Abstract
A new method to evaluate the levels of residue and the dissipation of chlorothalonil fungicide in tomatoes and cucumbers grown in experimental greenhouses was developed and validated. The vegetables were submitted to a single spraying with chlorothalonil at half, equal to and double of the recommended dose. Chlorothalonil residues were extracted in Ultra-Turrax system using ethyl acetate in the presence of anhydrous sodium sulphate and determined by gas chromatography with electron capture detection. The analytical curves were linear from 0.005 to 5.0 mg L-1, with coefficient of determination higher then 0.995. The assays provide acceptable results with RSD values below 10.5% and recoveries were between 92.2 and 114.5% for tomatoes, and between 86.2 and 103.3% for cucumbers, both obtained from spiked samples at 0.028, 0.28, 2.8 and 5.0 mg kg-1 levels. Statistical interpretation of residue levels fitted to a first-order model for the dissipation behavior of chlorothalonil. The mean half-life after treatments at the recommended dose, in the two experimental years, was 8.8 days for tomatoes and 1.6 days for cucumbers. The higher decrease rate of chlorothalonil residues in cucumbers is mainly due to the higher growth rate of this vegetable relative to tomato. The developed method has proven to be efficient for the determination of chlorothalonil residues in tomatoes and cucumbers with a limit of quantification of 0.02 mg kg-1 level, permitting to evaluate the risk of consumer exposure to these residues.
Highlights
Chlorothalonil is an effective foliage-protector against a broad range ofA Gas Chromatographic Method for the Determination of the Fungicide ChlorothalonilJ
The chromatograms obtained by gas chromatograph (GC)-electron capture detector (ECD) corresponding to standard solutions of chlorothalonil prepared in the pure solvent and in the matrix extracts of tomato and cucumber are show in the Figure 2
The results demonstrate that the GC-ECD response for chlorothalonil presents matrix effect[29,30] for the tomato and cucumber, evidenced mainly by the differences in the obtained analytical curves
Summary
Chlorothalonil (tetrachloroisophtalonitrile class) is an effective foliage-protector against a broad range ofA Gas Chromatographic Method for the Determination of the Fungicide ChlorothalonilJ. Chlorothalonil (tetrachloroisophtalonitrile class) is an effective foliage-protector against a broad range of. A Gas Chromatographic Method for the Determination of the Fungicide Chlorothalonil. With LD50 for rats (oralapplication) of 10000 mg kg-1 and of short persistence in the environment.[2] It is widely used in Brazil principally in tomatoes and cucumbers. The Maximum Residue Limit (MRL) for chlorothalonil in tomatoes and cucumbers established in Brazil are 1.0 and 0.1 mg kg-1 respectively, with a preharvest interval of 7 days.[3] The Codex Alimentarius Commission[4] and the Food and Drugs Administration (USA)[5] established a MRL of 5 mg kg-1 for chlorothalonil in both vegetables. The European MRL for chlorothalonil was fixed in 0.01 mg kg-1 for both vegetables.[6]
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