Alternative green solvents in cloud point extraction methods: recent developments, challenges, and greenness evaluation

Abstract

The cloud point extraction (CPE) approach has received a lot of interest, and many studies and reviews have already been written on this topic. The CPE is a good separation technique even at ultra-trace analyte levels. The researchers proposed numerous adjustments to make it environmentally friendly, affordable, and precise. Several reviews were handled in conventional CPE, but no analysis was offered that evaluated new CPE procedures based on green solvent-assisted surfactants and evaluated greenness scores. The present study tries to address the observed issue. This overview looks at the clouding phenomena and the applicability of CPE techniques that use green solvents. These approaches involve mixed-micellar media CPE (MM-CPE), ionic liquids CPE (IL-CPE), rapid synergistic CPE based on deep eutectic solvents (RS-DES-CPE), and others. They are simple to apply, efficient, fast, and safe. Also, they are reducing the heating step, chemical amounts, and extraction time compared with the conventional CPE methods. Additionally, the mechanisms and interactions of green solvents and surfactants were discussed. The green solvent selection website and three recent greenness tools have been described, such as Sample Preparation Metric of Sustainability (SPMS), Complex Modified GAPI (ComplexMoGAPI), and Analytical Greenness Metric of Sample Preparation (AGREEprep). Also, a critical comparison was made between the greenness ratings of CPE approaches. In this overview, we present readers with classified descriptions and comparison of CPE forms that with green solvent-assisted surfactants to help them acquire the knowledge they need for future CPE design. In addition, multiple limitations and potential patterns were introduced.