Naphthalene-1-sulfonic acid sodium salt is used as a detection reagent to investigate ion-pair high-performance liquid chromatographic retention behavior of copper(II)-1-oxa-4,7,10,13-tetraazacyclopentadecane complex. It is also used to prepare naphthalene-1-sulfonyl chloride by reaction with phosphorousoxy chloride. Further, it is used as a stationary liquid phase for resolution of dichlorophenol isomers by gas chromatography.