A resonance light scattering method for determining organophosphorus pesticides in camellia oil

Abstract

The invention provides a resonance light scattering method for determining organophosphorus pesticides in camellia oil. With monocrotophos as an organophosphorus pesticide model, a tetradentate Schiff base-iron (III) metal complex B with dual receptor properties is synthesized based on 5-nitrosalicylicaldehyde, o-phenylenediamine and ferric nitrate nonahydrate as substrates. The central ion iron (III) of the complex B can recognize the phosphate group in the organophosphorus pesticide molecule and coordinate with it; the nitro group (-NO2) on the ligand of the complex B can recognize the amino group (-NH2) of the monocrotophos and bind with it through hydrogen bonds, thereby forming a dual receptor sandwich complex and generating an aggregation reaction so that the system generates a strong resonance light scattering signal at 300 nm. When the concentration of the monocrotophos is 0μM-1.1μM, the resonance light scattering intensity of the system is linearly correlated with the concentration of the monocrotophos, and the linear equation is I=1375.9 c(μM)+527.71. This method was applied to the detection of actual camellia oil samples, with a recovery rate in the range of 97.0%-103.0% and a relative standard deviation of 1.5%-3.8%.

Description

Technical Field

[0001] The invention discloses a resonance light scattering method for determining organophosphorus pesticides in camellia oil, belonging to the technical field of camellia oil detection. Background Art

[0002] In modern agriculture, pesticides are widely used to ensure the yield of crops and improve the quality of agricultural products. However, the negative impact of the widespread use of pesticides has also been closely watched. Pesticide residues in crops and the environment have always been one of the hot issues in contemporary agricultural production and food safety. According to research reports, there are about 3 million cases of pesticide poisoning in the world each year, of which 220,000 die. Among the many categories of pesticides, organophosphorus pesticides have been widely promoted due to their good pest control effect, low cost, and low persistence. For example, about 70% of the insecticides currently used are organophosphorus pesticides. However, organophosphorus pesticides are also toxic and harmful to human health. For example, organophosphorus can inhibit the activity of acetylcholinesterase in the human body and affect the central nervous system, which may cause respiratory paralysis or even death. Camellia oil (also known as camellia oil, tea seed oil, wild camellia oil) is taken from the seeds of the oil tea tree. It is a highly nutritious vegetable oil unique to southern my country and is known as "longevity oil", "longevity oil" and "soft gold in oil". Camellia oil is one of the most common camellia products and is loved by people for its extremely high nutritional value. However, during the cultivation of camellia seeds, it is also susceptible to organophosphorus pesticide contamination. Therefore, the detection of organophosphorus pesticide residues in camellia oil is crucial to ensure food safety. Currently, the detection methods for organophosphorus pesticide residues reported mainly include enzyme-linked immunosorbent assay, spectrophotometry, chromatography-mass spectrometry, fluorescence, colorimetry, electrochemical method, etc. However, these methods all have shortcomings, such as the cumbersome operation of enzyme-linked immunosorbent assay and expensive reagents, the need for complex reactions and low sensitivity of spectrophotometry, and the need for toxic organic solvents and complex operation of chromatography-mass spectrometry. Therefore, it is of great significance to develop new methods for detecting organophosphorus pesticides.

[0003] Resonance light scattering spectroscopy has the advantages of high sensitivity, simple operation and low cost. It has been successfully applied to the detection of a variety of target molecules, including inorganic ions, organic molecules and biomacromolecules. So far, the RLS method has not been applied to the detection of organophosphorus in camellia oil. Therefore, it is of great significance to develop a new method for the detection of organophosphorus pesticide residues in camellia oil products. It is understood that the RLS method has been successfully applied to the analysis of phosphate-containing substances such as ATP (adenosine triphosphate) and fructose diphosphate (F-1,6-BP). For example, He et al. prepared a binuclear uranyl complex and aptamer-modified gold nanoparticles and used them as optical probes to create a resonance light scattering method for the determination of ATP. The principle of this method is that ATP specifically binds to the binuclear uranyl complex and aptamer-modified gold nanoparticles in turn and aggregates, causing the system to produce a strong RLS signal; Li et al. reported a resonance light scattering (RLS) method for the determination of fructose diphosphate (FBPs) in aqueous solution using 1,6-diphosphate fructose (F-1,6-BP) as a model analyte. This method uses a uranyl-Schiff base complex and cysteamine-modified gold nanoparticles (U-Sal-Cy-GNPs) as optical probes. The GNPs are aggregated by utilizing the specific affinity of the uranium-Schiff base complex for the phosphate group, thereby generating a strong RLS signal. The concentration of FBPs shows a good linear relationship with the RLS intensity within a certain range; in addition, Li et al. also reported a resonance light scattering method based on a bipolar tetradentate Schiff base (H4L) to measure fructose 1,6-diphosphate. Unlike Li, this method can detect F-1,6-BP in drug injections and human urine, which has great application value. Organophosphorus pesticide molecules are also molecules containing phosphoester groups and other groups (such as amino groups). Inspired by this, this paper uses monocrotophos as a model to establish a new method for detecting organophosphorus pesticides. This method is based on the specific recognition ability of tetradentate Schiff base-iron complexes for phosphate groups and amino groups in monocrotophos molecules. When complex B coexists with monocrotophos, the central ion iron (III) of complex B can recognize the phosphate group in the monocrotophos molecule and coordinate with it; the nitro group (-NO2) on the ligand of complex B can recognize the amino group (-NH2) of monocrotophos and bind to it through hydrogen bonds, thus forming a complex and aggregating. When the complex aggregates, the system generates a strong resonance light scattering signal. Based on this, we established an RLS method for the direct determination of monocrotophos. This method has been successfully applied to the detection of organic phosphorus in camellia oil with satisfactory results.

[0004] The existing resonance light scattering method for determining organophosphorus pesticides in camellia oil is not effective, the detection recovery rate of camellia oil samples is not high, and the relative standard deviation is low. Now there is an urgent need for a resonance light scattering method for determining organophosphorus pesticides in camellia oil to solve the above problems. Summary of the invention

[0005] In view of the shortcomings of the prior art, the object of the present invention is to provide a resonance light scattering method for determining organophosphorus pesticides in camellia oil, so as to solve the problems raised in the above background technology.

[0006] In order to achieve the above-mentioned purpose, the present invention is realized by the following technical scheme: a resonance light scattering method for determining organophosphorus pesticides in camellia oil, comprising instruments and reagents, wherein the instruments include a fluorescence spectrometer, an element analyzer, a Fourier transform infrared spectrometer and a nuclear magnetic resonance hydrogen spectrometer, and the reagents include o-phenylenediamine, 5-nitrosalicylicylaldehyde, ferric nitrate nonahydrate, anhydrous ethanol, monocrotophos, tris(hydroxymethyl)aminomethane, hydrochloric acid, acetonitrile, acetic acid, anhydrous magnesium sulfate, anhydrous sodium acetate, ethyl acetate, PSA, C18, secondary pure water and ceramic homogenizer.

[0007] Furthermore, the fluorescence spectrometer is used for RLS analysis research.

[0008] Furthermore, the elemental analyzer, Fourier transform infrared spectrometer and nuclear magnetic resonance hydrogen spectrometer are used to characterize the structure of complex B respectively.

[0009] Further, the synthetic route of complex B comprises the following steps:

[0010] (1) A solution of 5-nitrosalicylicylaldehyde (0.0541 g, 0.5 mmol) in anhydrous ethanol (15 mL) was added dropwise to an ethanol solution (10 mL) of o-phenylenediamine (0.1673 g, 1 mmol). The resulting mixture was stirred in a 40°C water bath for half an hour. Then, an ethanol solution (10 mL) of ferric nitrate nonahydrate (0.1669 g, 0.05 mol) was added under continuous stirring. The resulting solution was stirred for four hours and filtered from ethanol to obtain a dark orange-red solid powder from the filtrate.

[0011] (2) Transfer 5 g of camellia seed oil to a 50 mL centrifuge tube and add 10 mL of double distilled water. Vortex the mixture for 2 min and let it stand for 30 min. Then add 15 mL of acetonitrile-acetic acid solution (99:1), 6 g of magnesium sulfate, 1.5 g of sodium acetate and a ceramic homogenizer to the centrifuge tube. Vortex for 1 min and centrifuge at 4000 rpm for 5 min. Transfer 8 mL of the supernatant to another 15 mL centrifuge tube.

[0012] (3) MgSO4 (1200 mg), PSA (400 mg) and C18 (400 mg) were added to the supernatant respectively. After vortexing for 1 min, the mixture was centrifuged at 4000 rpm for 5 min. 2 mL of the supernatant was transferred to another 10 mL test tube and blown to near dryness with N2 in a 40 °C water bath. After adding 1 mL of ethyl acetate, the solution was filtered through a 0.22 μm organic filter membrane.

[0013] (4) Weigh an appropriate amount of solid powder of ligand B and dissolve it in DMF to prepare a solution with a concentration of 0.1 mM. Weigh monocrotophos and prepare a solution with a concentration of 0.1 mM.

[0014] (5) Add an appropriate amount of monocrotophos standard solution or monocrotophos sample solution to a 10 mL graduated tube, then add 70 μL of 0.1 mM ligand B solution and 2 mL of 0.1 mM Tris-HCl buffer solution (pH = 8.5), and make up to 10 mL with double distilled water. Incubate the solution at room temperature for 20 min, and then record the RLS spectrum of the system.

[0015] Furthermore, monocrotophos solutions of different concentrations were prepared, and RLS synchronous scanning was performed using the controlled variable method to analyze the effects of ligand concentration, acidity, and reaction time on the RLS intensity of the system.

[0016] The beneficial effects of the present invention are as follows: a resonance light scattering method for determining organophosphorus pesticides in camellia oil according to the present invention is based on the specific recognition ability of a tetradentate Schiff base-iron complex to a phosphate group and an amino group in a monocrotophos molecule. When a complex B coexists with monocrotophos, the central ion iron (III) of the complex B can recognize the phosphate group in the monocrotophos molecule and coordinate with it; the nitro group (-NO2) on the ligand of the complex B can recognize the amino group (-NH2) of the monocrotophos and bind with it through a hydrogen bond, thereby generating a complex and aggregating. When the complex aggregates, the system generates a strong resonance light scattering signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0018] Figure 1 The synthetic route of complex B in a resonance light scattering method for determining organophosphorus pesticides in camellia oil of the present invention;

[0019] Figure 2 This is a structural representation diagram of complex B in a resonance light scattering method for determining organophosphorus pesticides in camellia oil according to the present invention;

[0020] Figure 3 A resonance light scattering spectrum diagram of a resonance light scattering method for determining organophosphorus pesticides in camellia oil according to the present invention;

[0021] Figure 4 This is a quantitative analysis diagram of a resonance light scattering method for determining organophosphorus pesticides in camellia oil according to the present invention;

[0022] Figure 5 The diagram is an RLS spectrum diagram of different ions in a resonance light scattering method for determining organophosphorus pesticides in camellia oil according to the present invention. DETAILED DESCRIPTION

[0023] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0024] See also Figure 1-Figure 5 The present invention provides a technical solution: a resonance light scattering method for determining organophosphorus pesticides in camellia oil, comprising instruments and reagents, the instruments comprising a fluorescence spectrometer, an element analyzer, a Fourier transform infrared spectrometer and a nuclear magnetic resonance hydrogen spectrometer, and the reagents comprising o-phenylenediamine, 5-nitrosalicylicylaldehyde, ferric nitrate nonahydrate, anhydrous ethanol, monocrotophos, tris(hydroxymethyl)aminomethane, hydrochloric acid, acetonitrile, acetic acid, anhydrous magnesium sulfate, anhydrous sodium acetate, ethyl acetate, PSA, C18, secondary pure water and a ceramic homogenizer.

[0025] Fluorescence spectrometer was used for RLS analysis, and elemental analyzer, Fourier transform infrared spectrometer and nuclear magnetic resonance hydrogen spectrometer were used to characterize the structure of complex B, respectively.

[0026] The synthetic route of complex B comprises the following steps:

[0027] (1) A solution of 5-nitrosalicylicylaldehyde (0.0541 g, 0.5 mmol) in anhydrous ethanol (15 mL) was added dropwise to an ethanol solution (10 mL) of o-phenylenediamine (0.1673 g, 1 mmol). The resulting mixture was stirred in a 40°C water bath for half an hour. Then, an ethanol solution (10 mL) of ferric nitrate nonahydrate (0.1669 g, 0.05 mol) was added under continuous stirring. The resulting solution was stirred for four hours and filtered from ethanol to obtain a dark orange-red solid powder from the filtrate.

[0028] (2) Transfer 5 g of camellia seed oil to a 50 mL centrifuge tube and add 10 mL of double distilled water. Vortex the mixture for 2 min and let it stand for 30 min. Then add 15 ml of acetonitrile-acetic acid solution (99:1), 6 g of magnesium sulfate, 1.5 g of sodium acetate and a ceramic homogenizer to the centrifuge tube, vortex for 1 min, centrifuge at 4000 rpm for 5 min, and transfer 8 mL of the supernatant to another 15 mL centrifuge tube.

[0029] (3) MgSO4 (1200 mg), PSA (400 mg) and C18 (400 mg) were added to the supernatant respectively. After vortexing for 1 min, the mixture was centrifuged at 4000 rpm for 5 min. 2 mL of the supernatant was transferred to another 10 mL test tube and blown to near dryness with N2 in a 40 °C water bath. After adding 1 mL of ethyl acetate, the solution was filtered through a 0.22 μm organic filter membrane.

[0030] (4) Weigh an appropriate amount of solid powder of ligand B and dissolve it in DMF to prepare a solution with a concentration of 0.1 mM. Weigh monocrotophos and prepare a solution with a concentration of 0.1 mM;

[0031] (5) Add an appropriate amount of monocrotophos standard solution or monocrotophos sample solution to a 10 mL graduated tube, then add 70 μL of 0.1 mM ligand B solution and 2 mL of 0.1 mM Tris-HCl buffer solution (pH = 8.5), and make up to 10 mL with double distilled water. Incubate the solution at room temperature for 20 min, and then record the RLS spectrum of the system.

[0032] Furthermore, monocrotophos solutions of different concentrations were prepared, and RLS synchronous scanning was performed using the controlled variable method to analyze the effects of ligand concentration, acidity, and reaction time on the RLS intensity of the system.

[0033] Resonance light scattering spectra of different systems are shown in Figure 2. Figure 3 As shown in the figure, the curves from bottom to top are the resonance light scattering spectra of the monocrotophos solution, the ligand B solution, and the mixed solution of ligand B and monocrotophos in the system with a pH value of 8.5. It can be seen from the figure that after the ligand B and monocrotophos are mixed, the resonance light scattering intensity of the system is significantly enhanced, which indicates that the ligand B and monocrotophos are combined into a complex in the solution and undergo aggregation reaction to form an aggregate, resulting in an increase in the molecular mass of the system, thereby generating a strong resonance light scattering signal, wherein the maximum scattering peak of the aggregate is located at 300nm.

[0034] Under the optimized conditions, a series of monocrotophos solutions with different concentration gradients were used to calibrate the analysis and detection, and the resonance light scattering spectra of the system with different concentrations of monocrotophos solutions were obtained. When there was no monocrotophos in the system, the RLS intensity was relatively weak. As the concentration of the added monocrotophos solution continued to increase, the resonance light scattering intensity of the system also gradually increased, and had a good linear relationship within a certain concentration range. The illustration in the upper right corner is the standard curve of monocrotophos with different concentration gradients. The linear range is between 0M-1.1M, the linear regression equation is I=1375.9c(μM)+527.71, and the correlation coefficient R2=0.9919. According to the formula LOD=3Sb / m (Sb is the blank standard deviation, m is the slope of the working curve), the detection limit of this method is calculated to be 30nM, so this method can be used for the quantitative analysis of monocrotophos.

[0035] Figure 4 The RLS spectra of the monochromatic system b under different solutions. The concentration of B is 0.7 μM. From bottom to top, the concentrations of monochromatic phenols in the corresponding solutions are 0, 0.1, 0.3, 0.5, 0.8 and 1.1 μM, respectively. The solution reaction time and reaction time are 8.5 min and 25 min at pH, respectively, and the calibration curve is shown as an inset.

[0036] In order to study the practicality and effectiveness of this method in camellia oil, five groups of camellia oil from different manufacturers (#1,; #2, original fragrant camellia oil; #3, organic camellia oil,; #4 camellia oil; #5, camellia oil) were prepared for analysis of actual samples. At the same time, in order to evaluate the reliability of this method, a spiked recovery experiment was carried out on a standard concentration of monocrotophos solution, and the experimental results are shown in Table 1. It can be seen from the table that the average recovery rates of the five groups of samples were in the range of 97.0%-103.0%, and the relative standard deviations were between 1.5%-3.8%, indicating that this method has good practicality and accuracy and is suitable for the detection of organophosphorus in camellia oil. The analysis results of real samples in different camellia seed oils (n=6) are shown in Table 1.

[0037]

[0038] A tetradentate Schiff base-iron (III) complex B was prepared, and its structure was characterized, camellia oil sample pretreatment, reaction conditions were optimized, and the resonance light scattering spectral properties were studied. The experimental results showed that under the optimized conditions of pH 8.5, 70L of complex B and 20min of reaction time, the resonance light scattering intensity had a good linear relationship with the concentration of monocrotophos. In the feasibility study of actual samples, the spiked recoveries of five groups of camellia oil samples produced from different manufacturers were between 97.0% and 103.0%, and the RSDs were all in the range of 1.5% to 3.8%. In summary, this method has the advantages of high extraction efficiency, good purification effect, high recovery rate and good accuracy, and has important application significance for the detection of organophosphorus in camellia oil.

[0039] The characterization of complex B was carried out by elemental analysis, FTIR, and 1HNMR. For elemental analysis, calculated results were: C, 52.20; H, 2.61; N, 12.20; found: C, 52.41; H, 3.38; N, 12.43, for FTIR (KBr): ν(C=N)=1619cm-1, ν(skeleton vibration)=1523cm-1, ν(-NO2)=1342cm-1 (Fig. 2), for 1HNMR (400MHz, DMSO-d6): δ=9.20ppm(s, 2H, Ar-H), δ=8.78ppm(s, 2H, N=CH), δ=8.28ppm(d, 2H, Ar-H), δ=7.74-7.11ppm(m, 6H, Ar-H).

[0040] Based on the specific recognition ability of the tetradentate Schiff base-iron complex for the phosphate group and amino group in the monocrotophos molecule, when complex B coexists with monocrotophos, the central ion iron (III) of complex B can recognize the phosphate group in the monocrotophos molecule and coordinate with it; the nitro group (-NO2) on the ligand of complex B can recognize the amino group (-NH2) of monocrotophos and bind to it through hydrogen bonds, thereby forming a complex and aggregation. When the complex aggregates, the system generates a strong resonance light scattering signal.

[0041] In order to explore the anti-interference and selectivity of monocrotophos based on resonance light scattering, the effects of certain metal ions and inorganic phosphates on the reaction system were investigated according to experimental methods. The results are as follows: Figure 5 As shown, 10 times the amount of inorganic metal ions (K + 、Na + , Li + Mg 2+ , Cu 2+ , Ca 2+ , Ba 2+ 、Zn 2+ 、Co 2+ , Pb 2+ 、Al 3+ ), inorganic phosphate (PO4 3- 、HPO4 2- 、H2PO 4- ) do not interfere with the determination of monocrotophos. This shows that the resonance light scattering method for determining monocrotophos using ligand B as a double sandwich receptor has good selectivity.

[0042] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0043] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A resonance light scattering method for determining organophosphorus pesticides in camellia oil, comprising an instrument and reagents, characterized in that: The instruments include a fluorescence spectrometer, an element analyzer, a Fourier transform infrared spectrometer and a nuclear magnetic resonance hydrogen spectrometer, and the reagents include o-phenylenediamine, 5-nitrosalicylicylaldehyde, ferric nitrate nonahydrate, anhydrous ethanol, monocrotophos, tris(hydroxymethyl)aminomethane, hydrochloric acid, acetonitrile, acetic acid, anhydrous magnesium sulfate, anhydrous sodium acetate, ethyl acetate, PSA, C18, secondary pure water and ceramic homogenizer; The element analyzer, Fourier transform infrared spectrometer and nuclear magnetic resonance hydrogen spectrometer are respectively used to characterize the structure of complex B. The synthesis route of complex B includes the following steps: (1) 15 mL of anhydrous ethanol containing 0.0541 g, 0.5 mmol of 5-nitrosalicylic aldehyde was added dropwise to 10 mL of an ethanol solution containing 0.1673 g, 1 mmol of o-phenylenediamine, and the resulting mixture was stirred in a 40°C water bath for half an hour, and then 10 mL of an ethanol solution containing 0.1669 g, 0.05 mol of ferric nitrate nonahydrate was added under continuous stirring conditions. The resulting solution was stirred for four hours and filtered from the ethanol, and a dark orange-red solid powder was obtained from the filtrate; (2) Transfer 5 g of camellia seed oil to a 50 mL centrifuge tube and add 10 mL of double distilled water. Vortex the mixture for 2 min and let it stand for 30 min. Then, add 15 mL of 99:1 acetonitrile-acetic acid solution, 6 g of magnesium sulfate, 1.5 g of sodium acetate and a ceramic homogenizer to the centrifuge tube. Vortex for 1 min and centrifuge at 4000 rpm for 5 min. Transfer 8 mL of the supernatant to another 15 mL centrifuge tube. (3) 1200 mg MgSO4, 400 mg PSA and 400 mg C18 were added to the supernatant respectively. After vortexing for 1 min, the mixture was centrifuged at 4000 rpm for 5 min. 2 mL of the supernatant was transferred to another 10 mL test tube and blown to near dryness with N2 in a 40 °C water bath. After adding 1 mL of ethyl acetate, the solution was filtered through a 0.22 μm organic filter membrane. (4) Weigh an appropriate amount of solid powder of ligand B and dissolve it in DMF to prepare a solution with a concentration of 0.1 mM. Weigh monocrotophos and prepare a solution with a concentration of 0.1 mM. (5) Add an appropriate amount of monocrotophos standard solution or monocrotophos sample solution to a 10 mL graduated tube, then add 70 μL of 0.1 mM ligand B solution, 2 mL of 0.1 mM Tris-HCl buffer solution (the pH of the Tris-HCl buffer solution is 8.5), and make up to 10 mL with double distilled water. Incubate the solution at room temperature for 20 min, and then record the RLS spectrum of the system.

2. The resonance light scattering method for determining organophosphorus pesticides in camellia oil according to claim 1, characterized in that: The fluorescence spectrometer was used for RLS analysis studies.

3. The resonance light scattering method for determining organophosphorus pesticides in camellia oil according to claim 1, characterized in that: Monocrotophos solutions with different concentrations were prepared, and RLS synchronous scanning was performed using the controlled variable method to analyze the effects of ligand concentration, acidity and reaction time on the RLS intensity of the system.

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