Simultaneous Preconcentration of Fast Green FCF and Rhodamine B Using Deep Eutectic Solvent and Determination via High-Performance Thin Layer Chromatography

The aim of the current investigation is the development of a green, quick, easy, and accurate method for simultaneous preconcentration of fast green FCF (FG) and rhodamine B (Rh B) using a deep eutectic solvent (DES). Then, the high-performance thin layer chromatography (HPTLC) technique was used for the determination of analytes. Decanoic acid and tetrabutylammonium bromide were chosen as the components of DES. HPTLC analysis was performed on an aluminum plate silica gel 60 F₂₅₄. Methanol-ammonia and ethyl acetate were selected as the mobile phase. Scanning of the plates was accomplished by scanner 3. Effective parameters on the preconcentration process such as concentration of salt, volume of DES, stirrer time, and pH were investigated via central composite design (CCD). Data validation demonstrated good repeatability. The limit of detection for FG and Rh B was obtained as 0.08 and 0.01 µg·mL⁻¹, respectively. The enrichment factor for FG and Rh B was achieved as 7.43 and 10.77, respectively. The linear ranges for FG and Rh B were acquired as 0.10–1.20 and 0.05–1.20 µg·mL⁻¹, respectively. The preconcentration factor for both analytes was 21.66. Finally, the proposed method was successfully used for the quantitation of FG and Rh B in pastille and lipstick.