Xiao-Jun Chen

Determination and Safety Assessment of Residual Spirotetramat and Its Metabolites in Amaranth (Amaranthus tricolor) and Soil by Liquid Chromatography Triple-Quadrupole Tandem Mass Spectrometry

With the purpose of guaranteeing the safe use of spirotetramat and preventing its potential health threats to consumers, a QuEChERS extraction method coupled with LC triple-quadrupole tandem MS was applied in this study to determine residual spirotetramat metabolites in different tissues of amaranth (Amaranthus tricolor) and in soil. The results indicate that the spirotetramat degraded into different types of metabolites that were located in different tissues of amaranth and in soil. B-keto, B-glu, and B-enol were the three most representative degradation products in the leaf of amaranth, and B-glu and B-enol were the two major degradation products found in the stem of amaranth; however, only B-enol was detected in the root of amaranth. B-keto and B-mono were the two products detected in the soil in which the amaranth grew. The cytotoxicity results demonstrate that spirotetramat and its metabolite B-enol inhibited cellular growth, and the toxicity of spirotetramat and its metabolite B-enol exceeded than that of the metabolites B-keto, B-mono, and B-glu. This investigation is of great significance to the safe use of spirotetramat in agriculture.

Preservative Effects of Strobilurin Fungicides on Citrus Storage Diseases and Residue Safety Assessment

Ethofenprox, pyraclostrobine, trifloxystrobin and enestroburin are strobilurin fungicides that can effectively control fungal diseases caused by ascomycetes, zygomycetes, imperfect fungi, etc. With the purpose of guaranteeing the safe use of strobilurin fungicides in the prevention and treatment of citrus diseases, toxicity and control effects of the fungicides on citrus storage diseases and GC-MS (gas chromatography-mass spectrometry) were applied in this study to determine its residual safety. The results indicated that ethofenprox, trifloxystrobin, pyraclostrobine, and enestroburin had excellent inhibitory effects on citrus storage diseases at concentration of 200-400 ug/mL. Degradation dynamics of 4 fungicides during the storage period of citrus could be expressed as the first-order kinetics equation. The fungicides could penetrate into flesh through peels slowly. Therefore, the residue content of the fungicide on peels was higher than that in the flesh of the same citrus. After citrus fruits were treated for 90 d, the residues were lower than the maximum residue limits in all the countries, so the citrus were safe. This investigation provided the theoretical guidance and technical support for the quality evaluation of citrus products.