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polymer [74]. In this last case, a lab-synthesized β-cyclodextrin-poly(N-isopropylacrylamide) (β-CD-PNIPAM) polymer was used to carry out the extraction of three short-chain PAEs from tap and mineral water. This kind of polymers are characterized by showing a reversible phase transition in aqueous samples at a certain temperature known as low critical solution temperature (LCST). In this case, the LCST is at 32°C, so the polymer behaves as a liquid below that value while it is a solid when the temperature exceeds it. Taking advantage of this fact, the authors introduced 20 mL of β-CD-PNIPAM into the sample and mixed. Then, the temperature was increased up to 50°C obtaining a floating solid phase, which was collected after Na2SO4 addition in order to favor the salting-out effect. This extraction methodology, in combination with GC-MS, allowed obtaining good extraction efficiency and sensitivity, especially for DBP, which makes think about the potential of this procedure for the determination of long-chain PAEs. It is important to mention that, from an operational point of view, the use of this kind of polymers implies that the extraction step is developed in the same way as a LLE procedure and, as consequence, it could be not considered as a sorbent-based extraction methodology for some authors. However, the second part involve a desorption of the analytes from the solid polymer, since that reversible phase transition just takes place when it is into the water sample. In order to provide a better vision of this procedure, Figure 1.5 shows a scheme of a similar procedure used by Chen et al. in a previous work for the determination of different phenolic compounds—no PAEs were included [75].
Table 1.2 Some examples of the application of SPE for the analysis of PAEs in water samples.
| PAEs | Matrix (sample amount) | Sample pretreatment | Separation technique | LOQ | Recovery study | Residues found | Comments | Reference |
| DMP, DEP, DIBP, DBP, DMEP, BMPP, DEEP, DNPP, DHXP, BBP, DBEP, DCHP, DEHP DNOP, and DNP | River and sea waters (20 mL) | dSPE using 3 mL colloidal G and vortex for 2 min, centrifugation at 3800 rpm for 5 min, and desorption with 5 mL ethyl acetate and 2 g sodium sulfate by vortex for 30 s | GC-MS | 5–20 μg/L | 72–117% at 20 and 50 μg/L | Nine river and 2 sea waters samples were analyzed and contained at least 1 PAE at levels from 2 to 78 μg/L | Ethyl acetate showed higher extraction efficiency than ACN, acetone and hexane as desorption solvent | [72] |
| DEHP | Rain, lake and river waters (600 mL) | dSPE using 20 mg GO-MIP and agitation for 30 min, centrifugation at 12000 rpm for 10 min, and desorption (twice) with 2.5 mL acetone by vortex for 1 min and subsequent sonication for 5 min | HPLC-UV | 2.82 μg/L | 82-92% at 5, 50, and 500 μg/L | One sample of each water were analyzed and residues were found at 0.32 ± 0.08 and 1.56 ± 0.32 μg/L in lake and river waters, respectively. | DEHP was used as the template molecule. Acetone showed higher extraction efficiency than MeOH as desorption solvent | [69] |
| DMP, DEP, DBP, BBP, DEHP, and DNOP | Bottle water (200 mL) | dSPE using 60 mg DMIMs and stirring for 90 min, and desorption with 5 mL dichloromethane by sonication for 15 min | GC-MS | 1.03–1.35 μg/L | 92.4–99.0% at 25 μg/L | Two samples were analyzed and residues of DEHP were found at 10.06 ± 0.84 and 11.90 ± 1.70 μg/L | DEP was used as the dummy template. Dichloromethane showed higher extraction efficiency than acetone, MeOH, chloroform, ethyl acetate and hexane as desorption solvent. DMIMs-dSPE method showed higher recovery values compared with non-imprinted polymers | [73] |
| DMP, DEP, and DBP | Tap and mineral waters (20 mL) | dSPE using 20 mg (β-cyclodextrin-poly (N-isopropylacrylamide) and water bath at 50°C for 25 min., addition of sodium sulfate for polymer condensation purposes, and desorption with 200 μL ethyl acetate by sonication for 15 min. | GC-MS | 0.021–0.350 μg/L | 82.2–105.6% at 5, 100, and 600 μg/L | One sample of each water were analyzed and all PAEs were found at levels from 0.14 to 4.97 μg/L | Ethyl acetate showed higher extraction efficiency than hexane, acetone and dichloromethane as desorption solvent. | [74] |
| BBP, DBEP, DIPP, DNPP, DCHP, DEHP, DNOP, DINP, and DEHA | Milli-Q, pond, tap and waste waters (50 mL) | dSPE using 120 mg Basolite* F300 MOF and shaking for 5 min, vacuum-dried using a SPE column for 30 min, and elution with 15-mL ACN | HPLC-MS | 0.022–0.069 μg/L | 70–118% at 0.375 and 1.875 μg/L | Eight samples were analyzed and residues of DEHP were found at levels from 0.21 ± 0.26 to 4.04 ± 0.23 (_ig/L in all samples | ACN showed higher extraction efficiency than dichloromethane, acetone, cyclohexane and MeOH as elution solvent | [25] |
| DMP, DEP, DPP, DIBP, DBP, DNPP, DHXP, BBP, DEHP, DHP, DCHP, DPhP and DNOP | Drinking water (200 mL) | m-dSPE using 20 mg MWCNTs-m-NPs under agitation for 2 min, a magnet was used for decantation, and elution with 1 mL toluene–acetone (1:4, v/v) | GC-MS/MS | 0.03–0.1 μg/L | 86.6-100.2% at 5 μg/L | Three samples were analyzed and no residues were detected | Toluene showed higher extraction efficiency than acetone, MeOH, hexane and ethyl acetate as elution solvent. To reduce the toxicity of toluene, different proportions toluene-acetone (1:1, 1:4 and 1:9, v/v) were tested and the mix toluene–acetone (1:4, v/v) gave similar results | [76] |
| DEP, DPP, DBP, DCP, and DEHP | Bottled and river waters (300 mL) | m-dSPE using 25 mg G-Fe3O4 under 3 4 agitation for 15 min, a magnet was used for decantation, and elution (in triplicate) with 0.5 mL acetone by vortex for 10 s | HPLC-UV | 0.03–0.1 μg/L | 80.0–106.0% at 0.5 and 5 μg/L | One sample of each water were analyzed and residues of DBP and DEHP were found at 0.12 and 0.15 μg/L, respectively, in the river water sample | Acetone showed higher extraction efficiency than MeOH and ACN as elution solvent. Coca-Cola and green tea samples were also analyzed | [78] |
| DMP, DEP, DAP, DIBP, and BBP |
