Ionic liquids as advantageous solvents for headspace gas chromatography of compounds with low vapor pressure

Seaweed Polysaccharide Based Products and Materials: An Assessment on Their Production from a Sustainability Point of View

Among the various natural polymers, polysaccharides are one of the oldest biopolymers present on the Earth. They play a very crucial role in the survival of both animals and plants. Due to the presence of hydroxyl functional groups in most of the polysaccharides, it is easy to prepare their chemical derivatives. Several polysaccharide derivatives are widely used in a number of industrial applications. The polysaccharides such as cellulose, starch, chitosan, etc., have several applications but due to some distinguished characteristic properties, seaweed polysaccharides are preferred in a number of applications. This review covers published literature on the seaweed polysaccharides, their origin, and extraction from seaweeds, application, and chemical modification. Derivatization of the polysaccharides to impart new functionalities by chemical modification such as esterification, amidation, amination, C-N bond formation, sulphation, acetylation, phosphorylation, and graft copolymerization is discussed. The suitability of extraction of seaweed polysaccharides such as agar, carrageenan, and alginate using ionic solvent systems from a sustainability point of view and future prospects for efficient extraction and functionalization of seaweed polysaccharides is also included in this review article.

Controlled deuterium labelling of imidazolium ionic liquids to probe the fine structure of the electrical double layer using neutron reflectometry

The electrical double layer structure formed in an ionic liquid electrolyte was determined by combining the neutron reflectivity and deuterium labelling techniques.

Ionic Liquid-Assisted Laser Desorption/Ionization-Mass Spectrometry: Matrices, Microextraction, and Separation

Ionic liquids (ILs) have advanced a variety of applications, including matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS). ILs can be used as matrices and solvents for analyte extraction and separation prior to analysis using laser desorption/ionization-mass spectrometry (LDI-MS). Most ILs show high stability with negligible sublimation under vacuum, provide high ionization efficiency, can be used for qualitative and quantitative analyses with and without internal standards, show high reproducibility, form homogenous spots during sampling, and offer high solvation efficiency for a wide range of analytes. Ionic liquids can be used as solvents and pseudo-stationary phases for extraction and separation of a wide range of analytes, including proteins, peptides, lipids, carbohydrates, pathogenic bacteria, and small molecules. This review article summarizes the recent advances of ILs applications using MALDI-MS. The applications of ILs as matrices, solvents, and pseudo-stationary phases, are also reviewed.

Ionic liquid based microextraction of targeted lipids from serum using UPLC-MS/MS with a chemometric approach: a pilot study

An ionic liquid based vortex assisted surfactant-enhanced emulsification microextraction method followed by using liquid chromatography-electrospray mass spectrometry have been used for the determination of fatty acids, triglycerides and phospholipids in serum samples.

Estimation of Lattice Enthalpies of Ionic Liquids Supported by Hirshfeld Analysis

New measurements of vaporization enthalpies for 15 1:1 ionic liquids are performed by using a quartz-crystal microbalance. Collection and analysis of 33 available crystal structures of organic salts, which comprise 13 different cations and 12 anions, is performed. Their dissociation lattice enthalpies are calculated by a combination of experimental and quantum chemical quantities and are divided into the relaxation and Coulomb components to give an insight into elusive short-range interaction enthalpies. An empirical equation is developed, based on interaction-specific Hirshfeld surfaces and solvation enthalpies, which enables the estimation of the lattice enthalpy by using only the crystal-structure data.

Periodic mesoporous organosilica with ionic liquid framework as a novel fiber coating for headspace solid-phase microextraction of polycyclic aromatic hydrocarbons

Periodic mesoporous organosilica based on alkylimidazolium ionic liquid (PMO-IL) was prepared and used as a highly porous fiber coating material for solid-phase microextraction (SPME). The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the SPME fiber. The fiber was evaluated for the extraction of some polycyclic aromatic hydrocarbons (PAHs) from aqueous sample solutions in combination with gas chromatography-mass spectrometry (GC-MS). A one at-the-time optimization strategy was applied for optimizing the important extraction parameters such as extraction temperature, extraction time, ionic strength, stirring rate, and desorption temperature and time. In optimum conditions, the repeatability for one fiber (n=3), expressed as relative standard deviation (R.S.D.%), was between 4.3% and 9.7% for the test compounds. The detection limits for the studied compounds were between 4 and 9 pg mL(-1). The developed method offers the advantage of being simple to use, with shorter analysis time, lower cost of equipment, thermal stability of fiber and high relative recovery in comparison to conventional methods of analysis.

NMR study of cation dynamics in three crystalline states of 1-butyl-3-methylimidazolium hexafluorophosphate exhibiting crystal polymorphism

We investigate the cation rotational dynamics of a room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium hexafluorophosphate ([C(4)mim]PF(6)) in its three crystalline states by (1)H NMR spectroscopy. Spin-lattice and spin-spin relaxation time (T(1) and T(2), respectively) measurements as a function of temperature confirm the presence of three polymorphic crystals of [C(4)mim]PF(6): crystals α, β, and γ, which we previously discovered using Raman spectroscopy and calorimetry. Second moment calculations of (1)H NMR spectra reveal that certain segmental motions of the butyl group in addition to the rapid rotation of the two methyl groups in the cation occur in all the crystals. The trend in the mobility of the segmental motions is γ < β ≤ α, which is consistent with the strength of cation-anion interactions (or crystal packing density) estimated from high-frequency Raman scattering experiments. T(1) measurements demonstrate two types of rotational motions on the nanosecond time scale in all three crystals: fast and slow motions. The three crystals have similar activation energies of 12.5-15.1 kJ mol(-1) for the fast motion, which is assigned to the rotation of the methyl group at the terminal of the butyl group. These observed activation energies were consistent with that estimated by quantum chemical calculations in the gas phase (11.9 kJ mol(-1)). In contrast, the slow motions of crystals α and γ are attributed to different segmental motions of the butyl group and that of crystal β to either a little segmental motion or a certain PF(6)(-) rotational motion. These nanosecond rotational motions obtained from the T(1) measurements do not appear to be affected by crystal packing density because local interactions in the crystalline state rather than packing density govern such nanosecond motions. With respect to the segmental motions, the mobility is likely to change significantly with the conformation of the butyl group. On the basis of these findings, crystal γ, which is the only crystalline phase previously determined using single-crystal X-ray diffraction, is considered to be the most stable phase because of the slowest segmental motions and the strongest cation-anion interactions.

Ionic liquids as superior solvents for headspace gas chromatography of residual solvents with very low vapor pressure, relevant for pharmaceutical final dosage forms

1-n-Butyl-3-methylimidazolium dimethyl phosphate (BMIM DMP) was identified as the most suitable ionic liquid as solvent for the headspace gas chromatographic analysis of solvents with very low vapor pressure such as dimethylsulfoxide, N-methylpyrrolidone, sulfolane, tetralin, and ethylene glycol in a realistic matrix of commonly used excipients (carboxymethylcellulose, magnesium stearate, guar flour, and corn starch) in pharmaceutical products. Limits of quantification and limits of detection were in the low microgram per gram range. The detection of traces of sulfolane in a real sample of tablets containing the drug cefpodoxim proxetil demonstrated the applicability of the method.

Application of ionic liquids in high performance reversed-phase chromatography

Ionic liquids, considered “green” chemicals, are widely used in many areas of analytical chemistry due to their unique properties. Recently, ionic liquids have been used as a kind of novel additive in separation and combined with silica to synthesize new stationary phase as separation media. This review will focus on the properties and mechanisms of ionic liquids and their potential applications as mobile phase modifier and surface-bonded stationary phase in reversed-phase high performance liquid chromatography (RP-HPLC). Ionic liquids demonstrate advantages and potential in chromatographic field.

Preparation of ionic liquid based solid-phase microextraction fiber and its application to forensic determination of methamphetamine and amphetamine in human urine

A new solid-phase microextraction (SPME) procedure using an ionic liquid (IL) has been developed. Reusable IL-based SPME fiber was prepared for the first time by fixing IL through cross-linkage of IL impregnated silicone elastomer on the surface of a fused silica fiber. 1-Ethoxyethyl-3-methylimidazloium bis(trifluoromethane) sulfonylimide ([EeMim][NTf(2)]) ionic liquid was employed as a demonstration and the prepared fiber was applied to the forensic headspace determination of methamphetamine (MAP) and amphetamine (AP) in human urine samples. Important extraction parameters including the concentration of salt and base in sample matrix, extraction temperature and extraction time were investigated and optimized. Combined with gas chromatography/mass spectrometry (GC/MS) working in selected ion monitoring (SIM) mode, the new method showed good linearity in the range of 20-1500 microg L(-1), good repeatability (RSD<7.5% for MAP, and <11.5% for AP, n=6), and low detection limits (0.1 microg L(-1) for MAP and 0.5 microg L(-1) for AP). Feasibility of the method was evaluated by analyzing human urine samples. Although IL-based SPME is still at the beginning of its development stage, the results obtained by this work showed that it is a promising simple, fast and sensitive sample preparation method.

Ionic liquids in separation techniques

The growing interest in ionic liquids (ILs) has resulted in an exponentially increasing production of analytical applications. The potential of ILs in chemistry is related to their unique properties as non-molecular solvents: a negligible vapor pressure associated to a high thermal stability. ILs found uses in different sub-disciplines of analytical chemistry. After drawing a rapid picture of the physicochemical properties of selected ILs, this review focuses on their use in separation techniques: gas chromatography (GC), liquid chromatography (LC) and electrophoretic methods (CE). In LC and CE, ILs are not used as pure solvents, but rather diluted in aqueous solutions. In this situation ILs are just salts. They are dual in nature. Too often the properties of the cations are taken as the properties of the IL itself. The lyotropic theory is recalled and the effects of a chaotropic anion are pointed out. Many results can be explained considering all ions present in the solution. Ion-pairing and ion-exchange mechanisms are always present, associated with hydrophobic interactions, when dealing with IL in diluted solutions. Chromatographic and electrophoretic methods are also mainly employed for the control and monitoring of ILs. These methods are also considered. ILs will soon be produced on an industrial scale and it will be necessary to develop reliable analytical procedures for their analysis and control.

Ionic liquids in separations

Ionic liquids are liquids composed completely of ions. In the past two decades, ionic liquids have been widely used as "green solvents" replacing traditional organic solvents for organic synthesis and catalysis. In addition, ionic liquids are playing an increasingly important role in separation science. In this Account, the application of ionic liquids in all areas of separation science including extractions, gas chromatography, and supported liquid membrane processes are highlighted.

Surface confined ionic liquid as a stationary phase for HPLC

Trimethoxysilane "ionosilane" derivatives of room temperature ionic liquids based on alkylimidazolium bromides were synthesized for attachment to silica support material. The derivatives 1-methyl-3-(trimethoxysilylpropyl)imidazolium bromide and 1-butyl-3-(trimethoxysilylpropyl)imidazolium bromide were used to modify the surface of 3 microm diameter silica particles to act as the stationary phase for HPLC. The modified particles were characterized by thermogravimetric analysis (TGA) and (13)C and (29)Si NMR spectroscopies. The surface modification procedure rendered particles with a surface coverage of 0.84 micromol m(-2) for the alkylimidazolium bromide. The ionic liquid moiety was predominantly attached to the silica surface through two siloxane bonds of the ionosilane derivative (63%). Columns packed with the modified silica material were tested under HPLC conditions. Preliminary evaluation of the stationary phase for HPLC was performed using aromatic carboxylic acids as model compounds. The separation mechanism appears to involve multiple interactions including ion exchange, hydrophobic interaction, and other electrostatic interactions.