Residues and dissipation dynamics of oxine-copper in the apple by gas chromatography-flame thermionic detector

The aim of this study is to evaluate the safety issues of oxine-copper in the apple and to develop a standard procedure for the safe use of oxine-copper. Residue degradations and final residue levels of oxine-copper in the apple from three experimental sites (Yantai, Shandong province, Shijiazhuang, Hebei province and Suzhou, Anhui province) were determined by GC-FTD. In the pretreatment process, ethylene diamine tetraacetic acid(EDTA)was used as a competitive ligand, and oxine-copper was transformed into 8-hydroxyquinoline. The method was validated at three spike levels (0.060 5, 1.0, and 2.0 mg/kg) in the apple. The average recoveries of oxine-copper in the apple were 80%-98%, with RSD of 1.0%-2.3%. The quantification limit of detection of oxine-copper in the apple was 0.060 5 mg/kg. As time went on, the residual contents of oxine-copper in the apple decreased, which accorded with the first-order kinetics equation. The results showed that the dissipation of oxinecopper in the apple was fast, with the half-lives of 4.4-7.4 d. This study also demonstrated that 21 days later, the residues of oxine-copper in the apple were safe at the recommended application dosage and rates according to the MRL of oxine-copper in the apple in China(temporary limit).