RESIDUE LEVELS OF PYRETHRINS AND PIPERONYL BUTOXIDE IN SOIL AND RUNOFF WATER

Simultaneous analysis of pyrethrins (Py-I and Py-II) and piperonyl but oxide (PBO) in soil and runoff water samples following field applicati on of new pyrethrum formulation containing pyrethrins (Py's) and PBO i s described. Residues of total Py's and PBO were extracted from soil s amples using hexane-acetone (9:1). A solid phase extraction (SPE) colu mn containing C-18-octadecyl bonded silica was used to separate Py's a nd PBO residues from runoff water. Residues in soil and water were qua ntitated by high performance liquid chromatography (HPLC) equipped wit h C-18-column and a UV detector. Concentration of Py-IT in soil was 10 0 times higher than that of Py-I Ih following treatment and 9.6 times higher than in runoff surface water 11 days following treatment. Resul ts indicated that Py's are non-persistent in soil (even though lipophi llic) and water when applied at the recommended rate of 6 Ibs (5.31 g A.I.) per acre. There was a consistent decrease in total Py's residues as time after spraying increased. Py's residues in soil decreased fro m 0.91 to 0.11 ppm 4 days following treatment and one month after trea tment only 0.002 ppm were detected. The highest concentration of Py's in runoff water was 36.09 ng/liter following the first rainfall ill da ys following treatment). PBO initial residues detected in soil samples were low (0.84 mu g/g soil) while no residues of PBO were detected in runoff water.