Residual determination of pyrethrins in Lycium barbarum (goji) by GC-MS/MS and a dietary risk assessment of Chinese goji consumption.

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.

Determination, residue and risk assessment of trifloxystrobin, trifloxystrobin acid and tebuconazole in Chinese rice consumption.

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.

Determination, residue analysis, risk assessment and processing factors of tebufenozide in okra fruits under field conditions.

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.

A liquid chromatography-tandem mass spectrometry method to simultaneously determinate dichlorvos and phoxim in tobacco.

A simple pretreatment method with liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed and validated to simultaneously determine dichlorvos and phoxim in tobacco and soil matrices. Satisfactory linearity (R2 ≥ 0.9991) of the method was obtained for both analytes. The limits of detection and limits of quantification for dichlorvos and phoxim in three matrices were 0.0015-0.006 and 0.005-0.02 mg/kg, respectively. Average recoveries were 78.24-92.21% for dichlorvos and 76.62-100.51% for phoxim in soil, green tobacco leaves and cured tobacco leaves. The intra- and inter-day relative standard deviations were <6%. The established method was successfully applied for the residual analysis of dichlorvos and phoxim in real soil and tobacco samples. The results indicated that the established method could be used to detect trace amounts of dichlorvos and phoxim in tobacco. The data could also help the Chinese government establish maximum residue limits of dichlorvos and phoxim on tobacco and establish proper and safe use of dichlorvos and phoxim on tobacco plants in China.

A liquid chromatography with tandem mass spectrometry method to simultaneously determinate chlorpyrifos, imidacloprid and imidacloprid metabolites in wheat.

A liquid chromatography with tandem mass spectrometry method was developed and validated to simultaneously determine chlorpyrifos, imidacloprid, and imidacloprid metabolites in soil, wheat grain, and wheat straw matrices. Satisfactory linearity (R2 ≥ 0.9965) of the method was obtained for all analytes. The ranges of limits of detection and limits of quantification for seven analytes in three matrices were 0.17-66.7 and 0.5-200 µg/kg, respectively. Average recoveries were 72.85-81.25% for chlorpyrifos, 78.54-84.70% for imidacloprid, 73.83-81.03% for imidacloprid olefin, 71.47-80.61% for 5-hydroxy imidacloprid, 71.79-81.32% for imidacloprid urea, 70.42-82.20% for imidacloprid nitroguanidine, and 70.91-82.46% for imidacloprid 6-chloronicotinic acid in soil, wheat grain, and wheat straw. The intra- and interday relative standard deviations were less than 8%. The established method was successfully applied for the residual analysis of chlorpyrifos, imidacloprid, and imidacloprid metabolites in actual soil, wheat grain, and wheat straw samples. The results indicated that the established method could be used to detect trace amounts of chlorpyrifos, imidacloprid, and imidacloprid metabolites in wheat and that the method might be able to provide some data on the detection of these seven compounds in other crops.

Simultaneous determination and risk assessment of metalaxyl and azoxystrobin in potato by liquid chromatography with tandem mass spectrometry.

A liquid chromatography with tandem mass spectrometry method was developed and validated to simultaneously determine metalaxyl and azoxystrobin in soil, potato, and potato foliage samples. The samples were extracted by 20 mL of acetonitrile and purified with dispersive solid-phase extraction using octadecyl silane as sorbent. The method showed good linearity (determination coefficients ≥ 0.9926) for metalaxyl (2.5-500 ng/mL) and azoxystrobin (5-1000 ng/mL). The limits of detection and quantification for both fungicides were 1.5-20 µg/kg. The average recoveries in soil, potato, and potato foliage were 83.07-92.87% for metalaxyl and 82.71-98.53% for azoxystrobin. The intra- and inter-day relative standard deviations were all less than 9%. The method was successfully applied on the residual analysis of metalaxyl and azoxystrobin in field trial samples. The results showed that the concentrations of metalaxyl and azoxystrobin in potato samples collected from Guizhou and Hunan were below 50 and 100 µg/kg (maximum residue limit set by China), respectively, at 5 days after the last application. When following the recommended application manual, metalaxyl and azoxystrobin do not present health concerns to the population because the risk quotients are far below 100%. All the above data could help and promote the safe and proper use of metalaxyl and azoxystrobin in potato.