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1.2 Solid-Phase Microextraction
ОглавлениеSPME 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] |
| DBP, DIBP, BBP, and DEHP | Mineral water (9 mL plus 20% w/v NaCl) | SPME using a TiO2 NPs fiber, stirring at 30°C in DI mode for 75 min, and desorption at 285°C for 5 min | GC-FID, GC-MS | 0.17–0.40 μg/L | 86–107% at 2μg/L | One sample was analyzed and residues of DIBP and DEHP were found at 1.0 and 2.2 μg/L, respectively | TiO2 NPs fiber showed better extraction efficiency than PDMS and poly(3,4-ethylenedioxythiophene)-TiO2 fibers. DI-SPME provided better sensitivity than HS mode | [39] |
| DMP, DEP, DBP, and DEHP | Mineral, river and tap waters (15 mL) | SPME using a SiO2-PDMS-MWCNTs fiber, stirring at 40°C in DI mode for 30 min, and desorption at 280°C for 2 min | GC-FID | 0.033–0.067 μg/L | 79.62–109.3% at 10 μg/L | One sample of each water were analyzed and residues of DBP and DEHP were found at 5.26 and 8.47 μg/L, respectively, in the mineral water sample | SiO2-PDMS-MWCNTs fiber showed better extraction efficiency than PDMS, PA and DVB-CAR-PDMS fibers | [43] |
| DPP, DIBP, DBP, DNPP, BBP, and DEHP | Mineral and tap waters (10 mL) | SPME using a poly-o-aminophenol-MWCNTs fiber, stirring at 35°C in DI mode for 60 min, and desorption at 280°C for 2 min | GC-FID | 0.10–0.25 μg/L | 91–115% at 5 and 50 μg/L | Three mineral water samples and 1 tap water sample were analyzed and contained at least 2 PAEs at levels from 0.3 ± 0.02 to 8.1 ± 0.19 μg/L, except for 1 mineral water sample | NaCl and dextrose injection solutions were also analyzed | [42] |
| DBP, BBP, DEHA, DEHP, and DNOP | Tap, barreled drinking and pond waters (10 mL plus 15% w/v NaCl) | SPME using a PS-MWCNTs fiber, stirring at room temperature in DI mode for 60 min, and desorption at 280°C for 5 min | GC-MS/MS | 0.0038-0.059 μg/L | 73.4-103.8% at 0.05 and 0.2 μg/L | One sample of each water were analyzed and contained at least 1 PAE at levels from 0.038 ± 0.004 to 0.060 ± 0.007 μg/L | A Box-Behnken design was used for optimization purposes | [41] |
| DPP, DBP, DEHA, and DEHP | Mineral, tanked and tap waters, and boiling water exposed to a PET container (10 mL plus 30% w/v NaCl) | SPME using a G-PVC fiber, stirring at 70°C in HS mode for 35 min, and desorption at 230°C for 4 min | GC-FID | 0.2–0.3 μg/L | 88–108% at 10 and 20 μg/L | One sample of each water were analyzed and residues of DPP and DBP were found at 2.1 and 1.8 μg/L, respectively, only in the boiling water exposed to a PET container | A central composite design was used for optimization purposes. Sunflower and olive oils were also analyzed | [20] |
| DMP, DEP, DIBP, DBP, DMEP, BMPP, DEEP, DNPP, BBP, DHXP, DBEP, DCHP, DPhP, DEHP, DNOP, and DINP | Sea water (10 mL) | SPME using a PDMS fiber, stirring at 35°C in DI mode for 40 min, and desorption at 40°C for 6 min | GC-MS | 0.00017–0.0011 μg/L | 68.0–114.0%, but 55.4% for DMP, at 100 and 300 μg/L | Eleven sample was analyzed and contained at least 9 PAEs at levels from 0.270 to 1.39 μg/L | Sediment was also analyzed by conventional SPE | [96] |
| DEP, DIBP, DBP, BBP, and DEHP | River, bottled and mineral waters (4 mL plus 20% w/v NaCl) | SPME using a polyamide6-MnO fiber, stirring at 80°C in HS mode for 30 min, and desorption at 200°C for 5 min | GC-μ-ECD | 0.13–0.64 μg/L | 90.3–106% at 10 and 100 μg/L | One sample of each water were analyzed and residues of DEP, DIBP and DBP were found at levels from 9.24 to 29.3 μg/L, respectively, in the bottle and mineral waters | Polyamide6-MnO fiber showed better extraction efficiency than PDMS fiber. Soda was also analyzed | [44] |
| DMP, DEHP, DBP, DNPP, BBP, and DNOP | Tap and sea water (20 mL adjusted at pH 4) | SPME using a GO-1-(3-aminopropyl)-3-vinyl imidazolium bromide/tetrafluoroborate fiber, stirring at 35°C in DI mode for 30 min, and desorption at 175°C for 5 min | GC-MS | 0.017–0.10 μg/L | 87.6–101.2% at 1 and 5 μg/L | One sample of each water were analyzed, and no residues were detected | GO-1-(3-aminopropyl)-3-vinyl imidazolium bromide fiber showed higher extraction efficiency than GO-1-(3-aminopropyl)-3-vinyl imidazolium tetrafluoroborate, PA and CAR-PDMS fibers. Coffee was also analyzed | [52] |
| DEP, DPP, DAP, DBP, BBP, and DEHP | Water (- mL plus 20% w/v NaCl) | SPME using a OH-TPB-COFs fiber, stirring at 105°C in HS mode for 50 min, and desorption at 250°C for 7 min | GC-FID | 0.11–1.50 μg/L | 78.6–101.9% at 1 and 5 μg/L | Three sample were analyzed and contained at least 4 PAEs at levels from 1.39 to 5.78 μg/L | OH-TPB-COFs fiber showed better extraction efficiency than PDMS fiber | [46] |
| DMP, DBP, DINP, DEP, BBP, DEHP, DNOP, and DIDP | Mineral water (9 mL) | IT-SPME using AC-PS-DVB monolithic columns, and desorption with 1.5 mL ACN | CE-DAD, UHPLC-UV | 0.59–9.83 μg/L | 78.8–104.6% at 50 μg/L | One sample was analyzed, and no residues were detected | AC-PS-DVB monolithic column showed better extraction efficiency than AC-poly(BMA-EDMA) monolithic column. ACN showed higher extraction efficiency than MeOH as desorption solvent. | [62] |
| DMP, DEP, DAP, BBP, DBP, DNPP, and DCHP | Disposable tableware, plastic cup and river waters (45 mL plus 2% v/v MeOH) | IT-SPME using PDA-melamineformaldehyde aerogel-carbonfiber tube, and desorption with MeOH-water for 0.6 mL | HPLC-DAD | 0.07–0.16 μg/L | 77–120% at 10 and 15 μg/L | One sample of each water were analyzed and residues of DAP, BBP and DNPP were found at levels from 0.12 to 0.99 μg/L in the water in plastic cup | PDA-melamineformaldehyde aerogelcarbon-fiber tube showed better extraction efficiency than melamine-formaldehyde aerogel-carbon-fiber and bare carbon-fiber tubes | [23] |
| SBSE | ||||||||
| DMP, DEP, DBP, BBP, DEHP, and DNOP | Sea and esturiane waters (20 mL plus 30% w/v NaCl and 20% v/v MeOH) | SBSE using a PDMS stir bar, stirring at room temperature for 60–200 min, and thermal desorption at 300°C for 10 min | GC-MS | 0.0003–0.063 μg/L | 95–124% at 0.1 μg/L | One river water sample and 2 estuarian water samples were analyzed and contained all PAEs at levels from 0.0036 ± 0.0004 to 1.314 ± 0.018 μg/L | A Plackett–Burman and 2 central composite designs were used for optimization purposes. 6 polycyclic aromatic hydrocarbons, 12 polychlorinated biphenyls and 3 nonylphenols were also analyzed | [65] |
| DMP, DEP, DIBP, DBP, DMEP, DMPP, DEEP, DNPP, DHXP, BBP DBEP, DCHP, DEHP, DPhP, and DNOP | Sea water (25 mL plus 5% w/v NaCl and 10% v/v MeOH) | SBSE using a PDMS stir bar, stirring at room temperature for 120 min, and desorption with 200 μL MeOH and 50 μL ACN by sonication for 50 min | GC-MS | 0.00027–1.63 μg/L | - | No samples were analyzed | The stir bar coated with 150 μl PDMS showed higher extraction efficiency than coated with 50 μL and 75 μL PDMS, and 150 μL PDMS over carbon film. A mix MeOH-ACN showed higher extraction efficiency than MeOH and dichloromethane as desorption solvent | [66] |
μ-ECD, micro-electron capture detector; AC, activated carbon; ACN, acetonitrile; BBP, benzylbutyl phthalate; BMA, butyl methacrylate; BMPP, bis(4-methyl-2-pentyl) phthalate; CAR, carboxen; CE, capillary electrophoresis; COFs, covalent organic frameworks; CW, carbowax; DAD, diode-array detector; DAP, diallyl phthalate; DBEP, di(2-butoxyethyl) phthalate; DBP, dibutyl phthalate; DCHP, dicyclohexyl phthalate; DEEP, di(2-ethoxyethyl) phthalate; DEHA, di(2-ethylhexyl) adipate; DEHP, di(2-ethylhexyl) phthalate; DEP, diethyl phthalate; DHXP, dihexyl phthalate; DI, direct immersion; DIBP, diisobutyl phthalate; DIDP, diisodecyl phthalate; DINP, diisononyl phthalate; DIPP, diisopentyl phthalate; DMEP, di(2-methoxyethyl) phthalate; DMP, dimethyl phthalate; DMPP, dimethylethyl phthalate; DNOP, di-n-octyl phthalate; DNPP, di-n-pentyl phthalate; DPhP, diphenyl phthalate; DPP, dipropyl phthalate; DVB, divinylbenzene; EDMA, ethylene dimethacrylate; FID, flame ionization detector; G, graphene; GC, gas chromatography; GO, graphene oxide; HPLC, high-performance liquid chromatography; HS, headspace; IT-SPME, in tube-solid-phase microextraction; LOQ, limit of quantification; MeOH, methanol; MIP, molecularly imprinted polymer; MS/MS, tandem mass spectrometry; MS, mass spectrometry; MWCNTs, multi-walled carbon nanotubes; NPs, nanoparticles; PA, polyacrylate; PAE, phthalic acid ester; PDA, poly(dopamine); PDMS, polydimethylsiloxane; PET, polyethylene terephthalate; PPy, polypyrrole; PS, polystyrene; PVC, polyvinylchloride; SBSE, stir bar sorptive extraction; SPE, solidphase extraction; SPME, solid-phase microextraction; TPB, 2,4,6-triphenoxy-1,3,5-benzene; UHPLC, ultra-performance liquid chromatography; UV, ultraviolet.
As it has already been said, the fiber coating plays a key role in the SPME of PAEs from water samples. However, the types of commercial fibers are still limited, which reduces their application field. In addition, under certain conditions they have low thermal and chemical stability. Furthermore, they are fragile since they are based on fused silica supports. Consequently, most of the subsequent studies have been focused on developing new highly selective, efficient, inexpensive, and robust SPME fibers with controllable thickness through different coating techniques. For this purpose, a wide variety of new fibers based on the use of carbon-based nanomaterials [40–43], metal oxide nanoparticles (NPs) [39, 44], molecular imprinted polymers (MIPs) [45], covalent organic frameworks (COFs) [46], and bamboo charcoal [47] have been reported, among others.
The development of carbon-based coatings for stainless-steel fibers has been an important research field as a result of the exceptional properties these materials have, such as great chemical and thermal stability, high surface area and great capacity to establish π-π interactions with the aromatic groups of the PAEs [37, 48, 49]. Moreover, they can be easily dispersed in a polymer matrix to obtain coatings that provide considerably better characteristics than those of virgin polymers. Among them, multi-walled carbon nanotubes (MWCNTs) have been the most used, which are large molecules composed by numerous electronically aromatic delocalized carbon atom layers and rolled up into a cylinder. As examples of the use of this kind of coatings for the extraction of PAEs from water samples, Asadollahzadeh et al. [40] made a fiber coated with an oxidized MWCNTs-polypyrrole (PPy) composite while Behzadi et al. [42] used MWCNTs-poly-o-aminophenol, both obtained through electrochemical polymerization, for the extraction of mineral water samples. Song et al. [41] also prepared a MWCNTs-polystyrene (PS) material via electrostatic interactions as SPME coating, and Zhang et al. [43] developed a SiO2-PDMS-MWCNTs fiber by a sol-gel method. In both cases, drinking and environmental water samples were analyzed. All these fiber coatings presented a porous structure with very large surface areas where both phases (the MWCNTs and polymer) took part in the extraction procedure, enhancing the final adsorption capacity of the fiber. Moreover, in the last work, the organic-inorganic bilayer structure was designed to increase the stability and durability of the coating. In particular, a stainless-steel fiber was coated with a SiO2 layer, which was used as support for the chemical bonding of the second layer of PDMS-MWCNTs (see Figure 1.3). The first coating with a SiO2 layer is a general procedure widely used for coating different surfaces or particles [50, 51]. Compared with commercial PDMS, PA, and DVB-CAR-PDMS fibers, this new coating showed better extraction efficiency and longer lifetimes (150 vs. 50–100 times) for the extraction of DMP, DEP, DBP, and DEHP. It is also noteworthy to mention the extensive study that was conducted by these authors to evaluate the influence of salt addition on the extraction efficiency. It was observed that the addition of different kinds of salts such as NaCl, CaCO3, FeCl3, and MgCl2 at different concentrations (0%, 5%, 10%, and 15%, w/v) can have a negative or a negligible effect on the recovery values. Therefore, no salt was added to the samples, as in the vast majority of the published works on this topic (see Table 1.1).
Figure 1.3 Schematic representation of the SiO2-PDMS-MWNTs fiber preparation. Reprinted from [43] with permission from The Royal Society of Chemistry. MWNTs, multi-walled carbon nanotubes; TEOS, tetraethoxysilane; TSO-OH, hydroxyl terminated silicone oil.
Graphene is another of the allotropic forms of carbon that has been used as SPME coating. It consists of a monolayer of sp2 hybridized carbon atoms arranged in a 2D network. Like MWCNTs, graphene has a high surface area, high chemical and thermal stability as well as a high affinity for hydrophobic and aromatic compounds. Then, graphene-polymer nanocomposites have also been used as excellent SPME fiber coatings for the extraction of PAEs. Such is the case of the work developed by Amanzadeh et al. [20] in which a stainless-steel fiber was coated using a new graphene/polyvinylchloride (PVC) material and evaluated successfully as a SPME fiber for the extraction of dipropyl phthalate (DPP), DBP, DEHA, and DEHP from drinking waters and sunflower and olive oil samples. However, even though it was used in the HS mode, a single fiber could be used only 60 times without a significant decrease in the extraction efficiency. As a very interesting experiment, these authors also determined these PAEs in boiling water exposed to a polyethylene terephthalate (PET) bottle. Although the water used did not contain residues of any of the target PAEs at the beginning, residues of DPP and DBP were found at 2.1 and 1.8 μg/L, respectively, after filling this bottle with the same water just after boiling (it was analyzed after cooling). That is, the PAEs with low molecular weight (250.2 g/mol for DPP and 278.3 g/mol for DBP compared to 370.5 g/mol for DEHA and to 390.5 g/mol for DEHP) have larger water solubility, so these kinds of PAEs migrated more easily from PET bottles containing hot water.
Another example of the benefits of using graphene, is the work of Tashakkori et al. [52] who prepared SPME fibers based on the use of the ionic liquid (IL) 1-(3-aminopropyl)-3-vinyl imidazolium bromide and 1-(3-aminopropyl)-3-vinyl imidazolium tetrafluoroborate grafted onto graphene oxide (GO) previously deposited onto stainless-steel wires. On the one hand, GO disperses more easily for the first preparation step and inherits the mechanical properties of graphene but with a moderate decrease of mechanical parameters (Young’s modulus and intrinsic strength) due to the alterations produced in the sp2 structure [53, 54]. On the other hand, ILs can be structurally customized based on diverse procedures to tune the extraction performance [55]. In fact, ILs can establish a broader variety of interactions with the analytes such as π-π, dipolar, hydrogen bonding, and ionic/charge-charge [56]. As a result, they are also suitable for the extraction of hydrophobic compounds and aromatic analytes like PAEs. Consistently, the first GO-IL fibers showed better extraction efficiency for the analysis of DMP, DEHP, DBP, DNPP, BBP, and DNOP in tap and sea water samples (also in instant coffee samples) than other lab-made fiber, as well as commercial PA and CAR-PDMS fibers, using DI mode in all cases.
MIPs also provide a great improvement in selectivity since they have cavities specifically designed for a particular compound or group of analogous compounds [57, 58]. That is to say, retention occurs through a molecular recognition mechanism based on their size, shape and three-dimensional distribution of functional groups [59]. He et al. [45] demonstrated that MIPs are quite suitable as SPME fiber coatings for the successful extraction of low (DMP, DEP, DBP, and diallyl phthalate -DAP-) and high-molecular PAEs (DNOP) simultaneously, from bottled, tap, and reservoir water samples, although it is true that the latter was poorly extracted since DBP was used as template molecule during the synthesis of the polymer. Moreover, the peak areas obtained using the MIP fiber were much higher than those using a non-imprinted fiber prepared with the same protocol (without the addition of the template molecule), but also better compared to commercial PDMS, PA, and CW-DVB fibers (see Figure 1.4). These results indicate that the MIP fiber provided a better selectivity for the structural analogues of DBP, while commercial SPME coatings are more susceptible to undesirable interferences in the extraction process.
Another variant of SPME which has also been applied for PAEs extraction is in-tube (IT)-SPME [60]. In this format, a very thin tube is coated in its inner walls and the extraction and desorption are carried by the introduction and extraction of the sample inside the tube several times [61]. As in conventional SPME, the combination of materials with high surface areas and polymers afford a high extraction capability, while its porous structure provides suitable dynamic transport during extraction. As examples, Wang et al. [23] used poly(dopamine) (PDA) to functionalize melamine formaldehyde aerogel on carbon fibers and were packed inside IT-SPME tubes for the extraction of seven PAEs from drinkable and surface water, while the performance of this process embedding activated carbon (without any chemical modification) in different polymers (e.g., poly(butyl methacrylate-co-ethylene dimethacrylate) (poly(BMA-EDMA)) and PS-DVB) was investigated by Lirio et al. [62]. In this last work, low extraction recovery values were obtained when a solution containing eight PAEs was collected using monolithic columns with native poly(BMA-EDMA) and PS-DVB. On the contrary, the presence of increasing amounts of activated carbon provided a higher extraction efficiency under the same conditions. Moreover, the activated carbon-PS-DVB monolithic column exhibited better extraction performance than the activated carbon-poly(BMA-EDMA) one. Therefore, the first was applied in the IT-SPME of mineral water samples obtaining recovery values in the range of 78.8%–104.6% at 50 μg/L.
Figure 1.4 Extraction yields with different fibers (MI-SPME, PDMS, CW/DVB, and PA) in water samples. Extraction conditions: 12 ml of spiked pure water including NaCl content of 10% w/v, stirring at 60°C in DI, adsorption time 30 min, desorption at 250°C for 10 min. Reprinted from [45] with permission from Elsevier. CW, carbowax; DAP, diallyl phthalate; DBP, dibutyl phthalate; DEP, diethyl phthalate; DMP, dimethyl phthalate; DNOP, di-n-octyl phthalate; DVB, divinylbenzene; MI, molecular imprinted polymer; PA, polyacrylate; PDMS, polydimethylsiloxane; SPME, solid-phase microextraction.
