A study of quinclorac degradation during thermal and forced hydrolysis and soil photolysis

Abstract

N THE PRESENT study, the stability of quinclorac as (Queen 75% WG) during the forced thermal degradation at temperatures, forced acidic and alkaline hydrolysis, and soil photolysis was investigated. The results indicate that the maximum active ingredient degradation of quinclorac (5.57%) was achieved during storage at 54°C after 14 weeks. During the same time period, however, the reduction was modest, ranging between 1.5-3% at 35, 40, and 45°C, respectively. The shelf life of quinclorac after storage at different temperatures was consistent with the time period recommended by FAO/WHO. The acidic hydrolysis of quinclorac improved the shelf-life and half-life to 5.40 and 72.96 days, respectively, which is almost four times that of 1.0 N HCl. However, in alkaline conditions, the shelf-life and half-life of quinclorac were lowered to 1.02 and 13.73 days, respectively. Increasing the alkaline concentration to 1.0 N NaOH further reduced these results to 0.44 and 5.95 days, respectively. Generally, the kinetics of quinclorac degradation followed a first-order model that was reliant on its initial concentration. Furthermore, the half-life of quinclorac dissipation was determined to be 124 days in local clay-loam soil (with organic matter of 1.92%) and a significant saturation percentage of 62.99% and hence it is considered a persistent herbicide. The degradation products of quinclorac were identified by GC/MS and may be attributed to decarboxylation, dechlorination, hydroxylation, and the substitution of chlorine with a hydroxyl group.