Ionic Liquid-based Single-drop Microextraction Research Articles

Dynamic Ultrasonic Nebulisation Extraction Coupled with Headspace Ionic Liquid‐based Single‐drop Microextraction for the Analysis of the Essential Oil in Forsythia suspensa

Ionic liquids have attracted much attention as an extraction solvent instead of traditional organic solvent in single-drop microextraction. However, non-volatile ionic liquids are difficult to couple with gas chromatography. Thus, the following injection system for the determination of organic compounds is described. To establish an environmentally friendly, simple, and effective extraction method for preparation and analysis of the essential oil from aromatic plants. The dynamic ultrasonic nebulisation extraction was coupled with headspace ionic liquid-based single-drop microextraction(UNE-HS/IL/SDME)for the extraction of essential oils from Forsythia suspense fruits. After 13 min of extraction for 50 mg sample, the extracts in ionic liquid were evaporated rapidly in the gas chromatography injector through a thermal desorption unit (5 s). The traditional extraction method was carried out for comparative study. The optimum conditions were: 3 μL of 1-methyl-3-octylimidazolium hexafluorophosphate was selected as the extraction solvent, the sample amount was 50 mg, the flow rate of purging gas was 200 mL/min, the extraction time was 13 min, the injection volume was 2 μL, and the thermal desorption temperature and time were 240 °C and 5 s respectively. Comparing with hydrodistillation (HD), the proposed method was environment friendly and efficient. The proposed method is environmentally friendly, time saving, with high efficiency and low consumption. It would extend the application range of the HS/SDME and would be useful especially for aromatic plants analysis.

Ultrasonic nebulization headspace ionic liquid-based single drop microextraction of flavour compounds in fruit juices

The ultrasonic nebulization headspace ionic liquid-based single drop microextraction was developed for the extraction of flavour constituents from fruit juices. The GC–MS was applied to the separation and detection of the constituents. The parameters affecting extraction performance, such as microdrop volume, extraction time, enrichment time, extraction temperature, and position of microdrop, were investigated and optimized. The optimized system was: ionic liquid, 1-hexyl-3-methylimidazolium tetrafluroborate; solvent microdrop volume, 12.5μL; extraction time, 5min; enrichment time, 20min; extraction temperature, 80°C; the height of the microdrop above the solution surface, 1cm; and, the pH value of sample solution did not affect the species, and solubility of analytes. The recoveries were in the range of 80.4–115.0%, and the relative standard deviations were lower than 9.1%. The present method is a simple and sensitive method for the determination of flavour constituents in fruit juices.

On-line coupling of ionic liquid-based single-drop microextraction and capillary electrophoresis for determination of three bromophenols in water samples

An ionic liquid-based single-drop microextraction (IL-SDME) procedure using IL as an extractant on-line coupled to capillary electrophoresis (CE) is proposed. The method is capable of quantifying trace amounts of bromophenols in water samples. The extraction parameters such as extraction solvent, extraction time, ionic liquid single-drop volume, ionic strength and organic solvent were systematically investigated. For the SDME of the three bromophenols, a [C4MIM] [ PF6,] microdrop was exposed for 8 min to the aqueous sample with 10% (w/w) NaCI and then was directly injected into a capillary column for analysis. Under the optimal conditions, good linear relationships were obtained in the concentration range of 1 - 100 mg/L with the correlation coefficients of 0. 993 9 - 0. 998 8 for the bromophenols. The detection limits of the three bromophenols were 0. 3 mg/L. The RSDs of peak areas of the standards were 5. 21%- 6.47% (n =6). And the enrichment factors for the three bromophenols were 115.8, 327.0 and 569. 8. The proposed method was applied to the determination of the three bromophenols in tap, river and lake waters with the recoveries of the three bromophenols in the range of 87.8% - 96.7%. The method is suitable for the quantification of bromophenols in water samples.

A new coupling of ionic liquid based-single drop microextraction with tungsten coil electrothermal atomic absorption spectrometry

In this work, an improved method of ionic liquid based-single drop microextraction (IL-SDME) preconcentration was firstly coupled with tungsten coil electrothermal atomic absorption spectrometry (W-coil ET-AAS) detection. The new coupling was developed and applied for the determination of ultra-trace cadmium. Experimental parameters influencing the performance of IL-SDME as well as instrumental conditions were studied systematically, including IL-drop volume, chelating agent concentration, pH, stirring rate and time, heating program of W-coil ET-AAS, flow rate of carrier gas. Under the optimal conditions, the limit of detection (LOD) for cadmium was 0.015μgL−1 (sampling amount on W-coil was 10μL). The sensitivity enhancement factor was 42, while the improvement factor of LOD was 33. The established method was applied to determine cadmium in standard reference materials of rice and real water samples successfully. The developed IL-SDME-W-coil ET-AAS coupling represents a simple, green and highly sensitive method for cadmium determination.

Determination of Sulfonamides in Water Sample Using Ionic Liquid-based Single Drop Microextraction Coupled with High Performance Liquid Chromatography

Determination of Sulfonamides in Water Sample Using Ionic Liquid-based Single Drop Microextraction Coupled with High Performance Liquid Chromatography

Chromatography: Determining o-nitrophenol in wastewater

Detecting o-nitrophenol in aquatic environments is a major issue around the world due its widespread use in many industrial processes. A study has now been concluded for the determination of o-nitrophenol in water using high performance liquid chromatography preceded by ionic liquid-based single drop microextraction.

Symmetrical 1,3-Dialkylimidazolium Ionic Liquid Based Single-Drop Microextraction Coupled to GC-MS for the Determination of Esters in Natural Flavors

Symmetrical 1,3-Dialkylimidazolium Ionic Liquid Based Single-Drop Microextraction Coupled to GC-MS for the Determination of Esters in Natural Flavors

Determination of 2,4,6-tricholoroanisole in water and wine samples by ionic liquid-based single-drop microextraction and ion mobility spectrometry

This article presents for the first time the joint use of ionic liquid-based single drop microextraction (IL-SDME) and ion mobility spectrometry (IMS) for the determination of 2,4,6-trichloroanisol (2,4,6-TCA) in water and wine samples. An imidazolium-based IL was used as extractant taking into account both, its affinity for the analyte and its negligible response in the detector. Water samples were directly analyzed by IL-SDME while wines required a previous solid phase extraction step to remove the interference of ethanol in the ion mobility spectra. All the parameters affecting the extraction were optimized in order to achieve the highest sensitivity, taking into account the lower concentrations reported for this compound in the matrices selected. Moreover, the use of ion mobility working under the negative ionization mode confers an adequate selectivity. The limits of detection and quantification were 0.2 and 0.66 ng L −1, respectively. The precision of the method calculated at 10 ng L −1 was 1.4% (repeatability, n = 5) and 2.2% (reproducibility, n = 5, 3 days). The analysis of water and wine samples reported the presence of 2,4,6-TCA in wine samples commercialized in bottles with cork stoppers.

Ionic liquid-based single drop microextraction of ultra-trace copper in food and water samples before spectrophotometric determination

In this work, room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium hexafluorophosphate ([C 4mim]PF 6) was used as extractant in single drop microextraction (SDME). The traditionally volatile organic extractants were substituted by this green reagent, which changed SDME preconcentration into environmentally friendly method, relatively. After this pretreatment, ultra-trace copper in water and food samples could be accurately detected by spectrophotometer. This study was focused on the improvement of the analytical performance of spectrophotometric determination, expanding its applications. The influence factors relevant to IL-SDME, such as absorption spectra of complex, drop volume of RTIL, stirring rate and time, concentration of chelating agent, pH, and salt effect were studied systematically. Under the optimal conditions, the limit of detection (LOD) was 0.15 μg L −1 with an enhancement factor (EF) of 33. The proposed method was green, simple, rapid, sensitive, and cost-efficient.

On-line coupling of ionic liquid-based single-drop microextraction with capillary electrophoresis for sensitive detection of phenols

An ionic liquid-based single-drop microextraction (IL-SDME) procedure using IL as an extractant on-line coupled to capillary electrophoresis (CE) is proposed. The method is capable of quantifying trace amounts of phenols in environmental water samples. For the SDME of three phenols, a 2.40 nL IL microdrop was exposed for 10 min to the aqueous sample and then was directly injected into the capillary column for analysis. Extraction parameters such as the extraction time, the IL single-drop volume, pH of the sample solution, ionic strength, volume of the sample solution and the extraction temperature were systematically investigated. Detection limits to three phenols were less than 0.05 μg mL −1, and their calibration curves were all linear ( R 2 ≥ 0.9994) in the range from 0.05 to 50 μg mL −1. And enrichment factors for three phenols were 156, 107 and 257 without agitation, respectively. This method was then utilized to analyze two real environmental samples from Yellow River and tap water, obtaining satisfactory results. Compared with the usual SDME for CE, IL-SDME–CE is a simple, low-cost, fast and environmentally friendly preconcentration technique.

Ionic liquid-based single-drop microextraction followed by liquid chromatography-ultraviolet spectrophotometry detection to determine typical UV filters in surface water samples

A user-friendly and inexpensive ionic liquid-based single-drop microextraction (IL-SDME) procedure has been developed to preconcentrate trace amounts of six typical UV filters extensively used in cosmetic products (i.e., 2-hydroxy-4-methoxybenzophenone, isoamyl 4-methoxycinnamate, 3-(4'-methylbenzylidene)camphor, 2-ethylhexyl 2-cyano-3,3-diphenylacrylate, 2-ethylhexyl 4-dimethylaminobenzoate and 2-ethylhexyl 4-methoxycinnamate) from surface water samples prior to analysis by liquid chromatography-ultraviolet spectrophotometry detection (LC-UV). A two-stage multivariate optimization approach was developed by means of a Plackett-Burman design for screening and selecting the significant variables involved in the SDME procedure, which were later optimized by means of a circumscribed central composite design. The studied variables were drop volume, sample volume, agitation speed, ionic strength, extraction time and ethanol quantity. Owing to particularities, ionic liquid type and pH of the sample were optimized separately. Under optimized experimental conditions (i.e., 10 microL of 1-hexyl-3-methylimidazolium hexafluorophosphate, 20 mL of sample containing 1% (v/v) ethanol and NaCl free adjusted to pH 2, 37 min extraction time and 1300 rpm agitation speed) enrichment factors up to ca. 100-fold were obtained depending on the target analyte. The method gave good levels of repeatability with relative standard deviations varying between 2.8 and 8.8% (n=6). Limits of detection were found in the low microg L(-1) range, varying between 0.06 and 3.0 microg L(-1) depending on the target analyte. Recovery studies from different types of surface water samples collected during the winter period, which were analysed and confirmed free of all target analytes, ranged between 92 and 115%, showing that the matrix had a negligible effect upon extraction. Finally, the proposed method was applied to the analysis of different water samples (taken from two beaches, two swimming pools and a river) collected during the summer period.

Ionic liquid-based single drop microextraction and room-temperature gas chromatography for on-site ion mobility spectrometric analysis

The combination of ionic liquid-based headspace single drop microextraction (IL-HS-SDME) and room-temperature gas chromatography/ion mobility spectrometry (RTGC-IMS) is presented for the first time using the direct determination of trihalomethanes in waters as model analytical problem. The ionic liquid allows the transference of the analytes from the sample to the analytical system, at the same time that it provides an increase of the sensitivity and selectivity of the determination. An injection unit has been designed to permit the efficient volatilization of the analytes at room temperature and to avoid the entering of IL in the system. The direct combination allows the determination of the halocompounds in a rapid and simple way taking advance of their characteristic IMS spectra. The limits of the detection range between 0.1 ng mL −1 (bromoform) and 0.9 ng mL −1 (chloroform), the reproducibility of the system being better than 7.1% (RSD). The proposed coupling opens up a new horizon in IMS-based applications.

Simple and commercial readily-available approach for the direct use of ionic liquid-based single-drop microextraction prior to gas chromatography: Determination of chlorobenzenes in real water samples as model analytical application

A simple and commercial readily-available approach that enables the direct use of ionic liquid (IL)-based single-drop microextraction (SDME) prior to gas chromatography (GC) is presented. The approach is based on thermal desorption (TD) of the analytes from the IL droplet to the GC system, by using a robust and commercially-available thermodesorption system. For this purpose, a two-glass-tube concentrically disposed system was designed. The inner tube is a laboratory-cut Pyrex tube (20mm length) that houses the ionic liquid droplet from the SDME process, and the outer tube is a commercially-available TD glass tube (187mm length) commonly employed for stir-bar sorptive extractions (SBSE). In this way, the proposed device prevents IL from entering the GC system, as this could dirty the inlet or even block the column. The determination of 10 chlorobenzenes in water samples by GC coupled with mass spectrometric (MS) detection has been chosen as model analytical application, showing the feasibility of the proposed approach. The SDME process consists of a 5μL droplet of 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]) suspended in the headspace (HS) of a 10mL stirred sample. After extracting for 37min at room temperature, the IL droplet is directly placed into the small inner tube, which is placed into the TD tube. The whole device is placed inside the TD unit, where desorption of the analytes is performed at 240°C for 5min with a helium flow rate of 100mLmin−1. The analytical figures of merit of the proposed IL-(HS)-SDME-TD-GC–MS approach are very suitable for the determination of chlorobenzenes at ultratrace levels, with relative standard deviation values ranging between 2% and 17%, and limits of detection ranging between 1 and 4ngL−1, showing the potential offered by the IL-based SDME process with GC.

Speciation of mercury by ionic liquid-based single-drop microextraction combined with high-performance liquid chromatography-photodiode array detection

Room temperature ionic liquids can be considered as environmentally benign solvents with unique physicochemical properties. Ionic liquids can be used as extractant phases in SDME, being compatible with chromatographic systems. A single-drop microextraction method was developed for separation and preconcentration of mercury species (MeHg +, EtHg +, PhHg + and Hg 2+), which relies on the formation of the corresponding dithizonates and microextraction of these neutral chelates onto a microdrop of an ionic liquid. Afterwards, the separation and determination were carried out by high-performance liquid chromatography with a photodiode array detector. Variables affecting the formation and extraction of mercury dithizonates were optimized. The optimum conditions found were: microextraction time, 20 min; stirring rate, 900 rpm; pH, 11; ionic liquid type, 1-hexyl-3-methylimidazolium hexafluorophosphate ([C 6MIM][PF 6]); drop volume, 4 μL; and no sodium chloride addition. Limits of detection were between 1.0 and 22.8 μg L −1 for the four species of mercury, while the repeatability of the method, expressed as relative standard deviation, was between 3.7 and 11.6% ( n = 8). The method was finally applied to the determination of mercury species in different water samples.

Ionic liquid-based single drop microextraction combined with electrothermal atomic absorption spectrometry for the determination of manganese in water samples

Room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate [C 4MIM][PF 6], was used as an alternative to volatile organic solvents in single drop microextraction-electrothermal atomic absorption spectrometry (SDME-ETAAS). Manganese was extracted from aqueous solution into a drop of the ionic liquid after complextaion with 1-(2-thiazolylazo)-2-naphthol (TAN) and the drop was directly injected into the graphite furnace. Several variables affecting microextraction efficiency and ETAAS signal, such as pyrolysis and atomization temperature, pH, TAN concentration, extraction time, drop volume and stirring rate were investigated and optimized. In the optimum experimental conditions, the limit of detection (3 s) and the enhancement factor were 0.024 μg L −1 and 30.3, respectively. The relative standard deviation (RSD) for five replicate determinations of 0.5 μg L −1 Mn(II) was 5.5%. The developed method was validated by the analysis of a certified reference material (NIST SRM 1643e) and applied successfully to the determination of manganese in several natural water samples.

Ionic liquid-based single-drop microextraction/gas chromatographic/mass spectrometric determination of benzene, toluene, ethylbenzene and xylene isomers in waters

The direct coupling between ionic liquid-based single-drop microextraction and gas chromatography/mass spectrometry is proposed for the rapid and simple determination of benzene, toluene, ethylbenzene and xylenes isomers (BTEX) in water samples. The extraction procedure exploits not only the high affinity of the selected ionic liquid (1-methyl-3-octyl-imidazolium hexaflourophosphate) to these aromatic compounds but also its special properties like viscosity, low vapour pressure and immiscibility with water. All the variables involved in the extraction process have been studied in depth. The developed method allows the determination of these single-ring compounds in water under the reference concentration level fixed by the international legislation. In this case, limits of detection were in the range 20 ng L −1 (obtained for benzene) and 91 ng L −1 (for o-xylene). The repeatability of the proposed method, expressed as RSD ( n = 5), varied between 3.0% ( o-xylene) and 5.2% (toluene).

Direct Coupling of Ionic Liquid Based Single-Drop Microextraction and GC/MS

The use of ionic liquids as extracting media in single-drop liquid-phase microextraction (SDME) and its direct coupling to gas chromatography/mass spectrometry (GC/MS) is presented. For this purpose, a new removable interface that enables the introduction of the extracted analytes into the GC system, while preventing the ionic liquid from entering the column, has been developed. The determination of three representative pollutants in water samples has been used as a model analytical problem in order to demonstrate the feasibility of the proposed interface. The analytes (dichloromethane, p-xylene, and n-undecane) were coextracted from the aqueous sample in a 2-microL drop of 1-butyl-3-methylimidazolium hexaflourophosphate. Then, the syringe used to perform the SDME was directly introduced into the interface, which was held at 140 degrees C in order to achieve a complete volatilization of the target compounds. After the injection, the ionic liquid was retained in the interface, while a carrier gas transferred the volatilized analytes into the GC inlet. The optimization of the operational variables affecting the new interface (temperature, carrier flow rate, sample volume and injection technique) was accomplished. The analytes could be determined with detection limits in the low-nanogram per milliliter concentration range, and the relative standard deviations were between 3.3 and 4.4%.