Applications of Ionic Liquids in Analytical Chemistry

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Here we report a systematic study on electrical conductivity and surface tension of various concentrated solutions of imidazolium based room temperature ionic liquids (RTILs), viz. 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF 6 ]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF 4 ]) in the cosolvents methanol and acetonitrile at 298.15 K. The aim of the investigations was to explore the impact of cosolvents on bulk and interfacial characteristics of imidazolium based RTILs. It was observed that both methanol and acetonitrile mix non-ideally with and enhance the transport parameters of the imidazolium based RTILs. An interesting outcome of the presented work is that the investigated RTILs retain their inherent structural characteristics up to a high dilution limit with cosolvent, and this limit is higher in acetonitrile than in methanol as cosolvent. The findings establish that, in comparison to methanol, acetonitrile is a better cosolvent that can be used for enhancing the transport parameters of imidazolium based RTILs for electrochemical and other applications. The results are explained in light of structure-composition-property relations and ion-ion and ion-cosolvent interactions.

A series of weakly coordinating cations/anions (TAPR/TFAB) ion pairs are, herein, being proposed as non-aqueous electrolytes for high capacity ORFBs. These were accessed via a Palladiumcatalyzed approach followed by the simple filtration/isolation of the product. These substituted tetraarylphosphonium/tetrakis(pentafluorophenyl)borate salts 1-4 where the substituents are a pmethoxy (1), a 3,4-dimethoxy (2), a p-phenyl (3), and a p-trimethylsilylacetylene (TMSA) (4) have potential use in several industries owing to their unique solubility in low polarity solvents. These salts constitute a new class of molecular ion pairs which can promote charge dissociation even in low polarity solvents because of their large size and bulkiness. The result being an increased conductivity in those media that can be useful for electrochemistry, advances in catalysis, battery technology, petroleum handling etc. This work supports the national security goal of fostering the development of affordable, cl...

The use of ionic liquids in capillary electrophoresis, either as coating material or as components of the background electrolyte needs systematic standardization to set up optimal conditions. Excellent separation of the proteins was achieved using 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([emim][BF4]) or 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim][BF4]) ionic liquids using the properly made ionic‐liquid–water binary mixtures for the experiments. The binary mixture has a distinctly stable and well perceptible low pH, which depends on the concentration of the ionic liquid, and on the preparation time of the mixture. Optimal conditions for the electrophoretic separation were obtained upon a multivariate analysis of the experimental parameters (applied voltage, migration time, concentration, and type of the ionic liquid). The standardized condition provides a low electroendosmotic flow toward the anode, which, however, did not hinder the proteins to migrate toward the cat...

The application of ionic liquids (ILs) as nonderivatizing solvents for the pretreatment and regeneration of cellulose is a growing area of research. Here we report the development of a rapid and simple method for the determination of residual ethanol content in two hydrophilic ILs, 1-butyl-3-methylimidazolium chloride and 1-ethyl-3methylimidazolium acetate. The method utilizes headspace solid-phase microextraction coupled with gas chromatography at elevated extraction temperatures, resulting in rapid equilibration times. The effect of IL water content on the ethanol extraction efficiency is presented. Recovery experiments carried out in real samples gave recoveries ranging from 96.8 to 98.2%.

An attempt has been made to develop a fast, efficient and eco-friendly process for extraction of drug; Rifampicin (RF) from its aqueous solutions using room temperature ionic liquids (RTILs). RTILs viz. 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium tetrafluoroborate and 2-Hydroxyethyl-trimethylammonium L-(+)-lactate have been used for removal of RF. Various factors such as hydrophilicity/hydrophobicity of RTILs, concentration of used RTILs and pH of drug solutions, affecting removal of RF from its aqueous solution have been studied to investigate mechanism of extraction process. Partition coefficient of RF between RTILs and aqueous phases as well as its extraction efficiency have also been calculated and analyzed. Results showed that hydrophobicity plays a major role in extraction of RF from its aqueous solutions. The addition of just 2 % of hydrophobic RTIL; [BMIM][PF 6 ] leads to almost complete precipitation (98.92 %) of RF in just 1 min. Also, it has been observed that extraction efficiency of [BMIM][PF 6 ] is maximum at pH = 8.

Chiral recognition in liquid chromatography (LC) generally requires relatively strong interactions between the analyte and the chiral stationary phase, often in combination with steric interactions. Hence most LC enantiomeric separations favor compounds that have hydrogen bonding groups, aromatic rings, strong dipoles, possibilities for 7r-m or charge transfer interactions, etc. Compounds with little or no functionality are usually difficult to resolve by LC methods. Conversely gas chromatography (GC) has been very useful in resolving compounds with limited functionality, including hydrocarbons. In this sense GC has been very complementary to LC methodologies. In this work the enantiomeric separation of hydrocarbons by reversed-phase LC is described. It appears that chiral recognition results largely from "shape-selectivity" (i.e., the tight fit of a hydrophobic moiety into a hydrophobic cavity) with few other substantial contributing interactions. Small amounts of methyl rerr.-butyl ether greatly enhanced the separation efficiency. All commercial samples contain significant quantities of enantiomeric impurities.

Within the last decade, ionic liquids have come to the fore as environmentallyresponsible designer solvents. But what are ionic liquids and what can they offer the analytical scientist? This article addresses these questions and chronicles recent progress made in the application of ionic liquids toward analytical problem-solving. While further progress is required before ionic liquids become mainstream analytical solvents, results to date commend their use in various modes of chemical analysis. It is our aim that the findings reported herein draw other researchers into this area and encourage the increased application of ionic liquids in this manner.

Ionic liquids (ILs) have elicited considerable attention in the field of gas absorption and separation due to their unique properties. In addition to absorption capacity and absorption rate, absorption enthalpy is an important indicator for sorbent evaluation. In this work, the absorption enthalpy of CO 2 in several kinds of ILs was measured directly using a Calvet calorimeter. The effects of anions, cationic alkyl chain length, and temperature on absorption properties were discussed. Results showed that anions influenced CO 2 absorption enthalpy considerably. 1-Butyl-3-methylimidazolium acetate presented the most appropriate enthalpy for CO 2 absorption compared with the other ILs investigated with different chain lengths. Absorption enthalpy was dependent on temperature, and the isosteric absorption enthalpy decreased with an increase in temperature. This work provides a useful basis for the appropriate selection of alternative forms of IL sorbents for post-combustion CO 2 capture technology.

Amperometric NO2 sensors with a new type of printed solid polymer electrolyte and printed carbon working electrodes were developed. The electrolytes consisted of the ionic liquids 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide [EMIM][N(Tf)2], 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM][CF3SO3], and 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM][BF4], which were immobilized in a poly(vinylidene fluoride) (PVDF) matrix. The analyte, gaseous nitrogen dioxide, was detected by reduction at-500 mV vs. the platinum pseudoreference electrode. The sensors showed linear behavior over the whole tested range, i.e., 0-5 ppm, and their sensitivities were in the order of hundreds of nanoamperes per one ppm of NO2. The sensor sensitivity was influenced by the electrical conductance of the electrolyte; the higher the conductance, the greater the sensor sensitivity. The rise/recovery times were of the order of tens of seconds. The use of screen printing technology for the preparation of the solid electrolyte and the carbon working electrode simplifies sensor fabrication without a negative effect on sensor performance.

Water immiscible ionic liquid 1-dodecyl-3-methylimidazolium tetrafluoroborate (DMIM-BF 4) and its inclusion complex with β-cyclodextrin (β-CD) in molar ratio 1:1 have been synthesized. The formation of DMIM-BF 4 /β-CD complex was confirmed by FT-IR analysis, 1 H NMR analysis, and differential scanning calorimetry data. Our results indicate that the aliphatic tail of DMIM-BF 4 is included into β-CD inner cavity whereas imidazolium ring is located outside the torus. Moreover, the weak interaction between polar components of ionic liquid and hydrophilic outer surface of β-CD has also been detected. The standard agar disk diffusion method was performed to evaluate antimicrobial efficiency of the obtained compounds against Staphylococcus aureus (ATCC-25923), Escherichia coli (ATCC-25922) and Pseudomonas aeruginosa (ATCC-27853), Candida albicans (M 885 ATCC 10231) and its clinical isolate test-cultures. It has been found that both DMIM-BF 4 and DMIM-BF 4 /β-CD complex possess high antimicrobial activity as revealed by similar zone inhibition values against all tested microorganisms. The acute toxicity studies on Danio rerio (zebrafish) model organism showed that the pure ionic liquid DMIM-BF 4 is slightly toxic compound having LD 50 value of 7 mg/L, 2 whereas DMIM-BF 4 /β-CD complex has considerably reduced toxicity (LD 50 = 100 mg/L) and therefore have potentially wider application areas.

A rapid test of whether a laboratory sample contains any microorganisms is important and necessary for many areas of science and technology. Currently, most of the standard procedures for the detection of aerobic bacteria, anaerobic bacteria and fungi, require the preparation of microbial cultures in respective growth media, which are dramatically slow. Different approaches providing fast analysis such as CE are becoming more desired. To compensate for the natural electrophoretic heterogeneity of microbes, various buffer additives were examined to stack all bacteria and fungi in a sample plug into a single peak. This peak was removed from the molecular contaminants in the sample to prevent false positives. Both cationic surfactants and ionic liquids (IL) were investigated as run buffer additives and they are both widely applicable to different species of bacteria and fungi. Given that high concentrations of surfactants can potentially lyse cells, dicationic IL offer attractive auxil...

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. www.elsevier.com/locate/talanta Evaluation of 11 ionic liquids as potential extraction solvents for benzodiazepines from whole blood using liquid-liquid microextraction combined with LC-MS/MS.

Room temperature ionic liquids (RTIL) are molten salts starting to be used as nonmolecular solvents in separation methods mainly for their extremely low vapor pressure and thermal stability. RTILs are formed by an anion associated to a cation. This intrinsic structure gives them a dual nature. When used as additives in RPLC mobile phases to enhance basic compound separation, RTILs lose their particular physicochemical properties to become just salts. However, a given RTIL is not equivalent to another one made with the same cation. It is shown that both the anion and the cation contribute to solute retention and peak efficiency extending beyond simple "salting-out" or ion-pairing effects. Nine different alkylmethyl-imidazolium ionic liquids with different alkyl chain length and chloride or BF 4or PF 6anions were used as additives (50 mM max. conc.) in the liquid chromatography separation of some cationic basic solutes on a Kromasil C 18 column. It is shown with sodium salts and an acetonitrile-water 30/70 v/v mobile phase that anions can adsorb on the stationary phase surface according to their lyotropic character. They can also form ion pairs with the cationic basic solutes. Alkyl-imidazolium cations also adsorb on the C 18 bonded stationary phase due to hydrophobic character depending on their alkyl chain length. Anion adsorption dramatically increases the cationic solute retention factors when cation adsorption decreases them. The cation adsorption is mainly responsible for peak shape and efficiency enhancements. RTILs are additives that enhance the basic cationic solute peak shape changing peak position. A wise choice of the appropriate combination of anion lyotropy with imidazolium cation hydrophobicity allows playing with solute selectivity and analysis duration.

A comparative study of peak shape, elution behavior, elution strength and resolution of seven ␤-blockers (acebutolol, alprenolol, labetalol, metoprolol, nadolol, pindolol and propranolol) chromatographed with aqueous-organic mobile phases containing additives such as the ionic liquid (IL) 1-butyl-3-methylimidazolium (BMIM BF 4) or triethylamine (TEA) is performed using a conventional reversed-phase Kromasil C 18 column and isocratic elution. The efficiencies and asymmetry factors achieved for the group of ␤-blockers in the Kromasil C 18 column improve when the cationic modifiers are added to the aqueous-organic mobile phase as competing additives for the silanol active sites. BMIM BF 4 is a significantly better additive compared to TEA. The improvement is more notably for the asymmetry factor, BMIM BF 4 allowing to obtain higher plate numbers than TEA at the same concentration. The effects of both modifiers on elution strength and retention factors are, however, different. TEA decreases the solute retention factors when BMIM BF 4 does not change them significantly. Using other additives taken in the IL family such as 1-butyl-3methylimidazolium hexafluorophosphate and 1-octyl-3-methylimidazolium tetrafluoroborate (OMIM BF 4), it is shown that the silanol screening effect is always observed, due to the IL cation, when it is possible to increase or to decrease the solute retention factors playing with the hydrophobic nature or chaotropic character of its anion.

The negative-ion mode of electrospray ionization mass spectrometry (ESI-MS) is intrinsically less sensitive than the positive-ion mode. The detection and quantitation of anions can be performed in positive-ion mode by forming specific ion-pairs during the electrospray process. The paired-ion electrospray ionization (PIESI) method uses specially synthesized multifunctional cations to form positively charged adducts with the anions to be analyzed. The adducts are detected in the positive-ion mode and at higher m/z ratios to produce excellent signal-tonoise ratios and limits of detection that often are orders of magnitude better than those obtained with native anions in the negative-ion mode. This review briefly summarizes the different analytical approaches to detect and separate anions. It focuses on the recently introduced PIESI method to present the most effective dicationic, tricationic, and tetracationic reagents for the detection of singly and multiply charged anions and some zwitterions. The mechanism by which specific structural molecular architectures can have profound effects on signal intensities is also addressed.

h i g h l i g h t s g r a p h i c a l a b s t r a c t 14 newly synthesized dicationic ionic liquids varying by the anion. A McReynolds polarity passing 6000 or polarity number of 143. Strong selectivity differences between polar and apolar solutes. Anthracene eluting BEFORE phenanthrene showing unique shape selectivity.

Two mixtures of four 1-alkyl-3-methylimidazolium ionic liquids (ILs) salts associated to the anions tetrafluoroborate or hexafluorophosphate were analyzed by reversed-phase liquid chromatography with three different stationary phases: Kromasil C 8 , Zorbax Extend C 18 and Zorbax Sb-Aq. The effect on retention of various inorganic salts (NaCl, NaH 2 PO 4, NaBF 4 , NaClO 4 and NaPF 6) added to acetonitrile/water mobile phases was studied. The three columns gave similar separation profiles. In all cases, the retention of ILs increased with the increasing affinity of the inorganic anions for the apolar stationary phases; a phenomenon called chaotropicity. The chaotropic anion order is Cl − ∼ H 2 PO 4 − < BF 4 − ∼ ClO 4 − < PF 6 −. It is established that the presence of chaotropic anions in the mobile phase do not permit to differentiate between ILs associated to different anions. However, chloride or dihydrogenphosphate added salts do not fully screen the retention differences between ILs associated with different anions. Distorted and even split peaks may appear in the chromatogram depending on the nature and concentration of the injected ILs. In the RPLC analysis of imidazolium-based IL, it is recommended to add to the mobile phase significant amounts of a salt containing a chaotropic anion. This salt addition will improve the IL peak shapes and give reproducible retention factors. LODs in the low microgram range (∼5 nmol) were obtained with the Kromasil C 8 column with a 50/50 acetonitrile-water mobile phase containing 0.01 M NaPF 6 added salt and 230 nm UV detection.

Eleven 1-alkyl-3-methyl imidazolium ionic liquid (IL) salts were analyzed in reversed phase mode with a Kromasil C 18 column. The mobile phases were water-rich acetonitrile solutions (water content ≥70%, v/v) without any added salts. It is shown that it is possible to separate different ILs sharing the same cation and differing by the anion when salt-free mobile phases are used. When a buffer, acetate or phosphate salt, or any salt, such as sodium chloride or sodium tetrafluorobarate, is added to the mobile phase, the ILs differing only by their anions cannot be separated. ILs with different alkyl chains in the imidazolium cation are separated by mobile phases with or without added salts following a hydrophobic interaction behavior: log k is proportional to n C , the carbon number of the alkyl chain. Important differences in ion/stationary phase interactions are observed depending on the ionic content of the mobile phase. With salt-free mobile phases, the IL/C 18 stationary phase interactions correspond to concave isotherms associated with fronting peaks for all ILs. With mobile phase containing 0.01 M of salt, tailing IL peaks correspond to convex adsorption isotherms. Also, the IL retention factor depends on the concentration and nature of the added salt. Hexafluorophosphate chaotropic anions can adsorb on the Kromasil C 18 surface dramatically increasing the imidazolium cation retention factors.

The chromatographic behavior of protonated amines in reversed-phase liquid chromatography (RPLC) is influenced markedly by the identity of the mobile-phase anion. For example, retention factor values, k, obtained from protonated nordoxepin, nortriptyline, and amitriptyline increase almost 1 order of magnitude across the following series of anions employed as mobile-phase modifiers: H 2 PO 4-< HCOO-< CH 3 SO 3-< Cl-< NO 3-< CF 3 COO-< BF 4-< ClO 4-< PF 6-. Early eluting primary, secondary, and tertiary benzylamines are retained and resolved using BF 4-, ClO 4-, and PF 6but elute in or very near the void using all other mobile-phase anions tested. In contrast, a neutral hydrophobic marker, acenaphthene, shows no significant changes in retention with mobile-phase anion identity. Such large differences in amine retention with anion identity can be rationalized via both an ion-pairing model and the Hofmeister effect. Two key findings are reported. First, the dependence of amine retention on mobile-phase anion identity is attributed unambiguously to the Hofmeister effect and is quantified using a simple equation based solely on differences in the solvation of anions. Accurate prediction of k values from the excess chemical potential of anions in water suggests that anionsolvent interactions dominate the retention of amines in RPLC. Thus, controlling amine retention depends critically on judicious selection of mobile-phase anion (in addition to the usual experimental parameters such as organic modifier, temperature, pH, and stationary phase). Second, more lipophilic molecular anions can provide retention and tailing properties comparable to those obtained from traditional amphiphilic ion-pairing reagents such as octanesulfonate, but with the benefit of a superior gradient background and solubility at high concentrations of organic modifier.

The development of efficient CO2 capture and utilization technologies driven by renewable energy sources is mandatory to reduce the impact of climate change. Herein, seven imidazolium-based ionic liquids (ILs) with different anions and cations were tested as catholytes for the CO2 electrocatalytic reduction to CO over Ag electrode. Relevant activity and stability, but different selectivities for CO2 reduction or the side H2 evolution were observed. Density functional theory results show that depending on the IL anions the CO2 is captured or converted. Acetate anions (being strong Lewis bases) enhance CO2 capture and H2 evolution, while fluorinated anions (being weaker Lewis bases) favour the CO2 electroreduction. Differently from the hydrolytically unstable 1-butyl-3-methylimidazolium tetrafluoroborate, 1-Butyl-3-Methylimidazolium Triflate was the most promising IL, showing the highest Faradaic efficiency to CO (&gt;95%), and up to 8 h of stable operation at high current rates (−20 ...

Using the reaction field continuum model the dielectric spectra of three selected ionic liquids were converted to the solvation dynamics of coumarin 153. It is shown in detail that the inclusion of the static conductivity in this model is essential.

Abstract: This study focuses on the synthesis and characterization of the inclusion complex of β-Cyclodextrin (β-CD) with dicationic ionic liquid, 3,3&apos;-(1,4-Phenylenebis [methylene]) bis(1-methyl-1H-imidazol-3-ium) di(bromide) (PhenmimBr). The inclusion complex was prepared at room temperature utilizing conventional kneading technique. Proton (1H) NMR and 2D (1H–1H) COSY NMR were the primary characterization tools employed to verify the formation of the inclusion complex. COSY spectra showed strong correlations between protons of imidazolium and protons of β-CD which indicates that the imidazolium ring of PhenmimBr has entered the cavity of β-CD. UV absorption indicated that β-CD reacts with PhenmimBr to form a 2:1 β-CD-PhenmimBr complex with an apparent formation constant of 2.61 × 105 mol−2 L2. Other characterization studies such as UV, FT-IR, XRD, TGA, DSC and SEM studies were also used to further support the formation of the β-CD-PhenmimBr inclusion complex.

The development of efficient CO2 capture and utilization technologies driven by renewable energy sources is mandatory to reduce the impact of climate change. Herein, seven imidazolium-based ionic liquids (ILs) with different anions and cations were tested as catholytes for the CO2 electrocatalytic reduction to CO over Ag electrode. Relevant activity and stability, but different selectivities for CO2 reduction or the side H2 evolution were observed. Density functional theory results show that depending on the IL anions the CO2 is captured or converted. Acetate anions (being strong Lewis bases) enhance CO2 capture and H2 evolution, while fluorinated anions (being weaker Lewis bases) favour the CO2 electroreduction. Differently from the hydrolytically unstable 1-butyl-3-methylimidazolium tetrafluoroborate, 1-Butyl-3-Methylimidazolium Triflate was the most promising IL, showing the highest Faradaic efficiency to CO (&gt;95%), and up to 8 h of stable operation at high current rates (−20 ...

The Raman spectra of 1-decyl-3-methyl-imidazolium bromide ([C 10 mim][Br]) aqueous solutions have been measured while continuously increasing the water content in the system (0-100%). Principal component (PC) and 2D Raman correlation (2DCOR) analysis has been carried out, the main attention concentrating to the region of O-H stretching vibrations at 3100-3800 cm À1. The band structure has been resolved in the loadings on PC1 and PC2 as well as in 2DCOR spectra. It indicates the presence in the studied system of several nonequivalent states of water. Various states of water have been also revealed in the 1 H NMR spectra. They have been assigned to non-bonded or weakly H-bonded water molecules, those involved in the fast isotropic reorientational motion as well as in the H-bond exchange processes and finally-water in the LC ionogel structures. The last contributes the 1 H NMR line shape typical for anisotropic liquids with zero biaxiality (asymmetry) of magnetic shielding and the chemical shift anisotropy of ca 0.6 ppm. The borders of the liquid crystalline (LC) ionogel phase have been determined using the concentration dependence of the integral intensities of Raman bands and the scores on PC1.

Ionic liquids and polymeric ionic liquids in solid-phase extraction 16 Ionic liquids and polymeric ionic liquids in solid-phase microextraction Liquid-phase (micro)extraction 18 Ionic liquids and magnetic ionic liquids in dispersive liquid-liquid 19 microextraction 20 Ionic liquid dispersive liquid-liquid microextraction 21 Magnetic ionic liquid dispersive liquid-liquid microextraction 22 Ionic liquids and magnetic ionic liquids in single-drop microextraction 23 Ionic liquids in hollow fiber liquid-phase microextraction 24 Two phase ionic liquid-hollow fiber liquid-phase microextraction 25 Three phase ionic liquid-hollow fiber liquid-phase microextraction 26 Ionic liquids and magnetic ionic liquids in aqueous biphasic systems 27 Chromatographic and electrophoretic separations 28 Gas chromatography 29 Monocationic ionic liquid-based stationary phases 30 Di-and polycationic ionic liquid-based stationary phases 31 Polymeric ionic liquid-based stationary phases 32 Metal-containing ionic liquid-based stationary phases 33 Commercial ionic liquid-based stationary phases 34

Highlights o This paper presents the studies of triplettriplet energy transfer (TET) and electron transfer reactions (ET) reactions involving long lived triplet states and radical anions, respectively, in conventional solvents, SDS micelle and RTIL solvents, namely, 1-alkyl-3-methyl-imidazoliumtetrafluoroborate ([CMIM][BF4], in which the chain length of the alkyl group is varied up to ten carbon atoms. 3 nonpolar pockets, the diffusive motion of the reactants experiences much smaller microscopic viscosity as compared to the bulk or macroscopic viscosity of the solution. However, if one of two reactants is ionic and the other is nonionic, they reside at ionic and nonionic pockets of the RTIL solution, respectively, and the motion of the reactants occur through different regions of the RTIL solution. Therefore, the reactants experience the macroscopic viscosity of the solution and the reaction rates show a linear relationship with inverse of viscosity of the solution (Smoluchowski equation). Present study clearly establishes the inherent microscopic heterogeneities in room temperature ionic liquids (RTILs), which have been the subject of intense discussion in recent times.

The ionic liquids (ILs) are salts with melting points below 100 °C. These are called as ionic fluids, ionic melts, liquid electrolytes, fused salts, liquid salts, ionic glasses, designer solvents, green solvents and solvents of the future. These have a wide range of applications including medical, pharmaceutical and chemical sciences. Nowadays, their use is increasing greatly in separation science, especially in chromatography and capillary electrophoresis due to their remarkable properties. The present article describes the importance of ILs in high performance liquid chromatography and capillary electrophoresis. Efforts were also made to highlight the future expectations of ILs.

The partition coefficients, P IL/w , of several compounds, some of them of biological and pharmacological interest, between water and room-temperature ionic liquids based on the imidazolium, pyridinium, and phosphonium c a t i o n s , n a m e l y 1-o c t y l-3-m e t h y l i m i d a z o l i u m h e x a f l u o r o p h o s p h a t e , No c t y l p y r i d i n i u m tetrafluorophosphate, trihexyl(tetradecyl)phosphonium chloride, trihexyl(tetradecyl)phosphonium bromide, t r i h e x y l (t e t r a d e c y l) p h o s p h o n i u m b i s (t r i f l u o r o m e t h y l s u l f o n y l) i m i d e , a n d trihexyl(tetradecyl)phosphonium dicyanamide, were accurately measured. In this way, we extended our database of partition coefficients in room-temperature ionic liquids previously reported. We employed the solvation parameter model with different probe molecules (the training set) to elucidate the chemical interactions involved in the partition process and discussed the most relevant differences among the three types of ionic liquids. The multiparametric equations obtained with the aforementioned model were used to predict the partition coefficients for compounds (the test set) not present in the training set, most being of biological and pharmacological interest. An excellent agreement between calculated and experimental log P IL/w values was obtained. Thus, the obtained equations can be used to predict, a priori, the extraction efficiency for any compound using these ionic liquids as extraction solvents in liquid-liquid extractions.

Ionic liquids show great promise as excellent solvents or catalysts in energy and biological fields due to their unique chemical and physical properties. In this work, the characteristics of various ionic liquids are investigated with the electrophoresis of a charged droplet (ECD) method. Under normal situation, a charged droplet in a dielectric liquid shows back-and-forth bouncing motion between the positive and negative electrodes continuously. However, for some special ionic liquids, interesting retreating behavior of a charged droplet has been observed. This retreating behavior is due to the loss of positive charges of the droplet, and it suggests that only the positive ions are extracted from the droplet under the applied electric field. Based on this hypothesis of ion extraction, Fourier transform infrared (FTIR) spectroscopy analysis has been performed. The retreating behavior is also discussed from the intermolecular point of view according to the ion species.

Nicotine and cotinine are very polar basic molecules, which makes it difficult to analyze them by reversed-phase liquid chromatography (RPLC), especially in biological samples. Additives with an ionic character have been traditionally used in RPLC as silanol suppressors. The aim of our study was to investigate the potential of selected ionic liquids in improving chromatographic performance in comparison with common additives. The experimental design was conducted using the following ionic liquids as the mobile phase modifiers: 1-butyl-3-methylimidazolium tetrafluoroborate, BMIM[BF4] and 1-butyl-3-methylimidazolium hexafluorophosphate BMIM[PF6], with a C18 chromatographic column. The separation of these alkaloids on silica-based RPLC stationary phases was successfully conducted by the addition of BMIM[BF4] in an acetonitrile:phosphate-buffer-based mobile phase in a pH range of 2.3–5.2. The presented chromatographic method can be used as alternative for monitoring studies or pharmacok...

Nicotine and cotinine are very polar basic molecules, which makes it difficult to analyze them by reversed-phase liquid chromatography (RPLC), especially in biological samples. Additives with an ionic character have been traditionally used in RPLC as silanol suppressors. The aim of our study was to investigate the potential of selected ionic liquids in improving chromatographic performance in comparison with common additives. The experimental design was conducted using the following ionic liquids as the mobile phase modifiers: 1-butyl-3-methylimidazolium tetrafluoroborate, BMIM[BF4] and 1-butyl-3-methylimidazolium hexafluorophosphate BMIM[PF6], with a C18 chromatographic column. The separation of these alkaloids on silica-based RPLC stationary phases was successfully conducted by the addition of BMIM[BF4] in an acetonitrile:phosphate-buffer-based mobile phase in a pH range of 2.3–5.2. The presented chromatographic method can be used as alternative for monitoring studies or pharmacok...

We present a new family of ionic liquids (ILs) with a common cation, 1-butyl-3-methyl imidazolium, the popular [BMIM] + (also written C 4 C 1 Im +) and a variety of anionic complexes (also called adducts) based in thiocyanate (SCN)-: one blank compound, BMIM(SCN), and ten doped with metals having different oxidation states:

In recent years, materials science has propelled to the research forefront. Ionic liquids with unique and fascinating properties have also left their footprints to the developments of materials science during the last years. In this review we highlight some of their recent advances and provide an overview at the current status of ionic liquid-modified materials applied in solid-phase extraction, liquid and gas chromatography and capillary electrochromatography with reference to recent applications. In addition, the potential of ionic liquids in the modification of capillary inner wall in capillary electrophoresis is demonstrated. The main target material modified with ionic liquids is silica, but polymers and monoliths have recently joined the studies. Although imidazolium is still clearly the most commonly used ionic liquid for the covalently modification of materials, the exploitation of pyridinium and phosphonium will most probably increase in the future.

A high-throughput method for the production of solid-phase microextraction (SPME) sorbent coatings via ultraviolet (UV) photoinitiated copolymerization of ionic liquid (IL) monomers on a fused silica support is described. The copolymerization of monocationic and dicationic IL crosslinkers was performed "on-fiber" using UV initiated free radical polymerization. Mixtures composed of various amounts of the IL cross-linker, UV initiator (DAROCUR 1173), and IL monomer were dip-coated onto an etched and derivatized fused silica support and placed in a high-capacity UV reactor. The method requires no organic dispersive solvent and is much more rapid compared to traditional methods in which polymeric ionic liquid (PIL) sorbent coatings are prepared by 2,2′azobis(2-methylpropionitrile) (AIBN)-initiated polymerization. Two ionic liquid-based cross-linkers, namely, 1,8-di (3vinylimidazolium) octane dibromide ([(VIM) 2 C 8 ] 2[Br]) and 1,12-di (3-vinylimidazolium) dodecane dibromide ([(VIM) 2 C 12 ] 2[Br]), were copolymerized with an ionic liquid monomer, 1-vinyl-3-hexylimidazolium chloride ([VHIM][Cl]), to produce polar cross-linked PIL-based SPME sorbent coatings. The cross-linking and immobilization of these coatings make them particularly applicable in direct immersion SPME. The coatings were applied in the extraction of polar analytes, including alcohols, aldehydes, and esters, from aqueous solutions using headspace and direct immersion SPME gas chromatography mass spectrometry (GC/ MS). Compared to linear PIL-based sorbent coatings containing the same anions, the cross-linked PIL-based coatings exhibited higher thermal stability and lower bleed, making them ideal for GC/MS. Recovery experiments were performed in deionized, well, and river water. The structural integrity of the sorbent coatings, as well as their analytical precision, was not diminished after 90 extractions from complex samples using headspace and direct immersion SPME.

The present work has been undertaken with an objective to understand the differences in the local structural organization of the imidazolium-based monocationic ionic liquids (MILs) and dicationic ionic liquids (DILs) through resonance energy transfer (RET) studies. In this study, neat ILis used as donor and a charged species rhodamine 6G (R6G) is used as the acceptor unit due to the fact that they satisfy the spectroscopic criteria that are needed for RET event to take place. Additionally, R6G being charged species is expected to facilitate the electrostatic interactions with the ILs which are also charged. Specifically, two-imidazolium-based germinal DILs, and their monocationic counterparts are used for the present investigations. Additionally, the studies are carried out in some selected MILs where lengths of the alkyl side chains are kept unchanged for MILs and DILs. Interestingly, the present data reveal that the RET interaction is more favorable for DILs than for MILs even though the DILs are relatively bulkier than their monocatioinic counterparts. More interestingly, RET interaction is also found to be more favorable for DILs than for those MILs where the length of alkyl group is kept fixed for MILs and DILs. The result of the present study delineates that the length of the alkyl chain length on the cation is not the sole factor contributing to the RET outcomes for DILs and MILs but the local structure of DILs also contribute significantly to the same. The current investigation clearly indicates DILs have a more compact local structure than that of MILs. Essentially, the current study highlights that a cost effective, noninvasive technique such as RET is quite effective in capturing the differences in the nano-structural organization of MILs and DILs.

Egg shell (ES) is a biological macromolecule mainly containing calcite embedded in proteins and polysaccharides, while shell membrane predominantly contains proteins. Thus ES with membrane (ESM) possesses richer protein contents than ES. In the present work, ES and ESM have been separately modified using mono-and di-cationic imidazolium ionic liquids, [C 5 mim + ][Br-] (IL) and [Bis-(PhCH 2 MIm) + ][2Cl-] (DIL). Thus four modified products have been obtained namely ES-IL, ES-DIL, ESM-IL and ESM-DIL. In order to determine physico-chemical modifications of the ES due to the interactions with the ionic liquids, the structural, spectroscopic and thermal properties of all products were investigated by means of XRD, FTIR and TG/DTA. The IR spectra display significant changes in the 1400-1550 and 2800-3100 cm-1 regions confirming the insertion of IL and DIL into the ES and ESM layers. Furthermore, the XRD results indicate that this modification process influence the crystal structure of the ES. Thermal analysis suggests that the chemical modification increases the thermal stability of the ES and ESM. It has also been ascertained that presence of proteins in the shell membrane is responsible for increasing thermal stability in the order ES < ESM < ES-IL < ESM-IL < ES-DIL < ESM-DIL.