FormNo. 203-821-244 01/05-REV0
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1
Separation Science Application Note
GCxGC
OrganochlorinePesticides
byGCxGC-ECD
Introduction
United States Environmental Protection AgencyMethod (EPA) 8081 uses gas chromatography–
electron capture detection (GC-ECD) to quantify organochlorine pesticides (OCPs) in extracts from
solid and liquidmatrices. Themethod includes a parallel dual-column option inwhich the GC is
configuredwith one injection port, directing extracts to two different GC columns that terminate in
two ECDs. This configuration helps to confirm quantified values that are obtainedwhen a
non-specific detector such as the ECD is used. Conversely, biases that arise due to pesticide
coelutions with interferences are illuminated.
A relatively newway to solve separation problems is to use comprehensive two-dimensional GC
(GCxGC). GCxGC is away to increase peak capacity by applying two independent separations to a
sample in one analysis with one detector. Typically, GCxGC involves a serial column configuration
(differing phases) separated by a thermal modulator. A separation is performed on the first
column, and then effluent from the first column is continually (and quickly) focused and "injected"
onto the second column. By keeping the second column short, a series of high-speed
chromatograms are generated, and the first column separation can bemaintained. Separation
results can be plotted as a retention plane (column 1 time x column 2 time), also known as a
contour plot. By usingGCxGC, the chances for coeluting interferences are reduced, and an analogy
can be drawn between GCxGC and parallel dual-column analysis.
This application note describes a comparison of OCP results obtained from a parallel dual-column
GC-ECDmethod and a GCxGC-ECDmethod. Soil andwater extracts were quantified using the
external standardmethod.
Standards
The standards were obtained from Restek and contained the followingOCPs: aldrin, alpha-
chlordane, alpha-hexachlorocyclohexane (HCH), beta-HCH, DDD, DDE, DDT, delta-HCH, dieldrin,
endosulfan I, endosulfan II, endosulfan sulfate, endrin, endrin aldehyde, endrin ketone, gamma-
chlordane, gamma-HCH, heptachlor, heptachlor epoxide, andmethoxychlor. Decachlorobiphenyl
(209) and tetrachloro-m-xylene (TCMX) were also in the standards and serve as surrogate
compounds for method 8081.
The standards were diluted in hexane to achieve the following concentrations (in pg/µL) for
calibration curves.
• HCHs, heptachlors, aldrin, chlordanes, endosulfans (5, 10, 20, 40, 80)
• 209, TCMX, dieldrin, endrins, endosulfan sulfate, DDT compounds (10, 20, 40, 80, 160)
• Methoxychlor (50, 100, 200, 400, 800)
