Estimation of fenazaquin residues in brinjal, okra and soil
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Date
2019
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Punjab Agricultural University, Ludhiana
Abstract
Supervised field trials were conducted to study the residues of fenazaquin in brinjal and okra following its application at minimum effective (25 g a.i. ha-1), double the minimum effective (50 g a.i. ha-1) and the recommended dose (125 g a.i. ha-1), respectively. The samples were collected at 0 (2 hrs), 1, 3, 5, 7, 10 and 15 days after its application at an interval of 10 days. Sample processing was done following QuEChERS methodology and quantification by High Performance Liquid Chromatography (HPLC) followed by confirmation with Liquid Chromatograph-Mass Spectrometry (LC-MS). The mean initial deposits of fenazaquin on brinjal were 0.046, 0.098, 0.174 and 0.048, 0.102, 0.170 mg kg-1 following its last application during 2017-18 and 2018-19, respectively. For the corresponding doses on brinjal, the residues declined below limit of quantification (LOQ <0.01 mg kg-1) after 3, 5 and 7 days following its last application. The average initial deposits of fenazaquin on okra were 1.663, 2.037, 3.117 and 1.611, 2.299, 3.100 mg kg-1 during 2017-18 and 2018-19, respectively. The residues declined below LOQ at 7, 10 and 15 days during 2017-18 whereas during 2018-19 the residues reached below LOQ after 15 days following application of fenazaquin at all the three doses, respectively. Residues of fenazaquin were found below LOQ in the soil samples collected after 15 days of last application from both brinjal and okra fields. The half-life of 0.75, 1.16, 1.43 and 1.62, 1.75, 1.92 days in brinjal and okra was calculated following its last application at all the three doses, respectively. The average initial deposits observed at recommended dose were more than maximum residue limit of 0.01 mg kg-1 so, the waiting period of 7 and 15 days is suggested for safe consumption of brinjal and okra. Leaching studies showed the presence of fenazaquin residues in the upper layer (0-15 cm) only in the soil columns installed under field capacity and flooding conditions at different time intervals. None of the residues were detected in the leachate collected under both these conditions.
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