oa Editorial [Hot Topic: Ionic Liquids: Analytical and Environmental Issues (Guest Editors: Piotr Stepnowski and Stefan Stolte)]

Ionic liquids (ILs) are low melting point salts considered to be a new class of alternative solvents that represent ideal non-volatile media for a variety of industrial processes such as organic synthesis and biocatalysis, alternative electrolytes, phases and phase modifications in separation techniques, and alternative lubricants. Today's definition of ILs is based solely on their melting point, which is arbitrarily chosen to be below 100oC. ILs already in common use typically involve nitrogen- or phosphorus-containing organic cations such as alkylimidazolium, alkylpyridinium, alkylpyrrolidinium or alkylphosphonium, and anions like bis(trifluoromethanesulfonyl)imide, hexafluorophosphate and alkylsulfate. Although these cations and anions and their various combinations have already been studied extensively for their potential applications in numerous chemical and physical processes, every year more and more cations and anions forming liquid salts at room temperature are reported. One of the most attractive characteristics of ILs (apart from their negligible vapor pressure) is their potential to be “designed to order”. Properties such as density, moisture stability, viscosity or miscibility with other chemicals can be tailored by the appropriate selection of cation and anion; a very rough estimate indicates that such combinations can be numbered in the millions. It is therefore possible that we are dealing with a momentous breakthrough in modern chemistry and technology. This almost limitless potential to make new ionic liquids tailored to novel or existing applications is an exciting, visionary prospect. On the other hand, we have to be aware that in this field we will soon be facing a huge number of new chemicals, about which we actually know very little. In particular, data relating to hazard assessment are usually incomplete or even non-existent, because these chemicals are not yet being produced on an industrial scale. Once the large-scale implementation of ILs begins, however, it will not be long before they become permanent constituents of industrial effluents. In view of their great stability, they could slip through classical treatment systems to become persistent components of the environment, where the long-term consequences of their presence are still unknown. An understanding of their physicochemical parameters, toxicity and ecotoxicity, mobility and distribution in soils and sediments is therefore crucial for an accurate prediction of their fate in the environment.....