|Marek, Le Etta - UNIVERSITY OF MINNESOTA|
|Bresnahan, Gail - ND STATE UNIVERSITY|
Submitted to: Pittsburgh Conference
Publication Type: Abstract Only
Publication Acceptance Date: March 8, 1999
Publication Date: N/A
Technical Abstract: Some of the newer classes of herbicides are polar, nonvolatile, and applied at low rates, less than 100 g/ha. This combination of factors makes analysis difficult at the trace levels necessary to monitor their environmental fate in soil (1.0 mg/kg) and water (0.1 mg/L). For instance, to analyze clethodim, a cyclohexanedione oxime herbicide, it is first oxidized to a diacid and then derivatized, both steps involving clean-up, prior to GC analysis with a flame photometric detector. However, this method is nonselective and the results will include another related herbicide, sethoxydim, and their metabolites if present in water or soil. HPLC-UV has also been used to analyze these compounds. However, analysis by HPLC-UV is not sufficiently sensitive and provides no confirmation of these herbicides. We have successfully used a liquid chromatograph-electrospray- mass spectrometer (LC-ES-MS) for the multi-residue analysis of the cyclohexanedione oxime herbicides clethodim, sethoxydim, and alloxydim and selected metabolites in water. After solid phase extraction of the herbicides from water, a Hewlett Packard LC-ES-MS was used for the analyses. Without further cleanup, detection levels of less than 0.5 mg/L in water were obtained using SIM. This method also unambiguously confirms the three herbicides and selected metabolites in water. Details of the multi-residue method will be provided.