Determinations of dinotefuran and metabolite levels before and after household coffee processing in coffee beans using solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry.

BACKGROUND: Coffee is one of the most popular beverages in the world. However, as daily consumables, coffee beans may contain pesticide residues that are capable of causing adverse health effects. Thus, we investigated residue dynamics in coffee beans using supervised field trials under Good Agricultural Practice conditions and determined the effects of household coffee processing on the coffee-bean pesticide residues dinotefuran and its metabolites 1-methyl-3-(tetrahydro-3-furylmethyl) urea (UF) and 1-methyl-3-(tetrahydro-3-furylmethyl) guanidine (DN). RESULTS: The recovery rate of dinotefuran and its metabolites UF and DN was in the range 73.5%-106.3%, with a relative SD < 10%. The limits of detection and limits of quantification for dinotefuran, UF and DN were all 0.003 and 0.01 mg kg-1 , respectively. Dissipation experiments were conducted over 2015 and 2016 and showed a mean half-life of 40.8 days. Coffee processing procedures were performed as described for traditional household coffee processing in Ethiopia. Dinotefuran contents were reduced by 44.4%-86.7% with washing of coffee beans and the roasting process reduced these contents by 62.2%-100%. DN residues were not detected in roasted coffee beans before day 21 or in brewed coffee before day 35 and UF residues were not detected in brewed coffee before day 35. Kruskal-Wallis analyses indicated large variations in the stability of pesticide residues between processing methods (P ≤ 0.05). Reductions of pesticide concentrations with washing were also significantly lower than those following roasting (P = 0.0001) and brewing processes (P = 0.002). Moreover, processing factors were less than one for all processing stages, indicating reductions of pesticides contents for all processing stages. CONCLUSION: The cumulative effects of the three processing methods are of paramount importance with respect to an evaluation of the risks associated with the ingestion of pesticide residues, particularly those in coffee beans. © 2018 Society of Chemical Industry.

Application of the combination index (CI)-isobologram equation to research the toxicological interactions of clothianidin, thiamethoxam, and dinotefuran in honeybee, Apis mellifera.

Due to complex pest control scenarios and the needs of agricultural production, different neonicotinoids may be used in certain agricultural applications. Consequently, honeybees may be exposed to these substances through distribution throughout plant tissues via the vascular system through several pathways, such as surface water, the exudates excreted from plants, and air pollution via drift of dust as well as contaminated pollen and nectar. In the current study, the single and combined toxicity of clothianidin, dinotefuran, and thiamethoxam to honeybees was examined after 48 h exposure by the acute oral method and combination index (CI)-isobologram equation. At the 48 h interval, our results showed that 1) the order of toxicities for the single insecticides was ranked as clothianidin > thiamethoxam > dinotefuran and that 2) all binary and ternary combinations showed synergism or additive effect at the effect (fa) 0.5. Therefore, our results not only provided meaningful guidelines in evaluating the safety risk of the mixtures of the three neonicotinoids towards honeybees but also suggested that there is a significant interest in the study of mixture toxicities of neonicotinoids against honeybees because risk assessment of neonicotinoids against honeybees conducted only in individual insecticides may underestimate the realistic toxicity.

Multiresidue Method for Determination of 183 Pesticide Residues in Leeks by Rapid Multiplug Filtration Cleanup and Gas Chromatography-Tandem Mass Spectrometry.

This study reports the development of a novel multiplug filtration cleanup (m-PFC) procedure for analysis of pesticide residues in leek samples followed by gas chromatography-tandem mass spectrometry detection. The leek samples were initially purified following the dispersive solid-phase extraction with different sorbents to determine the most suitable proportioning of sorbent materials; then, the m-PFC method was carried out by applying the streamlined procedure with syringes. Average recoveries of most pesticides were in the range from 70.2 to 126.0% with the relative standard deviation < 20% with the m-PFC process. The limits of detection were 0.03-3.3 µg kg(-1). The limits of quantification were 0.1-10 µg kg(-1). The m-PFC process is convenient and time-efficient, taking just a few seconds per sample. Finally, the developed method was successfully applied to the determination of pesticide residues in market samples. In that analysis, 35 pesticides were detected in 29 samples, with values ranging from 2.0 to 9353.1 µg kg(-1).

Simultaneous determination of 70 pesticide residues in leek, leaf lettuce and garland chrysanthemum using modified QuEChERS method with multi-walled carbon nanotubes as reversed-dispersive solid-phase extraction materials.

Leek, leaf lettuce and garland chrysanthemum are troublesome vegetables containing large amount of pigments which may bring serious matrix interferences in mass spectrometry analysis. Multi-walled carbon nanotubes (MWCNTs) have a good effect for the cleanup of troublesome matrix. So the study was designed to develop a multi-residue method for the determination of 70 pesticide residues in leek, leaf lettuce and garland chrysanthemum based on a modified QuEChERS procedure using MWCNTs as reversed-dispersive solid phase extraction (r-DSPE) materials to remove the interferences of pigments. PSA and GCB were used as comparison. LC-MS/MS was used to identify and quantify the residue levels of multi-pesticides. The clean-up performance of MWCNTs was demonstrated to be obviously superior to GCB and PSA. This method was validated on leek, leaf lettuce and garland chrysanthemum spiked at the concentration of 10, 50 and 100µgkg(-1) with five replicates. The recoveries of 70 pesticides ranged from 74% to 119%, with relative standard deviations (RSDs) lower than 14.2%. Good linearity (R(2)≥0.9903) was obtained at the range of 10-1000µg/L for all pesticides in the selected matrices. The limit of quantification (LOQs) and limit of detection (LODs) of the 70 pesticides for the selected matrices ranged from 0.3 to 7.9µgkg(-1) and from 0.1 to 2.4µgkg(-1) respectively. The method was successfully applied to the routine monitoring of pesticide residues in market samples.

Dissipation and residue behavior of mepiquat on wheat and potato field application.

A modified LC-MS method for the analysis of mepiquat residue in wheat, potato, and soil was developed and validated. A hydrophilic interaction liquid chromatographic column has been successfully used to retain and separate the mepiquat. Mepiquat residue dynamics and final residues in supervised field trials at Good Agricultural Practice (GAP) conditions in wheat, potato, and soil were studied. The limits of quantification for mepiquat in all samples were all 0.007 mg kg(-1), which were lower than their maximum residue limits. At fortification levels of 0.04, 0.2, and 2 mg kg(-1) in all samples, recoveries ranged from 77.5 to 116.4% with relative standard deviations of 0.4-7.9% (n = 5). The dissipation half-lives (T 1/2) of mepiquat in soil (wheat), wheat plants, soil (potato), and potato plants were 4.5-6.3, 3.0-5.6, 2.2-4.6, and 2.4-3.2 days, respectively. The final residues of mepiquat were below 0.153 mg kg(-1) in soil (wheat), 0.052-1.900 mg kg(-1) in wheat, below 0.072 mg kg(-1) in soil (potato), and below 1.173 mg kg(-1) in potato at harvest time. Moreover, pesticide risk assessment for all the detected residues was conducted. A maximum 0.0012% of acceptable daily intake (150 mg kg(-1)) for national estimated daily intake indicated low dietary risk of these products.

Residue dynamics of procymidone in leeks and soil in greenhouses by smoke generator application.

A modified QuEChERS-GC-MS method for analysis of procymidone residue in leeks and soil was developed and validated. Procymidone residue dynamics and residues in supervised field trials at GAP conditions in leeks and soil in greenhouses were studied. Leek samples were treated under microwave radiation for 1min before homogenization, followed by extracting with acetonitrile and clean-up with reverse solid phase dispersion by primary and secondary amine (PSA). Procymidone residue was determined by GC-MS in selected ion monitoring (SIM) mode. At fortification levels of 0.02, 0.2 and 2mg/kg in leeks and soil, it was shown that recoveries ranged from 74.9% to 100.8% with relative standard deviations of 1.3-8.5%. At four geographical experimental plots, procymidone residue in leeks and soil showed a relatively fast dissipation rate, with half-lives of 4.52-8.76 days for leeks and 3.76-5.65 days for soil. At pre-harvest intervals of 21-30 days, procymidone residue ranged from 0.033 to 0.17mg/kg in leeks, and 0.020-1.75mg/kg in soil. Residues persistence varied in leeks and soil in four field trials, suggesting that it might be affected by some physical and chemical factors, growth dilution factor, soil characteristics and microorganisms.

PTEN-5-HT2C coupling: a new target for treating drug addiction.

It is well known that the ventral tegmental area (VTA) is a brain region in which virtually all abused drugs exert rewarding effects by activating its dopamine neurons. We recently found that the tumour suppressor enzyme phosphatase and tensin homologue deleted on chromosome 10 (PTEN) directly interacts to a region in the third intracellular loop (3L4F) of serotonin 5-HT2C receptors (5-HT2cR) in the rat VTA. PTEN limits agonist-induced 5-HT2cR phosphorylation via its protein phosphatase activity. Systemic or intra-amygdaloid application of the interfering peptide Tat-3L4F is able to disrupt PTEN coupling with 5-HT2cR in the rat VTA, resulting both in a suppression of the increased firing rate of VTA dopaminergic neurons induced by Delta 9-tetrahydrocannabinol (THC), the psychoactive ingredient of marijuana, and in a blockade of the conditioned place preference induced by THC and nicotine [Ji, S.P. et al. (2006). Nat. Med., 12: 324-329]. Because the blockade effects of Tat-3L4F peptide on the conditioned preference could be achieved by the suppression of Tat-3L4F peptide on the rewarding and/or learning/memory mechanisms associated with conditioned place preference, we recently explored whether Tat-3L4F can affect learning and memory. We observed that Tat-3L4F did not produce significant effects on spatial learning and memory in a Morris water maze test, thus indicating that Tat-3L4F can effectively suppress the rewarding effects induced by drugs of abuse.