Dissipation behaviour and dietary risk assessment of boscalid, triflumizole and its metabolite (FM-6-1) in open-field cucumber based on QuEChERS using HPLC-MS/MS technique.

BACKGROUND: To resist plant diseases, boscalid and triflumizole have been applied to cucumbers frequently. However, the residue and dietary risk assessment of these fungicides in cucumber should be given attention for food safety. RESULTS: An effective and highly sensitive method based on the liquid chromatography-tandem mass spectrometry technique for simultaneous multidetermination of boscalid, triflumizole and its metabolite (FM-6-1) in a cucumber ecosystem was established and validated. Field experiments were conducted in three different locations, where boscalid and triflumizole (35% suspension concentration) were applied at 253 g of active ingredient (a.i.) per hectare (the recommended high dosage) and 379.5 g a.i. ha-1 (1.5 times the recommended high dosage) in each location. The limits of quantification and the limits of detection of the proposed method ranged from 0.01 to 0.05 mg kg-1 and 3.9 × 10-5 to 7.5 × 10-4 mg L-1 respectively. The mean recoveries and relative standard deviations of these compounds were 80-105% and 1.0-6.1% respectively. The dissipation dynamics of compounds followed pseudo-first-order kinetic models remarkably, with a half-value period of 2.3-40.8 days. The residues of boscalid and triflumizole in cucumber at harvest were below 0.66 mg kg-1 and 0.07 mg kg-1 respectively. The results of the dietary risk assessments have shown a low dietary risk of compounds in cucumber with hazard ratios <1 and hazard index <1. CONCLUSION: These results from the experiments are the most important for putting a guide on reasonable usage of these fungicides under the open-field conditions in China. © 2018 Society of Chemical Industry.

Steam Explosion-Assisted Extraction of Ergosterol and Polysaccharides from Flammulina velutipes (Golden Needle Mushroom) Root Waste.

In this work, steam explosion (SE) was applied to prompt the rapid extraction of ergosterol and polysaccharides from Flammulina velutipes root (FVR) waste. Ultrasound-assisted saponification extraction (UASE) followed by water extraction was used to prepare ergosterol and polysaccharides. The results indicated that SE destroyed the complicated structure of FVR and increased its internal porosity and surface roughness. SE caused the thermal degradation of FVR's structural components and increased the polysaccharide content 0.97-fold. As a result, the extraction yield and efficiency of ergosterol and polysaccharides were improved. The theoretical maximum extraction concentration (C∞) and diffusion coefficient (D) were increased by 34.10% and 78.04% (ergosterol) and 27.69% and 48.67% (polysaccharides), respectively. The extraction yields obtained within 20-30 min of extraction time exceeded those of untreated samples extracted after several hours. For polysaccharides, SE led to a significant reduction in the average molecular weight, increased the percentage of uronic acids and decreased the neutral sugar percentage. The monosaccharide composition was changed by SE, with an increase in the molar ratio of glucose of 64.06% and some reductions in those of other monosaccharides. This work provides an effective method for the processing of fungi waste and adds to its economic value, supporting its high-value utilization in healthcare products.

Visible quantum cutting in GdF3:Eu(3+) nanocrystals via downconversion.

GdF3:Eu(3+) nanocrystals (NCs) and nanorods were synthesized by a microemulsion-mediated hydrothermal process. The structure, shape and particle size were characterized by means of x-ray diffraction (XRD) and transmission electron microscopy (TEM). The vacuum ultraviolet (VUV) spectrum of GdF3:Eu(3+) NCs shows that the Gd(3+) ion can absorb one VUV photon excited in the (6)GJ levels and relaxes through two-step energy transfer to Eu(3+), yielding two visible photons at room temperature. The visible quantum efficiency of GdF3:Eu(3+) NCs was calculated to be close to 170% by the peak intensity ratio of correlative transition emission under VUV excitation at 160 nm.