Fast GCUsingPressureTunableSelectivity
Apowerful technique for separating complexmixtures, developedbySacks, et. al.
1,2
at theUniversity ofMichigan, uses pressure-tunable selectivity anda series-coupled
columnensemble. In this technique (Stop-FlowGC), two standard-dimension
capillary columnswith dissimilar stationary phases are connected in series, usinga4-
way junction. At this junctionpoint, a sourceof carrier gas also is connected, with the
pressure controlledby anexternal ElectronicPressureControl (EPC) unit. An
external valve controls the flowof the carrier gas to the junctionpoint. Adetector is
connected to the fourthport of the junction, andmonitors the components as they
elute from the first column.
Whenan injection ismade, the sample componentsmove through the first and
second columns. Thereare4possible scenarios for closely-eluting compoundsA
andB:
(1) AandBare resolvedafter passing throughboth columns
(2) AandBare not resolvedafter the first column, but are resolvedafter the second
column
(3) AandBare resolvedafter the first column, but not after the second column
(4) AandBare not resolvedafter either column
