A vacuum jacketed gas line adaptor with a flange cover for an existing pipeline sample take-off probe encasing a sample line and hermetically sealed to a vacuum valve housing having an sealable access port and containing a vented bleed valve and a block valve, fluidly connected to the sample line and a length of vacuum jacketed tubing sealing connected to the valve housing and in vacuum communication therewith, where the vacuum jacketed tubing surrounds the sample line to provide thermal isolation from the ambient for the sample line to a sample vaporizer.