Investigation of the supercritical fluid extraction and detection of metals in contaminated soils

Abstract

In this work the Supercritical Fluid Extraction (SFE) and detection of sorbed metals in contaminated soils is explored. Iron containing samples were spiked onto sea sand and extracted with Supercritical Fluid CO₂. On-line detection was accomplished by decompressing the SF-CO₂ and analyte into a microwave induced plasma, whereby the resulting Iron atomic emission signal was quantified. This dissertation reports the first successful coupling of SFE and Microwave Induced Plasma - Atomic Emission Detection (MIP-AED) for the on-line analysis of sorbed metal contaminants. The on-line analysis was accomplished with a novel SFE-MIP interface design.

Experiments involving the on-line extraction and detection of ferrocene spiked sea sand were very promising, in that unity of extraction and detection was achieved with this nonpolar compound. Percent recovery was greatly reduced when the on-line extraction of Iron III Trifluoroacetylacetonate (FeTFA) was attempted. Off-line extraction studies were performed to establish the optimum conditions necessary to effect the SFE of the following Iron III complexes: Iron III Acetylacetonate (FeAcac) and Iron III Trifluoroacetylacetonate. The greatest recovery (55.85 0/0) was achieved with Supercritical Fluid-CO₂ under the following conditions: 60°C, 150 atm, 20 minute static extraction followed by 20 minute dynamic extraction. The extraction vessel contained 0.250 mg iron complex, 20 μL HPLC grade methanol, and 20 μL deionized water. Trapping of the analyte was achieved by decompressing the SF-CO₂ and analyte in 10 mL of HPLC grade methanol held at O°C.