Residue dissipation kinetics, safety evaluation and consumer risk assessment of fipronil in cowpea and the soil

Fipronil is extensively used for insect pest management in cowpea; however, its residue dynamics under field conditions require a reliable analytical assessment to ensure food safety. In the present study, a sensitive and validated gas chromatography–micro electron capture detector (GC-µECD) method was developed for the determination of fipronil residues in cowpea pods, leaves and soil and its dissipation behaviour was evaluated under field conditions. Field experiments were conducted during the kharif season (2023–24) at ICAR–Indian Institute of Vegetable Research, Varanasi, India, using cowpea (Vigna unguiculata L.) variety Kashi Kanchan in a randomised block design with three replications. Fipronil 5 % SC was applied at the recommended dose (50 g a.i. ha-1) and double the recommended dose using a knapsack sprayer. Samples of pods, leaves and soil were collected at different intervals (0, 1, 2, 5, 7 and 10 days) after the final spray. Residues were extracted and cleaned using a modified QuEChERS method and quantified by GC-µECD. The method showed good linearity over the concentration range of 0.01–0.1 µg mL-1, satisfactory recoveries and a limit of quantification (LOQ) of 0.01 mg kg-1 for all matrices. Fipronil residues dissipated progressively with time, following first-order kinetics and declined below detectable levels within the recommended pre-harvest interval. Therefore, when used at recommended doses, fipronil presents a low risk profile in cowpea cultivation.