M22 - Mass Spectrometric Quantification of β-Cyfluthrin Residues on Leafy Vegetables

Pyrethroids like β-cyfluthrin are synthetic analogues of natural pyrethrins derived from the flowers of pyrethrums (Chrysanthemum cinerariaefolium and C. coccineum). β-cyfluthrin is a commonly used insecticide on Brassica leaves to control insects attack such as Lepidoptera, Coleoptera, Hemiptera, and Diptera families for better crop yield and quality. A field study was conducted to study the dissipation of β-cyfluthrin on collard and kale leaves following spraying of the commercial formulation Baythroid ® XL. The objectives were to 1) develop an analytical method for the determination of the total β-cyfluthrin isomers, 2) determine the dissipation constants and half-life (T½) values of β-cyfluthrin on kale and collard grown under field conditions, and 3) determine workers' re-entry time following β-cyfluthrin spraying for workers and consumer safety. Residues were extracted from the leaves using ethyl acetate and cleaned up through an open glass chromatographic column packed with Florisil. A gas chromatograph (GC) equipped with an electron capture detector (GC/ECD) and a GC equipped with a mass selective detector (GC/MSD) were used for quantification and confirmation of the insecticide residues. The method successfully separated the 4 isomers of β-cyfluthrin, revealing the molecular ion fragments at m/z of 127, 163, 206, and 226, respectively. Following spraying, the initial residues (sum of isomers) of β-cyfluthrin were lower on collard (9.5 µg g^-1) than on kale leaves (28.8 µg g^-1 fresh leaves). The study revealed a greater T_1/2 value of 8.2 days of β-cyfluthrin on collard than on kale leaves (5.1 days).