|Marek, Le Etta - MN DEPT OF AGRICULTURE|
|Bresnahan, Gail - NORTH DAKOTA STATE UNIV|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 2, 2000
Publication Date: N/A
Interpretive Summary: Some of the newer classes of herbicides have properties that make their analysis difficult at the trace levels (mg/kg) necessary to monitor their environmental fate in soil, water, and air. For instance, cyclohexanedione oxime herbicides such as alloxydim, clethodim, and sethoxydim are applied at 100 to 300 g/ha to control grasses in soybean, sugarbeet, and oilseed rape. Early attempts to study the fate of these herbicides in soil have relied on bioassay and traditional gas and liquid chromatographic (HPLC) techniques, which have had limited success. A limitation of these methods is the lack of confirmation of the herbicide or metabolite. A promising method for these newer classes of herbicides is HPLC/electrospray/mass spectroscopy (LC/ES/MS). We developed a multiresidue method for the simultaneous determination of alloxydim, clethodim, sethoxydim, and two metabolites in water by LC/ES/MS. The percent recoveries for the three herbicides were > 88% with a limit of detection < 0.05 mg/L. There was no evidence of decomposition of clethodim and sethoxydim during the extraction and analysis. LC/ES/MS provides the confirmation and limits of detection necessary for a multiresidue method, which should also be appropriate for other cyclohexanedione oxime herbicides. Scientist and regulatory agencies now have a method to monitor their environmental fate in soil, water, and air.
Technical Abstract: A multiresidue method for the determination of alloxydim, (methyl 2,2- dimethyl-4,6-dioxo-5-[1-[2-propenyloxy)amino]buthylindene]cyclo- hexanecarb oxylate), clethodim (E,E)-(+/-)-2-[1-[[3-chloro-2-propenyl) oxy]imino]propyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one), and sethoxydim ((+/-)-2-[1-(ethoxyimino)butyl]-5-[2-ethylthio)propyl]-3- hydroxy-2-cyclohexen-1-one) and two metabolites, clethodim sulfoxide ((E,E)-(+/-)-2-[1-[[3-chloro-2-propenyl)oxy]imino]propyl]-5-[2- (ethylsulfinyl)propyl]-3-hydroxy-2-cyclohexen-1-one) and sethoxydim sulfoxide ((+/-)-2-(ethoxyimino)butyl]-5-[2-ethylsulfinyl)propyl]-3- hydroxy-2-cyclohexen-1-one) in water by high performance liquid chromatography/electrospray/mass spectrometry (LC,ES/MS) is reported. River water and distilled water were spiked at 0.8 mg L**-1 with all three herbicides, which were then extracted from the water by C18-SPE. The herbicides and metabolites were quantified and confirmed using selected ion monitoring. The percent recoveries were as follows alloxydim, 117 +/- 11%, clethodim, 96 +/- 14%; sethoxydim, 89 +/- 13%. There was no evidence of oxidation of clethodim and sethoxydim during the extraction to their respective sulfoxides. The limit of quantitation was < 0.05 mg L**-1. We have shown that we can analyze and confirm three cyclohexanedione oxime herbicides and two metabolites in water by LC/ES/MS. This multiresidue method should also be appropriate for other cyclohexanedione oximes.