EXTRACTION OF ATRAZINE, CYANAZINE, DESETHYLATRAZINE, DESISOPROPYLATRAZINE, AND METOLACHLOR FROM FORTIFIED WESTERN CORN-BELT SOILS BY SFE WITH CO2

Supercritical fluid extraction (SFE) using CO2 has been demonstrated as an alternative to polar organic solvents or water for the quantitative removal of atrazine, two of its metabolites, cyanazine, and metolachlor for several agricultural soils. Recoveries of each analyte from soil fortified from 0.1 to 2.0 mg/kg ranged between 25 and 120%, depending upon the soil matrix and analyte extracted. A single extraction, using cosolvent-modified CO2, conducted at relatively high fluid density in both static and dynamic modes, sufficed for all analytes. Principal component analysis was used to correlate each component in a matrix of dependent variables influencing extraction efficiency. HPLC analysis indicated that fewer coextracted moieties are found using SFE rather than from extractions using polar liquid solvents. Addition of both water and methanol to the air-dried soil prior to commencement of CO2 flow does enhance the recovery for all analytes. Further, such cosolvents do not promote the conversion of the chloro-triazine analytes to any of their corresponding hydroxy or methoxy analogs under the SFE conditions tested.