Flow injection determination of anionic surfactants based on the solvatochromism of p-diphenylaminoazobenzene sulfonate

Based on the solvatochromism of a commercially available azo dye, p-diphenylaminoazobenzene sulfonate (PDABS), a flow injection (FI) method for the determination of anionic surfactants (0-4x10(-5) M) was established. Determination was carried out directly in aqueous solutions with a sampling rate of 60 h(-1), a detection limit (S/N=3) of 2x10(-7) M anionic surfactant and a relative standard deviation of 0.9% at 2x10(-5) M Sodium dodecylbenzenesulfonate (DBS) (n=11). The proposed method was applied to determine anionic surfactants in washing powders. The results agree well with that obtained by the Epton titrimetric method.