Ionic liquids: multi‐role actors in elemental speciation analysis

Abstract

Elemental speciation is a concept that results extremely relevant in nutritional, toxicity and environmental studies as it generates crucial information to fully understand the bioavailability and toxicity of an element1. However, high selectivity and sensitivity are the main demands to be covered by analytical methods for trace elements speciation studies. To accomplish these goals, the combination of a selective separation technique with highly sensitive detectors has been the main strategy. Although any kind of separation technique is feasible, chromatographic techniques are easily coupled to elemental specific detectors. Likewise, non-chromatographic separation techniques can also be used for speciation analysis, but with a more limited separation power. In any case, both methodological approaches require constant improvements due to the high complexity to analyze the speciation of some elements and the difficulty imposed by sample matrices. Ionic Liquids (ILs) are recognized as modern solvents with remarkable properties such as low volatility, high conductivity, and the possibility of offering multiple interactions with different chemical species. Therefore, they have found wide application in different fields of analytical chemistry. In fact, ILs have been proposed as highly efficient extraction phases for separation and preconcentration, while their particular interactions with solutes show them as excellent tools in chromatography as well2. Moreover, the potential of ILs for the separation and preconcentration of trace elements can be further extended beyond their own limits when they are combined with different types of nanomaterials, and properties such as magnetism can be imparted to these extraction phases for more practical microextraction procedures. In this lecture, recent advances on the development of non-chromatographic and chromatographic separation methods using ILs for elemental speciation analysis will be presented. The development of modern liquid-liquid and solid-phase microextraction techniques (e.g. dispersive liquid-liquid microextraction (DLLME) and dispersive microsolid phase extraction (D-µ-SPE)) based on ILs and their combination with certain nanomaterials will be discussed. Also, the application of ILs for the determination of elemental species by HPLC-elemental specific detector hyphenated techniques will be presented, along with the benefits and potential drawbacks of their application when they are coupled to atomic spectrometry-based techniques.