Potentiometric Flow Injection Analysis of Anionic Surfactants in Industrial Products and Wastes

Abstract.

A new sensor for anionic surfactants with a membrane consisting of 33 wt% poly(vinyl chloride) (PVC), 66 wt% dioctylphthalate (DOP) plasticizer, and 1 wt% tridodecylmethylammonium chloride (TDMAC) is developed and used for flow injection analysis. The sensor displays a working response range of 5×10⁻⁷–5×10⁻³ M dodecylbenzene sulfonate (DBS⁻) with a Nernstian slope of 58.5±0.2 mV decade⁻¹, a response time of 30 s and a detection limit of 1.5×10⁻⁷ M DBS⁻. Selectivity measurements with different anionic species indicate good membrane selectivity towards DBS⁻. The sensor is used to measure anionic surfactants (DBS⁻) in different wastewater samples, commercial detergent products, and for monitoring the rate of surfactant biodegradation in sewage treatment plants. The results obtained agree fairly well with data obtained by the standard extraction-spectrophotometric method. The proposed potentiometric method offers the advantages of simplicity, accuracy, automation feasibility, and applicability to turbid and colored sample solutions.