PNNL-13501 - Pacific Northwest National Laboratory

m/z Arbitrary Units
Figure 1. Mass spectrum of silylated-trichloropyridinol
m/z
209,210
254,256
Figure 2. Mass Spectrum of silylated-2-isopropyl-4-methyl-
6-hydroxypyrimidine
One-half of a solution of metabolized chlorpyrifos was
extracted and derivatized for trichloropyridinol. The
resulting concentration was approximately 2 ppm and the
oxon was not detected. Another sample containing equal
concentrations of chlorpyrifos and diazinon was extracted
and derivatized for trichloropyridinol. The concentration
for trichloropyridinol was 2 ppm. The results indicated
good reproducibility. Concentrations were based on the
response of a standard. A duplicate sample was extracted
and analyzed for chlorpyrifos and chlorpyrifos-oxon, but
no peaks were detected. These preliminary results
suggested, under these reaction conditions and
concentrations of analytes, that the metabolism of
chlorpyrifos was not inhibited by the presence of
diazinon. These results also indicated complete
metabolism of chlorpyrifos to trichloropyridinol.
Summary and Conclusions
We developed analytical methods for analyzing
chlorpyrifos, diazinon, associated oxons, and metabolites
and concluded that
• the components can be extracted and analyzed at low
concentrations with very good reproducibility
• electron ionization with selected ion monitoring may
not be the most sensitive method for detection
(negative ion electrospray ionization mass
spectrometry may be better)
• the metabolism of chlorpyrifos was not inhibited by
the presence of diazinon under test conditions and
concentrations
• further studies will be needed at lower concentrations
to verify lack of inhibition.
Publication and Presentation
Campbell, JA, TS Poet, GM Mong, and C. Timchalk.
June 2000. “In vitro metabolism study with a mixture of
the organophosphate insecticides chlorpyrifos and
diazinon.” Presented at the 48 th ASMS Conference on
Mass Spectrometry and Allied Topics, Long Beach,
California. In Proceedings of 48 th ASMS Conference on
Mass Spectrometry and Allied Topics (in press).
Analytical and Physical Chemistry 5