Miniaturization and Automation in Green Sample Preparation

Amongst the different steps of any analytical procedure, sample preparation is considered to be one of the most critical. Currently, efforts are centred in the development of miniaturized extraction techniques, which make use of efficient extraction sorbents/solvents and reduce organic solvent and/or energy consumption, following the principles of Green Analytical Chemistry (GAC). Extraction techniques can be divided into sorbent- and solvent-based approaches, each one of them with numerous variants which allow a wide range of applications in different fields. In the first case, solid-phase microextraction and micro-solid-phase extraction are the two main types, whereas solvent-based microextraction techniques are mainly subdivided into single-drop microextraction, hollow-fibre liquid-phase microextraction, and dispersive liquid–liquid microextraction. Interestingly, many efforts have been made with the objective of achieving full/partial automation of these extraction techniques to overcome many of the issues that arise from human errors. Overall, although both solvent- and sorbent-based techniques have been automated, sorbent-based ones are still ahead; nonetheless, solvent-based extraction techniques have seen an important increase in momentum in recent years.