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,