## 3 Extraction and Analytical Methods
### Extraction Techniques
However, a few studies in the literature use this technique (also online, with mass analysers), so it is still under development and has been shown to be effective only for some phthalates [34]. Stir bar sorptive extraction (SBSE) is another green method based on the extraction of organic compounds such as phthalates from aqueous samples without the use of solvents or concentration phases. The method consists of the extraction of solutes by adsorption in a polymer made up of PDMS that covers a stir bar [34; 47]. Solid-phase extraction, liquid-liquid extraction (LLE), and LLE-similar are the most widely used methods for the determination of phthalates [35]. Liquid-liquid extraction is a method used for the extraction of analytes in aqueous samples by organic solvent, for example, hexane and dichloromethane (DCM) [34; 48]. Shaking the mixture vigorously promotes the extraction of analytes. After decantation, a separation will be obtained between the aqueous phase and the organic phase (not miscible), containing phthalates that will then be collected and analysed while the aqueous solution can be subjected again to the process to improve the recovery of the analytes [49]. In addition, it is possible to add organic modifiers such as methanol to have a better extraction efficiency of most non-polar PAEs such as DEHP and DnOP [50], and the separation process can be improved by coupling sonication, centrifugation, and freezing [34]. Despite the ease of application, the LLE procedure requires a large amount of organic solvents with environmental and economic consequences [51]. Solid-supported LLE (SLE), considered a hybrid method between SPE and LLE, is a technique in which an aqueous sample initially interacts with a cartridge divided with a sorbent in diatomaceous earth that retains both analytes and matrix components, subsequently, the PAEs are then selectively eluted through into an immiscible organic solvent [52]. A similar method using very low volumes (a few microlitres) of immiscible substances is called liquid-phase microextraction (LPME), which can be combined with different extraction processes that maximise its effectiveness [34; 52]. These microextraction techniques include single-drop microextraction (SDME), hollow-fibre LPME (HF-LPME), dispersive liquid-liquid microextraction (DLLME) and its different forms (ultrasound-assisted dispersive liquid-liquid extraction (UA-DLLME), ultrasound-vortex-assisted dispersive liquid-liquid microextraction (USVA-DLLME), and magnetic stirring-assisted dispersive liquid-liquid microextraction (MSA-DLLME)), and cold-induced aggregation microextraction (CIA-ME) [34]. Another method that takes advantage of the distribution balance of the two phases is the microporous membrane LLE (MMLLE). This method allows the automation of the micro-LLE process on a PP membrane that permits the entry of the aqueous phase together with the organic solvent [50]. Following the same chemical principle in the homogeneous liquid-liquid extraction (HLLE), the area of contact between two phases (water and organic solvent) is extremely large, consenting a rapid attainment of repartition equilibrium [34]. Among the increasingly used methods for the determination of pollutants, the quick, easy, cheap, effective, rugged, and safe (QuECHERS) technique has taken significant importance in recent years [53]. The QuECHERS procedure involves a series of methods aimed at solving all problems due to the heterogeneous nature of the sample (for example, long extraction times due to several passages, large quantities of solvents to be used, etc.) [53; 54; 55] and can be used to extract compounds from a solid and liquid matrix. The process consists of the transfer of analytes from solid or liquid samples to the extraction phase. After sample homogenisation, an initial extraction with acetonitrile is carried out, followed by a phase of buffer salts\" addition and centrifugation [54]. Then, the supernatant will be purified (removing the interferents) through the dispersive solid-phase microextraction (d-SPME) [53; 54].