SeparationRequirements
Dioxins andFurans
Chromatographic resolution and analysis times are dependant on column dimensions (length, i.d., phase thickness). The table
below summarizes a number of column options for the analysis of dioxins/furans. The conventional 60M 5% diphenyl column
is assigned a relative analysis time of 1. Experimentally it has been determined that 175,000 plates are required to obtain the
necessary separation of 2,3,7,8-TCDD from its nearest neighbors (1,2,3,7/1,2,3,8-TCDD unresolved pair eluting before, and
1,2,3,9-TCDD eluting after). This criterion can be easilymet on both the 40M, and the 60M columns, however, the analysis
can be completed in nearly½ of the time on the 40M column. The 20M column is also capable ofmeeting these requirements
in about ¼ of the time, however, there is little room for trimming the columnwhen the column performance begins to deterio-
ratewith use. For the dioxin and furan analysis, therefore, a 40M columnwas selected for thiswork.
PCBs
In order tominimize the number of ions that must be simultaneouslymonitored, it is desirable to elute the bulk of the PCB
compounds prior to the elution of the dioxin and furan compounds. This can be accomplished by injecting the non-coplanar
PCB fraction into a 20M column that is parallel to the 40M column used for the separation of the dioxin/furan fraction.
ColumnConfiguration
Columns are installed in parallel into anMS ion source, withPCB fraction being injected onto the 20M column, and the di-
oxin/furan fraction being injected onto the 40M column. Resulting analysis time is less than a single fraction on the conven-
tional 60M column.
