In this study, aqueous two-phase systems (ATPSs) containing a cationic and anionic surfactants mixture were used for the preconcentration of the synthetic food dyes Allura Red AC, Azorubine, Sunset Yellow, Tartrazine, and Fast Green FCF. A rapid, simple, low cost, affordable, and environmentally friendly methodology based on microextraction in ATPSs, followed by spectrophotometric/colorimetric determination of the dyes, is proposed. The ATPSs are formed in mixtures of benzethonium chloride (BztCl) and sodium N-lauroylsarcosinate (NaLS) or sodium dihexylsulfosuccinate (NaDHSS) under the molar ratio close to equimolar at the total surfactant concentration of 0.01–0.20 M. The density, viscosity, polarity, and water content in the surfactant-rich phases at an equimolar ratio BztCl:NaA were determined. The effects of pH, total surfactant concentration, dye concentration, and time of extraction/centrifugation were investigated, and the optimum conditions for the quantitative extraction of dyes were established. The smartphone-based colorimetric determination was employed directly in the extract without separating the aqueous phase. The analytical performance (calibration linearity, precision, limits of detection and quantification, reproducibility, and preconcentration factor) and comparison of the spectrophotometric and smartphone-based colorimetric determination of dyes were evaluated. The method was applied to the determination of dyes in food samples and food-processing industrial wastewater.

An aqueous biphasic system (ABS) based on tetrabutylammonium bromide (TBABr) with ammonium sulfate as a salting-out agent was used to extract synthetic food dyes from aqueous solutions. Conditions for the preparation of the TBABr–H ₂ O–(NH ₄ ) ₂ SO ₄ ABS for microextraction preconcentration of Allura Red, Tartrazine, Azorubine, Sunset Yellow, and Fast Green were optimized: tetrabutylammonium bromide, 0.075 M and ammonium sulfate, 33 wt %. The recovery of all of the dyes was no lower than 97% at pH 2.3–9.5 for 1 min. Filtration through nonwoven polypropylene was used to facilitate phase separation and extract isolation. The concentrate was eluted with distilled water, and the dyes in the eluate were determined by spectrophotometry. The limits of detection were 0.02, 0.03, 0.03, 0.04, and 0.02 mg/L for Allura Red, Azorubine, Tartrazine, Sunset Yellow, and Fast Green, respectively. The procedure was applied to determine dyes in drinks, a mouthwash, an Easter kit for dyeing eggs, and the drug Ibuprofen.

The simultaneous dissolution of tetraoctylammonium bromide and sodium N-lauroyl sarcosinate in water leads to the in situ formation of a water-immiscible ionic liquid, tetraoctylammonium N-lauroyl...

The distribution of 4-(2-pyridylazo)resorcinol, PAR (5 × 10–4–1 × 10–2M) in the systems tetraoctylammonium N-lauroylsarcosinate (TOALS)–water and trioctylmethylammonium salicylate (TOMAS)–water is...