Octylamine-oxalic acid (Oct-Oxa) deep eutectic solvent for the separation of Sudan II from food samples.

This work presents a novel deep eutectic solvent (DES) formed of octylamine and oxalic acid (Oct-Oxa) that was effectively used to separate Sudan II dye from food and water samples. The prepared DES was characterized using Fourier transform infrared spectroscopy (FT-IR) and carbon-13 nuclear magnetic resonance (C NMR). Key parameters were optimized, including a short ultrasonication time of 30 s and a very low DES volume of only 500 μL that could be separated within one minute of centrifugation. The remaining parameters were also tested: pH (7), DES molar ratio (1:1), and sample volume (40 mL). The method demonstrates excellent recovery and accuracy, with limits of detection (LOD) of 1.2 μg kg and quantification (LOQ) of 4.1 μg kg. It facilitates rapid separation and sensitive detection of Sudan II dye using ultraviolet-visible (UV-VIS) spectrophotometry. The novelty of this approach lies in the use of a novel DES, the minimal volume of DES required, and the efficiency of the short ultrasonication time, highlighting the method's potential for sustainable, cost-effective extraction in environmental and food safety applications.