CN114113037A - Method for rapidly detecting dithiocarbamate pesticides in tobacco leaves - Google Patents
Method for rapidly detecting dithiocarbamate pesticides in tobacco leaves Download PDFInfo
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- CN114113037A CN114113037A CN202111430205.XA CN202111430205A CN114113037A CN 114113037 A CN114113037 A CN 114113037A CN 202111430205 A CN202111430205 A CN 202111430205A CN 114113037 A CN114113037 A CN 114113037A
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- 239000000575 pesticide Substances 0.000 title claims abstract description 82
- 239000012990 dithiocarbamate Substances 0.000 title claims abstract description 69
- 241000208125 Nicotiana Species 0.000 title claims abstract description 67
- 235000002637 Nicotiana tabacum Nutrition 0.000 title claims abstract description 67
- DKVNPHBNOWQYFE-UHFFFAOYSA-N carbamodithioic acid Chemical compound NC(S)=S DKVNPHBNOWQYFE-UHFFFAOYSA-N 0.000 title claims abstract description 61
- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000001069 Raman spectroscopy Methods 0.000 claims abstract description 118
- 239000000758 substrate Substances 0.000 claims abstract description 92
- 239000002131 composite material Substances 0.000 claims abstract description 62
- 239000000126 substance Substances 0.000 claims abstract description 59
- 239000007788 liquid Substances 0.000 claims abstract description 50
- 239000012086 standard solution Substances 0.000 claims abstract description 49
- 238000012937 correction Methods 0.000 claims abstract description 45
- 238000001514 detection method Methods 0.000 claims abstract description 34
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- 238000002198 surface plasmon resonance spectroscopy Methods 0.000 claims description 5
- 239000012224 working solution Substances 0.000 claims description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 4
- FOIXSVOLVBLSDH-UHFFFAOYSA-N Silver ion Chemical compound [Ag+] FOIXSVOLVBLSDH-UHFFFAOYSA-N 0.000 claims description 4
- 229910052802 copper Inorganic materials 0.000 claims description 4
- 239000010949 copper Substances 0.000 claims description 4
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 4
- 239000010931 gold Substances 0.000 claims description 4
- 229910052737 gold Inorganic materials 0.000 claims description 4
- 238000001228 spectrum Methods 0.000 claims 1
- 150000004659 dithiocarbamates Chemical class 0.000 abstract description 8
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- 238000012360 testing method Methods 0.000 description 8
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- WCXDHFDTOYPNIE-RIYZIHGNSA-N (E)-acetamiprid Chemical compound N#C/N=C(\C)N(C)CC1=CC=C(Cl)N=C1 WCXDHFDTOYPNIE-RIYZIHGNSA-N 0.000 description 2
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- 239000005760 Difenoconazole Substances 0.000 description 2
- PNVJTZOFSHSLTO-UHFFFAOYSA-N Fenthion Chemical compound COP(=S)(OC)OC1=CC=C(SC)C(C)=C1 PNVJTZOFSHSLTO-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- BQYJATMQXGBDHF-UHFFFAOYSA-N difenoconazole Chemical compound O1C(C)COC1(C=1C(=CC(OC=2C=CC(Cl)=CC=2)=CC=1)Cl)CN1N=CN=C1 BQYJATMQXGBDHF-UHFFFAOYSA-N 0.000 description 2
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- 238000005516 engineering process Methods 0.000 description 2
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- 229910000021 magnesium carbonate Inorganic materials 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
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- 239000003899 bactericide agent Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- TXSULMYZLWFIAT-UHFFFAOYSA-N carbamodithioic acid;ethene Chemical class C=C.NC(S)=S TXSULMYZLWFIAT-UHFFFAOYSA-N 0.000 description 1
- TYUWIWBZXGOFHY-UHFFFAOYSA-N carbamodithioic acid;prop-1-ene Chemical class CC=C.NC(S)=S TYUWIWBZXGOFHY-UHFFFAOYSA-N 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- MZGNSEAPZQGJRB-UHFFFAOYSA-N dimethyldithiocarbamic acid Chemical class CN(C)C(S)=S MZGNSEAPZQGJRB-UHFFFAOYSA-N 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 235000012055 fruits and vegetables Nutrition 0.000 description 1
- 239000000417 fungicide Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 238000004811 liquid chromatography Methods 0.000 description 1
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- 239000002184 metal Substances 0.000 description 1
- 229910021392 nanocarbon Inorganic materials 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
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- 239000002243 precursor Substances 0.000 description 1
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- 238000001179 sorption measurement Methods 0.000 description 1
- 238000002798 spectrophotometry method Methods 0.000 description 1
- 238000013112 stability test Methods 0.000 description 1
- 238000004416 surface enhanced Raman spectroscopy Methods 0.000 description 1
- 235000019505 tobacco product Nutrition 0.000 description 1
- HRXKRNGNAMMEHJ-UHFFFAOYSA-K trisodium citrate Chemical compound [Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O HRXKRNGNAMMEHJ-UHFFFAOYSA-K 0.000 description 1
- 229940038773 trisodium citrate Drugs 0.000 description 1
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Images
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- 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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- Health & Medical Sciences (AREA)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Physics & Mathematics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
Abstract
The invention discloses a method for rapidly detecting dithiocarbamate pesticides in tobacco leaves, which comprises the following steps: constructing a composite Raman enhancement substrate; pretreating a tobacco leaf sample to obtain a liquid to be detected; mixing the composite Raman-enhanced substrate in the step S1 with the solution to be detected in the step S2 to obtain a mixture; detecting the mixture in the step S3 by using a portable Raman spectrometer to obtain a Raman spectrogram of the object to be detected and the quantitative correction substance; drawing a working curve of the dithiocarbamate standard solution; and comparing the Raman spectrogram of the substance to be detected and the quantitative correction substance in the S4 with the working curve of the standard solution in the S5 to obtain the content of the dithiocarbamate pesticides in the tobacco leaves. The invention does not need to perform derivatization on dithiocarbamates, has simple and convenient operation, low sensitivity and good quantitative accuracy, has the characteristic of on-site detection, and can perform rapid qualitative and quantitative detection.
Description
Technical Field
The invention relates to the technical field of detection of pesticide residues in tobacco leaves, and particularly relates to a rapid detection method of dithiocarbamate pesticides in tobacco leaves.
Background
Dithiocarbamates (DTCs) are a class of organosulfur protective fungicides, mainly the three classes of dimethyldithiocarbamates (such as thiram), propylene dithiocarbamates (such as propineb), and ethylene dithiocarbamates (such as mancozeb). In tobacco, DTCs are mainly used for preventing and controlling anthrax, vertical blight, root rot, brown spot or black shank, and the like, and are easy to cause residues due to the fact that DTCs are relatively stable on the surface of tobacco leaves, and are one of pesticides with high pesticide residue detection rate in tobacco and tobacco products.
The methods commonly used for DTCs detection at present include liquid chromatography, gas chromatography and chromatography-mass spectrometry. Compared with the early spectrophotometry, the methods have greatly improved sensitivity, but the detection requires derivatization of a sample, the pretreatment operation is complex and long, and only the total amount of DTCs (DTCs) which are the residual bactericides can be obtained. Therefore, it is important to establish a simple method suitable for rapid analysis without derivatization.
With the development of the Surface Enhanced Raman Spectroscopy (SERS) technology, the SERS technology is used for rapid on-site analysis due to its features of simple operation, high sensitivity, no need of complex pre-treatment of samples, and the like, and is widely used in the field of detection of pesticide residues on fruits and vegetables in recent years. However, due to factors such as uneven distribution of molecules to be detected on the metal substrate, the reproducibility of molecular signals is poor, and the application of quantitative detection of the molecules is limited. The detection performance and reliability of SERS depend on the reasonable design of the substrate, and carbon materials are used for preparing the SERS substrate in recent years due to the excellent adsorption performance and chemical stability of the carbon materials, but the general preparation method is complex and the quantitative effect cannot meet the actual requirement.
In view of the above, there is a need to develop a method for detecting dithiocarbamate pesticides in tobacco leaves to solve the above technical problems.
Disclosure of Invention
The invention aims to provide a method for detecting dithiocarbamate pesticides in tobacco leaves, which has excellent sensitivity and quantitative accuracy and can rapidly and quantitatively detect the dithiocarbamate pesticides in the tobacco leaves.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a method for rapidly detecting dithiocarbamate pesticides in tobacco leaves, which comprises the following steps:
s1, constructing a composite Raman enhancement substrate; the composite Raman enhancement substrate is constructed by a carbon carrier, a load and a quantitative correction substance; uniformly dispersing the load on the surface of a carrier to form a composite substrate, adding the quantitative correction substance into the composite substrate, and uniformly mixing to obtain a composite Raman enhancement substrate;
s2, preprocessing a tobacco leaf sample to obtain a liquid to be detected;
s3, mixing the composite Raman enhancement substrate in the step S1, the liquid to be detected in the step S2 and a quantitative correction substance to obtain a mixture;
s4, detecting the mixture in the step S3 by adopting a portable Raman spectrometer to obtain a Raman spectrogram of the object to be detected and the quantitative correction substance;
s5, preparing a dithiocarbamate standard solution, adding the composite Raman enhancement substrate and quantitative correction substances in the same amount as those in the S3 into the standard solution, detecting by using the Raman spectrometer same as that in the S4, and drawing a working curve of the dithiocarbamate standard solution;
and S6, comparing the Raman spectrogram of the substance to be detected and the quantitative correction substance in the S4 with the working curve of the standard solution in the S5, and calculating to obtain the content of the dithiocarbamate pesticides in the tobacco leaves.
The raman enhancement substrate in step S1 is specifically constructed by: the carbon nano-cage CNCs material rich in oxygen-containing functional groups is used as the carrier after surface modification treatment, the metal nano-particle sol with surface plasmon resonance effect is used as the load, and a chemical substance with a Raman signal appearing in a Raman silent area is used as the quantitative correction substance to construct the CNCs @ metal nano-particle composite Raman enhanced substrate.
Preferably, the carbon nanocage material is a material which is synthesized by using magnesium oxide as a template and adopting a CVD method and has a regular mesoporous structure and uniform pore diameter; the aperture is 10-50 nm, and the surface of the material is rich in hydroxyl, carbonyl and carboxyl active functional groups after surface modification; the metal nanoparticle sol is one of gold nanoparticles, silver nanoparticles or copper nanoparticles.
Preferably, the CNCs @ metal nanoparticle composite Raman enhancement substrate is a liquid substrate or a solid substrate; when the composite Raman enhancement substrate is a liquid substrate, the volume ratio of the liquid composite Raman enhancement substrate to the liquid to be detected is 1-5: 1; when the composite Raman enhancement substrate is a solid substrate, the addition of the liquid drop to be detected is 10-50 uL.
Preferably, the quantitative correction substance is KSCN of 9-11 mg/L.
Preferably, the tobacco sample pretreatment method in step S2 is as follows:
placing 0.5g of cut tobacco leaf sample in a centrifuge tube, adding 5ml of ethyl acetate, performing vortex oscillation on a vortex mixing oscillator for 1min, and performing centrifugal separation at a rotation speed of not more than 4000r/min for 1min to obtain supernatant, i.e. sample extract; adding 100mg of polyamide, 100mg of N-propyl ethylenediamine solid phase adsorbent PSA, 30mg of graphite carbonized black GCB and 50mg of C18 into a purification tube in sequence, acidifying with 100 mu L of 1mol/L HCl, adding 1mL of the sample extracting solution, oscillating for 1min in a vortex mixing oscillator, centrifuging for 1min at 10000r/min, taking supernatant, placing the supernatant into a 2mL centrifuge tube, adding 100uL of 9-11 mg/L KSCN solution, blowing to be nearly dry, adding 100 mu L of pure water, and redissolving to obtain the liquid to be detected.
Preferably, in the step S4, the wavelength of the excitation light source of the portable raman spectrometer is 300 to 1500nm, and the spectral range is 150 to 2800cm-1。
Preferably, the dithiocarbamate pesticides in the tobacco leaves detected by the detection method are thiram, propineb and mancozeb.
Preferably, the working curve for plotting the dithiocarbamate standard solution in the step S5 is specifically as follows:
acetonitrile is taken as a solvent, and standard solutions of thiram, propineb and mancozeb with the concentrations of 0.05, 0.2, 1, 2, 4, 6 and 8mg/kg are respectively prepared; and performing Raman detection on the three pesticide standard solutions with different concentrations after the operation according to the methods in the steps S3 and S4, wherein the ratio of the Raman quantitative characteristic peak intensity of the pesticide to be detected to the internal standard peak intensity is used as a vertical coordinate, and the pesticide concentration is used as a horizontal coordinate to obtain quantitative standard curves of the three pesticides.
Preferably, the calculation formula of the content of the dithiocarbamate pesticides in the tobacco leaves in the step S6 is as follows:
wherein:
r is pesticide residue amount in mg/kg on a wet basis;
c, the pesticide concentration in the liquid to be detected of the sample is given by a standard curve, and the unit is ug/mL;
v is volume of extract liquid, unit is mL;
m is the sample mass in g;
cis-the concentration of the internal standard in the sample extract is ug/mL;
ci2-the concentration of the internal standard in the standard working solution is ug/mL.
In summary, compared with the prior art, the invention has the beneficial effects that:
1. according to the invention, the carbon nanocage material with a regular and uniform mesoporous structure is used as the material for loading the metal nanoparticles, so that a more uniform Raman signal can be obtained by the composite enhanced substrate, and the detection sensitivity and the stability of an enhanced system are obviously improved; meanwhile, the surface of the carbon nanocages is modified, so that the surface of the material has rich oxygen-containing functional groups, the dispersibility of the enhanced substrate in different solvents is improved, and the consistency of Raman signals is improved.
2. The method does not need to perform derivatization on the dithiocarbamate, is simple and convenient to operate, has the characteristic of field detection, is low in sensitivity and good in quantitative accuracy, and can be used for quickly, qualitatively and quantitatively detecting the dithiocarbamate pesticide in the tobacco leaves.
3. According to the invention, the quantitative correction reagent is added into the enhanced substrate, so that the quantitative Raman signal can be less interfered by the change of equipment, environment and a reaction system, and the quantitative accuracy is improved.
4. The enhanced substrate has better universality, is not only suitable for detecting dithiocarbamate pesticides, but also can effectively detect other various pesticides under the portable Raman spectrum equipment.
5. The preparation method of the enhanced substrate is simple, has good stability, long effective service life and high detection sensitivity, can accurately perform quantitative detection on pesticide, has simple and rapid detection steps, and is suitable for rapid field detection of tobacco pesticide residues.
6. The pretreatment method of the tobacco sample provided by the invention greatly reduces the interference degree existing when the solvent is combined with the enhancing reagent.
Drawings
FIG. 1 is a Raman spectrum test chart and corresponding Raman characteristic peaks of three pesticide standard solutions of the invention;
FIG. 2 is a graph of Raman characteristic peak intensity of 0.5mg/L thiram standard solution of the present invention as a function of time;
FIG. 3 shows Raman spectrum test charts of fenthion, acetamiprid and difenoconazole and corresponding Raman characteristic peaks.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without any inventive step, are within the scope of the present invention.
Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention provides a method for rapidly detecting dithiocarbamate pesticides in tobacco leaves, which comprises the following steps:
s1, constructing a composite Raman enhancement substrate; the composite Raman enhancement substrate is constructed by a carbon carrier, a load and a quantitative correction substance; uniformly dispersing the load on the surface of a carrier to form a composite substrate, adding the quantitative correction substance into the composite substrate, and uniformly mixing to obtain a composite Raman enhancement substrate;
s2, preprocessing a tobacco leaf sample to obtain a liquid to be detected;
s3, mixing the composite Raman enhancement substrate in the step S1, the liquid to be detected in the step S2 and a quantitative correction substance to obtain a mixture;
s4, detecting the mixture in the step S3 by adopting a portable Raman spectrometer to obtain a Raman spectrogram of the object to be detected and the quantitative correction substance;
s5, preparing a dithiocarbamate standard solution, adding the composite Raman enhancement substrate and quantitative correction substances in the same amount as those in the S3 into the standard solution, detecting by using the Raman spectrometer same as that in the S4, and drawing a working curve of the dithiocarbamate standard solution;
and S6, comparing the Raman spectrogram of the substance to be detected and the quantitative correction substance in the S4 with the working curve of the standard solution in the S5, and calculating to obtain the content of the dithiocarbamate pesticides in the tobacco leaves.
The raman enhancement substrate in step S1 is specifically constructed by: the carbon nano-cage CNCs material rich in oxygen-containing functional groups is used as the carrier after surface modification treatment, the metal nano-particle sol with surface plasmon resonance effect is used as the load, and a chemical substance with a Raman signal appearing in a Raman silent area is used as the quantitative correction substance to construct the CNCs @ metal nano-particle composite Raman enhanced substrate.
Preferably, the carbon nanocage material is a material which is synthesized by using magnesium oxide as a template and adopting a CVD method and has a regular mesoporous structure and uniform pore diameter; the aperture is 10-50 nm, and the surface of the material is rich in hydroxyl, carbonyl and carboxyl active functional groups after surface modification; the metal nanoparticle sol is one of gold nanoparticles, silver nanoparticles or copper nanoparticles.
Preferably, the CNCs @ metal nanoparticle composite Raman enhancement substrate is a liquid substrate or a solid substrate; when the composite Raman enhancement substrate is a liquid substrate, the volume ratio of the liquid composite Raman enhancement substrate to the liquid to be detected is 1-5: 1; when the composite Raman enhancement substrate is a solid substrate, the addition of the liquid drop to be detected is 10-50 uL.
Preferably, the quantitative correction substance is KSCN of 9-11 mg/L.
Preferably, the tobacco sample pretreatment method in step S2 is as follows:
placing 0.5g of cut tobacco leaf sample in a centrifuge tube, adding 5ml of ethyl acetate, performing vortex oscillation on a vortex mixing oscillator for 1min, and performing centrifugal separation at a rotation speed of not more than 4000r/min for 1min to obtain supernatant, i.e. sample extract; adding 100mg of polyamide, 100mg of N-propyl ethylenediamine solid phase adsorbent PSA, 30mg of graphite carbonized black GCB and 50mg of C18 into a purification tube in sequence, acidifying with 100 mu L of 1mol/L HCl, adding 1mL of the sample extracting solution, oscillating for 1min in a vortex mixing oscillator, centrifuging for 1min at 10000r/min, taking supernatant, placing the supernatant into a 2mL centrifuge tube, adding 100uL of 9-11 mg/L of KSCN solution, blowing to be nearly dry, adding 100 mu L of pure water, and redissolving to obtain the liquid to be detected.
Preferably, the step S4 is executed inThe wavelength of the excitation light source of the portable Raman spectrometer is 300-1500 nm, and the spectral range is 150-2800 cm-1。
Preferably, the dithiocarbamate pesticides in the tobacco leaves detected by the detection method are thiram, propineb and mancozeb.
Preferably, the working curve for plotting the dithiocarbamate standard solution in the step S5 is specifically as follows:
acetonitrile is taken as a solvent, and standard solutions of thiram, propineb and mancozeb with the concentrations of 0.05, 0.2, 1, 2, 4, 6 and 8mg/kg are respectively prepared; and performing Raman detection on the three pesticide standard solutions with different concentrations after the operation according to the methods in the steps S3 and S4, wherein the ratio of the Raman quantitative characteristic peak intensity of the pesticide to be detected to the internal standard peak intensity is used as a vertical coordinate, and the pesticide concentration is used as a horizontal coordinate to obtain quantitative standard curves of the three pesticides.
Preferably, the calculation formula of the content of the dithiocarbamate pesticides in the tobacco leaves in the step S6 is as follows:
wherein:
r is pesticide residue amount in mg/kg on a wet basis;
c, the pesticide concentration in the liquid to be detected of the sample is given by a standard curve, and the unit is ug/mL;
v is volume of extract liquid, unit is mL;
m is the sample mass in g;
cis-the concentration of the internal standard in the sample extract is ug/mL;
ci2-the concentration of the internal standard in the standard working solution is ug/mL.
The invention is further illustrated by the following specific examples, which are intended to be illustrative of the invention and are not to be construed as limiting the scope thereof.
Example 1
The method for detecting the dithiocarbamate pesticides in the tobacco leaves can quickly and accurately detect thiram, propineb and mancozeb in the dithiocarbamate pesticides in the tobacco leaves.
The specific embodiment provides a construction method of CNCs @ AuNPs liquid substrates, which comprises the following steps:
preparing a carbon carrier: placing 2g of magnesium carbonate in a tube furnace, heating to 800 ℃ under the protection of Ar gas to decompose the magnesium carbonate into a magnesium oxide template, injecting a benzene precursor into the furnace tube, reacting at the high temperature of 800 ℃ for 20min, stopping heating, and taking out a product when the temperature is reduced to be lower than 100 ℃; and (3) placing the product in a 1:1 HCl aqueous solution, stirring for 24h to remove the magnesium oxide template, repeatedly washing the product with deionized water to be neutral, and drying for later use. And adding the nano carbon material into 6M nitric acid, heating and refluxing for 2 hours at the temperature of 60 ℃, washing for a plurality of times by using deionized water, and drying in an oven for 10 hours to obtain the CNCs containing rich oxygen-containing functional groups.
Loading materials: the alcohol red gold nanoparticle sol is prepared by a method of reducing chloroauric acid by trisodium citrate, and the particle size is about 50 nm.
Weighing 4mg of the prepared CNCs material, uniformly dispersing the CNCs in 10mL of deionized water by ultrasonic, adding 2mL of the solution into 20mL of gold nanoparticle sol, reacting for 40min under the ultrasonic condition, and then stirring for 4 h. And finally, centrifuging the solution, removing the supernatant, ultrasonically dispersing the bottom precipitate in 4mL of deionized water, adding 10mg/L of KSCN serving as a quantitative correction substance, and uniformly mixing to obtain the CNCs @ AuNPs liquid substrate.
The specific embodiment provides a method for quantitatively detecting dithiocarbamate pesticides in tobacco leaves, which specifically comprises the following steps:
acetonitrile is used as a solvent, and standard solutions of thiram, propineb and mancozeb with the concentrations of 0.05, 0.2, 1, 2, 4, 6 and 8mg/kg are prepared respectively.
Performing Raman detection on the standard solutions of thiram, propineb and mancozeb: mixing 100 mu L of CNCs @ AuNPs liquid substrate with 100 mu L of standard solution to-be-detected solution for 1min, and detecting on a machine. Portable Raman spectrometer adopting 785nm light source and having spectral range of 150-2800 cm-1Integration time 10 s. The Raman spectrum test chart and the corresponding Raman characteristic peak of the three pesticide standard solutions at each concentration are shown in the attached figure 1. And taking the ratio of the Raman characteristic quantitative peak to the KSCN peak as a vertical coordinate and the pesticide concentration as a horizontal coordinate to obtain quantitative standard curves of the three pesticides. The results of quantitative analysis of the standard solutions of thiram, propineb and mancozeb are shown in table 1.
TABLE 1
The specific embodiment provides a standard-adding recovery test of thiram, propineb and mancozeb in tobacco leaves, which specifically comprises the following steps:
placing 0.5g of cut tobacco leaf sample in a centrifuge tube, adding 5ml of ethyl acetate, performing vortex oscillation on a vortex mixing oscillator for 1min, and performing centrifugal separation at a rotation speed of not more than 4000r/min for 1min to obtain supernatant, i.e. sample extract; adding 100mg of polyamide, 100mg of N-propyl ethylenediamine solid phase adsorbent PSA, 30mg of graphite carbonized black GCB and 50mg of C18 into a purification tube in sequence, acidifying with 100 mu L of 1mol/L HCl, adding 1mL of the sample extracting solution, oscillating for 1min in a vortex mixing oscillator, centrifuging for 1min at 10000r/min, taking supernatant, placing the supernatant into a 2mL centrifuge tube, adding 100uL of 9-11 mg/L KSCN solution, blowing to be nearly dry, adding 100 mu L of pure water, and redissolving to obtain the liquid to be detected. Mixing the composite Raman enhancement substrate, the liquid to be detected and the quantitative correction substance; and performing Raman detection on the mixture, wherein the Raman detection conditions are consistent with those of the standard solution, and obtaining a Raman spectrogram of the object to be detected and the quantitative correction substance. And comparing the Raman spectrogram of the substance to be detected and the quantitative correction substance with the working curve of the standard solution, and calculating according to a calculation formula of the content of the dithiocarbamate pesticides in the tobacco leaves to obtain the content of the dithiocarbamate pesticides in the tobacco leaves. The results of the tabacco leaf standard recovery tests of thiram, propineb and mancozeb are shown in table 2.
TABLE 2
The results show that: the range of the standard recovery rate is 94.7-112%, and the range of the relative standard deviation (n is 3) is 2.2-7.7%, which shows that the method has good quantitative accuracy and excellent sensitivity.
The specific embodiment provides a stability test of CNCs @ AuNPs, which specifically comprises the following steps:
in order to verify the detection performance stability of CNCs @ AuNPs, 0.5mg/L thiram standard solution is subjected to regular Raman enhancement detection every other month, the consistency of materials, reagents and instruments is ensured in each test, and the number of times of thiram is 1375cm-1The intensity of the characteristic peak is shown in the attached figure 2 in detail.
The result shows that the CNCs @ AuNPs prepared by the method have good stability of more than 12 months and long effective service time.
The specific embodiment provides a universality test for detecting pesticides by CNCs @ AuNPs, which specifically comprises the following steps:
in order to verify the applicability of the CNCs @ metal nanoparticle composite reinforced substrate detection pesticide, three pesticides with larger structural differences are selected for detection, namely fenthion, acetamiprid and difenoconazole. Preparing standard solutions of three pesticides of 0.1mg/L, wherein the Raman spectrum testing conditions are consistent with those of the standard solutions. When detection is carried out, Raman characteristic peaks of the three pesticides are clear and obvious, and are shown in the attached figure 3 in detail.
The result shows that the CNCs @ metal nanoparticle composite reinforced substrate has universality and has a good reinforcing effect on various pesticides.
Example 2
The embodiment provides a method for rapidly detecting dithiocarbamate pesticides in tobacco leaves, which comprises the following steps:
s1, constructing a composite Raman enhancement substrate; the composite Raman enhancement substrate is constructed by a carbon carrier, a load and a quantitative correction substance; uniformly dispersing the load on the surface of a carrier to form a composite substrate, adding the quantitative correction substance into the composite substrate, and uniformly mixing to obtain a composite Raman enhancement substrate;
s2, preprocessing a tobacco leaf sample to obtain a liquid to be detected;
s3, mixing the composite Raman enhancement substrate in the step S1, the liquid to be detected in the step S2 and a quantitative correction substance to obtain a mixture;
s4, detecting the mixture in the step S3 by adopting a portable Raman spectrometer to obtain a Raman spectrogram of the object to be detected and the quantitative correction substance;
s5, preparing a dithiocarbamate standard solution, adding the composite Raman enhancement substrate and quantitative correction substances in the same amount as those in the S3 into the standard solution, detecting by using the Raman spectrometer same as that in the S4, and drawing a working curve of the dithiocarbamate standard solution;
and S6, comparing the Raman spectrogram of the substance to be detected and the quantitative correction substance in the S4 with the working curve of the standard solution in the S5, and calculating to obtain the content of the dithiocarbamate pesticides in the tobacco leaves.
The raman enhancement substrate in step S1 is specifically constructed by: the carbon nano-cage CNCs material rich in oxygen-containing functional groups is used as the carrier after surface modification treatment, the metal nano-particle sol with surface plasmon resonance effect is used as the load, and a chemical substance with a Raman signal appearing in a Raman silent area is used as the quantitative correction substance to construct the CNCs @ metal nano-particle composite Raman enhanced substrate.
Preferably, the carbon nanocage material is a material which is synthesized by using magnesium oxide as a template and adopting a CVD method and has a regular mesoporous structure and uniform pore diameter; the aperture is 10-50 nm, and the surface of the material is rich in hydroxyl, carbonyl and carboxyl active functional groups after surface modification; the metal nanoparticle sol is silver nanoparticles.
Preferably, the CNCs @ metal nanoparticle composite Raman enhancement substrate is a liquid substrate, and the volume ratio of the liquid composite Raman enhancement substrate to the liquid to be detected is 1-5.
Preferably, the quantitative calibration substance is preferably 9mg/L KSCN.
Preferably, the tobacco sample pretreatment method in step S2 is as follows:
placing 0.5g of cut tobacco leaf sample in a centrifuge tube, adding 5ml of ethyl acetate, performing vortex oscillation on a vortex mixing oscillator for 1min, and performing centrifugal separation at a rotation speed of not more than 4000r/min for 1min to obtain supernatant, i.e. sample extract; adding 100mg of polyamide, 100mg of N-propyl ethylenediamine solid phase adsorbent PSA, 30mg of graphite carbonized black GCB and 50mg of C18 into a purification tube in sequence, acidifying with 100 mu L of 1mol/L HCl, adding 1mL of the sample extracting solution, oscillating for 1min in a vortex mixing oscillator, centrifuging for 1min at 10000r/min, taking supernatant, placing the supernatant into a 2mL centrifuge tube, adding 100uL of 9-11 mg/L of KSCN solution, blowing to be nearly dry, adding 100 mu L of pure water, and redissolving to obtain the liquid to be detected.
Preferably, the wavelength of the excitation light source of the portable raman spectrometer in step S4 is 1500nm, and the spectral range is 1800cm-1。
Preferably, the dithiocarbamate pesticides in the tobacco leaves detected by the detection method are thiram, propineb and mancozeb.
Preferably, the working curve for plotting the dithiocarbamate standard solution in the step S5 is specifically as follows:
acetonitrile is taken as a solvent, and standard solutions of thiram, propineb and mancozeb with the concentrations of 0.05, 0.2, 1, 2, 4, 6 and 8mg/kg are respectively prepared; and performing Raman detection on the three pesticide standard solutions with different concentrations after the operation according to the methods in the steps S3 and S4, wherein the ratio of the Raman quantitative characteristic peak intensity of the pesticide to be detected to the internal standard peak intensity is used as a vertical coordinate, and the pesticide concentration is used as a horizontal coordinate to obtain quantitative standard curves of the three pesticides.
Preferably, the calculation formula of the content of the dithiocarbamate pesticides in the tobacco leaves in the step S6 is as follows:
wherein:
r is pesticide residue amount in mg/kg on a wet basis;
c, the pesticide concentration in the liquid to be detected of the sample is given by a standard curve, and the unit is ug/mL;
v is volume of extract liquid, unit is mL;
m is the sample mass in g;
cis-the concentration of the internal standard in the sample extract is ug/mL;
ci2-the concentration of the internal standard in the standard working solution is ug/mL.
Example 3
The embodiment provides a method for rapidly detecting dithiocarbamate pesticides in tobacco leaves, which comprises the following steps:
s1, constructing a composite Raman enhancement substrate; the composite Raman enhancement substrate is constructed by a carbon carrier, a load and a quantitative correction substance; uniformly dispersing the load on the surface of a carrier to form a composite substrate, adding the quantitative correction substance into the composite substrate, and uniformly mixing to obtain a composite Raman enhancement substrate;
s2, preprocessing a tobacco leaf sample to obtain a liquid to be detected;
s3, mixing the composite Raman enhancement substrate in the step S1, the liquid to be detected in the step S2 and a quantitative correction substance to obtain a mixture;
s4, detecting the mixture in the step S3 by adopting a portable Raman spectrometer to obtain a Raman spectrogram of the object to be detected and the quantitative correction substance;
s5, preparing a dithiocarbamate standard solution, adding the composite Raman enhancement substrate and quantitative correction substances in the same amount as those in the S3 into the standard solution, detecting by using the Raman spectrometer same as that in the S4, and drawing a working curve of the dithiocarbamate standard solution;
and S6, comparing the Raman spectrogram of the substance to be detected and the quantitative correction substance in the S4 with the working curve of the standard solution in the S5, and calculating to obtain the content of the dithiocarbamate pesticides in the tobacco leaves.
The raman enhancement substrate in step S1 is specifically constructed by: the carbon nano-cage CNCs material rich in oxygen-containing functional groups is used as the carrier after surface modification treatment, the metal nano-particle sol with surface plasmon resonance effect is used as the load, and a chemical substance with a Raman signal appearing in a Raman silent area is used as the quantitative correction substance to construct the CNCs @ metal nano-particle composite Raman enhanced substrate.
Preferably, the carbon nanocage material is a material which is synthesized by using magnesium oxide as a template and adopting a CVD method and has a regular mesoporous structure and uniform pore diameter; the aperture is 10-50 nm, and the surface of the material is rich in hydroxyl, carbonyl and carboxyl active functional groups after surface modification; the metal nanoparticle sol is copper nanoparticles.
Preferably, the CNCs @ metal nanoparticle composite Raman enhancement substrate is a solid substrate; when the composite Raman enhancement substrate is a solid substrate, the addition of the liquid drop to be detected is 10-50 uL.
Preferably, the quantitative calibration substance is preferably 11mg/L of KSCN.
Preferably, the tobacco sample pretreatment method in step S2 is as follows:
placing 0.5g of cut tobacco leaf sample in a centrifuge tube, adding 5ml of ethyl acetate, performing vortex oscillation on a vortex mixing oscillator for 1min, and performing centrifugal separation at a rotation speed of not more than 4000r/min for 1min to obtain supernatant, i.e. sample extract; adding 100mg of polyamide, 100mg of N-propyl ethylenediamine solid phase adsorbent PSA, 30mg of graphite carbonized black GCB and 50mg of C18 into a purification tube in sequence, acidifying with 100 mu L of 1mol/L HCl, adding 1mL of the sample extracting solution, oscillating for 1min in a vortex mixing oscillator, centrifuging for 1min at 10000r/min, taking supernatant, placing the supernatant into a 2mL centrifuge tube, adding 100uL of 9-11 mg/L KSCN solution, blowing to be nearly dry, adding 100 mu L of pure water, and redissolving to obtain the liquid to be detected.
Preferably, the wavelength of the excitation light source of the portable raman spectrometer in step S4 is 300nm, and the spectral range is 2800cm-1。
Preferably, the dithiocarbamate pesticides in the tobacco leaves detected by the detection method are thiram, propineb and mancozeb.
Preferably, the working curve for plotting the dithiocarbamate standard solution in the step S5 is specifically as follows:
acetonitrile is taken as a solvent, and standard solutions of thiram, propineb and mancozeb with the concentrations of 0.05, 0.2, 1, 2, 4, 6 and 8mg/kg are respectively prepared; and performing Raman detection on the three pesticide standard solutions with different concentrations after the operation according to the methods in the steps S3 and S4, wherein the ratio of the Raman quantitative characteristic peak intensity of the pesticide to be detected to the internal standard peak intensity is used as a vertical coordinate, and the pesticide concentration is used as a horizontal coordinate to obtain quantitative standard curves of the three pesticides.
Preferably, the calculation formula of the content of the dithiocarbamate pesticides in the tobacco leaves in the step S6 is as follows:
wherein:
r is pesticide residue amount in mg/kg on a wet basis;
c, the pesticide concentration in the liquid to be detected of the sample is given by a standard curve, and the unit is ug/mL;
v is volume of extract liquid, unit is mL;
m is the sample mass in g;
cis-the concentration of the internal standard in the sample extract is ug/mL;
ci2-the concentration of the internal standard in the standard working solution is ug/mL.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A method for rapidly detecting dithiocarbamate pesticides in tobacco leaves is characterized by comprising the following steps:
s1, constructing a composite Raman enhancement substrate; the composite Raman enhancement substrate is constructed by a carbon carrier, a load and a quantitative correction substance; uniformly dispersing the load on the surface of a carrier to form a composite substrate, adding the quantitative correction substance into the composite substrate, and uniformly mixing to obtain a composite Raman enhancement substrate;
s2, preprocessing a tobacco leaf sample to obtain a liquid to be detected;
s3, mixing the composite Raman enhancement substrate in the step S1, the liquid to be detected in the step S2 and a quantitative correction substance to obtain a mixture;
s4, detecting the mixture in the step S3 by adopting a portable Raman spectrometer to obtain a Raman spectrogram of the object to be detected and the quantitative correction substance;
s5, preparing a dithiocarbamate standard solution, adding the composite Raman enhancement substrate and quantitative correction substances in the same amount as those in the S3 into the standard solution, detecting by using the Raman spectrometer same as that in the S4, and drawing a working curve of the dithiocarbamate standard solution;
and S6, comparing the Raman spectrogram of the substance to be detected and the quantitative correction substance in the S4 with the working curve of the standard solution in the S5, and calculating to obtain the content of the dithiocarbamate pesticides in the tobacco leaves.
2. The method for detecting dithiocarbamate pesticides in tobacco leaves according to claim 1, wherein the Raman-enhanced substrate in step S1 is specifically constructed by: the carbon nano-cage CNCs material rich in oxygen-containing functional groups is used as the carrier after surface modification treatment, the metal nano-particle sol with surface plasmon resonance effect is used as the load, and a chemical substance with a Raman signal appearing in a Raman silent area is used as the quantitative correction substance to construct the CNCs @ metal nano-particle composite Raman enhanced substrate.
3. The method for detecting dithiocarbamate pesticides in tobacco leaves according to claim 2, wherein the carbon nanocage material is a material which is synthesized by a CVD method by using magnesium oxide as a template and has a regular mesoporous structure and uniform pore diameter; the aperture is 10-50 nm, and the surface of the material is rich in hydroxyl, carbonyl and carboxyl active functional groups after surface modification; the metal nanoparticle sol is one of gold nanoparticles, silver nanoparticles or copper nanoparticles.
4. The method for detecting dithiocarbamate pesticides in tobacco leaves according to claim 2, wherein the CNCs @ metal nanoparticle composite Raman-enhanced substrate is a liquid substrate or a solid substrate; when the composite Raman enhancement substrate is a liquid substrate, the volume ratio of the liquid composite Raman enhancement substrate to the liquid to be detected is 1-5: 1; when the composite Raman enhancement substrate is a solid substrate, the addition of the liquid drop to be detected is 10-50 uL.
5. The method for detecting dithiocarbamate pesticides in tobacco leaves according to claim 1, wherein the quantitative correction substance is preferably KSCN at 9-11 mg/L.
6. The method for detecting dithiocarbamate pesticides in tobacco leaves according to claim 1, wherein the method for pretreating the tobacco leaf sample in the step S2 comprises the following steps:
placing 0.5g of cut tobacco leaf sample in a centrifuge tube, adding 5ml of ethyl acetate, performing vortex oscillation on a vortex mixing oscillator for 1min, and performing centrifugal separation at a rotation speed of not more than 4000r/min for 1min to obtain supernatant, i.e. sample extract; adding 100mg of polyamide, 100mg of N-propyl ethylenediamine solid phase adsorbent PSA, 30mg of graphite carbonized black GCB and 50mg of C18 into a purification tube in sequence, acidifying with 100 mu L of 1mol/L HCl, adding 1mL of the sample extracting solution, oscillating for 1min in a vortex mixing oscillator, centrifuging for 1min at 10000r/min, taking supernatant, placing the supernatant into a 2mL centrifuge tube, adding 100uL of 9-11 mg/L KSCN solution, blowing to be nearly dry, adding 100 mu L of pure water, and redissolving to obtain the liquid to be detected.
7. The method for detecting dithiocarbamate pesticides in tobacco leaves according to claim 1, wherein the portable Raman spectrometer in the step S4 is provided with an excitation light source with a wavelength of 300-1500 nm and a spectrum range of 150-2800 cm-1。
8. The method for detecting dithiocarbamate pesticides in tobacco leaves according to claim 1, wherein the dithiocarbamate pesticides in the tobacco leaves detected by the detection method are thiram, propineb and mancozeb.
9. The method for detecting dithiocarbamate pesticides in tobacco leaves according to claim 8, wherein the step S5 of drawing a working curve of the dithiocarbamate standard solution is specifically as follows:
acetonitrile is taken as a solvent, and standard solutions of thiram, propineb and mancozeb with the concentrations of 0.05, 0.2, 1, 2, 4, 6 and 8mg/kg are respectively prepared; and performing Raman detection on the three pesticide standard solutions with different concentrations after the operation according to the methods in the steps S3 and S4, wherein the ratio of the Raman quantitative characteristic peak intensity of the pesticide to be detected to the internal standard peak intensity is used as a vertical coordinate, and the pesticide concentration is used as a horizontal coordinate to obtain quantitative standard curves of the three pesticides.
10. The method for detecting dithiocarbamate pesticides in tobacco leaves according to claim 1, wherein the calculation formula of the content of dithiocarbamate pesticides in tobacco leaves in the step S6 is as follows:
wherein:
r is pesticide residue amount in mg/kg on a wet basis;
c, the pesticide concentration in the liquid to be detected of the sample is given by a standard curve, and the unit is ug/mL;
v is volume of extract liquid, unit is mL;
m is the sample mass in g;
cis-the concentration of the internal standard in the sample extract is ug/mL;
ci2-the concentration of the internal standard in the standard working solution is ug/mL.
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