Supercritical Fluid Extraction and Solid-Phase Extraction of AC 263,222 and Imazethapyr from Three Texas Soils

Abstract.

Supercritical fluid extraction (SFE) using CO₂ and solid-phase extraction (SPE) are two technologies recently discussed in the literature as alternatives to Soxhlet and liquid/liquid extraction (LLE). This research compared SFE and SPE extraction efficiency of two imidazolinone herbicides, AC263,222 and imazethapyr, from three soils. Recovery of the herbicides using SFE-CO₂ with a 4.6:1 acetonitrile:acetic acid cosolvent was approximately 80% for Poth and Tremona soils and 60% when extracted from Ships soil with high clay content and high pH. SPE recovery of both herbicides averaged 78% and was not statistically different between soils. Combining SPE disks with a SPE cartridge cleanup procedure provided a faster filtration with cleaner filtrate compared with using SPE C-18 cartridges by themselves. Cleanup was needed after both SFE and SPE disk extraction due to interfering peaks in the chromatography.