Over the past two decades, greater attention has been paid to the use of chemical processes in an environmentally and human friendly way to suit green chemistry approaches. The latter goal consists of designing chemical processes to either reduce or eliminate hazardous substances, as guided by the 12 Principles of Green Chemistry [1]. In this context, new analytical procedures have been developed to protect people’s health and to eliminate, or at least reduce, the negative impact of chemical products (e.g., organic solvents) on the environment [1–3]. Much effort has been made to develop green analytical separation methods, especially with the advent of ultra-high performance liquid chromatography (UHPLC), capillary electrophoresis (CE) and supercritical fluid chromatography (SFC), which use significantly reduced quantities of organic solvents. For complex matrices or at very low analyte concentrations, the sample preparation step is considered to be the most polluting step of the analytical process [2,4]. Liquid–liquid extraction (LLE) and solid-phase extraction (SPE) are widely used for sample clean-up and analyte preconcentration; however, large volumes of hazardous organic solvents that are harmful to both humans and the environment are required for these extractions. Therefore, new sample preparation techniques have been developed over the last few years that (i) replace the toxic organic solvents used and (ii) reduce solvent consumption [4]. For the former, toxic solvents can be replaced with alternative, nontoxic extraction agents, such as supercritical fluids (supercritical fluid extraction, SFE), ionic liquids, superheated water (subcritical water extraction, SWE) and surfactants (cloud point extraction, CPE). For the latter, recent investigations have focused on developing miniaturised sample preparations that drastically reduce solvent consumption (i.e., microextraction techniques) [5] or extract the analyte of interest without a solvent (