A high performance liquid chromatographic method employing
two columns connected in series and separated~y·a.switching
valve has been developed for the analysis of the insecticide/
nematicide oxamyl (methyl-N' ,N'-dimethyl-N-[(methylcarbamoyl)
oxy]-l-thiooxarnimidate) and two of its metabolites.
A variation of this method involving two reverse phase columns
was employed to monitor the persistence and translocation of
oxamyl in treated peach seedlings. It was possible to
simultaneously analyse for oxamyl and its corresponding oxime
(methyl-N',N'-dimethyl-N-hydroxy-l-thiooxamimidate}, a major
metabolite of oxamyl in plants, without prior cleanup of the
samples. The method allowed detection of 0.058 pg oxamyl and
0.035 p.g oxime. On treated peach leaves oxamyl was found to
dissipate rapidly during the first two-week period, followed
by a period of slow decomposition. Movement of oxamyl or its
oxime did not occur in detectable quantities to untreated
leaves or to the root or soil.
A second variation of the method which employed a size
exclusion column as·the first column and a reverse phase
column as the second was used to monitor the degradation of
oxamyl in treated, planted corn seeds and was suitable for
simultaneous analysis of oxamyl, its oxime and dimethylcyanoformamide
(DMCF), a metabolite of oxamyl. The method
allowed detection of 0.02 pg oxamyl, 0.02 p.g oxime and
0.005 pg DMCF. Oxamyl was found to persist for a period of
5 - 6 weeks, which is long enough to permit oxamyl seedtreatment
to be considered as a potential means of protecting
young corn plants from nematode attack. Decomposition was found to be more rapid in unsterilized soil than in sterililized
soil.
DMCF was found to have a nematostatic effect at high
concentrations ( 2,OOOpprn), but at lower concentrations
no effect on nematode mobility was observed. Oxamyl, on the
other hand, was found to reduce the mobility of nematodes
at concentrations down to 4 ppm
