FormNo. 203-821-250 01/05-REV0
LECO is a registered trademark of LECO Corporation
4
77
110
110
Equal concentration
standardmix
Aroclor 1254
4
1A
1B
1B
Figure1.
Contour plots of (1A) standardmix containing equal concentrations of PCBs 110 and the
dioxin-like PCB 77 and (1B) Aroclor 1254. As calculated from the study of Frame et. al, PCB 110 is
at 325 pg/µL in the Aroclor 1254 dilution, while PCB 77 only has a concentration of 1.05 pg/µL.
The selectivity of GCxGC-ECD for dioxin-like PCBs, evenwhen they are in the presence of bulk
PCBs in an Aroclor, has been adequately demonstrated by the data in Table 3, except for PCB 77.
In this case, a better chromatographic separationmay be necessary to determine this PCB in an
unbiased fashion should PCB 110 be elevated in the same sample. To further demonstrate the
selectivity of GCxGC-ECD for dioxin-like PCBs, the Aroclor 1254 dilutionwasmademore complex
by spiking it with an organochlorine pesticide (OCP)mix that contained aldrin, chlordanes, DDD,
DDE, DDT, dieldrin, endosulfans, endosulfan sulfate, endrin, endrin aldehyde, endrin ketone,
heptachlor, heptachlor epoxide, hexachlorocyclohexanes, andmethoxychlor at 100 pg/µL for each
pesticide. In environmental samples it is not unusual to find OCPs with PCBs, which complicates the
determination of both species. Table 4 demonstrates that the OCPs did not interferewith the
determination of dioxin-like PCBs in an Aroclor mix, highlighting the selectivity of the GCxGC-ECD
technique.
