CN114965417A - Method for rapidly detecting methyl mercury by surface enhanced Raman scattering - Google Patents
Method for rapidly detecting methyl mercury by surface enhanced Raman scattering Download PDFInfo
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- JJWSNOOGIUMOEE-UHFFFAOYSA-N Monomethylmercury Chemical compound [Hg]C JJWSNOOGIUMOEE-UHFFFAOYSA-N 0.000 title claims abstract description 64
- 238000004416 surface enhanced Raman spectroscopy Methods 0.000 title claims abstract description 37
- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000001069 Raman spectroscopy Methods 0.000 claims abstract description 49
- 238000001514 detection method Methods 0.000 claims abstract description 46
- VYFYYTLLBUKUHU-UHFFFAOYSA-N dopamine Chemical compound NCCC1=CC=C(O)C(O)=C1 VYFYYTLLBUKUHU-UHFFFAOYSA-N 0.000 claims abstract description 44
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 26
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- PQTCMBYFWMFIGM-UHFFFAOYSA-N gold silver Chemical class [Ag].[Au] PQTCMBYFWMFIGM-UHFFFAOYSA-N 0.000 claims abstract description 10
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 10
- 239000001509 sodium citrate Substances 0.000 claims abstract description 9
- NLJMYIDDQXHKNR-UHFFFAOYSA-K sodium citrate Chemical compound O.O.[Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NLJMYIDDQXHKNR-UHFFFAOYSA-K 0.000 claims abstract description 9
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- 238000002156 mixing Methods 0.000 claims description 14
- -1 polytetrafluoroethylene Polymers 0.000 claims description 12
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 12
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- 229910021642 ultra pure water Inorganic materials 0.000 claims description 10
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- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 9
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- USFZMSVCRYTOJT-UHFFFAOYSA-N Ammonium acetate Chemical compound N.CC(O)=O USFZMSVCRYTOJT-UHFFFAOYSA-N 0.000 claims description 4
- 239000005695 Ammonium acetate Substances 0.000 claims description 4
- 229940043376 ammonium acetate Drugs 0.000 claims description 4
- 235000019257 ammonium acetate Nutrition 0.000 claims description 4
- XUJNEKJLAYXESH-UHFFFAOYSA-N cysteine Natural products SCC(N)C(O)=O XUJNEKJLAYXESH-UHFFFAOYSA-N 0.000 claims description 4
- 235000018417 cysteine Nutrition 0.000 claims description 4
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 claims description 4
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- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
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- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/65—Raman scattering
- G01N21/658—Raman scattering enhancement Raman, e.g. surface plasmons
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Abstract
The invention discloses a method for rapidly detecting methyl mercury by surface enhanced Raman scattering, which comprises the steps of preparing a dopamine carbon point modified gold-silver nano Raman scattering enhancer, preparing a super-hydrophobic film substrate, determining a methyl mercury SERS characteristic peak, purifying an aquatic product sample and measuring the methyl mercury SERS; according to the method, the dopamine carbon dots and the sodium citrate are used as reducing agents and stabilizing agents to prepare the gold-silver nano material as a Raman scattering reinforcing agent, the purified aquatic product extract is applied to the hydrophobic substrate for multiple times, methyl mercury molecules entering hot spot areas are enriched, the Raman signals of the molecules can be greatly enhanced, high-sensitivity detection of the methyl mercury is realized, the detection limit of an environmental water sample is up to 1 mug/kg, and the detection sensitivity of the methyl mercury SERS in the aquatic product is up to 5 mug/kg.
Description
Technical Field
The invention relates to the technical field of chemical analysis and detection, in particular to a method for rapidly detecting methyl mercury by surface enhanced Raman scattering.
Background
Mercury is one of the main pollutants widely existing in the whole sphere, methyl mercury is one of organic mercury, has the strongest toxicity and fat solubility, is easily absorbed and enriched by organisms in water, and the concentration of the methyl mercury in fish bodies can reach 10 in the water 4 ~10 6 And (4) doubling. Chronic poisoning may be caused by long-term consumption of food contaminated with mercury, and water preferably in japan is caused by long-term consumption of contaminated fish and shellfish. Therefore, the method is very necessary for measuring the methylmercury in the aquatic products. The related detection method of the state at present relates to a gas chromatography-inductively coupled plasma mass spectrometry (GC-ICP-MS) method, a high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) method, a high performance liquid chromatography-atomic fluorescence spectroscopy (HPLC-AFS) method and the like. These methods require expensive instrumentation, specialized operators, long testing times, and high costs.
Due to the advantages of high sensitivity, high resolution, capability of providing abundant structural information, no need of high vacuum detection conditions and the like, the Surface Enhanced Raman Scattering (SERS) spectrum can realize qualitative and quantitative detection and interface stress analysis, and is widely applied to the aspects of food monitoring, sample trace analysis and the like. The SERS detection method is simple, convenient, rapid and simple to operate, and particularly a portable Raman rapid detector has considerable advantages in food safety monitoring, but is quite limited in practical application at present, mainly the Raman signals generated by most target objects are weak, the effect of a Raman reinforcing agent is limited, and meanwhile, the detection sensitivity and accuracy are greatly influenced by the interference of a substrate. There is currently no report of direct use of SERS for methyl mercury detection.
Disclosure of Invention
The invention provides a method for rapidly detecting methyl mercury by surface enhanced Raman scattering, which combines a super-hydrophobic substrate with a gold-silver nano Raman scattering enhancer, and a nanoparticle suspension can be concentrated and gathered on one point on the super-hydrophobic surface, so that the method can be used for constructing an SERS substrate containing high-density hot spots; the method solves the problems that the existing surface enhanced Raman scattering spectrum Raman reinforcing agent is single in synthesis, a reducing agent and a stabilizing agent are limited, and the signal enhancement of a target object cannot be met, provides a new gold and silver nano material synthesis method, and achieves the effect of Raman signal enhancement.
The method for rapidly detecting the methyl mercury by the surface enhanced Raman scattering comprises the following steps:
preparing a gold and silver nano Raman scattering reinforcing agent with high stability by using dopamine carbon dots and sodium citrate as a reducing agent and a stabilizing agent;
coating a perfluorinated polyether modified epoxy resin with hydrophobicity on a polytetrafluoroethylene plate serving as a substrate, and drying to prepare a super-hydrophobic film substrate;
mixing the methyl mercury standard solution with a gold-silver nano Raman scattering enhancer in a vortex manner; using a liquid transfer gun to transfer the mixed solution drop on the super-hydrophobic film substrate, so that the mixed solution forms spherical liquid drops; naturally drying the spherical liquid drops, forming a detection area to be detected after the liquid drops are dried, carrying out Raman spectrum detection on the detection area to be detected by using a portable Raman instrument, and determining 924cm according to the methyl mercury molecular structure and the attribution of a Raman peak position -1 The characteristic peak is used as a discrimination basis for detecting the methyl mercury by the surface enhanced Raman scattering spectrum, and the linear relation between the concentration of the methyl mercury and the peak area of the characteristic peak is determined;
taking sample liquid to be detected and a gold-silver nano Raman scattering enhancer for vortex mixing; using a liquid transfer gun to transfer the mixed solution drop on the super-hydrophobic film substrate, so that the mixed solution forms spherical liquid drops; the method comprises the steps of naturally drying spherical liquid drops, repeating the processes of dripping and drying twice, forming a to-be-detected area after the liquid drops are dried, carrying out Raman spectrum detection on the to-be-detected area by using a portable Raman instrument, and calculating the concentration of methyl mercury in the to-be-detected sample liquid according to the peak area of a characteristic peak.
The sample to be detected comprises an environmental water sample and an aquatic product.
The preparation method of the gold and silver nano Raman scattering enhancer comprises the following steps:
1. synthesis of dopamine carbon dots: weighing 1.0-2.0g of dopamine and 0.5-1.0g of citric acid, dissolving in 20mL of ultrapure water, ultrasonically mixing uniformly, transferring the solution into a polytetrafluoroethylene lining hydrothermal reaction kettle, heating at the constant temperature of 200 ℃ for 8-10h, and naturally cooling to room temperature after the reaction is finished to obtain a brown solution; removing large-particle impurities from the brown solution by using a 0.22-micron filter membrane, centrifuging at a high speed, and drying the supernate in vacuum to obtain dopamine carbon dots;
2. preparation of gold and silver nano Raman scattering reinforcing agent: dissolving 12-15mg of dopamine carbon dot and 20-25mg of sodium citrate in 40mL of ultrapure water, heating to 100 ℃ in an oil bath, and adding AgNO 3 And HAuCl 4 ，AgNO 3 And HAuCl 4 The concentration of the gold and silver nano Raman scattering enhancer in the mixed solution is 10-15mg/mL, the mixture is stirred for 60min in a dark place, cooled to room temperature and centrifuged at high speed, and the supernatant is the gold and silver nano Raman scattering enhancer.
The preparation method of the super-hydrophobic film substrate comprises the following steps: after being extruded by stress, the perfluoropolyether modified epoxy resin is uniformly coated on a polytetrafluoroethylene plate, and the coating thickness is 0.5-1 mm; then, putting the polytetrafluoroethylene plate coated with the perfluoropolyether modified epoxy resin into a vacuum drying oven to be dried for 2-4h at 60 ℃ so as to remove the organic solvent; then taking out and cooling to room temperature.
The method for preparing the sample liquid to be detected by pretreating the aquatic product sample comprises the following steps:
(1) sample extraction: weighing 10g (accurate to 0.001 g) of sample, accurately transferring 50mL of 5mol/L hydrochloric acid solution, placing the sample in a 100mL plastic centrifuge tube with a cover, performing ultrasonic water bath extraction at room temperature for 60min, centrifuging at the rotating speed of 8000r/min at 4 ℃ for 15min, taking out supernatant, slowly dropwise adding an ammonia water solution (ammonia water and water are mixed according to the volume ratio of 1: 1) in a cold water bath, adjusting the pH of the supernatant to 3-7, and adding water to 50mL to obtain a sample extracting solution;
(2) sample extraction: oscillating and extracting a sample extracting solution twice by 20mL of dichloromethane, oscillating for 10min each time, standing for 10min, collecting and combining dichloromethane extracting solutions, putting the dichloromethane extracting solutions into a 50mL colorimetric tube, accurately adding 2mL of back-extraction solution (aqueous solution containing 1% of cysteine and 0.8% of ammonium acetate) by using a graduated pipette for extraction, oscillating for 5min, standing for 10min, and sucking an upper-layer aqueous solution to obtain a sample solution to be detected.
The concentration of the methyl mercury standard solution is 1-500 mug/L; the addition amount of the gold and silver nano Raman scattering enhancer is 50-100 mu L.
Under the conditions of 785nm exciting light, 500mW laser power and 10s scanning time of Raman spectrum detection, the surface enhanced Raman scattering spectrum peak of the methylmercury standard solution has 488cm -1 、581cm -1 And 924cm -1 Peak(s).
The detection concentration of the method of the invention on the water sample reaches 1 mug/L.
The detection limit of the method for the methyl mercury residue in the aquatic product is 5 mug/kg.
The invention has the following advantages:
1. the invention adopts dopamine carbon dots, sodium citrate as a reducing agent and a stabilizer to prepare a gold-silver nano material as a Raman scattering enhancer, and the Raman scattering enhancer has high stability, high selectivity and capability of enhancing SERS (surface enhanced Raman scattering) signals of methyl mercury and coexisting Hg 2+ And other substances that may be present in the aquatic product do not interfere with the assay;
2. according to the method, the purified aquatic product extract is sample-applied on the hydrophobic substrate prepared by the method for multiple times, so that methyl mercury molecules entering a hot spot area are enriched, the Raman signal of the molecules can be greatly enhanced, the high-sensitivity detection of the methyl mercury is realized, the detection limit of a water sample reaches 1 microgram/L, and the detection sensitivity of the methyl mercury SERS in the aquatic product reaches 5 microgram/kg;
3. in the method, the sample extracting solution is extracted by using an organic solvent at first, and then is subjected to back extraction by using a water phase, so that the methyl mercury is enriched, and the interference of fat-soluble components in the extracting solution is eliminated;
4. the gold and silver nano material prepared in the method can form Au-Ag-Hg alloy with methyl mercury, so that aggregation-induced plasmon displacement is caused, amplification of Raman signals of the gold and silver nano material is realized, and the detection method has the characteristics of high sensitivity, strong specificity, simplicity in operation, quickness and the like.
Drawings
FIG. 1 is a SERS spectrum of different concentrations of methylmercury drops on a super-hydrophobic thin film substrate according to example 1 of the present invention;
FIG. 2 is a linear relationship between different concentrations of methylmercury and the intensity of characteristic peaks in example 1 of the present invention;
fig. 3 is a SERS spectrum of the purified water product extracted by adding methyl mercury drops with different concentrations on a super-hydrophobic film substrate in example 1 of the present invention.
Detailed Description
The present invention is described in terms of particular embodiments, other advantages and features of the invention will become apparent to those skilled in the art from the following disclosure, and it is to be understood that the described embodiments are merely exemplary of the invention and that it is not intended to limit the invention to the particular embodiments disclosed. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1: surface enhanced Raman scattering rapid detection of methylmercury in aquatic products
(1) Weighing 1.0g of dopamine and 0.5g of citric acid, dissolving in 20mL of ultrapure water, ultrasonically mixing uniformly, transferring the solution into a polytetrafluoroethylene-lined hydrothermal reaction kettle, heating at the constant temperature of 180 ℃ for 10 hours, and naturally cooling to room temperature after the reaction is finished to obtain a brown solution; removing large particle impurities from the brown solution with a 0.22 μm filter membrane, centrifuging at 8000r/min, and vacuum drying the supernatant at 60 deg.C to obtain dopamine carbon dots;
(2) dissolving 12mg of dopamine carbon dot and 20mg of sodium citrate in 40mL of ultrapure water, heating to 100 ℃ in an oil bath, and adding AgNO 3 And HAuCl 4 ，AgNO 3 And HAuCl 4 The concentration of the silver nano Raman scattering enhancer in the mixed solution is 10mg/mL, the mixture is stirred for 60min in a dark place, cooled to room temperature and centrifuged at 8000r/min, and the supernatant is the silver nano Raman scattering enhancer;
(3) after being extruded by stress, the perfluoropolyether modified epoxy resin is uniformly coated on a polytetrafluoroethylene plate, and the coating thickness is 1 mm; then, putting the polytetrafluoroethylene plate coated with the perfluoropolyether modified epoxy resin into a vacuum drying oven, drying for 2 hours at 60 ℃ to remove the organic solvent, taking out, and cooling to room temperature to obtain the super-hydrophobic film substrate;
(4) SERS detection of methyl mercury standard solution: taking 200 mu L of methyl mercury standard solution (1, 5, 50, 100, 200, 300, 400 and 500 mu g/L) and 100 mu L of gold-silver nano Raman scattering reinforcing agent, carrying out vortex mixing for 1min, using a liquid transfer gun to transfer 50 mu L of the mixed solution, dripping the mixed solution on a super-hydrophobic film substrate to enable the mixed solution to form spherical liquid drops, naturally airing the spherical liquid drops, forming a detection area to be detected after the liquid drops are dried, scanning for 10s under the conditions of 785nm exciting light and 500mW laser power, and carrying out Raman spectrum detection on the detection area to be detected by using a portable Raman spectrometer;
(5) determining the detection wave number of the methyl mercury SERS spectrum and performing SERS analysis on the standard: as shown in FIG. 1, 488cm is observed in SERS spectrum of methylmercury -1 、581cm -1 And 924cm -1 Determining 924cm according to the molecular structure and Raman peak position assignment of methyl mercury -1 The characteristic peak is used as the discrimination basis for detecting the methyl mercury by SERS spectrum. The intensities of the characteristic peaks in the SERS spectra of the methyl mercury vary with the concentrations of the standard solutions (1, 5, 50, 100, 200, 300, 400 and 500. mu.g/L), as shown in FIG. 2, the concentration of the methyl mercury and the peak area of the characteristic peaks are 924cm -1 The linear regression equation is: y = 1988.74x +4588.17, R 2 = 0.9688; and all have obvious Raman spectrum peaks when the concentration is as low as 1 mug/L; therefore, the detection concentration of the methyl mercury standard solution by the method reaches 1 mug/L;
(6) SERS determination of methyl mercury in grass carp sample
(61) Extracting a grass carp sample: weighing 10g (accurate to 0.001 g) of grass carp and 50mL of 5mol/L hydrochloric acid solution, placing the grass carp and 50mL of 5mol/L hydrochloric acid solution into a 100mL plastic centrifuge tube with a cover, extracting the grass carp and the hydrochloric acid solution in an ultrasonic water bath at room temperature for 60min, centrifuging the grass carp and the hydrochloric acid solution at a rotating speed of 8000r/min at 4 ℃ for 15min, taking out a supernatant, slowly dropwise adding an ammonia water solution (the ammonia water and the water are mixed according to a volume ratio of 1: 1) into a cold water bath, adjusting the pH value of the supernatant to be 6, and adding water to 50mL to obtain a sample extracting solution;
(62) sample extraction: oscillating and extracting a sample extracting solution twice by using 20mL of dichloromethane, oscillating for 10min each time, standing for 10min, collecting and combining dichloromethane extracting solutions, putting the dichloromethane extracting solutions into a 50mL colorimetric tube, accurately adding 2mL of back extraction solution (aqueous solution containing 1% of cysteine and 0.8% of ammonium acetate) by using a graduated pipette for extraction, oscillating for 5min, standing for 10min, and sucking an upper aqueous solution to obtain a sample solution to be detected;
(63) mixing 200 mu L of sample liquid to be detected and 100 mu L of gold and silver nano Raman scattering reinforcing agent for 1min in a vortex manner; using a liquid transfer gun to transfer 50 mu L of the mixed solution to drop on the super-hydrophobic film substrate, so that the mixed solution forms spherical liquid drops; naturally airing the spherical liquid drops, repeating the processes of dripping and airing twice, drying the concentrated liquid drops to form a to-be-detected area, performing Raman spectrum detection on the to-be-detected area by using a portable Raman spectrometer, scanning for 10s under the conditions of 785nm exciting light and 500mW laser power, substituting the peak area of the obtained characteristic peak into the regression equation in the step (5), and calculating to obtain the concentration of the methyl mercury in the grass carp to be 6 mug/kg;
the accuracy and the reproducibility of the method are verified through the sample standard adding recovery rate and the precision test, and the method comprises the following specific steps: carrying out blank surface enhanced Raman scattering detection on the treated sample liquid to be detected, and finding that the sample liquid to be detected is at 924cm -1 A characteristic peak appears, the characteristic peak for detecting the methyl mercury is not interfered, but the matrix interference reduces the identification of the SRES spectrum of the methyl mercury; performing SERS detection by adding standard recovery rate test, i.e. adding methyl mercury standard solutions with different concentrations into blank sample solution to be detected, wherein 924cm is used when the concentration of methyl mercury is 5 μ g/kg -1 The characteristic peak of the SRES can still be obviously identified, and when the concentration is as low as 1 mu g/kg, the obtained SRES spectrum is similar to that of the blank extracting solution; the results of figure 3 show that the detection limit of the detection method on the methyl mercury in the fish is lower than 5 mug/kg, the experimental reproduction is good, and the detection rate is high>90%。
Example 2: surface enhanced Raman scattering rapid detection of methyl mercury in squid
(1) Weighing 2.0g of dopamine and 1.0g of citric acid, dissolving in 20mL of ultrapure water, ultrasonically mixing uniformly, transferring the solution into a polytetrafluoroethylene-lined hydrothermal reaction kettle, heating at the constant temperature of 200 ℃ for 8 hours, and naturally cooling to room temperature after the reaction is finished to obtain a brown solution; removing large particle impurities from the brown solution with a 0.22 μm filter membrane, centrifuging at 8000r/min, and vacuum drying the supernatant at 60 deg.C to obtain dopamine carbon dots;
(2) dissolving 15mg of dopamine carbon dot and 25mg of sodium citrate in 40mL of ultrapure water, heating to 100 ℃ in an oil bath, and adding AgNO 3 And HAuCl 4 ，AgNO 3 And HAuCl 4 The concentration of the silver nano Raman scattering enhancer in the mixed solution is 14mg/mL, the mixture is stirred for 60min in a dark place, cooled to room temperature and centrifuged at 8000r/min, and the supernatant is the silver nano Raman scattering enhancer;
(3) after being extruded by stress, the perfluoropolyether modified epoxy resin is uniformly coated on a polytetrafluoroethylene plate, and the coating thickness is 0.8 mm; then, putting the polytetrafluoroethylene plate coated with the perfluoropolyether modified epoxy resin into a vacuum drying oven, drying for 3 hours at 60 ℃ to remove the organic solvent, taking out, and cooling to room temperature to obtain the super-hydrophobic film substrate;
(4) the SERS detection and regression equation of the methylmercury standard solution are the same as those of the example 1;
(5) SERS determination of methyl mercury in squid sample
(51) Extracting a squid sample: weighing 10g (accurate to 0.001 g) of squid and 50mL of 5mol/L hydrochloric acid solution, placing the squid and the 5mol/L hydrochloric acid solution into a 100mL plastic centrifuge tube with a cover, extracting the squid and the 5mol/L hydrochloric acid solution in an ultrasonic water bath at room temperature for 60min, centrifuging the squid and the 50mL hydrochloric acid solution at a rotating speed of 8000r/min at 4 ℃ for 15min, taking out supernatant, slowly dropwise adding an ammonia water solution (the ammonia water and water are mixed according to a volume ratio of 1: 1) into a cold water bath, adjusting the pH value of the supernatant to be 4, and adding water to 50mL to obtain a sample extracting solution;
(52) sample extraction: oscillating and extracting a sample extracting solution twice by using 20mL of dichloromethane, oscillating for 10min each time, standing for 10min, collecting and combining dichloromethane extracting solutions, putting the dichloromethane extracting solutions into a 50mL colorimetric tube, accurately adding 2mL of back extraction solution (aqueous solution containing 1% of cysteine and 0.8% of ammonium acetate) by using a graduated pipette for extraction, oscillating for 5min, standing for 10min, and sucking an upper aqueous solution to obtain a sample solution to be detected;
(53) mixing 200 mu L of sample liquid to be detected and 100 mu L of gold and silver nano Raman scattering reinforcing agent for 1min in a vortex manner; using a liquid transfer gun to transfer 50 mu L of the mixed solution to drop on the super-hydrophobic film substrate, so that the mixed solution forms spherical liquid drops; naturally airing the spherical liquid drops, repeating the processes of dripping and airing twice, drying the concentrated liquid drops to form a to-be-detected area, performing Raman spectrum detection on the to-be-detected area by using a portable Raman spectrometer, scanning for 10s under the conditions of 785nm exciting light and 500mW laser power, substituting the peak area of the obtained characteristic peak into the regression equation in the step (4), and calculating to obtain the concentration of the methyl mercury in the squid to be 3.5 mu g/kg;
the method for quickly detecting methyl mercury in aquatic products by surface-enhanced Raman scattering uses an extraction-back extraction method to remove interference influence of impurities such as fat, protein and the like in aquatic products, uses the dopamine carbon-point modified gold-silver nano as an SERS reinforcing agent and the prepared super-hydrophobic thin film substrate as an SERS substrate, and has the characteristics of high sensitivity, rapidness, simplicity and convenience in operation and the like for SERS detection of methyl mercury in aquatic products.
Example 3: surface enhanced Raman scattering rapid detection of methyl mercury in drinking water
(1) Weighing 1.5g of dopamine and 0.8g of citric acid, dissolving in 20mL of ultrapure water, ultrasonically mixing uniformly, transferring the solution into a polytetrafluoroethylene-lined hydrothermal reaction kettle, heating at the constant temperature of 190 ℃ for 9 hours, and naturally cooling to room temperature after the reaction is finished to obtain a brown solution; removing large particle impurities from the brown solution with a 0.22 μm filter membrane, centrifuging at 8000r/min, and vacuum drying the supernatant at 60 deg.C to obtain dopamine carbon dots;
(2) dissolving 13mg of dopamine carbon dot and 22mg of sodium citrate in 40mL of ultrapure water, heating to 100 ℃ in an oil bath, and adding AgNO 3 And HAuCl 4 ，AgNO 3 And HAuCl 4 The concentration of the silver nano Raman scattering enhancer in the mixed solution is 12mg/mL, the mixture is stirred for 60min in a dark place, cooled to room temperature and centrifuged at 8000r/min, and the supernatant is the silver nano Raman scattering enhancer;
(3) after being extruded by stress, the perfluoropolyether modified epoxy resin is uniformly coated on a polytetrafluoroethylene plate, and the coating thickness is 0.7 mm; then, putting the polytetrafluoroethylene plate coated with the perfluoropolyether modified epoxy resin into a vacuum drying oven, drying for 3 hours at 60 ℃ to remove the organic solvent, taking out, and cooling to room temperature to obtain the super-hydrophobic film substrate;
(4) the SERS detection and regression equation of the methylmercury standard solution are the same as those of the example 1;
(5) pretreatment of drinking water samples: adding 0.20mL of concentrated nitric acid into 10.0mL of water sample, and standing for 20min to obtain a sample solution to be detected;
(6) mixing 200 mu L of sample liquid to be detected and 100 mu L of gold and silver nano Raman scattering reinforcing agent for 1min in a vortex manner; using a liquid transfer gun to transfer 50 mu L of the mixed solution to drop on the super-hydrophobic film substrate, so that the mixed solution forms spherical liquid drops; naturally drying the spherical liquid drops, repeating the processes of dripping and drying twice, drying the concentrated liquid drops to form a to-be-detected area, performing Raman spectrum detection on the to-be-detected area by using a portable Raman spectrometer, scanning for 10s under the conditions of 785nm exciting light and 500mW laser power, and substituting the peak area of the obtained characteristic peak into the regression equation in the step (4), wherein no methyl mercury is detected.
Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (5)
1. A method for rapidly detecting methylmercury by surface enhanced Raman scattering is characterized by comprising the following steps:
preparing a gold and silver nano Raman scattering enhancer by using dopamine carbon dots and sodium citrate as a reducing agent and a stabilizing agent;
taking a polytetrafluoroethylene plate as a substrate, coating perfluoropolyether modified epoxy resin with hydrophobicity on the substrate, and drying to prepare a super-hydrophobic film substrate;
mixing the methyl mercury standard solution with a gold-silver nano Raman scattering enhancer in a vortex manner; using a liquid transfer gun to transfer the mixed solution drop on the super-hydrophobic film substrate, so that the mixed solution forms spherical liquid drops; naturally drying the spherical liquid drops, forming a detection area to be detected after the liquid drops are dried, carrying out Raman spectrum detection on the detection area to be detected by using a portable Raman instrument, and determining 924cm according to the methyl mercury molecular structure and the attribution of a Raman peak position -1 Characteristic peak of the first detection region is used as surface enhanced Raman scattering spectrum to detect the firstDetermining the judgment basis of the basic mercury, and determining the linear relation between the concentration of the methyl mercury and the peak area of the characteristic peak;
taking a sample liquid to be detected and mixing with a gold-silver nano Raman scattering enhancer in a vortex manner; using a liquid transfer gun to transfer the mixed solution drop on the super-hydrophobic film substrate, so that the mixed solution forms spherical liquid drops; naturally drying the spherical liquid drops, repeating the processes of dripping and drying twice, forming a to-be-detected area after the liquid drops are dried, carrying out Raman spectrum detection on the to-be-detected area by using a portable Raman instrument, and calculating the concentration of the methyl mercury in the to-be-detected sample liquid according to the peak area of the characteristic peak.
2. The method of claim 1, wherein the gold and silver nano raman scattering enhancer is prepared as follows:
(1) weighing 1.0-2.0g of dopamine and 0.5-1.0g of citric acid, dissolving in 20mL of ultrapure water, ultrasonically mixing uniformly, transferring the solution into a polytetrafluoroethylene lining hydrothermal reaction kettle, heating at the constant temperature of 200 ℃ for 8-10h, and naturally cooling to room temperature after the reaction is finished to obtain a brown solution; removing large particle impurities from the brown solution by using a 0.22-micron filter membrane, centrifuging at a high speed, and drying the supernatant in vacuum to obtain dopamine carbon dots;
(2) dissolving 12-15mg of dopamine carbon dot and 20-25mg of sodium citrate in 40mL of ultrapure water, heating to 100 ℃ in an oil bath, and adding AgNO 3 And HAuCl 4 ，AgNO 3 And HAuCl 4 The concentration of the gold and silver nano Raman scattering enhancer in the mixed solution is 10-15mg/mL, the mixture is stirred for 60min in a dark place, cooled to room temperature and centrifuged at high speed, and the supernatant is the gold and silver nano Raman scattering enhancer.
3. The method according to claim 1, wherein the sample liquid to be tested of the aquatic product is prepared by the steps of:
(1) weighing 10.000g of aquatic product sample and 50mL of 5mol/L hydrochloric acid solution, placing the aquatic product sample and 50mL of 5mol/L hydrochloric acid solution into a 100mL plastic centrifuge tube with a cover, extracting the aquatic product sample in an ultrasonic water bath at room temperature for 60min, centrifuging the aquatic product sample at the rotation speed of 8000r/min at the temperature of 4 ℃ for 15min, taking out supernatant, slowly dropwise adding an ammonia water solution into a cold water bath, adjusting the pH value of the supernatant to 3-7, and adding water to 50mL to obtain a sample extracting solution;
(2) oscillating and extracting a sample extracting solution twice by using 20mL of dichloromethane, oscillating for 10min each time, standing for 10min, collecting and combining dichloromethane extracting solutions into a 50mL colorimetric tube, accurately adding 2mL of back-extraction solution by using a graduated pipette for extraction, oscillating for 5min, standing for 10min, and sucking an upper-layer aqueous solution to obtain a sample solution to be detected, wherein the back-extraction solution is an aqueous solution containing cysteine with the mass concentration of 1% and ammonium acetate with the mass concentration of 0.8%.
4. The method of claim 1, wherein: the concentration of the methylmercury standard solution is 1-500 mug/L, and the addition amount of the gold and silver nano Raman scattering reinforcing agent is 50-100 mug L.
5. The method of claim 1, wherein: the ammonia water solution is prepared by mixing ammonia water and water according to the volume ratio of 1: 1.
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| CN117664953B (en) * | 2024-01-31 | 2024-05-17 | 云南伦扬科技有限公司 | Method for rapidly detecting fumonisin B1 and mercury by using Au-Ag Janus@Au NPs with SERS and nano enzyme activities |
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