Residue levels of pyrethrins and piperonyl butoxide in soil and runoff water

Abstract

Simultaneous analysis of pyrethrins (Py‐I and Py‐II) and piperonyl butoxide (PBO) in soil and runoff water samples following field application of a new pyrethrum formulation containing pyrethrins (Py's) and PBO is described. Residues of total Py's and PBO were extracted from soil samples using hexane‐acetone (9: 1). A solid phase extraction (SPE) column containing C₁₈‐octadecyl bonded silica was used to separate Py's and PBO residues from runoff water. Residues in soil and water were quantitated by high performance liquid chromatography (HPLC) equipped with C₁₈‐column and a UV detector.

Concentration of Py‐II in soil was 100 times higher than that of Py‐I 1h following treatment and 9.6 times higher than Py‐I in runoff surface water 11 days following treatment. Results indicated that Py's are non‐persistent in soil (even though lipophillic) and water when applied at the recommended rate of 6 lbs (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 from 0.91 to 0.11 ppm 4 days following treatment and one month after treatment only 0.002 ppm were detected. The highest concentration of Py's in runoff water was 36.09 ng/liter following the first rainfall (11 days following treatment). PBO initial residues detected in soil samples were low (0.84 μg/g soil) while no residues of PBO were detected in runoff water.

Key words:

• Total pyrethrins
• PBO
• SPE cartridge
• HPLC
• persistence

Notes

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