CN114813708A - Method for analyzing trace Pb element in aqueous solution by combining electrodeposition and SD-LIBS - Google Patents

Method for analyzing trace Pb element in aqueous solution by combining electrodeposition and SD-LIBS Download PDF

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CN114813708A
CN114813708A CN202210478484.5A CN202210478484A CN114813708A CN 114813708 A CN114813708 A CN 114813708A CN 202210478484 A CN202210478484 A CN 202210478484A CN 114813708 A CN114813708 A CN 114813708A
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electrodeposition
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陈安民
王秋云
姜远飞
李苏宇
金明星
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Jilin University
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Abstract

The invention is suitable for the field of heavy metal pollution analysis, and provides a method for analyzing trace Pb element in an aqueous solution by combining electrodeposition and SD-LIBS (spark discharge assisted laser induced breakdown spectroscopy). the method adopts an electrodeposition method to enrich the trace heavy metal Pb element in the aqueous solution on the surface of a high-purity Al plate under an enrichment voltage of 8V and an enrichment time of 10min, so that the problems of low sensitivity and low accuracy when the LIBS directly detects a water sample are solved; detecting Pb element on the surface of the Al plate by adopting an SD-LIBS (secure digital-LiBS) technology so as to enhance the emission intensity of Pb (I); and calibration curves of Pb (I) at 405.78nm at different discharge voltages are plotted, wherein the slope (S) of the calibration curve increases and the detection limit (LoD) decreases as the discharge voltage increases. Therefore, the electrodeposition method and the SD-LIBS technology are combined to realize high-sensitivity detection of trace heavy metal elements in the aqueous solution.

Description

Method for analyzing trace Pb element in aqueous solution by combining electrodeposition and SD-LIBS
Technical Field
The invention belongs to the field of heavy metal pollution analysis, and particularly relates to a method for analyzing trace Pb element in an aqueous solution by combining electrodeposition and SD-LIBS.
Background
Due to the rapid development of economy, the daily lives of industry, agriculture and human beings have caused serious water pollution. The increasing amount of metal waste in water poses a potential threat to human health and life. Therefore, development of a high-sensitivity water environment monitoring technology is particularly necessary. Currently, common water environment monitoring techniques can be classified into the following types: electrochemical analysis, spectrophotometry, atomic fluorescence spectroscopy, atomic absorption spectroscopy, inductively coupled plasma emission spectroscopy, and inductively coupled plasma mass spectroscopy. Although the method has high measurement precision, the method needs complex sample pretreatment, lacks the capability of quick, real-time, on-line and multi-element simultaneous analysis, and is difficult to meet the requirement of water pollution monitoring. The above problems are solved by the Laser Induced Breakdown Spectroscopy (LIBS) technique, which has the following unique advantages: 1. the equipment is simple and the operability is good; 2. the ability to detect solids, liquids, gases, aerosols, and the like; 3. detecting multiple elements simultaneously; 4. the sample preparation is simple or does not need sample preparation; 5. micro-destructive measurements; 6. detecting on site, on line and in real time; 7. and (4) remote detection. Therefore, LIBS has been applied to many fields such as environmental pollution detection, harmful substance detection, handicrafts detection, space exploration, and archaeological exploration.
When LIBS analyzes trace elements in a liquid matrix, liquid sputtering and liquid level fluctuation are easily generated when liquid is irradiated by laser, and evaporated liquid can absorb and scatter laser, so that the efficiency of laser ablation of the liquid is greatly reduced. Therefore, direct laser ablation of the liquid results in short plasma lifetime, weak emission intensity, large spectral fluctuations, and affects the sensitivity and accuracy of LIBS detection. In order to avoid the above technical difficulties, researchers have made many improvements: 1. liquid flow method: converting the solution from a static state to a flowing state by using a liquid column method (jet method), a liquid drop method, a laminar flow method, an atomization method, or the like; 2. an instrument method comprises the following steps: auxiliary equipment is added on the basis of a liquid flow method to improve the LIBS detection capability, and the LIBS detection capability comprises a double-pulse LIBS, a laser-induced fluorescence LIBS, a magnetic confinement LIBS and a microwave-assisted LIBS; 3. and (3) a curing method: converting liquids to solids includes electrodeposition, freezing, adsorption, and surface enhancement. The electrodeposition method is characterized in that cations in an aqueous solution to be detected are enriched on the surface of an electrode by utilizing a displacement technology of a conductive electrode, and a liquid sample is converted into a solid sample. The breakdown threshold of a solid sample is lower compared to a liquid sample, and therefore its elemental emission intensity is higher. In addition, Spark Discharge (SD) is a simple and effective re-excitation source for enhancing the emission of LIBS, and the combination of SD and LIBS is called spark discharge assisted LIBS (SD-LIBS). The SD re-ignites the plasma to gain more energy. More particles in the plasma absorb energy and are excited to a higher energy level. SD-LIBS can increase plasma lifetime, emission intensity, spectral signal-to-noise ratio, plasma temperature, and electron density compared to conventional LIBS. In addition, the SD in the SD-LIBS does not cause further damage to the sample, so that the SD-LIBS is a good spectral analysis technology. In order to improve the detection sensitivity of LIBS to the heavy metal elements in the aqueous solution, it is necessary to further study the influence of the electrodeposition method and SD-LIBS combination on the detection sensitivity of the heavy metal elements in the aqueous solution.
Disclosure of Invention
An object of an embodiment of the present invention is to provide a method for analyzing trace Pb elements by electrodeposition in combination with SD-LIBS, which is intended to solve the problems set forth in the background art described above.
In order to achieve the purpose, the invention provides the following technical scheme:
the method for analyzing the trace Pb element by combining the electrodeposition and the SD-LIBS comprises the following steps:
step one, sample preparation: using deionized water and Pb (NO) 3 ) 2 Powder preparation of Pb (NO) of various concentrations 3 ) 2 A standard aqueous solution;
step two, electrodeposition: putting an Al plate with the purity of 99.9% into alcohol and deionized water for ultrasonic treatment, putting a beaker filled with an aqueous solution to be analyzed on a magnetic stirrer, using the Al plate as an anode and a cathode, adding 8V direct-current voltage to the anode and the cathode, moving cations in the solution to the surface of the Al plate of the cathode under the action of an electric field to obtain electrons, depositing the electrons on the surface of the Al plate of the cathode, and after 10min, sucking the solution on the surface of the Al plate by using cleaning paper to dry the solution for LIBS analysis;
step three, LIBS analysis: analyzing Pb element by an SD-LIBS experimental device;
and step four, analyzing the throughput.
Further, deionized water and Pb (NO) were used 3 ) 2 Powder preparation of Pb (NO) of various concentrations 3 ) 2 The specific operation of the standard aqueous solution is as follows:
a. weighing Pb (NO) using an electronic balance 3 ) 2 Powder, wherein the weighing range of the electronic balance is 0.01g-100 g;
b. putting the weighed powder into a 1000mL volumetric flask, adding nitric acid and deionized water to dissolve the powder, diluting the powder to a scale with deionized water, and shaking up to obtain a stock solution;
c. before use, 10mL of stock solution is measured, placed in a 1000mL volumetric flask, diluted to the scale with deionized water and shaken up to obtain a sample.
Furthermore, the SD-LIBS experimental device consists of a light source, a three-dimensional translation table, a high-voltage discharge system, a spectrometer and ICCD system and a computer.
Further, the light source is a Q-switched Nd-YAG laser system, the pulse width is 10ns, the wavelength is 1064nm, and the repetition frequency is 1Hz
Further, the positive electrode and the negative electrode of the high-voltage discharge system are respectively a Cu needle and an Al plate, and the Cu needle is placed at a position 3mm away from the surface of the Al plate.
Further, the specific operation of analyzing the Pb element by the SD-LIBS experimental apparatus is as follows:
laser is vertically focused to the surface of the Al plate through a reflector, a diaphragm and a focusing lens to generate laser-induced plasma, the focusing distance of the focusing lens is 23cm, the diameter of a light spot is 500 mu m, and the energy density of the laser is 6.8J/cm 2 (ii) a Fixing an Al plate on a three-dimensional translation table vertical to the laser direction, collecting plasma emission by a lens with the focal length of 75mm and the diameter of 50mm, and introducing the plasma emission into a spectrometer and ICCD system by an optical fiber; the photodiode triggers the ICCD to synchronize the delay time between the laser and plasma emission.
Further, the gate delay of the ICCD is 0.5 μ s, and the gate width of the ICCD is 50 μ s.
Further, the speed of the three-dimensional translation stage is 1 mm/s.
Compared with the prior art, the invention has the beneficial effects that:
the invention adopts an electrodeposition method, under the enrichment voltage of 8V and the enrichment time of 10min, the trace heavy metal Pb element in the aqueous solution is enriched on the surface of the high-purity Al plate, and the problems of low sensitivity and low accuracy when the LIBS directly detects a water sample are solved; detecting Pb element on the surface of the Al plate by adopting an SD-LIBS (secure digital-optical lateral-field) technology so as to enhance the emission intensity of Pb (I); calibration curves for pb (i) at 405.78nm were plotted at different discharge voltages (0kV, 2kV and 4kV), with the slope (S) of the calibration curve increasing and the limit of detection (LoD) decreasing with increasing discharge voltage. Therefore, the electrodeposition method and the SD-LIBS technology can realize high-sensitivity detection of trace heavy metal elements in the aqueous solution.
Drawings
FIG. 1 shows schematic diagrams of electrodeposition schematic diagram (a) and SD-LIBS experimental apparatus (b) (wherein M is a mirror, I is a diaphragm, L is a focusing lens, and Pd is a photodiode) in the present invention.
FIG. 2 is a spectrum of Pb (I) at 405.78nm at different Pb concentrations and different discharge voltages in accordance with the present invention; the discharge voltages are 0kV (a), 2kV (b) and 4kV (c), respectively; pb concentrations of 60ng/mL (a), 120ng/mL (b), and 200ng/mL (c), respectively.
FIG. 3 is a graph showing the peak intensity of Pb (I)405.78nm as a function of discharge voltage (0kV, 2kV, 4kV) at different Pb concentrations (60ng/mL, 120ng/mL, 200ng/mL) in the present invention.
FIG. 4 is a calibration curve of Pb (I) at 405.78nm for different discharge voltages (0kV, 2kV, 4kV) in the present invention.
FIG. 5 is a graph showing the correlation between the prepared concentration and the predicted concentration at different discharge voltages (0kV, 2kV and 4kV) in the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Specific implementations of the present invention are described in detail below with reference to specific embodiments.
The method for analyzing the trace Pb element by combining the electrodeposition and the SD-LIBS, which is provided by the embodiment of the invention, comprises the following steps:
step one, sample preparation: using deionized water and Pb (NO) 3 ) 2 Powder preparation of Pb (NO) of various concentrations 3 ) 2 A standard aqueous solution;
step two, electrodeposition: putting an Al plate with the purity of 99.9 percent into alcohol and deionized water for ultrasonic treatment, putting a Beaker (Beaker) filled with an aqueous solution to be analyzed on a Magnetic stirring device (Magnetic stirring apparatus), using the Al plate as an Anode and a Cathode, adding 8V direct current Voltage (DC Voltage) to the Anode (Al Anode) and the Cathode (Al Cathodode), moving cations in the solution to the surface of the Al plate of the Cathode under the action of an electric field to obtain electrons, depositing the electrons on the surface of the Al plate of the Cathode, and after 10min, sucking the solution on the surface of the Al plate by using cleaning paper for LIBS analysis;
step three, LIBS analysis: analyzing Pb element by an SD-LIBS experimental device;
and step four, analyzing the throughput.
In the present example, in order to establish a calibration curve of the Pb element, a series of reference samples of known concentrations must be prepared. Using deionized water and Pb (NO3) 2 Preparation of powders with varying concentrations of Pb (NO3) 2 Standard aqueous solutions, as shown in table 1.
Table 1 standard aqueous solution concentrations were prepared.
Figure BDA0003626686450000051
FIG. 1(a) shows the electrodeposition scheme. Magnetic stirring bar is a Magnetic stirring rod; putting some Al plates with the purity of 99.9% into alcohol and deionized water for ultrasonic treatment (15min) to ensure that the surface of the Al plate is free of impurities, putting a beaker filled with an aqueous solution to be analyzed on a magnetic stirrer, and continuously stirring the solution by the magnetic stirrer in the electrodeposition process to ensure the uniformity of the concentration of metal ions in the solution; the Al plates serve as an anode and a cathode. A dc voltage of 8V was applied to the two electrodes. Under the action of an electric field, cations in the solution move to the surface of the Al plate of the negative electrode to obtain electrons, the electrons are deposited on the surface of the Al plate of the negative electrode, and after 10min, the solution on the surface of the Al plate is sucked and dried by cleaning paper and is used for LIBS analysis. Step four, analyzing throughput: in the experiment, only one electrodeposition device is used, the time for depositing the Al plate is 10min, the laser repetition frequency is 1Hz, all spectral data are average values measured by 20 laser pulses, and the acquisition time is not more than one min because the acquisition system is automatic. Therefore, the total time of electrodeposition and measurement does not exceed 11 min. Further, assuming that ten electrodeposition devices continuously perform the measurement, the measurement time per sample is only 2 min.
As a preferred embodiment of the present invention, deionized water and Pb (NO) are used 3 ) 2 Powder preparation of Pb (NO) of various concentrations 3 ) 2 The specific operation of the standard aqueous solution is as follows:
a. weighing Pb (NO) using an electronic balance 3 ) 2 Powder, wherein the weighing range of the electronic balance is 0.01g-100 g;
b. putting the weighed powder into a 1000mL volumetric flask, adding nitric acid and deionized water to dissolve the powder, diluting the powder to a scale with deionized water, and shaking up to obtain a stock solution;
c. before use, 10mL of stock solution is measured, placed in a 1000mL volumetric flask, diluted to the mark with deionized water and shaken well to obtain a Sample (Sample).
In the present example, Pb (NO) was weighed using an electronic balance 3 ) 2 Powder (0.160g, purity greater than 99.0%). Pb (NO) 3 ) 2 The powder was from national pharmaceutical group chemical agents limited (china); putting the weighed powder into a 1000mL volumetric flask, adding nitric acid (5mL) and deionized water (50mL) to dissolve the powder, diluting the powder to a scale with deionized water, and shaking up to obtain a stock solution; accurately measuring 10mL of stock solution before use, placing in a 1000mL measuring flask, diluting to scale with deionized water and shaking up to obtainObtaining a sample (1 mL per 1. mu.g of Pb); the authenticity of the Pb measurement was confirmed by comparing the spectrum of the preparation solution with the spectrum of the authentication solution.
As a preferred embodiment of the invention, the SD-LIBS experimental device consists of a light source, a three-dimensional translation stage, a high voltage discharge system (highVoltage), a spectrometer + ICCD system and a computer.
As a preferred embodiment of the invention, the light source is a Q-switched Nd: YAG laser system with a pulse width of 10ns, a wavelength of 1064nm and a repetition frequency of 1 Hz.
In the embodiment of the invention, the light source is a Q-switched Nd: YAG (continuous, Laser III) Laser system (Laser system).
As a preferred embodiment of the present invention, the positive electrode and the negative electrode of the high voltage discharge system are a Cu needle and an Al plate, respectively, and the Cu needle is placed at a position 3mm from the surface of the Al plate.
As a preferred embodiment of the present invention, the specific operation of the SD-LIBS experimental apparatus for analyzing Pb element is as follows:
the laser is vertically focused to the surface of the Al plate through a reflector, a diaphragm and a focusing lens to generate laser-induced plasma, the focusing distance of the focusing lens is 23cm, the spot diameter is 500 mu m, and the laser energy density is 6.8J/cm 2 (ii) a Fixing an Al plate on a three-dimensional translation table vertical to the laser direction, collecting plasma emission by a lens with the focal length of 75mm and the diameter of 50mm, and leading the plasma emission to a Spectrometer (Spectrometer) + ICCD system by an optical Fiber (Fiber); the photodiode triggers the ICCD to synchronize the delay time between the laser and plasma emission.
In the present example, an Al plate was fixed on a three-dimensional translation stage (PT 3/M-Z8; Thorlabs, USA) perpendicular to the laser direction to ensure that each laser beam irradiated to a new sample surface; the plasma emission was collected by a lens with a focal length of 75mm and a diameter of 50mm and directed by an optical fiber into a spectrometer (SP-500i, PI-Acton, 1200 lines/mm grating) + ICCD (PIMAX4, Princeton instruments, USA, 1024i) system. The photodiode (Pd) triggers the ICCD to synchronize the delay time between the laser and plasma emission.
As a preferred embodiment of the invention, the gate delay of the ICCD is 0.5 μ s and the width of the ICCD is 50 μ s.
In an embodiment of the present invention, the gate delay of the ICCD is set to 0.5 μ s and the gate width of the ICCD is set to 50 μ s to reduce the effect of continuous emission and collect as much of the spectral signal as possible.
As a preferred embodiment of the invention, the speed of the three-dimensional translation stage is 1 mm/s.
In an embodiment of the invention, the speed of the three-dimensional translation stage is set to 1mm/s and the laser repetition rate is set to 1Hz to ensure that each laser pulse irradiates a new sample surface.
Results and discussion
First, Pb (I) at 405.78nm was selected as the analysis line. FIG. 2 shows the spectrum of Pb (I) at 405.78nm at discharge voltages of 0kV, 2kV and 4 kV. It is observed from the graph that the line emission of Pb (i)405.78nm increases with increasing Pb concentration. According to theoretical derivation, the number of heavy metal ions N enriched on the surface of the Al plate is related to the element concentration C, the enrichment voltage U, the enrichment time t and the solution volume V as follows:
N＝CV(1-e -AUt ) (1)
wherein A is a constant. As can be seen from equation (1), once the enrichment voltage U, the enrichment time t and the solution volume V are determined, the number of particles N of the heavy metal element is proportional to the element concentration C. Therefore, the number of particles of Pb element increases as the Pb concentration increases. Furthermore, the spectral intensity can be described by the following expression:
Figure BDA0003626686450000081
wherein i and j are upper and lower energy levels, h is Planck's constant, c is the speed of light, gi is the degree of degeneracy, A ij Is the transition probability from i to j, Np is the particle density of the element, E i Is the element energy level, λ ij Is the wavelength, k B Is the boltzmann constant, T is the plasma temperature, and q (T) is the elemental distribution function. From the equation (1) As can be seen from (2) and (2), the linear intensity of Pb (I)405.78nm is proportional to the concentration of Pb element, i.e., the linear emission of Pb (I)405.78nm increases with increasing Pb concentration.
As shown in FIG. 2, the line intensity of Pb (I)405.78nm increases with an increase in discharge voltage. Laser plasma is generated by laser ablation of a sample to be detected, electrons and ions in the plasma rapidly diffuse into a gap between a Cu electrode and an Al target and are accelerated continuously under the action of a strong electric field, collision ionization among particles grows exponentially, a so-called avalanche discharge process is formed, energy is rapidly transferred into the plasma in the process, and therefore reheating of the plasma is achieved. Therefore, the emission intensity of pb (i) using SD is greatly improved, and in addition, as the discharge voltage is increased, the energy of injection into plasma is also increased, and more particles are excited from a low energy level to a high energy level. Therefore, the emission intensity of pb (i) is stronger at a high discharge voltage than at a low discharge voltage, and this phenomenon can be clearly observed from fig. 3. The emission intensity of Pb (i) increases with the increase of the Pb concentration at the same discharge voltage; at the same Pb concentration, the emission intensity of Pb (i) increases with an increase in discharge voltage.
In order to quantitatively analyze the content of Pb element in the aqueous solution, it is necessary to obtain a calibration curve of Pb (i). Calibration curves of the heavy metal Pb element obtained in the present invention at different discharge voltages (0kV, 2kV and 4kV) are shown in FIG. 4. Since the data points in fig. 4 clearly follow a linear trend and self-absorption can be neglected, the curve can be fitted linearly, the expression is as follows:
I＝S·C+b (3)
where I is the spectral signal intensity, S is the analytical sensitivity, i.e. the ratio of the minimum change in the detectable signal intensity to the change in the measured concentration (the slope of the calibration curve), b is a constant (the intercept of the calibration curve), and C is the concentration of the Pb element in the aqueous solution. From fig. 4, the calculated S values for the heavy metal Pb at different discharge voltages are listed in table 2. The S values at 0kV, 2kV and 4kV are 0.0403, 0.1643 and 0.2853 respectively; the corresponding linear equations are I-0.0403 · C +20.0, I-0.1643 · C +24.1 and I-0.2853 · C + 31.4.
TABLE 2 different discharge ratesR of Pb (I) at 405.78nm 2 S, LoD and RSD values
Figure BDA0003626686450000091
By utilizing the calibration curve, the signal intensity of Pb in the unknown environmental water sample can be determined and the concentration of Pb in the unknown environmental water sample can be calculated by using the same analysis process and experiment conditions, so that the aim of quantitative analysis is fulfilled. LoD is determined by the 3 σ rule, described by the following expression:
Figure BDA0003626686450000092
where σ is the standard deviation of the background noise. The LoD of the Pb element at three discharge voltages calculated according to the formula (4) is listed in table 2. It is evident from table 2 that SD-LIBS in combination with electrodeposition significantly increases S and decreases LoD. The LoD with the discharge voltage of 4kV is lower than that of 0kV by one order of magnitude, and the main reason is that SD obviously prolongs the emission life of plasma generated by laser and improves the spectral intensity. Further, in order to evaluate the correlation between the Pb concentration and the Pb (i) intensity, a linear correlation coefficient R was used 2 (coefficient of measurement) to express the degree of correlation. R of Pb (I) at discharge voltages of 0kV, 2kV and 4kV 2 Values of 0.87, 0.93 and 0.95, respectively, as shown in table 2, the correlation between the concentration of Pb element and the Pb (i) intensity increased with the increase in voltage; to further investigate the effect of SD on spectral stability, the Relative Standard Deviation (RSD) of pb (i) was calculated, and as shown in table 2, the RSD values of pb (i) were 20.7, 18.3, and 15.7 at discharge voltages of 0, 2, and 4kV, respectively, and the spectral stability of pb (i) was continuously improved as the discharge voltage was increased. Therefore, the use of SD can improve the correlation and stability of Pb (I) spectral radiation.
Finally, in order to evaluate the accuracy of quantitative analysis of trace Pb element in aqueous solution by electrodeposition combined with SD-LIBS, correlation curves between prepared concentration and predicted concentration were plotted at different discharge voltages (0kV, 2kV and 4kV), as shown in FIG. 5, and the corresponding R was calculated 2 PeaceRelative error of homogeneous (ARE). Table 3 shows the R at different voltages (0kV, 2kV and 4kV) 2 And ARE values. With increasing discharge voltage, R 2 Increasing from 0.91 to 0.97, while ARE decreasing from 10.0% to 7.3%. The results show that the use of SD improves the accuracy of the quantitative analysis. In conclusion, the combination of the electrodeposition and the SD-LIBS can realize the high-sensitivity detection of the trace heavy metal Pb element in the aqueous solution and improve the accuracy of the quantitative analysis of the trace heavy metal Pb element in the aqueous solution.
TABLE 3 precision values of Pb (I) at 405.78nm for different discharge voltages
Figure BDA0003626686450000101
Summary of the invention
The invention enriches trace heavy metal Pb element in the aqueous solution on the surface of the high-purity Al plate by using an electrodeposition method, and qualitatively and quantitatively analyzes Pb (I)405.78nm by using an SD-LIBS (Standard substance-to-Life ratio) technology. Firstly, the spectral radiation of the Pb element under different discharge voltages is qualitatively discussed, so that the spectral radiation of the Pb element can be enhanced to different degrees no matter the discharge voltage is high or low, and the discharge can play a role in re-excitation and re-heating of the plasma; secondly, the LoD of Pb element under the discharge voltage of 0kV, 2kV and 4kV is quantitatively calculated, the LoD of Pb element is respectively 53.5ng/mL, 13.1ng/mL and 7.5ng/mL, and the LoD with the discharge voltage of 4kV is lower than the LoD of 0kV by one order of magnitude, mainly because SD obviously prolongs the emission life of plasma generated by laser and improves the spectral intensity. Therefore, the combination of the electrodeposition and the SD-LIBS can realize the high-sensitivity detection of the heavy metal elements in the aqueous solution and improve the accuracy of the quantitative analysis of the heavy metal elements in the aqueous solution.
The above is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, it is possible to make several variations and modifications without departing from the concept of the present invention, and these should be considered as the protection scope of the present invention, which will not affect the effect of the implementation of the present invention and the practicability of the patent.

Claims (8)

1. The method for analyzing the trace Pb element by combining the electrodeposition and the SD-LIBS is characterized by comprising the following steps:
step one, sample preparation: using deionized water and Pb (NO) 3 ) 2 Powder preparation of Pb (NO) of various concentrations 3 ) 2 A standard aqueous solution;
step two, electrodeposition: putting an Al plate with the purity of 99.9% into alcohol and deionized water for ultrasonic treatment, putting a beaker filled with an aqueous solution to be analyzed on a magnetic stirrer, using the Al plate as an anode and a cathode, adding 8V direct-current voltage to the anode and the cathode, moving cations in the solution to the surface of the Al plate of the cathode under the action of an electric field to obtain electrons, depositing the electrons on the surface of the Al plate of the cathode, and after 10min, sucking the solution on the surface of the Al plate by using cleaning paper to dry the solution for LIBS analysis;
step three, LIBS analysis: analyzing Pb element by an SD-LIBS experimental device;
and step four, analyzing the throughput.
2. The method for analyzing trace Pb element by electrodeposition in combination with SD-LIBS as claimed in claim 1, wherein deionized water and Pb (NO) are used 3 ) 2 Powder preparation of Pb (NO) of various concentrations 3 ) 2 The specific operation of the standard aqueous solution is as follows:
a. weighing Pb (NO) using an electronic balance 3 ) 2 Powder, the weighing range of the electronic balance is 0.01g-100 g;
b. putting the weighed powder into a 1000mL volumetric flask, adding nitric acid and deionized water to dissolve the powder, diluting the powder to a scale with deionized water, and shaking up to obtain a stock solution;
c. before use, 10mL of stock solution is measured, placed in a 1000mL volumetric flask, diluted to the scale with deionized water and shaken up to obtain a sample.
3. The method for analyzing trace Pb element by combining electro-deposition and SD-LIBS according to claim 1, wherein the SD-LIBS experimental device is composed of a light source, a three-dimensional translation stage, a high-voltage discharge system, a spectrometer + ICCD system and a computer.
4. YAG laser system, pulse width is 10ns, wavelength is 1064nm, and repetition frequency is 1 Hz.
5. The method for analyzing trace Pb element by combining electrodeposition with SD-LIBS according to claim 3, wherein the positive electrode and the negative electrode of the high-voltage discharge system are a Cu needle and an Al plate, respectively, and the Cu needle is placed at a position 3mm away from the surface of the Al plate.
6. The method for analyzing the trace Pb element by combining the electrodeposition and the SD-LIBS according to claim 3, wherein the SD-LIBS experimental apparatus is used for analyzing the Pb element by the following specific operations:
laser is vertically focused to the surface of the Al plate through a reflector, a diaphragm and a focusing lens to generate laser-induced plasma, the focusing distance of the focusing lens is 23cm, the diameter of a light spot is 500 mu m, and the energy density of the laser is 6.8J/cm 2 (ii) a Fixing an Al plate on a three-dimensional translation table vertical to the laser direction, collecting plasma emission by a lens with the focal length of 75mm and the diameter of 50mm, and introducing the plasma emission into a spectrometer and ICCD system by an optical fiber; the photodiode triggers the ICCD to synchronize the delay time between the laser and plasma emission.
7. The method for analyzing trace Pb element by electrodeposition in combination with SD-LIBS according to claim 6, wherein the gate delay of ICCD is 0.5 μ s and the gate width of ICCD is 50 μ s.
8. The method for the combined electrodeposition and SD-LIBS analysis of trace Pb elements according to claim 6, characterized in that the speed of the three-dimensional translation stage is 1 mm/s.
CN202210478484.5A 2022-05-05 2022-05-05 Method for analyzing trace Pb element in aqueous solution by combining electrodeposition and SD-LIBS Pending CN114813708A (en)

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