CN117214151A - Quantitative detection method for trace elements in water body - Google Patents
Quantitative detection method for trace elements in water body Download PDFInfo
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Abstract
The invention provides a quantitative detection method of trace elements in a water body, which comprises the following steps: preparing a super-hydrophobic array sensor by using a laser treatment and chemical modification method, and utilizing partial Leidenfrost effect to combine with the super-hydrophobic array sensor to evaporate and enrich trace liquid drops in the solution to be detected so as to obtain an enriched substrate containing the element deposition solute to be detected; detecting and analyzing the solute deposited on the enrichment substrate based on a laser induced breakdown spectroscopy LIBS technology to obtain the spectral intensity corresponding to the maximum signal characteristic spectral peak of the element to be detected; and determining the concentration of the element to be detected in the solution to be detected by combining the calibration curve. The method realizes the ultrafast enrichment of the element to be detected in the water body by combining the super-hydrophobic array sensor based on the partial Leidenfrost effect, and realizes the rapid and ultrasensitive in-situ detection of the element to be detected in the water body by using the laser-induced breakdown spectroscopy technology.
Description
Technical Field
The invention relates to the technical field of environmental protection and water quality detection, in particular to a quantitative detection method for trace elements in a water body.
Background
The detection and analysis of trace elements in water body is an important ring of environmental protection and water quality detection, and especially with the development of society, the disordered emission of industrial wastewater and other pollutants causes serious environmental pollution and threatens the health of human beings. Therefore, developing a rapid, simple in situ detection method for trace elements in a body of water becomes a hot spot and challenge for researchers to chase. In the technical field, methods such as inductively coupled plasma emission spectrometry, inductively coupled plasma mass spectrometry, X-ray fluorescence spectrometry and atomic absorption spectrometry are applied. However, these methods, while highly sensitive, at the same time, expensive equipment, complex process flows and operations result in the above methods being only suitable for laboratory work and difficult to apply to the need for rapid in situ detection of trace elements in water.
The Laser-induced breakdown spectroscopy (Laser-induced breakdown spectroscopy, LIBS) technology has the characteristics of simple structure, high analysis speed and capability of realizing remote, real-time and on-line full-element analysis, and the principle is that high-energy Laser pulses are directly focused on a sample, so that the sample is induced to generate plasma and emit specific spectrum signals, and the element composition and content information in the sample to be detected are obtained by analyzing the wavelength and intensity distribution of an emission spectrum. However, in water body detection, because the element concentration in the solution is generally low, and the absorption and sputtering effects of water on the laser pulse, the sensitivity and stability of LIBS are poor when directly detecting the aqueous solution.
At present, the following methods are mainly applied to quantitative detection of trace elements in a water body based on LIBS technology: LIBS detection method based on nanoparticle field enhancement, LIBS detection method based on spark discharge excitation, dry liquid drop method based on enrichment substrate and the like are proved to be capable of effectively enhancing sensitivity and stability during LIBS detection, but the operation flow of the method is complex, the use cost is high, the pretreatment time is long, and the efficiency during LIBS water trace element detection is greatly affected. Therefore, how to realize ultrasensitive and highly stable LIBS in-situ detection and analysis of trace elements in a water body under the conditions of low detection cost and high detection efficiency has become an urgent problem to be solved in the field.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a quantitative detection method for trace elements in a water body, solves the problems of complex flow, expensive equipment, low treatment efficiency and the like in the conventional sample pretreatment method, and can realize rapid, stable and ultrasensitive LIBS quantitative detection for trace elements in the water body.
The invention is realized by the following technical scheme:
a quantitative detection method of trace elements in a water body comprises the following steps:
(1) Preparing a super-hydrophobic array sensor by using a laser treatment and chemical modification method, wherein the super-hydrophobic array sensor is used for enriching and preprocessing a solution to be detected; the super-hydrophobic array sensor is required to have super-hydrophobic performance, and the super-hydrophobic surface is in an array form;
(2) Extracting a solution to be detected based on a part of Leidenfrost effect and the super-hydrophobic array sensor, and pipetting the solution to be detected to the surface of the super-hydrophobic array sensor for evaporation and enrichment to obtain an enrichment substrate containing solute deposition to be detected;
(3) Placing the enrichment substrate containing the solute sediment to be detected obtained in the step (2) in a LIBS detection system, and ablating the solute to be detected by using pulse laser to obtain a LIBS full spectrum of the solution to be detected;
(4) Processing the LIBS spectrum of the solution to be detected obtained in the step (3) to obtain the spectrum intensity corresponding to the maximum signal characteristic spectrum peak of the element to be detected in the full spectrum;
(5) Preparing a plurality of standard solutions containing solutes to be detected with different concentrations, and obtaining the spectral intensities containing the solutes to be detected with different concentrations according to the methods described in the steps (1) - (4);
(6) Establishing a calibration curve required during quantitative analysis, and calculating concentration values of elements to be detected in the solution to be detected; the calibration curve is established by fitting the spectral intensities of solutes to be detected and the corresponding element concentrations thereof in a plurality of standard solutions with known concentrations obtained in the step (5), and is used for constructing a linear relation between the concentration values of the elements to be detected and the spectral intensities corresponding to the maximum signal characteristic spectral peaks;
(7) Fitting the spectral intensity corresponding to the maximum signal characteristic spectral peak of the element to be measured in the solution to be measured extracted in the step (4) with a calibration curve to obtain an element concentration value corresponding to the spectral intensity in the calibration curve, namely the concentration value of the element to be measured in the solution to be measured.
Further, the preparation method of the superhydrophobic array sensor in the step (1) is as follows:
(1.1) placing a sensor substrate which is ultrasonically cleaned by using absolute ethyl alcohol and deionized water and dried in an infrared micro/nano processing system, and carrying out surface treatment by a picosecond laser to obtain a substrate with an array surface;
(1.2) the tridecaffein triethoxysilane solution was combined with absolute ethanol in a ratio of 1:99 to obtain the super-hydrophobic chemical modifier with the mass fraction of 1%wt;
(1.3) immersing the substrate with the array surface in the super-hydrophobic chemical modifier for 20 minutes, and then taking out to obtain a chemically modified substrate;
and (1.4) placing the chemically modified substrate on the surface of a heating platform at 80 ℃ for 10-20 minutes, and removing the residual chemical modifier on the surface of the substrate to obtain the super-hydrophobic array sensor.
Further, the specific method for evaporation enrichment in the step (2) is as follows: the super-hydrophobic array sensor is placed on the surface of a constant-temperature heating platform for heating and heat preservation, the solution to be detected is extracted through a micropipette and is pipetted to the super-hydrophobic array surface of the sensor for evaporation and enrichment, and along with gradual evaporation of the solvent in the solution to be detected, the solute to be detected is gradually separated out and forms small-area solute deposition in a short time, so that the evaporation and enrichment are completed.
Further, the heating and heat preserving temperature of the super-hydrophobic array sensor in the step (3) is 130-140 ℃; the volume of the solution to be detected is 50 mu L; the solute deposition time is 3-4 minutes; the solute deposition area has a diameter of 300 to 350 μm.
The invention has the following beneficial effects:
1) The invention provides a method for realizing rapid and stable enrichment pretreatment of a solution to be detected by utilizing partial Leidenfrost effect combined with a super-hydrophobic array sensor, and is firstly applied to quantitative detection of trace elements in a water body by LIBS. Compared with the traditional enrichment pretreatment method, the method has the advantages of high efficiency, good enrichment effect and simple and convenient pretreatment process.
2) The invention provides a super-hydrophobic array sensor which is used as a substrate to realize evaporation enrichment of a solution to be detected, wherein the super-hydrophobic array sensor is used for preparing a super-hydrophobic array surface with stable structure on the surface of an Al substrate by using a laser treatment and chemical modification method, the Al substrate has good heat conduction performance, the super-hydrophobic array on the surface of the sensor can realize synchronous enrichment of a plurality of solution drops to be detected, and the characteristics can greatly improve the pretreatment efficiency of a sensor sample.
3) According to the invention, the rapid and stable enrichment pretreatment of the solution to be tested is realized by combining partial Leidenfrost effect with the super-hydrophobic array sensor, compared with the traditional super-hydrophobic surface (without combining partial Leidenfrost effect), a dense steam layer is formed at the bottom of the liquid drop of the solution to be tested on the super-hydrophobic array surface under the action of partial Leidenfrost effect, so that the static contact angle is further increased, the contact area between the liquid drop and the surface is reduced, the deposition area of solute in the solution to be tested is reduced, and the coffee ring structure possibly occurring in enrichment is avoided. In addition, the solution to be detected is enriched on the surface of the high Wen Zhenlie, so that the evaporation pretreatment efficiency is improved.
4) Compared with enrichment of the solution to be tested on the super-hydrophobic surface of the non-combined part of the Leidenfrost effect, the method has the advantages that the air is filled in the micro/nano structure of the super-hydrophobic surface, the solution to be tested is easy to roll on the surface of the micro/nano structure, so that the in-situ enrichment cannot be realized, and a liquid bridge (air bubble) is formed at the contact part of the bottom of the solution to be tested and the super-hydrophobic surface under the action of part of the Leidenfrost effect, so that the solution to be tested is bound on the super-hydrophobic surface, and the in-situ enrichment is realized.
5) The invention adopts a brand new enrichment scheme to pretreat the solution to be detected, thereby realizing the ultrasensitive LIBS quantitative detection of trace elements in the water body. Compared with the traditional LIBS sample pretreatment method, the method provided by the invention can realize stable and in-situ enrichment of the solution to be detected in a short time, reduce the enrichment area of solute in the solution to be detected, ensure that the detection limit of the LIBS to be detected element is as low as ng/L, ensure that the relative standard deviation of LIBS data of 10 times of repeated detection is only 3.7%, and is a novel rapid, stable and ultrasensitive LIBS quantitative detection method.
6) The method provided by the invention realizes the efficient and stable liquid-solid conversion of the solution to be detected, eliminates the effects of plasma quenching, liquid splashing, energy absorption and the like when the LIBS detects the solution sample, and greatly improves the sensitivity and stability of the LIBS detection.
Drawings
FIG. 1 is a schematic diagram of a flow chart for evaporating and enriching a solution to be detected based on a partial Leidenfrost effect combined with a super-hydrophobic array sensor;
FIG. 2 is a schematic diagram of the LIBS detection system provided by the invention;
FIG. 3 is a plot of the evaporative enrichment behavior of 5. Mu.L of the test solution on a super-hydrophobic array sensor.
FIG. 4 is a graph showing the variation of the signal intensity of LIBS of the solute to be detected under different enrichment conditions;
FIG. 5 is a schematic illustration of a solute to be measured deposited in different areas of a superhydrophobic array sensor provided by the invention;
FIG. 6 is a graph showing LIBS signal intensity variation of a solute to be measured deposited in different areas on a superhydrophobic array sensor provided by the invention;
FIG. 7 is a LIBS spectral variation of different concentration Be solutions deposited on a superhydrophobic array sensor provided by the invention;
FIG. 8 is a LIBS spectral variation of Cu solutions of different concentrations deposited on a superhydrophobic array sensor provided by the invention;
Detailed Description
The invention will be described in further detail with reference to the drawings and the detailed description.
The invention provides a quantitative detection method of trace elements in a water body, which comprises the following steps:
(1) Preparing a super-hydrophobic array sensor by using a laser treatment and chemical modification method, wherein the super-hydrophobic array sensor is used for enriching and preprocessing a solution to be detected;
the super-hydrophobic array sensor has excellent super-hydrophobic performance (contact angle is more than 150 degrees, rolling angle is less than 10 degrees), and the super-hydrophobic surface is prepared into an array form so as to meet the requirement of synchronous enrichment of multiple groups of solutions to be detected and improve the pretreatment efficiency of samples.
The super-hydrophobic array sensor can be prepared by the following steps:
(1.1) placing a sensor substrate which is sequentially ultrasonically cleaned by using absolute ethyl alcohol and deionized water and dried in an infrared micro/nano processing system, and carrying out surface treatment by a picosecond laser to obtain a substrate with an array surface; the sensor substrate can be aluminum sheet or other flat metal substrate with excellent heat conduction performance, such as copper sheet, silicon wafer and the like, so that the heat conduction performance of the sensor can be improved, and the time required by sample pretreatment can be reduced.
(1.2) the tridecaffein triethoxysilane solution was combined with absolute ethanol in a ratio of 1:99 to obtain the super-hydrophobic chemical modifier with the mass fraction of 1%wt;
(1.3) immersing the substrate with the array surface in the super-hydrophobic chemical modifier for 20 minutes, and then taking out to obtain a chemically modified substrate;
(1.4) placing the chemically modified substrate on the surface of a heating platform at 80 ℃ for 10-20 minutes, and removing the residual chemical modifier on the surface of the substrate to obtain the super-hydrophobic array sensor;
(2) Based on the partial leidenfrost effect and the super-hydrophobic array sensor, the solution to be tested is subjected to evaporation enrichment (shown in figure 1). The super-hydrophobic array sensor 104 is placed on the surface of the constant-temperature heating platform 101 for heating and heat preservation, the solution to be detected is extracted through the micropipette 102 and is pipetted to the super-hydrophobic array surface of the sensor for evaporation enrichment, and as the solvent in the solution to be detected is gradually evaporated, the solute to be detected is gradually separated out and forms a small-area solute deposit 103 in a short time.
Preferably, the heating and heat preserving temperature of the super-hydrophobic array sensor 104 is 130-140 ℃; the volume of the solution to be detected is 50 mu L; the solute deposition time is 3-4 minutes; the solute deposition area has a diameter of 300 to 350 μm.
It can be appreciated that the enrichment method based on partial leidenfrost effect combined with the superhydrophobic surface can further improve the contact angle of the trace liquid drop, and compared with enrichment of the trace liquid drop by the superhydrophobic surface in an untreated surface or low-temperature environment, the enrichment method reduces the contact area of the liquid drop and the substrate and increases the temperature of the substrate surface, thereby reducing the area for enriching the solute and the time for evaporating the solvent.
(3) Placing the super-hydrophobic array sensor 104 containing the solute deposit to be detected, which is obtained in the step (2), in a LIBS detection system, and ablating the solute to be detected by using pulse laser to obtain the LIBS full spectrum of the solution to be detected.
As shown in fig. 2, the LIBS detection system includes a first focusing mirror 201 (f 1 =200 mm), dichroic mirror 202, beam splitter 203, photodiode 204, timing signal output line 205, laser 206, laser control signal line 207, spectrometer 208, optical fiber 209, optical fiber holder 210, second focusing mirror 211 (f) 2 =100 mm), a spectrometer control signal line 212, a computer 213 and a three-coordinate displacement platform 214.
Placing the super-hydrophobic array sensor 104 containing solute deposition to be detected on a three-coordinate displacement platform 214, splitting a pulse laser beam emitted by a laser 206 by a beam splitter 203, vertically incidence 90% of the pulse laser beam to a dichroic mirror 202, and focusing on the surface of the super-hydrophobic array sensor 215 by a first focusing mirror 201; another, i.e., 10%, pulse laser light is coupled to the photodiode 204, which converts the optical signal to a high-level electrical signal via photoelectric conversion for triggering the spectrometer 208, thus reducing the cost of the detection device and the sensitivity of external triggering. The plasma emission light in the LIBS detection system is coupled into the spectrometer 208 through the optical fiber 209 in a coaxial acquisition mode, namely, the plasma emission light is coupled into the spectrometer 208 through the first focusing mirror 201, the dichroic mirror 202 and the second focusing mirror 211 through the optical fiber 209, and the plasma emission light acquisition optical path is coaxial with the laser optical path, so that the plasma emission light acquisition efficiency can be improved, and the signal acquisition capability of the LIBS system can be enhanced.
(4) And (3) processing the LIBS spectrum of the solution to be detected obtained in the step (3) to obtain the spectrum intensity corresponding to the maximum signal characteristic spectrum peak of the element to be detected in the full spectrum.
(5) Preparing standard solutions with different concentrations, and obtaining LIBS spectrum intensities containing solutes with different concentrations to be detected, wherein the LIBS spectrum intensities are used for carrying out LIBS quantitative analysis on a solution to be detected containing elements with unknown concentrations to be detected;
preferably, the standard solution is configured from a known concentration of the element to be tested and deionized water.
It can be understood that the LIBS spectrum intensities containing solutes to be measured with different concentrations are LIBS spectrum intensities corresponding to the maximum signal characteristic spectrum peak in the atomic emission spectrum of the known element in the standard solution.
(6) Establishing a calibration curve required during quantitative analysis, and calculating concentration values of elements to be detected in the solution to be detected;
it can be understood that the calibration curve is established by fitting the signal intensities of the LIBS characteristic spectrum peaks of the element to be detected in the standard solutions with known concentrations and the corresponding element concentrations, and is used for constructing the linear relation between the concentration values of the element to be detected and the LIBS spectrum intensities corresponding to the maximum signal characteristic spectrum peaks.
(7) And determining the concentration of the element to be detected in the solution to be detected based on the spectral intensity and the calibration curve corresponding to the maximum signal characteristic spectral peak of the element to be detected. Fitting the spectral intensity corresponding to the maximum signal characteristic spectral peak of the element to be detected in the solution to be detected extracted in the step (4) with a calibration curve to obtain the element concentration value corresponding to the spectral intensity in the calibration curve.
The following examples are only illustrative of the present invention and are not intended to limit the scope of the invention.
Example 1
1) Sequentially using absolute ethyl alcohol and deionized water to ultrasonically clean an Al sheet for 10 minutes, drying, using an infrared micro/nano processing system to carry out laser surface treatment, soaking the Al sheet subjected to laser treatment in a chemical modifier for 20 minutes, and placing the modified Al sheet on a heating platform at 80 ℃ to evaporate and remove the chemical modifier remained on the surface to obtain the super-hydrophobic array sensor for later use.
2) And placing the super-hydrophobic array sensor on a heating table, heating to 135 ℃, fully heating the sensor, homogenizing the surface temperature and preserving heat for later use. 50 mu L of Be solution with the concentration of 5 mu g/L is instilled on the surface area of the super-hydrophobic array of the sensor, and the liquid drops are rapidly enriched in situ by utilizing the partial Frout effect and the super-hydrophobic surface. As the solvent evaporates, the drop volume gradually decreases, and for about 3-4 minutes, the solvent evaporates completely, and the solute to be measured is deposited on the superhydrophobic array surface area of the sensor.
3) And detecting and analyzing the solute to be detected deposited on the super-hydrophobic array sensor by using a LIBS detection system to obtain the LIBS full spectrum of the solution to be detected.
4) And processing the LIBS full spectrum of the solution to be detected, and extracting the spectrum intensity corresponding to the maximum signal characteristic spectrum peak of the element to be detected in the full spectrum.
Example 2
1) Sequentially using absolute ethyl alcohol and deionized water to ultrasonically clean the Al sheet for 10 minutes and drying to obtain an untreated Al sheet for later use.
2) And placing the untreated Al sheet on a heating table, heating to 80 ℃, fully heating the Al sheet, homogenizing the surface temperature and preserving heat for later use. And (3) dripping 50 mu L of Be solution with the concentration of 5 mu g/L on the surface of the untreated Al sheet, gradually reducing the liquid drop volume along with the evaporation of the solvent, and completely evaporating the solvent for about 10 minutes, wherein the solute to Be detected is deposited on the surface of the untreated Al sheet.
3) And detecting and analyzing the solute to be detected deposited on the surface of the untreated Al sheet by using a LIBS detection system to obtain the LIBS full spectrum of the solution to be detected.
4) And processing the LIBS full spectrum of the solution to be detected, and extracting the spectrum intensity corresponding to the maximum signal characteristic spectrum peak of the element to be detected in the full spectrum.
Example 3
1) Sequentially using absolute ethyl alcohol and deionized water to ultrasonically clean the Al sheet for 10 minutes and drying to obtain the solute-free Al sheet for later use.
2) And (3) detecting and analyzing the surface of the solute-free Al sheet by using a LIBS detection system to obtain the LIBS full spectrum of the surface.
3) And processing the LIBS full spectrum of the surface, and extracting the spectrum intensity corresponding to the Be element maximum signal characteristic spectrum peak in the full spectrum.
Example 4
1) Sequentially using absolute ethyl alcohol and deionized water to ultrasonically clean an Al sheet for 10 minutes, drying, using an infrared micro/nano processing system to carry out laser surface treatment, soaking the Al sheet subjected to laser treatment in a chemical modifier for 20 minutes, and placing the modified Al sheet on a heating platform at 80 ℃ to evaporate and remove the chemical modifier remained on the surface to obtain the super-hydrophobic array sensor for later use.
2) And placing the super-hydrophobic array sensor on a heating table, heating to 135 ℃, fully heating the sensor, homogenizing the surface temperature and preserving heat for later use. 10 groups of 50 mu L Be solutions with the concentration of 5 mu g/L are respectively instilled on 10 different super-hydrophobic array surface areas of the sensor, and liquid drops are rapidly enriched in situ by utilizing the partial Frout effect and the super-hydrophobic surface. As the solvent evaporates, the drop volume gradually decreases, and for about 3-4 minutes, the solvent evaporates completely, and 10 sets of solutes to be measured are deposited on 10 different superhydrophobic array surface regions of the sensor.
3) And respectively detecting and analyzing 10 groups of solutes to be detected deposited on the super-hydrophobic array sensor by using a LIBS detection system to obtain LIBS full spectra of 10 groups of solutions to be detected.
4) And (3) processing the LIBS full spectrums of the 10 groups of solutions to be tested, and extracting the spectrum intensity corresponding to the maximum signal characteristic spectrum peak of the element to be tested in the 10 different full spectrums.
Example 5
1) Sequentially using absolute ethyl alcohol and deionized water to ultrasonically clean an Al sheet for 10 minutes, drying, using an infrared micro/nano processing system to carry out laser surface treatment, soaking the Al sheet subjected to laser treatment in a chemical modifier for 20 minutes, and placing the modified Al sheet on a heating platform at 80 ℃ to evaporate and remove the chemical modifier remained on the surface to obtain the super-hydrophobic array sensor for later use.
2) And placing the super-hydrophobic array sensor on a heating table, heating to 135 ℃, fully heating the sensor, homogenizing the surface temperature and preserving heat for later use. 50 mu L of Be solution with different concentrations is respectively instilled on different super-hydrophobic array surface areas of the sensor, and liquid drops are rapidly enriched in situ by utilizing partial Frout effect and super-hydrophobic surface. As the solvent evaporates, the drop volume gradually decreases, and the solvent evaporates completely for about 3-4 minutes, and the solute to be measured with different concentrations is deposited on the surface area of the superhydrophobic array of the sensor.
3) And respectively detecting and analyzing the solutes to be detected with different concentrations deposited on the super-hydrophobic array sensor by using a LIBS detection system to obtain LIBS full spectra of the solutions to be detected with different concentrations.
4) And processing LIBS full spectra of the solutions to be detected with different concentrations, and extracting spectral intensities corresponding to maximum signal characteristic spectral peaks of the elements to be detected with different concentrations in the full spectra.
Example 6
1) Sequentially using absolute ethyl alcohol and deionized water to ultrasonically clean an Al sheet for 10 minutes, drying, using an infrared micro/nano processing system to carry out laser surface treatment, soaking the Al sheet subjected to laser treatment in a chemical modifier for 20 minutes, and placing the modified Al sheet on a heating platform at 80 ℃ to evaporate and remove the chemical modifier remained on the surface to obtain the super-hydrophobic array sensor for later use.
2) And placing the super-hydrophobic array sensor on a heating table, heating to 135 ℃, fully heating the sensor, homogenizing the surface temperature and preserving heat for later use. And (3) respectively instilling 50 mu L of Cu solutions with different concentrations on different superhydrophobic array surface areas of the sensor, and rapidly enriching liquid drops in situ by utilizing partial Leidenfrost effect and superhydrophobic surface. As the solvent evaporates, the drop volume gradually decreases, and the solvent evaporates completely for about 3-4 minutes, and the solute to be measured with different concentrations is deposited on the surface area of the superhydrophobic array of the sensor.
3) And respectively detecting and analyzing the solutes to be detected with different concentrations deposited on the super-hydrophobic array sensor by using a LIBS detection system to obtain LIBS full spectra of the solutions to be detected with different concentrations.
4) And processing LIBS full spectra of the solutions to be detected with different concentrations, and extracting spectral intensities corresponding to maximum signal characteristic spectral peaks of the elements to be detected with different concentrations in the full spectra.
The maximum signal characteristic spectrum peak of Be element in examples 1-5 corresponds to a wavelength of 313.04nm.
The wavelength corresponding to the peak of the maximum signal characteristic of the Cu element in example 6 is 324.754nm.
The Be solution concentrations in example 5 were 10. Mu.g/L, 1. Mu.g/L and 0. Mu.g/L, respectively.
The Cu solutions in example 6 had concentrations of 10. Mu.g/L, 0.1. Mu.g/L and 0. Mu.g/L, respectively.
Fig. 3 shows the evaporation and enrichment behavior characteristics of 5 μl of the solution to be tested on the superhydrophobic array sensor, which indicates that under the action of partial leidenfrost effect combined with the superhydrophobic surface, the solvent in the solution to be tested evaporates rapidly, the droplet becomes smaller gradually, and finally the solution to be tested is deposited on the superhydrophobic surface, i.e. the solution to be tested can be enriched rapidly and stably in situ in the superhydrophobic region.
Examples 1-3, the results of the spectral intensities corresponding to the maximum signal characteristic peaks (BeII 313.04 nm) of the elements to Be detected in the solute deposition under different conditions are shown in FIG. 4, and 50. Mu.L of Be solution with the concentration of 5. Mu.g/L is deposited on the surface of the super-hydrophobic array sensor to obtain the maximum LIBS signal intensity.
FIG. 5 is a three-dimensional morphology diagram of a 10-group solution to be measured with a concentration of 50 [ mu ] L deposited solute on the surfaces of different super-hydrophobic arrays of the same sensor, wherein the diameter of a white dotted circle is 350 [ mu ] m, and it can be understood that the diameter of the deposition area of the 10-group solution to be measured does not exceed 350 [ mu ] m, and the capability of greatly improving sample enrichment of a sample by combining partial Leidenfrost effect with the super-hydrophobic array sensor sample pretreatment method is shown.
In example 4, the spectrum intensity results corresponding to the maximum signal characteristic spectrum peak (Be II 313.04 nm) of the element to Be detected in the 10 groups of solutes are shown in fig. 6, and the LIBS average signal intensity of the 10 groups of data is 16552 and the relative standard deviation is 3.7%, which indicates that the sample pretreatment stability is greatly improved due to the combination of partial leidenfrost effect and the sample treatment method of the superhydrophobic array sensor, and further the stability of LIBS detection is improved.
In example 5, the spectrum intensity results corresponding to the maximum signal characteristic spectrum peaks (Be II 313.04 nm) of the elements to Be detected with different concentrations are shown in FIG. 7, and the signal intensity of the Be element characteristic spectrum peak shows a remarkable decreasing trend along with the decrease of the element concentration in the Be solution, and the detection limit of the Be element calculated by the calibration curve established by the method provided by the invention is 0.033 mug/L.
In example 6, the spectrum intensity results corresponding to the maximum signal characteristic spectrum peaks (Cu I324.754 nm) of the elements to be detected with different concentrations are shown in FIG. 8, and the signal intensity of the Cu element characteristic spectrum peak shows a remarkable descending trend along with the descending of the element concentration in the Cu solution, and the detection limit of the Cu element calculated by the calibration curve established by the method provided by the invention is 0.083 mug/L.
It will be obvious to those skilled in the art that the present invention may be varied in a number of ways without departing from the scope of the invention. All such modifications as would be obvious to one skilled in the art are intended to be included within the scope of this claims.
Claims (4)
1. The quantitative detection method of trace elements in the water body is characterized by comprising the following steps:
(1) Preparing a super-hydrophobic array sensor by using a laser treatment and chemical modification method, wherein the super-hydrophobic array sensor is used for enriching and preprocessing a solution to be detected; the super-hydrophobic array sensor is required to have super-hydrophobic performance, and the super-hydrophobic surface is in an array form;
(2) Extracting a solution to be detected based on a part of Leidenfrost effect and the super-hydrophobic array sensor, and pipetting the solution to be detected to the surface of the super-hydrophobic array sensor for evaporation and enrichment to obtain an enrichment substrate containing solute deposition to be detected;
(3) Placing the enrichment substrate containing the solute sediment to be detected obtained in the step (2) in a LIBS detection system, and ablating the solute to be detected by using pulse laser to obtain a LIBS full spectrum of the solution to be detected;
(4) Processing the LIBS spectrum of the solution to be detected obtained in the step (3) to obtain the spectrum intensity corresponding to the maximum signal characteristic spectrum peak of the element to be detected in the full spectrum;
(5) Preparing a plurality of standard solutions containing solutes to be detected with different concentrations, and obtaining the spectral intensities containing the solutes to be detected with different concentrations according to the methods described in the steps (1) - (4);
(6) Establishing a calibration curve required during quantitative analysis, and calculating concentration values of elements to be detected in the solution to be detected; the calibration curve is established by fitting the spectral intensities of solutes to be detected and the corresponding element concentrations thereof in a plurality of standard solutions with known concentrations obtained in the step (5), and is used for constructing a linear relation between the concentration values of the elements to be detected and the spectral intensities corresponding to the maximum signal characteristic spectral peaks;
(7) Fitting the spectral intensity corresponding to the maximum signal characteristic spectral peak of the element to be measured in the solution to be measured extracted in the step (4) with a calibration curve to obtain an element concentration value corresponding to the spectral intensity in the calibration curve, namely the concentration value of the element to be measured in the solution to be measured.
2. The method for quantitatively detecting trace elements in a water body according to claim 1, wherein the preparation method of the superhydrophobic array sensor in the step (1) is as follows:
(1.1) placing a sensor substrate which is ultrasonically cleaned by using absolute ethyl alcohol and deionized water and dried in an infrared micro/nano processing system, and carrying out surface treatment by a picosecond laser to obtain a substrate with an array surface;
(1.2) the tridecaffein triethoxysilane solution was combined with absolute ethanol in a ratio of 1:99 to obtain the super-hydrophobic chemical modifier with the mass fraction of 1%wt;
(1.3) immersing the substrate with the array surface in the super-hydrophobic chemical modifier for 20 minutes, and then taking out to obtain a chemically modified substrate;
and (1.4) placing the chemically modified substrate on the surface of a heating platform at 80 ℃ for 10-20 minutes, and removing the residual chemical modifier on the surface of the substrate to obtain the super-hydrophobic array sensor.
3. The quantitative detection method of trace elements in a water body according to claim 1, wherein the specific method of evaporation enrichment in the step (2) is as follows: the super-hydrophobic array sensor is placed on the surface of a constant-temperature heating platform for heating and heat preservation, the solution to be detected is extracted through a micropipette and is pipetted to the super-hydrophobic array surface of the sensor for evaporation and enrichment, and along with gradual evaporation of the solvent in the solution to be detected, the solute to be detected is gradually separated out and forms small-area solute deposition in a short time, so that the evaporation and enrichment are completed.
4. The method for quantitatively detecting trace elements in a water body according to claim 3, wherein the heating and heat preserving temperature of the super-hydrophobic array sensor in the step (3) is 130-140 ℃; the volume of the solution to be detected is 50 mu L; the solute deposition time is 3-4 minutes; the solute deposition area has a diameter of 300 to 350 μm.
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