Five-way ANOVA Interaction Analysis of the Selective Extraction of Carbaryl, Pirimicarb and Aldicarb From Soils by Supercritical Fluid Extraction

Abstract

Due to the biopersistence of organophosphate and organochloride compounds, the hydrolytic degradation of the carbamate insecticides has proved attractive in the reduction of persistent insecticides in the biosphere and food chain. Their susceptibility to hydrolysis, however, can complicate their analysis and care is required in the selection of the extraction conditions and the analytical technique employed. The work described here is an investigation into method optimisation in the extraction and final analysis of selected carbamate insecticides from selected soils. A method using the inert extraction medium of supercritical carbon dioxide has been developed for determination of three carbamates relevant to the soft fruit growing industry (carbaryl, aldicarb and pirimicarb). Determinations were completed using HPLC-postcolumn reaction-fluorescence with orthophthalaldehyde-mercaptoethanol derivatisation. The resultant methylisoindole fluorophore was detected at λ _ex :330 nm and λ _em :450 nm with pirimicarb detection at λ _ex :315 nm and λ _em :380 nm. A five variable ANOVA analysis was carried out to determine both the most significant independent factors in the extractions and their most significant statistical interaction(s). Retrospectively optimised extraction conditions were obtained from the ANOVA where many of the carbamates were successfully extracted from each soil using CO ₂ at 300 atm modified with 10% dimethyl sulfoxide. The mean recoveries obtained were 91.5–107.8% for all carbamates from many soils.