Nanomaterials in Extraction Techniques
Despite the advances in analytical instrumentation, separation, enrichment and sample clean-up procedures continue to be essential analytical steps prior to the determination stage itself. Numerous potential interferents and low concentrations of analytes make a preliminary extraction procedure necessary. The development of new extraction techniques and the improvement of existing techniques using novel extraction materials are the main trends in this research area. Nanomaterials, materials with sizes or features ranging from 1 to 100 nm in one or more dimensions, have drawn extensive attention from scientists in recent years mainly owing to their unique and attractive thermal, mechanical, electronic and biological properties. Their high surface-to-volume ratio, the possibility for surface functionalization and favorable thermal features provide the flexibility needed in a broad range of analytical application. Their properties have been extensively exploited in different extraction techniques, such as solid-phase extraction and microextraction. Nanomaterials can be used as single particles, aggregates, powders or dispersed in a matrix, and their physicochemical properties can be controlled through structural design, incorporation of suitable components or modification of the surfaces. Whereas monofunctional nanomaterials provide a single function, the preparation of core/shell nanoparticles allows different properties to be combined in one material. In the preparation of these multifunctional nanomaterials, various strategies are used to attain a combination of targeting specificity, magnetic properties and analysis capability. The surface modification of nanomaterials by functional molecules, particles or polymers can improve the separation and preconcentration efficiency, analytical selectivity and method reliability. The aim of this chapter is to provide an updated and critical review of the most important features and applications of nanomaterials (metallic, silica and carbon-based) for solid-phase extraction and microextraction techniques. Emphasis will be placed on description of work that has provided interesting results for use in this analytical field.