Ionic Liquids in Analytical Chemistry

Soukup-Hein, Renee J.; Warnke, Molly M.; Armstrong, Daniel W.

doi:10.1146/annurev-anchem-060908-155150

Cited by 120 publications

(69 citation statements)

References 130 publications

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“…5 Various combinations of cations and anions make ILs "designable" solvents of great versatility for an increasing number of applications. 6 A molecular understanding of IL properties is crucial to the design of ILs.…”

Section: Introductionmentioning

confidence: 99%

Improved United-Atom Force Field for 1-Alkyl-3-methylimidazolium Chloride

et al. 2010

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We have developed a united atom (UA) nonpolarizable force field for 1-alkyl-3-methyl-imidazolium chloride ([C n mim][Cl], n ) 1, 2, 4, 6, 8), a potential solvent for the pretreatment of lignocellulosic biomass. The charges were assigned by fitting the electrostatic potential surface (ESP) of the ion pair dimers. The LennardJones parameters of the hydrogen atoms on the imidazolium ring were adjusted to agree with the ab initio optimized geometries of isolated ion pairs. Molecular dynamics (MD) simulations were performed for a wide range of temperatures to validate the force field. Substantial improvements were found in both the dynamical properties and the fluid structures, as compared to those predicted using our previously developed UA force field (UA2006) (Phys. Chem. Chem. Phys. 2006, 8, 1096. Liquid densities were found to lie within 2% experimental data. The simulated heats of vaporization decreased about 30% relative to that predicted using the UA2006 force field. The site-site radial distribution functions between the hydrogen atoms on the imidazolium ring and the chloride anions were in good agreement with those determined by ab initio molecular dynamics. The newly developed force field gives a much better description of the self-diffusion coefficients and shear viscosities, which usually deviate by 1 order of magnitude when determined using other force fields.

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Section: Introductionmentioning

confidence: 99%

Improved United-Atom Force Field for 1-Alkyl-3-methylimidazolium Chloride

et al. 2010

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“…In fact, the first work by Tanaka et al [3] on the laser-induced production of gas-phase ions from biomolecules was made using glycerol as the matrix. Room temperature ionic liquids with very low vapor pressures can be useful homogeneous matrixes for MALDI [20][21][22][23][24][25][26][27][28][29][30], as first demonstrated by Armstrong et al [21]. An ionic liquid is prepared by mixing equal amounts of an acid and a base.…”

Section: Ion Ratiomentioning

confidence: 99%

Investigations of Some Liquid Matrixes for Analyte Quantification by MALDI

Moon

Park

Ahn

et al. 2015

J. Am. Soc. Mass Spectrom.

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Abstract. Sample inhomogeneity is one of the obstacles preventing the generation of reproducible mass spectra by MALDI and to their use for the purpose of analyte quantification. As a potential solution to this problem, we investigated MALDI with some liquid matrixes prepared by nonstoichiometric mixing of acids and bases. Out of 27 combinations of acids and bases, liquid matrixes could be produced from seven. When the overall spectral features were considered, two liquid matrixes using α-cyano-4-hydroxycinnamic acid as the acid and 3-aminoquinoline and N,N-diethylaniline as bases were the best choices. In our previous study of MALDI with solid matrixes, we found that three requirements had to be met for the generation of reproducible spectra and for analyte quantification: (1) controlling the temperature by fixing the total ion count, (2) plotting the analyte-to-matrix ion ratio versus the analyte concentration as the calibration curve, and (3) keeping the matrix suppression below a critical value. We found that the same requirements had to be met in MALDI with liquid matrixes as well. In particular, although the liquid matrixes tested here were homogeneous, they failed to display spot-to-spot spectral reproducibility unless the first requirement above was met. We also found that analytederived ions could not be produced efficiently by MALDI with the above liquid matrixes unless the analyte was sufficiently basic. In this sense, MALDI processes with solid and liquid matrixes should be regarded as complementary techniques rather than as competing ones.

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“…Tunability is a characteristic that is unavailable with all other classes of GC stationary phases. By means of relatively simple synthetic modifications or changes to the cation, anion (or substituents thereon), and the linkage chains of ILs, the desired solvent and selectivity characteristics can be altered and controlled [25][26][27][28][29].…”

Section: Novel Materials As Gc Stationary Phasesmentioning

confidence: 99%