A separable electrical isolator for coupling two pieces of conductive tubing carrying high pressure cryogenic gas includes a gas-impervious dielectric spacer with a bore in which the pieces of tubing are sealed axially-aligned in fluid communication with an electrically-nonconductive gap between them. A pair of complementary coupling members are rigidly attached to the pieces of tubing to define outwardly-extending annular flanges that are each sealed about the periphery of a corresponding one of the pieces in a position slightly set back from an end of the piece. Each flange has an annular rib protruding from it toward the end of the piece. The coupling members are separably and nonconductively interconnected with the annular ribs applying compressive force to the spacer to thereby effect the seal.