Dissipation kinetics, pre-harvest residue limits, and dietary risk assessment of the systemic fungicide metalaxyl in Swiss chard grown under greenhouse conditions.

The residual behavior of the systemic fungicide, metalaxyl, in Swiss chard cultivated at two different locations under greenhouse conditions was investigated using high-performance liquid chromatography coupled with an ultraviolet detector (HPLC-UVD). Samples were randomly collected over 14 days and extracted using acetonitrile, partitioned using solid sodium chloride, and a solid-phase extraction (SPE) NH2 cartridge was used for cleanup. The linearity over a concentration range 0.05-50 mg/L was excellent with a coefficient of determination (R2) of 0.9997. The recovery rate ranged from 77.05 to 88.92% with relative standard deviations (RSDs) ≤ 10.74, and the limits of detection (LOD) and quantification (LOQ) were 0.0033 and 0.01 mg/kg, respectively. The initial (2 h after application) deposits were 4.69 and 5.90 mg/kg for sites 1 and 2, respectively, which increased to 4.95 and 6.57 mg/kg, respectively, one day post-application, owing to the systemic properties of the fungicide. The dissipation half-life was 5.3 and 6.0 days for sites 1 and 2, respectively. The pre-harvest residue limit (PHRL) suggested that if 55.38 and 47.23 mg/kg was applied 10 days before harvest or 33.28 and 30.73 mg/kg was applied 5 days before harvest (for sites 1 and 2, respectively) then the concentration will fall below the maximum residue limit (MRL = 20.0 mg/kg) at the time of harvest. The dietary risk assessment, estimated as hazard quotient (RQ%), indicate that metalaxyl can be safely used in/on Swiss chard, with no hazardous effects expected for consumers.

A quick and effective methodology for analyzing dinotefuran and its highly polar metabolites in plum using liquid chromatography-tandem mass spectrometry.

A simple and effective method was developed for analyzing dinotefuran and its three metabolites (MNG, UF, and DN) in plum using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Due to the polarity and high water miscibility, dinotefuran and some of its metabolites (especially DN) have some limitations to be extracted with acetonitrile and salt following the "QuEChERS" sample preparation methodology. Alternatively, the samples were extracted with methanol, and purified with dispersive-solid phase extraction procedure (d-SPE) using primary secondary amine (PSA) and C18 sorbents after filtration, and mass up. Due to the suppression effect originated from plum matrix, matrix-matched calibration curves, which provided good linearity with coefficient of determination (R2)≥0.998, were used for quantification of all analytes. Blank plum samples fortified with 2 spiking levels (10×LOQ and 50×LOQ) yielded satisfactory recoveries for all tested analytes in the range of 83.01 to 110.18% with relative standard deviation (RSD)≤8.91. The method was successfully applied to field-incurred plum samples and dinotefuran and all metabolites were positively detected and quantified. In conclusion, we suggest that the method can be expanded to polar compounds having solvent and partitioning problems in any of the versions of QuEChERS.

Dynamic residual pattern of azoxystrobin in Swiss chard with contribution to safety evaluation.

This study aimed at quantifying the residual amount of azoxystrobin in Swiss chard samples grown under greenhouse conditions at two different locations (Gwangju and Naju, Republic of Korea). Samples were extracted with acetonitrile, separated by salting out, and subjected to purification by using solid-phase extraction. The analyte was identified using liquid chromatography-ultraviolet detection. The linearity of the calibration range was excellent with coefficient of determination 1.00. Recovery at three different spiking levels (0.1, 0.5, and 4 mg/kg) ranged between 82.89 and 109.46% with relative standard deviation <3. The limit of quantification, 0.01 mg/kg, was considerably much lower than the maximum residue limit (50 mg/kg) set by the Korean Ministry of Food and Drug Safety. The developed methodology was successfully used for field-treated leaves, which were collected randomly at 0-14 days following azoxystrobin application. The rate of disappearance in/on Swiss chard was ascribed to first-order kinetics with a half-life of 8 and 5 days, in leaves grown in Gwangju and Naju greenhouses, respectively. Risk assessments revealed that the acceptable daily intake percentage is substantially below the risk level of consumption at day 0 (in both areas), thus encouraging its safe consumption.

Residual dynamic and risk assessment of dimethomorph in Swiss chard grown at two different sites.

Residue analysis of dimethomorph in Swiss chard cultivated at two different locations under greenhouse conditions was conducted using high-performance liquid chromatography-ultraviolet detection and confirmed by tandem mass spectrometry. The randomly collected samples (over 14 days) were extracted with acetonitrile and purified using a Florisil solid-phase extraction cartridge. Linearity over a concentration range of 0.05-50.0 mg/L had an excellent coefficient of determination of 0.9996. Recovery rate ranged from 82.98 to 95.43% with relative standard deviations ≤5.12% and limits of detection and quantification of 0.003 and 0.01 mg/kg, respectively. The initial deposits [day 0 (2 h post-application)] were considerably lower (7.57 and 8.55 mg/kg for sites 1 and 2, respectively) than the maximum residue limit (30 mg/kg) set by the Korean Ministry of Food and Drug Safety. The dissipation half-life was approximately the same, being 5.0 and 5.1 days for sites 1 and 2, respectively. Risk assessment estimated as acceptable daily intake revealed a value of 0.084 or 0.094% (day 0) and 0.014% (10 days post-application), for sites 1 and 2, respectively. The values indicated that dimethomorph can be safely used on Swiss chard, with no hazardous effects expected for Korean consumers.

Residual determination and risk assessment of buprofezin in plum (Prunus domestica) grown in open-field conditions following the application of three different formulations.

This study was conducted to characterize the residual level and perform a risk assessment on buprofezin formulated as an emulsifiable concentrate, wettable powder, and suspension concentrate over various treatment schedules in plum (Prunus domestica). The samples were extracted with an AOAC quick, easy, cheap, effective, rugged, and safe, 'QuEChERS', method after major modifications. As intrinsic interferences were observed in blank plum samples following dispersive-solid phase extraction (consisting of primary secondary amine and C18 sorbents), amino cartridges were used for solid-phase extraction. Analysis was carried out using liquid chromatography with diode array detection and confirmed by liquid chromatography-tandem mass spectrometry. The method showed excellent linearity with determination coefficient (R2 = 1) and satisfactory recoveries (at two spiking levels, 0.5 and 2.5 mg/kg) between 90.98 and 94.74% with relative standard deviation (RSD) ≤8%. The limit of quantification (0.05 mg/kg) was considerably lower than the maximum residue limit (2 mg/kg) set by the Codex Alimentarius. Absolute residue levels for emulsifiable concentrates were highest, perhaps owing to the dilution rate and adjuvant. Notably, all formulation residues were lower than the maximum residue limit, and safety data proved that the fruits are safe for consumers. Copyright © 2016 John Wiley & Sons, Ltd.