A Müller

Effects of different head groups and functionalised side chains on the aquatic toxicity of ionic liquids

In this study, the influence of different head groups, functionalised side chains and anions of ionic liquids on the marine bacteria Vibrio fischeri, the limnic green algae Scenedesmus vacuolatus and the fresh water plant Lemna minor was investigated. The aim of these experiments is to improve the knowledge base for the molecular design of ionic liquids leading to a reduced (eco)toxicological hazard potential. The analysed set of about 40 ionic liquids confirmed the interdependency between lipophilicity—as derived from gradient HPLC—and (eco)toxicity. The toxicity was clearly reduced for the test organisms (partially by six to seven orders of magnitude) when short functionalised side chains were used instead of non-polar alkyl chains. Furthermore, we could demonstrate strong interactions of hydrophobic ionic liquid cations with two different types of common biological lipidbilayers, indicating that the membrane system of organisms is probably a primary target site of toxic action. These systematic studies are addressed to producers, developers and downstream users of ionic liquids in different fields of application, to facilitate the selection of (eco)toxicologically favourable structural elements and thus to contribute to the design of inherently safer ionic liquids.

Reversed-phase liquid chromatographic method for the determination of selected room-temperature ionic liquid cations

The separation of selected 1-alkyl- and 1-aryl-3-methylimidazolium-based room temperature ionic liquid cations has been performed using reversed-phase high-performance liquid chromatography with electrospray ionization mass detection. The RP-HPLC method development started with the selection of a column taking into account especially the resolution of low molecular congeners of the selected group. Mobile phase composition was optimized for peak resolution, sensitivity and high reproducibility of retention values. The results of the method development were applied to the determination of exemplary ionic liquid species present in the medium used in cytotoxicity studies.

Purity specification methods for ionic liquids

In the last decade, ionic liquids have shown great promise in a plethora of applications. However, little attention has been paid to the characterisation of the purity of these fluids, which has ultimately led to non-reproducible data in the literature. In order to facilitate specification of ionic liquids, a number of analytical protocols with their limits of detection (where available) have been compiled, including methods of other authors. In particular, quantitative methods have been developed and summarised for the determination of the total ionic liquid content, residual unreacted ionic liquid starting material and by-products (amines, alkylating agents, inorganic halides), solvents from extraction procedures and water, in addition to decomposition products and total volatiles.

Explaining Ionic Liquid Water Solubility in Terms of Cation and Anion Hydrophobicity

The water solubility of salts is ordinarily dictated by lattice energy and ion solvation. However, in the case of low melting salts also known as ionic liquids, lattice energy is immaterial and differences in hydrophobicity largely account for differences in their water solubility. In this contribution, the activity coefficients of ionic liquids in water are split into cation and anion contributions by regression against cation hydrophobicity parameters that are experimentally determined by reversed phase liquid chromatography. In this way, anion hydrophobicity parameters are derived, as well as an equation to estimate water solubilities for cation-anion combinations for which the water solubility has not been measured. Thus, a new pathway to the quantification of aqueous ion solvation is shown, making use of the relative weakness of interactions between ionic liquid ions as compared to their hydrophobicities.

Sorption and desorption of imidazolium based ionic liquids in different soil types.

This study investigates the influence of the two different clay minerals kaolinite and smectite as well as of organic matter on the cation sorption and desorption behaviour of three imidazolium based ionic liquids -1-butyl-3-methyl-imidazolium tetrafluoroborate (IM14 BF(4)), 1-methyl-3-octyl-imidazolium tetrafluoroborate (IM18 BF(4)) and 1-butyl-3-methyl-imidazolium bis[(trifluoromethyl)sulfonyl]imide (IM14 (CF(3)SO(2))(2)N) - in soil. The German standard soil Lufa 2.2 - a natural soil classified as a loamy sand - was the basis substrate for the different soil compositions and also served as a reference soil. The addition of organic matter and clays increases the sorption of the substances and in particular smectite had striking effects on the sorption capacity for all three ionic liquids indicating that ionic interactions play an important role for sorption and desorption processes of ionic liquids in soil. One exception was for kaolinite-containing soils and the IM14 cation: with (CF(3)SO(2))(2)N(-) as an anion the sorption was identical at either 10 wt% or 15 wt% clay content, and with BF(4)(-) sorption was even lower at 15 wt% kaolinite than at 10 wt%. Desorption was weak for IM18 BF(4), presumably owing to the longer alkyl side chain. With regard to the influence of kaolinite on desorption, the same pattern was observed as it was found for the sorption of IM14 BF(4) and IM14 (CF(3)SO(2))(2)N.

Electron-impact ionization of multiply charged tungsten ions

Absolute cross sections for electron-impact ionization of Wq+ ions (q ≤ 17) are measured using a well established electron-ion crossed beams technique. A special problem with many-electron tungsten ions is the existence of large numbers of long-lived excited states and their presence in the primary ion beams employed in the experiments.

Dielectronic Recombination of Fe XXI and Fe XXII via N = 2→N' = 2 Core Excitations: Data

We have measured dielectronic recombination (DR) resonance strengths and energies for carbon-like Fe xxi forming Fe xx and for boron-like Fe xxii forming Fe xxi via N ¼ 2 ! N 0 ¼ 2 core excitations. All measurements were carried out using the heavy-ion Test Storage Ring at the Max-Planck-Institute for Nuclear Physics in Heidelberg, Germany. We have also calculated these resonance strengths and energies using three independent, state-of-the-art perturbative techniques: a multiconfiguration Breit-Pauli (MCBP) method using the code AUTOSTRUCTURE, a multiconfiguration Dirac-Fock (MCDF) method, and a relativistic configuration interaction method using the Flexible Atomic Code (FAC). Overall, reasonable agreement is found between our experimental results and our theoretical calculations. The most notable discrepancies tend to occur for relative collision energies d3 eV. We have used our measured 2 ! 2r esults to produce Maxwellianaveraged rate coefficients for Fe xxi and Fe xxii. Our experimentally derived rate coefficients are estimated to be accurate to better than � 20% both for Fexxi at kBTe > 0: 5e V and for Fexxii at kBTe > 0:001 eV. For these !

Cross-section measurements with interacting beams

Interacting beams were first employed to determine absolute cross sections for atomic processes a half-century ago. Significant advances in many technologies have improved the precision and sensitivity of such measurements to the degree that the high quality of those early experiments seems remarkable today. Despite their early successes and continuing advances, interacting beams experiments and the determination of absolute cross sections and rate coefficients from them remain a challenge. This paper concentrates on one large-scale technical advance, the synchrotron light source that has facilitated interacting-beams measurements of cross sections for photoionization of atomic and molecular ions. Recent results will be presented for photoionization of fullerene and endofullerene molecular ions.

High-power electron gun for electron-ion crossed-beams experiments

A high-performance electron gun for crossed-beams electron-ion collision experiments is presented. First test measurements demonstrated high electron currents, e.g., 1 A at 3.5 keV electron energy verifying the results of electron optics simulations carried out prior to the mechanical construction of the gun. Presently, the device is implemented into an ultra-high vacuum setup that will allow for its integration into an ion beamline for cross section measurements.

Recombination and Ionization Measurements at the Heidelberg Heavy Ion Storage Ring TSR

Knowledge of the charge state distribution (CSD) of astrophysical plasmas is important for the interpretation of spectroscopic data. To accurately calculate CSDs, reliable rate coefficients are needed for dielectronic recombination (DR), which is the dominant electron-ion recombination mechanism for most ions, and for electron impact ionization (EII). We are carrying out DR and EII measurements of astrophysically important ions using the TSR storage ring at the Max-Plank-Institute for Nuclear Physics in Heidelberg, Germany. Storage ring measurements are largely free of the metastable contamination found in other experimental geometries, resulting in more unambiguous DR and EII reaction rate measurements. The measured data can be used in plasma modelling as well as for benchmarking theoretical atomic calculations.