Novel in-house mixed-mode ion-exchange materials for sorptive phase extraction techniques

Mixed-mode ion-exchange materials have been implanted in different sorptive extraction techniques as they combine capacity and selectivity in a single material. They are a good option for concentrating ionic (or ionisable) compounds from complex samples using an appropriate washing step that simplifies the sample matrix. Research into the development of in-house mixed-mode ion-exchange materials is therefore a field of scientific interest. These materials are developed with the aim to improve the features of both the core and the ionic moieties attached. The study of the optimal extraction protocol to exploit the ionic interactions between the material and the target compounds is a key point in method development. This review is an overview of the preparation, characterisation, evaluation and application of in-house mixed mode ion-exchange materials. It mainly covers the technique of solid-phase extraction; however, the latest advances in solid-phase microextraction, stir bar sorptive extraction and other emerging microextraction techniques are also presented. Examples of different applications that cover the extraction of different compounds in several types of samples are also illustrated.