Analytical and Bioanalytical Chemistry (v.410, #19)
Ionic liquids as tunable materials in (bio)analytical chemistry by Jared L. Anderson; Kevin D. Clark (4565-4566).
is Professor of Chemistry in the Department of Chemistry at Iowa State University. His research focuses on the development of stationary phases for multidimensional gas chromatography, alternative approaches in sample preparation, particularly in nucleic acid isolation and purification, and developing analytical tools for trace level analysis within active pharmaceutical ingredients. He has published over 150 peer-reviewed publications and 5 book chapters. He currently holds 6 patents and serves on the editorial boards of Analytica Chimica Acta, Analytical and Bioanalytical Chemistry, Journal of Liquid Chromatography and Related Technologies, LCGC Magazine, and Journal of Separation Science. completed his BA degree in chemistry at Gustavus Adolphus College (Minnesota) in 2012. He is a PhD candidate in analytical chemistry at Iowa State University under the supervision of Professor Jared Anderson. His research focuses on selective nucleic acid analysis and the application of magnetic ionic liquids in bioanalytical chemistry.
Advances in the analysis of biological samples using ionic liquids by Kevin D. Clark; María J. Trujillo-Rodríguez; Jared L. Anderson (4567-4573).
Ionic liquids are a class of solvents and materials that hold great promise in bioanalytical chemistry. Task-specific ionic liquids have recently been designed for the selective extraction, separation, and detection of proteins, peptides, nucleic acids, and other physiologically relevant analytes from complex biological samples. To facilitate rapid bioanalysis, ionic liquids have been integrated in miniaturized and automated procedures. Bioanalytical separations have also benefited from the modification of nonspecific magnetic materials with ionic liquids or the implementation of ionic liquids with inherent magnetic properties. Furthermore, the direct detection of the extracted molecules in the analytical instrument has been demonstrated with structurally tuned ionic liquids and magnetic ionic liquids, providing a significant advantage in the analysis of low-abundance analytes. This article gives an overview of these advances that involve the application of ionic liquids and derivatives in bioanalysis. Graphical abstractIonic liquids, magnetic ionic liquids, and ionic liquid-based sorbents are increasing the speed, selectivity, and sensitivity in the analysis of biological samples
Keywords: Task-specific ionic liquid; Magnetic ionic liquid; Bioanalysis; Automation; Miniaturization; Magnetic separation
Capacitive hysteresis at the 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)-trifluorophosphate–polycrystalline gold interface by Anthony J. Lucio; Scott K. Shaw (4575-4586).
is a PhD graduate from the University of Iowa in the laboratory of Prof. Scott K. Shaw where he studied the electrochemical double-layer capacitance in ionic liquids. He will be doing postdoctoral research at the University of Warwick on synthetic diamond-based electrochemical sensors. is an Assistant Professor of Chemistry at the University of Iowa. His research interests include physical and analytical characterization of chemical surfaces and interfaces, including measuring the dynamics and dimensions of interfacial molecular assemblies. This work is motivated by important challenges in environmental chemistry, and energy storage and production. We report potential-dependent capacitance curves over a 2-V potential range for the 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)-trifluorophosphate (Emim FAP)–polycrystalline gold interface, and examine the effect of potential scan direction on results. We find very small levels of capacitive hysteresis in the Emim FAP–polycrystalline Au electrochemical system, where capacitance curves show minor dependence on the potential scan direction employed. This is a considerably different response than that reported for the Emim FAP–Au(111) interface where significant hysteresis is observed based on the potential scan direction (Drüschler et al. in J Phys Chem C 115 (14):6802–6808, 2011). Hysteresis effects have previously been suggested to be a general feature of an ionic liquid (IL) at electrified interfaces due to slow interfacial processes and has been demonstrated for numerous electrochemical systems. We provide new evidence that the experimental procedure used to acquire capacitance data and data workup could also have implications on capacitance–potential relationships in ILs. This work serves to progress our understanding of the nature of capacitive hysteresis at the IL–electrode interface. Graphical abstractSubtle changes in experimental methods can lead to significantly different capacitance measurements in ionic liquids. Which is the best approach?
Keywords: Capacitance; Electrochemical impedance spectroscopy; Electrochemical double layer; Hysteresis; Ionic liquid
Toward continuous amperometric gas sensing in ionic liquids: rationalization of signal drift nature and calibration methods by Lu Lin; Xiangqun Zeng (4587-4596).
is currently a PhD student in the electro-analytical chemistry lab of Professor Xiangqun Zeng at Oakland University, Rochester, Michigan. His research interest is in the area of continuous-use ionic liquid electrochemical sensors for multiple gas detection, involving methods development, sensor characterization, and validation. He is currently an invited reviewer of ISCAS (IEEE International Symposium on Circuits and Systems), and was awarded the URC Student Travel Grant by the Office of Research Administration of Oakland University in 2014 and the First Time Graduate Student Scholarship by Oakland University in 2012. is currently a Professor at the Department of Chemistry at Oakland University, Rochester, Michigan. She has been working in the areas of electrochemistry and interface chemistry at solid electrodes, development of new analytical techniques, chemical and biosensors, ionic liquids, and conductive polymers for over 20 years. She is an Editorial Board member of Journal of Electrochemistry and a reviewer for a broad range of US federal funding agencies. Sensor signal drift is the key issue for the reliability of continuous gas sensors. In this paper, we characterized the sensing signal drift of an amperometric ionic liquid (IL)-based oxygen sensor to identify the key chemical parameters that contribute to the signal drift. The signal drifts due to the sensing reactions of the analyte oxygen at the electrode/electrolyte interface at a fixed potential and the mass transport of the reactant and product at the electrode/electrolyte interface were systematically studied. Results show that the analyte concentration variation and the platinum electrode surface activity are major factors contributing to sensing signal drift. An amperometric method with a double potential step incorporating a conditioning step was tested and demonstrated to be useful in reducing the sensing signal drift and extending the sensor operation lifetime. Also, a mathematic method was tested to calibrate the baseline drift and sensing signal sensitivity change for continuous sensing. This study provides the understanding of the chemical processes that contribute to the IL electrochemical gas (IL-EG) sensor signal stability and demonstrates some effective strategies for signal drift calibration that can increase the reliability of the continuous amperometric sensing. Graphical Abstractᅟ
Keywords: Gas sensors; Ionic liquid; Continuous sensing; Signal drift; Calibration
Evaluating the solvation properties of metal-containing ionic liquids using the solvation parameter model by He Nan; Liese Peterson; Jared L. Anderson (4597-4606).
completed his M.S. degree in chemistry at Kyung Hee University in Korea. He is currently a Ph.D. student in the Department of Chemistry at Iowa State University working under the supervision of Professor Jared Anderson. His research focuses on developing new sample preparation methods, new stationary phases in chromatographic separations, and using comprehensive two-dimensional gas chromatography in the resolution of complex samples. is an undergraduate student in Chemistry at Concordia College, Moorhead, Minnesota, and will complete her B.A. in Chemistry in 2018. She completed a research internship in summer 2017 at Iowa State University under the direction of Professor Jared Anderson. is a Professor of Chemistry in the Department of Chemistry at Iowa State University. His research focuses on the development of stationary phases for multidimensional gas chromatography, alternative approaches in sample preparation, particularly in nucleic acid isolation and purification, and developing analytical tools for trace level analysis within active pharmaceutical ingredients. Ionic liquids (IL) have been utilized as gas chromatography stationary phases due to their high thermal stability, negligible vapor pressure, wide liquid range, and the ability to solvate a range of analytes. In this study, the solvation properties of eight room temperature ILs containing various transition and rare earth metal centers [e.g., Mn(II), Co(II), Ni(II), Nd(III), Gd(III), and Dy(III)] are characterized using the Abraham solvation parameter model. These metal-containing ILs (MCILs) consist of the trihexyl(tetradecyl)phosphonium cation and functionalized acetylacetonate ligands chelated to various metals. They are used in this study as gas chromatographic stationary phases to investigate the effect of the metal centers on the separation selectivities for various analytes. In addition, two MCILs comprised of tetrachloromanganate and tris(trifluoromethylphenylacetylaceto)manganate anions were used to study the effect of chelating ligands on the selectivity of the stationary phases. Depending on the metal center and chelating ligand, significant differences in solvation properties were observed. MCILs containing Ni(II) and Mn(II) metal centers exhibited higher retention factors and higher peak asymmetry factors for amines (e.g., aniline and pyridine). Alcohols (e.g., phenol, p-cresol, 1-octanol, and 1-decanol) were strongly retained on the MCIL stationary phase containing Mn(II) and Dy(III) metal centers. This study presents a comprehensive evaluation into how the solvation properties of ILs can be varied by incorporating transition and rare earth metal centers into their structural make-up. In addition, it provides insight into how these new classes of ILs can be used for solute-specific gas chromatographic separations. Graphical abstractThe solvation properties of eight metal-containing ionic liquids (MCILs) comprised of transition and rare-earth metal centers are evaluated for the first time using gas chromatography. The results reveal that metals comprising the MCILs provide unique separation selectivities for various analytes and that these materials can be exploited as stationary phases in solute-specific gas chromatographic separations.
Keywords: Ionic liquids; Gas chromatography; Magnetic ionic liquids; Solvation properties
Ionic liquid inspired alkalinochromic salts based on Reichardt’s dyes for the solution phase and vapochromic detection of amines by Jeremy B. Essner; Gary A. Baker (4607-4613).
Chromogenic salts based on the negatively solvatochromic pyridinium N-phenolate betaines 2,6-diphenyl-4-(2,4,6-triphenyl-N-pyridino)-phenolate (Reichardt’s dye 30) and 2,6-dichloro-4-(2,4,6-triphenyl-N-pyridino)-phenolate (Reichardt’s dye 33) proved to be promising probes for the colorimetric detection of bases, including hydroxide ion, ammonia, and aliphatic amines. Specifically, the protonated halide forms of these two dyes were ion exchanged to generate lipophilic bis(trifluoromethylsulfonyl)imide derivatives, denoted [E T(30)][Tf2N] and [E T(33)][Tf2N], respectively. When dissolved in 95 vol% EtOH, these essentially colorless solutions displayed dramatic “alkalinochromic” color-on switching due to phenolic deprotonation to generate the zwitterionic form of the dyes with their characteristic charge-transfer absorption. The extent of the colorimetric response varied with the base strength for the aliphatic amines tested (i.e., propylamine, ethanolamine, ethylenediamine, diethylenetriamine, triethylamine, triethanolamine), being loosely correlated with the pK b of the amine. In addition, we demonstrated proof of concept for the vapochromic detection of ammonia and aliphatic amines by dissolution of the chromogenic probes in the ionic liquid 1-propyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide. We also showed that the dyed ionic liquid can be successfully immobilized within silica sol-gel ionogels to generate more practical and robust sensory platforms. This strategy represents a useful addition to existing colorimetric sensor arrays targeting amines and other basic species. In particular, the differential response of the two different probes offers a measure of chemical selectivity which will be of interest for detecting biogenic amines in food safety applications, among other areas.
Keywords: Reichardt’s dye 30; Reichardt’s dye 33; Vapochromic detection; Amine detection; Ionic liquids
Ionic liquid capillary columns for analysis of multi-component volatiles by gas chromatography-mass spectrometry: performance, selectivity, activity and retention indices by Michelle S. S. Amaral; Philip J. Marriott; Humberto R. Bizzo; Claudia M. Rezende (4615-4632).
This study investigates applications and performance evaluation of SLB-IL60, SLB-IL76 and SLB-IL111 columns, in relation to a DB-Wax column, for the analysis of coffee volatile compounds. Both standards and an authentic coffee sample were analysed, with solid-phase microextraction (SPME) sampling of the latter. A cryofocusing method was applied to improve resolution of the earliest eluting peaks using splitless injection SPME sample analysis. The Grob test was used to verify the inertness and efficiency of the columns, helping to understand the interactions between analytes and stationary phases, particularly toward more polar coffee analytes. A DB-5 column was used only in analysis of n-alkanes and Grob test mixtures as an apolar reference. The evaluated ionic liquid columns showed a moderate acid-base character and low inertness for compounds with hydrogen bond capabilities, especially for the hydroxylated analytes, 2,3-butanediol in the Grob test, and furanones and acids in the coffee standards. The columns exhibiting the best resolution and efficiency were DB-Wax and SLB-IL60, both for samples and standards. Although the DB-Wax column is preferred for analysis of coffee volatiles, due to better inertness, the evaluated ionic liquid columns allowed identification of compounds that were not observed in separations with the Wax-phase column in this work. Among these compounds is 3,4-dimethyl-2,5-furandione, seldom reported in the literature of coffee. Proposed improvement by the manufacturer in the inertness of the columns evaluated in this study may lead to better results; so future versions of IL phases may be better applied in the separation of target analytes, especially those with basic character. Graphical abstractIllustrative representation of the sample (coffee) and the chemical structures of the stationary phases of the ionic liquid capillary columns used as object of study in the present work.
Keywords: Ionic liquids; Coffee volatiles; Gas chromatography; Solid-phase microextraction; Cryofocusing
Branched-chain dicationic ionic liquids for fatty acid methyl ester assessment by gas chromatography by Mohsen Talebi; Rahul A. Patil; Leonard M. Sidisky; Alain Berthod; Daniel W. Armstrong (4633-4643).
The authors would like to call the reader’s attention to the fact that the original publication included some corrections needed to be addressed.Twelve bis- or dicationic ionic liquids (ILs) including eight based on imidazolium, a single one based on phosphonium, and three based on pyrrolidinium cationic units were prepared with the bis(trifluoromethyl sulfonyl) imide anion. The two identical cationic moieties were attached by different alkyl spacers having three or five carbons and differing alkyl substituents attached to the spacer. The SLB-IL111 column, as the most polar commercial stationary phase known, was included in the study for comparison. Isothermal separations of a rapeseed oil fatty acid methyl ester (FAME) sample were used to study and compare the 12 IL-based column performances and selectivities. The retention times of the most retained methyl esters of lignoceric (C24:0) and erucic (C22:1) acids were used to estimate the IL polarity. The phosphonium dicationic IL column was, by far, the least polar. Imidazolium-based dicationic IL columns were the most polar. Polarity and selectivity for the FAME separation were somewhat related. The separation of a 37-FAME standard mixture allowed the investigation of selectivity variations observed on the 12 IL-based columns under temperature gradients up to 230 °C. The remarkable selectivity of the IL-based columns is demonstrated by the detailed analysis of the cis/trans C18:1 isomers of a partially hydrogenated vegetable oil sample on 30-m columns, separations competing with that done following an “official method” performed on a 100-m column. Graphical abstractSeparation of fatty acid methyl esters on a 30-m 3m2C5(mpy)2. 2NTf2 branched-chain dicationic IL-based column. Branched chain dicationic ILs show great selectivity for separation of cis/trans, ω-3/ω-6, and detailed analysis of cis/trans fats.
Keywords: Gas chromatography; Ionic liquid columns; Fatty acid methyl esters; Selectivity; Polarity
Dicationic ionic liquid thermal decomposition pathways by Rahul A. Patil; Mohsen Talebi; Alain Berthod; Daniel W. Armstrong (4645-4655).
The rapid expansion in the study and use of ionic liquids (ILs) is a result of their unique properties including negligible volatility, high thermal stability, and ability to dissolve disparate compounds. However, because ILs have infinitely variable structures (often referred to as “tunability”), these properties can differ considerably. Herein, we focus on the thermal stability of 15 bis-/dicationic ionic liquids. Specifically, their thermal breakdown products are examined to determine the structural linkages, bonds, or atoms most susceptible to thermally induced changes and whether such changes occur before possible volatilization. In most cases, the heteroatom-carbon single bonds were susceptible to thermolytic decomposition. Graphical abstractCapture of dicationic ionic liquid thermal decomposition products for subsequent identification.
Keywords: Ionic liquid; High temperature; Decomposition mechanism; Thermal decomposition; Thermal stability
Ionic liquids as water-compatible GC stationary phases for the analysis of fragrances and essential oils by Cecilia Cagliero; Carlo Bicchi; Chiara Cordero; Erica Liberto; Patrizia Rubiolo; Barbara Sgorbini (4657-4668).
Fragrances and products deriving from essential oils are often formulated or diluted in aqueous media, usually ethanol/water. Gas chromatography (GC) is the technique of choice to analyze volatiles. However, when using columns coated with conventional stationary phases, its application to aqueous samples often requires time-consuming and/or discriminative sample preparation techniques to extract the target analytes from the aqueous medium, so as to avoid its direct injection. In GC with conventional columns, water produces peak asymmetry, poor sensitivity and efficiency, strong adsorption, stationary phase degradation, and, last but not least, it is not easy to detect reliably when present in high amounts. In 2012, Armstrong’s group introduced new fully water-compatible ionic-liquid (IL)-based GC capillary columns based on phosphonium and imidazolium derivative cations combined with trifluoromethanesulphonate. These columns were recently made available commercially by Supelco, under the trade name Watercol™. These derivatives maintain IL’s unique selectivity and chromatographic properties, and enable water to be used as injection solvent, thus avoiding the sample preparation procedures required by conventional columns. This study reports and critically discusses the results of commercially available water-compatible IL columns for direct analysis of aqueous samples in the fragrance and essential oil fields by GC with thermal conductivity (TCD) and/or flame ionization detectors (FID). The results showed that water-compatible IL-based stationary phases can successfully be adopted for qualitative and quantitative analysis of fragrances and essential oils directly diluted in aqueous solvents. On the other hand, the study also shows that their inertness needs to be further increased and (possibly) the range of operative temperature extended when water is the main solvent of the sample.
Keywords: Ionic liquids; GC; Aqueous samples; Water-compatible stationary phases; Essential oils; Fragrances
Ionic liquid phases with comprehensive two-dimensional gas chromatography of fatty acid methyl esters by Siriluck Pojjanapornpun; Yada Nolvachai; Kornkanok Aryusuk; Chadin Kulsing; Kanit Krisnangkura; Philip J. Marriott (4669-4677).
New generation inert ionic liquid (iIL) GC columns IL60i, IL76i and IL111i, comprising phosphonium or imidazolium cationic species, were investigated for separation of fatty acid methyl esters (FAME). In general, the iIL phases provide comparable retention times to their corresponding conventional columns, with only minor selectivity differences. The average tailing factors and peak widths were noticeably improved (reduced) for IL60i and IL76i, while they were slightly improved for IL111i. Inert IL phase columns were coupled with conventional IL columns in comprehensive two-dimensional GC (GC × GC) with a solid-state modulator which offers variable modulation temperature (T M), programmable T M during analysis and trapping stationary phase material during the trap/release (modulation) process, independent of oven T and column sets. Although IL phases are classified as polar, relative polarity of the two phases comprising individual GC × GC column sets permits combination of less-polar IL/polar IL and polar IL/less-polar IL column sets; it was observed that a polar/less-polar column set provided better separation of FAME. A higher first dimension (1D) phase polarity combined with a lower 2D phase polarity, for instance 1D IL111i with 2D IL59 gave the best result; the greater difference in 1D/2D phase polarity results in increasing occupancy of peak area in the 2D space. The IL111i/IL59 column set was selected for analysis of fatty acids in fat and oil products (butter, margarine, fish oil and canola oil). Compared with the conventional IL111, IL111i showed reduced column bleed which makes this more suited to GC × GC analysis of FAME. The proposed method offers a fast profiling approach with good repeatability of analysis of FAME.
Keywords: Comprehensive two-dimensional gas chromatography; Fatty acid methyl ester; Inert IL phases; Ionic liquids; Solid-state modulation
Hydrophilic magnetic ionic liquid for magnetic headspace single-drop microextraction of chlorobenzenes prior to thermal desorption-gas chromatography-mass spectrometry by Elena Fernández; Lorena Vidal; Antonio Canals (4679-4687).
A new, fast, easy to handle, and environmentally friendly magnetic headspace single-drop microextraction (Mag-HS-SDME) based on a magnetic ionic liquid (MIL) as an extractant solvent is presented. A small drop of the MIL 1-ethyl-3-methylimidazolium tetraisothiocyanatocobaltate(II) ([Emim]2[Co(NCS)4]) is located on one end of a small neodymium magnet to extract nine chlorobenzenes (1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene, 1,2,3,4-tetrachlorobenzene, 1,2,4,5-tetrachlorobenzene, and pentachlorobenzene) as model analytes from water samples prior to thermal desorption-gas chromatography-mass spectrometry determination. A multivariate optimization strategy was employed to optimize experimental parameters affecting Mag-HS-SDME. The method was evaluated under optimized extraction conditions (i.e., sample volume, 20 mL; MIL volume, 1 μL; extraction time, 10 min; stirring speed, 1500 rpm; and ionic strength, 15% NaCl (w/v)), obtaining a linear response from 0.05 to 5 μg L−1 for all analytes. The repeatability of the proposed method was evaluated at 0.7 and 3 μg L−1 spiking levels and coefficients of variation ranged between 3 and 18% (n = 3). Limits of detection were in the order of nanograms per liter ranging from 4 ng L−1 for 1,4-dichlorobenzene and 1,2,3,4-tetrachlorobenzene to 8 ng L−1 for 1,2,4,5-tetrachlorobenzene. Finally, tap water, pond water, and wastewater were selected as real water samples to assess the applicability of the method. Relative recoveries varied between 82 and 114% showing negligible matrix effects. Graphical abstractMagnetic headspace single-drop microextraction followed by thermal desorption-gas chromatography-mass spectrometry
Keywords: Magnetic ionic liquid; Magnetic headspace single-drop microextraction; Thermal desorption-gas chromatography-mass spectrometry; Chlorobenzenes; Water samples
Magnetic ionic liquids as versatile extraction phases for the rapid determination of estrogens in human urine by dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography-diode array detection by Josias Merib; Daniel A. Spudeit; Gabriela Corazza; Eduardo Carasek; Jared L. Anderson (4689-4699).
In this study, a rapid and straightforward approach based on magnetic ionic liquids (MIL) as extraction phases and dispersive liquid-liquid microextraction (DLLME) was developed to analyze the hormones estriol, 17-β-estradiol, 17-α-ethynylestradiol, and estrone in human urine samples. This is the first report of an application of manganese-based MILs compatible with HPLC to extract compounds of biological interest from urine samples. The hydrophobic MILs trihexyltetradecylphosphonium tetrachloromanganate (II) ([P6,6,6,14 +]2[MnCl4 2−]) and aliquat tetrachloromanganate (II) ([Aliquat+]2[MnCl4 2−]) were employed and the optimized extraction conditions were comprised of 5 mg of MIL ([P6,6,6,14 +]2[MnCl4 2−]), 5 μL of methanol (MeOH) as disperser solvent, and an extraction time of 90 s at sample pH 6. The analytical parameters of merit were determined under optimized conditions and very satisfactory results were achieved, with LODs of 2 ng mL−1 for all analytes, determination coefficients (R 2) ranging from 0.9949 for 17-β-estradiol to 0.9998 for estrone. In addition, good results of method precision were achieved with the intraday (n = 3) varying from 4.7% for 17-β-estradiol to 19.5% for estriol (both at 5 ng mL−1) and interday precision (evaluated at 100 ng mL−1) ranging from 11.4% for estrone to 17.7% for 17-α-ethynylestradiol and analyte relative recovery evaluated in three real samples ranged from 67.5 to 115.6%. The proposed DLLME/MIL-based approach allowed for a reliable, environmentally friendly and high-throughput methodology with no need for a centrifugation step. Graphical abstractAn overview of the rapid and straightforward extraction procedure using DLLME/MIL-based approach
Keywords: Magnetic ionic liquids; Sample preparation; Urine; Biological samples
Salt-induced ionic liquid-based microextraction using a low cytotoxic guanidinium ionic liquid and liquid chromatography with fluorescence detection to determine monohydroxylated polycyclic aromatic hydrocarbons in urine by Idaira Pacheco-Fernández; Verónica Pino; Jacob Lorenzo-Morales; Juan H. Ayala; Ana M. Afonso (4701-4713).
A novel ionic liquid (IL)-based microextraction method has been developed for the determination of four hydroxylated polycyclic aromatic hydrocarbons (OHPAHs) in urine samples. The water soluble IL-based surfactant selected as extraction solvent is decylguanidinium chloride (C10Gu-Cl), the cytotoxicity and micellar behavior of which were evaluated. The proposed salt-induced IL-based preconcentration method simply consists in adding NaClO4 to the aqueous medium containing the IL to promote its water insolubility. The entire method was optimized, requiring the use of only 20 μL of C10Gu-Cl for 10 mL of diluted urine sample (1:10) without any pH adjustment, followed by the addition of NaClO4 to ensure a 5% (w/v) content. A cloudy solution was observed immediately, and after the application of 4 min of vortex and 8 min of centrifugation, the droplet was diluted up to 60 μL with a mixture of acetonitrile:water (30:70) and injected into the liquid chromatograph with fluorescence detection. The method was validated using both synthetic urine and human urine as matrix for the determination of the four OHPAHs. The following analytical features were obtained: detection limits down to 1 ng·L-1 in real urine; inter-day reproducibility (as RSD in %) always lower than 17% when dealing with real urine samples spiked at 80 ng·L-1; and average relative recoveries of 102% in real urine samples at such low spiked levels. Despite the simplicity of the proposed method, it performed successfully with complex urine samples. Graphical abstractSalt-induced IL-based microextraction using a low cytotoxic IL for mono-OHPAHs in urine
Keywords: Guanidinium-based ionic liquids; Monohydroxylated polycyclic aromatic hydrocarbons; Urine; Liquid-phase microextraction; High-performance liquid chromatography; Fluorescence detection
Magnetic ionic liquid-based dispersive liquid-liquid microextraction technique for preconcentration and ultra-trace determination of Cd in honey by Emiliano F. Fiorentini; Leticia B. Escudero; Rodolfo G. Wuilloud (4715-4723).
A simple, highly efficient, batch, and centrifuge-less dispersive liquid-liquid microextraction method based on a magnetic ionic liquid (MIL-DLLME) and electrothermal atomic absorption spectrometry (ETAAS) detection was developed for ultra-trace Cd determination in honey. Initially, Cd(II) was chelated with ammonium diethyldithiophosphate (DDTP) at pH 0.5 followed by its extraction with the MIL trihexyl(tetradecyl)phosphonium tetrachloroferrate(III) ([P6,6,6,14]FeCl4) and acetonitrile as dispersant. The MIL phase containing the analyte was separated from the aqueous phase using only a magnet. A back-extraction procedure was applied to recover Cd from the MIL phase using diluted HNO3 and this solution was directly injected into the graphite furnace of ETAAS instrument. An extraction efficiency of 93% and a sensitivity enhancement factor of 112 were obtained under optimal experimental conditions. The detection limit (LOD) was 0.4 ng L−1 Cd, while the relative standard deviation (RSD) was 3.8% (at 2 μg L−1 Cd and n = 10), calculated from the peak height of absorbance signals. This work reports the first application of the MIL [P6,6,6,14]FeCl4 along with the DLLME technique for the successful determination of Cd at trace levels in different honey samples. Graphical abstractPreconcentration of ultratraces of Cd in honey using a magnetic ionic liquid and dispersive liquid-liquid microextraction technique.
Keywords: Magnetic ionic liquids; Microextraction; Preconcentration; Cadmium; Honey
Sensitive analysis of N-blocked amino acids using high-performance liquid chromatography with paired ion electrospray ionization mass spectrometry by Yadi Wang; Siqi Du; Daniel W. Armstrong (4725-4735).
In this study, a paired ion electrospray ionization (PIESI) mass spectrometry method was developed for sensitive detection of 9-fluorenylmethyl chloroformate (Fmoc)-derivatized amino acids. The structure-optimized ion-pairing reagent was introduced post column to form positively charged complexes which can be detected in the positive ion mode. These complexes are more surface-active than the original analytes, and meanwhile, the intensity of sodium adducts was significantly reduced. The limit of detection of the amino acids obtained with the optimal ion-pairing reagent was 0.5 to 20 pg which was 5–100 times lower than the negative mode. In addition, two mass spectrometry platforms—linear ion trap and triple quadrupole—were used to compare the PIESI improvements. Eventually, the method was applied to successfully detect the level of amino acids in human urine samples with high accuracy and the added benefit of minimizing matrix effects. Graphical abstractA HPLC-ESI-MS/MS method by using ion-pairing reagents for sensitive detection of Fmoc amino acids
Keywords: Paired ion electrospray ionization; PIESI; HPLC-MS; Amino acids; Ionic liquid
Miniaturized dispersive liquid-liquid microextraction and MALDI MS using ionic liquid matrices for the detection of bacterial communication molecules and virulence factors by Jan Leipert; Ingrid Bobis; Sabine Schubert; Helmut Fickenscher; Matthias Leippe; Andreas Tholey (4737-4748).
The identification and quantification of molecules involved in bacterial communication are major prerequisites for the understanding of interspecies interactions at the molecular level. We developed a procedure allowing the determination of 2-heptyl-4(1H)-quinolone (HHQ) and 2-heptyl-3-hydroxy-4(1H)-quinolone (PQS) and the virulence factor pyocyanin (PYO) formed by the Gram-negative bacterium Pseudomonas aeruginosa. The method is based on dispersive liquid-liquid microextraction from small supernatant volumes (below 10 μL) followed by quantitative matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). The use of ionic liquid matrix led to a lowered limit of detection for pyocyanin and, due to suppression of matrix background signals, easy to interpret mass spectra compared to crystalline matrices. Using an isotope-labeled pyocyanin standard synthesized in small-scale synthesis, quantitative analysis spanning approximately one order of magnitude (0.5 to 250 fmol) was feasible. The method was successfully applied to the detection of the signaling molecules PQS and HHQ in cultures of P. aeruginosa strains isolated from sputum of cystic fibrosis patients and allowed a highly sensitive quantification of PYO from these cultures. Hence, the developed method bears the potential to be used for screening purposes in clinical settings and will help to decipher the molecular basis of bacterial communication. Graphical abstractIonic liquid matrices for the detection and quantification of the toxin pyocyanin and other signaling molecules from P. aeruginosa by MALDI MS.
Keywords: Biofilm; Cystic fibrosis; Pseudomonas aeruginosa ; Pyocyanin; Quorum sensing; Resistance
Characterization of the aroma profile of novel Brazilian wines by solid-phase microextraction using polymeric ionic liquid sorbent coatings by Juliana Crucello; Luiz F. O. Miron; Victor H. C. Ferreira; He Nan; Marcia O. M. Marques; Patricia S. Ritschel; Mauro C. Zanus; Jared L. Anderson; Ronei J. Poppi; Leandro W. Hantao (4749-4762).
In this study, a series of polymeric ionic liquid (PIL) sorbent coatings is evaluated for the extraction of polar volatile organic compounds (VOCs) from Brazilian wines using headspace solid-phase microextraction (HS-SPME), including samples from ‘Isabella’ and ‘BRS Magna’ cultivars—the latter was recently introduced by the Brazilian Agricultural Research Corporation – National Grape & Wine Research Center. The structurally tuned SPME coatings were compared to the commercial SPME phases, namely poly(acrylate) (PA) and divinylbenzene/carboxen/poly(dimethylsiloxane) (DVB/CAR/PDMS). The separation, detection and identification of the aroma profiles were obtained using comprehensive two-dimensional gas chromatography mass spectrometry (GC×GC-MS). The best performing PIL-based SPME fiber, namely 1-hexadecyl-3-vinylimidazolium bis[(trifluoromethyl)sulfonyl]imide with 1,12-di(3-vinylimidazolium)dodecane dibis[(trifluoromethyl)sulfonyl]imide incorporated cross-linker supported on an elastic nitinol wire, exhibited superior performance to DVB/CAR/PDMS regarding the average number of extracted peaks and extracted more polar analytes providing additional insight into the aroma profile of ‘BRS Magna’ wines. Four batches of wine were evaluated, namely ‘Isabella’ and ‘BRS Magna’ vintages 2015 and 2016, using highly selective PIL-based SPME coatings and enabled the detection of 350+ peaks. Furthermore, this is the first report evaluating the aroma of ‘BRS Magna’ wines. A hybrid approach that combined pixel-based Fisher ratio and peak table-based data comparison was used for data handling. This proof-of-concept experiment provided reliable and statistically valid distinction of wines that may guide regulation agencies to create high sample throughput protocols to screen wines exported by Brazilian vintners. Graphical abstractHighly selective extraction of wine aroma using polymeric ionic liquid.
Keywords: Biomarkers; Flavor and aroma; Food chemistry; Foodomics; Sensomics
Correction to: Branched-chain dicationic ionic liquids for fatty acid methyl ester assessment by gas chromatography by Mohsen Talebi; Rahul A. Patil; Leonard M. Sidisky; Alain Berthod; Daniel W. Armstrong (4763-4764).
The authors would like to call the reader’s attention to the fact that the original publication included some corrections needed to be addressed.