FormNo. 203-821-259 02/05-REV0
LECO is a registered trademark of LECO Corporation
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MS: LECO Pegasus TOFMS
Ionization:
Electron ionization at 70 eV
Source Temperature: 200°C
StoredMass Range: 35 to 450 u
Acquisition Rate:
100 spectra/second
Experimental Conditions for PBDEStandard
GCxGC-TOFMS
GCxGC: Agilent 6890Gas Chromatograph equippedwith a LECOGCxGC thermal modulator and
secondary oven
Column 1:
9.5m x 0.18mm x 0.20 µm Rtx-5 (Restek)
Column 2:
1m x 0.25mm x 0.25 µm Rtx-Dioxin 2 (Restek)
Carrier:
Helium at 1.5mL/min, constant flow
Injection:
1 µL direct injection at 250°C, 4mmUniliner (Restek)
Oven 1 Program:
120°C (1min), 10°/min to 340° (2min)
Oven 2 Program:
20°C offset from oven 1
Modulation Time:
3 seconds
MS: LECO Pegasus TOFMS
Ionization:
Electron ionization at 70 eV
Source Temperature: 225°C
StoredMass Range: 200 to 1000 u
Acquisition Rate:
50 spectra/second
DataProcessing
LECOChromaTOF software.
Results andDiscussion
To reduce processing time for GCxGC-TOFMS data, it is often desirable to process only part of the
chromatogram. Figure 1 is a contour plot, or GCxGC chromatogram, of a PIANOmix that ismarked
with yellow lines to illustrate an example of limited data processing. The only area of interest in
this example is the first dimension retention time region, approximately 1850 to 3550 seconds,
which contains the C
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-C
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benzenes. ChromaTOF already contains segmented processing capability
that allows peak finding for only this region (Figure 2), which can reduce the overall processing
time.
Resample is a recently added ChromaTOF feature that allows segmented processing by creating a
new file for the desired retention time region, with the added benefits of choosing a sample
reduction rate (acquisition rate), and/or restricting themass range for the new file. The sample
reduction rate allows a user to create a file of, for example, 50 spectra/second acquisition rate
from one of 100 spectra/second, which cuts the file size in half and can speed processing. The nice
thing about this part of the feature is that the "extra" spectra are not thrown away, but are instead
summed to produce a signal-to-noise enhancement. Mass range restriction, in addition to
decreasing file sizewhich leads to processing time improvement, may have the added benefit of
improving spectral deconvolutionwhen lower (or higher)m/z ions are discarded that are only from
matrix interferences.
