A method for sers detection of fluoroacetamides

Abstract

A SERS detection method of fluoroacetamide, involving preparation of SERS substrate and SERS detection of fluoroacetamide. The core-shell Au@PVP of polyvinylpyrrolidone (PVP) coated gold nanoparticles is prepared as SERS substrate for quantitative analysis and detection of fluoroacetamide. Under the conditions of optimizing the addition amount of fluoroacetamide and pH value, the linear detection range of fluoroacetamide is 100 ppb-1 ppt, the detection limit is 1 ppt, and the relative standard deviation of SERS intensity is less than 10%. The Au@PVP as SERS substrate has the advantages of low cost, controllability, high detection efficiency, etc., and can be applied to practical detection of organic fluorine insecticide pesticides. The method is simple in operation, high in accuracy and sensitivity, and does not require complex operation technology, meeting the requirements of large-scale and rapid analysis and detection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of detection of fluoroacetamides, and particularly relates to a SERS detection method of fluoroacetamides. BACKGROUND

[0002] Fluoroacetamide is a small (77 Da) highly toxic chemical that was previously used as a rodenticide. Fluoroacetamide poisoning has occurred in humans, but there are few reliable rapid detection methods and reports. Therefore, it is crucial to develop a rapid detection method for fluoroacetamide. However, achieving this goal is a great challenge, mainly due to the very low molecular weight of fluoroacetamide. A series of studies have been conducted on its detection methods. Currently, the main methods for detecting fluoroacetamide at home and abroad are: sulfur-indigo blue reaction (Logan BK, Stafford DT, Tebbett IR, Moore CM. Rapid screening for 100 basic drugs and metabolites in urine using cation exchange solid-phase extraction and high-performance liquid chromatography with diode array detection. J Anal Toxicol. 1990 May-Jun; 14(3): 154-9. doi: 10.1093 / jat / 14.3.154. PMID: 2374404.), high-performance liquid chromatography (Cooney TP, Varelis P, Bendall JG. High-Throughput Quantification of Monofluoroacetate (1080) in Milk as a Response to an Extortion Threat. J Food Prot. 2016 Feb; 79(2): 273-81. doi: 10.4315 / 0362-028X.JFP-15-405. PMID: 26818988.), high-performance liquid chromatography-mass spectrometry (High Performance Liquid Chromatography-Mass Spectroscopy-Mass Spectroscopy, HPLC-MS-MS), (Bessaire T, Tarres A, Goyon A, Mottier P, Dubois M, Tan WP, Delatour T. Quantitative determination of sodium monofluoroacetate "1080" in infant formulas and dairy products by isotope dilution LC-MS / MS.Food Addit Contam Part A Chem Anal Control Expo Risk Assess. 2015; 32(11): 1885-92. doi: 10.1080 / 19440049.2015.1087057. Epub 2015 Oct 8. PMID: 26366530.), gas chromatography-mass spectrometry (Cai X, Zhang D, Ju H, Wu G, Liu X. Fast detection of fluoroacetamide in body fluid using gas chromatography-mass spectrometry after solid-phase microextraction. J Chromatogr B Analyt Technol Biomed Life Sci. 2004 Apr 5;802(2):239-45. doi: 10.1016 / S1570-0232(03)00556-7. PMID: 15018783.). The HPLC method is characterized by high sensitivity, but measures the total amount, and cannot separately quantify fluoroacetamide and its homologues. The HPLC-MS-MS method is a new detection technology developed in recent years, which has both qualitative function and high sensitivity, but the instrument is expensive. The sulfur-indigo reaction qualitatively detects fluoroacetamide, which was further developed by Logan et al. in 1990. The detection procedure first uses a methanol / water mixture to extract fluoroacetamide from the sample. At present, it has been able to qualitatively detect fluoroacetamide. Due to low efficiency and sensitivity, this method shows many limitations, such as interference, false positives and false negatives. Gas chromatography-mass spectrometry, which has high sensitivity, can detect 1 mL of blood or 1 g of tissue samples containing fluoroacetamide, with a recovery rate of 80% to 85%. However, this method is not suitable for the detection of fluoroacetamide in poisoned tissue samples. For poisoned tissue samples, fluoroacetamide must first be extracted using a mixture of acetone and water and strong acidic ethyl acetate, and then derivatized with N, N-diethyl-p-phenylenediamine. The above methods for detecting fluoroacetamide all have the disadvantages of high cost and long detection period. SUMMARY

[0003] The present application aims at solving the above problems in the prior art, and provides a SERS (surface enhanced Raman scattering) detection method for fluoroacetamide, which realizes quantitative analysis of fluoroacetamide by the relationship between the peak intensity of a Raman characteristic peak and the concentration of fluoroacetamide, through preparation of Au@PVP as a solid substrate on a silicon wafer and utilization of the uniformity and stability of the SERS substrate. The method is simple in operation, high in accuracy and sensitivity, and does not require complex operation techniques, and meets the requirements of large batch and rapid analysis and detection.

[0004] To achieve the above object, the present application adopts the following technical scheme:

[0005] A SERS detection method for fluoroacetamide, comprising the following steps:

[0006] 1) synthesis of AuNPs sol;

[0007] 2) synthesis of Au@PVP particles as a SERS substrate: taking AuNPs sol, adding PVP solution under stirring to react, and preparing Au@PVP core-shell nanoparticle sol;

[0008] 3) quantitative analysis and detection of fluoroacetamide on the SERS substrate.

[0009] In step 1), AuNPs sol is prepared by reduction of chloroauric acid with sodium citrate, and the particle size of Au nanoparticles is 55±5 nm.

[0010] In step 1), the mass percentage concentration of sodium citrate is 0.8% to 1.5%, the molar concentration of chloroauric acid is 1 to 3 mmol / L, and the volume ratio of sodium citrate to chloroauric acid is 3:5. The Au nanoparticle sol with uniform particle size can be prepared by controlling the concentration of reactants, reaction temperature, reaction time and stirring speed.

[0011] In step 1), the reaction temperature is 100 to 110℃, the reaction time is 40 to 60 min, and the magnetic stirring speed is 600 to 2000 r / min.

[0012] In step 2), the amount of the AuNPs sol is 20 to 30 mL, the magnetic stirring speed is 900 to 1200 r / min, the mass concentration of the PVP solution is 1% to 4%, the volume of the PVP solution taken is 100 to 150 μL, and the PVP solution is added dropwise to the AuNPs sol, and the stirring time is 20 to 40 min.

[0013] The specific method for quantitative analysis and detection of the fluoroacetamide on the SERS substrate in step 3) is as follows: under the optimal excitation wavelength, the fluoroacetamide solution with different concentrations is mixed with the SERS substrate and hydrochloric acid to perform surface-enhanced Raman detection; with the increase of the fluoroacetamide concentration, the Raman peak of the fluoroacetamide at a specific wavelength gradually increases; the intensity of the Raman characteristic peak of the fluoroacetamide is proportional to the amount of the fluoroacetamide, so that the fluoroacetamide is quantitatively analyzed and detected.

[0014] The optimal excitation wavelength refers to the 785 nm excitation wavelength, and the detection temperature is 20-30 DEG C; the Raman peak of the fluoroacetamide at a specific wavelength refers to the characteristic Raman peak of the fluoroacetamide at 1030 cm -1 -1 The quantitative analysis and detection refers to that under the optimal experimental condition, the logarithm of the fluoroacetamide concentration is taken as the abscissa, the peak intensity of the fluoroacetamide at the strongest characteristic peak 1030 cm 2 The linear range is 100 ppb-1 ppt, the linear correlation coefficient R is 0.99049, and the detection limit is 1 ppt.

[0015] The optimal experimental condition is that the optimal detection pH value of the fluoroacetamide is 3, the optimal detection volume ratio of the Au@PVP to the fluoroacetamide is 5:1, and water is selected as the optimal solvent for preparing the fluoroacetamide; the fluoroacetamide solution with different concentrations is mixed with the SERS substrate according to the optimal combination amount ratio, and then centrifuged to obtain a concentrated solution which is dropped on a silicon wafer to perform surface-enhanced Raman detection; with the increase of the concentration, the Raman peak of the fluoroacetamide at a specific wavelength gradually increases; the intensity of the Raman characteristic peak of the fluoroacetamide is proportional to the concentration of the fluoroacetamide, so that the fluoroacetamide is quantitatively analyzed and detected.

[0016] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0017] The present application realizes the rapid quantitative analysis of the fluoroacetamide by the relationship between the Raman characteristic peak intensity and the concentration of the fluoroacetamide by taking the Au@PVP core-shell nanoparticle as the SERS substrate. The present application takes the Au@PVP as the SERS substrate, which not only has excellent SERS Raman enhancement effect, but also has good stability and sensitivity, and the process is simple, low in cost, good in repeatability and simple in detection method and easy to operate. The fluoroacetamide is selected as the target molecule, the Raman enhancement effect of the SERS substrate on the fluoroacetamide is tested, and the experimental results show that the Au@PVP as the SERS substrate improves the Raman detection limit of the fluoroacetamide; the pH value and the volume ratio are optimized, and the fluoroacetamide at 1030 cm -1 ​The signal intensity of the characteristic Raman peak has linear relationship with the concentration, a simple, rapid and low-cost detection method is established, without complex specific modification, the Raman characteristic peak of fluoroacetamide is directly utilized for quantitative analysis and detection, the linear range of the application is 100ppb-1ppt, the linear correlation coefficient R2 is 0.9942, and the detection limit is 1ppt. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Fig. 1 is a transmission electron microscope (TEM) image of Au@PVP core-shell nanoparticles prepared in the application, wherein A is a TEM image of a single Au@PVP core-shell nanoparticle, B is a TEM image of Au@PVP, and C is a scanning electron microscope (SEM) image of Au@PVP.

[0019] Figure 2 Fig. 4 is a Raman spectrum of fluoroacetamide under different pH conditions, wherein a) pH=3, b) pH=7, and c) pH=9.

[0020] Figure 3 Fig. 5 is a Raman spectrum of Au@PVP mixed with fluoroacetamide in different proportions, wherein a) 10:0.5, b) 10:1, c) 10:2, and d) 10:3.

[0021] Figure 4 Fig. 6 is a Raman spectrum of SERS peak intensity randomly collected from 10 different sites.

[0022] Figure 5 Fig. 7 is a columnar chart of SERS peak intensity randomly collected from 10 different sites of 100ppb fluoroacetamide on a SERS substrate.

[0023] Figure 6 Fig. 8 is a SERS spectrum of fluoroacetamide in different concentrations, wherein a) 1ppt, b) 10ppt, c) 100ppt, d) 1ppb, e) 10ppt, and f) 100ppb.

[0024] Figure 7 Fig. 9 is a relationship chart of SERS intensity of fluoroacetamide at the strongest Raman peak 1030cm-1 and the negative logarithm of concentration. -1 DETAILED DESCRIPTION

[0025] In order to make the technical problems, technical solutions and beneficial effects of the application more clear and explicit, the application is further described in detail below in combination with the drawings and examples.

[0026] Example 1

[0027] 1) Synthesis of gold nanoparticles

[0028] ​Gold nanoparticles (AuNPs) were prepared using the sodium citrate reduction method. 200 mL of 0.01% chloroauric acid solution was added to a flask and magnetic stirring was initiated at 800 rpm. While boiling, 1.4 mL of 1% sodium citrate was added and the magnetic stirring speed was increased to 1500 rpm. The solution changed color from light yellow to colorless to reddish brown. Stirring was continued for 40 minutes and then cooled naturally to room temperature to produce gold nanoparticles of uniform size.

[0029] Au@PVP core-shell nanoparticles were prepared by chemical reduction. 20 mL of the prepared AuNPs sol was placed in a flask, and 100 μL of a 1% PVP solution was added. The reaction was allowed to proceed at 25°C with magnetic stirring at 1000 rpm for 20 minutes. This yielded Au@PVP core-shell nanoparticles with a shell thickness of approximately 3.49 nm. The particle size, shape, and shell thickness of the core-shell nanoparticles were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM).

[0030] Figure 1 TEM and SEM images of the prepared Au@PVP core-shell nanoparticles. Figure 1 In the figure, the scale bars are 50 nm (Figures A and B) and 60 nm (Figure C). Figure 1 It can be seen that the Au nanoparticles are surrounded by a PVP shell with a shell thickness of about 3.49 nm (Figure A). The particle size of the Au@PVP core-shell nanoparticles is about 55 nm (Figure B). The particle size and shape of the nanoparticles are relatively uniform (Figure C).

[0031] 2) Optimization of optimal pH

[0032] The added volumes of Au@PVP and 100 ppb fluoroacetamide were determined, the pH of the solution was adjusted to (3, 7, 9), and the surface enhanced Raman spectrum of fluoroacetamide was scanned to determine the optimal pH.

[0033] See also Figure 2 In Figures a to c, the pH values ​​of the solutions are 3, 7, and 9, respectively. It can be seen that at different pH values, the concentration of fluoroacetamide at 1030 cm -1 There is a strong Raman peak. When pH=3, the Raman signal peak reaches the strongest. When the pH value of fluoroacetamide is 7 or 9 ( Figure 2 In b and c), the signal intensity of the Raman characteristic peak decreased significantly. Therefore, the pH of the Au@PVP and fluoroacetamide was fixed at 3 in subsequent detection.

[0034] 3) Optimization of the optimal addition amount

[0035] Determine the volume of Au@PVP and hydrochloric acid, add different volumes of fluoroacetamide, scan the surface enhanced Raman spectrum of fluoroacetamide, and determine the optimal amount ratio of Au@PVP and fluoroacetamide.

[0036] Figure 3 To fix the concentration of Au@PVP and fluoroacetamide (FAM) (100 ppb), control the volume ratio of them, and collect SERS spectrum. In figures a~d, the volume ratio of Au@PVP, fluoroacetamide (FAM) and hydrochloric acid is 10:0.5:0.6, 10:1:0.6, 10:2:0.6, 10:3:0.6 respectively. It can be seen that with the gradual increase of the addition amount of fluoroacetamide (FAM), the Raman peak at 1030 cm -1 There is a stronger Raman peak, and when the addition amount of fluoroacetamide is 100 μL, the Raman signal peak reaches the strongest. But with the addition amount of fluoroacetamide exceeding 100 μL, the Raman intensity will not increase with the addition amount of fluoroacetamide. Therefore, the volume ratio of Au@PVP, fluoroacetamide (FAM) and hydrochloric acid is fixed to 10:2:0.6 in subsequent detection.

[0037] 4) SERS detection of fluoroacetamide

[0038] Take the SERS substrate prepared by mixing PVP gold (Au@PVP) and 100 ppb fluoroacetamide at a ratio of 5:1, scan the Raman spectrum, do 10 times in parallel, randomly select points on the substrate with a 785 nm excitation wavelength, and get the surface enhanced Raman spectrum of fluoroacetamide corresponding to different points. Compare the Raman peak intensity of fluoroacetamide collected in 10 parallel to determine the uniformity of the substrate.

[0039] Figure 4 To get the SERS spectrum of 10 different position points randomly. After mixing Au@PVP and 100 ppb fluoroacetamide and 1 mol / L HCl at a ratio of 10:2:0.6, randomly select ten different points for SERS detection, measure the Raman peak intensity of fluoroacetamide, and draw the intensity of each characteristic Raman peak of different position points. Figure 4 ). Calculate the relative standard deviation (RSD) of the Raman peak intensity of 10 different position points from the Raman peak intensity, which is 3.36%, all less than 10% (see Figure 5 ), which shows that the uniformity of fluoroacetamide on the SERS substrate is good, and it can be applied to the quantitative analysis of surface enhanced Raman of fluoroacetamide.

[0040] The Au@PVP core-shell nanoparticles are mixed with different concentration of fluoroacetamide solution (100ppb, 10ppb, 1ppb, 100ppt, 10ppt, 1ppt) in the proportion of 5:1, and then the Raman spectrum is collected to quantitatively detect the fluoroacetamide. Figure 6 Figure 6 The Raman spectra of 1ppt, 10ppt, 100ppt, 1ppb, 10ppb and 100ppb fluoroacetamide aqueous solution added dropwise on the SERS substrate are shown in a to f, respectively, and the concentration of fluoroacetamide is measured three times. -1 The greater the concentration of fluoroacetamide is, the stronger the Raman peak intensity at 1030cm -1 The logarithm of the peak intensity at 1030cm Figure 7 The standard curve is drawn (the error bar in the standard curve represents the standard deviation), and it can be seen that the logarithm of the concentration and the Raman peak intensity have a certain linear relationship, the linear range is 100ppb-1ppt, the linear correlation coefficient R 2 reaches 0.9942, the detection limit is 1ppt, the method is simple in operation, low in detection cost and fast in detection speed.

[0041] The Au@PVP is used as the SERS substrate, which has excellent SERS Raman enhancement effect, good stability and sensitivity, simple process, low cost, good repeatability and simple and easy-to-operate detection method. The fluoroacetamide is used as the target molecule, the Raman enhancement effect of the SERS substrate on the fluoroacetamide is tested, and the experimental results show that the Au@PVP used as the SERS substrate improves the Raman detection limit of the fluoroacetamide. By optimizing the pH value and the volume ratio, the signal intensity of the characteristic Raman peak of the fluoroacetamide at 1030cm -1 has a linear relationship with the concentration, a simple, rapid and low-cost detection method is established, without complex specific modification, and the fluoroacetamide is directly used for quantitative analysis and detection by using the Raman characteristic peak.​

Claims

1. A SERS detection method for fluoroacetamide, characterized in that The following steps are involved: 1) Synthesis of AuNPs sol; 2) Synthesis of Au@PVP particles as SERS substrate: AuNPs sol was taken and PVP solution was added under stirring to prepare Au@PVP core-shell nanoparticle sol; 3) Quantitative analysis and detection of fluoroacetamide on SERS substrate.

2. The SERS detection method for fluoroacetamide according to claim 1, wherein: In step 1), AuNPs sol is prepared by reducing chloroauric acid with sodium citrate, and the particle size of Au nanoparticles is 55±5 nm.

3. The SERS detection method for fluoroacetamide according to claim 2, wherein: In step 1), the mass percentage concentration of sodium citrate is 0.8% to 1.5%, the molar concentration of chloroauric acid is 1 to 3 mmol / L, and the volume ratio of sodium citrate to chloroauric acid is 3:

5.

4. The SERS detection method for fluoroacetamide according to claim 2, wherein: In step 1), the reaction temperature is 100-110° C., the reaction time is 40-60 min, and the magnetic stirring speed is 600-2000 r / min.

5. The SERS detection method for fluoroacetamide according to claim 1, wherein: In step 2), the amount of the AuNPs sol is 20 to 30 mL, the magnetic stirring speed is 900 to 1200 r / min, the mass concentration of the PVP solution is 1% to 4%, the volume of the PVP solution is 100 to 150 μL, and the PVP solution is added dropwise to the AuNPs sol, and the stirring time is continuous for 20 to 40 min.

6. The SERS detection method for fluoroacetamide according to claim 1, wherein: In step 3), the specific method for quantitative analysis and detection of fluoroacetamide on the SERS substrate is as follows: at the optimal excitation wavelength, fluoroacetamide solutions of different concentrations are mixed with the SERS substrate and hydrochloric acid, and surface enhanced Raman detection is performed. As the concentration of fluoroacetamide increases, the Raman peak of fluoroacetamide at a specific wavelength gradually increases. The intensity of the Raman characteristic peak of fluoroacetamide is proportional to the amount of fluoroacetamide, so as to quantitatively analyze and detect fluoroacetamide.

7. The SERS detection method for fluoroacetamide according to claim 6, wherein: The optimal excitation wavelength refers to an excitation wavelength of 785 nm, and the detection temperature is 20° C. to 30° C.; the Raman peak of fluoroacetamide at a specific wavelength refers to the Raman peak of fluoroacetamide at 1030 cm -1 The quantitative analysis and detection refers to the logarithm of the fluoroacetamide concentration as the horizontal axis under the optimal experimental conditions, with the strongest characteristic peak of fluoroacetamide at 1030cm -1 The peak intensity at the ordinate was used to establish a standard curve for quantitative detection of fluoroacetamide. The detection range was 1ppm~1ppt, the linear range was 100ppb~1ppt, and the linear correlation coefficient R 2 The detection limit is 1ppt.

8. The SERS detection method for fluoroacetamide according to claim 7, wherein: Under the optimal experimental conditions, the optimal detection pH value of fluoroacetamide is 3, and the optimal detection volume ratio of Au@PVP to fluoroacetamide is 5:1; fluoroacetamide solutions of different concentrations are mixed with the SERS substrate according to the optimal binding ratio and then centrifuged for surface enhanced Raman detection.

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