and the optical fiber spectrometer; the optical filter assembly is arranged between the glow discharge area and the circular convex lens and comprises a rotating disc and a plurality of through holes distributed in the circumference of the rotating disc, and at least one through hole is provided with an optical filter. According to the liquid cathode glow discharge spectrometer, different optical filters can be switched and selected according to different measured wavelengths of to-be-measured elements and interference conditions of adjacent spectral lines (bands), so that the working efficiency is improved, the consumption of a test solution of a test sample is reduced, the measurement precision is improved, and the labor time is saved.

Description

Technical Field

[0001] The present invention belongs to the technical field of atomic spectroscopy for metal element analysis, and particularly relates to a liquid cathode glow discharge spectrometer with an automatic filter switching function. Background Art

[0002] The liquid cathode glow discharge emission spectrometer can be used for the determination of various metal elements in liquid samples, including elements such as lead, mercury, silver, thallium, cadmium, chromium, manganese, iron, copper, zinc, potassium, lithium, sodium, calcium, magnesium, gallium, indium, etc. This instrument applies a voltage of several hundred to thousands of volts between the metal anode and the sample injection solution cathode to ionize and discharge the gas between the electrodes, forming a microplasma. During the discharge process, the metal ions of the element to be measured volatilize or sputter into the microplasma and are thermally excited to generate an emission spectrum, and the quantitative detection of the element to be measured is realized through the characteristic radiation of different metal elements.

[0003] During the process of the metal ions of the element to be measured volatilizing or sputtering into the microplasma, complex coexisting matrix components also enter the plasma together, forming a matrix radiation band. In the quantitative analysis process of some target elements, the analysis spectral line is easily affected by serious spectral interference caused by the continuous adjacent band radiation of molecular groups, which affects the accuracy of the measurement results. Installing a filter can significantly improve this problem. However, when the target analysis element changes, the filter usually needs to be replaced, which restricts the realization of multi-element analysis with a single injection of the liquid cathode glow discharge emission spectrometer, not only significantly affecting the analysis efficiency, but also resulting in a relatively large consumption of the test sample solution. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a liquid cathode glow discharge spectrometer with an automatic filter switching function. According to the different wavelengths of the element to be measured and the interference situation of adjacent spectral lines (bands), different filters can be switched and selected, greatly improving the working efficiency of multi-element analysis with adjacent spectral line (band) interference, reducing the consumption of the test sample solution, and at the same time improving the measurement accuracy by effectively eliminating the interference of the molecular group emission spectrum. The need for multi-element determination with different adjacent spectral line (band) interferences can be realized without manually disassembling and installing the filter, saving a large amount of time for manually replacing the filter.

[0005] Specifically, the present invention provides the following technical solutions:

[0006] A liquid cathode glow discharge spectrometer with an automatic filter switching function, comprising a solid anode, a liquid cathode, a filter assembly, a circular convex lens, and an optical fiber spectrometer;

[0007] There is a glow discharge region between the solid anode and the liquid cathode. The fiber optic spectrometer is arranged outside the glow discharge region, and the circular convex lens is arranged between the glow discharge region and the fiber optic spectrometer;

[0008] The filter assembly is arranged between the glow discharge region and the circular convex lens, and includes a rotating disk and a plurality of through holes arranged circumferentially on the rotating disk, and at least one of the through holes is provided with a filter.

[0009] Preferably, the filter assembly is arranged parallel to the circular convex lens. As the rotating disk of the filter assembly rotates, the central axis of the circular convex lens can pass through each through hole on the rotating disk in turn. After successful breakdown, the light passes through the through hole penetrated by the central axis of the circular convex lens, is incident on the circular convex lens, and after being focused by the circular convex lens, enters the fiber optic spectrometer to collect the required data; if the through hole is provided with a filter, the filter can filter the light passing through the through hole.

[0010] Preferably, it further includes a sector-shaped light blocking sheet; the sector-shaped light blocking sheet is arranged between the glow discharge region and the filter assembly. The sector-shaped light blocking sheet is used to block the light from passing through other through holes, ensuring that the light only passes through the through hole penetrated by the central axis of the circular convex lens, thereby eliminating the stray light interference of different channels.

[0011] Preferably, among the through holes arranged circumferentially on the rotating disk, one through hole is not provided with a filter, and the remaining through holes are provided with different types of filters.

[0012] Preferably, the size of the through hole on the rotating disk is 2 mm to 50 mm (if the through hole is a circular hole, the diameter size is 2 mm to 50 mm; if the through hole is a square hole, the side length size is 2 mm to 50 mm);

[0013] The diameter of the circular convex lens is 10 mm to 25 mm, preferably 16 mm to 20 mm.

[0014] Preferably, the filter assembly is located 2 to 5 cm outside the glow discharge region; it is found that if the distance is less than the above range, it will be corroded by acid mist; if the distance is greater than the above range, there will be light energy loss;

[0015] The distance between the filter assembly and the circular convex lens is 0 to 5 cm, preferably 0.2 - 2 cm; it is found that if the distance between the filter assembly and the circular convex lens is too large, there will be energy loss.

[0016] Preferably, the fiber optic probe of the fiber optic spectrometer is located at the focus of the outgoing light of the circular convex lens.

[0017] Preferably, a rotating shaft is fixedly connected to the middle of the rotating disk, and the rotating shaft is driven by a motor to rotate.

[0018] Preferably, the liquid cathode includes a glass tube with an opening at one end facing the solid anode. A graphite auxiliary electrode is sleeved outside the glass tube, and the solid anode and the graphite auxiliary electrode are connected to a high-voltage power supply.

[0019] Beneficial effects achieved by the present invention:

[0020] (1) A liquid cathode glow discharge spectrometer with an automatic filter switching function provided by the present invention realizes the switching of specific band-pass (cut-off) filters or no filters by driving the motor to rotate the rotating disk, so that different filter positions can be automatically selected according to the measurement wavelengths of elements to be measured and the interference conditions of adjacent spectral lines (bands).

[0021] (2) A liquid cathode glow discharge spectrometer with an automatic filter switching function provided by the present invention saves a large amount of time for manual filter replacement, greatly improves the working efficiency of multi-element analysis with interference from adjacent spectral lines (bands), reduces the consumption of test sample solutions, and improves the measurement accuracy by effectively eliminating the interference of molecular group emission spectra.

[0022] (3) A liquid cathode glow discharge spectrometer with an automatic filter switching function provided by the present invention eliminates the stray light interference of different channels by arranging a sector-shaped light blocking plate between the glow discharge region and the filter assembly.

[0023] (4) A liquid cathode glow discharge spectrometer with an automatic filter switching function provided by the present invention ensures that the wavelength range of the light transmitted through the filter does not deviate from the allowable value by limiting the diameters of the through holes and circular convex lenses on the rotating disk and their setting positions. In addition, while ensuring the feasibility of component processing, it effectively avoids the corrosion of optical devices by the acid mist generated during the liquid cathode glow discharge process; it reduces the light energy loss to the greatest extent, ensures the best light intensity of the spectral lines to be measured, and further improves the detection sensitivity.

[0024] (5) A liquid cathode glow discharge spectrometer with an automatic filter switching function provided by the present invention is applied to the simultaneous determination of thallium and lithium contents in a single injection, effectively eliminates matrix interference, and the detection limits of thallium and lithium elements are lower than 1.0 μg / L, and the repeatability RSDs are all lower than 10%. Description of the Drawings

[0025] Figure 1Schematic diagram of the structure of the liquid cathode glow discharge spectrometer in Example 1; where 1 is a solid anode, 2 is a graphite auxiliary electrode, 3 is a high-voltage power supply, 4 is a glow discharge region, 5 is a filter assembly, 6 is a motor, 7 is a circular convex lens, 8 is an optical fiber probe, 9 is an optical fiber spectrometer, 10 is waste liquid, 11 is a liquid cathode, 12 is a sample injection test solution, and 13 is a sector light shield.

[0026] Figure 2 Schematic diagram of the structure of the filter assembly in Example 1; where 14 is the reference position (without a filter), 15 is the first filter 1#, 16 is the second filter, 17 is a rotating shaft, 18 is the third filter, 19 is the fourth filter, and 20 is the fifth filter. Detailed implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention. For those not specifying specific techniques or conditions in the embodiments, they shall be carried out according to the techniques or conditions described in the literature in the field or according to the product specifications.

[0028] Example 1

[0029] A liquid cathode glow discharge spectrometer with an automatic filter switching function, see Figure 1-2 , including a solid anode 1, a liquid cathode 11, a sector light shield 13, a filter assembly 5, a circular convex lens 7, and an optical fiber spectrometer 9;

[0030] Between the solid anode 1 and the liquid cathode 11 is a glow discharge region 4, and the optical fiber spectrometer 9 is arranged outside the glow discharge region 4; the diameter of the circular convex lens 7 is 18 mm, which is arranged between the glow discharge region 4 and the optical fiber spectrometer 9, and the optical fiber probe 8 of the optical fiber spectrometer 9 is located at the focus of the outgoing light of the circular convex lens 7;

[0031] The filter assembly 5 is arranged between the glow discharge region 4 and the circular convex lens 7, and is 3 cm outside the glow discharge region 4, and the distance from the circular convex lens 7 is 1 cm;

[0032] The filter assembly 5 includes a rotating disk and 6 circular through holes with a diameter of 10 mm evenly arranged circumferentially on the rotating disk. One through hole is the reference position 14 without a filter, and the other through holes are respectively provided with different types of first filter 15, second filter 16, third filter 18, fourth filter 19, and fifth filter 20; the middle of the rotating disk is fixedly connected with a rotating shaft 17, and the rotating shaft 17 is driven to rotate by a motor 6.

[0033] The filter set 5 is arranged in parallel with the circular convex lens 7. As the rotating disk of the filter assembly 5 rotates, the central axes of the circular convex lens 7 can pass through each through hole on the rotating disk in sequence.

[0034] The sector light shield 13 is arranged between the glow discharge region 4 and the filter assembly 5 to ensure that light only passes through the through holes penetrated by the central axis of the circular convex lens 7, thereby eliminating the interference of stray light in different channels.

[0035] The liquid cathode 11 includes a glass tube with one end facing the solid anode 1 being open. A graphite auxiliary electrode 2 is sleeved outside the glass tube. The solid anode 1 and the graphite auxiliary electrode 2 are connected to a high-voltage power supply 3.

[0036] When not in the glow discharge working state, the filter set turntable 5 is in the reference position 14 (i.e., the central axis of the circular convex lens 7 passes through the reference position 13). When a voltage of several hundred to thousands of volts is applied between the solid electrode 1 and the graphite auxiliary cathode 2 through the high-voltage power supply 3, the sampling test solution 12 enters the glass tube. The air between the liquid cathode and the solid electrode 1 is ionized to generate a micro-plasma, and the glow discharge is successfully initiated. Then, according to different elements to be measured, in the selected order, the rotating disk of the filter assembly 5 is driven by the motor 6 to rotate to the first selected filter position to collect the required data. After the data collection is completed, the rotating disk of the filter assembly 5 is driven by the motor 6 to rotate to the second selected filter position to collect the required data; and so on. After all the element spectral data are collected, the rotating disk of the filter assembly 5 is driven by the motor 6 to return to the reference position 14, and then the glow discharge ends, and the waste liquid 10 is discharged through the quartz capillary.

[0037] Specifically, the liquid cathode glow discharge spectrometer with an automatic filter switching function is applied to the simultaneous determination of thallium and lithium contents in a single injection. The determination wavelength of thallium element is 535 nm, and a filter needs to be selected to eliminate matrix spectral interference; the determination wavelength of lithium element is 671 nm, and there is no significant matrix spectral interference. The reference position (without a filter, adding a filter will significantly reduce the sensitivity) is adopted, a tungsten discharge anode is used, at a discharge voltage of 700 V, a discharge current of 60 mA, an injection flow rate of 4.0 mL / min, and an injection volume of 2.5 mL. For industrial wastewater in which thallium and lithium elements are not detected by an inductively coupled plasma mass spectrometer as a blank matrix, thallium and lithium single-element standard solutions are respectively added to prepare a standard series with thallium and lithium element concentrations of 5 μg / L, 10 μg / L, 20 μg / L, 50 μg / L, and 100 μg / L. The glow intensities of the standard series with different concentration gradients are measured from low to high concentrations, and the working curve for thallium element is fitted as y = 86x + 33 (y is the emission intensity, x is the thallium concentration); the working curve for lithium element is y = 124x + 33 (y is the emission intensity, x is the lithium concentration); the blank matrix solution is repeatedly measured 11 times, and three times the standard deviation of the glow intensities of thallium and lithium elements divided by the slope is used as the detection limit. The detection limits of thallium and lithium elements are 0.87 μg / L and 0.55 μg / L respectively; a sample of industrial wastewater blank matrix added with 10 μg / L thallium and lithium is subjected to 7 repeated tests, and the relative standard deviations are 4.8% and 6.2% respectively.

[0038] After the determination of lithium element by the liquid cathode glow discharge spectrometer without an automatic filter switching function, the filter needs to be removed and the light needs to be adjusted again by professional personnel before the determination. In comparison, the liquid cathode glow discharge spectrometer with an automatic filter switching function has significantly improved in terms of analysis efficiency, sample consumption, requirements for analysts, etc. while ensuring the analysis performance.

[0039] Although the present invention has been described in detail in the above text with general descriptions, specific embodiments and experiments, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.

Claims

1. A liquid cathode glow discharge spectrometer with automatic filter switching function, characterized in that: It includes a solid anode, a liquid cathode, a filter assembly, a circular convex lens and a fiber optic spectrometer; A glow discharge region is provided between the solid anode and the liquid cathode, the optical fiber spectrometer is arranged outside the glow discharge region, and the circular convex lens is arranged between the glow discharge region and the optical fiber spectrometer; The filter assembly is arranged between the glow discharge area and the circular convex lens, and comprises a rotating disk and a plurality of through holes arranged circumferentially on the rotating disk, and at least one of the through holes is provided with a filter.

2. The liquid cathode glow discharge spectrometer with automatic filter switching function according to claim 1, characterized in that: The filter assembly is arranged in parallel with the circular convex lens. As the rotating disk of the filter assembly rotates, each through hole on the rotating disk can be passed through by the central axis of the circular convex lens in sequence.

3. The liquid cathode glow discharge spectrometer method with automatic filter switching function according to claim 1 or 2, characterized in that: It also includes a fan-shaped light shielding plate; the fan-shaped light shielding plate is arranged between the glow discharge area and the filter assembly.

4. The liquid cathode glow discharge spectrometer method with automatic filter switching function according to claim 1 or 2, characterized in that: Among the through holes arranged circumferentially on the rotating disk, one through hole is not provided with a filter, and the other through holes are provided with filters of different types.

5. The liquid cathode glow discharge spectrometer with automatic filter switching function according to claim 1 or 2, characterized in that: The size of the through hole on the rotating disk is 2mm to 50mm; The diameter of the circular convex lens is 10 mm to 25 mm, preferably 16 mm to 20 mm.

6. A liquid cathode glow discharge spectrometer with automatic filter switching function according to claim 1 or 2, characterized in that: The filter assembly is located 2 to 5 cm outside the glow discharge area; The distance between the filter assembly and the circular convex lens is 0-5 cm, preferably 0.2-2 cm.

7. A liquid cathode glow discharge spectrometer with automatic filter switching function according to claim 1 or 2, characterized in that: The optical fiber probe of the optical fiber spectrometer is located at the focus of the outgoing light of the circular convex lens.

8. The liquid cathode glow discharge spectrometer with automatic filter switching function according to claim 1 or 2, characterized in that: A rotating shaft is fixedly connected to the middle of the rotating disk, and the rotating shaft is driven to rotate by a motor.

9. A liquid cathode glow discharge spectrometer with automatic filter switching function according to claim 1 or 2, characterized in that: The liquid cathode comprises a glass tube, one end of the glass tube is open toward the solid anode, a graphite auxiliary electrode is disposed outside the glass tube, and the solid anode and the graphite auxiliary electrode are connected to a high voltage power supply.

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