Cloud Point Extraction and Spectrophotometric Determination of Sulfide in Water Samples using Ethylene Blue Formation Reaction

A rapid, selective, and sensitive cloud point extraction process using mixed micelle of a nonionic surfactant, Triton X-114, and an anionic surfactant, SDS, to extract sulfide from aqueous solutions was investigated. The method is based on the color reaction of sulfide with N,N-diethyl-p-phenylenediamine (DPD) in the presence of suitable oxidizing reagent (Fe3+) in acid media and cloud point extraction of ethylene blue (EB) dye. Various factors and optimal extraction and reaction conditions like: acid, Fe3+, reagent, and surfactant concentration were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, RSD%) were obtained. Linearity was obeyed in the range of 1-100ng mL-1 of sulfide ion. The detection limit of the method is 0.5ng mL-1 of sulfide ion. The interference effect of some anions, cations, and neutral species was also tested. The method was applied to the determination of sulfide in spring, river, and waste water samples.