Na(4)EDTA-assisted sub-/supercritical fluid extraction procedure for quantitative recovery of polar analytes in soil

Supercritical carbon dioxide (SC-CO2) is effective in extracting nonpolar a nd slightly polar chemicals from soils. However, pure SC-CO2 is unsatisfact ory for recovering polar chemicals in soils. A simple supercritical fluid e xtraction (SFE) procedure was developed to quantitatively recover polar and nonpolar chemicals from soils. The polar chemicals tested were aromatic ac ids and phenols. The nonpolar and slightly polar chemicals used as model co mpounds were common pesticides and environmental pollutants such as polycyc lic aromatic hydrocarbons. The procedure required pretreatment of the sampl es with 15% water (g/g), 5% (ethylenedinitrilo)tetraacetic acid tetrasodium salt (Na(4)EDTA) (g/g), and 50% methanol (mL/g) prior to extractions using SC-CO2 at 60 degrees C and 34.5 MPa. Recoveries ranged from 90 to 106% for the aromatic acids using the Na(4)EDTA-assisted SFE compared with only 7-6 3% recoveries of the corresponding chemicals when no Na(4)EDTA was used. Th e method quantitatively extracted 2,4-D and its close analogues aged in the soil for 2-30 days. The Na(4)EDTA-assisted SFE was also adequate for extra cting phenolic analytes including picric acid and pentachlorophenol with re coveries from 85 to 104%. Na(4)EDTA is a good enhancer for extraction of th e 29 analytes representing a wide range of polarity from the soil using SC- COB. The method is valuable for the analysis of parent pollutants and trans formed products, particularly oxygen-borne metabolites in the environment.