Application of ionic liquids for extraction of phenolic compounds and dyes: A critical review

Environmental pollution is a one of the most popular and challenging dilemma that faces science community today. Natural weathering and industrialization sectors such as textile, printing, iron-steel, petroleum, pesticides, paper, pharmaceuticals, and painting, to name the few are the main sources of dye and phenolic compound pollutants. The widely investigated sample preparation methods for dyes and phenolic compounds are liquid–liquid extraction (LLE), liquid–liquid microextraction (LLME), solid phase extraction (SPE), and solid phase microextraction (SPME). However, to minimize the use of organic solvents and to achieve Green Chemistry Principles in the above listed sample preparation methods, ionic liquids have been extensively investigated. Therefore, the current evaluates various sample preparation methods that have been developed for the extraction of dyes and phenolic compounds in various matrixes. The published literature reports show that, imidazolium-based ionic liquids are the mostly investigated solvents in LLE, SPE, and in biphasic extraction (BPE) of phenols and dyes. Additionally, it was observed that dyes preferred SPE prior to spectrophotometric determination, while phenolic compounds were mostly determined by using LLE followed by high performance liquid chromatography (HPLC) analysis. However, the variation in miscibility of ionic liquids makes the sample preparation technology in analytical chemistry to have a wider development. Therefore, more innovative developments using ionic liquids are highly expected for the determination of phenols and dyes in various matrices.