Asahipak GF-310 HQ (an Aqueous/Organic (multi-solvent use) SEC column) was used for an analysis of anionic surfactant. Anionic surfactants are often used in textile industries and as household detergents. The anion part of the compound works as a surfactant when ionized in a solvent. There are two types of sodium dodecylbenzensulfonate; linear type (soft type) and branched type (hard type). From an environmental pollution point of view, it is important to distinguish the two, since each type has different biodegradability and accumulation factors. GF-310 HQ is feasible for distinguishing the soft and hard types without any complexity. There is no considerable difference in peak shapes of soft and hard types when analyzed at a mobile phase containing 60% acetonitrile (Eluent I). However, analysis at lower acetonitrile concentration provides hydrophobic interaction affects and this creates differences in the peak shapes of soft and hard types, thus they can be distinguished (Eluent II and III).