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.     

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.     

Ionic liquid-based homogeneous liquid-liquid microextraction for the determination of antibiotics in milk by high-performance liquid chromatography

Ionic liquid-based homogeneous liquid-liquid microextraction (IL-based HLLME) high-performance liquid chromatography was developed and applied to the extraction, separation and determination of some antibiotics in milk. The proteins and lipids were removed by adding salt and adjusting the pH value. The homogeneous extraction was applied to the improvement of recoveries for IL phase and analytes. The experimental parameters of the IL-based HLLME, including salt concentration in sample solution, pH value of sample solution, volume of [C(6)MIM][BF(4)], amount of ion-pairing agent (NH(4)PF(6)), and extraction time, were evaluated. The limits of detection for enoxacin, pefloxacin, norfloxacin, enrofloxacin, sulfamethoxazole and sulfadimethoxine were 15.8, 7.07, 5.13, 4.00, 7.79 and 8.33 μg L(-1), respectively. When the proposed method was applied to the analysis of milk samples the recoveries of the analytes ranged from 92.5 to 118.6% and relative standard deviations were lower than 7.00%.     

Ionic liquid-based liquid phase microextraction with direct injection for capillary electrophoresis

Liquid–liquid microextraction using the water immiscible ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, EMIM NtfO₂, for the concentration and cleanup of basic compounds for analysis by CE has been investigated. Using an electrolyte comprising 1 mol/L alanine and 3 mol/L acetic acid, EMIM NtfO₂ could be directly injected into the capillary after liquid phase extraction. Using the basic dye chryisoidine, sensitivity enhancements approaching 1000-fold were obtained by mixing 20 μL of EMIM NtfO₂ with 1500 μL of aqueous sample, leaving only 5 μL of the undissolved ionic liquid which was used for injection into the CE. Lower more repeatable enhancement factors of 200-fold were obtained with slightly larger initial 25 μL volumes of EMIM NtfO₂ due to the larger residual volume of ionic liquid which made handling easier. This could be extended to basic pharmaceuticals, and the extraction of clozapine and its two active metabolites, nor-clozapine and clozapine-N-oxide, was demonstrated from urine with enrichment factors greater than 100 obtained. Handling of potentially more dangerous samples, such as serum, through in-vial extraction of clozapine and its metabolites and direct injection of the ionic liquid layer was also demonstrated with enhancements in sensitivity of 80. Limits of detection from 3 to 11 μg/L and 6 to 55 μg/L were obtained from urine and serum, respectively, which are sufficiently low to be useful for the determination of these pharmaceuticals clinically for therapeutic drug monitoring and for forensic toxicology.     

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.     

Ionic liquid-based dynamic liquid-phase microextraction: application to the determination of anti-inflammatory drugs in urine samples

Dynamic liquid-phase microextraction (dLPME) using an ionic liquid as acceptor phase is proposed for the determination of six non-steroidal anti-inflammatory drugs (NSAIDs) in human urine samples for the first time. The extraction is carried out in a simple and automatic flow configuration. The chemical affinity between the extractant (1-butyl-3-methylimidazolium hexafluorophosphate) and the analytes permits a selective isolation of the drugs from the sample matrix allowing also their preconcentration. The whole analytical method has been optimized taking into account all the chemical, physical and hydrodynamic variables. The proposed method is a valuable alternative for the analysis of these drugs in urine within the concentration range 0.1-10 microg mL(-1), allowing their determination at therapeutic and toxic levels. Limits of detection were in the range from 38 ng mL(-1) (indomethacin) to 70 ng mL(-1) (naproxen). The repeatability of the proposed method expressed as RSD (n=5) varied between 2.1% (flurbiprofen) and 3.8% (tolmetin).     

Ionic liquid-based headspace single-drop microextraction coupled to gas chromatography for the determination of chlorobenzene derivatives

A novel method, based on the coupling of ionic liquid-based headspace single-drop microextraction (SDME) with gas chromatography (GC), is developed for the determination of chlorobenzene derivatives. For the SDME of five chlorobenzene derivatives, a 1.0 μL 1-octyl-3-methylimidazolium hexafluorophosphate microdrop is exposed for 20 min to the headspace of a 15 ml aqueous sample containing 20% (w/v) NaCl placed in 25 ml vial at 40 °C. Then, the extractant is directly injected into the injector block of the GC instrument. To avoid ionic liquid leaking into the chromatographic column, a small glass tube is placed in the injection block. Under optimized operation conditions, linear relation between peak areas and analyte concentrations up to 1.5 mg L^?1 has been obtained The detection limits range from 0.1 to 0.5 μg L^?1 for the various analytes. The relative standard deviations at 1.0 μg L^?1 range from 7.7 to 12.4%, and the enrichment factors from 41 to 127. The method is simple and sensitive, and does not suffer from the influence of a solvent peak. Its applicability is demonstrated by the determination of chlorobenzenes in wastewater samples.     

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.     

Ionic liquid for high temperature headspace liquid-phase microextraction of chlorinated anilines in environmental water samples

Based on the non-volatility of room temperature ionic liquids (IL), 1-butyl-3-methylimidazolium hexafluorophosphate ([C4MIM][PF6]) IL was employed as an advantageous extraction solvent for high temperature headspace liquid-phase microextraction (LPME) of chloroanilines in environmental water samples. At high temperature of 90 degrees C, 4-chloroaniline, 2-chloroaniline, 3,4-dichloroaniline, and 2,4-dichloroaniline were extracted into a 10 microl drop of [C4MIM][PF6] suspended on the needle of a high-performance liquid chromatography (HPLC) microsyringe held at the headspace of the samples. Then, the IL was injected directly into the HPLC system for determination. Parameters related to LPME were optimized, and high selectivity and low detection limits of the four chlorinated anilines were obtained because the extraction was performed at high temperature in headspace mode and the very high affinity between IL and chlorinated anilines. The proposed procedure was applied for the analysis of the real samples including tap water, river water and wastewater samples from a petrochemical plant and a printworks, and only 3,4-dichloroaniline was detected in the printworks wastewater at 88.2 microg l(-1) level. The recoveries for the four chlorinated anilines in the four samples were all in the range of 81.9-99.6% at 25 microg l(-1) spiked level.     

Development of a simple in-vial liquid-phase microextraction device for drug analysis compatible with capillary gas chromatography, capillary electrophoresis and high-performance liquid chromatography

A simple, inexpensive and disposable device for liquid-phase microextraction (LPME) is presented for use in combination with capillary gas chromatography (GC), capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC). 1-4 ml samples of human urine or plasma were filled into conventional 4-ml vials, whereafter 15-25 microl of the extraction medium (acceptor solution) was filled into a short piece of a porous hollow fiber and placed into the sample vial. The drugs of interest were extracted from the sample solutions and into the small volumes of acceptor solution based on high partition coefficients and were preconcentrated by a factor of 30-125. For LPME in combination with GC, the porous hollow fiber was filled with 15 microl n-octanol as the acceptor solution. Following 30 min of extraction, the organic acceptor solution was injected directly into the GC system. For LPME in combination with CE and HPLC, n-octanol was immobilized within the pores of the hollow fiber, while the internal volume of the fiber was filled with either 25 microl of 0.1 M HCl (for extraction of basic compounds) or 25 microl 0.02 M NaOH (for acidic compounds). Following 45 min extraction, the aqueous acceptor solution was injected directly into the CE or HPLC system. Owing to the low cost, the extraction devices were disposed after a single extraction which eliminated the possibility of carry over effects. In addition, because no expensive instrumentation was required for LPME, 10-30 samples were extracted in parallel to provide a high number of samples per unit time capacity.     

Hybrid flow analyzer for automatic hollow-fiber-assisted ionic liquid-based liquid-phase microextraction with in-line membrane regeneration

The proof-of-concept of a new methodology for in-line hollow-fiber (HF)-assisted three-phase liquid-phase microextraction (LPME) allowing for handling of the feed and acceptor aqueous solutions and of minute volumes of the organic extracting phase in a programmable flow mode is reported in this paper. The flow analyzer fosters in-line anchoring of ionic-liquid-laden extracting solution (10 % (v/v) methyltrioctyl ammonium chloride in kerosene) in the pores of a single-strand microporous polypropylene HF, and regeneration of the liquid-phase membrane itself for each individual analysis cycle in a fully automated mode. Using hexavalent chromium as a model analyte and 1,5-diphenylcarbazide as a chromogenic probe in the acceptor solution, the flow-based HF-LPME hyphenated system was harnessed to the clean-up of troublesome samples (viz., domestic wastewater and soil leachates) with concomitant enrichment of target species. Distinct extraction modes and chemistries were assessed for enhanced Cr(VI) permeability. A single sample plug was subjected to a twofold backward–forward flow extraction so as to decrease the thickness of the boundary layer at the HF shell side for improved extraction efficiency. Under the optimized physicochemical variables, a limit of detection of 4.6 μg?L^?1 Cr(VI), a dynamic linear range of up to 500 μg?L^?1 and intermediate precision better than 10 % were obtained for a sample volume of 2.8 mL buffered at pH 4 and a volume of organic extractant of 120 μL, with an enrichment factor of ca. 11 for a sample residence time in the donor compartment of merely 4.5 min. Analyte recoveries in domestic wastewaters were ≥83 % using external calibration with relative standard deviations better than 14 %, thereby demonstrating the expedient clean-up of samples with elevated content of dissolved organic carbon. The automatic HF-LPME method was validated in terms of bias against the SRM 2701 (NIST soil) preceded by the EPA alkaline digestion method 3060A. No significant differences between Cr(VI) concentration as obtained with the automatic HF-LPME system (546?±?57 mg?kg^?1) and the certified value (551.2?±?17.2 mg?kg^?1, expressed as mean ± combined uncertainty) were encountered at the 0.05 significance level.     

基于离子液体的单滴液相微萃取-高效液相色谱法测定水中杀螨隆农药残留

建立了基于1-辛基-3-甲基咪唑六氟磷酸盐离子液体的单滴液相微萃取-高效液相色谱测定水中的杀螨隆农药残留的新方法.考察了萃取剂种类、萃取剂体积、液滴大小、萃取时间、搅拌速度、温度、盐度等对萃取效率的影响.在最佳条件下,该方法的线性范围为0.05～5 mg/L,r2=0.9994,RSD为2.1%(n=6),检出限为0....     

Advances in sample preparation using membrane-based liquid-phase microextraction techniques

The article highlights some of the most important developments in membrane-based liquid-phase microextraction techniques and applications. We discuss the evolution of different configurations from the flat type of module through the hollow-fiber module to the latest membrane combination with other sorbents and coating of the hollow fiber. We also discuss the basic principles and important parameters that control the extraction process in two-phase and three-phase systems. Finally, we highlight future trends in module configuration and applications.     

Development of a two-dimensional liquid chromatography system with trapping and sample enrichment capabilities

A solid-phase microextraction (SPME) followed by a gas chromatographic-mass spectrometric (GC-MS) determination has been developed and validated for the determination of cyprodinil and fludioxonil in white wine samples. Extraction parameters such as the selection of SPME coating, the effect of the temperature, the effect of the headspace volume and the salt addition were studied and optimized, together with GC-MS analytical conditions. The divinylbenzene-Carboxen-polydimethylsiloxane (DVB-CAR-PDMS) fiber was the most appropriate for the determination of the two pesticides in wine. The quality parameters of the proposed method demonstrated a good precision (RSD about 5%), with detection limits of 0.1 and 0.2 microg/l for cyprodinil and fludioxonil, respectively. Fifteen commercial white wine samples produced in Rías Baixas area in Galicia (N.W. Spain) were analyzed with the SPME-GC-MS procedure. Some of the commercial wines (75%) presented the two pesticides in concentrations ranging from 0.9 to 28.6 microg/l. In conclusion, SPME-GC-MS has a great potential for fungicide determination in wines.     

A new interface for coupling solid phase microextraction with liquid chromatography

A modified Rheodyne 7520 microsample injector was used as a new solid phase microextraction (SPME)–liquid chromatography (LC) interface. The modification was focused on the construction of a new sample rotor, which was built by gluing two sample rotors together. The new sample rotor was further reinforced with 3 pieces of stainless steel tubing. The enlarged central flow passage in the new sample rotor was used as a desorption chamber. SPME fiber desorption occurred in static mode. But all desorption solvent in the desorption chamber was injected into LC system with the interface. The analytical performance of the interface was evaluated by SPME–LC analysis of PAHs in water. At least 90% polycyclic aromatic hydrocarbons (PAHs) were desorbed from a polyacrylonitrile (PAN)/C18 bonded fuse silica fiber in 30 s. And injection was completed in 20 s. About 10–20% total carryovers were found on the fiber and in the interface. The carryover in the interface was eliminated by flushing the desorption chamber with acetonitrile at 1 mL min⁻¹ for 2 min. The repeatability of the method was from 2% to 8%. The limit of detection (LOD) was in the mid pg mL⁻¹ range. The linear ranges were from 0.1 to 100 ng mL⁻¹. The new SPME–LC interface was reliable for coupling SPME with LC for both qualitative and quantitative analysis.     

液相微萃取-高效液相色谱法分析葡萄汁中多酚类化合物

建立了一种基于液相微萃取与高效液相色谱联用技术测定葡萄汁中鞣花酸、白藜芦醇和槲皮素的分析方法. 比较了单液滴液相微萃取和中空纤维液相微萃取两种萃取模式, 选择了单液滴液相微萃取作为3种多酚类化合物的液相微萃取模式. 考察了搅拌速度、萃取时间、料液相pH和料液相离子强度的影响. 鞣花酸、白藜芦醇和槲皮素的富集倍数分别为48.4、 79.4和155.8, 方法的线性范围为0.0050～5.0 μg/mL, 鞣花酸、白藜芦醇和槲皮素的检出限分别为0.015, 0.0020, 0.0080 μg/mL, 相对标准偏差分别为2.0%, 1.8%和1.7%. 用于实际样品葡萄汁的分析, 加标回收率在81.9%～102.3%之间.     

Application of ultrasound-assisted ionic liquid dispersive liquid-phase microextraction followed high-performance liquid chromatography for the determination of fungicides in red wine

A new method was developed for the determination of fungicides in red wine using ultrasound-assisted ionic liquid dispersive liquid–phase microextraction followed by high-performance liquid chromatography. The ionic liquid, 1-hexyl-3-methylimidazolium hexafluorophosphate (IL) was quickly disrupted by ultrasonication and dispersed in wine as fine droplets. At this stage, the analytes were extracted into the fine droplets of IL. After centrifugation, the concentration of the enriched fungicides in the sedimented phase was determined. Extraction conditions including the type of extraction solvent, the extraction solvent volume, ultrasonication time, centrifugation time and sample pH were optimized. The performance of the method was studied in terms of linearity, precision, and recovery. Quantitative recoveries (>70%) except for pyrimethanil were obtained, and method precision was also satisfactory (RSD?<?10%). Enrichment factors range from 100 to 200, and the limits of detection are at the low μg per liter level for most of the target compounds.

In-line liquid-phase microextraction for selective enrichment and direct electrophoretic analysis of acidic drugs

This work describes an efficient in-line extraction-preconcentration unit coupled to the electrophoretic capillary based on a liquid-phase microextraction (LPME) process, which can be directly assembled to the cartridge of the commercial CE equipment. The unit permits analyte extraction, preconcentration and electrophoretic separation to be automatically performed in the commercial CE equipment without the need for additional hardware or software. This new approach was usefully used for the separation and determination of nonsteroidal anti-inflammatory drugs in human urine permitting at least to analyze 30 consecutive real samples. The LODs were lower than 2 microg/L and the reproducibility, expressed as RSD, was 3.1% for the same unit and only 4.8% between different units.     

Antibiotic-assisted three-phase liquid-phase microextraction of aromatic amines from aqueous solutions combined with high-performance liquid chromatography

Three-phase liquid-phase microextraction (LLLME) combined with high-performance liquid chromatography (HPLC) equipped with a monolithic column for the analysis of some aromatic amines is described. These compounds were extracted from an aqueous sample (4.0 mL) adjusted to pH 13 with NaOH-NaCl solution (Donor Phase, P₁) into an organic phase (P₂, 150 μL of Benzyl alcohol and ethyl acetate mixture, 2:1) and then back-extracted into a microdrop of aqueous acceptor phase (P3) adjusted to pH 2 with Na₂HPO₄-H₃PO₄ buffer solution. The extraction time T1 (from P₁ to P₂) was 20 min, and T₂ (from P₂ to P₃) was 1 min. Different antibiotics as complexing agents for amines were added to the acceptor phase to improve the extraction time. Factors such as organic solvents, extraction times, addition of antibiotics to the acceptor phase, and stirring rate were optimized. The method was applied to the determination of aromatic amines in waste-water samples. Enrichment factors ranged from 189.0 to 395.5. The linearity range was from 2.5 to 1000 ng/mL, and the detection limits varied from 0.5 to 1.50 ng/mL. Relative standard deviations (%, n = 5) were found (at S/N 3) to be in the range of 1.3–8.5. All experiments were carried out at room temperature, 22 ± 0.5°C. The text was submitted by the authors in English.