FormNo. 203-821-258 02/05-REV0
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5
Deconvoluted
spectrum
Library
spectrum
Deconvoluted
spectrum
Library
spectrum
Malathion
Chlorpyrifos
Figure5.
TOFmass spectra from the GCxGC analysis of Malathion and Chlorpyrifos in an ash
leaves extract. The similarities versus library spectra are greater than 900 (out of 999).
One observation for the spectrum of Malathion producedwith GCxGC of ash leaves was the
absence of the 167 ion (frommatrix) that was present in the deconvoluted spectrum for the one-
dimensional analysis. Figure 6 helps illuminate the reason behind this, which simply put, is the
increased separating power availablewith GCxGC. Close inspection of the GCxGC portion of this
figure (or of the contour plots in Figures 3 and 4) will reveal that the GCxGC peaks, due to thermal
focusing close to the detector, are only about 100-200ms wide at their base. Because the peaks
are so narrow, TOFMS, which can acquire data at up to 500 spectra/second, is the onlymass
spectrometer appropriate for GCxGC.
167 Interference
Malathion
GCxGC
GC
Figure6.
Linear chromatograms for one-dimensional (GC) and two-dimensional (GCxGC) analyses
of Malathion in ash leaves. Malathion coeluteswith a largematrix peak inGC, but is easily
separated from this same compound using GCxGC.
