Temporal–spatial analysis of cyromazine in cowpea using liquid chromatography–mass spectrometry coupled with mass spectrometry imaging

Abstract

Background: Cowpea (Vigna unguiculata L. Walp.) is an economically important crop. It is nutritious and popular with consumers. However, it has been listed as one of the agricultural products of critical concern about safety in China and cyromazine is the major risk factor. Objectives: This study analyzed the dissipation and permeation kinetics of cyromazine residue in cowpea, to offer a scientific basis for the rational use of pesticide and ensure the safety of agricultural products. Materials and methods: The dissipation and residue level of the systemic insecticide cyromazine on cowpea under field and stored conditions were investigated. Subsequently, the spatial distribution of cyromazine was studied using mass spectrometry imaging to visualize the dynamic processes of permeation and migration in the tissues post pesticide application. Results: The dissipation processing of cyromazine in cowpea was shown to follow the first-order kinetics and half-life was 7.76 d in the field. In cowpea, the permeation and migration rate of cyromazine was faster than that in kidney beans and accumulation was mainly in the pulp. It is not safe to apply cyromazine to cowpeas with reference to the application method on kidney beans. Conclusions: These findings present vital data for the determination of risks linked with cowpea consumption and pesticide intake.