FormNo. 203-821-258 02/05-REV0
LECO is a registered trademark of LECO Corporation
1
Separation Science Application Note
Pegasus
®
GC-TOFMS andGCxGC-TOFMSof
OrganophosphatePesticides inAsh Leaves
Introduction
Organophosphate pesticides such as Chlorpyrifos, Diazinon, andMalathion are sometimes used on
ornamental plants to control nuisance insects. Monitoring these plants for the insecticides can be a
challenge because the residual levels are often small and thematrix (the plant material) is
chemically complex. This note describes the analysis of an ash leaves extract for Chlorpyrifos,
Diazinon, andMalathion by Gas Chromatography—Time-of-Flight Mass Spectrometry (GC-TOFMS)
and comprehensive two-dimensional GC-TOFMS (GCxGC-TOFMS). Advantages offered by
automated peak find and spectral deconvolution routines are discussed, and the benefit of
enhanced peak capacity for complex samples is shown.
Sample Extraction
An ash leaves extract was prepared by the United States Department of Agriculture in Gulfport,
Mississippi.
Experimental Conditions
GC-TOFMS
GC: Agilent 6890 Gas Chromatograph
Column:
20m x 0.25mm x 0.71 µm Rtx-TNT (Restek)
Carrier:
Helium at 2mL/min, constant flow
Injection:
1 µL splitless at 250°C, valve time 60 sec.
Oven Program:
80°C (1min), 20°/min to 340°
MS: LECO Pegasus
®
TOFMS
Ionization:
Electron ionization at 70 eV
Source Temperature: 225°C
StoredMass Range: 45 to 550 u
Acquisition Rate:
20 spectra/sec.
GCxGC-TOFMS
GCxGC: Agilent 6890Gas Chromatograph equippedwith a LECOGCxGC Thermal Modulator
and Secondary Oven
Column 1:
10m x 0.18mm x 0.20 µm Rtx-5 (Restek)
Column 2:
2m x 0.10mm x 0.10 µm Rtx-PCB (Restek)
Carrier:
Helium at 0.7mL/min, constant flow
Injection:
1 µL splitless at 275°C, valve time 60 sec.
Oven 1 Program:
80°C (1min), 10°/min to 300°
Oven 2 Program:
35°C offset from oven 1
Modulation Time:
3 sec.
