SPE (dSPE), and magnetic dSPE (m-dSPE), among others. The extraction ability to quantitatively and selectively extract these target analytes will be commented and discussed.
1.2 Solid-Phase Microextraction
SPME has been the sorbent-based microextraction technique most used for the analysis of PAEs in water samples (see Table 1.1) probably, among other reasons, because it allows to reduce the risk of PAEs contamination during sample extraction with respect to other conventional extraction techniques. On the one hand, the absence of organic solvents and additional steps reduces PAEs background levels. On the other, water is in many occasions a simple and clean matrix that contains few interferences, so the direct immersion (DI) mode can be used without hardly any impairment of its lifetime (except for waste waters or marine water). Moreover, in SPME, extraction, pre-concentration and direct desorption into analytical instruments can be easily integrated in most cases.
The first studies in which SPME was applied for PAEs extraction from water samples dealt with the direct application of commercial fiber coatings, including polydimethylsiloxane (PDMS), polyacrylate (PA), PDMS-divinylbenzene (DVB), carboxen (CAR)-PDMS, and carbowax (CW)-DVB. As examples, Cao [21] demonstrated the better performance of PDMS-DVB fibers compared to PDMS and DVB-CAR-PDMS fibers for the headspace (HS) SPME extraction of nine PAEs (DMP, DEP, DIBP, DBP, BBP, DHXP, DEHA, DEHP, and DNOP) from bottled water samples, while Polo et al. [28] found that PDMS-DVB fibers also give higher extraction efficiency than PDMS, PA, CAR-PDMS, and CW-DVB fibers for DBP, BBP, and DNOP, but CAR-PDMS and PA fibers show a better extraction performance for DMP and DEP, and for DEHP, although the first one provided better results for simultaneous analysis of the target PAEs from bottled, industrial harbor, river, urban collector, and influent and effluent waste water samples. As expected, the optimal SPME fiber for the extraction of a particular phthalate depends on both the properties of the coating and the PAEs since these compounds differ from each other in terms of polarity and volatility and, therefore, on their distribution between the fiber coating and the matrix. In addition, low-molecular PAEs are more volatile than those of high-molecular weight [38]. As a result, low-molecular PAEs would be expected to be more efficiently extracted when HS mode is used [38]. However, they have a certain solubility in water and, as consequence, they volatilize very slowly from this kind of matrices. Contrary, although high-molecular PAEs are less volatile, they have a lower water solubility and they volatilize faster at higher temperatures than it could be expected [38]. Accordingly, it has been observed that DEHP and DNOP are extracted from different water samples more efficiently than BBP, DEP, and DMP using HS-SPME [28, 39]. Nevertheless, most of the works published on this topic are based on DI-SPME instead of HS-SPME.
Table 1.1 Some examples of the application of SPME and SBSE for the analysis of PAEs in water samples.
| PAEs | Matrix (sample amount) | Sample pretreatment | Separation technique | LOQ | Recovery study | Residues found | Comments | Reference |
| SPME | ||||||||
| DMP, DEP, DBP, BBP, DEHP, and DNOP | Mineral, river, industrial port, sewage, and waste waters (10 mL) | SPME using a PDMS-DVB fiber, stirring at 100°C in DI mode for 20 min, and desorption at 270°C for 5 min | GC-MS | 0.0067–0.34 μg/L | 87–110% at 0.5 and 2.5 μg/L | One sample of each water were analyzed and contained all PAEs at levels from 0.011 to 6.17 μg/L | A multifactor categorical design was used for optimization purposes. PDMS-DVB fiber showed higher extraction efficiency than PDMS, PA, CAR-PDMS and CW-DVB fibers for DBP, BBP, and DNOP, but CAR-PDMS for DMP and DEP, and PA for DEHP. DI-SPME provided better sensitivity than HS mode | [28] |
| DEHA, DMP, DEP, BBP, DIBP, DBP, DHXP, DEHP, and DNOP | Mineral water (10 mL plus 10 or 30% w/v NaCl) | SPME using a PDMS-DVB fiber, stirring at 90°C in DI mode for 60 min, and desorption at 270–280°C for 5 min | GC-MS | - | - | Eleven samples were analyzed and residues of DEP, DIBP, DBP, and DEHP were found at levels from 0.052 to 1.72 μg/L | PDMS-DVB fiber showed higher extraction efficiency than PDMS and DVB-CAR-PDMS fibers | [21] |
| DPP, DBP, DIBP, and DNPP | Mineral and tap water (10 mL) | SPME using a MWCNTs-PPy fiber, stirring at room temperature in DI mode for 60 min, and desorption at 250°C for 25 min | GC-FID | 0.17–0.33 μg/L | 90–113% at 5 and 50 μg/L | Three mineral water samples and 1 tap water were analyzed and contained at least 1 PAE at levels from 0.6 to 7.90 μg/L, except 1 of the mineral water samples | - | [40] |
| DMP, DEP, DBP, DAP, and DNOP | Mineral, tap and reservoir waters (12 mL plus 10% w/v NaCl) | SPME using a MIP fiber, stirring at 60°C in DI mode for 30 min, and desorption at 250°C for 10 min | GC-MS | 0.0072–0.069 μg/L | 94.54–105.34% | One sample of each water were analyzed and contained at least 2 PAEs at levels from 0.07 to 0.53 μg/L | DBP was used as the template molecule. MIP fiber showed higher extraction efficiency than a non-imprinted polymer fiber, and PDMS, PA and CW-DVB fibers | [45] |
| DMP, DEP, DBP, BBP, DEHP, DINP, and DNOP | Water (5 mL plus 6% w/v NaCl) | SPME using a PA fiber, stirring at room temperature in DI mode for 50 min, and desorption at 270°C for 2 min | GC-MS | 0.007–0.027 μg/L | - | Six samples were analyzed and contained at least 2 PAEs at levels from 0.4 to 78.8 μg/L | PA fiber showed higher extraction efficiency than PDMS fiber. Urine was also analyzed | [95] |
| DIBP, DBP, BMPP, DNPP, DHXP, BBP, DCHP, DEHP, DIPP, DNOP, and DINP | River and tap waters (- mL) | SPME using a bamboo charcoal fiber, stirring at room temperature in DI mode for 20 min, and desorption at 280°C for 10 min | GC-MS | 0.013–0.067 μg/L | 61.9–87.1% at 0.1, 0.5, and 1 μg/L | One sample of each water were analyzed and no residues were detected | Bamboo charcoal fiber showed greater extraction efficiency than PDMS, PDMS-DVB and PA fibers for DNOP and DINP, but lower for DIBP, DBP, and DNPP | [47] |
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DBP, DIBP,
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