PURPOSE: To simply and accurately measure the content of alcohol, in the analysis of alcohol in gasoline due to gas chromatography, by separating a component by the sorbitol column of the first stage to apply predetermined treatment thereto and introducing the residual specimen into the porous polymer beads column of the second stage to separate the same.

CONSTITUTION: An apparatus is constituted of the first stage consisting of a sample gasifying chamber 1, a sorbitol column 2 and a pressure controller 3, the second stage consisting of a resistor 5, a porous polymer beads column 6 and a detector 7 and the four-way valve 4 connecting both stages. At first, gasoline is introduced into the gasifying chamber 1 and a component is separated by the sorbitol column 2 and the residual component is introduced into the second column 6 at the point of time when a C8 aromatic component is eluated. The four-way valve 4 and the pressure controller 3 play an important part in the change-over of flow passages and the content of alcohol in gasoline of a high octane value containing alcohols can be simply and accurately measured by this method.