## 3 Extraction and Analytical Methods
### Extraction Techniques  
Different types of processes are used according to the type of matrix to be investigated in the sample pretreatment and phthalate extraction process. These extraction techniques can be resumed as solid-liquid extraction, solid-phase extraction, liquid-liquid extraction, and various others, as well as hybrid techniques [34; 35; 39]. Solid-liquid extraction (SLE) is a technique in which phthalates are extracted from the solid matrix through a solvent. This type of extraction can be performed by Soxhlet apparatus, ultrasonic bath, or mixing elution. Soxhlet is a technique that allows the extraction of analytes from solid materials used when the compound to be extracted has a limited solubility in the chosen solvent and the impurities are insoluble in it [35]. This extraction is not very common for the determination of phthalates and has the advantage that it does not need to be continuously monitored; in addition, it saves the solvent (e.g., cyclohexane, dichloromethane, or methanol) as the latter circulates continuously in the chamber to perform the extraction process [35]. However, the disadvantage lies in the long period of time required for the extraction process, which can be reduced with the temperature rise [35; 40]. Unfortunately, in the case of complex organic matrices, the process may result in a high amount of analytical interference due to the matrix effect, and consequently the low recovery of analytes [41]. Moreover, on column, purification processes can be required. Regarding liquid analyses, to date, solid-phase extraction (SPE) and liquid-liquid extraction (LLE) are used and further developed to promote extraction quality and cleanliness [35]. Solid-phase extraction (SPE) is the technique of extraction, purification, and concentration of analytes, best known and used for chemical analysis in different sectors (clinical, environmental, pharmaceutical, and food). The extraction process is based on the interaction of analytes to be extracted (affinity difference between analyte and interference),present in a matrix/liquid phase with the solid phase called adsorbent (usually polymer matrix) present in the cartridge [42]. This technique saves time and solvents and can be prepared in semi- or full automation. Thanks to these advantages and practical operation, it is widely used, especially for water samples, in which the activated solid phase is used to extract PAEs from water samples and eluted with organic solvent [34; 43]. In particular, the process can be divided into a preliminary phase of filtration of the water sample followed by four steps to be carried out in the cartridges: conditioning/equilibration, load (sample addition), washing, and elution [37]. The cartridges used for PAEs' extraction generally consist of short columns (made of polyethylene (PE) or polypropylene (PP)) containing sorbents (such as C18, octadecylsilane (ODS), HLB, etc.) that can have different sizes of porosity (usually 50-60 \(\upmu\)m) [34]. Another type of SPE is the magnetic SPE, a low environmental impact technique with good sensitivity that uses a solution of a magnetic carbon nanotube based on dispersed iron. This technique can be automated in combination with gas chromatography, favouring low LOD (3.1-37 ng/L for 16 PAEs) [44]. Another similar technique called the dispersive graphene SPE (DSPE) uses graphene as a nanomaterial or a false adsorbent with a microsphere, printed with a magnetic molecule (MAG-MIM), in which organic desorption solvents are usually acetonitrile, acetone, ethyl acetate, and n-hexane [45]. Solid-phase microextraction (SPME) is also considered a green technique as it is solvent-free and includes the absorption of analytes on a microfiber coated with a hydrophilic polymer, such as polydimethylsiloxane/divinylbenzene (PDMS/DVB), divinylbenzene/carboxon/polydimethylsiloxane (DVB/CAR/PDMS), and polyacrylate (PA) fibres [46].