CN107917901A - A kind of method and apparatus of fluid sample elemental composition on-line checking - Google Patents

Abstract

The invention relates to a method and a device for on-line detection of elemental components of a liquid sample. The device injects the liquid sample into the sampling tank (2) through the peristaltic pump (1), so that the sample flows through the water storage tank (3) above the microporous ejection sheet (5). 7) under the action of high-frequency vibration, it is sprayed out from the outside of the spray hole (6) on the microporous spray sheet (5), forming dense liquid droplets moving at high speed. The fan (10) and the diversion exhaust pipe (8) keep the droplet sample in a stable cylindrical shape. After the laser pulse emitted by the laser (11) is focused by the focusing lens group (12), it breaks down dense liquid droplets to generate plasma, and the plasma radiation signal is collected by the lens group (13), optical fiber (14), and spectrometer (15). The obtained spectral signal realizes the element composition analysis of the sample. It can be used in high-precision detection applications in the fields of marine, chemical, food, pharmaceutical, scientific research and water pollution.

Description

Method and device for on-line detection of elemental components in liquid samples

technical field

The invention is suitable for continuous on-line detection of metal components in water bodies by laser-induced breakdown spectroscopy technology. This technology realizes real-time sampling through continuous online microhole jet-assisted sampling device, and uses laser-induced breakdown spectroscopy technology to achieve highly sensitive qualitative or quantitative detection of elemental components in water. This method is expected to be applied in the fields of water environment monitoring and natural water scientific investigation.

Background technique

Laser-induced breakdown spectroscopy (LIBS) uses a focused laser pulse to break down the sample to generate a transient plasma. By detecting the characteristic spectrum emitted by the elements in the sample plasma, the qualitative analysis of the elemental composition in the sample is realized. quantitative analysis. This technology has the characteristics of no need for sample pretreatment, and has the ability of rapid and real-time analysis, so it has received extensive attention. In fields such as elemental composition analysis of smelting products, LIBS technology has been applied in-depth on-site. The application of this technology to the field of component analysis of liquid samples also has a good prospect. It is foreseeable that this technology can play a role in the fields of heavy metal pollution of water resources, detection of marine metal elements, and monitoring of sewage discharged from industrial and mining enterprises. However, when applied to the detection of water body components, due to the influence of the matrix effect and the constraints of related technical characteristics, the sensitivity and stability of LIBS water body detection are affected. Therefore, the online and on-site LIBS detection technology of metal elements in water body has encountered difficulties. The invention utilizes the designed microhole jet continuous sampling device to assist the LIBS detection method to realize continuous on-line LIBS detection of the metal elements in the water body.

Invention content:

The invention uses a specially designed microporous injection device to convert the flowing liquid into dense small droplets on-line and spray them out continuously, and uses a laser pulse to break down the sample in a specific gas environment, and uses a spectral analysis device to analyze the radiation spectrum of the plasma.

The invention can be divided into three parts: a microhole injection device, a laser pulse emission device and a spectrum analysis device. Among them, the microhole injection device is mainly used to convert the flowing liquid into dense small droplets on-line and spray them out continuously; the laser pulse emission device mainly includes a pulse laser and a focusing lens group, which is used to generate the laser pulse required to break through the sample; The spectrum analysis device mainly includes a collection lens group and a spectrometer, which are used to collect the spectral radiation generated by the breakdown.

Description of drawings:

The present invention will be further described below in conjunction with accompanying drawing.

The accompanying drawing is a schematic diagram of a microhole injection-assisted laser breakdown detection device. Among them, 1 is the speed-regulating peristaltic pump, 2 is the sample inlet, 3 is the flow water storage tank, 4 is the drainage hole, 5 is the microporous injection piece, 6 is the injection hole, 7 is the piezoelectric ceramic piece, and 8 is the diversion exhaust Tube, 9 is a buffer waste liquid bottle, 10 is a fan, and the above components form a microhole injection device; 11 is a pulse laser, 12 is a focusing lens group, and the two form a laser pulse emission device; 13 is a collection lens group, and 14 is an optical fiber , 15 is a spectrometer, which forms a spectrum analysis device; 16 is a computer.

Detailed ways:

The present invention is carried out as follows. The liquid sample is injected online into the sample inlet (2) of the injection tank through the peristaltic pump (1), so that the liquid sample flows through the flow water storage tank (3) above the microporous spray sheet (5) at a uniform speed, and the flow water storage tank (3) A part of the liquid sample in ) is under the action of the liquid tension and the high-frequency vibration of the piezoelectric ceramic sheet (7), the small droplet sample is ejected from the injection hole (6) from the other side of the microporous ejection sheet (5), Dense droplets moving at high speed are formed. The remaining sample is drained through the drain hole (4). A diversion exhaust pipe (8), a buffer waste liquid bottle (9) and a fan (10) are selected to form a diversion device. Its function is to generate air flow at the mouth of the diversion exhaust pipe (8) through the fan (10), so that the dense droplet sample is drawn into the exhaust pipe at high speed, and then the shape of the droplet is kept in a stable cylindrical shape. Condensed droplets flow into the buffer waste bottle (9) for collection. The laser pulse emitted by the pulse laser (11) is focused on the top of the diversion exhaust pipe (8) through the focusing lens group (12), so that the laser pulse just hits the edge of the cylindrical dense droplet. The optical radiation produced by the breakdown plasma cooling is collected by the collection lens group (13) and coupled into the optical fiber (14), and split by the fiber optic spectrometer (15), and the spectral signals are displayed and stored by the computer (16).

According to the detection purpose and detection conditions, the size of the hole in the spray area of the atomization sheet can be customized according to the needs, and finally the droplet samples with different diameters can be produced. The inner diameter of the diversion exhaust pipe 8 is usually selected according to the size of the injection area, so as to generate columnar dense droplets with relatively stable flow velocity and shape.

The wavelength of the pulse output by the pulse laser 11 can be arbitrarily selected in the infrared band according to the research purpose; the pulse width can be on the order of nanoseconds or femtoseconds; in order to cover the infrared band, the laser wavelength can be between 532nm and 1064nm Choose between; the energy of the pulse can also be selected according to the needs. After being focused by the focusing lens group 12, in order to reduce the scattering and absorption caused by the dense liquid droplets, the breakdown is selected at the edge of the columnar dense liquid droplets.

The spectrometer 15 is a fiber optic spectrometer with a detection range of 190nm-800nm. When performing component detection and analysis, in order to avoid the continuous background radiation at the initial moment, the spectrum acquisition delay time is selected between 200ns-1500ns.

The computer 16 is used to display and store the spectral signals recorded by the spectrometer 15, and process the signals. Under the same experimental conditions, the concentration of the target element in the droplet sample can be inverted according to the intensity of the characteristic peak of the target element.

The method can limit the volume of the ablated sample droplet, thereby improving the accuracy of quantitative detection. The method can convert the flowing liquid into dense small droplets on-line and spray them out continuously, so that continuous on-line detection of liquid samples can be realized.

Claims (6)

1. A method and device for online detection of elemental components of a liquid sample, the method is characterized in that: The microhole injection device is used as the sampling system for online laser-induced breakdown spectroscopy analysis of liquid samples. The microhole injection device converts the flowing liquid into dense small droplets on-line and sprays them out continuously. Using the laser-induced breakdown device, the breakdown The sample droplets are used for qualitative and quantitative detection of the target elements in the sample through the spectral detection device. The detection device designed by the method is characterized in that: the micro-hole injection device is composed of a peristaltic pump, a micro-hole injection sheet, a sampling tank and a flow guide device. The liquid sample is injected online into the sample inlet (2) of the injection tank through the peristaltic pump (1), so that the liquid sample flows through the flow water storage tank (3) above the microporous spray sheet (5) at a uniform speed, and the flow water storage tank (3) A part of the liquid sample in ) is under the action of the liquid tension and the high-frequency vibration of the piezoelectric ceramic sheet (7), the small droplet sample is ejected from the injection hole (6) from the other side of the microporous ejection sheet (5), Dense liquid droplets moving at high speed are formed. The remaining sample is discharged by the drain hole (4). A diversion exhaust pipe (8), a buffer waste liquid bottle (9) and a fan (10) are selected to form a diversion device. Its function is to generate air flow at the mouth of the diversion exhaust pipe (8) through the fan (10), so that the dense droplet sample is drawn into the exhaust pipe at high speed, and then the shape of the droplet is kept in a stable cylindrical shape. Condensed droplets flow into the buffer waste bottle (9) for collection. The spectral detection method is characterized in that: the laser pulse emitted by the pulse laser (11) is focused on the top of the diversion exhaust pipe (8) through the focusing lens group (12), so that the laser pulse just hits the cylindrical dense liquid edge of the drop. The optical radiation produced by the breakdown plasma cooling is collected by the collection lens group (13) and coupled into the optical fiber (14), and split by the fiber optic spectrometer (15), and the spectral signals are displayed and stored by the computer (16). 2. The microporous injection device according to claim 1, characterized in that it can continuously inject samples and convert the liquid samples into dense small droplets online and in real time and spray them out continuously. 3. The injection area and the guide exhaust pipe according to claim 2, characterized in that the diameters of the holes of the two are matched. 4. The pulse laser according to claim 2, characterized in that the output laser pulse beam is focused on the edge of the columnar dense liquid droplet, and the laser wavelength can be selected between 532nm and 1064nm. 5. The spectrometer according to claim 2, characterized in that according to the requirements of the detection target, its working spectral range is between 190nm and 800nm. 6. The detection method according to claim 2, characterized in that according to the requirements of the detection target, the acquisition gate delay time of the detector is selected between 200ns-1500ns.