Switchable solvent-based micro-extraction of pesticides in food and environmental samples

Switchable solvents are new generation solvents that are environmentally friendly and can be used for the effective pre-concentration of pesticide residues in food and environmental matrices. They have physico-chemical properties that can be switched abruptly and reversibly between two opposite forms. The common switchable solvents used commonly during pesticide pre-concentration involve polarity switch. Such solvent switch between hydrophobic and hydrophilic forms during pesticide pre-concentration. Secondary and tertiary amines are typical switchable hydrophilicity solvents. The amines are hydrophobic but they abruptly and reversibly switch to their hydrophilic forms on addition of CO₂ to them. The application of amine-based switchable solvents during pre-concentration of pesticide residue in food and environmental samples are discussed in this paper. Medium-chain fatty acids can also be used as switchable solvents. Their switch between hydrophobic and hydrophilic forms is usually triggered by pH changes. Applications of fatty acid-based switchable solvents during pre-concentration of pesticide residues are reviewed in this paper. Switchable solvent-based micro-extraction can be combined with other pre-concentration techniques to enhance selectivity resulting in clean chromatograms. This paper has a section dedicated to the application of hyphenated switchable solvent-based micro-extraction techniques during pre-concentration of pesticides in food and environmental samples. In addition, the challenges associated with the use of switchable solvents during micro-extraction of pesticide residues are also discussed.