Determination of water pollutants by direct-immersion solid-phase microextraction using polymeric ionic liquid coatings

The determination of a group of eighteen pollutants in waters, including polycyclic aromatic hydrocarbons and substituted phenols, is conducted in direct-immersion solid-phase microextraction (SPME) using the polymeric ionic liquid (PIL) poly(1-vinyl-3-hexadecylimidazolium) bis[(trifluoromethyl)sulfonyl]imide as a novel coating material. The performance of the PIL fiber coating in the developed IL-SPME-gas chromatography (GC)–mass spectrometry (MS) method is characterized by average relative recoveries of 92.5% for deionized waters and 90.8% for well waters, average precision values (as relative standard deviations, RSD%) of 11% for deionized waters and 12% for well waters, using a spiked level of 5 ng mL⁻¹. The detection limits oscillate from 0.005 ng mL⁻¹ for fluoranthene to 4.4 ng mL⁻¹ for 4-chloro-3-methylphenol, when using an extraction time of 60 min with 20 mL of aqueous sample. The extraction capabilities of the PIL fiber have been compared with the commercial SPME coatings: polydimethylsyloxane (PDMS) 30 μm, PDMS 100 μm and polyacrylate (PA) 85 μm. The PIL fiber is superior to the PDMS 30 μm for all analytes studied. A qualitative study was also carried out to compare among the nature of the coating materials by normalizing the coating thickness. The PIL material was shown to be more efficient than the PDMS material for all analytes studied. The PIL coating was also adequate for nonpolar analytes whereas the PA material was more sensitive for polar compounds.     

Ionic liquid-based single-drop liquid-phase microextraction combined with high-performance liquid chromatography for the determination of sulfonamides in environmental water

A simple, rapid and environment‐friendly technique of single‐drop liquid‐phase microextraction has been developed for the determination of sulfonamides in environmental water. Several important parameters including stirring rate, extraction solvent, extraction pH, salinity and extraction time were optimized to maximize the extract efficiency. Extraction solvent 1‐octyl‐3‐methylimidazolium hexafluorophosphate [C₈MIM][PF₆] ionic liquid showed better extraction efficiency than 1‐butyl‐3‐methylimidazolium hexafluorophosphate [C₄MIM][PF₆] and 1‐octanol. The optimum experimental conditions were: pH, 4.5; sodium chloride content, 36% w/v; extraction time, 20 min. This method provided low detection limits (0.5–1 ng/mL), good repeatability (the RSD ranging from 4.2 to 9.9%, n=5) and wide linear range (1–1500 ng/mL), with determination coefficients (r²) higher than 0.9989 for all the target compounds. Real sample analysis showed relative recoveries between 63.5 and 115.8% for all the target compounds.     

离子液体顶空液相微萃取富集苯系物

以水不互溶的离子液体1-丁基-3-甲基咪唑的六氟磷酸盐作为顶空液相微萃取的萃取剂,能够从水溶液中有效地萃取苯系物。当萃取时间为30min时,富集倍数在19～50之间。     

Conductive polymeric ionic liquids for electroanalysis and solid-phase microextraction

Three novel electropolymerizable thiophene-based ionic liquids (ILs) were synthesized and characterized as potential candidates for developing selective extraction media for chemical analysis. Electropolymerization of the bis[(trifluoromethyl)sulfonyl]imide ([NTf₂]^-) analogs successfully produced uniform polymeric thin-films on macro- and microelectrode substrates from both vinyl and methylimidazolium IL monomer derivatives. The resultant conducting polymer IL (CPIL) films were characterized by electrochemical methods and found to exhibit attractive behavior towards anionic species while simultaneously providing an exclusion barrier toward cationic species. Thermogravimetric analysis of the thiophene-based IL monomers established a high thermal stability, particularly for the methylimidazolium IL, which was stable until temperatures above 350 °C. Subsequently, the methylimidazolium IL was polymerized on 125 μm platinum wires and utilized for the first time as a sorbent coating for headspace solid-phase microextraction (HS-SPME). The sorbent coating was easily prepared in a reproducible manner, provided high thermal stability, and allowed for the gas chromatographic analysis of polar analytes. The normalized response of the poly[thioph-C₆MIm][NTf₂]-based sorbent coating exhibited higher extraction efficiency compared to an 85 μm polyacrylate fiber and excellent fiber-to-fiber reproducibility. Therefore, the electropolymerizable thiophene-based ILs were found to be viable new materials for the preparation of sorbent coatings for HS-SPME.     

Application of ionic liquid in liquid phase microextraction technology

Ionic liquids (ILs) are novel nonmolecular solvents. Their unique properties, such as high thermal stability, tunable viscosity, negligible vapor pressure, nonflammability, and good solubility for inorganic and organic compounds, make them excellent candidates as extraction media for a range of microextraction techniques. Many physical properties of ILs can be varied, and the structural design can be tuned to impart the desired functionality and enhance the analyte extraction selectivity, efficiency, and sensitivity. This paper provides an overview of the applications of ILs in liquid phase microextraction technology, such as single‐drop microextraction, hollow fiber based liquid phase microextraction, and dispersive liquid–liquid microextraction. The sensitivity, linear calibration range, and detection limits for a range of target analytes in the methods were analyzed to determine the advantages of ILs in liquid phase microextraction.     

Sorbent coatings for solid-phase microextraction based on mixtures of polymeric ionic liquids

Four polymeric ionic liquids based on two different cations, poly(1‐vinyl‐3‐hexylimidazolium) and poly(1‐vinyl‐3‐hexadecylimidazolium), combined with two different anions, bis[(trifluoromethyl)sulfonyl]imide (NTf) and chloride (Cl^?), were combined in various weight percentages and used as sorbent coatings for solid‐phase microextraction gas chromatography (SPME‐GC). The selectivity of the fiber coatings for 12 test analytes was examined. The extraction efficiency of n‐alcohols increased with an increase in the weight percentage of chloride ion in the sorbent coating. The ability to tune the interactions between the coating material and the analytes was exploited and resulted in distinct changes in the limits of detection for hydrogen‐bonding analytes with varying chloride ion content in the sorbent coating.     

Analysis of quinolones by voltage-assisted liquid-phase microextraction combined with LC-MS

The method of liquid-phase microextraction assisted with voltage was developed and applied on determination of quinolones in water sample in this study. Both of the reproducibility and extraction time were improved with the aid of applying voltage. Four analytes in neutral state such as cinoxacin, oxolinic acid, nalidixic acid, and flumequine were extracted from a sample solution at pH 2.0, through a polypropylene hollow fiber which was immobilized with 2-octanone, and then into a 25 μL of the acceptor phase of 40 mM borate buffer at pH 10.0 by applying voltage of 100 V. Subsequently, the acceptor solution was directly subjected to analysis by LC-MS. The performance of the method for four quinolones was also evaluated. Linearity was obtained in the range of 1.0-25.0 ng/mL with R(2) > 0.996. Limits of detection were below 0.6 ng/mL, and recoveries of water sample were ranged from 90.8 to 109.6%.     

Determination of phenols in environmental water samples by ionic liquid-based headspace liquid-phase microextraction coupled with high-performance liquid chromatography

Headspace liquid-phase microextraction (HS-LPME) has been applied to efficient enrichment of phenols such as 2-nitrophenol, 4-chlorophenol, 2,4-dichlorophenol, and 2-naphthol from water samples based on 1-butyl-3-methylimidazolium hexafluorophosphate ([C4MIM][PF6]) as an extractant. Some parameters that may influence HS-LPME were investigated. The linear range was in the range of 0.5-100 microg/L, and the enrichment factors and repeatability (RSD, n = 6) of the proposed method were in the range of 17.2-160.7 and 5.4-8.9%, respectively. The detection limit for each analyte ranged from 0.3 to 0.5 microg/L. Complex matrices of environmental water samples had a small effect on the enrichment, and this problem could be resolved by the addition of sodium ethylene diamine tetraacetate (EDTA) into the samples. The spiked recoveries were in the range of 89.4-114.2%. All these facts demonstrated that the proposed method, with merits of low cost, simplicity, and easy operation, would be a competitive alternative procedure for the determination of such compounds at trace level.     

Hollow fiber supported ionic liquid membrane microextraction for determination of sulfonamides in environmental water samples by high-performance liquid chromatography

By using ionic liquid as membrane liquid and tri-n-octylphosphine oxide (TOPO) as additive, hollow fiber supported liquid phase microextraction (HF-LPME) was developed for the determination of five sulfonamides in environmental water samples by high-performance liquid chromatography with ultraviolet detection The extraction solvent and the parameters affecting the extraction enrichment factor such as the type and amount of carrier, pH and volume ratio of donor phase and acceptor phase, extraction time, salt-out effect and matrix effect were optimized. Under the optimal extraction conditions (organic liquid membrane phase: [C₈MIM][PF₆] with 14% TOPO (w/v); donor phase: 4 mL, pH 4.5 KH₂PO₄ with 2 M Na₂SO₄; acceptor phase: 25 μL, pH 13 NaOH; extraction time: 8 h), low detection limits (0.1–0.4 μg/L, RSD ≤ 5%) and good linear range (1–2000 ng/mL, R² ≥ 0.999) were obtained for all the analytes. The presence of humic acid (0–25 mg/L dissolved organic carbon) and bovine serum albumin (0–100 μg/mL) had no significant effect on the extraction efficiency. Good spike recoveries over the range of 82.2–103.2% were obtained when applying the proposed method on five real environmental water samples. These results indicated that this present method was very sensitive and reliable with good repeatabilities and excellent clean-up in water samples. The proposed method confirmed hollow fiber supported ionic liquid membrane based LPME to be robust to monitoring trace levels of sulfadiazine, sulfamerazine, sulfamethazine, sulfadimethoxine and sulfamethoxazole in aqueous samples.     

Determination of estrogens in wastewater using three-phase hollow fiber-mediated liquid-phase microextraction followed by HPLC

Three-phase hollow fiber-mediated liquid-phase microextraction followed by HPLC was used for the determination of three synthetic estrogens, namely diethylstilbestrol, dienestrol, and hexestrol, in wastewater. Extraction conditions including organic solvent, volume ratio between donor solution and acceptor phase, extraction time, stirring rate, donor phase and acceptor phase were optimized. The target compounds were extracted from a 10 mL aqueous sample at pH 1.5 (donor solution) through a 45 mm in length hollow polypropylene fiber that was immersed in 1-octanol in advance, and then the hollow fiber was filled with 10 microL 0.5 mol/L sodium hydroxide solution (acceptor phase). After a 40 min extraction, the acceptor phase was directly injected into an HPLC system for detection. Under the optimized extraction conditions, a large enrichment factor (more than 300-fold) was achieved for the three estrogens. The determination limit at an S/N of 3 ranged from 0.25 to 0.5 microg/L for the estrogens. The recovery ratio was more than 86% in the determination of these estrogens in wastewater.     

Solid-phase extraction of room-temperature imidazolium ionic liquids from aqueous environmental samples

Owing to their favorable properties, ionic liquids have recently gained recognition as possibly environmentally benign solvents. Now among the most promising industrial chemicals, they have already been labeled green, but this appellation seems due entirely to their very low vapor pressure. This growing interest in the various applications of ionic liquids will soon result in their presence in the environment. Therefore, reliable analytical tools for the environmental analysis of ionic liquids need to be developed urgently. This paper presents a newly developed analytical procedure for the enrichment of 1-alkyl- and 1-aryl-3-methylimidazolium ionic liquids from water samples. The method is based on cation exchange solid-phase extraction followed by selective elution. Pre-concentrated samples are subjected to high-performance liquid chromatography (HPLC) with an advanced methodology for qualitative and quantitative analysis. The overall procedure was verified by using standard spiked samples of tap water, seawater, and freshwater.     

Stereoselective determination of hydroxychloroquine and its metabolites in human urine by liquid-phase microextraction and CE

Liquid-phase microextraction based on polypropylene hollow fibers and CE were applied for the chiral determination of hydroxychloroquine (HCQ) and its metabolites (desethylchloroquine, DCQ; desethylhydroxychloroquine, DHCQ; bisdesethylchloroquine, BDCQ) in human urine. The analytes were extracted from 3 mL of urine spiked with the internal standard (metoprolol) and alkalinized with 250 muL of 2 M NaOH. The analytes were extracted into 1-octanol impregnated in the pores of the hollow fiber, and into an acid acceptor solution inside the hollow fiber. The electrophoretic separations were carried out in 100 mmol/L Tris buffer (pH adjusted to 9.0 with phosphoric acid) containing 1% w/v S-beta-CD and 30 mg/mL HP-beta-CD with a constant voltage of +18 kV. The method was linear over the concentration range of 10-1000 ng/mL for each HCQ stereoisomer and 21-333 ng/mL for each metabolite stereoisomer. Within-day and between-day assay precision and accuracy for the analytes were studied at three concentration levels for each stereoisomer and were lower than 15%. The developed method was applied for the determination of the cumulative urinary excretion of HCQ, DCQ, and DHCQ after oral administration of rac-HCQ to a health volunteer. The results obtained are in agreement with previous literature data.     

Determination of formaldehyde in shiitake mushroom by ionic liquid-based liquid-phase microextraction coupled with liquid chromatography

Using ionic liquid as extraction solvent and 2,4-dinitrophenylhydrazine (DNPH) as derivative agent, formaldehyde in shiitake mushroom was determined by liquid-phase microextraction coupled with high-performance liquid chromatography (HPLC). Shiitake mushroom was leached with water and filtrated, then the formaldehyde in filtrate was derivatized with DNPH and extracted simultaneously into a 10 μl drop of ionic liquid suspended on the tip of the microsyringe, and finally injected into the HPLC system for determination. The proposed procedure has a detection limit of 5 μg l⁻¹ formaldehyde in extraction solution, thus the mushroom sample filtrate could be diluted with a large ratio to eliminate the influence of sample matrix. The method has a relative standard deviation of 3.5% between days for 53.5 μg l⁻¹ formaldehyde standards. High contents of formaldehyde (119-494 μg g⁻¹ wet weight), which is harmful for human beings, were detected in shiitake mushroom. Therefore, strategies must be taken to prevent the accumulation and strictly control the content of formaldehyde in shiitake mushroom.     

Application of new approaches to liquid-phase microextraction for the determination of emerging pollutants

Liquid-liquid extraction (LLE) has been widely used as a pre-treatment technique for separation and preconcentration of organic analytes from aqueous samples. Nevertheless, this technique has several drawbacks, mainly in the use of large volumes of solvents, making LLE an expensive, environmentally-unfriendly technique.Miniaturized methodologies [e.g., liquid-phase microextraction (LPME)] have arisen in the search for alternatives to conventional LLE, using negligible volumes of extracting solvents and reducing the number of steps in the procedure. Developments have led to different approaches to LPME, namely single-drop microextraction (SDME), hollow-fiber LPME (HF-LPME), dispersive liquid-liquid microextraction (DLLME) and solidified floating organic drop microextraction (SFODME).This overview focuses on the application of these microextraction techniques to the analysis of emerging pollutants.     

Insitu growth of IRMOF-3 combined with ionic liquids to prepare solid-phase microextraction fibers

A superior solid-phase microextraction (SPME) fiber-coating material, IRMOF-3@ILs/PDMS, was prepared by the in situ growth of IRMOF-3 onto stainless-steel wires and protection with ionic liquids (ILs) and polydimethylsiloxane (PDMS). The ILs can efficiently prevent the substantial cracking of IRMOF-3 caused by moisture, and a thin PDMS film can protect the IRMOF-3@ILs material to achieve a much better extraction efficiency as well as excellent resistance to high temperature and high humidity. This IRMOF-3@ILs/PDMS coating possessed a porous structure, a rough surface and an increased lifespan (by at least 100 times) compared with that of IRMOF-3. The coating was evaluated by analyzing four polycyclic aromatic hydrocarbons (PAHs) in water, and good precision (<7.7%), low detection limits (12.0–15.4 ng L⁻¹), and wide linearity (50–20,000 ng L⁻¹) were achieved under the optimized conditions. The fiber was successfully applied to the sensitive analysis of PAHs in rainwater by coupling it with gas chromatography–mass spectrometry (GC–MS).     

Chemical immobilization of crosslinked polymeric ionic liquids on nitinol wires produces highly robust sorbent coatings for solid-phase microextraction

Super elastic nitinol (NiTi) wires were exploited as highly robust supports for three distinct crosslinked polymeric ionic liquid (PIL)-based coatings in solid-phase microextraction (SPME). The oxidation of NiTi wires in a boiling (30% w/w) H₂O₂ solution and subsequent derivatization in vinyltrimethoxysilane (VTMS) allowed for vinyl moieties to be appended to the surface of the support. UV-initiated on-fiber copolymerization of the vinyl-substituted NiTi support with monocationic ionic liquid (IL) monomers and dicationic IL crosslinkers produced a crosslinked PIL-based network that was covalently attached to the NiTi wire. This alteration alleviated receding of the coating from the support, which was observed for an analogous crosslinked PIL applied on unmodified NiTi wires. A series of demanding extraction conditions, including extreme pH, pre-exposure to pure organic solvents, and high temperatures, were applied to investigate the versatility and robustness of the fibers. Acceptable precision of the model analytes was obtained for all fibers under these conditions. Method validation by examining the relative recovery of a homologous group of phthalate esters (PAEs) was performed in drip-brewed coffee (maintained at 60 °C) by direct immersion SPME. Acceptable recoveries were obtained for most PAEs in the part-per-billion level, even in this exceedingly harsh and complex matrix.     

Speciation analysis of mercury in sediments using ionic‐liquid‐based vortex‐assisted liquid–liquid microextraction combined with high‐performance liquid chromatography and cold vapor atomic fluorescence spectrometry

An improved novel method based on ionic liquid vortex‐assisted liquid–liquid microextraction has been developed for the extraction of methylmercury, ethylmercury and inorganic mercury in sediment samples prior to analysis by high‐performance liquid chromatography with cold vapor atomic fluorescence spectrometry. In this work, mercury species were firstly complexed with dithizone, and the complexes were extracted into 1‐hexyl‐3‐methylimidazolium hexafluorophosphate. Key factors that affect the extraction efficiency of mercury species, such as type and amount of ionic liquid and chelatants, extraction time, sample pH, salt effect and matrix effect were investigated. Under the optimum conditions, linearity was found in the concentration range from 0.1–70 ng/g. Limits of detection ranged from 0.037–0.061 ng/g. Reproducibility and recoveries were assessed by extracting a series of six independent sediment samples that were spiked with different concentration levels. Finally, the proposed method was successfully applied in analysis of real sediment samples. In this work, ionic liquids vortex‐assisted liquid–liquid microextraction was for the first time used for the extraction of mercury species in sediment samples. The proposed method was proved to be much simpler and more rapid, as well as more environmentally friendly and efficient compared with the previous methods.     

Preparation and characterization of novel crown ether functionalized ionic liquid-based solid-phase microextraction coatings by sol-gel technology

A novel crown ether functionalized ionic liquid (IL), 1-allyl-3-(6'-oxo-benzo-15-crown-5 hexyl) imidazolium hexafluorophosphate was synthesized and used as selective stationary phase to prepare task-specific IL-based solid phase microextraction (SPME) fibers by sol-gel method and free radical cross-linking technology. The underlying mechanism of the sol-gel reaction was proposed and the successful chemical bonding of the crown ether functionalized IL to the formed hybrid organic-inorganic copolymer coating was confirmed by FT-IR spectroscopy. The performance of this in situ created crown ether functionalized IL-based SPME fibers, was investigated in detail. The coating has porous surface structure, stable performance in high temperature (to 340 °C) and in different solutions (water, organic solvent, acid and alkali), and good coating preparation reproducibility. In contrast to the sol-gel derived 1-allyl-3-methyl imidazolium hexafluorophosphate-based coating prepared in our previous work with the identical procedure, the extraction performance of this newly developed sol-gel crown ether functionalized IL-based coating was superior for alcohols, phthalate esters, phenolic environmental estrogens, fatty acids and aromatic amines due to the introduction of benzo-15-crown-5 functional group in IL structure. Moreover, it was shown to provide higher or comparable extraction efficiencies for most analytes studied than did the commercial PDMS, PDMS/DVB and PA fibers.     

Reduction of silanophilic interactions in liquid chromatography with the use of ionic liquids

A suppression of silanophilic interactions by the selected ionic liquids added to the mobile phase in thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) is reported. Acetonitrile was used as the eluent, alone or with various concentrations of water and phosphoric buffer pH 3. Selectivity of the normal (NP) and the reversed (RP) stationary phase material was examined using a series of proton-acceptor basic drugs analytes. The ionic liquids studied appeared to significantly affect analyte retention in NP-TLC, RP-TLC and RP-HPLC systems tested. Consequently, the increased separation selectivity was attained. Due to ionic liquid additives to eluent even analytes could be chromatographed, which were not eluted from the silica-based stationary phase materials with 100% of acetonitrile in the mobile phase. Addition of ionic liquid already in very small concentration (0.5%, v/v) could reduce the amount of acetonitrile used during the optimization of basic analytes separations in TLC and HPLC systems. Moreover, the influence of temperature on the separation of basic analytes was demonstrated and considered in practical HPLC method development.     

Basalt fibers grafted with a poly(ionic liquids) coating for in‐tube solid‐phase microextraction

To improve the durability and extraction efficiency of an ionic liquid coating, 1‐dodecyl‐3‐vinylimidazolium bromide was polymerized and grafted onto basalt fibers for in‐tube solid‐phase microextraction. To develop an extraction tube, basalt fibers grafted with the poly(ionic liquids) coating were filled into a polyether ether ketone tube with a 0.75 mm inner diameter. The extraction tube was connected to high‐performance liquid chromatography system equipped with a sampling pump to build an online enrichment and analysis system. Using four common phthalates as model analytes, the extraction tube was investigated by the online analysis system. Good enrichment performance was exhibited by high enrichment factors ranging from 851 to 1858. Under the optimum conditions, an online analysis method was established, and good linearity (0.03–12 and 0.15–12 μg/L) and low limits of detection (0.01–0.05 μg/L) were achieved. This analysis method was applied to real samples including water in a disposable plastic box and the bottled water, some targets were detected but not quantified, and the relative recoveries spiked at 2, 5 and 10 μg/L were in the range of 86.4–119.5%.