CN108802009B - Method for detecting heavy metal by using plasma atomic emission spectrometer - Google Patents
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Abstract
The invention relates to a method for detecting heavy metals by using a plasma atomic emission spectrometer, which solves the technical problems of inconvenient operation in the process of detecting heavy metals, large optical signal loss, high detection cost, low efficiency and low speed caused by serious pollution of a window sheet in the prior art. The invention provides a method for detecting heavy metals by using a plasma atomic emission spectrometer, which sequentially comprises the following steps: (1) firstly, a working air source is introduced into an air inlet branch pipe from an air inlet; (2) after preparing a gaseous sample to be detected, generating stable plasma in a plasma excitation area through a plasma excitation device; (3) after entering the plasma excitation area, the gaseous sample to be tested is excited by the plasma to generate a corresponding characteristic optical signal, and then the characteristic optical signal is transmitted out through the window sheet along the inner part of the main pipe through the lighting port opposite to the direction of the air outlet and enters the spectrometer to obtain the spectral information of the atoms of the sample to be tested. The invention is widely applied to the field of spectrometers of analytical instruments.
Description
Technical Field
The invention relates to the field of spectrometers of analytical instruments, in particular to a method for detecting heavy metals by using a plasma atomic emission spectrometer.
Background
With the globalization of environmental pollution, the society has higher and higher attention to heavy metal pollution in soil, the existing soil heavy metal detection method usually utilizes methods such as atomic absorption spectroscopy, inductively coupled plasma atomic emission spectroscopy, atomic fluorescence spectroscopy and the like to analyze and detect the treated soil solution, the whole detection process is complicated, the instrument volume is large, the detection cost is high, and the method is difficult to be widely applied to on-site rapid detection.
The front optical path system of the existing spectrometer mainly focuses light into the optical fiber through the lens firstly, and then transmits the light into the spectrometer through the optical fiber, if the mode adopted by a Houxian lamp team is adopted, the lens is used for focusing and the optical fiber is used for transmitting, on one hand, the collection efficiency of signal light can be reduced, partial energy is lost, on the other hand, the optical path structure is complex, the operation is inconvenient, and especially, the optical fiber is difficult to be applied to a portable instrument. There is also a scheme of adopting lens, and the spectrometer is replaced by the light splitting detection system, and the optical fiber is saved. However, there is a drawback that light collection at the air outlet end is difficult to overcome, and when detecting solid and other liquid samples with high concentration, the atomized sample air flow contains many solid impurities, which easily pollute the condenser lens when the air flow exits. Therefore, the scheme adopts the mode that the high-transparency window piece is placed in front of the lens to protect the lens, so that the window piece needs to be cleaned before each test, the operation is very inconvenient, the cost is increased, and the efficiency is also reduced.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a method for detecting heavy metals by using a plasma atomic emission spectrometer, which is convenient to operate, does not need to repeatedly clean a window sheet, has small optical signal loss, low detection cost and high efficiency, and has high detection speed.
The technical scheme adopted by the invention for solving the technical problem is as follows:
a method for detecting heavy metals by using a plasma atomic emission spectrometer sequentially comprises the following steps:
(1) opening an airflow control valve of the gas path system, introducing a working gas source into the gas inlet branch pipe from the gas inlet, sequentially entering the main pipe and the plasma excitation area, and finally discharging from the gas outlet;
(2) after preparing a gaseous sample to be tested, applying high-voltage pulse voltage to discharge electrodes in a plasma excitation device through a power supply unit to generate stable plasma between the discharge electrodes, namely generating stable plasma in a plasma excitation area;
(3) a gaseous sample to be detected is brought into the main pipe from the air inlet of the air inlet branch pipe under the drive of a working air source, then enters a plasma excitation area to be excited by plasma, metal atoms in the gaseous sample to be detected are excited by the plasma and then change from a ground state into an unstable excited state, corresponding characteristic light signals are generated when the excited state returns to the ground state, the characteristic light signals are transmitted along the interior of the main pipe, are transmitted out through a window piece through a light collecting port opposite to an air outlet in direction, enter a spectrometer through a collimator and are collected and processed, and finally, spectral information of elements of the sample to be detected is obtained, so that the qualitative analysis or the quantitative analysis of the elements of the sample to be detected is realized; and simultaneously, the residues in the gaseous sample to be detected are discharged through the air outlet under the driving of the working air source.
Preferably, the working gas source is an inert gas, and the inert gas is argon or helium.
Preferably, the plasma atomic emission spectrometer comprises a front light path system, a light splitting detection system, a display control module, a gas path system and a battery, wherein the light splitting detection system comprises a photoelectric conversion and signal processing module, and is connected with the display control module and controlled by the display control module; the front light path system is provided with a main pipe and an air inlet branch pipe, the main pipe is a hollow straight pipe, and openings at two ends of the main pipe are respectively provided with a lighting port and an air outlet; a window sheet is arranged at the lighting port, and the lighting port is sealed through the window sheet; one end of the air inlet branch pipe is provided with an air inlet, the other end of the air inlet branch pipe is fixedly connected with the main pipe, the air inlet branch pipe and the main pipe are arranged in a Y-shaped pipeline, an included angle between the air inlet branch pipe and the main pipe close to one end of the lighting port is 0-90 degrees, and the interior of the air inlet branch pipe is communicated with the interior of the main pipe; a plasma excitation area is arranged on the main pipe between the interface of the air inlet branch pipe and the main pipe and the air outlet, a plasma excitation device and a power supply unit are arranged on the outer wall of the plasma excitation area, the plasma excitation device is provided with a discharge electrode, the power supply unit is connected with the discharge electrode, and high-voltage pulse voltage is applied to the discharge electrode through the power supply unit to generate plasma in the plasma excitation area; the gas circuit system is provided with a working gas source, and the working gas source enters the front light path system from the gas inlet.
Preferably, in the step (2), the preparation of the gaseous sample to be detected is obtained by adopting an electrothermal evaporation mode, and the method comprises the following steps: the electrothermal evaporation device is provided with an electric heating wire, the liquid to be detected is dripped onto the electric heating wire, current is applied to the electric heating wire, the magnitude and time of the current applied to the electric heating wire are changed through the electrothermal evaporation device, and the removal of the solvent in the extracting solution, the ashing of the matrix and the evaporation of the element to be detected are sequentially realized to form a gaseous sample to be detected.
Preferably, in the step (3), the qualitative analysis process of the sample to be tested: and determining the type of the metal element in the sample to be detected according to the characteristic light signal emitted by the metal element in the solution to be detected.
Preferably, in the step (3), the quantitative analysis process of the sample to be tested comprises the following steps:
(1) preparation of standard working curve: preparing a standard series concentration solution of a metal element to be detected, detecting the standard series concentration solution by using a plasma emission spectrometer with a front light path system, and fitting a standard curve according to the intensity change of a characteristic light signal to obtain a standard working curve of the characteristic light signal intensity and the metal element concentration;
(2) and (3) measuring the intensity of the characteristic light signal emitted by the metal element to be detected in the solution to be detected under the condition of the same detection parameters as those in the step (1), and determining the concentration of the metal element in the sample solution to be detected according to the standard working curve of the intensity of the characteristic light signal and the concentration of the metal element prepared in the step (1).
The invention has the beneficial effects that: the method for detecting the heavy metal by using the plasma atomic emission spectrometer is simple and reasonable in principle, convenient to use and operate, free of repeatedly cleaning a window sheet, low in optical signal loss and high in detection efficiency.
(1) The working principle of the method for detecting heavy metal by using the plasma atomic emission spectrometer is that a working gas source is introduced into a gas inlet branch pipe from a gas inlet, gas carrying a sample to be detected enters a main pipe from the gas inlet of the gas inlet branch pipe under the drive of the working gas source and then enters a plasma excitation area, the gas is excited by plasma in the plasma excitation area, metal atoms are changed into an unstable excited state from a ground state after being excited by the plasma, corresponding characteristic light signals are generated when the metal atoms return to the ground state from the excited state, the characteristic light signals are transmitted out through a light collecting port in the opposite direction to a gas outlet along the inside of the main pipe, pass through a collimator, enter the spectrometer, are collected and processed, and finally spectral information of the heavy metal of the sample to be detected is obtained, so that the analysis of the metal elements of the sample to be detected is realized. And meanwhile, the residues in the sample are driven by a working air source to be discharged through an air outlet.
Compared with the use mode that the window sheet is fixed at the air outlet in the front light path system with the traditional structure and then the light is collected at the air outlet, the invention adopts the Y-shaped pipeline design to collect the light at the lighting port opposite to the air outlet, so that the pollution of residues in a sample to the window sheet in the use process can be avoided, the complicated step of cleaning the window sheet before detection is omitted, the loss of equipment in the use process is reduced, and the maintenance cost is reduced.
(2) The method for detecting the heavy metal by using the plasma atomic emission spectrometer adopts the collimator to be directly connected with the spectrometer, removes optical fibers, shortens the light path, obviously reduces the loss of optical signals, and improves the transmission and collection efficiency of light, thereby improving the detection efficiency and sensitivity of the whole optical instrument.
(3) The method for detecting the heavy metal by using the plasma atomic emission spectrometer has the advantages of simple operation and high detection speed, and can realize on-site rapid detection.
Drawings
FIG. 1 is a schematic structural diagram of a front optical path system of a plasma atomic emission spectrometer according to embodiment 1 of the present invention;
fig. 2 is a schematic structural diagram of a front optical path system of a plasma atomic emission spectrometer according to embodiment 2 of the present invention.
The labels in the figure are: 1. the plasma generating device comprises a main pipe, 2 parts of an air inlet branch pipe, 3 parts of an air inlet, 4 parts of an air outlet, 5 parts of a lighting port, 6 parts of a plasma excitation area, 7 parts of a window sheet, 8 parts of a collimator, 9 parts of a spectrometer, 10 parts of a discharge electrode, 11 parts of a power supply unit, 12 parts of an electric heating wire and 13 parts of an electric heating evaporation device.
Detailed Description
The invention is further described below in conjunction with the drawings and the specific embodiments to assist in understanding the contents of the invention. The method used in the invention is a conventional production method if no special provisions are made; the starting materials used, unless otherwise specified, are conventional commercial products.
Example 1
The invention discloses a method for detecting heavy metals by using a plasma atomic emission spectrometer, which is characterized in that the plasma atomic emission spectrometer with a front light path system comprises the front light path system, a light splitting detection system, a display control module, a gas path system and a battery, wherein the light splitting detection system comprises a photoelectric conversion and signal processing module, and is connected with the display control module and controlled by the display control module; the battery is respectively connected with the light splitting detection system and the display control module and respectively supplies power to the light splitting detection system and the display control module; the gas path system is provided with a working gas source and a gas flow control valve, wherein the gas flow control valve is connected with the working gas source, the working gas source is inert gas, and the inert gas is argon or helium.
As shown in FIG. 1, the front optical path system of the plasma atomic emission spectrometer of the present invention is provided with a main pipe 1 and an air inlet branch pipe 2, wherein the main pipe 1 and the air inlet branch pipe 2 are made of quartz glass. The main pipe 1 is a hollow straight pipe, and openings at two ends of the main pipe are respectively provided with a lighting port 5 and an air outlet 4; the outlet of the lighting port 5 is also provided with a window sheet 7, and the lighting port 5 is sealed by the window sheet 7, so that the main pipe 1 forms a structure that one end of the lighting port 5 is sealed with the outside and one end of the air outlet 4 is communicated with the outside. One end of the air inlet branch pipe 2 is provided with an air inlet 3, the other end of the air inlet branch pipe 2 is fixedly connected with the main pipe 1 through melting, the air inlet branch pipe 2 and the main pipe 1 are arranged in a Y shape, the inside of the air inlet branch pipe 2 is communicated with the inside of the main pipe 1, and a plasma excitation area 6 is arranged on the main pipe 1 between the interface of the air inlet branch pipe 2 and the main pipe 1 and the air outlet 4; the included angle alpha between the air inlet branch pipe 2 and the main pipe 1 close to one end of the lighting port 5 is 20 degrees, and the inclined included angle alpha is an acute angle, so that the air flow of a working air source can more smoothly enter the plasma excitation area 6 in the main pipe 1 from the air inlet branch pipe 2 in the using process, and the transmission of the air flow carrying the sample to be tested is facilitated. Meanwhile, the distance from the window sheet 7 to the interface between the air inlet branch pipe 2 and the main pipe 1 is 10mm, and a certain airflow dead zone is formed at one end, close to the lighting port 5, in the main pipe 1, so that long-term cleaning of the window sheet 7 and the airflow dead zone is facilitated, and the influence of impurities on a detection result is reduced.
A dielectric barrier discharge plasma excitation device and a power supply unit 11 are arranged on the outer wall of the plasma excitation area 6, the plasma excitation device is provided with a discharge electrode 10, the power supply unit 11 is connected with the discharge electrode 10, and high-voltage pulse voltage is applied to the discharge electrode 10 in the plasma excitation device through the power supply unit 11, so that plasma is generated in the plasma excitation area 6; the plasma excitation device adopts a dielectric barrier discharge excitation mode, has the advantages of simple structure, small volume and low cost, and can carry out more convenient and rapid qualitative and quantitative analysis on the metal elements in the sample.
The spectrometer 9 is provided with a collimator 8 fixedly connected with the spectrometer 9, and the collimator 8 is directly arranged on a light inlet of the spectrometer 9, so that the installation is convenient. The collimator 8 is internally provided with a focusing lens made of an ultraviolet fused quartz lens, the central axis of the lens coincides with the central axis of the main pipe, the parameters of the quartz lens are matched with the slit parameters of the spectrometer, the collimator 8 can completely focus light into the spectrometer 9, and the focal length of the lens is 10mm for the marine optical series spectrometer 9. The window sheet 7 is fixedly connected with the lighting port 5 in a sealing way; when the types of detection elements are not limited, most of characteristic peaks of heavy metal elements are concentrated in an ultraviolet region, and an ultraviolet high-transmittance quartz glass sheet is adopted, so that light rays in the ultraviolet region in the characteristic peaks of the metal elements have high transmittance, the characteristic light loss of the metal elements in the determination process is reduced to the maximum extent, the detection error is small, and the determination accuracy is high.
The invention discloses a method for detecting heavy metals by using a plasma atomic emission spectrometer, which sequentially comprises the following steps:
(1) opening an airflow control valve of the gas path system, introducing a working gas source into the gas inlet branch pipe 2 from the gas inlet 3, sequentially entering the main pipe 1 and the plasma excitation area 6, and finally discharging from the gas outlet 4;
(2) after preparing a gaseous sample to be tested, applying high-voltage pulse voltage to the discharge electrodes 10 in the plasma excitation device through the power supply unit 11 to generate stable plasma between the discharge electrodes 10, namely generating stable plasma in the plasma excitation area 6;
(3) a gaseous sample to be detected is brought into the main pipe 1 from the air inlet 3 of the air inlet branch pipe 2 under the drive of a working air source, then enters the plasma excitation area 6 and is excited by the plasma, metal atoms in the gas of the sample to be detected are excited by the plasma and then change from a ground state into an unstable excited state, and then corresponding characteristic optical signals are generated when the excited state returns to the ground state, and then the characteristic optical signals are transmitted out along the inside of the main pipe 1 through a light collecting port 5 opposite to the opening direction of the air outlet 4 through a window sheet 7, pass through a collimator 8, enter a spectrometer 9 and are collected and processed, and finally, the spectral information of the sample element to be detected is obtained, so that the analysis of the heavy metal element of the sample to be detected is realized; meanwhile, the residue in the sample is driven by the working gas source to be discharged through the gas outlet 4.
Compared with the method for using the optical signal which is collected at the gas outlet 4 and is fixed at the window piece 7 in the front optical path system with the traditional structure, the method adopts the Y-shaped pipeline design, the optical signal is collected at the light collecting port 5 which is opposite to the gas outlet 4, the pollution of impurities in the airflow to the window piece 7 can be avoided, the complicated step of cleaning the window piece 7 before detection is omitted, simultaneously, the metal atoms are changed into an unstable excited state from a ground state after being excited by plasma, and then the corresponding characteristic optical signal is generated when the metal atoms return to the ground state from the excited state, the optical signal is transmitted through the window piece 7 through the light collecting port 5 which is opposite to the gas outlet 4, enters the spectrometer 9 through the collimator 8 and is collected and processed, the traditional optical fiber transmission is not needed in the using process, the loss in the characteristic optical signal transmission process is obviously reduced, the detection error is reduced, the accuracy of detection is improved, and qualitative and quantitative detection of the metal elements to be detected in the sample to be detected is realized.
The above is only an embodiment of the present invention, and for example, the included angle α between the air intake branch pipe 2 and the main pipe 1 near the daylight opening 5 is any acute angle from 0 ° to 90 °, preferably from 5 ° to 45 °; preferably, the distance from the window sheet 7 to the interface between the air inlet branch pipe 2 and the main pipe 1 is 8-30 mm; the window sheet 7 can select a required filter sheet according to element detection requirements, such as an ultraviolet filter, a cut-off filter and the like; the main pipe 1 and the air inlet branch pipe 2 can be made of any transparent insulating medium; any other excitation mode capable of generating plasma in the plasma excitation area 6 can adopt a front light path system, and the method disclosed by the invention can be used for realizing heavy metal detection and analysis.
The method for detecting the heavy metal by using the plasma atomic emission spectrometer has the advantages of simple operation and high detection speed, and can realize on-site rapid detection; by detecting and analyzing the plasma atomic spectrum and adopting the Y-shaped pipeline design, the pollution of residues in a sample to the window sheet in the using process is avoided, the complicated step of cleaning the window sheet before detection is omitted, and the maintenance cost is reduced. The collimator is directly connected with the spectrometer, optical fibers are removed, the optical path is shortened, the loss of optical signals is obviously reduced, the transmission and collection efficiency of light is improved, and therefore the detection efficiency and sensitivity of the whole optical instrument are improved.
Example 2
The method for detecting heavy metals by using the plasma atomic emission spectrometer with the optical path system in front of the plasma atomic emission spectrometer in the embodiment 1 is shown in fig. 2, and sequentially comprises the following steps:
(1) preparation of a solution to be tested: extracting the metal elements in the soil sample by using an extractant diethyltriamine pentaacetic acid or a dilute acid solution in an extraction mode to obtain a solution to be detected.
(2) Firstly, opening an airflow control valve of the gas path system, introducing an inert gas working gas source into a gas inlet branch pipe 2 from a gas inlet 3, then sequentially entering a main pipe 1 and a plasma excitation area 6, and finally discharging from a gas outlet 4; the inert gas is argon.
(3) Preparing a gaseous sample to be detected by adopting an electrothermal evaporation mode:
and (2) connecting an outlet of an electrothermal evaporation device 13 with an air inlet 3 of an air inlet branch pipe 2 in a sealing and through manner, arranging an electric heating wire 12 on the electrothermal evaporation device 13, aligning the electric heating wire 12 with the air inlet 3 of the air inlet branch pipe 2, dropwise adding the liquid to be detected prepared in the step (1) onto the electric heating wire 12, applying different currents to the electric heating wire 12 through the electrothermal evaporation device 13, sequentially removing the solvent and the matrix in the liquid to be detected, and closing the current of the electric heating wire 12.
(4) A high-voltage pulse voltage is applied to the discharge electrodes 10 in the plasma excitation device by the power supply unit 11, so that stable plasma is generated between the discharge electrodes 10, that is, stable plasma is generated in the plasma excitation region 6.
(5) Then, a high current is applied to the heating wire 12 by the electrothermal evaporation device 13, so that the metal atoms to be detected are vaporized and evaporated to form a gaseous sample to be detected. A gaseous sample to be detected is brought into the main pipe 1 from the air inlet 3 of the air inlet branch pipe 2 under the drive of a working air source, then enters the plasma excitation area 6 to be excited by plasma, metal atoms in the gas of the sample to be detected are excited by the plasma and then change from a ground state to an unstable excited state, corresponding characteristic optical signals are generated when the excited state returns to the ground state, then the characteristic optical signals are transmitted out along the inside of the main pipe 1 through a light collecting port 5 opposite to the opening direction of the air outlet 4 through a window sheet 7, pass through a collimator 8 and enter a spectrometer 9 to be collected and processed, and finally, the spectral information of the element of the sample to be detected is obtained, so that the qualitative analysis or the quantitative analysis of the element component of the sample to be detected is realized; meanwhile, the residue in the sample is driven by the working gas source to be discharged through the gas outlet 4.
(6) Removing residues: and then the current applied to the heating wire 12 is increased and changed, and the residue on the heating wire 12 is removed, so that the detection of the next sample is facilitated.
(7) The qualitative analysis method for the sample to be detected comprises the following steps: and determining the type of the metal element in the sample to be detected according to the spectral line wavelength of the characteristic light signal emitted by the metal element in the solution to be detected.
(8) The quantitative analysis process of the sample to be detected comprises the following steps:
a. preparation of standard working curve: preparing a standard series concentration solution of a metal element to be detected, detecting the standard series concentration solution by using a plasma atomic emission spectrometer with a front optical path system, and fitting a standard curve according to the intensity change of a characteristic light signal to obtain a standard working curve of the characteristic light signal intensity and the metal element concentration;
b. and c, under the condition of the same detection parameters as those in the step a, determining the characteristic optical signal intensity of the metal element to be detected in the solution to be detected, and determining the concentration of the metal element in the sample solution to be detected according to the standard working curve of the characteristic optical signal intensity and the concentration of the metal element prepared in the step a.
Example 3
The following will describe the detection method and performance evaluation of the present invention by taking the test of available lead in soil as an example.
The method for detecting lead in soil by using the plasma atomic emission spectrometer with the front optical path system in the embodiment 2 is shown in fig. 2, and sequentially comprises the following steps:
(1) preparation of a solution to be tested: taking 1g of soil sample, leaching for two hours by using 5ml of diethylenetriaminepentaacetic acid extractant, filtering leaching liquor to obtain liquid to be detected, and directly detecting the liquid to be detected.
(2) Firstly, opening an airflow control valve of the gas path system, introducing an inert gas working gas source into a gas inlet branch pipe 2 from a gas inlet 3, then sequentially entering a main pipe 1 and a plasma excitation area 6, and finally discharging from a gas outlet 4; the inert gas is argon, and the gas flow rate is 0.3L/min.
(3) With the sealed through connection of electric heat evaporation device 13's export and the air inlet 3 of air inlet branch 2, electric heat evaporation device 13 is equipped with heating wire 12, aims at air inlet 3 department of air inlet branch 2 with heating wire 12, will wait to detect liquid dropwise add to heating wire 12 that step (1) made, applys different electric currents to heating wire 12 simultaneously and carries out solvent and matrix in proper order and get rid of, electric current size and duration are in proper order: the water removal current is 1.0A, and the water removal time is 120 s; ashing current was 1.4A, and after 30s of ashing time, the current to the heating wire 12 was turned off.
(4) Then, a high-voltage pulse voltage is applied to the discharge electrodes 10 in the plasma excitation device through the power supply unit 11, so that stable plasma is generated between the discharge electrodes 10, that is, stable plasma is generated in the plasma excitation region 6. After the plasma is stably generated for 10s, the electric heating wire is applied with evaporation current of 4.0A, the evaporation time is 3s, and the lead element attached to the electric heating wire 12 is directly and instantly gasified and atomized.
(5) Gaseous lead atoms prepared in the step (4) are brought into the main pipe 1 from the air inlet 3 of the air inlet branch pipe 2 under the drive of a working air source, then enter a plasma excitation area 6 to be excited by plasma, the gaseous lead atoms are changed into unstable excited states from ground states after being excited by the plasma, characteristic emission lines of the lead elements are generated when the excited states return to the ground states, optical signals are transmitted out through a window sheet 7 through a light collecting port 5 opposite to an air outlet 4, pass through a collimator 8 and enter a spectrometer 9 to be collected and processed, and finally spectrum information of the lead elements in the sample to be detected is obtained, so that the analysis of the sample to be detected is realized; meanwhile, the residue in the sample is driven by the working gas source to be discharged through the gas outlet 4.
(6) Removing residues: the size of the current applied to the heating wire 12 is increased through the electric heating evaporation device 13, the residual current is removed by 4.6A, the residual time is removed by 2s, and the residues on the heating wire 12 are removed, so that the next sample can be conveniently detected.
(7) And (3) performing qualitative analysis on a sample to be detected: and determining that the lead element is contained in the sample to be detected according to the characteristic emission line 368.347nm emitted from the solution to be detected.
(8) The quantitative analysis process of the sample to be detected comprises the following steps:
a. drawing a lead working curve: 500 mul of lead standard stock solution with the concentration of 1000 mug/ml is taken to be put into a 50ml volumetric flask, and the prepared diethylenetriaminepentaacetic acid (0.005mol/l) is added to the volumetric flask to a constant volume to be a scale mark, wherein the concentration is 10 mug/ml. Taking 50 mul, 100 mul, 200 mul, 500 mul and 1000 mul of the prepared 10 mul/mL lead standard solution to be respectively placed in a 10mL volumetric flask, and fixing the volume by using the diethylenetriamine pentaacetic acid solution to obtain working solutions with the concentrations of 50 mul, 100 mul, 200 mul, 500 mul and 1000 mul. The plasma atomic emission spectrometer with the front optical path system is used for detecting the solutions with the standard series of concentrations, and the 368.347nm peak intensity of the characteristic peak of lead corresponding to the solutions with different concentrations is measured under the optimal condition, which is shown in table 1. Fitting a standard curve according to the change of the characteristic peak intensity to obtain a standard working curve of the characteristic light signal intensity and the lead element concentration, wherein the linear regression equation is as follows: y is 11.943X-427.444, and the correlation coefficient is 0.9993, which fully proves that the detection method of the invention has wide linear range.
b. And c, under the condition of the same detection parameters as those in the step a, measuring the emission characteristic optical signal intensity of the lead in the solution to be detected, and determining the concentration of the effective lead in the sample solution to be detected according to the standard working curve of the measured characteristic optical signal intensity and the concentration of the lead element. Taking a national standard substance (GBW07458, the effective Pb calibration content of DTPA leaching method is 2.07 +/-0.17 mg/kg) as a sample to be detected, and measuring the content as follows: 1.76 ± 0.11mg/kg, RSD 6% was determined in parallel 6 experiments. The result shows that the method has high accuracy and good repeatability, and can be used for rapidly detecting the effective heavy metal in the soil.
TABLE 1 lead Standard solution corresponding Strength Table
Therefore, in the method for detecting the heavy metal by using the plasma atomic emission spectrometer, only the sample needs to be prepared into a simple solution, interference factors are few in the determination process, the linear range is wide, and the detection speed is high; through the detection and analysis of the plasma atomic emission spectrum, optical signals can directly enter the spectrometer through the collimator without being transmitted through optical fibers, and the method has the advantages of small measurement error of metal elements, high precision and good accuracy.
With the globalization of environmental pollution, the society has higher and higher attention to heavy metal pollution in soil, the existing soil heavy metal detection method usually utilizes methods such as atomic absorption spectroscopy, inductively coupled plasma atomic emission spectroscopy, atomic fluorescence spectroscopy and the like to analyze and detect the treated soil solution, the whole detection process is complicated, the instrument volume is large, the detection cost is high, and the method is difficult to be widely applied to on-site rapid detection. The method for detecting the heavy metal by using the plasma atomic emission spectrometer is simple and easy to implement, has few interference factors in the determination process, wide linear range and high detection speed, and can realize on-site rapid detection; by adopting the Y-shaped pipeline design and the front optical path system of the collimator, optical signals can directly enter the spectrometer through the collimator without optical fiber transmission or window cleaning, the measurement error of metal elements is small, the accuracy is high, the repeatability is good, and the on-site rapid detection requirement on the heavy metal elements in the soil can be met.
However, the above description is only an embodiment of the present invention, and the scope of the present invention should not be limited thereto, for example, the inert gas is helium, or a mixture of gases, etc., and all equivalent changes and modifications made according to the claims of the present invention should be covered by the present invention.
Claims (6)
1. A method for detecting heavy metals by using a plasma atomic emission spectrometer is characterized by sequentially comprising the following steps:
(1) opening an airflow control valve of the gas path system, introducing a working gas source into the gas inlet branch pipe from the gas inlet, sequentially entering the main pipe and the plasma excitation area, and finally discharging from the gas outlet;
(2) after preparing a gaseous sample to be tested, applying high-voltage pulse voltage to discharge electrodes in a plasma excitation device through a power supply unit to generate stable plasma between the discharge electrodes, namely generating stable plasma in a plasma excitation area;
(3) the gas-state sample to be detected is brought into the main pipe from the air inlet of the air inlet branch pipe under the drive of a working air source, then enters the plasma excitation area to be excited by the plasma, metal atoms in the gas-state sample to be detected are changed into an unstable excited state from a ground state after being excited by the plasma, corresponding characteristic optical signals are generated when the excited state returns to the ground state, the characteristic optical signals are transmitted along the inside of the main pipe, are transmitted out through the window piece through the light collecting port opposite to the air outlet direction, pass through the collimator, enter the spectrometer, are collected and processed, and finally spectral information of the atoms of the sample to be detected is obtained, so that the qualitative analysis or the quantitative analysis of the element components of the sample to be detected is realized; meanwhile, the residues in the gaseous sample to be detected are discharged through the air outlet under the driving of a working air source;
an airflow dead zone is formed at one end, close to the lighting opening, in the main pipe; the included angle between the air inlet branch pipe and the main pipe close to one end of the lighting port is an acute angle.
2. The method for detecting heavy metals by using a plasma atomic emission spectrometer according to claim 1, wherein the working gas source is an inert gas, and the inert gas is argon or helium.
3. The method for detecting heavy metals by using a plasma atomic emission spectrometer as claimed in claim 1, wherein the plasma atomic emission spectrometer comprises a front optical path system, a light splitting detection system, a display control module, an air path system and a battery, the light splitting detection system comprises a photoelectric conversion and signal processing module, and the light splitting detection system is connected with the display control module and is controlled by the display control module; the front light path system is provided with a main pipe and an air inlet branch pipe, the main pipe is a hollow straight pipe, and openings at two ends of the main pipe are respectively provided with a lighting port and an air outlet; the lighting opening is provided with a window sheet, and the lighting opening is sealed through the window sheet; an air inlet is formed in one end of the air inlet branch pipe, the other end of the air inlet branch pipe is fixedly connected with the main pipe, the air inlet branch pipe and the main pipe are arranged in a Y-shaped pipeline, the air inlet branch pipe is close to the lighting opening, an included angle between the air inlet branch pipe and the main pipe close to one end of the lighting opening is 0-90 degrees, and the interior of the air inlet branch pipe is communicated with the interior of the main pipe; a plasma excitation area is arranged on the main pipe between the interface of the air inlet branch pipe and the main pipe and the air outlet, a plasma excitation device and a power supply unit are arranged on the outer wall of the plasma excitation area, the plasma excitation device is provided with a discharge electrode, the power supply unit is connected with the discharge electrode, and high-voltage pulse voltage is applied to the discharge electrode through the power supply unit to enable plasma to be generated in the plasma excitation area; the gas circuit system is provided with a working gas source, and the working gas source enters the front light path system from the gas inlet.
4. The method for detecting heavy metals by using a plasma atomic emission spectrometer according to claim 1, wherein in the step (2), the preparation of the gaseous sample to be detected is obtained by means of electrothermal evaporation, and the method comprises the following steps: the electrothermal evaporation device is provided with a heating wire, the liquid to be detected is dripped onto the heating wire, current is applied to the heating wire, the magnitude and time of the current applied to the heating wire are changed through the electrothermal evaporation device, and the removal of the solvent in the extracting solution, the ashing of the matrix and the evaporation of the element to be detected are sequentially realized to form the gaseous sample to be detected.
5. The method for detecting heavy metals by using a plasma atomic emission spectrometer according to claim 1, wherein in the step (3), the qualitative analysis process of the sample to be detected comprises the following steps: and determining the type of the metal element in the sample to be detected according to the characteristic light signal emitted by the metal element in the solution to be detected.
6. The method for detecting heavy metals by using a plasma atomic emission spectrometer according to claim 3, wherein in the step (3), the quantitative analysis process of the sample to be detected comprises the following steps:
(1) preparation of standard working curve: preparing a standard series concentration solution of a metal element to be detected, detecting the standard series concentration solution by using a plasma emission spectrometer with the front light path system, and fitting a standard curve according to the intensity change of a characteristic light signal to obtain a standard working curve of the characteristic light signal intensity and the metal element concentration;
(2) and (3) measuring the characteristic light signal intensity of the metal element to be measured in the solution to be measured under the condition of the same detection parameters as those in the step (1), and determining the concentration of the metal element in the sample solution to be measured according to the standard working curve of the characteristic light signal intensity and the concentration of the metal element prepared in the step (1).
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| CN111595833A (en) * | 2020-06-09 | 2020-08-28 | 哈尔滨工业大学（威海） | Rapid detection method for trace heavy metals in human blood |
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