Supercritical fluid extraction of carbamate pesticides from soils and cereals

A method for the supercritical fluid extraction of carbamate pesticides (propoxur, aminocarb, carbaryl and methiocarb) from soil and cereal samples using CO2 is proposed. Extractions were at 378 bar and 54 degrees C. Analytes were determined in the extracts by HPLC with fluorescence detection after post-column derivatization. Recoveries from spiked soil ranged between 39.6 and 91.7%, depending on analyte and soil components. Lowest recoveries were from sandy soils. Aminocarb could not be recovered from any soil using CO2. Recovery of aminocarb from diatomaceous earth was improved by adding methanol to the extraction cell prior to SFE, but the effect was not observed in soil samples. Recoveries for propoxur and aminocarb from spiked wheat were about 75%, and only between 30-50% for aminocarb from corn and oats, and carbaryl from wheat. Fat was coextracted using CO2 and retained in the trap together with the analytes, however, appropriate rinsing solvent allowed on-line clean-up of the extract.