Investigation of the adsorption of pymetrozine on the Au@AgNPs surface and its application in the rapid detection of pymetrozine residues in apple.

Pymetrozine is widely used in agriculture to control pests, and its residue may pose a threat to humans. In this study, the adsorption behavior of pymetrozine on Au@AgNPs surfaces in different solutions was investigated by calculation of ACD/Labs, density functional theory, UV-vis spectra, zeta potential and surface-enhanced Raman scattering. Then, a SERS method for detection of pymetrozine residues in apples was established based on the adsorption study. The results showed that pymetrozine was adsorbed on Au@AgNPs surface in different forms in various solutions and high SERS sensitivity of pymetrozine was obtained by the synergistic effect of pymetrozine, Au@AgNPs and NaOH. A simple SERS method has been established to detect pymetrozine in apples with a LOD of 0.038 mg/kg, linear range of 0.05-1.00 mg/kg, recovery of 71.93-117.49 % and RSD low than 11.70 %. This study provides a reference for rapid detection of pymetrozine in agricultural products.

Real-time and in situ monitoring of organosilicon-induced thiram penetration into cabbage leaves by surface-enhanced Raman scattering mapping.

BACKGROUND: Understanding pesticide penetration behavior is important for effective application of pesticides. However, there is a lack of an effective method to monitor pesticide penetration behavior and its changing process. In the present study, a novel surface-enhanced Raman scattering (SERS) mapping method was used for real-time and in situ tracking of the penetration behaviors of thiram and thiram-organosilicon mixture on cabbage leaves. RESULTS: The results suggest that thiram has very weak ability to penetrate into cabbage leaves. However, when the thiram-organosilicon mixture was placed on leaf surfaces, a clear thiram signal was detected inside the leaf after 2 h of exposure, a strong signal was observed after 12 h, and the penetration depth of thiram was approximately 200 µm after 48 h. CONCLUSION: SERS mapping was demonstrated to be a reliable method for in situ monitoring of organosilicon-induced thiram penetration into cabbage leaf over time. The present study provides a new reference for rationally selecting adjuvants, effectively applying pesticides, and reducing pesticides residue in food. © 2022 Society of Chemical Industry.

Degradation of Sulfoxaflor in Water and Soil: Kinetics, Degradation Pathways, Transformation Product Identification, and Toxicity.

Hydrolysis, photolysis, and soil degradation are important degradation pathways of pesticides and might generate toxic chemicals and pose threats to the environment. Sulfoxaflor is a widely used neonicotinoid pesticide, but few studies have been conducted to research its environmental behaviors and residues. Herein, the hydrolysis and photolysis of sulfoxaflor in water and degradation in four typical Chinese soils were systematically studied. In addition, degradation products, pathways, and toxicity to Daphnia magna were also investigated. Sulfoxaflor can undergo photolysis and soil degradation, and the degradation percentage was greater than 90% after 96 h or 96 days, respectively. However, sulfoxaflor was not degraded or only slightly degraded during in hydrolysis and was not photodegraded in acidic water or sterilized soil. Four degradation products were screened by UHPLC-Q-Orbitrap-HRMS, three candidates (X11719474, X11721061, and X11718922) were synthesized, and the photolysis and soil degradation kinetics were explored. The possible pathways were elucidated. Sulfoxaflor, X11718922, and X11721061 had a low toxicity, and X11719474 (48 h EC50 0.74 mg/L) had a high toxicity to Daphnia magna. Thus, sulfoxaflor and its degradation products could induce tissue damage in Daphnia magna. This work offers a theoretical basis for the application and ecological risk assessment of sulfoxaflor.

A Sensitive SERS Method for Determination of Pymetrozine in Apple and Cabbage Based on an Easily Prepared Substrate.

Residual pesticides are one of the major food safety concerns around the world. There is a demand for simple and reliable methods to monitor pesticide residues in foods. In this study, a sensitive method for determination of pymetrozine in apple and cabbage samples using surface-enhanced Raman spectroscopy (SERS) based on decanethiol functionalized silver nanoparticles was established. The proposed method performed satisfactorily with the linear detection range of 0.01-1.00 mg/L and limit of detection (LOD) of 0.01 mg/L in methanol. In addition, it was successfully used to detect pymetrozine in apple and cabbage samples, the LOD was 0.02 and 0.03 mg/L, respectively, and the recoveries of spiked cabbage and apple ranged 70.40-104.00%, with relative standard deviations below 12.18% and 10.33% for intra-day and inter-day tests. Moreover, the results of the correlation test with real cabbage samples of liquid chromatography-tandem mass spectrometry showed that they were highly correlated (slope = 0.9895, R2 = 0.9953). This study provides a sensitive approach for detection of pymetrozine in apple and cabbage, which has great potential for determination of pymetrozine residues in food products.

Bagging and non-bagging treatment on the dissipation and residue of four mixed application pesticides on banana fruit.

BACKGROUND: Bananas are vulnerable to disease and insect pests after producing fruit. In order to increase the yield and produce high-quality fruit, the insecticides and fungicides are mixed and applied 2-3 times on banana, then the fruit is bagged. Buprofezin, imidacloprid, difenoconazole, and pyraclostrobin are widely used on banana. However, there is a lack of research on the effect of fruit bagging on pesticide dissipation and residues on bananas. RESULTS: A versatile liquid chromatography-tandem mass spectrometry method with modified QuEChERS sample preparation has been developed for the determination of buprofezin, imidacloprid, difenoconazole, and pyraclostrobin in bananas. The recovery of four pesticides was satisfactory (74.96-98.63%) with reasonable relative standard deviation (≤ 8.78%). In Hainan and Guangzhou, the half-lives of the four pesticides were 4.68-13.9 and 5.63-20.4 days in non-bagged and bagged bananas, respectively. The significance analysis of the half-lives in the two sites showed that the dissipation rates of the three pesticides (imidacloprid, difenoconazole, pyraclostrobin) on whole bananas were significantly decreased by the effect of bagging (P < 0.05). However, there was no significant difference in the degradation of half-life of buprofezin under bagging and without bagging (P > 0.05). CONCLUSION: The high vapor pressure and the non-systemic property cause buprofezin to evaporate and dissipate the fastest among the four studied pesticides. The ultimate residues of four pesticides in bananas are lower than the maximum residue limits in China after three times of mixed applications under bagging or non-bagging. The results provide scientific data for evaluating the safety of four pesticides in banana bagging. © 2020 Society of Chemical Industry.

In situ and rapid determination of acetamiprid residue on cabbage leaf using surface-enhanced Raman scattering.

BACKGROUND: Pesticide residues in agricultural products and foods pose a serious threat to human health, and therefore a simple, rapid and direct method is urgently needed for pesticide residue detection. In addition to realizing the detection of acetamiprid in cabbage extract solution, the main target of this study was to establish an in situ surface-enhanced Raman scattering (SERS) method, which could directly detect acetamiprid residue on cabbage leaf without the need for extraction. Acetamiprid was first used to contaminate the surface of fresh cabbage leaf, and then bimetallic silver-coated gold nanoparticles (Au@AgNPs) were added on the contaminated spots and dried for SERS measurement. RESULTS: Results suggested that acetamiprid can be detected in cabbage extract and on cabbage leaf surface in situ using the SERS method based on the Au@AgNPs substrate. The limit of detection was 0.08 µg mL-1 in cabbage extract and 0.14 mg kg-1 on cabbage leaf, the recovery ranged from 80.5% to 105.5% and the relative standard deviation was in the range 4.37-10.63%. CONCLUSIONS: The proposed SERS method provides an in situ, nondestructive and rapid way to detect acetamiprid residue on the surface of fruits and vegetables, which could serve as an auxiliary approach for early screening of contaminated produce in field or on site in the future. © 2020 Society of Chemical Industry.

New Method for Accurate Determination of Polyphenol Oxidase Activity Based on Reduction in SERS Intensity of Catechol.

Rapid and accurate measurement of polyphenol oxidase (PPO) activity is important in the food industry as PPOs play a vital role in catalyzing enzymatic reactions. The aim of this study was to develop surface-enhanced Raman scattering (SERS) approach for accurate determination of PPO activity in fruit and vegetables using the reduction in SERS intensity of catechol in reaction medium. Within a certain catechol concentration, when a purified PPO solution was analyzed, the reduction in SERS intensity (Δ I) was linear to PPO activity ( Ec) in a wide range of 500-50 000 U/L, and a linear regression equation of log Δ I/Δ t = 0.6223 log Ec + 0.8072, with a correlation coefficient of 0.9689 and a limit of detection of 224.65 U/L, was obtained. The method was used for detecting PPO activity in apple and potato samples, and the results were compared with those obtained from colorimetric assay, which demonstrated that the proposed method could be successfully used for detecting PPO activity in food samples.

Simple Approach for the Rapid Detection of Alternariol in Pear Fruit by Surface-Enhanced Raman Scattering with Pyridine-Modified Silver Nanoparticles.

A simple method based on surface-enhanced Raman scattering (SERS) was developed for the rapid determination of alternariol (AOH) in pear fruits using an easily prepared silver-nanoparticle (AgNP) substrate. The AgNP substrate was modified by pyridine to circumvent the weak affinity of the AOH molecules to the silver surface and to improve the sensitivity of detection. Quantitative analysis was performed in AOH solutions at concentrations ranging from 3.16 to 316.0 µg/L, and the limit of detection was 1.30 µg/L. The novel method was also applied to the detection of AOH residues in pear fruits purchased from the market and in pear fruits that were artificially inoculated with Alternaria alternata. AOH was not found in any of the fresh fruit, whereas it resided in the rotten and inoculated fruits. Finally, the SERS method was cross validated against HPLC. It was revealed that the SERS method has great potential utility in the rapid detection of AOH in pear fruits and other agricultural products.

Regression Algorithms in Hyperspectral Data Analysis for Meat Quality Detection and Evaluation.

Hyperspectral imaging (HSI) system in tandem with chemometric methods is proposed as a rapid, efficient, cost-saving, and nondestructive detection technique, and multivariate data analysis is an indispensable part of this novel detection technique. In recent years, the rapid progress that we have made in using all kinds of chemometric methods to deal with hyperspectral data of meat products, however, cannot meet the practical needs very well. Thus, in order to give some suggestions on how to select an appropriate algorithm for hyperspectral data analysis, this review, first, briefly introduces the principle of the most widely used regression algorithms, and, more importantly, then focuses on the application of different algorithms in modeling the correlation between the quality attributes of the tested sample and their hyperspectral data. The advantages and limitations of these algorithms are compared and discussed. This review article will provide valuable guidelines for data analysis in the future progress of HSI detection technique.

Recent Developments in Methods and Techniques for Rapid Monitoring of Sugar Metabolism in Fruits.

The major sugars in fruits, including glucose, fructose, and sucrose, play a critical role in fruit quality control and maturity evaluation. Many novel methods and techniques such as enzymatic and nonenzymatic biosensors, nuclear magnetic resonance, and near-infrared spectroscopy have been developed to provide the rapid estimation of sugar inversion under different storage conditions. This review provides a description of recent advancements in these technologies for the determination of sugar contents in fruits. The prospects of emerging spectroscopic technologies such as Raman spectroscopy, hyperspectral imaging, and terahertz imaging, for assessing sugars in intact fruits are discussed. The challenges for further developments of these methods and technologies to meet the increasing demand for rapid and on-line quality control are also presented.

Synergetic degradation of konjac glucomannan by γ-ray irradiation and hydrogen peroxide.

Konjac glucomannan (KGM) samples were irradiated with (60)Co γ-rays with a radiation dose of 50kGy in the presence and absence of hydrogen peroxide. The average molecular weight (Mw) and polydispersity index (PDI) of untreated and degraded samples were measured by gel permeation chromatography (GPC), revealing that γ-rays and hydrogen peroxide had a synergetic effect on degradation. Structures of untreated and degraded products were characterized with ultraviolet-visible (UV) and Fourier-transform infrared (FT-IR) spectroscopies, and X-ray diffraction (XRD). Results showed that there was no significant change in the main chain of KGM following degradation, although the crystallinity of KGM decreased. A synergetic effect of γ-rays and hydrogen peroxide was also found in the structural characterization of KGM. The physical properties of KGM changed markedly following degradation, which may increase its application potential. The mechanism of degradation of KGM in the presence and absence of hydrogen peroxide was also investigated.

Study on preparation and separation of Konjac oligosaccharides.

To study the preparation and separation of Konjac oligosaccharides, Konjac Glucomannan was degraded by the combination of γ-irradiation and ß-mannanase, and then the degradation product was separated by ultrafiltration. To our interest, for most of Konjac oligosaccharides obtained by this method, the molecular mass was lower than 2200 Da. In addition, the 1000 Da molecular weight cut off membrane could effectively separate the Konjac oligosaccharides. In conclusion, the combination of γ-irradiation and ß-mannanase was an efficient method to obtain Konjac oligosaccharides, and the oligosaccharides of molecular mass lower than 1000 Da could be effectively separated by ultrafiltration.