Extraction of Synthetic Food Dyes with Trioctylmethylammonium Salicylate

The trioctylmethylammonium salicylate ionic liquid has been studied for the extraction and preconcentration of anionic synthetic food dyes (SFDs) Azorubine (AZR), Fast Green (FG), Sunset Yellow (SY), Allura Red (AR), Red 2G (R2G), and Tartrazine (TAR) from aqueous solutions. All SFDs are quantitatively extracted into the ionic liquid at pH 1.8–8.0 in the presence of sodium chloride (2–10 wt %) and in the absence of sodium chloride at pH 7.0–11.0 in 1 min. The values of the distribution coefficient (logD) were 2.9 ± 0.2, 2.9 ± 0.2, 3.4 ± 0.2, 3.2 ± 0.1, 3.3 ± 0.1, and 3.5 ± 0.2 (pH 8–9) for AZR, SY, FG, AR, R2G, and TAR, respectively. A procedure for the extraction–spectrophotometric determination of the SFDs (0.05–2.75 mg/L) is proposed; the limits of detection are 0.02, 0.004, 0.01, 0.01, 0.01, and 0.02 mg/L for AZR, FG, SY, AR, R2G, and TAR, respectively. The method was used to determine the dyes in beverages and other samples.