A SOLID-PHASE EXTRACTION BASED SOIL EXTRACTION METHOD FOR PESTICIDES OF VARYING POLARITY

Solid-phase extraction (SPE) is an innovative method for efficiently a nd quantitatively extracting pesticides from large numbers of soil sam ples. An extraction method using commercially available SPE columns ha s been developed and tested using three herbicides of varying polarity : bromacil hyl-3-(1-methylpropyl)-2,4(1H,3H)pyrimidinedione], napropam ide [N,N-diethyl-2-(1-na-phthalenyloxy)propanamide], and prometryn -th yl)-6-(methylthio)-1,3,5-triazine-2,4-diamine]. The soil sample is sha ken with a methanol/water mixture and centrifuged. The supernatant is then diluted with a concentrated NaCl solution, and drawn through an S PE column. The sorbed pesticides are finally eluted from the column wi th methanol. This method requires no specialized laboratory equipment and is well suited for processing large numbers of samples. Analyses o f spiked soil samples show recoveries of over 90% and average coeffici ents of variation (CV's) ranging from 5% at high soil pesticide concen trations to 18% at lower concentrations. The practical detection limit for the method is approximately 10 mug/kg.