PURPOSE: To reduce contamination from plastic members in a liquid chromatograph device by removing aromatic material and/or olefinic material from dispersion solution before adding the dispersion solution to a plastic basic material.

CONSTITUTION: To use an analysis measuring device to be brought into contact with liquid, dispersion solution is added to a plastic base material, and extrusion of the plastic basic material added with the dispersion solution is carried out to thereby produce plastic members. Before the addition of dispersion solution thereto, an aromatic material and/or an olefin material is removed from the solution. To remove the same therefrom by a chenical reaction, chlorosulfone acid is added to the solution. The plastic members are tubes or films while the plastic basic material is polytetrafluoroethylene, and the solution is a gasoline fraction.