Abstract
A systematic evaluation of eight different coatings made of solid phase extraction (SPE) and carbon-based sorbents immobilized with polyacrylonitrile in the thin-film microextraction (TFME) format using LC-MS/MS was described. The investigated coatings included graphene, graphene oxide, multi-walled carbon nanotubes (MWCNTs), carboxylated MWCNTs, as carbon-based coatings, and polystyrene-divinylbenzene (PS-DVB), octadecyl-silica particles (C18), hydrophilic–hydrophobic balance particles (HLB) and phenyl-boronic acid modified particles (PBA), as SPE-based coatings. A total of 24 compounds of diverse moieties and of a wide range of polarities (log P from −2.99 to 6.98) were selected as probes. The investigated coatings were characterized based on their extraction performance toward the selected probes at different pH values and at optimized desorption conditions. In the case of SPE-based coatings, PS-DVB and HLB exhibited a balanced extraction for compounds within a wide range of polarities, and C18 showed superior extraction recoveries for non-polar analytes. Carbon-based coatings showed high affinity for non-polar compounds given that their main driving force for extraction is hydrophobic interactions. Interestingly, among the studied carbon-based coatings, graphene oxide showed the best extraction capabilities toward polar compounds owing to its oxygen-containing groups. Overall, this work provided important insights about the extraction mechanisms and properties of the investigated coatings, facilitating the coating selection when developing new TFME applications.
Highlights
Thin-film microextraction (TFME), an alternative configuration of solid-phase microextraction (SPME), was first introduced in 2003 [1] and has since been employed for various LC and GC applications [1,2,3,4]
Eight different adsorbents used as TFME coatings were systematically evaluated, using as models various compounds characterized by a wide range of log P values
The graphene oxide coating showed better extraction performance for polar compounds owing to its hydrophilic functional groups on the surface
Summary
Thin-film microextraction (TFME), an alternative configuration of solid-phase microextraction (SPME), was first introduced in 2003 [1] and has since been employed for various LC and GC applications [1,2,3,4]. In addition to the above SPE phases, carbon nanomaterials including graphene and carbon nanotubes (CNTs) have been employed as potential adsorbents for SPE and SPME applications due to their large surface area and tunable surface properties [14,15,16,17] In this regard, CNTs have been employed in TFME coatings for high-throughput analysis of phenolic compounds in water [18]. The effect of extraction conditions, such as pH, on the extraction performance of TFME coatings must be thoroughly evaluated to provide analysts with a better understanding of the extraction behaviors of various kinds of compounds on these adsorbents Such information would help better inform analysts with respect to coating selection during TFME method development of real applications. The influence of pH (3.0, 7.4 and 10.0) on the extraction capacities of the selected coatings was further investigated in order to better elucidate the extraction mechanisms of these analytes on the eight different coatings
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