EFFECTS OF MODIFIERS, ADSORBENTS AND ELUENTS IN SUPERCRITICAL-FLUID EXTRACTION OF SELECTED PESTICIDES IN SOIL

The applicability of supercritical fluid extraction (SFE) in pesticide residue analysis of fenpropimorph, pirimicarb, parathion-ethyl, trial late and fenvalerate in soil was investigated. Fortification experimen ts were conducted to optimize the extraction procedure by varying modi fiers, trap adsorbents and eluents. Best efficiency was achieved at 60 degrees C extraction temperature and CO2 pressure of 3.8.10(7) Pa by the use of 5% methanol as modifer, a diol-modified silica gel trap and ethyl acetate as eluent. Recoveries of the target compounds ranged fr om 93-104%. Additionally, real soil samples taken 3 and 31 days after application under field conditions were analyzed for fenpropimorph, pi rimicarb and parathion-ethyl residues by SEE and slurry as well as Sox hlet extraction technique. For all extraction methods investigated com parably high extraction efficiency was achieved. SFE is the most rapid procedure considering especially that no time-consuming clean-up step s are necessary. However, the little sample size applicable in the ins trument specific extraction thimbles is the limiting factor in the det ection of pesticides at low concentrations. Therefore, SFE extracts of replicates have to be pooled and concentrated in order to yield detec tion limits as low as those of conventional extraction procedures. (C) 1997 Elsevier Science B.V.