Dissipation, Residue Behavior and Dietary Risk Assessment of Difenoconazole on Jujube (Ziziphus jujuba Mill.)

Abstract

Difenoconazole is a triazole germicide that is usually applied to prevent fungal diseases on crops with high efficiency and safety. Jujube is a spiny Rhamnaceous plant that originated in China more than 4000 years ago and is extensively cultivated in northern China nowadays. To evaluate the safety of difenoconazole in jujube, supervised field trials were carried out in six provinces of China, and the final residue and dissipation behavior of difenoconazole on jujube were determined by gas chromatography (GC). The results showed that when addition levels were 0.02, 0.2, and 2 mg·kg−1, average recoveries of the aforementioned method for difenoconazole in jujube can be put into the range of 73–108%, and relative standard deviation (RSD) was 3–9%. The limit of quantitation (LOQ) for this method was 0.02 mg·kg−1. In the final residue test, difenoconazole was sprayed to deal with the jujube at 100 and 150 mg·kg−1 doses twice or three times, respectively, while the dissipation test was applied only once at a 150 mg·kg−1 dose. Final residue testing results have revealed that when jujube samples were harvested and tested at 7, 14, and 21 days post-application, difenoconazole residues in samples were 0.11–1.59, 0.05–0.77, 0.04–0.63 mg·kg−1, respectively. The dissipation testing results showed that the digestion process of difenoconazole in jujube tends to be a gradual reduction process and the dynamic regularity of the residue dissipation proves consistent with the first-order dynamics reaction equation. The half-life (t1/2) for difenoconazole residue dissipation in Qingdao and Yuncheng was 13.1 days and 16.5 days, respectively. The risk quotient (RQ) was 84.9% lower than 100%, showing that dietary intake risk to difenoconazole was acceptable and the maximum residue limit (MRL) of difenoconazole on jujube is recommended to be 2 mg·kg−1.