FLUORINE-FREE IONIC LIQUIDS FOR SEPARATIONS AND SENSOR
APPLICATIONS
Vladimir Egorov, Igor Pletnev, Maria Roslova and Natalia Shvedene
Department of Chemistry, Lomonosov Moscow State University, Moscow, Russia
shvedene@analyt.chem.msu.ru
Ionic liquids (ILs) are promising new solvents which are increasingly widely used in analytical
chemistry [1]. However, their much publicized “green” nature and environmental friendliness were
recently subjected to serious doubts. In our opinion, these doubts may be, to a large extent, related
to widespread use of fluorinated anions as anionic constituents of ionic liquids (whence poor
biodegradability, possible biotoxicity, etc.; also a relatively high price of IL).
Being interested in applications of ionic liquids in solvent extraction [2] and electrochemical analysis
[3], we are in search of novel fluorine-free ionic ILs suitable for analytical applications. We studied
some commercially available fluorine-free ILs (e.g., trihexyltetradecylphosphonium decanoate and
bis (2,4,4-trimethylpentyl)phosphinate) and produced some novel ones. In particular, recently we
synthesized (for the first time, to the best of our knowledge) and characterized ionic liquids
comprising an anion of N-acylated amino acid, N-lauroyl sarcosinate (sarcosine is N-methylglycine).
Lauroyl sarcosinate is readily available as it is a component of industrial-scale produced and widely
used surfactant, sodium lauroylsarcosinate. Given its derivation from amino acid and wide use in
personal care cosmetics products, good biodegradability and biocompatibility of lauroyl sarcosinate
is of little surprise. Tetrahexylammonium and tetraoctylammonium lauroyl sarcosinates are waterimmiscible ionic liquids. Quite interestingly, the measured water content (saturated) in these ionic
liquids is rather high and unusual for typical ‘hydrophobic’ solvents. The stability of the lauroyl
sarcosinate ILs to hydrolysis at various pH and their miscibility with a number of organic solvents
have been studied. Also, solubility and aggregation in water have been investigated. The polarity of
solvents has been estimated using a solvatochromic probe method.
The extraction of metal ions and organic compounds into fluorine-free ILs has been investigated.
The parameters of extraction systems (phase volume ratio, time of phase contact, pH of aqueous
phase, etc.) were optimized to reach the maximum recovery at the minimum IL consumption. The
effect of cation’s alkyl chain length on the extraction efficiency was examined. Also, ionic liquids
containing non-fluorinated anions were studied as components of ion-selective electrodes.
The authors are grateful to Russian Foundation for Basic Research for the support (grant No. 09-0312259-ofi_m).
References
1. Ionic Liquids in Chemical Analysis. Ed. By M. Koel. 448 pp. CRC Press, 2008.
2. I. Pletnev, S. Smirnova and V. Egorov. Liquid-Liquid Extraction of Organic Compounds. [1], pp.
243-267.
3. N. Shvedene, D. Chernyshov and I. Pletnev. A review of application of ionic liquids in
electrochemical sensors. Russian Chem. J., v. 52, N2, pp. 80-91, 2008 (in Russian).
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