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A simple and sensitive liquid chromatography-tandem mass spectrometry method was developed for the determination of thidiazuron (TDZ), a plant growth regulator, in soil, tobacco leaf (fresh, cured), stem, and root. The detection limits of TDZ ranged from 0.03 μg/kg to 0.15 μg/kg, and the limits of quantification ranged from 0.1 − 0.5 μg/kg. The average recoveries of TDZ in soil, tobacco leaf (fresh, cured), stem, and root were between 75.39% and 98.51% with intra-day relative standard deviations (RSDs) between 1.06% and 4.91% and inter-day RSDs between 1.49% and 7.52%. The valid method was used to determine the amount of TDZ residues in tobacco and soil samples under open field and laboratory conditions. Field experiments were carried out in six agricultural sites of China, and the results showed that the half-lives of TDZ were 9.76 − 12.60 days and 2.04 − 4.81 days in soil and fresh tobacco leaves, respectively. The terminal concentration of TDZ in cured tobacco leaves was <0.50−7.46 μg/kg. Foliage spray and root irrigation experiments were conducted under laboratory conditions. The results indicated that TDZ can be transferred upward and downward in tobacco plants. The transfer factor (TF) of the root irrigation was approximately 10 times of TF of the foliage spray. [ABSTRACT FROM AUTHOR]

A quick, easy, cheap, effective, rugged and safe liquid chromatography-tandem mass spectrometry technology was used to determine benziothiazolinone in citrus. Orthogonal test and single-factor analysis were conducted to identify the optimal extraction method of benziothiazolinone. The good linearity (R2 > 0.9949), high accuracy and precision, matrix effect and satisfactory recoveries (79.31%–98.68%) at three spiked levels (0.02, 0.2 and 2 mg/kg) with low relative standard deviation values (0.63%–8.68%) were validated. The limits of detection and quantification were within 0.2–0.8 and 20 μg/kg, respectively. This study could provide guidance for the reasonable use of this fungicide and for the establishment of maximum residue level. [ABSTRACT FROM AUTHOR]

An accurate and simple analytical approach for the determination of residues cinerin I, cinerin II, jasmolin I, jasmolin II, pyrethrin I and pyrethrin II (six active ingredients of pyrethrins) in fresh and dried goji berries was developed and validated for analysis by gas chromatography with tandem mass spectrometry. Good linearity (determination coefficient >0.99), accuracy (average recoveries of 88.3%–111.5%) and precision (intra- and inter-day relative standard deviations of 0.4%–8.3%) were obtained with the optimised determination method. The LODs and LOQs of the six analytes in two goji matrices were 0.24–2.1 µg/kg and 0.8–7 µg/kg, respectively. In a field trial, the terminal residual levels of pyrethrins (the sum of the concentrations of the six target analytes) in fresh and dried goji berry samples were <20–304 µg/kg at harvest, which could provide some information for the establishment of a maximum residue limit of pyrethrins on goji berries in China. Moreover, the risk assessment results indicated that because the risk quotient values were ≪100%, the potential dietary risk of pyrethrins on goji berries could be negligible for Chinese consumers. These detection and field results could provide some supporting data for the determination of pyrethrin residues in other crops and the proper application and safety assessment of pyrethrins in goji plants. [ABSTRACT FROM AUTHOR]

BACKGROUND: Ensuring the yield, quality, and profitability of okra by preventing and controlling pests with the application of insecticides has increased in the last decade. Some insecticide residues might remain in edible parts of okra (fruits) and lead to several potential human health problems. Therefore, research on the residue behaviour, risk assessment and removal approach of insecticides on okra fruits is important for food safety, together with the proper application and residual elimination of insecticides in okra. RESULTS: A simple liquid chromatography with tandem mass spectrometry (LC–MS/MS) method was established and validated for determining the tebufenozide residues in okra fruits. The recoveries of tebufenozide in okra fruits were >72% with relative standard deviations of 0.6 to 6.1%. The dissipation rates of tebufenozide were different in okra fruits cultivated under open land and glasshouse field conditions because of the discriminating humidity and temperature conditions. The dietary intake of the tebufenozide residues from okra fruit consumption for Chinese consumers was fairly low, with approximately no potential health risk. The processing factor values of washing, blanching, washing + blanching and soaking were all less than one, which indicated that these processes could effectively reduce the residual hydrazide in the okra fruit. CONCLUSION: The developed method for analysing tebufenozide in okra fruits was applicable for field studies on this insecticide. The potential health risk of tebufenozide in okra fruits could be negligible to the health of different age groups of Chinese consumers. The soaking process effectively removed tebufenozide residues from okra fruits. The obtained data will help Chinese governments establish a maximum residue limit of tebufenozide in okra and provide data for the risk assessment and removal of tebufenozide in other crops. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: In this study, a modified quick, easy, cheap, effective, rugged and safe method coupled with gas chromatography with electron capture detection was established to determine dimethachlon residues in paddy soil, rice husk, rice straw, brown rice and cooked rice. The limits of quantification of dimethachlon were 0.01 mg/kg for paddy soil, brown rice and cooked rice and 0.02 mg/kg for rice straw and rice husk. The mean recoveries were in the range 78.59–104.7% with relative standard deviation values of <10% for dimethachlon in the five matrices. For field experiments, the final residues of dimethachlon in paddy soil were < 0.05 mg/kg and were < 1.21 mg/kg in rice straw from six sites. The final residues of dimethachlon in the brown rice at 21, 28 and 35 days after spraying from six sites were 0.08–7.58 mg/kg, and 0.16–30.1 mg/kg in rice husk. Our six test sites covered the main rice–producing areas of China. The routine rice cooking process of a Chinese family could apparently increase the removal of dimethachlon in rice compared with brown rice, and the reduction ratios were > 96%. [ABSTRACT FROM AUTHOR]

Dufulin (DFL) is a potent, new-generation agrochemical that protects crops, such as tobacco, from viruses. Herein, for the first time, we developed a sensitive and specific polyclonal antibody-based indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) to detect DFL residues in samples. The assay showed high sensitivity and specificity to DFL, with a half maximal inhibitory concentration (IC50) of 48.5 ng ml−1 and limit of detection (IC20) of 2.5 ng ml−1. The average recovery of DFL in different spiked samples, such as tobacco, rice, tomato, cucumber, soil and water, was in the range of 70.7–138.8%. A statistically significant correlation was observed between our developed ELISA and previously established methodology of high-performance liquid chromatography with a diode array detector. These results indicate our assay is a potentially useful analytical tool for rapid detection of DFL residue in actual samples. [ABSTRACT FROM AUTHOR]

Two independent field trials were performed in Guizhou and Hunan, China in 2013 to investigate the dissipation and residue levels of saisentong in tobacco and soil. A novel and accurate method using high-performance liquid chromatography with diode array detection was developed and validated to determine saisentong levels in tobacco and soil. The average recovery of saisentong at fortification levels of 0.5, 2.5, 5.0 and 50.0 mg kg−1in fresh tobacco ranged from 75.92 to 107.40% with a relative standard deviation (RSD) of 0.94 to 7.55%, that at fortification levels of 0.5, 2.0 and 5.0 mg kg−1in tobacco powder ranged from 74.96 to 94.43% with a relative standard deviation (RSD) of 4.38 to 8.14%, and that at fortification levels of 0.1, 0.5 and 5.0 mg kg−1in soil ranged from 86.90 to 100.0% with an RSD of 1.38 to 4.62%. The limit of detection (LOD) of saisentong was 0.15 mg•kg−1in tobacco and 0.03 mg kg−1in soil, and the limit of quantification (LOQ) was 0.5 mg kg−1in tobacco and 0.1 mg kg−1in soil, respectively. For field experiments, the half-lives of saisentong in tobacco from Guizhou and Hunan were 5.9 and 1.6 days, respectively; those in soil were 14.7 and 12.0 days, respectively. The results suggest that the saisentong dissipation curves followed the first-order kinetic. The terminal residues of saisengtong in tobacco ranged from 0.5 to 9.39 mg kg−1at pre-harvest intervals (PHI) of 7, 14 and 21 days. [ABSTRACT FROM AUTHOR]

The fate of kresoxim-methyl was studied in a tobacco field ecosystem, and a simple and reliable method was developed for the determination of kresoxim-methyl in soil, green and cured tobacco leaves. Kresoxim-methyl residues were extracted from samples with petroleum ether, and determined by gas chromatography (GC) coupled with an electron capture detector (ECD). Kresoxim-methyl (30% suspension concentration) was applied at 150 g a.i. ha–1(the recommended high dosage) and 225 g a.i. ha–1(1.5 times the recommended high dosage) in the experimental fields in Huishui and Changsha in China. The limits of detection (LODs) and limits of quantification (LOQs) of kresoxim-methyl in green tobacco leaves, cured tobacco leaves and soil were 0.012 and 0.04 mg kg–1, 0.12 and 0.4 mg kg–1, and 0.0015 and 0.005 mg kg–1, respectively. The average recoveries were 84.5% to 95.7%, 79.8% to 94.3% and 83.3% to 93.8% with relative standard deviations (RSDs) less than 10% in green tobacco leaves at four spiked levels (0.04, 0.2, 2 and 8 mg kg–1), cured tobacco leaves at three spiked levels (0.4, 1 and 10 mg kg–1) and soil at three spiked levels (0.005, 0.05 and 0.5 mg kg–1), respectively. The results showed that the half-lives of kresoxim-methyl in green tobacco leaves and soil were 1.2–5.3 days and 6.7–10.4 days, respectively. At harvest, kresoxim-methyl residues in cured tobacco leaves samples collected 21 days after the last application at the recommended dosage were below 1.0 mg kg–1. These results could help establish appropriate application frequency and harvest intervals in the use of kresoxim-methyl on tobacco plants. [ABSTRACT FROM PUBLISHER]

A sensitive and selective analytical method for dufulin detection was developed using ultra-performance liquid chromatography coupled with photo-diode array detection (UPLC-PDA). Dufulin analysis was carried out with 1 μl sample injection on BEH C18 column (50.0 mm × 2.1 mm i. d., 1.7 μm film thickness) thermostatted at 40°C with a mobile phase of methanol/water (58/42 by volume) at flow rate of 0.3 ml min−1. Dissipation rates of dufulin in paddy plant, soil, water, and brown rice in three districts in China were studied using the method developed. Dufulin (30% WP) was applied at two dosages, 337.50 g a. i. ha−1(recommended dosage) and 506.25 g a. i. ha−1(1.5 times the recommended dosage) in experimental fields in Guizhou, Anhui, and Tianjin provinces in China. The limit of detection (LOD) and the limit of quantification (LOQ) of dufulin were 2.5 and 7.5 μg kg−1, respectively. The average recoveries were 72.76–95.43, 97.84–101.7, 96.99–100.8, and 80.91–100.5% in paddy plant at four spiking levels (0.04, 0.20, 2.0, 50.4 mg kg−1), in water at three spiked levels (0.0025, 0.025, 0.25 mg l−1), in soil at three spiking levels (0.04, 0.13, 1.3 mg kg−1), and in brown rice at four spiking levels (0.05, 0.20, 2.0, 10.0 mg kg−1), respectively. Our results showed that half-lives of dufulin in paddy plant and water in the three districts were 7.7–11.3 and 2.1–4.8 days, respectively. At harvest, dufulin residues in brown rice samples collected 35 days after the last dufulin application at the recommended dosage were below 0.5 mg kg−1. Our results provided data to help establish appropriate application frequency and harvest intervals in the use of dufulin for rice pest control in China. [ABSTRACT FROM AUTHOR]

A simple and rapid analytical method for the detection of trifloxystrobin, trifloxystrobin acid and tebuconazole in soil, brown rice, paddy plants and rice hulls was established and validated by liquid chromatography with tandem mass spectrometry. Acceptable linearity (R2 > 0.99), accuracy (average recoveries of 74.3–108.5%) and precision (intra‐ and inter‐day relative standard deviations of 0.9–8.8%) were obtained using the developed determination approach. In the field trial, the half‐lives of trifloxystrobin and tebuconazole in paddy plants were 5.7–8.3 days in three locations throughout China, and the terminal residue concentrations of trifloxystrobin and tebuconazole were <100 and 500 μg/kg (maximum residue limits set by China), respectively, at harvest, which indicated that, based on the recommended application procedure, trifloxystrobin and tebuconazole are safe for use on rice. The risk assessment results demonstrated that, owing to risk quotient values of both fungicides being <100%, the potential risk of trifloxystrobin and tebuconazole on rice was acceptable for Chinese consumers. These data could provide supporting information for the proper use and safety evaluation of trifloxystrobin and tebuconazole in rice. [ABSTRACT FROM AUTHOR]