To concentrate alkylamine or alkylammonium in a dilute soln. to quantitatively analyze the same by ion chromatography.

A concn. process connecting a concn. column 6 being a cation exchange column to an ion chromatography analyser using an ion exchange column 8 and an electric conductivity detector through a passage changeover valve and passing a sample soln. through the concn. column 6 in a sample introducing stage of a usual ion chromatography analyzing method to hold org. alkylamine and org. alkylaminomium contained in the sample soln. to the concn. column 6 and a separation process separating org. amine and org. ammonium held to the concn. process from the concn. column 6 to introduce them into an analyzing column 8 are added.