Two-dimensional materials as a platform in extraction methods: A review

Abstract

Sample preparation is a critical step in analytical chemistry, particularly in the consideration of analytes of interest from complex matrices. Due to this complexity, the presence of interferences and low concentrations of the analytes, direct analysis of matrices is not possible in most cases. So, to address this, sample preparation is necessary for removing possible interferences, and pre-concentrating the target analytes. Sorbent-based sorptive extraction/microextraction (SBSEME) is a versatile sample preparation method that has been widely applied for the processing of various samples. With a judicious choice of sorbents, SBSEME can provide benefits like simplicity, ease of operation, cost-effectiveness, high accessibility, moderate extraction time, and low-to-moderate consumption of solvents, and compatibility with different detection techniques. Among the many different materials that have been used in SBSEME as sorbents, two-dimensional materials (TDMs) like graphene and its derivatives (graphene oxide and reduced graphene oxide) have been attracting a lot of attention in recent years by those involved in the sample preparation field. TDMs have amenable characteristics like porous structures, high surface area, high adsorption capacity, ease of modification to further improve their properties, generally low toxicity, excellent biocompatibility, high physical, chemical and thermal stability, high elasticity and flexibility, and high resistance and thermal conductivity. To better investigate and understand the applicability of TDMs in sample preparation methods, it is important to survey recent progress and development of TDMs with reference to their synthesis and applications. To this end, in this review article, (a) TDMs, their features, synthesis and modification approaches are investigated; (b) different TDM composites are studied and evaluated; (c) the applications of TDMs and their composites in different extraction methods such as solid-phase extraction (SPE), dispersive SPE, magnetic SPE, micro-SPE, solid-phase microextraction, pipette-tip solid-phase extraction, stir bar sorptive extraction, and headspace sorptive extraction are described; (d) possible mechanisms of sorbent-analyte interactions as a vital aspect of extraction are also evaluated; and (e) current trends and future prospects in relation to synthesis and application of TDMs and their composites in extraction methods are assessed. The general conclusion that can be drawn from the review is that these versatile materials represent a fertile area of sample preparation research that will continue to be advanced further by analytical chemists.