INFICON Explorer Portable Gas Chromatograph - Manual (Page 284)

Assay 1 User Notes
282
Figure 21 Column B Compounds on the PID
Figure 22 Column B Compounds on the ECD
The light compounds are analyzed on Column C, with Column A acting as the
precolumn. As before, the mid-range and heavy compounds are prevented from
entering Column C by adjusting the backflush time. In this case only the light
compounds are allowed to pass from Column A to Column C, all other compounds
are backflushed out of the system. No real separation of the light compounds occurs
on Column A. All of the separation occurs on Column C.