Validation of Pyrithiobac Sodium (Staple® Herbicide) ELISA for Australian Cotton Soils

Abstract

An enzyme‐linked immunosorbent assay (ELISA) for pyrithiobac‐sodium (Staple®) produced by DuPont was validated in Australian soils. This pyrithiobac‐sodium ELISA was shown to be highly sensitive with the limit of detection of 4–5 ppt. Soil samples were extracted either in PBS buffer by shaking or by accelerated solvent extraction (ASE). While pyrithiobac sodium can be analyzed directly by ELISA after ASE extraction with 1/10 or more dilutions, the analysis of PBS extract required filtration and dilution 1/20 or more depending on the concentration. Immunoassay results compared favorably with GC‐MS results for both ASE and PBS extract of incurred residue of pyrithiobac sodium in soil samples, indicating that this ELISA can be an inexpensive and reliable alternative to conventional residue analysis methods for quantification of pyrithiobac‐sodium. This validation provided the basis for applying the ELISA to a field study of pyrithiobac‐sodium.

Keywords:

• ELISA
• Validation
• Soil
• Pyrithiobac sodium

Acknowledgments

We are grateful to J.C.Strahan (DuPont, USA) for her valuable discussions concerning pyrithiobac sodium ELISA, and A.Netting (School of Biochemistry and Molecular Genetics, University of New South Wales) for his help in mass spectrometric confirmation of pyrithiobac sodium samples.