Supercritical Fluid Extraction of Metsulfuron Methyl, Sulfometuron Methyl, and Nicosulfuron from Soils

Abstract

Sulfonylurea herbicides are usually extracted from soils with batch liquid techniques. The objective of this study was to develop a general supercritical fluid extraction (SFE) procedure for sulfonylurea herbicides in soils. The procedure was optimized for metsulfuron methyl, and the parameters investigated included: SF-CO₂ density, extraction time, and methanol modifier addition. Quantitative extraction could only be performed at high densities (i.e., 0.9 g ml⁻¹) and with 2% (w/w) modifier addition. ¹⁴C-labeled metsulfuron methyl, sulfometuron methyl, and nicosulfuron were extracted from sandy loam, silt loam, and clay loam soils spiked at two levels (0.4 and 4 μg g⁻¹) of herbicide. Under the conditions used, good recoveries of metsulfuron methyl and sulfometuron methyl (75–89%) were obtained. However, nicosulfuron was difficult to extract (1–4%). The results show that an optimized method cannot always be directly applied to similar compounds without further method development.

Key Words:

• SFE
• sulfonylurea herbicides
• metsulfuron methyl
• sulfometuron methyl
• nicosulfuron
• soils