Carbon nanomaterial-based membranes in solid-phase extraction

Abstract

Carbon nanomaterials (CNMs) have some excellent properties that make them ideal candidates as sorbents for solid-phase extraction (SPE). However, practical difficulties related to their handling (dispersion in the atmosphere, bundling phenomena, reduced adsorption capability, sorbent loss in cartridge/column format, etc.) have hindered their direct use for conventional SPE modes. Therefore, researchers working in the field of extraction science have looked for new solutions to avoid the above-mentioned problems. One of these is the design of CNM-based membranes. These devices can be of two different types: membranes that are exclusively composed of CNMs (i.e. buckypaper and graphene oxide paper) and polysaccharide membranes containing dispersed CNMs. A membrane can be used either as a filter, operating under flow-through mode, or as a rotating device, operating under the action of magnetic stirring. In both cases, the main advantages arising from the use of membranes are excellent results in terms of transport rates, adsorption capability, high throughput, and ease of employment. This review covers the preparation/synthesis procedures of such membranes and their potential in SPE applications, highlighting benefits and shortcomings in comparison with conventional SPE materials (especially, microparticles carbonaceous sorbents) and devices. Further challenges and expected improvements are addressed too.

Keywords: Buckypaper; Carbon nanotubes; Graphene; Membranes; Solid-phase extraction.

Fig. 1

a C1s XP spectrum. b O1s XP spectrum of BP. The three peaks centred at 286, 287, and 288 eV can be assigned to different types of oxidized carbon: carbon involved in a single bond with an oxygen atom (phenols and ethers); carbon involved in a double bond with an oxygen atom (ketones and aldehydes); carbon involved simultaneously in single and double bond with an oxygen atom (carboxylic groups). (Reproduced with permission from [25])

Fig. 2

a Schematic illustration of the stir-disk SPE unit, components for its assembly, and operational steps. b Investigation of the individual influence of logP and pKa on the recovery of the model compounds extracted by the stir-disk SPE device. (Reproduced with permission from [29])

Fig. 3

Schematic illustration of the whole extraction procedure: a protein precipitation and b operational steps of rotating-disk micro-SPE clean-up. (Reproduced with permission from [30])

Fig. 4

Illustration of interactions between GO and CS (reproduced with permission from [43])

Fig. 5

a Schematic representation of the grafting method for polymer modification (modified from [51]). b Synthesis and structure of S-CS-MWCNTs. (Modified from [50])

Fig. 6

a FESEM surface morphology of the AG/CS-MWCNT composite film. b the FESEM cross section. (Reproduced with permission from [51])

Fig. 7

Schematic illustration of a MMM microextraction and the setup for the simultaneous microextraction of 15 samples using a multiposition magnetic stirrer (reproduced with permission from [56])