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The high abundance of cannabinoids within cannabis samples presents an issue for pesticide testing as cannabinoids are often co-extracted with pesticides using various sample preparation techniques. Cannabinoids may also chromatographically co-elute with moderate polarity pesticides and inhibit the ionization of pesticides when using mass spectrometry. To circumvent these issues, we have developed a new approach to isolate commonly regulated pesticides and cannabinoids from aqueous samples using tunable, crosslinked imidazolium polymeric ionic liquid (PIL)-based sorbent coatings for direct immersion solid-phase microextraction (DI-SPME). The selectivity of four PIL sorbent coatings towards 20 pesticides and six cannabinoids, including cannabidiol and Δ

A new class of magnetic ionic liquid (MIL) containing paramagnetic cations has been applied for in situ dispersive liquid-liquid microextraction in the determination of both polar and non-polar pollutants, including ultraviolet filters, polycyclic aromatic hydrocarbons, alkylphenols, a plasticizer and a preservative in aqueous samples. The MILs were based on cations containing Ni(II) metal centers coordinated with four N-alkylimidazole ligands and chloride anions. The MILs were capable of undergoing in situ metathesis reaction with the bis[(trifluoromethyl)sulfonyl]imide ([NTf2−]) anion during the microextraction procedure, generating a water-immiscible extraction solvent containing the preconcentrated analytes. The MIL was then isolated by magnetic separation, followed by direct analysis using reversed-phase high performance liquid chromatography with diode array detection. Among all of the studied MILs, those containing the N-butylimidazole and N-benzylimidazole ligands ([Ni(C4IM)42+]2[Cl-] and [Ni(BeIM)42+]2[Cl-], respectively) exhibited the best extraction performance. The method under optimum conditions required 5 mL of sample at pH 3, 20 mg of [Ni(C4IM)42+]2[Cl-] or 30 mg of [Ni(BeIM)42+]2[Cl-], 300 μL of acetone or acetonitrile as dispersive solvent (depending on the MIL), a 1:2 M ratio of MIL to [NTf2−], and 3 min of vortex. The developed method achieved higher extraction efficiency compared to the conventional MIL-dispersive liquid-liquid microextraction mode, with extraction efficiencies of 46.8–88.6% and 65.4–97.0% for the [Ni(C4IM)42+]2[Cl-] and the [Ni(BeIM)42+]2[Cl-] MILs (at a spiked level of 81 μg L-1), respectively, limits of detection down to 5.2 μg L-1, and inter-day relative standard deviation lower than 16%.

Choline chloride-based deep eutectic solvents (DESs) are immensely popular in organic synthesis, catalysis, electrochemistry, and separation science. A popular choice of hydrogen bond donor (HBD) among these DESs consists of both straight-chain and branched polyols that can incorporate additional functional groups, such as ether linkages. Previous studies have shown that the extraction efficiency is significantly altered when the molar ratio of HBD in choline chloride-based DES systems is varied, but no study has been able to relate it to their solvation characteristics. This is largely due to the limited sensitivity of existing solvatochromic dye techniques to detect minor changes in solvation interactions when the DES composition is varied. In this study, inverse gas chromatography was employed for the first time to investigate the variation in solvation properties for DESs comprised of choline salts as hydrogen bond acceptors (HBAs) and polyols as HBDs when their HBA/HBD ratio is systematically altered. Unlike many organic solvents, DES systems investigated in this work possessed a significant hydrogen bond character. It was observed that the hydrogen bond basicity generally plateaued at higher molar ratios of HBD while the hydrogen bond acidity was observed to be the highest at HBA/HBD ratios of 1:10 in all DESs. Amongst all solvents, neat HBDs (triethylene glycol and 1,8-octane diol) possessed the weakest hydrogen bond basicity since they lack the chloride anion that acts as the primary hydrogen bond acceptor. Results from this study demonstrate that the solvation characteristics of DESs are largely different from their starting materials while the HBA/HBD ratio further influences their solvation interactions that can in turn impact important parameters such as extraction yields.

Phosphonium-based ionic liquids (ILs) have proven to be successful stationary phases (SPs) for gas chromatography (GC) in several fields of application because of their unique selectivity and good chromatographic properties. This study focuses on the use of two ILs as GC SPs that are based on the phosphonium derivatives trihexyl(tetradecyl)phosphonium chloride ([P

In this study, an enhanced variant of magnetic ionic liquid (MIL)-based dispersive liquid-liquid microextraction is put forward. The procedure combines a water insoluble solid support and the [P66614+][Dy(III)(hfacac)4−] MIL, in a one-pot, pH-modulated procedure for microextraction of triazines (TZs) and sulfonamides (SAs). The solid supporting material was mixed with the MIL to overcome difficulties concerning the weighing of MIL and to control the uniform dispersion of the MIL, rendering the whole extraction procedure more reproducible. The pH-modulation during extraction step makes possible the one-pot extraction of SAs and TZs, from a single sample, in 15 min. Overall, the new analytical method developed enjoys the benefits of sensitivity (limits of quantification: 0.034–0.091 μg L-1) and precision (relative standard deviation: 5.2–8.1%), while good recoveries (i.e., 89–101%) were achieved from lake water and effluent from a municipal wastewater treatment plant. Owing to all of the above, the new procedure can be used to determine the concentrations of SAs and TZs at levels below the maximum residue limits.

A novel sorbent material, gold-polypyrrole (Au-PPy) nanocomposite-coated silica, is described for the efficient solid-phase extraction (SPE) of six common microcystins (MCs) well below the recommended United States EPA and World Health Organization (WHO) guidelines. With the optimized SPE protocol, samples spiked with MCs were determined at ng/L concentrations by liquid chromatography-mass spectrometry (LC–MS) in different aqueous sample matrices, including HPLC-grade, tap, and lake water. The average recoveries for all MCs tested in the three water matrices ranged from 94.1–103.2% with relative standard deviations (RSDs) of 1.6–5.4%, which indicated excellent extraction efficiency and reproducibility. Limits of detection (LODs) and limits of quantification (LOQs) for all MCs in both tap and lake water samples were determined to be ≤1.5 ng/L and 5.0 ng/L, respectively. The Au-PPy nanocomposite-coated sorbent material was reusable for at least three independent MC extractions with a single SPE cartridge in the concentration range of 10–500 ng/L. Importantly, off-column selective separation at the sample preparation and preconcentration stage between more hydrophilic and more hydrophobic MCs was achieved by sequential elution through changes in the solvent composition and SPE bed size. Therefore, the Au-PPy nanocomposite-coated silica sorbent is a promising new material for the quantification of MC variants in water samples.

The development of rapid, convenient, and high throughput sample preparation approaches such as liquid phase microextraction techniques have been continuously developed over the last decade. More recently, significant attention has been given to the replacement of conventional organic solvents used in liquid phase microextraction techniques in order to reduce toxic waste and to improve selectivity and/or extraction efficiency. With these objectives, non-conventional solvents have been explored in liquid phase microextraction and aqueous biphasic systems. The utilized non-conventional solvents include ionic liquids, magnetic ionic liquids, and deep eutectic solvents. They have been widely used as extraction solvents or additives in various liquid phase microextraction modes including dispersive liquid-liquid microextraction, single-drop microextraction, hollow fiber-liquid phase microextraction, as well as in aqueous biphasic systems. This review provides an overview into the use of non-conventional solvents in these microextraction techniques in the past 5 years (2012-2016). Analytical applications of the techniques are also discussed.

Deep eutectic solvents (DESs) have gained increasing popularity in separation science due to the fact that their physico-chemical properties can be easily fine-tuned by varying the type or ratio of hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD). While it is well-known that the molar ratio of HBA/HBD affects the melting point of a eutectic mixture, much less is understood regarding its effect on the magnitude of individual solvation interactions. This is largely due to the fact that established solvatochromic dye methods lack sensitivity when the HBA/HBD ratio is varied slightly in a eutectic mixture. Herein, this study is the first to measure the variation of DES solvation interactions with small changes in the molar ratio of HBA/HBD using inverse gas chromatography (IGC). Solute-solvent interactions of three different DES systems comprised of ammonium salts and organic acids were examined. The probe molecules were studied for 18 eutectic mixtures of varied HBA and HBD composition. DES hydrogen bond basicity, hydrogen bond acidity, and dispersive-type interactions exhibited the greatest change when the molar ratio of HBA/HBD was varied in the eutectic mixture. Results from this study demonstrate that the HBA/HBD ratio can be used to modulate the solvation characteristics for this class of DESs in separations and that the stoichiometric ratio of the HBA/HBD is important in ensuring their reproducible preparation.

Deep eutectic solvents (DESs) have emerged as alternatives to conventional organic solvents and ionic liquids (ILs). Their tunable and designer physio-chemical properties, low cost, and ease of preparation make them attractive solvent systems for use in extractions and additives to chromatographic separations. However, due to the diverse range of hydrogen bond acceptors and donors that comprise DESs, choosing the appropriate solvent for separations can be challenging. This review discusses all methods of DES preparation and details their advantages and disadvantages. Since polarity is an important aspect in their use in separations, the classification of DESs based on the betaine dye and nile red scales as well as Kamlet-Taft parameters is also discussed. Finally, a summary of applications of DESs in various extraction processes (phenolics, fuels, metals, proteins, carbohydrates), solid-phase extraction, solid-phase microextraction, as well as capillary electrochromatography is provided.

Structurally-tuned ionic liquids (ILs) have been previously applied as the second dimension column in comprehensive two-dimensional gas chromatography (GC × GC) and have demonstrated high selectivity in the separation of individual aliphatic hydrocarbons from other aliphatic hydrocarbons. However, the maximum operating temperatures of these stationary phases limit the separation of analytes with high boiling points. In order to address this issue, a series of polymeric ionic liquid (PIL)-based stationary phases were prepared in this study using imidazolium-based IL monomers via in-column free radical polymerization. The IL monomers were functionalized with long alkyl chain substituents to provide the needed selectivity for the separation of aliphatic hydrocarbons. Columns were prepared with different film thicknesses to identify the best performing stationary phase for the separation of kerosene. The bis[(trifluoromethyl)sulfonyl]imide ([NTf 2 ] − )-based PIL stationary phase with larger film thickness (0.28 μm) exhibited higher selectivity for aliphatic hydrocarbons and showed a maximum allowable operating temperature of 300 °C. PIL-based stationary phases containing varied amount of IL-based crosslinker were prepared to study the effect of the crosslinker on the selectivity and thermal stability of the resulting stationary phase. The optimal resolution of aliphatic hydrocarbons was achieved when 50% (w/w) of crosslinker was incorporated into the PIL-based stationary phase. The resulting stationary phase exhibited good selectivity for different groups of aliphatic hydrocarbons even after being conditioned at 325 °C. Finally, the crosslinked PIL-based stationary phase was compared with SUPELCOWAX 10 and DB-17 columns for the separation of aliphatic hydrocarbons in diesel fuel. Better resolution of aliphatic hydrocarbons was obtained when employing the crosslinked PIL-based stationary phase as the second dimension column.

Neat crosslinked polymeric ionic liquid (PIL) sorbent coatings for solid-phase microextraction (SPME) compatible with high-performance liquid chromatography (HPLC) are reported for the first time. Six structurally different PILs were crosslinked to nitinol supports and applied for the determination of select pharmaceutical drugs, phenolics, and insecticides. Sampling conditions including sample solution pH, extraction time, desorption solvent, desorption time, and desorption solvent volume were optimized using design of experiment (DOE). The developed PIL sorbent coatings were stable when performing extractions under acidic pH and remained intact in various organic desorption solvents (i.e., methanol, acetonitrile, acetone). The PIL-based sorbent coating polymerized from the IL monomer 1-vinyl-3-(10-hydroxydecyl) imidazolium chloride [VC10OHIM][Cl] and IL crosslinker 1,12-di(3-vinylbenzylimidazolium) dodecane dichloride [(VBIM)2C12] 2[Cl] exhibited superior extraction performance compared to the other studied PILs. The extraction efficiency of pharmaceutical drugs and phenolics increased when the film thickness of the PIL-based sorbent coating was increased while many insecticides were largely unaffected. Satisfactory analytical performance was obtained with limits of detection (LODs) ranging from 0.2 to 2 μg L(-1) for the target analytes. The accuracy of the analytical method was examined by studying the relative recovery of analytes in real water samples, including tap water and lake water, with recoveries varying from 50.2% to 115.9% and from 48.8% to 116.6%, respectively.

Novel cross-linked polymeric ionic liquid (PIL) bucky gels were formed by free-radical polymerization of polymerizable ionic liquids gelled with multi-walled carbon nanotubes (MWCNT) and used as sorbent coatings for solid-phase microextraction (SPME). The combination of PIL with MWCNTs significantly enhanced the π–π interaction between the sorbent coatings and the aromatic analytes. Compared to the neat PIL-based sorbent coating, the PIL bucky gel sorbent coatings demonstrated higher extraction efficiency for the extraction of polycyclic aromatic hydrocarbons (PAHs). A partitioning extraction mechanism was observed for the PIL/MWCNT-based sorbent coatings indicating that the addition of MWCNTs did not seem to affect the extraction mechanism of the sorbent coating. The analyte-to-coating partition coefficients (log Kfs) were estimated and the limits of detection (LOD) for selected PIL bucky gel sorbent coating were determined to be in the range of 1–2.5 ng L−1. Recovery studies were also performed for PAHs in river and tap water to validate the applicability of the developed method.

Six ionic liquids (ILs) were applied for the first time as solvents in the extraction and preconcentration of deoxyribonucleic acid (DNA) using an in situ dispersive liquid–liquid microextraction (DLLME) approach. The effect of different IL substituents and functional group on the extraction efficiency of DNA was investigated. The highest extraction efficiencies of DNA were obtained using 1-(1,2-dihydroxypropyl)-3-hexadecylimidazolium bromide (C 16 POHIM-Br) and N , N -didecyl- N -methyl- d -glucaminium bromide [(C 10 ) 2 NMDG-Br]. Extraction efficiencies higher than 97% were obtained using small amounts of IL (0.50 mg) for each extraction. The extraction of DNA from a sample matrix containing metal ions and protein revealed that the metal ions did not interfere with the extraction of DNA and that the co-extraction of protein can be mitigated by performing the extraction under moderately acidic conditions. Data from 31 P NMR spectroscopy suggest that a combination of electrostatic and π–π interactions dominate IL–DNA complexation and that the extraction is concentration dependant.

A preconcentration procedure utilizing IL-based surfactants it is described for the first time. The procedure is based on transforming a water-soluble IL-based surfactant, 1-hexadecyl-3-butylimidazolium bromide (C₁₆C₄Im-Br), into a water-insoluble IL, 1-hexadecyl-3-butylimidazolium bis[(trifluoromethane)sulfonyl]imide (C₁₆C₄Im-NTf₂), via a simple metathesis reaction. The preconcentration procedure is used in combination with a micellar microwave-assisted extraction (MMAE) method for the analysis of sixteen polycyclic aromatic hydrocarbons (PAHs) from toasted cereals. The obtained microdroplet of C₁₆C₄Im-NTf₂ containing the extracted PAHs is then diluted with acetonitrile and injected into a high-performance liquid chromatograph (HPLC) employing UV-vis and fluorescence detection. This in situ preconcentration step highly improves the sensitivity of the MMAE despite the complexity of the solid matrix. The developed in situ preconcentration method exhibited almost quantitative extraction efficiencies (80-95% in average) for the PAHs studied, and good precision values (lower than 14%). The overall MMAE+in situ preconcentration method presented limits of detection down to 0.03 μg kg⁻¹.

Ionic liquids (ILs) are promising gas chromatography (GC) stationary phases due to their high thermal stability, negligible vapor pressure, and ability to solvate a broad range of analytes. The tunability of ILs allows for structure modification in pursuit of enhanced separation selectivity and control of analyte elution order. In this study, the solvation parameter model is used to characterize the solvation interactions of fifteen ILs containing various cationic functional groups (i.e., dimethylamino, hydroxyl, and ether) and cation types paired with various counter anions, namely, tris(pentafluoroethyl)trifluorophosphate (FAP − ), bis[(trifluoromethyl)sulfonyl]imide (NTf 2 − ), thiocyanate (SCN − ), tricyanomethide (C(CN) 3 − ), tetracyanoborate (B(CN) 4 − ), and bis[oxalate(2-)]borate (BOB − ). The presence of functional groups affected the hydrogen bond basicity, hydrogen bond acidity, as well as dispersion interactions of the resulting ILs, while the change of cation type yielded modest influence on the dipolarity. The switch of counter anions in unfunctionalized ILs produced compounds with higher dipolarity and hydrogen bond basicity. The dipolarity and hydrogen bond basicity of ILs possessing cyano-containing anions appeared to be inversely proportional to the cyano content of the anion. The modification of IL structure resulted in a significant effect on the retention behavior as well as separation selectivity for many solutes, including reversed elution orders of some analytes. This study provides one of the most comprehensive examinations up-to-date on the relation between IL structure and the resulting solvation characteristics and gives tremendous insight into choosing suitable ILs as GC stationary phases for solute specific separations.

The CO2 selectivity of two polymeric task-specific ionic liquid sorbent coatings, poly(1-vinyl-3-hexylimidazolium) bis[(trifluoromethyl)sulfonyl]imide [poly(VHIM-NTf2)] and poly(1-vinyl-3-hexylimidazolium) taurate [poly(VHIM-taurate)], was examined using solid-phase microextraction (SPME) for the determination of CO2 in simulated flue gas. For comparison purposes, a commercial SPME fiber, Carboxen™-PDMS, was also studied. A study into the effect of humidity revealed that the poly(VHIM-taurate) fiber exhibited enhanced resistance to water, presumably due to the unique mechanism of CO2 capture. The effect of temperature on the performance of the PIL-based and Carboxen fibers was examined by generating calibration curves under various temperatures. The sensitivity, linearity, and linear range of the three fibers were evaluated. The extraction of CH4 and N2 was performed and the selectivities of the PIL-based and Carboxen fibers were compared. The poly(VHIM-NTf2) fiber was found to possess superior CO2/CH4 and CO2/N2 selectivities compared to the Carboxen fiber, despite the smaller film thicknesses of the PIL-based fibers. A scanning electron microscopy study suggests that the amine group of the poly(VHIM-taurate) is capable of selectively reacting with CO2 but not CH4 or N2, resulting in a significant surface morphology change of the sorbent coating.

The complexation of native β-cyclodextrin (CD) and seven aromatic compounds, namely, phenetole, toluene, m-xylene, naphthalene, biphenyl, fluorene and phenanthrene, has been studied for first time utilizing a solid-phase microextraction (SPME)–high-performance liquid chromatography (HPLC) method. The stoichiometries of the analyte:β-CD complexes were found to be either 1:1 or 1:2. The formation of 1:2 complexes was confirmed for naphthalene, biphenyl, fluorene, and phenanthrene only when utilizing relatively high concentrations of β-CD (up to 6.6 mM). The 1:2 stoichiometries were confirmed using the classical modified Benesi–Hildebrand (BH) method. The calculated binding constants for 1:1 stoichiometries ( K 1 ) using the SPME method varied from 115.3 M −1 for toluene to 3510 M −1 for phenanthrene, whereas the corresponding values to the 1:2 stoichiometries ( K 3 ) varied from 7.30 × 10 5 M −2 for biphenyl to 9.03 × 10 6 M −2 for naphthalene.

The interest of using ionic liquids (ILs) as stationary phases in gas chromatography (GC) has increased in recent years. This is largely due to the fact that new classes of ILs are being developed that are capable of satisfying many of the requirements of GC stationary phases. This review highlights the major requirements of GC stationary phases and describes how molten salts/ILs can be designed to largely meet these needs. The retention characteristics of organic solutes will be discussed for ammonium, pyridinium, and phosphonium-based molten salts followed by imidazolium, pyridinium, pyrollidinium, and phosphonium-based IL stationary phases. The versatility of ILs allows for the development of stationary phases based on dicationic ILs, polymeric ILs, and IL mixtures. To aid in choosing the appropriate IL stationary phase for a particular separation, the reader is guided through the different types of stationary phases available to identify those capable of providing the desired separation selectivity of organic solutes while allowing for flexibility in ranges of temperature used throughout the separation.

Three ionic liquid (IL)-based aggregates, 1-hexadecyl-3-methylimidazolium bromide (HDMIm-Br), 1-hexadecyl-3-butylimidazolium bromide (HDBIm-Br), and 1,3-didodecylimidazolium bromide (DDDDIm-Br) have been applied to the development of a quantitative solid-phase microextraction (SPME)-gas chromatography (GC)–mass spectrometry (MS) method. A sensitivity factor (SF) is defined and introduced for the first time to quantitatively compare the efficiency of the IL-based aggregates by SPME-GC–MS and to evaluate the partitioning strength of several polycyclic aromatic hydrocarbons (PAHs) to the three IL-aggregates. The ILs HDBIm-Br and HDMIm-Br have been used successfully to extract seven PAHs from the certified reference sediment BCR-535 using focused microwave-assisted extraction followed by SPME-GC–MS. Average recoveries for six of the seven certified PAHs were 84.6% for HDMIm-Br and 101% for HDBIm-Br, with relative standard deviation values (RSDs) lower than 19%. The overall extraction method requires short extraction times (around 7 min for the microwave step) and avoids the use of organic solvents.

A new class of stationary phase coatings for solid-phase microextraction (SPME) based on polymeric ionic liquids (PILs) is presented. PIL-based SPME coatings exhibit exceptional film stability, high thermal stability, reproducible extraction efficiencies, and long lifetimes. A series of three homologous polymeric imidazolium-based ionic liquid coatings were synthesized by free radical reaction. The fiber coatings were used to extract esters and fatty acid methyl esters from aqueous solution followed by gas chromatographic separation and flame ionization detection. To examine the effect of the matrix on the coatings, extractions were carried out in a synthetic wine solution followed by recovery experiments in two real wine samples. When carrying out the extractions in aqueous solution, the detection limits for most analytes ranged from 2.5 to 50microgL(-1) whereas lower detection limits were obtained for larger fatty acid methyl esters. Recovery experiments carried out in red and white wines ranged from 70.2% to 115.1% using the PIL fibers compared to 61.9% to 102.9% using a commercial polydimethylsiloxane fiber of similar film thickness. The structural tuning capability of these new coating materials makes them widely amendable to performing task-specific microextractions.

A method to extract PAHs from sediments is carried out using aqueous solutions containing aggregates of the ionic liquid (IL) 1-hexadecyl-3-methylimidazolium bromide (HDMIm-Br) as the extracting medium. Focused microwave-assisted extraction has been used to accelerate the extraction step, followed by HPLC with fluorescence detection without clean-up steps to remove the IL prior to injection. The method has been applied to certified reference sediment BCR-535 and marine sediments from Tenerife (Canary Islands) with successful results. The optimized method gave average absolute recoveries of 91.1% for six of the seven PAHs studied, with relative standard deviations lower than 10.4%. The overall method is characterized for presenting low extraction times (6min), low amounts of the sediment (0.1g), low amounts of IL (45mM), and low volumes of aqueous extractant solution (9mL). The use of small amounts of both IL and aqueous extractant solution allows the method to be considered environmental-friendly.

The separation of 17 chiral sulfoxides and eight chiral sulfinate esters by gas chromatography (GC) on four derivatized cyclodextrin chiral stationary phases (CSPs) (Chiraldex G-TA, G-BP, G-PN, B-DM) is presented. Many of these compounds are structural isomers or part of a homologous series. Differences in enantioselectivity of the methyl phenyl sulfoxide isomers on the derivatized gamma cyclodextrin and the heptakis 2,6-di-O-methyl-beta-cyclodextrin (i.e. B-DM) CSPs are discussed. Under the conditions of this study, the molecular mass cut-off for the GC separation of these compounds was approximately 230. Compounds of higher molecular mass were not eluted from the CSPs at reasonable times and temperatures, but these higher molecular mass enantiomers can be separated by liquid chromatography and capillary electrophoresis. The enantiomeric separation and elution order of a sulfinate ester containing two stereogenic centers as well as 15 chiral sulfoxides is presented. The G-TA and B-DM CSPs generally gave opposite elution orders for most of the compounds studied.