thiophanate and tebuconazole

Winter is the key period for the control of apple diseases, and fungicides are needed to protect the trunk or main branches. Fungicide residue in apple tree bark is an important basis for the action of the pesticide, but there are no reports on analytical methods or dissipation patterns. In this work, thiophanate-methyl, carbendazim, tebuconazole and pyraclostrobin were selected as typical fungicides and a new QuEChERS-HPLC-VWD(QuEChERS extraction followed by high-performance liquid chromatography detection with a variable wavelength detector) analytical method was developed to estimate their residue kinetics in apple tree bark during the winter months. In the pretreatment step, the sorbent for the clean-up of extracts was optimized as 60 mg/ml primary secondary amine and a gradient-elution model followed by a variable wavelength detection was developed for instrumental analysis. Then this method was validated and applied to the analysis of apple tree bark samples with the linearity range of 0.010-50.00 mg/L, quantification limit range of 0.028-0.080 mg/kg and recovery range of 86.1-101.4%. The dissipation kinetics of thiophanate-methyl and pyraclostrobin could be described by the first-order and two-phase kinetics models, respectively. For carbendazim and tebuconazole, two new models were developed to describe their residue kinetics.

Topics: Benzimidazoles; Carbamates; Chromatography, High Pressure Liquid; Fungicides, Industrial; Linear Models; Malus; Pesticide Residues; Plant Bark; Reproducibility of Results; Sensitivity and Specificity; Spectrophotometry, Ultraviolet; Strobilurins; Thiophanate; Triazoles

A multi-residue method for the determination of 107 pesticide residues in wolfberry has been developed and validated. Similar pretreatment approaches were compared, and the linearity, matrix effect, analysis limits, precision, stability and accuracy were validated, which verifies the satisfactory performance of this new method. The LODs and LOQs were in the range of 0.14-1.91 µg/kg and 0.46-6.37 µg/kg, respectively. The recovery of analytes at three fortification levels (10 µg/kg, 50 µg/kg, 100 µg/kg) ranged from 63.3-123.0%, 72.0-118.6% and 67.0-118.3%, respectively, with relative standard deviations (RSDs) below 15.0%. The proposed method was applied to the analysis of fifty wolfberry samples collected from supermarkets, pharmacies and farmers' markets in different cities of Shandong Province. One hundred percent of the samples analyzed included at least one pesticide, and a total of 26 pesticide residues was detected in fifty samples, which mainly were insecticides and bactericide. Several pesticides with higher detection rates were 96% for acetamiprid, 82% for imidacloprid, 54% for thiophanate-methyl, 50% for blasticidin-S, 42% for carbendazim, 42% for tebuconazole and 36% for difenoconazole in wolfberry samples. This study proved the adaptability of the developed method to the detection of multiple pesticide residues in wolfberry and provided basis for the research on the risks to wolfberry health.

Topics: Benzimidazoles; Carbamates; Chromatography, High Pressure Liquid; Humans; Liquid-Liquid Extraction; Lycium; Neonicotinoids; Nitro Compounds; Nucleosides; Pesticide Residues; Tandem Mass Spectrometry; Thiophanate; Triazoles

An efficient method was developed and validated for simultaneous determination of tebuconazole, thiophanate-methyl and its metabolite carbendazim in grape and soil using QuEChERS procedure and liquid chromatography-tandem mass spectrometry. The average recoveries of the method were 83.2%-105.4%, the limit of detection (LOD) ranged from 2.1 × 10

Topics: Benzimidazoles; Carbamates; China; Chromatography, Liquid; Dietary Exposure; Food Contamination; Half-Life; Humans; Limit of Detection; Pesticide Residues; Risk Assessment; Soil Pollutants; Tandem Mass Spectrometry; Thiophanate; Triazoles; Vitis

A new bioassay has been developed combining the simplicity of direct bioautography with the improved chromatographic resolution of 2D-TLC. Mixtures of structurally diverse antifungal agents were tested to establish the validity and utility of this method in the discovery of new natural products with activity against agriculturally important fungal pathogens.

Topics: Acrylates; Aniline Compounds; Antifungal Agents; Ascomycota; Benzimidazoles; Biological Assay; Captan; Carbamates; Chromatography, Thin Layer; Colletotrichum; Dimethyldithiocarbamate; Fungicides, Industrial; Guanidines; Maneb; Methacrylates; Nitriles; Nitrobenzenes; Oxazoles; Piperazines; Plant Diseases; Plants; Pyrimidines; Strobilurins; Thiabendazole; Thiophanate; Triazoles