Ionic liquid/ionic liquid dispersive liquid-liquid microextraction

In this article, a novel and simple microextraction method, termed ionic liquid/ionic liquid dispersive liquid–liquid microextraction (IL/IL‐DLLME), has been designed and developed for the rapid enrichment and analysis of environmental pollutants. Instead of using hazardous organic solvents, two kinds of ILs, hydrophobic IL and hydrophilic IL, were used as extraction solvent and disperser solvent in IL/IL‐DLLME step, respectively. Permethrin and biphenthrin, two of the often‐used pyrethroid pesticides, were used as model compounds. Factors that may affect the enrichment efficiencies were investigated and optimized in detail. Under optimum conditions, permethrin and biphenthrin exhibited a wide linear relationship over the range 1–100 μg/L. For permethrin and biphenthrin, the precisions were 4.65–7.78%, and limits of detection were found to be 0.28 and 0.83 μg/L, respectively. Satisfactory results were achieved when the present method was applied to analyze the target compounds in real‐world water samples with spiked recoveries over the range 84.1–113.5%. All these facts indicated that IL/IL‐DLLME is a simple and rapid alternative for the enrichment and analysis of environmental pollutants and will have a wide application perspective in the future.     

A ionic liquid for dispersive liquid-liquid microextraction of phenols

In the present study, a new solvent-free mode of liquid phase microextraction termed ionic liquid dispersive liquid-liquid microextraction (IL-DLLME) was developed. Four phenols were used as model compounds in the development and evaluation of the procedure. In this method, 50 μL of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF₆]) and 1.5 mL of sample aqueous solution were placed in a 2.2-mL glass test tube and mixed by aspirating and rapidly injecting by a syringe. This procedure produced a cloudy solution. In this process, phenols in the water sample were extracted into the IL phase. After centrifuging, the fine droplets of IL sedimented to the bottom of the glass test tube. The settled phase was injected into the high performance liquid chromatograph (HPLC) for separation and detection of phenols. Some parameters that might affect the extraction efficiency were optimized. The main advantages of the proposed method are high speed, high recovery, good repeatability and environmental friendliness.     

Determination of phenolic compounds in water samples by HPLC following ionic liquid dispersive liquid-liquid microextraction and cold-induced aggregation

We report on the determination of bisphenol A and 2-naphthol in water samples using ionic liquid cold-induced aggregation dispersive liquid-liquid microextraction combined with HPLC. Parameters governing the extraction efficiency (disperser solvent, volume of extraction and disperser solvent, pH, temperature, extraction time) were optimized and resulted in enrichment factors of 112 for bisphenol A and of 186 for 2-naphthol. The calibration curve was linear with correlation coefficients of 0.9995 and 0.9998, respectively, in the concentration range from 1.5 to 200?ng?mL^?1. The relative standard deviations are 2.3% and 4.1% (for n?=?5), the limits of detection are 0.58 and 0.86?ng?mL^?1, and relative recoveries in tap, lake and river water samples range between 100.1 and 108.1%, 99.4 and 106.2%, and 97.1 and 103.8%, respectively.

Determination of rifaximin in rat serum by ionic liquid based dispersive liquid-liquid microextraction combined with RP-HPLC

An efficient and environmental friendly ionic liquid based dispersive liquid-liquid microextraction procedure was optimized for determination of rifaximin in rat serum by reverse phase high-performance liquid chromatography. The effect of ionic liquids, dispersive solvents, extractant/disperser ratio, and salt concentrations on sample recovery and enrichment factors were studied. Among the five ionic liquids studied in the present investigation, 1-butyl-3-methylimidazolium hexafluorophosphate was found to be most effective for extraction of rifaximin. The recovery was found to be more than 98% using 1-butyl-3-methylimidazolium hexafluorophosphate and methanol as extraction and dispersive solvents, at an extractant/disperser ratio of 0.43. The recovery was further enhanced to 99.5% by the addition of 5.0% NaCl solution. A threefold enhancement in detection limit was achieved when compared to protein precipitation. The ionic liquid containing the extracted rifaximin was directly injected into HPLC system. The linear relationship was observed in the range of 0.03-10.0 μg/mL with the correlation coefficient (r(2) ) 0.9998. Limits of detection and quantification were found to be 0.01 and 0.03 μg/mL, respectively. The relative standard deviation was 2.5%. The method was validated and applied to study pharmacokinetics of rifaxmin in rat serum.     

Quantitation of antioxidants in water samples using ionic liquid dispersive liquid-liquid microextraction followed by high-performance liquid chromatography-ultraviolet detection

A simple and efficient method, ionic liquid-based dispersive liquid-liquid microextraction combined with high-performance liquid chromatography-ultraviolet detection (HPLC-UV), has been applied for the extraction and determination of some antioxidants (Irganox 1010, Irganox 1076 and Irgafos 168) in water samples. The microextraction efficiency factors were investigated and optimized: 1-hexyl-3-methylimidazolium hexafluorophosphate [C(6)MIM][PF(6)] (0.06 g) as extracting solvent, methanol (0.5 mL) as disperser solvent without salt addition. Under the selected conditions, enrichment factors up to 48-fold, limits of detection (LODs) of 5.0-10.0 ng/mL and dynamic linear ranges of 25-1500 ng/mL were obtained. A reasonable repeatability (RSD≤11.8%, n=5) with satisfactory linearity (r(2)≥0.9954) of the results illustrated a good performance of the presented method. The accuracy of the method was tested by the relative recovery experiments on spiked samples, with results ranging from 85 to 118%. Finally, the method was successfully applied for determination of the analytes in several real water samples.     

Temperature-induced aggregation ionic liquid dispersive liquid-liquid microextraction method for separation trace amount of cobalt ion

A simple and rapid temperature induced aggregation micro extraction method based on ionic liquid for extraction and preconcentration of cobalt ions from water samples was proposed. In this investigation small amounts of 1-hexyl-3-methylimidazolium hexafluorophosphate [Hmim][PF₆] and 1-hexyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide [Hmim][Tf₂N] (as extractant solvents) were added in a sample solution containing Triton X-114 (as an anti-sticking agent). After centrifuging the cooled solution, analysis was carried out by flame atomic absorption spectrophotometry. Some effective parameters have been optimized. Under the optimum conditions, detection limit of the method was 0.44 ng/mL and the relative standard deviation (RSD) for 100.0 ng/mL cobalt was ±2.3% (n = 7).The calibration curve was linear in the range of 3.0–200.0 ng/mL cobalt and enrichment factor was obtained as 26.5. The applicability of the technique was evaluated by the determination of trace amounts of cobalt in several water samples and synthetic alloys.     

Orthogonal array optimization of ionic liquid based dispersive liquid-liquid microextraction for toxic anilines in foods

A simple and rapid method of ionic liquid based dispersive liquid-liquid microextraction(DLLME) combining with high performance liquid chromatography(HPLC) was developed for the analysis of four toxic anilines in flour steamed bread and maize steamed bread.Several possible influential factors such as the type of ionic liquid and disperser solvent,extraction time,sample pH,ionic strength and the volume of ionic liquid and disperser solvent were optimized using single factor experiments and orthogonal array design(OAD) with OA 25(5 4) matrix.Analysis of variance(ANOVA) and percent contribution(PC) were used to investigate the significance of the factors of OAD.Sample pH and ionic strength are statistically demonstrated two chief factors.Under the optimum condition,the method exhibits a good linearity(r 2 > 0.99) over the studied range(50-1000 ng g 1) for anilines.The extraction factors and recoveries for the anilines in two kinds of steamed breads ranged between 34.1%-73.3% and 44.3%-95.3%,respectively.The limit of detections(LODs) and limit of quantitations(LOQs) ranged between 10-15 ng g 1 and 30-45 ng g-1.     

Determination of phthalate esters in water samples by ionic liquid cold-induced aggregation dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography

A novel method, termed ionic liquid cold-induced aggregation dispersive liquid–liquid microextraction (IL-CIA-DLLME), combined with high-performance liquid chromatography (HPLC) was developed for the determination of three phthalate esters in water samples. Several important parameters influencing the IL-CIA-DLLME extraction efficiency, such as the type of extraction and disperser solvent, the volume of extraction and disperser solvent, temperature, extraction time and salt effect, were investigated. Under optimal extraction conditions, the enrichment factors and extraction recoveries ranged from 174 to 212 and 69.9 to 84.8%, respectively. Excellent linearity with coefficients of correlation from 0.9968 to 0.9994 was observed in the concentration range of 2–100 ng mL⁻¹. The repeatability of the proposed method expressed as relative standard deviations ranged from 2.2 to 3.7% (n = 5). Limits of detection were between 0.68 and 1.36 ng mL⁻¹. Good relative recoveries for phthalate esters in tap, bottled mineral and river water samples were obtained in the ranges of 91.5–98.1%, 92.4–99.2% and 90.1–96.8%, respectively. Thus, the proposed method has excellent potential for the determination of phthalate esters in the environmental field.     

Determination of formaldehyde in beverages using microwave-assisted derivatization and ionic liquid-based dispersive liquid-liquid microextraction followed by high-performance liquid chromatography

A simple method based on simultaneous microwave-assisted derivatization and ionic liquid-based dispersive liquid-liquid microextraction (IL-based DLLME) is proposed for the derivatization, extraction and preconcentration of formaldehyde in beverage samples prior to the determination by high-performance liquid chromatography (HPLC). Formaldehyde was in situ derivatized with 2,4-dinitrophenylhydrazine (DNPH) and simultaneously extracted and preconcentrated by using microwave-assisted derivatization and IL-based DLLME in a single step. Several experimental parameters, including type and volume of extraction solvent, type and volume of disperser, microwave power and irradiation time, volume of DNPH, pH of sample solution, and ionic strength were evaluated. When the microwave power was 120 W, formaldehyde could be derivatized and extracted simultaneously only within 90 s. Under optimal experimental conditions, good linearity was observed in the range of 0.5-50 ng/mL with the correlation coefficient of 0.9965, and the limit of detection was 0.12 ng/mL. The proposed method was applied to the analysis of different beverage samples, and the recoveries of formaldehyde obtained were in the range of 84.9-95.1% with the relative standard deviations lower than 8.4%. The results showed that the proposed method was a rapid, convenient and feasible method for the determination of formaldehyde in beverage samples.     

Determination of insecticides in water using in situ halide exchange reaction-assisted ionic liquid dispersive liquid-liquid microextraction followed by high-performance liquid chromatography

A dispersive liquid-liquid microextraction (DLLME) method using in situ halide exchange reaction to form ionic liquid (IL) extraction phase was developed to determine four insecticides (i.e. methoxyfenozide, tetrachlorvinphos, thiamethoxam, and diafenthiuron) in water samples. The preconcentration procedure, followed by high-performance liquid chromatography and variable wavelength detectors (VWD), enabled the formation of the immiscible IL extraction phase; the insecticides were transferred into the IL phase simultaneously, which enhanced the efficiency and sufficiency, greatly shortening the operation time. The experimental parameters affecting the extraction efficiency including volume of extraction IL, extraction and centrifugation times, volume of the sample solution and exchanging reagent, and addition of organic solvent and salt were investigated and optimized. Under optimized conditions, the extractions yielded recoveries of the target analytes from 82 to 102%. The calibration curves were linear, and the correlation coefficient ranged from 0.9990 to 0.9999 under the concentration levels of 5-200 μg/L. The relative standard deviation (n=6) was 2.9-4.6%. The limits of detection (LODs) for the four insecticides were between 0.98 and 2.54 μg/L.     

Selective determination of inorganic cobalt in nutritional supplements by ultrasound-assisted temperature-controlled ionic liquid dispersive liquid phase microextraction and electrothermal atomic absorption spectrometry

In the present work, a simple and rapid analytical method based on application of ionic liquids (ILs) for inorganic Co(II) species (iCo) microextraction in a variety of nutrient supplements was developed. Inorganic Co was initially chelated with 1-nitroso-2-naphtol (1N2N) reagent followed by a modern technique named ultrasound-assisted temperature-controlled ionic liquid dispersive liquid phase microextraction (USA-TILDLME). The extraction was performed with 1-hexyl-3-methylimidazolium hexafluorophosphate [C₆mim][PF₆] with the aid of ultrasound to improve iCo recovery. Finally, the iCo-enriched IL phase was solubilized in methanol and directly injected into an electrothermal atomic absorption spectrometer (ETAAS). Several parameters that could influence iCo microextraction and detection were carefully studied. Since the main difficulty in these samples is caused by high concentrations of potential interfering ions, different approaches were evaluated to eliminate interferences. The limit of detection (LOD) was 5.4 ng L^?1, while the relative standard deviation (RSD) was 4.7% (at 0.5 μg L^?1 Co level and n = 10), calculated from the peak height of absorbance signals. Selective microextraction of iCo species was achieved only by controlling the pH value during the procedure. The method was thus successfully applied for determination of iCo species in nutritional supplements.     

Determination of traces of lead and cadmium using dispersive liquid-liquid microextraction followed by electrothermal atomic absorption spectrometry

Microchimica Acta - A procedure is presented for the determination of very low concentrations of lead and cadmium in water samples. Dispersive liquid-liquid microextraction with ammonium...     

Speciation of mercury in water samples by dispersive liquid-liquid microextraction combined with high performance liquid chromatography-inductively coupled plasma mass spectrometry

The dispersive liquid-liquid microextraction (DLLME) combined with high performance liquid chromatography-inductively coupled plasma mass spectrometry for the speciation of mercury in water samples was described. Firstly methylmercury (MeHg⁺) and mercury (Hg²⁺) were complexed with sodium diethyldithiocarbamate, and then the complexes were extracted into carbon tetrachloride by using DLLME. Under the optimized conditions, the enrichment factors of 138 and 350 for MeHg⁺ and Hg²⁺ were obtained from only 5.00 mL sample solution. The detection limits of the analytes (as Hg) were 0.0076 ng mL⁻¹ for MeHg⁺ and 0.0014 ng mL⁻¹ for Hg²⁺, respectively. The relative standard deviations for ten replicate measurements of 0.5 ng mL⁻¹ MeHg⁺ and Hg²⁺ were 6.9% and 4.4%, respectively. Standard reference material of seawater (GBW(E)080042) was analyzed to verify the accuracy of the method and the results were in good agreement with the certified values. Finally, the developed method was successfully applied for the speciation of mercury in three environmental water samples.     

Determination of triclosan and triclocarban in environmental water samples with ionic liquid/ionic liquid dispersive liquid-liquid microextraction prior to HPLC-ESI-MS/MS

A hydrophobic ionic liquid was finely dispersed in aqueous solution along with a hydrophilic ionic liquid. Following centrifugation, the two phases aggregate to form relatively large droplets. Based on this phenomenon, a method termed ionic liquid/ionic liquid dispersive liquid-liquid microextraction was developed. It was applied to the enrichment of triclosan (TCS) and triclocarban (TCC) from water samples prior to HPLC with electrospray tandem MS detection. The type and volume of the hydrophobic ionic liquid (the extraction solvent) and the hydrophilic ionic liquid (the disperser solvent), salt content, and extraction time were optimized. Under optimum conditions, the method gives a linear response in the concentration ranges from 0.5 to 100???g L^?1 for TCC and from 2.5 to 500???g L^?1 for TCS, respectively. The limits of detection are 0.23 and 0.35???g L^?1, and the repeatability is 5.4 and 6.4% for TCC and TCS, respectively. The method was validated with four environmental water samples, and average recoveries of spiked samples were in the range from 88% to 111%. The results indicate that the method is a promising new approach for the rapid enrichment and determination of organic pollutants.

Speciation of butyl and phenyltin compounds using dispersive liquid-liquid microextraction and gas chromatography-flame photometric detection

Dispersive liquid-liquid microextraction and gas chromatography-flame photometric detection (DLLME-GC-FPD) were performed for the speciation of butyl and phenyltin compounds in water samples after derivatization with sodium tetraethylborate (NaBEt4). Some important parameters, such as pH, amount of NaBEt4, derivatization time, kind and volume of extraction and disperser solvents, extraction time and salt effect were investigated and optimized. High enrichment factors (825-1036) and low detection limits (0.2-1 ng L(-1)) were obtained under the optimum conditions. The calibration graphs were linear in the range of 0.5-1000 ng L(-1) (as Sn) for the target analytes. The relative standard deviations (RSDs) for the extraction of 20 ng L(-1) (as Sn) of butyl and phenyltin compounds varied from 2.3 to 5.9% (n=7) and from 4.1 to 8.8% (n=7) with and without using internal standard, respectively. Seawater and river water samples were successfully analyzed using the proposed method and the relative recoveries of the studied compounds in the water samples, at spiking levels of 10.0 and 100 ng L(-1) (as Sn) were obtained to be 82.5-104.7%.     

Rapid determination of lead in water samples by dispersive liquid-liquid microextraction coupled with electrothermal atomic absorption spectrometry

The need for highly reliable methods for the determination of trace and ultratrace elements has been recognized in analytical chemistry and environmental science. A simple and powerful microextraction technique was used for the detection of the lead ultratrace amounts in water samples using the dispersive liquid-liquid microextraction (DLLME), followed by the electrothermal atomic absorption spectrometry (ET AAS). In this microextraction technique, a mixture of 0.50 mL acetone (disperser solvent), containing 35 microL carbon tetrachloride (extraction solvent) and 5 microL diethyldithiophosphoric acid (chelating agent), was rapidly injected by syringe into the 5.00 mL water sample, spiked with lead. In this process, the lead ions reacted with the chelating agent and were extracted into the fine droplets of CCl(4). After centrifugation (2 min at 5000 rpm), the fine CCl4 droplets were sedimented at the bottom of the conical test tube (25+/-1 microL). Then, 20 microL from the sedimented phase, containing the enriched analyte, was determined by ET AAS. The next step was the optimization of various experimental conditions, affecting DLLME, such as the type and the volume of the extraction solvent, the type and the volume of the disperser solvent, the extraction time, the salt effect, pH and the chelating agent amount. Moreover, the effect of the interfering ions on the analytes recovery was also investigated. Under the optimum conditions, the enrichment factor of 150 was obtained from only a 5.00 mL water sample. The calibration graph was linear in the range of 0.05-1 microg L(-1) with the detection limit of 0.02 microg L(-1). The relative standard deviation (R.S.D.) for seven replicate measurements of 0.50 microg L(-1) of lead was 2.5%. The relative lead recoveries in mineral, tap, well and sea water samples at the spiking level of 0.20 and 0.40 microg L(-1) varied from 93.5 to 105.0. The characteristics of the proposed method were compared with the cloud point extraction (CPE), the liquid-liquid extraction, the solid phase extraction (SPE), the on-line solid phase extraction (SPE) and the co-precipitation, based on bibliographic data. The main DLLME advantages combined with ET AAS were simplicity of operation, rapidity, low cost, high-enrichment factor, good repeatability, low consumption of extraction solvent, requiring a low sample volume (5.00 mL).     

Determination of cocaine adulterants in human urine by dispersive liquid-liquid microextraction and high-performance liquid chromatography

Analytical and Bioanalytical Chemistry - This study aimed to determine simultaneously five major street cocaine adulterants (caffeine, lidocaine, phenacetin, diltiazem, and hydroxyzine) in human...     

Ionic liquid based dispersive liquid-liquid microextraction of aromatic amines in water samples

In this work, a new microextraction method termed ionic liquid based dispersive liquid-liquid microextraction （IL-DLLME） was demonstrated for the extraction of 2-methylaniline, 4-chloroaniline, 1-naphthylamine and 4-aminobiphenyl in aqueous matrices. After extraction the ionic liquid （IL） phase was injected directly into the high performance liquid chromatography （HPLC） system for determination. Some parameters that might affect the extraction efficiency were optimized. Under the optimum conditions, good linear relationship, sensitivity and reproducibility were obtained. The limits of detection （LOD, S/N = 3） for the four analytes were in the range of 0.45-2.6 μg L^-1. The relative standard deviations （R.S.D., n = 6） were in the range of 6.2-9.8%. This method was applied for the analysis of the real water samples. The recoveries ranged from 93.4 to 106.4%. The main advantages of the method are high speed, high recovery, good repeatability and volatile organic solvent-free.     

分散液相微萃取技术研究的最新进展

分散液相微萃取(DLLME)作为一种新型样品前处理技术,具有操作简便、快速,富集效率高,萃取剂使用量少等优点。本文对近年来该技术在分离科学领域应用的最新进展进行了简要评述。主要讨论了以下3个方面:(1)DLLME与其他净化或萃取技术的结合;(2)萃取剂的拓展;(3)萃取装置的改进。     

Selective extraction of emerging contaminants from water samples by dispersive liquid-liquid microextraction using functionalized ionic liquids

Functionalized ionic liquids containing the tris(pentafluoroethyl)trifluorophosphate (FAP) anion were used as extraction solvents in dispersive liquid-liquid microextraction (DLLME) for the extraction of 14 emerging contaminants from water samples. The extraction efficiencies and selectivities were compared to those of an in situ IL DLLME method which uses an in situ metathesis reaction to exchange 1-butyl-3-methylimidazolium chloride (BMIM-Cl) to 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide (BMIM-NTf(2)). Compounds containing tertiary amine functionality were extracted with high selectivity and sensitivity by the 1-(6-amino-hexyl)-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (HNH(2)MPL-FAP) IL compared to other FAP-based ILs and the BMIM-NTf(2) IL. On the other hand, polar or acidic compounds without amine groups exhibited higher enrichment factors using the BMIM-NTf(2) IL. The detection limits for the studied analytes varied from 0.1 to 55.1 μg/L using the traditional IL DLLME method with the HNH(2)MPL-FAP IL as extraction solvent, and from 0.1 to 55.8 μg/L using in situ IL DLLME method with BMIM-Cl+LiNTf(2) as extraction solvent. A 93-fold decrease in the detection limit of caffeine was observed when using the HNH(2)MPL-FAP IL compared to that obtained using in situ IL DLLME method. Real water samples including tap water and creek water were analyzed with both IL DLLME methods and yielded recoveries ranging from 91% to 110%.