Abstract: This invention makes a rapid and accurate anion separation analysis possible by using an electric conductivity detector built in a chromatographic apparatus and a binary composite solution as an eluent. The binary composite solution: borax and an aliphatic acid/an aromatic acid/a saccharic acid/a sugar is used in alkaline regions, while the binary composite solution: a sulphonic acid and boric acid/a monocarboxylic acid is used in acid regions. Over a conventional analysis employing phthalic acid or benzoic acid singly, this analysis has an advantage in capturing a wider variety of anions on chromatograph with high accuracy in more sensitized condition without suffering a hindrance due to noises or peaks having nothing to do with objective anions because the electric conductivity of the eluent itself is very low.