Innovations in Extractive Phases for In-Tube Solid-Phase Microextraction Coupled to Miniaturized Liquid Chromatography: A Critical Review

Abstract

Over the past years, a great effort has been devoted to the development of new sorbents that can be used to pack or to coat extractive capillaries for in-tube solid-phase microextraction (IT-SPME). Many of those efforts have been focused on the preparation of capillaries for miniaturized liquid chromatography (LC) due to the reduced availability of capillary columns with appropriate dimensions for this kind of system. Moreover, many of the extractive capillaries that have been used for IT-SPME so far are segments of open columns from the gas chromatography (GC) field, but the phase nature and dimensions are very limited. In particular, polar compounds barely interact with stationary GC phases. Capillary GC columns may also be unsuitable when highly selective extractions are needed. In this work, we provide an overview of the extractive capillaries that have been specifically developed for capillary LC (capLC) and nano LC (nanoLC) to enhance the overall performance of the IT-SPME, the chromatographic separation, and the detection. Different monolithic polymers, such as silica C18 and C8 polymers, molecularly imprinted polymers (MIPs), polymers functionalized with antibodies, and polymers reinforced with different types of carbon nanotubes, metal, and metal oxide nanoparticles (including magnetic nanoparticles), and restricted access materials (RAMs) will be presented and critically discussed.

Novel solid‐phase microextraction fiber coatings: A review

“…Metal oxides used in chemical sensors are usually applied for the preparation of the extraction phase. Robust, efficient, and cheap SPME coatings have been designed with the metal oxides that possessed excellent properties of large surface-to-volume ratio, good adsorption ability, and high thermal stability, such as cobalt oxide, titanium dioxide, lead oxide, zirconium oxide, and zinc oxide [154][155][156][157]. The main preparation approaches are hydrothermal growth, electrodeposition, and pyrolysis-glue adhesion.…”

Capillary Liquid Chromatography for the Determination of Terpenes in Botanical Dietary Supplements

“…Recent progress in LC has resulted in miniaturized scale separations, such as capillary LC (CapLC) with enhanced resolution and sensitivity derived from the fact that the dispersion of the analytes during the separation is considerably reduced [ 21 ]. Miniaturized LC offers additional advantages such as lower consumption of mobile and stationary phases, and a reduction in the generation of wastes [ 22 ]. However, in the analysis of dietary supplements, CapLC has only been applied to a few compounds so far, mainly amino acids and peptides, fatty acids, and flavonoids [ 23 ].…”

Application of Covalent Organic Porous Polymers-Functionalized Basalt Fibers for in-Tube Solid-Phase Microextraction

“…For IT-SPME, the property of extraction materials directly affects the extraction performance and then influences the analytical results, so the extraction efficiency can be improved via selecting good extraction materials. So far, a variety of advanced materials have been used as the coatings for SPME, such as nanomaterials [ 22 , 23 ], carbon materials [ 24 , 25 ], mesporous materials [ 26 , 27 ], ionic liquids [ 28 , 29 ], aerogels [ 30 , 31 ], metal-organic frameworks [ 32 ], covalent organic frameworks [ 33 ], and so on. Covalent organic porous polymers (COPs) are completely composed of light elements (C, H, O, N, etc.)…”