Solid-phase extraction of aldicarb and its metabolites from water and soil

Extraction methods using solid-phase extraction (SPE) cartridges are generally preferred over traditional liquid-liquid extraction methods when they are available. Solid-phase extraction methods require less preparative work, thus increasing sample through-put. A SPE method using a graphite carbon sorbent was developed to extract low concentrations (1-40 mu g/L) of the polar pesticide, aldicarb [2-methyl-2-(methylthio)propionaldehyde de O-(methylcarbamoyl) oxime], and its oxidative metabolites, aldicarb sulfoxide [2-methyl-2-(methylsulfinayl)propionaldehyde-O-(methylcarbamoyl) oxime] and aldicarb sulfone [2-methyl-2-(methylsulfonyl) propionaldehyde-O-(methylcarbamoyl) oxime] from water samples. The analytes were removed from a 150-mL water sample by the SPE cartridge and eluted with 2 mt of methanol. Recoveries from water for all three compounds exceeded 90% with coefficients of variation ranging from 3 to 9%. An extraction method was also developed to extract aldicarb and its metabolites from soil using water as the extractant, The analytes are then recovered from the water using the same SPE method referred to above. Recoveries from soil for all three compounds ranged from 80 to 95%. Our SPE method also worked well (recoveries >95%) for two other carbamates, methomyl [S-methyl N-[(methylcarbamoyl)oxy]thioacetimidate] and oxamyl [N',N'-dimethyl-N-[(methylcarbamoyl)oxy]-1-thiooxamimidate] tested and should work with other polar compounds once they are in the aqueous phase.