Pengqiang Du

Rapid residue analysis of pyriproxyfen, avermectins and diflubenzuron in mushrooms by ultra-performance liquid chromatography coupled with tandem mass spectrometry

A quick, easy, cheap, effective, rugged, and safe (QuEChERS) analytical procedure for the simultaneous determination of pyriproxyfen, diflubenzuron and avermectin residues in mushrooms and their substrates was developed using ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS). Pyriproxyfen, diflubenzuron and avermectin were extracted with acetonitrile and the purification procedure was carried out using primary-secondary amine (PSA). The determination of target compounds was achieved in less than 3.0 min using an electrospray ionization source in positive mode (ESI+). Chromatographic separation was achieved using gradient elution with a mobile phase consisting of acetonitrile and water containing 0.2% formic acid. Average recoveries were in the range of 78.1–112.5% with the relative standard deviation values below 11.8% for all analytes. The limits of detection ranged from 0.016 to 1.5 μg kg−1, and limits of quantification ranged from 0.052 to 5 μg kg−1. The results of the method validation confirmed that this proposed method is convenient and reliable for the determination of pyriproxyfen, diflubenzuron and avermectin residues in mushrooms and their substrates.

Residue analysis and persistence evaluation of fipronil and its metabolites in cotton using high-performance liquid chromatography-tandem mass spectrometry

A simple residue analytical method based on the QuEChERS approach and high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) detection was developed for the analysis of fipronil and its three metabolites in cottonseed, cotton plant and soil. The average recoveries of four test compounds from all three matrices were 78.6–108.9% at the level of 0.005 to 0.5 mg/kg, with an RSD in the range of 0.6 to 13.7%. The limit of quantification (LOQ) of the four test compounds ranged from 0.005 to 0.01 mg/kg. The results of the residual dynamics experiments showed that fipronil dissipated rapidly in cotton plants and soil and that oxidation and photolysis were the main degradation pathways. Moreover, the bi-exponential models demonstrated a good fit of the measured data for fipronil in cotton plants and soil, with R2 in the range of 0.8989 to 0.9989. Furthermore, a total of 40 samples of cottonseed from Shandong Province were analyzed, and all of the samples were free from the four test compound residues.

Determination and dissipation of mesotrione and its metabolites in rice using UPLC and triple-quadrupole tandem mass spectrometry

In this study, an efficient and fast method for the determination of the herbicide mesotrione and its two metabolites [4-methylsulfonyl-2-nitrobenzoic acid (MNBA) and 2-amino-4-methylsulfonylbenzoic acid (AMBA)] in rice, rice plants, rice hulls, water, and soil was developed, using ultra performance liquid chromatography coupled with tandem quadrupole (Xevo TQ-S) mass spectrometry (UPLC-Xevo TQ-S-MS/MS). The recoveries of the compounds were 68.6%-108.4% at different levels. The intra-day relative standard deviation (RSD) ranged from 2.0% to 14.4%, and the inter-day RSD, from 1.9% to 11.4%. The limits of quantification (LOQ) were ranged from 0.146 to 4.545μgkg-1for mesotrione, MNBA and AMBA. Dissipation and residual assays with the commercial formulation were conducted at three locations. The dissipation rates of the compounds were fast in rice plants, soil, and water, and residues at harvest were not detected in any of the three localities.

Residue behaviour of six pesticides in button crimini during home canning

The effect of home canning (including washing, boiling, cooling, adding solution and sterilisation) on residue levels of imidacloprid, diflubenzuron, abamectin, pyriproxyfen and β-cypermethrin and chlorothalonilin on button crimini was assessed. Residues of imidacloprid, diflubenzuron, abamectin and pyriproxyfen were measured by UPLC-MS/MS; the residues of β-cypermethrin and chlorothalonil were measured by GC. Results showed that washing resulted in a 3.8% reduction of the initial residue level of imidacloprid (p ≤ 0.05). From washing to sterilisation the processing effect was significant compared with raw crimini (p ≤ 0.05), but processing through cooling and adding solution had no effect. For diflubenzuron, from raw crimini to sterilisation the processing effect was significant by comparison with the initial level (p ≤ 0.05); the processing effect was not obvious between two sequential steps, and the sequential steps have list: washing and boiling, boiling and cooling, boiling and adding of solution, cooling and adding solution. The changes in abamectin levels were also significant from raw crimini to sterilisation compared with raw crimini (p ≤ 0.05), but the changes were not obvious from boiling to adding solution and amongst them. For pyriproxyfen, washing resulted in a 39% reduction, but changes were not obvious from washing to sterilisation, p ≤ 0.05 between two consecutive steps. The whole procedure could significantly decrease residues of β-cypermethrin (p ≤ 0.05); washing could significantly reduce residues of β-cypermethrin; the effects of last procedures were complicated, and p ≤ 0.05 between two consecutive steps. Washing resulted in an 80% reduction of chlorothalonil; after washing there were no detectable residues. After the whole process, the processing factors for imidacloprid, diflubenzuron, abamectin, pyriproxyfen, β-cypermethrin and chlorothalonil were 0.40, 0.22, 0.04, 0.85, 0.28 and 0, respectively.

Simultaneous determination of three pesticides and their metabolites in unprocessed foods using ultraperformance liquid chromatography-tandem mass spectrometry

ABSTRACT We have developed a rapid, multi-compound analytical method for measuring residues of the pesticides thiamethoxam and its metabolite, clothianidin; fipronil and its three metabolites, fipronil sulfone, fipronil sulfide, and fipronil desulfinyl; and pyraclostrobin in unprocessed foods (rice, corn, cucumbers, tomatoes, apples, and bananas) by ultra-performance liquid chromatography coupled to tandem mass spectrometry. Acetonitrile was used as the extraction solvent, and an octadecylsilane-dispersive SPE was used to clean up the analytes, which were then separated through a UPLC HSS T3 column connected to a tandem mass spectrometer via an electrospray ionisation source. The linearity of this method for the target analytes was excellent (R2 ≥0.990) in the concentration range of 5–1000 μg kg–1. The average recoveries of the seven compounds at concentrations of 10, 100, and 1000 μg kg–1 from six spiked matrix samples ranged from 73.6 to 110.6%, all with RSD values of ≤19.7%. The limit of quantification was 10 μg kg–1. The method validated the effectiveness of the method for routine monitoring the residue of these pesticides and their metabolites in foods.

Clomazone influence soil microbial community and soil nitrogen cycling

We designed an indoor mesocosm experiment to investigate the long-term effects of exposure to clomazone, a widely used herbicide, on soil microbial communities and their nitrogen (N) cycling functions. Clomazone was applied to two typical soils from China at three concentrations: 0.8 (the recommended dosage), 8 and 80 mg kg-1 soil dry weight, and the mix was incubated for 90 days. Samples were removed periodically for assay with several techniques. The half-lives of clomazone in this experiment were 11-126 d. Results were significant only for the highest clomazone concentration. Next-generation sequencing of the 16S and 18S rDNA genes revealed that bacterial diversity significantly decreased whereas fungal abundance increased after day 60 but with no detectable effect on the microbial community. Hierarchical cluster and principal coordinates analysis revealed that the bacterial community structure was negatively impacted. Linear discriminant analysis of effect size identified Sphingomonas and Arthrobacter as the predominant bacterial species. Finally, we measured soil NH4+ and NO3- concentrations and used real-time PCR to analyze the abundance of the N-cycling genes, nifH and amoA. In the first 30 days, the NO3--N content and the number of ammonia-oxidizing bacteria increased. N2-fixing bacteria were inhibited after 60 days, but the NH4+-N concentration remained unchanged and was likely provided by ammoniation.

Effects of trifluralin on the soil microbial community and functional groups involved in nitrogen cycling

Large amounts of trifluralin are applied each year for weed control; however, its effects on soil microbial communities and functions are unknown. Two agricultural soils, one silty loam and one silty clay were spiked with TFL (0, 0.84, 8.4, and 84 mg kg-1) and studied the effects using a laboratory microcosm approach. The half-lives were 44.19-61.83 d in all cases. Bacterial abundance increased 1.12-5.56 times by TFL, but the diversity decreased. From the next-generation sequencing results, TFL altered the bacterial community structure, which initially diverged from the control community structure, then recovered, and then diverged again. Linear discriminant analysis effect size indicated that Sphingomonas and Xanthomonadaceae were the predominant species on day 7 and 15 in TFL treatments. N2-fixing bacteria were initially increased, then decreased, and then recovered, and it was positively correlated with NH4+-N content. Compared with the control, ammonia-oxidizing bacteria were decreased by 25.51-92.63%, ammonia-oxidizing archaea were decreased by 17.12-85.21% (except day 7), and the NO3--N concentration was also inhibited. In contrast to bacteria, fungal abundance was inhibited without any observable effects on fungal diversity or community structure. These results suggest that TFL impacts soil bacterial community and alters functional microorganisms involved in soil N processing.

Impact of fomesafen on the soil microbial communities in soybean fields in Northeastern China

Fomesafen, a widely adopted residual herbicide, is used throughout the soybean region of northern China for the spring planting. However, the ecological risks of using fomesafen in soil remain unknown. The aim of this work was to evaluate the impact of fomesafen on the microbial community structure of soil using laboratory and field experiments. Under laboratory conditions, the application of fomesafen at concentrations of 3.75 and 37.5mg/kg decreased the basal respiration (RB) and microbial biomass carbon (MBC). In contrast, treatment with 375mg/kg of fomesafen resulted in a significant decrease in the RB, MBC, abundance of both Gram+ and Gram- bacteria, and fungal biomass. Analysis of variance showed that the treatment accounted for most of the variance (38.3%) observed in the soil microbial communities. Furthermore, the field experiment showed that long-term fomesafen application in continuously cropped soybean fields affected the soil bacterial community composition by increasing the relative average abundance of Proteobacteria and Actinobacteria species and decreasing the abundance of Verrucomicrobia species. In addition, Acidobacteria and Chloroflexi species showed a pattern of activation-inhibition. Taken together, our results suggest that the application of fomesafen can affect the community structure of soil bacteria in the spring planting soybean region of northern China.

Evaluation of the safe use and dietary risk of beta -cypermethrin, pyriproxyfen, avermectin, diflubenzuron and chlorothalonil in button mushroom

In this study, the residues of beta-cypermethrin, pyriproxyfen, avermectin, diflubenzuron and chlorothalonil in button mushrooms were investigated. The dietary risks of ingesting button mushrooms that have had these pesticides applied by two different methods under normal plant conditions were evaluated. The dissipation of these pesticides into the soil was also studied. According to the maximum residue limits (MRLs) and acceptable daily intakes (ADIs), the final residues of beta-cypermethrin, pyriproxyfen, avermectin, diflubenzuron, and chlorothalonil were safe for human consumption after these pesticides were applied by spraying 2 times at the dosages of 900, 750, 540, 562.5, and 540 g a.i.ha−1. The dissipation experiment results demonstrated that these pesticides dissipated rapidly after spraying, and there were no residues that could be detected at harvest time when the pesticides were mixed with substrates. According to this work, the application methods of spraying and incorporation with these pesticides at 1 and 1.5 times of the recommended dosage are safe and proper in cultivating button mushrooms.