Extraction of pesticides from soil using supercritical carbon dioxide added with methanol as co-solvent

In this work, supercritical fluid extraction (SFE) using carbon dioxide (SC-CO2) added with methanol (MeOH) as cosolvent was employed in the extraction of a mixture of 31 pesticides in soil. Different conditions of pressure (10, 15 and 20 MPa), temperature (308, 313 and 318 K) and extraction time (3× 10 min, 3× 15 min, 4× 10 min, 4× 15 min and 5× 10 min, each one in static mode) were explored. The influence of organic matter (OM) content of soil on the SFE of pesticides was evaluated. Additionally, the effect of time elapsed between the fortification and the SFE on the recovery rate (% R) of pesticides was determinated. The extracts obtained were analyzed using gas chromatography (GC) with simultaneous detection by electronic microcapture (μ-ECD) and nitrogen-phosphorus detectors (NPD), coupled in parallel. It was found that the most suitable conditions for the SFE of pesticides under study were 15 MPa, 318 K and 4 static stages of 10 min, with values of % R above 70% for most pesticides. It was noted that for 16 of the 30 pesticides, the OM content were not an influential factor on recovery, 11 pesticides had high % R in soils with high OM content, and the % R for only 3 pesticides decreased when increasing the OM content in soil. Regarding the effect of time between fortification and SFE, we found that for 20 of the 30 pesticides this factor does not affect their % R. This work allowed to demonstrate that the SC-CO2 as solvent added with methanol as cosolvent (SC-CO2/MeOH) was an alternative for the extraction of pesticides from soils.