Selective determination of triton-type non-ionic surfactants by on-line clean-up and flow injection with spectrophotometric detection

Abstract

A flow injection method is proposed for the determination of Triton-type non-ionic surfactants, employing reagent injection and spectrophotometric detection. The method is based on the reaction between these surfactants and alizarin fluorine blue. Interferences from ionic and amphoteric surfactants were eliminated by selective retention on a column containing an ion-exchange resin inserted in the flow system, whereas interferences from non-ionic surfactants were eliminated by selective retention on a column containing Amberlite XAD-4 adsorption resin followed by elution of the Triton-type surfactants. Beer's law is obeyed at 432 nm in the ranges 0.2–12.0 mg l^–1 and 2.0–120 µg l^–1 of Triton-type surfactants, with relative standard deviations (n= 10) of 5.7 and 0.49%, respectively. The validity of the proposed method was tested by the analysis of several samples and by an analysis of variance (ANOVA) statistical comparison with two other methods.