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 (0–4 × 10−5 M) was established. Determination was carried out directly in aqueous solutions with a sampling rate of 60 h−1, a detection limit (SN = 3) of 2 × 10−7 M anionic surfactant and a relative standard deviation of 0.9% at 2 × 10−5 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.