In short, there are several strategies proposed in the literature
for analyte extraction [27,28], involving liquid-liquid extraction (LLE)
[29–31] and solid-phase extraction (SPE) [32,33]. LLE and SPE are
the most widely used techniques for the extraction of liquid samples.
In the first type, an appropriate selection of the extraction solvent
permits removal of the analyte fromthe original solution to the new
phase, directly or after a previous derivatization.