Spectrophotometric determination of anionic surfactants by conversion of the leuco-bases of triphenylmethane dyes

Abstract

A one-phase, one-reagent, spectrophotometric technique is reported for the detection and determination of anionic surfactants of the sulfonate and sulfate types. Both applications are based on conversion of the colorless leuco-bases of triphenylmethane dyes (Brilliant Green and methyl violet) to colored (quinoid) forms by the anionic surfactants. The quantitative method, in the absorption and reflectance modes, is applicable to anionic surfactants in the 0–1500 ppm range; the spectrophotometric procedure can be automated. Residual surfactant can be detected at the 0.01% level on the surface of cellulosic products.