FormNo. 203-821-244 01/05-REV0
LECO is a registered trademark of LECO Corporation
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Samples
Soil andwater extracts were obtained fromSevern Trent Laboratories, STL Burlington, in
Colchester, Vermont. Soil was extracted using EPAMethod 3550, ultrasonic extraction.
Additionally, gel permeation chromatographywas applied to the soil extracts using EPAMethod
3640. Water was liquid-liquid extracted in a separatory funnel according to EPAMethod 3510. Both
soil andwater extracts were subjected to Florisil column clean-up following EPAMethod 3620.
Experimental Conditions
Parallel Dual-ColumnGC-ECD
Column 1:
30m x 0.32mm x 0.50 µm Rtx-CLPesticide (Restek)
Column 2:
30m x 0.32mm x 0.42 µm Rtx-CLPesticideII (Restek)
Carrier:
Hydrogen at 2.8mL/min, constant flow
Injection:
2 µL direct at 200°C
Oven Program:
120°C (1min), 16°/min to 210°, 13°/min to 245°, 12.5°/min to 300° (4min)
Total Run Time:
17min
Detector:
ECD, 300°C, argon/methanemakeup gas at 140mL/min
LECOGCxGC-ECD
Agilent 6890 GC-ECD equippedwith a LECOQuad Jet—Dual-Stage Thermal Modulator
Column 1:
9m x 0.18mm x 0.20 µm Rtx-5 (Restek)
Column 2:
1m x 0.18mm x 0.20 µm Rtx-200 (Restek)
Carrier:
Helium at 2mL/min, constant flow
Injection:
1 µL split at 250°C, split ratio 50:1
Oven 1 Program:
50°C (0.2min), 30°/min to 140°, 5°/min to 250°
Oven 2 Program:
50°C offset from oven 1
Modulation:
Temperature offset 30°C from oven 1, time 6 sec.
Total Run Time:
25.2min
Detector:
ECD, 325°C, N2makeup gas at 148mL/min, 50Hz
DataProcessing
LECOChromaTOF
®
software was used to automatically peak find and quantify organochlorine
pesticides analyzedwith GCxGC-ECD.
Analysis of StandardswithGCxGC-ECD
Figure 1 is a contour plot of an OCP standard analyzedwith GCxGC-ECD. Note that the X-axis
represents the first dimension retention time, and the Y-axis shows the second dimension retention
time (the actual retention times are recorded in Table 1). Peak intensity, as defined by detector
response, is represented by a color scheme from blue (zero, or baseline detector response) to red
(most intense response). Each "spot" represents a peak (and pesticide). Figure 2 demonstrates the
power of GCxGC by showing how beta- and gamma-HCH, which coelute on Rtx-5 (in the first
dimension), are separated by Rtx-200 in the second dimension.
Another way to visualize GCxGC data is with a surface plot (illustrated in Figure 3). In this plot, the
Z-axis represents peak intensity (as defined by ECD response).
