Task-specific ionic liquids: Applications in sample preparation and the chemistry behind their selectivity

•Review of the last ten years of task-specific ionic liquids (TSILs) applications for sample preparation, covering practically of their history in this field.•Applications on TSILs for preparation and treatment of environmental, food and beverages and biological samples are reviewed and analyzed in terms of their analytical characteristics.•Special emphasis is made on the chemistry responsible for the selectivity of TSILs, and the structural reasons behind their specificity. Task-specific ionic liquids (TSILs) represent a sub-family of ionic liquids characterized by their high specificity towards a target analyte or group of analytes. This characteristic has made them valuable tools for sample preparation, where selectivity represents a key aspect, especially when other species represent a significant source of interference or when non-specific detectors are used. This review presents an overview of TSILs applications for sample preparation from the last ten years, with a special emphasis on their use as liquid-liquid microextraction solvents or as functionalizing agents for sorbents applied to solid-phase microextractions. TSILs applications for the treatment of environmental, food and biological samples are reviewed, including reports devoted to speciation analysis, a relevant trend in recent years regarding elemental studies. Additionally, focus is made on the ‘task-specificity’ of the presented TSILs, including a description of the chemical characteristics that made them selective towards the studied analytes. Finally, future trends and gaps to be covered in the field are also discussed.