Automated Procedure for Extraction of Metolachlor from Soil

Abstract

Methods for extraction of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] from soil are tedious and time-consuming. Existing robotic stations were adapted to provide an automated multistep method of metolachlor extraction from soil. The method was examined using a fine-loamy, mixed Udic Haploboroll. Duration of equilibration (0−4 h), initial soil pH (5.0−7.1), temperature of evaporation (24, 35, and 50 °C), and gas used for perfusion (air or N2) were examined. Extraction efficiency was unaffected by duration of equilibration or initial soil pH. A temperature by perfusion gas interaction affected percent recovery. At 24 °C, N2 provided a small but measurable advantage in recovery, 71.1−74.2%. At 35 °C, a clear advantage in recovery, 50.5−69.8%, was obtained using compressed air. At 50 °C, recovery, which averaged only about 38%, was unaffected by perfusion gas. Relative recovery was unaffected by incubation time in 90% methanol over a 4-h range. Relative to the current extraction method, the serialized robotic method increased sample output by 267%. Relative costs of extraction were also compared. Hazardous waste generation was decreased by about 67%, and reagent cost was decreased by > 75% using the robotic method.