Abstract:

Bayberry is an important economic fruit in south China. Its quality and safety are highly concerned because of lacking registered pesticides and direct consumption habit with bare fruit without washing. Drosophila melanogaster is the most important insect which harm bayberry fruit during harvest time. Therefore, it is necessary to evaluate the residual risk of its control agents such as cyromazine, which has been widely used for preventing Drosophila melanogaster on bayberry. Cyromazine and its metabolite melamine were not easy to be analysed becaused of highly solubable property in water. In this study, an analytical method had been developed for analyzing cyromazine and its metabolite melamine using solid phase extraction coupled with high performance liquid phase tandem mass spectrometer (LC-MS/MS) under multi-reaction monitoring mode. The sample was extracted by 1% trichloroacetic acid solution, followed by purification with MCX SPE, and then detected by LC-MS/MS. The results showed that recoveries of cyromazine and melamine were in the range of 88%-110%. The relative standard deviations were less than 10%. The detection limit (LOD) for both cyromazine and melamine methods were 0.01 mg·kg ^-1. The quantitative limits (LOQ) of the methods were all 0.05 mg·kg ^-1, with good linear relationship in the range of 0.01-0.10 mg·L ^-1. The evaluation result of matrix effect showed matrix inhibition impact. Risk assessment results showed that both chronic and acute risk quotients for cyromazine and melamine were less than 1, indicating that their acute and chronic risks were negligible or within the acceptable range according to the monitoring data. In general, there was no risk protentical for bayberry consumers. This method had the advantages of good sensitivity, friendly to people and environment with less solvent usage. It could be applied for future risk monitoring of cyromazine and its metabolite melamine on bayberry.

Key words: bayberry, residues, cyromazine, melamine, risk assessment