Ionic liquid for single‐drop microextraction followed by high‐performance liquid chromatography‐ultraviolet detection to determine carbonyl compounds in environmental waters

A sensitive method based on ionic liquid for single‐drop liquid microextraction coupled with HPLC‐UV was developed for the determination of carbonyl compounds in environmental waters using 1‐octyl‐3‐methylimidazolium hexafluorophosphate [C₈min][PF₆] as extraction solvent and 2,4‐dinitrophenylhydrazine as derivatizing agent. The extraction parameters affecting the enrichment factors such as solvent volume, pH, extraction time and salt concentration were investigated. A homemade funnel form polytetrafluoroethylene sleeve was fixed at the tip of the syringe needle and this allowed the use of 10 μL drop of ionic liquid for direct immersion extraction. Under the optimal conditions, the remarkable enrichment factors up to 150‐fold were obtained depending on the target analytes. The method has been validated when rectilinear relationship was obtained between the concentrations of analytes and peak area in the range of 5–100 ng/mL, the correlation coefficients were from 0.995 to 0.998, and the limit of detection was in the range of 0.04–2.03 ng/mL. The method was applied to monitor the concentration of carbonyl compounds in environmental waters with spiked recovery in the range of 84.2–106.9%.     

In‐line coupled single drop liquid–liquid–liquid microextraction with capillary electrophoresis for determining fluoroquinolones in water samples

A simple in‐line single drop liquid–liquid–liquid microextraction (SD‐LLLME) coupled with CE for the determination of two fluoroquinolones was developed. The method is capable to quantify trace amount of analytes in water samples and to improve the sensitivity of CE detection. For the SD‐LLLME, a thin layer of organic phase was used to separate a drop of 0.1 M NaOH hanging at the inlet of the capillary from the aqueous donor phase. By this way, the analytes were extracted to the acceptor phase through the organic layer based on their acidic/basic dissociation equilibrium. The drop was immersed into the organic phase during 10 min for extraction and then it is directly injected into the capillary for the analysis. Parameters such as type and volume of organic solvent phase, aqueous donor, and acceptor phases and extraction time and temperature were optimized. The enrichment factor was calculated, resulting 40‐fold for enrofloxacin (ENR) and sixfold for ciprofloxacin (CIP). The linear range were 20–400 μg/L for ENR and 60–400 μg/L for CIP. The detection limits were 10.1 μg/L and 55.3 μg/L for ENR and CIP, respectively, and a good reproducibility was obtained (4.4% for ENR and 5.6% for CIP). Two real water samples were analysed applying the new method and the obtained results presented satisfactory recovery percentages (90–100.3%).     

Determination of zearalenone in maize products by vortex‐assisted ionic‐liquid‐based dispersive liquid–liquid microextraction with high‐performance liquid chromatography

A novel method has been developed for the analysis of zearalenone in maize products by vortex‐assisted ionic‐liquid‐based dispersive liquid–liquid microextraction combined with HPLC and fluorescence detection. Maize samples were extracted with methanol/water (80:20, v/v) and the extraction solution was then used as the dispersive solvent in the microextraction procedure. The analyte was rapidly transmitted to a small volume of ionic liquid and was determined by HPLC. Various parameters affecting the recovery of the mycotoxin were investigated, such as the type and volume of the extraction solvent, the type and volume of the dispersive solvent, the pH of the aqueous phase, the salt addition, and the time of vortex and centrifugation. Under the optimal experimental conditions, a good linearity of the analyte was obtained in the range of 1.0–1000.0 μg/L with the correlation coefficient of 0.9998. The limit of detection (S/N = 3) and quantification (S/N = 10) were 0.3 and 1.0 μg/kg, and the mean recoveries ranged from 83.5 to 94.9%, with a relative standard deviation less than 5.0%. The proposed method was demonstrated to be simple, cheap, quick, and highly selective and was successfully applied to the determination of zearalenone in maize products.     

A glance at achievements in the coupling of headspace and direct immersion single‐drop microextraction with chromatographic techniques

The present article offers a glance at achievements in single‐drop microextraction(SDME), with a focus on the two most commonly used modes of this technique: headspace and direct immersion. Factors affecting SDME, such as the pH and ionic strength of the sample solution, the stirring rate, and the extraction time are briefly summarized. The requirements for the acceptor phase and the influence of the sampling temperature are presented. In addition, the potential of the application of microwave and ultrasonic energy in SDME is also discussed. Examples of the application of the headspace and direct immersion modes of SDME are given in a table as additional Supporting Information.     

Ionic liquid‐based dispersive liquid–liquid microextraction followed by RP‐HPLC determination of saquinavir in rat serum: application to pharmacokinetics

An ionic liquid‐based dispersive liquid–liquid microextraction followed by RP‐HPLC determination of the most commonly prescribed protease inhibitor, saquinavir, in rat plasma was developed and validated. The effects of different ionic liquids, dispersive solvents, extractant/disperser ratio and salt concentration on sample recovery and enrichment were studied. Among the ionic liquids investigated, 1‐butyl‐3‐methylimidazolium hexafluorophosphate was found to be most effective for extraction of saquinavir from rat serum. The recovery was found to be 95% at an extractant/disperser ratio of 0.43 using 1‐butyl‐3‐methylimidazolium hexafluorophosphate and methanol as extraction and dispersive solvents. The recovery was further enhanced to 99.5% by addition of 5.0% NaCl. A threefold enhancement in detection and quantification limits was achieved, at 0.01 and 0.03 µg/mL, compared with the conventional protein precipitation method. A linear relationship was observed in the range of 0.035–10.0 µg/mL with a correlation coefficient (r²) of 0.9996. The method was validated and applied to study pharmacokinetics of saquinavir in rat serum. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of estrogens in environmental water samples using 1,3‐dipentylimidazolium hexafluorophosphate ionic liquid as extraction solvent in dispersive liquid–liquid microextraction

In this work, the potential of a symmetric dialkyl‐substituted ionic liquid (IL), 1,3‐dipenthylimidazolium hexafluorophosphate ([PPIm][PF₆]), as extraction solvent in dispersive liquid–liquid microextraction (DLLME) has been studied for the analysis of a group of three natural (estriol, 17β‐estradiol, and 17α‐estradiol) and four synthetic (17α‐ethynylestradiol, diethylstibestrol, dienestrol, and hexestrol) estrogenic compounds as well as one mycotoxin with estrogenic activity (zearalenone) in different types of water samples (Milli‐Q, mineral, and wastewater). Separation, determination, and quantification were developed by HPLC‐DAD and a fluorescence detector (FD) connected in series. Factors influencing the IL‐DLLME procedure (sample pH, amount of IL, type and volume of disperser solvent, ionic strength, and assistance of vortex agitation) were investigated and optimized by means of a step‐by‐step approach. Once the optimum extraction conditions were established (10 mL of water at pH 8, 60 mg of [PPIm][PF₆], 500 μL of ACN as disperser solvent and vortex agitation for 1 min), the calibration curves of the whole method (IL‐DLLME‐HPLC‐DAD/FD) were obtained and precision and accuracy were evaluated. It was demonstrated that the developed methodology was repeatable, accurate, and selective with limits of detection in the 0.30–0.57 μg/L and 13.8–37.1 μg/L range for FD and DAD, respectively. Relative recovery values were higher than 85% for the different types of water samples and the Student's t test demonstrated that there were not significant differences between the added and the found concentration.     

Ionic liquid‐based microwave‐assisted surfactant‐improved dispersive liquid–liquid microextraction and derivatization of aminoglycosides in milk samples

A green and simple method, ionic liquid‐based microwave‐assisted surfactant‐improved dispersive liquid–liquid microextraction and derivatization was developed for the determination of aminoglycosides in milk samples. Nonionic surfactant Triton X‐100 and ionic liquid 1‐hexyl‐3‐methylimidazolium hexafluorophosphate were used as the disperser and extraction solvent, respectively. Extraction, preconcentration, and derivatization of aminoglycosides were carried out in a single step. Several experimental parameters, including type and volume of extraction solvent, type and concentration of surfactant, microwave power and irradiation time, concentration of derivatization reagent, and pH value and volume of buffer were investigated and optimized. Under the optimum experimental conditions, the linearities for determining the analytes were in the range 0.4–10.0 ng/mL for tobramycin, 1.0–25.0 ng/mL for neomycin, and 2.0–50.0 ng/mL for gentamicin, with the correlation coefficients ranging from 0.9991 to 0.9998. The LODs for the analytes were between 0.11 and 0.50 ng/mL. The present method was applied to the analysis of different milk samples, and the recoveries of aminoglycosides obtained were in the range 96.4–105.4% with the RSDs lower than 5.5%. The results showed that the present method was a rapid, convenient, and environmentally friendly method for the determination of aminoglycosides in milk samples.     

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....     

Determination of four acidic nonsteroidal anti‐inflammatory drugs in wastewater samples by dispersive liquid–liquid microextraction based on solidification of floating organic droplet and high‐performance liquid chromatography

A simple, environmentally friendly, and sensitive dispersive liquid–liquid microextraction based on solidification of floating organic droplet for the extraction of four acidic nonsteroidal anti‐inflammatory drugs (ketoprofen, naproxen, ibuprofen, and diclofenac) from wastewater samples subsequent by high‐performance liquid chromatography analysis was developed. The influence of extraction parameters such as pH, the effect of solution ionic strength, type of extraction solvent, disperser solvent, and extraction solvent volume were studied. High enrichment factors (283–302) were obtained through the developed method. The method provides good linearity (r > 0.999) in a concentration range of 1–100 μg/L, good intra‐ and inter‐day precision (relative standard deviation < 7%) and low limits of quantification. The relative recoveries of the selected compounds were situated over 80% both in synthetic and real water samples. The developed method has been successfully applied for the analysis of the selected compounds in wastewater samples.     

Determination of musk fragrances in sewage sludge by pressurized liquid extraction coupled to automated ionic liquid‐based headspace single‐drop microextraction followed by GC‐MS/MS

A method for the quantitative determination of ten musk fragrances extensively used in personal care products from sewage sludge was developed by using a pressurized liquid extraction (PLE) followed by an automated ionic liquid‐based headspace single‐drop microextraction and gas chromatography‐tandem mass spectrometry. The influence of main factors on the efficiency of PLE was studied. For all musks, the highest recovery values were achieved using 1 g of pretreated sewage sludge, H₂O/methanol (1:1) as an extraction solvent, a temperature of 80°C, a pressure of 1500 psi, an extraction time of 5 min, 2 cycles, a 100% flush volume, a purge time of 120 s, and 1 g Florisil as in‐cell clean‐up extraction sorbent. The use and optimization of an in‐cell clean‐up sorbent was necessary to remove fatty interferents of the PLE extract that make the subsequent ionic liquid‐based headspace single‐drop microextraction difficult. Validation parameters, namely LODs and LOQs, ranged from 0.5–1.5 to 2.5–5 ng/g, respectively. Good levels of intra‐ and interday repeatabilities were obtained analyzing sewage sludge samples spiked at 10 ng/g (n = 3, RSDs < 10%). The method applicability was tested with sewage sludge from different wastewater treatment plants. The analysis revealed the presence of all the polycyclic musks studied at concentrations higher than the LOQs, ranging from 6 to 530 ng/g. However, the nitro musk concentrations were below the LOQs or, in the case of musk xylene, was not detected.     

In situ ionic‐liquid‐dispersive liquid–liquid microextraction of Sudan dyes from liquid samples

In situ ionic‐liquid‐dispersive liquid–liquid microextraction was introduced for extracting Sudan dyes from different liquid samples followed by detection using ultrafast liquid chromatography. The extraction and metathesis reaction can be performed simultaneously, the extraction time was shortened notably and higher enrichment factors can be obtained compared with traditional dispersive liquid–liquid microextraction. When the extraction was coupled with ultrafast liquid chromatography, a green, convenient, cheap, and efficient method for the determination of Sudan dyes was developed. The effects of various experimental factors, including type of extraction solvent, amount of 1‐hexyl‐3‐methylimidazolium chloride, ratio of ammonium hexafluorophosphate to 1‐hexyl‐3‐methylimidazolium chloride, pH value, salt concentration in sample solution, extraction time and centrifugation time were investigated and optimized for the extraction of four kinds of Sudan dyes. The limits of detection for Sudan I, II, III, and IV were 0.324, 0.299, 0.390, and 0.655 ng/mL, respectively. Recoveries obtained by analyzing the seven spiked samples were between 65.95 and 112.82%. The consumption of organic solvent (120 μL acetonitrile per sample) was very low, so it could be considered as a green analytical method.     

Single‐drop microextraction combined in‐line with capillary electrophoresis for the determination of nonsteroidal anti‐inflammatory drugs in urine samples

This study describes a method to determine nonsteroidal anti‐inflammatory drugs (NSAIDs) in urine samples based on the use of single‐drop microextraction (SDME) in a three‐phase design as a preconcentration technique coupled in‐line to capillary electrophoresis. Different parameters affecting the extraction efficiency of the SDME process were evaluated (e.g. type of extractant, volume of the microdroplet, and extraction time). The developed method was successfully applied to the analysis of human urine samples with LODs ranging between 1.0 and 2.5 μg/mL for all of the NSAIDs under study. This method shows RSD values ranging from 8.5 to 15.3% in interday analysis. The enrichment factors were calculated, resulting 27‐fold for ketoprofen, 14‐fold for diclofenac, 12‐fold for ibuprofen, and 44‐fold naproxen. Samples were analyzed applying the SDME–CE method and the obtained results presented satisfactory recovery values (82–115%). The overall method can be considered a promising approach for the analysis of NSAIDs in urine samples after minimal sample pretreatment.     

Double sample preconcentration by in‐line coupled large volume single drop microextraction and sweeping in capillary electrophoresis

Single drop microextraction (SDME) is a convenient and powerful preconcentration method for CE before injection. By simple combination of sample‐handling sequences without modification of the CE apparatus, a drop of an aqueous acceptor phase covered with a thin organic layer was formed at the tip of a capillary; 10 min SDME of fluorescein and 6‐carboxyfluorescein from a donor phase of pH 1 to an acceptor phase of pH 9 provided 110‐fold enrichments without stirring the donor phase. To improve the concentration effect further, SDME was coupled with an on‐line (after injection) sample preconcentration method, sweeping, in which analytes in a long sample zone are accumulated at the boundary of a pseudostationary phase penetrating into the sample zone. It is thus necessary to inject a sample of much larger volume than that of a drop in typical SDME. A Teflon sleeve over the capillary inlet allowed a large volume drop to be held stably during extraction. By in‐line coupling 10 min SDME and sweeping of a 30 nL sample using a cationic surfactant dodecyltrimethylammonium, enrichment factors of the double preconcentration were increased up to 32 000.     

Capillary electrophoresis determination of nonsteroidal anti‐inflammatory drugs in wastewater using hollow fiber liquid‐phase microextraction

The presence of pharmaceuticals in the environment due to growing worldwide consumption has become an important problem that requires analytical solutions. This paper describes a CE determination for several nonsteroidal anti‐inflammatory drugs (ibuprofen, naproxen, ketoprofen, diclofenac, ketorolac, aceclofenac and salicylic acid) in environmental waters using hollow fiber membrane liquid‐phase microextraction. The extraction was carried out using a polypropylene membrane supporting dihexyl ether and the electrophoretic separation was performed in acetate buffer (30 mM, pH 4) using ACN as the organic modifier. Detection limits between 0.25 and 0.86 ng/mL were obtained, respectively. The method could be applied to the direct determination of the seven anti‐inflammatories in wastewaters, and five of them have been determined or detected in different urban wastewaters.     

Simultaneous extraction and quantification of albendazole and triclabendazole using vortex‐assisted hollow‐fiber liquid‐phase microextraction combined with high‐performance liquid chromatography

A novel, simple, and rapid vortex‐assisted hollow‐fiber liquid‐phase microextraction method was developed for the simultaneous extraction of albendazole and triclabendazole from various matrices before their determination by high‐performance liquid chromatography with fluorescence detection. Several factors influencing the microextraction efficiency including sample pH, nature and volume of extraction solvent, ionic strength, vortex time, and sample volume were investigated and optimized. Under the optimal conditions, the limits of detection were 0.08 and 0.12 μg/L for albendazole and triclabendazole, respectively. The calibration curves were linear in the concentration ranges of 0.3–50.0 and 0.4–50.0 μg/L with the coefficients of determination of 0.9999 and 0.9995 for albendazole and triclabendazole, respectively. The interday and intraday relative standard deviations for albendazole and triclabendazole at three concentration levels (1.0, 10.0, and 30.0 μg/L) were in the range of 6.0–11.0 and 5.0–7.9%, respectively. The developed method was successfully applied to determine albendazole and triclabendazole in water, milk, honey, and urine samples.     

Syringe‐to‐syringe dispersive liquid‐phase microextraction solidified floating organic drop combined with high‐performance liquid chromatography for the separation and quantification of ochratoxin A in food samples

A new, simple, and rapid syringe‐to‐syringe dispersive liquid‐phase microextraction with solidified floating organic drop was used for the separation and preconcentration of ochratoxin A from grain and juice samples before its quantification using high‐performance liquid chromatography and fluorescence detection. Factors influencing the microextraction efficiency of ochratoxin A, such as sample solution pH, type and volume of organic extractant, salt concentration, number of injections, and volume of the sample, were studied and optimized. Under the optimum properties, the calibration graph showed linearity in the range of 65.0–700.0 ng/L (coefficient of determination = 0.9991). The limit of detection was 20.0 ng/L. The inter‐day and intra‐day relative standard deviations were in the range of 5.0–8.5%. This method was successfully applied for the quantification of ochratoxin A in grain and juice samples.     

Optimization of alcohol‐assisted dispersive liquid–liquid microextraction by experimental design for the rapid determination of fluoxetine in biological samples

A sensitive and rapid method based on alcohol‐assisted dispersive liquid–liquid microextraction followed by high‐performance liquid chromatography for the determination of fluoxetine in human plasma and urine samples was developed. The effects of six parameters on the extraction recovery were investigated and optimized utilizing Plackett–Burman design and Box–Benken design, respectively. According to the Plackett–Burman design results, the volume of disperser solvent, extraction time, and stirring speed had no effect on the recovery of fluoxetine. The optimized conditions included a mixture of 172 μL of 1‐octanol as extraction solvent and 400 μL of methanol as disperser solvent, pH of 11.3 and 0% w/v of salt in the sample solution. Replicating the experiment in optimized condition for five times, gave the average extraction recoveries equal to 90.15%. The detection limit of fluoxetine in human plasma was obtained 3 ng/mL, and the linearity was in the range of 10–1200 ng/mL. The corresponding values for human urine were 4.2 ng/mL with the linearity range from 10 to 2000 ng/mL. Relative standard deviations for intra and inter day extraction of fluoxetine were less than 7% in five measurements. The developed method was successfully applied for the determination of fluoxetine in human plasma and urine samples.     

Switchable‐hydrophilicity solvent liquid‐liquid microextraction versus dispersive liquid‐liquid microextraction prior to HPLC‐UV for the determination and isolation of piperine from Piper nigrum L

Switchable‐hydrophilicity solvent liquid‐liquid microextraction and dispersive liquid‐liquid microextraction were compared for the extraction of piperine from Piper nigrum L. prior to its analysis by using high‐performance liquid chromatography with UV detection. Under optimum conditions, limits of detection and quantitation were found as 0.2–0.6 and 0.7–2.0 μg/mg with the two methods, respectively. Calibration graphs showed good linearity with coefficients of determination (R²) higher than 0.9962 and percentage relative standard deviations lower than 6.8%. Both methods were efficiently used for the extraction of piperine from black and white pepper samples from different origins and percentage relative recoveries ranged between 90.0 and 106.0%. The results showed that switchable‐hydrophilicity solvent liquid‐liquid microextraction is a better alternative to dispersive liquid‐liquid microextraction for the routine analysis of piperine in food samples. A novel scaled‐up dispersive liquid‐liquid microextraction method was also proposed for the isolation of piperine providing a yield of 102.9 ± 4.9% and purity higher than 98.0% as revealed by NMR spectroscopy.     

Vortex‐ and CO2‐gas‐assisted liquid–liquid microextraction with salt addition for the high‐performance liquid chromatographic determination of furanic compounds in concentrated juices and dried fruits

A novel microextraction method based on vortex‐ and CO₂‐assisted liquid–liquid microextraction with salt addition for the isolation of furanic compounds (5‐hydroxymethyl‐2‐furaldehyde, 5‐methyl‐2‐furaldehyde, 2‐furaldehyde, 3‐furaldehyde, 2‐furoic and 3‐furoic acids) was developed. Purging the sample with CO₂ was applied after vortexing to enhance the phase separation and mass transfer of the analytes. The optimum extraction conditions were: extraction solvent (volume), propyl acetate (125 μL); sample pH, 2.4; vortexing time, 45 s; salt concentration, 25% w/v and purging time, 5 min. The analytes were separated using an ODS Hypersil C₁₈ column (250×4.6 mm i.d, 5 μm) under gradient flow. The proposed method showed good linearities (r² >0.999), low detection limits (0.08–1.9 μg/L) and good recoveries (80.7–122%). The validated method was successfully applied for the determination of the furanic compounds in concentrated juice (mango, date, orange, pomegranate, roselle, mangosteen and soursop) and dried fruit (prune, date and apricot paste) samples.     

Dispersion‐solidification liquid–liquid microextraction for volatile aromatic hydrocarbons determination: Comparison with liquid phase microextraction based on the solidification of a floating drop

Two microextraction techniques – liquid phase microextraction based on solidification of a floating organic drop (LPME‐SFO) and dispersive liquid–liquid microextraction combined with a solidification of a floating organic drop (DLLME‐SFO) – are explored for benzene, toluene, ethylbenzene and o‐xylene sampling and preconcentration. The investigation covers the effects of extraction solvent type, extraction and disperser solvents' volume, and the extraction time. For both techniques 1‐undecanol containing n‐heptane as internal standard was used as an extracting solvent. For DLLME‐SFO acetone was used as a disperser solvent. The calibration curves for both techniques and for all the analytes were linear up to 10 μg/mL, correlation coefficients were in the range 0.997–0.998, enrichment factors were from 87 for benzene to 290 for o‐xylene, detection limits were from 0.31 and 0.35 μg/L for benzene to 0.15 and 0.10 μg/L for o‐xylene for LPME‐SFO and DLLME‐SFO, respectively. Repeatabilities of the results were acceptable with RSDs up to 12%. Being comparable with LPME‐SFO in the analytical characteristics, DLLME‐SFO is superior to LPME‐SFO in the extraction time. A possibility to apply the proposed techniques for volatile aromatic hydrocarbons determination in tap water and snow was demonstrated.