Gas chromatographic detection systems are subject to two main sources of interference: solvent elution and liquid phase bleed. Solvent elution, especially with large injection volumes, often produces undesirable tailing, over-loading or fouling of detector, and flame extinguishment. Column liquid phase bleed causes detector and combustion tube contamination which may result in lost sensitivity, anomalous behavior and catalyst poisoning. The described problems would be solved by a system which would vent solvent, shunt column bleed, and maintain continuous detector equilibrium. Dual columns can be connected to a single detector in the usual manner with or without installation of a by-pass valve.