QUANTITATIVE SUPERCRITICAL FLUID EXTRACTION OF SULFONYL UREA HERBICIDES FROM AQUEOUS MATRICES VIA SOLID-PHASE EXTRACTION DISKS

The quantitative and reproducible supercritical fluid extraction (SFE) of two sulfonyl urea herbicides, sulfometuron methyl (CAS Reg. No. 74222-97-2) and chlorsulfuron (CAS Reg. No. 64902-72-3), is demonstrated. Both herbicides are extracted quantitatively with supercritical 2% methanol-modified CO2from both a Celite™ matrix and water via solid phase extraction (SPE) disks. The Celite extractions are used to determine optimum conditions for extraction and to see if the analytes are indeed quantitatively extractable by SFE without the possibility of matrix interferences. Parameters investigated include solid phase trapping material, trap rinse solvent, trap temperature during extraction, removal of spiking solvent, type of supercritical fluid, and minimum extraction time. The SFE extracts are analyzed by high-performance liquid chromatography (HPLC) with ultraviolet absorbance detection. Extraction recoveries of 97.2% (RSD = 7.8%) and 93.6% (RSD = 5.5%) are achieved for sulfometuron methyl and chlorsulfuron, respectively, off of a C8SPE disk using 2% methanol-modified CO2Analytes are deposited on the disk via 1-L water samples. Comparisons are made to traditional organic solvent elution of the SPE disk. © Oxford University Press 1992.